&EPA
United States
Environmental Protection
Agency
Development Document for Proposed
Effluent Guidelines and Standards
for the Construction and Development
Category
June 2002
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Development Document for Proposed Effluent Guidelines
and Standards for the Construction and Development
Category
June 2002
United States Environmental Protection Agency
Office of Water (4303T)
1200 Pennsylvania Avenue, NW
Washington, DC 20460
www.epa.gov/waterscience/guide/
[EPA-821-R-02-007]
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Acknowledgments and Disclaimer
The Construction and Development Effluent Guidelines proposed rule and support documents
were prepared by the C&D Project Team: Eric Strassler, Project Manager; Jesse .Pritts, P.E.,
Engineer; George Denning, Economist; Karen Maher, Environmental Assessor; and Michael G.
Lee, Attorney. Technical support for this Development Document was provided by Tetra Tech,
Inc.
Neither the United States government nor any of its employees, contractors, subcontractors or
other employees makes any warranty, expressed or implied, or assumes any legal liability or
responsibility for any third party's use of, or the results of such use of, any information,
apparatus, product or process discussed in this report, or represents that its use by such a third
party would not infringe on privately owned rights. Mention of trade names or commercial
products does not constitute-endorsement by EPA or recommendation for use.
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Development Document for Construction and Development Proposed Effluent Guidelines
Contents
SECTION 1: SUMMARY AND SCOPE
1.1 Introduction 1-1
1.2 Summary and Scope of Proposal 1-1
SECTION 2: BACKGROUND
2.1 Legal Authority _ 2-1
2.2 Clean Water Act , '..'..' 2-1
2.2.1 Best Practicable Control Technology Currently Available 2-2
2.2.2 Best Conventional Pollutant Control Technology 2-3
2.2.3 Best Available Technology Economically Achievable 2-3
2.2.4 New Source Performance Standards 2-3
2.2.5 Pretreatment Standards for Existing Sources and Pretreatment Standards for New
Sources 2-4
2.2.6 Effluent Guidelines Schedule 2-4
2.2.7 . NPDES Phase I and n Storm Water Rules 2-5
2.3 Pollution Prevention Act of 1990 2-5
2.4 State Regulations ...: 2-6
2.5 References . 2-6
SECTION 3: DATA COLLECTION
3.1 Introduction . ; 3-1
3.2 Literature Search 3-1
3.3 Compilation of State and Municipal Existing Control Strategies, Criteria,
and Standards 3-1
3.4 Other Data Sources 3-5
3.4.1 Phase II Storm Water Rule Economic Analysis ".. 3-5
3.4.2 USDA National Resource Inventory .. 3-5
3.4.3 National Storm Water BMP Database . .'. 3-5
3.4.4 BMP Design Manuals and Guidance Documents Developed by Governmental and
Other Organizations 3-6
3.5 References ,..-.. 3-6
SECTION 4: INDUSTRY PROFILE
4.1 Introduction 4-1
4.2 Industry Description 4,4
4.2.1 Industry Definition and Classification of Subsectors by NAIC and SIC Codes 4-1
4.2.2 Residential Building Construction Group 4-6
4.2.3 Nonresidential Building Construction Group .'.. , 4-13
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4.2.4 Heavy Construction Subsector 4-21
4.3 Industry Practices and Trends 4-23
4.3.1 Overview of Construction Land-disturbing Activities 4-23
4.3.2 Construction Site Size Categories and Estimates of Amount of Disturbed Land .... 4-26
4.3.2.1 National Estimates of Disturbed Acreage 4-26
4.3.2.2 Distribution of Acreage by Project Type • • 4-28
4.3.2.3 Distribution of Developed Acreage by Project Size and Geography 4-34
4.4 References 4-39
SECTION 5: TECHNOLOGY ASSESSMENT
5.1 Construction Erosion and Sediment Controls 5-1
5.1.1 Introduction .5-1
5.1.2 Procedure for Technology Assessment • 5-2
5.1.2.1 Identification of Performance Goals 5-2
5.1-.2.2 Goals, Environmental Impact Areas, and Assessment Scales 5-3
5.1.2.3 Qualitative Versus Quantitative Assessment 5-5
5.1.3 Review of Historical Approaches to Erosion and Sediment Control 5-5
5.1.4 Goals, Control Strategies, Criteria, and Standards 5-8
5.1.4.1 Goals, Control Strategies, Criteria, And Standards: How They Relate 5-8
5.1.4.2 Levels of Performance or "How Well Do The Strategies Work?" 5-10
5.1.4.3 Strategies, Criteria, Standards, And Enforcement , 5-10
5.1.5 Control Techniques, BMP Systems 5-14
5.1.5.1 Erosion Control and Prevention 5-14
5.1.5.1.1 Planning, Staging, Scheduling • 5-14
5.1.5.1.2 Vegetative Stabilization -. 5-17
5.1.5.1.2.1 Grass-lined Channels 5-21
5.1.5.1.2.2 Seeding .' ...5-24
5.1.5.1.2.3 Sodding 5-27
5.1.5.1.2.4 Mulching 5-29
5.1.5.1.2.5 Geotextiles 5-33
5.1.5.1.2.6 Vegetated Buffer Strips .. 5-35
5.1.5.1.2.7 Erosion Control Matting 5-37
5.1.5.1.2.8 Topsoiling 5-40
5.1.5.2 Water Handling Practices ..: 5-42
5.1.5.2.1 Earth Dike 5-42
5.1.5.2.2 Temporary Swale .. 5-44
5.1.5.2.3 Temporary Storm Drain Diversion 5-51
5.1.5.2.4 Pipe Slope Drain 5-53
5.1.5.2.5 Stone CheckDam 5-57
5.1.5.2.6 Lined Waterways 5-59
5.1.5.3 Sediment Trapping Devices 5-63
5.1.5.3.1 SiltFence :. . 5-64
5.1.5.3.2 Super Silt Fence 5-71
5.1.5.3.3 Straw Bale Dike 5-73
5.1.5.3.4 Sediment Trap 5-76
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5.1.5.3.5 Sediment Basin , 5-81
5.1.5.4 Other Control Practices 5-88
5.1.5.4.1 Stone Outlet Structure 5-88
5.1.5.4.2 Rock Outlet Protection 5-90
5.1.5.4.3 Sump Pit -. '. : 5-93
5.1.5.4.4 Sediment Tank 5-95
5.1.5.4.5 Stabilized Construction Entrance 5-96
5.1.5.4.6 Land Grading -....' 5-98
5.1.5.4.7 Temporary Access Waterway Crossing 5-100
.5.1.5.4.8 Dust Control 5-103
5.1.5.4.9 Storm Drain Inlet Protection . 5-106
5.1.5.4.10 Polyacrylamide (PAM) 5-108
5.1.6 Summary • • ... 5-112
5.2 References ....,.: 5-124
SECTION 6: REGULATORY DEVELOPMENT AND RATIONALE
6.1 Identification of Industry Impacts , 6-1
6.1.1 Pollutant Indicators 6-1
6.1.2 Physical/habitat Indicators 6-4
6.2 Development of Regulatdry Options . .. . 6-5
6.3 Regulatory Options Developed for the Proposed Rule 6-7
6.3.1 Option 1 Inspection and Certification^ , 6-7
6.3.2 Option 2 Codify EPA CGP Requirements with Site Inspection and Certification
Provisions 6-9
6.3.3 Option 3 No Regulation .' 6-15
6.4 References • 6-15
SECTION 7: APPROACH TO ESTIMATING COSTS
7.1 Overview 7-1
7.2 Methods for Estimating Erosion and Sediment Control Costs .. 7-1
7:2.1 Overview .. 7-1
7.2.2 Erosion and Sediment Control Costs 7-4
7.3 Methods for Estimating Administrative Costs 7-13
7.3.1 Overview •• 7-13
7.3.2 Administrative Costs to Permittees - 7-13
7.3.3 Administrative Costs for General Permit Revisions 7-14
7.4 References > • • • • • 7-15
Appendices
A. State Regulations on the Control of Construction Storm Water A-l
B. Supporting Cost Data .,. B-l
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Tables
Table 3-1. State or Regional Planning Authority Requirements for Water Quality Protection ... 3-3
Table 3-2. Municipal or Regional Planning Authority Requirements : . 3-4
Table 4-1. 1997 NAICS Subsectors, Industry Groups, and Industries Performing Construction
Activities That Might Disturb Land 4-3
Table 4-2. ,1987 SIC Industry Groups Performing Construction Activities
That May Disturb Land 4-5
Table 4-3. Annual Housing Construction Starts by Type and Region 4-7
Table 4-4. Residential Construction Industry Profile for 1997 4-9
Table 4-5. Busiest Markets for Single-Family Housing Permits for 1999 .. 4-10
Table 4-6. Busiest Markets for Multifamily Housing Permits for 1999 4-10
Table 4-7. Changes in Housing Starts by Region (1989 and 1999) 4-12
Table 4-8. Value of Construction Work for Manufacturing and Industrial Building Construction
Establishments With Payroll by Type of Construction '. ... 4-15
Table 4-9. Value of Manufacturing and Industrial Building Construction Work for
Establishments With Payroll by Location of Construction Work, 1997 4-16
Table 4-10. Value of Construction Work for Commercial and .Institutional Building Construction
Establishments With Payroll by Type of Construction, 1997 4-18
Table 4-1,1. Value of Commercial and Institutional Building Construction Work for
Establishments With Payroll by Location of Construction Work, 1997 4-20
Table 4-12. Overview of Heavy Construction Industry, 1992 and 1997 4-22
Table 4-13. Acres Converted from Undeveloped to Developed State, 1992-1997 4-27
Table 4-14. New Single-Family and Multifamily Housing Units Authorized, 1995-1997 4-28
Table 4-15. Average and Median Lot Size for New Single-Family
Housing Units Sold, 1995-1997 4-29
Table 4-16. Average Building Square Footage 4-31
Table 4-17. Typical Building Sizes and Size Ranges by Type of Building , 4-32
Table 4-18. National Estimates of Land Area Developed Per Year, Based on Building
Permit Data , 4.33
Table 4-19. National Estimates of Land Area Disturbed Based on National Resources Inventory
Totals .,. 4-34
Table 4-20. Distribution of 14 Community Survey Permits by Site Size 4-36
Table 4-21. Distribution of National Construction by Site Size and Development Type 4-38
Table 5-1. Description of Levels of Performance of Three Control Strategies 5-10
Table 5-2. Descriptions of Levels of Difficulty in Enforcement 5-11
Table 5-3. Scheduling Considerations for Construction Activities Enforcement 5-16
Table 5-4. Conditions Where Vegetative Streambank Stabilization Is Acceptable 5-20
Table 5-5. Maximum Permissible Velocities for Individual Site Conditions
for Grass Swales 5-22
Table 5-6. Typical Mulching Materials and Application Rates 5-31
Table 5-7. Measured Reductions in Soil Loss for Different Mulch Treatments 5-32
Table 5-8. Cubic Yards of Topsoil Required for Application to Various Depths 5-41
Table 5-9. Grassed Swale Pollutant Removal Efficiency Data 5-49
Table 5-10. Average Annual Operation and Maintenance Costs for a Grass Swale 5-5:1
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Development Document for Construction and Development Proposed Effluent Guidelines
Table 5-11. Recommended Pipe/Tubing Sizes for Slope Drains 5-54
Table 5-12. Slope Drain Characteristics 5-55
Table 5-13. Maximum Slope Lengths for Silt Fences 5-65
Table 5-14. Typical Requirements for Silt Fence Fabric 5-68
• Table 5-15. Slope Lengths for Super Silt Fences 5-71
Table 5-16. Minimum Requirements for Super Silt Fence Geotextile Class F Fabric 5-72
Table 5-17, Maximum Land Slope and Distances Above a Straw Bale Dam 5-74
Table 5-18. Weir Length for Sediment Traps ' 5-78
Table 5-19. Range of Measured.Long-Term Pollutant Removal for Sediment Detention Basins . 5-79
Table 5-20. Common Concerns Associated with Sediment Traps ,.. 5-80
Table 5-21. Common Concerns Associated with Sediment Basins 5-86
Table 5-22. Riprap.Sizes and Thicknesses (SHA Specifications) ...... 5-91
Table 5-23. Application Rates for Spray-On Adhesives 5^105
Table 5-24. Turbidity Reduction Values from PAM .'.. ..,. 5-110
Table 5-25. Summary of Information on Erosion Control and Prevention
BMPs (Sub-section 5.1.5.1) 5-112
Table 5-26. Summary of Information on Erosion Control and Prevention
BMPs (Sub-section 5.1.5.2) • 5-116
Table 5-27. Summary of Information on Erosion Control and Prevention
BMPs (Sub-section 5.1.5.3) 5-119
Table 5-28. Summary of Information on Erosion Control and Prevention
BMPs (Sub-section 5.1.5.4) .., 5-122
Table 7-1. Total Costs of Proposed Rule Options 7-1
Table 7-2. Regional compliance Cost Adjustment Factors .7-4
Table 7-3. Construction Site ESC BMP Descriptions and Site Thresholds 7-5
Table 7-4, Components of Existing State Erosion and Sediment Control Requirements 7-7
Table 7-5. State Acreage Equivalent to Proposed Option 2 . 7-9
Table 7-6. Construction ESC BMP Design and Operation and Maintenance Costs as a
Percentage of Capital Costs — 7-10
Table 7-7. . Evaluated construction Site BMPs that Augment the Suite of
Baseline BMPs 7-11
Table 7-8. BMP Quantity. Adjustment Factors for Baseline and Proposed Options . .'. .7-12
Table 7-9. National Cost Estimates for Proposed Rule Options 7-13
Table 7-10. One-Time Hours and Costs to Incorporate Erosion and Sediment Control
Effluent Guidelines Requirements into General Permits 7-14
Figures
Figure 4-1. Annual Housing Starts 4-8
Figure 4-2. Bureau of Census Housing Regions :..,.... ..4-11
Figure 4-3. Annual Housing Starts by Region 4-13
Figure 4-4. Value of Heavy construction work by region, 1997 :....... . 4-23
Figure 5-1. Flow Diagram Showing Relationship Among Goals, Strategies, Criteria,
and Standards 5-9
Figure 7-1. EPA Ecoregions , 7-3
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Development Document for Construction and Development Proposed Effluent Guidelines
SECTION 1: OVERVIEW
1.1 INTRODUCTION
This document presents technical information to support the Agency's analyses and complements
"Economic Analysis of Proposed Effluent Guidelines and Standards for the Construction and
Development Category," EPA-821-R-02-008, and "Environmental Assessment for Proposed
Effluent Guidelines and Standards for the Construction and Development Category," EPA 821-
R-02-009.
A summary of the information contained in the chapters of this document is as follows:
• Chapter 2 presents background information on the legal authority for effluent limitation
guidelines and the existing EPA storm water program.
• Chapter 3 presents a summary of the data collection activities conducted to support the
proposal.
• Chapter 4 summarizes the characteristics of the construction and development industry,
, including major indicators of industry size and annual construction activity.
>
• Chapter 5 presents information and data on erosion and sediment control (ESC) best
management practices (BMPs) used by this industry, including applicability, costs, and
efficiencies. '
• Chapter 6 presents a description of the regulatory options considered by EPA for
developing the proposal, as well as a walk-through of the provisions of each proposed
option.
• Chapter 7 presents the methodology used by the Agency to estimate the costs of the
proposed options.
1.2 SUMMARY AND SCOPE OF PROPOSAL
The proposed rule contains three options for controlling storm water discharges from
construction sites.
• Option 1 would establish inspection and certification provisions to ensure proper
implementation of controls. This option would apply to all construction sites disturbing
one or more acres of land required to obtain a permit under the existing National
Pollutant Discharge Elimination System (NPDES) storm water regulations. This option
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would amend the NPDES regulations at 40 CFR Part 122, but would not create effluent
limitation guidelines.
• Option 2 would add minimum requirements for preparation of a Storm Water Pollution
Prevention Plan (SWPPP) as well as minimum requirements for sizing sediment basins,
installing erosion and sediment controls, providing temporary stabilization to exposed
soils, and conducting regular inspections. Option 2 would apply to all sites that disturb
five or more acres of land, consistent with the permitting requirements of the Phase I
NPDES storm water regulations. This option would create a new effluent guidelines
category at 40 CFR Part 450 and would also modify 40 CFR Part 122.
• Option 3 would not establish any new requirements.
EPA estimated that Option 1 would cost approximately $130 million annually, while preventing
the annual discharge of approximately 5.25 million tons of Total Suspended Solids (TSS) and
associated turbidity to surface waters. The estimated annual monetized benefits of this option are
$10.4 million. Option 2 is estimated to cost approximately $505 million annually, while
preventing the discharge of approximately 11.1 million tons of TSS and associated turbidity to
surface waters annually. The estimated annual monetized benefits of Option 2 are $22.0 million.
Option 3 is not expected to have any costs or benefits.
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Development Document for Construction and Development Proposed Effluent Guidelines
SECTION 2: BACKGROUND
2.1 LEGAL AUTHORITY
The Environmental Protection Agency (EPA) is proposing Effluent Limitation Guidelines for
discharges associated with construction and development activities under the authority of
Sections 301, 304, 306, 308, 402, and 501 of the Clean Water Act (CWA) (the Federal Water
Pollution Control Act), 33 United States Code (U.S.C.) 1311, 1314, 1316, 1318, 1342, and 1361.
This section describes EPA's legal authority for issuing the regulation, existing state regulations,
and other federal regulations associated with construction and development activities.
2.2 CLEAN WATER ACT
Congress adopted the-Clean Water Act (CWA) to "restore and maintain the chemical, physical,
and biological integrity of the nation's waters" (Section 101 (a), 33 U.S.C. 1251(a)). To achieve
this goal, the CWA prohibits the discharge of pollutants into navigable waters except in
compliance with the statute. CWA sec. 402 requires "point source" discharges to obtain a permit
.under the National Pollutant Discharge Elimination System (NPDES). These permits are issued
by EPA regional offices or authorized State agencies.
Following enactment of the Federal Water Pollution Control Amendments of 1972 (Pub.L. 92-
500, October 18, 1972), EPA and the States issued NPDES permits to thousands of dischargers,
both industrial (e.g. manufacturing, energy and mining facilities) and municipal (sewage.
treatment plants). As required under Title HI of the Act, EPA promulgated effluent limitation
guidelines and standards for many industrial categories, and these requirements are incorporated
into the permits.
The Water Quality Act of 1987 (Pub.L. 100-4, February 4, 1987) amended the CWA. The
NPDES program was expanded by defining municipal and industrial storm water discharges as
point sources. Industrial storm water dischargers, municipal separate storm sewer systems and
other storm water dischargers designated by EPA must obtain NPDES permits pursuant to
Section 402(p) (33 U.S.C. 1342(p)).
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2.2.1
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
AVAILABLE
In guidelines for a point source category, EPA may define BPT effluent limits for conventional,
toxic,1 and non-conventional pollutants. In specifying BPT, EPA looks at a number of factors.
EPA first considers the cost of achieving effluent reductions in relation to the effluent reduction .
benefits. The Agency also considers the age of the equipment and facilities, the processes
employed and any required process changes, engineering aspects of the control technologies,
non-water quality environmental impacts (including energy requirements), and such other factors
as the Agency deems appropriate (CWA sec. 304(b)(l)(B)). Traditionally, EPA establishes BPT
effluent limitations based on the average of the best performance of facilities within the category
of various ages, sizes, processes or other common characteristics. Where existing performance is
uniformly inadequate, EPA may require higher levels of control than currently in place in a
category if the Agency determines that the technology can be practically applied. (US Senate,
1973, p. 1468).
In addition, the Act requires a cost-reasonableness assessment for BPT limitations, hi
determining the BPT limits, EPA considers the total cost of treatment technologies in relation to
the effluent reduction benefits achieved. This inquiry does not limit EPA's broad discretion to
adopt BPT limitations that are achievable with available technology unless the required
additional reductions are "wholly out of proportion to the costs of achieving such marginal level
of reduction." (US Senate, 1973, p. 170) Moreover, the inquiry does not require the Agency to
quantify benefits in monetary terms. See, for example, American Iron and Steel Institute v. EPA,
526 F. 2d 1027 (3rd Cir., 1975).
In balancing costs against the benefits of effluent reduction, EPA considers the volume and
nature of expected discharges after application of BPT, the general environmental effects of
pollutants, and the cost and economic impacts of the required level of pollution control, hi past
effluent limitation guidelines and standards, BPT cost-reasonableness removal figures have
ranged from $0.21 to $33.71 per pound removed in year 2000 dollars, hi developing guidelines,
the Act does not require consideration of water quality problems attributable to particular point
sources, or water quality improvements in particular bodies of water. Accordingly, EPA has not
considered these factors in developing the limitations being proposed today. See Weyerhaeuser
Company v. Costle, 590 F. 2d 1011 (B.C. Cir. 1978).
1 In the initial stages of EPA CWA regulation, EPA efforts emphasized the achievement of BPT limitations for
control of the "classical" pollutants (e.g., TSS, pH, BOD5). However, nothing on the face of the statute explicitly
restricted BPT limitation to such pollutants. Following passage of the Clean Water Act of 1977 (Pub.L. 95-217,
December 27,1977) with its requirement for point sources to achieve best available technology limitations to control
discharges of toxic pollutants, EPA shifted its focus to developing BAT limitations for the listed priority toxic
pollutants.
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2.2.2
BEST CONVENTIONAL POLLUTANT CONTROL TECHNOLOGY
The 1977 amendments to the CWA required EPA to identify effluent reduction levels for
conventional pollutants associated with BCT technology for discharges from existing point
sources. BCT is not an additional limitation, but replaces Best Available Technology (BAT) for
control of conventional pollutants. In addition to other factors specified in sec. 304(b)(4)(B), the
CWA requires that EPA establish BCT limitations after consideration of a two- part "cost-
reasonableness" test. EPA explained its methodology for the development of BCT limitations in
July 1986 (51FR 24974).
Section 304(a)(4) designates the following as conventional pollutants: biochemical oxygen
demand (BOD5), total suspended solids (TSS), fecal coliform, pH, and any additional pollutants
defined by the Administrator as conventional. The Administrator designated oil and grease as an
additional conventional pollutant on July 30, 1979 (44 FR 44501). A primary pollutant of
concern at construction sites, sediment, is measured as TSS.
2.2.3
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
In general, BAT effluent guidelines (CWA sec. 304(b)(2)) represent the best existing
economically achievable performance of direct discharging plants in the subcategory or category.
The factors considered in assessing BAT include the cost of achieving BAT effluent reductions,
the age of equipment and facilities involved, the processes employed, engineering aspects of the
control technology, potential process changes, non-water quality environmental impacts
(including energy requirements), and such factors asjhe Administrator deems appropriate. The
Agency retains considerable discretion in assigning the weight to be accorded to these factors.
An additional statutory factor considered in setting BAT is "economic achievability." Generally,
EPA determines the economic achievability on the basis of the total cost to the subcategory and
the overall effect of the rule on the industry's financial health. The Agency may base BAT
limitations upon effluent reductions attainable through changes in a facility's processes and
operations. As with BPT, where existing performance is uniformly inadequate, EPA may base
BAT upon technology transferred from a different subcategory or from another category. In
addition, the Agency may base BAT upon manufacturing process changes or internal controls,
even when these technologies are not common industry practice.
2.2.4
NEW SOURCE PERFORMANCE STANDARDS
New Source Performance Standards (NSPS) reflect effluent reductions that are achievable based
on the best available demonstrated control technology. New facilities have the opportunity to
install the best and most efficient production processes and wastewater treatment technologies.
As a result, NSPS should represent the greatest degree of effluent reduction attainable through
the application of the best available demonstrated control technology for all pollutants (i.e.,
conventional, non-conventional, and priority pollutants). In establishing NSPS, CWA sec. 306
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Development Document for Construction and Development Proposed Effluent Guidelines
directs EPA to take into consideration the cost of achieving the effluent reduction and any non-
water quality environmental impacts and energy requirements.
2.2.5
PRETREATMENT STANDARDS FOR EXISTING SOURCES AND
PRETREATMENT STANDARDS FOR NEW SOURCES
The CWA also defines standards for indirect discharges, i.e. discharges into publicly owned
treatment works (POTWs). These are Pretreatment Standards for Existing Sources (PSES) and
Pretreatment Standards for New Sources (PSNS) under sec. 307(b). Because EPA has identified
no deliberate discharges directly to POTWs, EPA is not proposing PSES or PSNS for the
Construction and Development Category. The information reviewed by the Agency indicates
that the Vast majority of construction sites discharge either directly to waters of the U.S. or
through MS4s. In some urban areas, construction sites discharge to combined sewer systems
(i.e., sewers carrying both storm water and domestic sewage through a single pipe) which lead to
POTWs. Sediment is susceptible to treatment in POTWs, using technologies commonly
employed such as primary clarification, and EPA has no evidence of interference, pollutant pass-
through or sludge contamination.
2.2.6
EFFLUENT GUIDELINES SCHEDULE
Clean Water Act section 304(m) requires EPA to publish a plan every two years that consists of
three elements. First, under sec. 304(m)(l)(A), EPA is required to establish a schedule for the
annual review and revision of existing effluent guidelines in accordance with sec. 304(b).
Section 304(b) applies to ELGs for direct dischargers and requires EPA to revise such regulations
as appropriate. Second, under sec. 304(m)(l)(B), EPA must identify categories of sources
discharging toxic or nonconventional pollutants for which EPA has not published BAT ELGs
under sec. 304(b)(2) or new source performance standards under sec. 306. Finally, under sec.
304(m)(l)(C), EPA must establish a schedule for the promulgation of BAT and NSPS for the
categories identified under subparagraph (B) not later than three years after being identified in the
304(m) plan. Section 304(m) does not apply to pretreatment standards for indirect dischargers,
which EPA promulgates pursuant to sec. 307(b) and 307(c) of the Act.
On October 30, 1989, Natural Resources Defense Council, Inc. (NRDC), and Public Citizen,
Inc., filed an action against EPA in which they alleged, among other things, that EPA had failed
to comply with sec. 304(m). Plaintiffs and EPA agreed to a settlement of that action in a consent
decree entered on January 3,1, 1992. (Natural Resources Defense Council et al v. Whitman,
D.D.C. Civil Action No. 89-2980). The consent decree, which has been modified several times,
established a schedule by which EPA is to propose and take final action for eleven point source
categories identified by name in the decree and for eight other point source categories identified
only as new or revised rules, numbered 5 through 12. EPA selected the Construction and
Development category as the subject for New or Revised Rule #10. The decree, as modified,
calls for the Administrator to sign a proposed ELG for the C&D category no later than May 15,
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2002, and to take final action on that proposal no later than March 31, 2004. A settlement
agreement between the parties, signed on June 28, 2000, requires that EPA develop regulatory
options applicable to discharges from construction, development and redevelopment, covering
site sizes included in the Phase I and Phase IINPDES storm water rules (i.e. one acre or greater).
EPA is required to develop options including numeric effluent limitations for sedimentation and
turbidity; control of construction site pollutants other than sedimentation and turbidity (e.g.
discarded building materials, concrete truck washout, trash); BMPs for controlling post-
construction runoff; BMPs for construction sites; and requirements to design storm water
controls to maintain pre-development runoff conditions where practicable. The settlement also
requires EPA to issue guidance to MS4s and other permittees on maintenance of post-
construction BMPs identified in the proposed ELGs. Further discussion of approaches not
pursued by EPA at this time may be found in the docket for today's proposal.
2.2.7
NPDES PHASE I AND II STORM WATER RULES
The National Pollutant Discharge Elimination System (NPDES) is a permit system established
under the GWA to enforce effluent limitation. Operators of construction activities, including
clearing, grading and excavation are required to apply for permit coverage under the NPDES
Phase I and II storm water rules. Under the Phase I rule (promulgated in 1990), construction sites
of 5 or more acres must be covered by either a general or an individual permit. General permits
covering the Phase I sites have been issued by EPA regional offices and state water quality
agencies. Permittees are required to develop storm water pollution prevention plans that include
descriptions of BMPs employed, although actual BMP selection and design are at the discretion
of permittees (in conformance with applicable state or local requirements).
Construction sites between 1 and 5 acres in size are subject to the NPDES Phase n storm water
rule (promulgated in 1999). The construction activities covered under Phase n are termed small
construction activities and exclude routine maintenance that is performed to maintain the original
line and grade, hydraulic capacity, or original purpose of the facility. Under the Phase II program,
NPDES permit requirements for construction activities are similar to the Phase I requirements
because they will be covered under similar general permits.
2.3 POLLUTION PREVENTION ACT OF 1990
The Pollution Prevention Act of 1990. (PPA) (42 U.S.C. 13101 et seq., Pub. L. 101-508,
November 5, 1990) makes pollution prevention the national policy of the United States. The
PPA identifies an environmental management hierarchy in which pollution "should be prevented
or reduced whenever feasible; pollution that cannot be prevented should be recycled in an
environmentally safe manner, whenever feasible; pollution that cannot be prevented or recycled
should be treated in an environmentally safe manner whenever feasible; and disposal or release
into the environment should be employed only as a last resort..." (42 U.S.C. 13103). In short,
preventing pollution before it is created is preferable to trying to manage, treat or dispose of it
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after it is created. According to the PPA, source reduction reduces the generation and release of
hazardous substances, pollutants, wastes, contaminants or residuals at the source, usually within
a process. The term source reduction "...includes equipment or technology modifications,
process or procedure modifications, reformulation or redesign of products, substitution of raw
materials, and improvements in housekeeping, maintenance, training, or inventory control. The
term 'source reduction' does not include any practice which alters the physical, chemical, or
biological characteristics or the volume of a hazardous substance, pollutant, or contaminant
through a process or activity which itself is not integral to or necessary for the production of a
product or the providing of a service." In effect, source reduction means reducing the amount of
a pollutant that enters a waste stream or that is otherwise released into the environment prior to
out-of-process recycling, treatment, or disposal.
Although the PPA does not explicitly address storm water discharges or discharges from
construction sites, the principles of the PPA are implicit in many of the practices used to reduce
pollutant discharges from construction sites. These include controls that minimize the potential
for erosion such as stabilization of disturbed areas as soon as practicable. These controls are
described in section 5 of the Development Document.
2.4 STATE REGULATIONS
States and municipalities have been regulating discharges of runoff from construction and land
development industry to varying degrees for some time. A compilation of state and selected
municipal regulatory approaches was prepared to help establish the baseline for national and
regional levels of control. Data were collected by reviewing state and municipal web sites,
summary references, state and municipal regulations and storm water guidance manuals. All
states (and the selected municipalities) were contacted to confirm the data collected and to fill in
data gaps, however, only 87 percent of the state agencies and a much smaller percentage of
municipalities responded. The state and municipal regulatory data are summarized hi Section 3.3
and the complete data sheets are included in Appendix A.
2.5 REFERENCES
US Senate, 1973. A Legislative History of the Federal Water Pollution Control Act Amendments
of 1972. U.S. Senate Committee of Public Works, Serial No. 93-1, January 1973.
Washington, DC.
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SECTION 3: DATA COLLECTION
3.1 INTRODUCTION
EPA gathered and evaluated technical and economic data from various sources in the course of
developing the effluent limitation guidelines and standards for the construction and development
industry. "EPA used existing data sources to profile the industry with respect to general industry
description, industry trends, environmental impacts, and erosion and sediment control best
management practices (BMPs) and cost. This chapter details the data sources used in the
development of this proposal.
3.2 LITERATURE SEARCH
A literature search was performed to obtain information on various BMPs that pertain to the
construction and land development industry. Journal articles and professional conference
proceedings were used to summarize the most recent BMP effectiveness data, design and
installation criteria, applicability, advantages, limitations, and cost.
3.3 COMPILATION OF STATE AND MUNICIPAL EXISTING CONTROL
STRATEGIES, CRITERIA, AND STANDARDS
A compilation of State and municipal regulations were prepared to determine national and
regional approaches towards controlling construction site storm water. The data were collected
by reviewing State and municipal web sites, summary references, and State and municipal
regulations and storm water guidance manuals. States and municipalities were contacted to
confirm the data collected and to fill in data not available by these methods. Not all State and
municipal contacts responded or were able to provide the missing information sought. While 87
percent of the State agencies provided confirmation of the regulatory data collected for this study,
a much smaller percentage of municipalities responded.
A summary of criteria and standards that are implemented by States and municipalities as of
August 2000 are presented in Tables 3-1 and 3-2, respectively. State requirements are generally
equal to or less stringent than municipalities that are covered under the federal Clean Water Act
NPDES Storm Water Program because State requirements apply to all development within their
boundaries including single site development and low to high density developments. NPDES
Storm Water Program designated municipalities generally have a population of 100,000 or more
and can collect and fund the resources necessary to design, implement, and monitor separate and
potentially more stringent storm water management programs. Table 3-1 contains responses
from 47 of the 54 State controlling agencies. The total is greater than 50 because Florida has 5
intrastate regional authorities. Some State data were uncertain and repeated contacts to the •
responsible State agencies to confirm the data were not returned. For the same reason, some of
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the data sought from municipal agencies also are not available for this report. Tables 3-1 and 3-2
are summaries of the regulatory controls used by States and municipalities as presented on Table
A-l: State regulations on the control of construction phase storm water.
Many data were not readily available. Appendix A presents Tables A-l which includes all of the
data that was collected.
The data collected reflect a cross section of the US geography but are representative primarily of
municipalities that have a population of 100,000 or greater and relatively few municipalities of
smaller population. Thirty-one municipalities are included in the summary tables, which is a
relatively small data set compared to the approximately 240 municipalities with NPDES
programs and nearly 3,000 municipalities nationwide. Therefore, the data presented for the
States in Table 3-1 is fairly comprehensive while data for the municipalities presented in Table 3-
2 is not comprehensive but does reflect the diversity of management techniques used at the
municipal level.
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Table 3-1. State or Regional Planning Authority Requirements
for Water Quality Protection
Standard
Solids or sediment
percent reduction
Numeric effluent limits
for TSS, settleable
solids, or turbidity
Numeric design depth or
volume for water quality
treatment
Habitat/biological
measures
Physical in-stream
condition controls
Water Quality or
Effluent Monitoring
Requirement
Number of
States with
Requirement9
• 11
2
22
3 •
8
3
Percent of
National
Developed
Acreage with
Requirement
24% '
11%
53%
7%
17%
6%
Percent of
National
Developed
Acreage
without
Requirement
61%
76%
28%
80%
70%
83%
Percent of
National
Developed
Acreage
without
Information
15%
13%
19%
13%
13%
11%
a Florida has 5 Water Management Districts. If any of these Districts met a particular standard, the
entire state annual developed acreage was counted.
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Table 3-2. Municipal Planning Authority Requirements
Standard
Design storm for peak
discharge control
Solids or sediment
percent reduction
Numeric design depth,
storm, or volume for
water quality treatment
Design storm for flood
control
Habitat/biological
measures
Physical in-stream
condition controls
Percent of
Municipalities
Reviewed with
Requirement
39%
7%
-
39%
3%
10%
Percent of
Municipalities
' Reviewed without
Requirement
45%
77%
-
16%
65%
58%
Percent of
Municipalities
without
Information
16%
16%
-
23%
32%
32%
Note: This table reflects data collected from 31 municipalities
Tables 3-1 and 3-2 indicate that the following key control measures are being employed by States
and municipal/regional authorities to implement the NPDES Storm Water Program:
• Storm water controls designed for peak discharge control
• Storm water controls designed for water quality control
• Storm water controls designed for flood control
• Specified depths of runoff for water quality control
• Percent reduction of loadings for water quality control (primarily solids and sediments)
• Numeric effluent limits for water quality control (primarily total suspended solids, settleable
solids, or turbidity)
• Control measures for biological or habitat protection
• Control measures for physical in-stream condition controls (primarily streambed and
streambank erosion).
The water quantity control measures for peak discharge and runoff volume controls that apply to
the post-development conditions typically are not applicable during the construction phase when
the site is disturbed. Pollutant control measures are commonly required during the construction
phase, though the requirements for post-development storm water management are broader and
potentially more stringent.
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3.4 OTHER DATA SOURCES
3.4.1 PHASE II STORM WATER RULE ECONOMIC ANALYSIS
The Economic Analysis of the Final Phase II Storm Water Rule (USEPA, 1999) estimated Phase
II Storm Water Rule compliance costs for two major categories of pollutant controls for
construction sites: erosion and sediment control BMPs and post-construction storm water
management controls. Total costs for implementing the Phase II Rule encompass expenditures
for installation of erosion and sediment control technologies, labor requirements for submitting a
Notice of Intent (NOI) to be covered by a general permit, a Notification to Municipalities, a
Storm Water Pollution Prevention Plan (SWPPP), and maintenance costs. Costs were derived on
a per-site basis and then aggregated to the State and national level based on the number of
building permits issued. As described in the Economic Analysis Report for the Phase II Rule,
census data were used to project the annual number of construction permits by Standard
Industrial Classification (SIC) Code and construction permit data from 14 municipalities were
used to categorize construction activities by site size.
3.4.2 1997 USDA NATIONAL RESOURCE INVENTORY
The 1997 National Resources Inventory (NRI) (USDA, 2000) is a statistically based survey that.
has been designed and implemented to assess conditions and trends of soil, water, and related
resources on non-Federal lands in the United States. The NRI is conducted every 5 years by the.
U.S. Department of Agriculture's (USDA) Natural Resources Conservation Service (NRCS), in
cooperation with the Iowa State University Statistical Laboratory. The inventory provides
scientifically valid, timely, and relevant information that is used to formulate effective
agricultural and environmental policies and legislation, implement resource conservation
programs, and enhance the public's understanding of natural resources arid environmental
conditions.
The NRI is a compilation of natural resource information on non-Federal land in the United
States-nearly 75 percent of the country's land base. The inventory captures data on land cover
and use, soil erosion, prime farmland, wetlands, habitat diversity, selected conservation practices,
and related resource attributes at more than 800,000 scientifically selected sample sites. The NRI
can be accessed at http://www.nrcs.usda.gov/technical/NRI/.
3.4.3 NATIONAL STORM WATER BMP DATABASE
The National Stormwater BMP Database, developed by the American Society of Civil Engineers
(ASCE), is designed to be a source of reliable data to help improve water quality nationwide by
sharing consistent and transferable information on the performance of storm water best
management practices. The database helps water quality professionals across the United States
learn about successful BMPs and apply proven methods to local water quality projects. The
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database is based on extensive screening of a bibliography of more than 800 existing BMP
studies and was designed by national storm water experts on ASCE's Urban Water Resources
Research Council. As of June 2002, the database contains data on 198 BMPs. Representative
information provided for BMPs includes test site location, researcher contact data, watershed
characteristics, regional climate statistics, BMP design parameters, monitoring equipment types,
and monitoring data such as precipitation, flow, and water quality. The database can be accessed
online at http://www.bmpdatabase.org.
3.4.4
BMP DESIGN MANUALS AND GUIDANCE DOCUMENTS DEVELOPED
BY GOVERNMENTAL AND OTHER ORGANIZATIONS
A variety of manuals and documents were used to obtain information on design and effectiveness
of various BMPs. Examples include: (1) State design manuals such as the Virginia Erosion and
Sediment Control Handbook (http://www.dcr.state.va.us/sw/e&s-ftp.htmX the Maryland Storm
Water Design Manual rhtrp://www.mde.state.md.us/environment/wma/stormwatermanualX and
the Denver Urban Drainage Criteria Manual (http://www.udfcd.org): (2) Guidance documents
such as the Texas Nonpoint Source Book http://www.txnpsbook.org) and EPA's National Menu
of BMPs (http://www.epa.gov/npdes/menuofbmps/menu.htm): and (3) Consensus design
manuals such as manuals of practice on storm water design developed by ASCE and the Water
Environment Federation (ASCE and WEF, 1992 and!998) were used to determine various
management strategies. Links to on-line manuals and guidance documents are provided on
EPA's website at http://www.epa.gov/waterscience/guide/construction/.
3.5 REFERENCES
ASCE and WEF. 1992. Design and Construction of Urban Stormwater Management Systems.
ASCE Manual and Report on Engineering Practice No. 77; WEF Manual of Practice No.
FD-20. American Society of Civil Engineers, New York, NY. Water Environment
Federation, Alexandria, VA. http://www.asce.org and http://www.wef.org .
ASCE and WEF. 1998. Urban Runoff Quality Management. ASCE Manual and Report on
Engineering Practice No. 87; WEF Manual of Practice No. 23. American Society of Civil
Engineers, Reston, VA. Water Environment Federation, Alexandria, VA.
http://www.asce.org and http://www.wef.org .'
USEPA. 1999. Economic Analysis of the Final Phase II Storm Water Rule. U.S. Environmental
Protection Agency, Office of Wastewater Management. Washington, DC.
USDA. 2000.1997 National Resources Inventory. U.S. Department of Agriculture, National
Resources Conservation Service, Washington, DC.
http://www.nrcs.usda.gov/technical/NRI/.
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SECTION 4: INDUSTRY PROFILE
4.1 INTRODUCTION
The construction sector is among the largest and most important sectors in the national
economy, accounting for approximately 4 percent of the U.S. gross domestic product. During
1997, approximately 262,000 construction companies with payroll in the United States employed
nearly 2.4 million workers nationwide. Another 1.6 million workers associated with construction
activities were self-employed. The construction industry is divided into three major subsectors:
general building contractors, heavy construction contractors, and special trade contractors.
General contractors build residential, industrial, commercial, and other buildings. Heavy
construction contractors build sewers, roads, highways, bridges, and tunnels. Special trade
contractors typically provide carpentry, painting, plumbing, and electrical services.
Because the proposed effluent guidelines are being developed to address water quality issues,
this document focuses on the construction subsectors most closely associated with land-
disturbing activities. General contractors and heavy construction establishments are by definition
the most likely to conduct activities that could affect water resources. It should be noted,
however, that for individual projects responsibility for land-disturbing activities and potential
impacts on water quality might not be obvious because general contractors often subcontract all
or some of the actual construction work. Hence, the following subsections describe the subsector
categories most likely to be responsible for land-disturbing activities at the national level.
4.2 INDUSTRY DESCRIPTION
4.2.1 INDUSTRY DEFINITION AND CLASSIFICATION OF SUBSECTORS BY NAIC
AND SIC CODES
The construction and land development industry is classified in the 1997 North American
Industry Classification System (NAICS, 1997) under Sector 23, Construction. NAICS 1997 is
the system currently used for' classifying industry establishments by type of economic activity. It
replaced the U.S. Standard Industrial Classification (SIC) system.
Construction work includes new construction, additions, alterations, and repairs. Establishments
identified as construction-management firms are also included. The construction sector is divided
into three types of activities or subsectors:
• Subsector 233-Building, Developing, and General Contracting
This subsector is made up of establishments responsible for the construction of building
projects. Builders, developers, and general contractors, as well as land subdividers and
land developers, are included in the subsector. The construction work may be done for
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others and performed by custom builders, general contractors, design builders, or turnkey
contractors. This construction activity may be for sale as performed by speculative or
operative builders.
• Subsector 234—Heavy Construction
This subsector comprises establishments engaged in the construction of heavy
engineering and industrial projects (except buildings), such as highways, power plants,
and pipelines. Establishments in this subsector usually assume responsibility for entire
nonbuilding projects, but they may hire subcontractors for some or all of the actual
construction work. Special trade contractors are included in this group if they are
engaged in activities primarily related to heavy construction, such as grading for
highways. The kinds of establishments in this group include heavy-construction general
contractors and design builders.
• Subsector 235-Special Trade Contractors
This subsector comprises establishments engaged in specialized construction activities,
such as plumbing, painting, and electrical work.. The activities in this subsector may be
subcontracted from builders or general contractors, or the work may be performed
directly for project owners. Special trade contractors usually perform most of their work
at the job site..
Table 4-1 provides a list of the 3-digit subsectors, 4-digit industry groups and 5-digit NAICS
industries in the construction sector.
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Table 4-1. 1997 NAICS, Subsectors, Industry Groups,
and Industries Performing Construction Activities
That Might Disturb Land
1997 NAICS Sector 23 - Construction
233
2331
23311
2332
23321
23322
2333
23331
23332
234
2341
23411
23412
2349
23491
23492
23493
23499
235
2357
23571
2359
23593
Building, Developing, and General Contracting
Land Subdivision and Land Development
Land Subdivision and Land Development
Residential Building Construction
Single-family Housing Construction
Multifamily Housing Construction
Nonresidential Building Construction
Manufacturing and Industrial Building Construction
Commercial and Institutional Building Construction
Heavy Construction
Highway, Street, Bridge, and Tunnel Construction
Highway and Street Construction
Bridge and Tunnel Construction
Other Heavy Construction
Water, Sewer, and Pipeline Construction
Power and Communication Transmission Line Construction
Industrial Nonbuilding Structure Construction
All Other Heavy Construction
Special Trade Contractors
Concrete Contractors
Concrete Contractors
Other Special Trade Contractors
Excavation Contractors
Before the creation of the NAICS, construction and land development industries were classified
using the SIC system. Any data collected before January 1997 might still be classified under that
system. SIC classifications are relevant to the effluent guidelines, because certain U.S. Bureau of
the Census (BOC) data for the construction industry were collected until 1994 and therefore
classified under the SIC system rather than the NAICS. Under the SIC system, industries that
might perform land-disturbing activities were classified under Division C-Construction, and
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Division H-Finance, Insurance, and Real Estate. These divisions include the following SIC
major groups:
• SIC Major Group 15-Building Construction General Contractors and Operative Builders
This group includes general contractors and operative builders primarily engaged in the
construction of residential, farm, commercial, or other buildings. General building
contractors who combine a special trade with their contracting are also included,
• SIC Major Group 16-Heavy Construction Other Than Building Construction Contractors
This group includes general contractors primarily engaged in heavy construction other
than building construction, such as highways and streets, bridges, sewers, railroads,
irrigation projects, flood control projects, and marine construction, as well as special
trade contractors primarily engaged in activities of a type clearly specialized in such
heavy construction and not normally performed on buildings or building-related projects.
• SIC Major Group 17-Construction Special Trade Contractors
^
This group includes special trade contractors who undertake activities of a type that are
specialized either in building construction or in both building and nonbuilding projects.
• SIC Major Group 65-Real Estate
This group includes real estate operators and the owners and lessors of real property, as
well as buyers, sellers, developers, agents, and brokers.
Major groups 15 and 16 are further defined by the type of construction performed. Table 4-2
provides a list of the more specific industry groups and industries that might perform land-
disturbing activities.
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Table 4-2. 1987 SIC Industry Groups Performing Construction
Activities That May Disturb Land
SIC Major Group 15
Industry Group 152: General Building Contractors - Residential
1521
General Contractors - Single-family Houses
1522
General Contractors - Residential Buildings, Other Than Single-family
Industry Group 153: Operative Builders
1531 Operative Builders
Industry Group 154: General Building Contractors - Nonresidential
1541
General Contractors - Industrial Buildings and Warehouses
1542 General Contractors - Nonresidential Buildings, Other Than Industrial
SIC Major Group 16
Industry Group 161: Highway and Street Construction, Except Elevated Highways
1611 Highway and Street Construction, Except Elevated Highways
Industry Group 162: Heavy Construction, Except Highway and Street
1622
Bridge, Tunnel, and Elevated Highway Construction
1623
Water, Sewer, Pipeline, and Communications and Power Line
1629 Heavy Construction Not Elsewhere Classified
SIC Major Group 17
Industry Group 179: Miscellaneous Special Trade Contractors
1771
Concrete Work
1794 Excavation Work
SIC Major Group 65
Industry Group 655: Land Subdividers and Developers
6552
Land Subdividers and Developers, Except Cemeteries
The focus of this Development Document is on construction activities carried out by firms
covered by NAICS codes 233 and 234 or SIC codes 15 and 16. (As discussed in Section VIA in
the preamble of the proposed rule, Special Trade Contractors, NAICS 235 or SIC 17, are
typically subcontractors and not identified as NPDES permittees.) Furthermore, the residential,
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non-residential, and heavy construction subsectors receive the greatest emphasis, because they
account for the vast majority of construction projects and are responsible for most of the land
disturbance in the United States. The following subsections describe these subsectors in terms of
size, distribution, and recent growth trends.
4.2.2
RESIDENTIAL BUILDING CONSTRUCTION GROUP
Residential Construction Industry Description. The U.S. Bureau of the Census (BOC), a
division of the Department of Commerce (DOC), divides the residential construction industry
into two categories. The first encompasses single-family housing construction and includes
mobile homes, prefabricated houses, row houses, town houses, and single-family detached
houses. The second encompasses, multifamily housing construction and includes high-rise
apartments, garden apartments, and town house apartments in which units are not separated by
ground-to-roof walls.
Historic Trends. The DOC began collecting detailed information on housing starts in 1963.
Data on housing permits and starts are published monthly by the DOC and are viewed by
economists as leading indicators of economic activity. More detailed industry information is
collected through the Census of Construction Industries (CCI), which is conducted every 5 years
(in years ending in a 2 or a 7) as part of the Census Bureau's Economic Census program. These
data provide the most detailed snapshot of the status of the construction industry. The CCI
covers all employer establishments primarily engaged in construction as defined by the NAICS
and includes nonresidential construction activities. Table 4-3 summarizes housing starts for the
period from 1979 to 1999.
In Table 4-3, the number of construction starts is shown by regional location and type 'of
structure. The table also provides national totals for both single- and multifamily housing starts
(BOC, 2001). As shown in the table, single-family housing starts account for the majority of
housing construction starts. Figure 4-1 combines single- and multifamily housing starts and
graphically depicts annual changes during the 1997-1999 period. The number of construction
starts for privately owned housing units has decreased from approximately 1.7 million starts in
1979 to roughly 1.6 million starts in 1999 (BOC, 2001).
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Table 4-3. Annual Housing Construction Starts by Type and Region
(Starts are in thousands)
Year
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
United
States
1,745
1,292
1,084
1,062
1,703
1,750
1,742 "
1,805
1,621
.1,488
1,376
1,193
1,014
1,200
1,288
1,457 ,
1,354
1,447
1,474
1,617
1,641
Northeast
Single-
family
123
87
84
79
123
158
182
228
204
181
132
104
99
112
116
123
102
112
111
122
126
Multi-
family
55
38
33
37
45.
46
70
66
65
54
47
27
14
15
11
16
16
20
26 .
26
29
Midwest
Single-
family
243
142
no.
99
153
167
148
188
203
194
190
193
191
236
251
268
233
254
238
223
289
Multi-
family
106
76
55
50
65'
76
92
108
95
80
76
60
•42
52
47
61
57
68
66
58
59
South
Single-
family
522
428
363
357
557
528
504
504
485
443
, 409
371
353
439
498
522
485
524
507
573
580
Multi-
family
225
215
198
234
378
338
278
229
149
132
127
108
62
58
63
117
130
138
164
169
167
West
Single-
family
306
196
148
127
234
230
239
261
255
264
272
226
197
244
261
286
256
271
278
303
308
Multi-
family
165
110
' 92
78
148
206
230
222
165
140
124
103
57
45
41
65
76
90
. 86
92
84
Source: BOC, 2001.
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Housing start data tend to reflect the health of the U.S. economy. Therefore, as shown in Figure
4-1, the number of housing starts dropped significantly from 1986 to 1991 as the national
economy fell into a recession. Conversely, the robust economy over the past several years has
been accompanied by a strong growth in housing starts.
2,000 T-
1,800 • -
1,600 • -
800--
1979
1981
-
1983 1985 1987 1989 1991 1993 ' 1995 1997 1999
Year
Figure 4-1. Annual Housing Starts
Industry Size. As a result of the recent strong growth in demand for new housing, the number of
workers employed in residential construction has also increased. According to the BOC (1999b),
the total number of employees in the housing construction industry rose from 452,257 in 1992 to
628,886 in 1997, an increase of almost 40 percent. Table 4-4 shows the number of workers
employed, the payroll for those workers, and the value of completed construction for 1997. As
shown in the table, the number of establishments and workers associated with construction of
single-family housing greatly exceeds that for multifamily housing construction. It should also
be noted that although construction of single-family homes is performed by both small and large
firms, most multifamily housing construction is performed by large firms. Specifically, a special
study by the Census Bureau (BOC, 2000a) found that about 39 percent of single-family homes
are built by small builders (fewer than 25 units in the year); 21 percent by medium builders (25-
99 units); and 40 percent by large builders (more than 100 units). In contrast, construction of
multifamily housing is performed primarily by larger builders. During 1997, large builders
constructed 77 percent of multifamily housing units.
The value of construction is defined as work done by general contractors, heavy construction
contractors, and special trade contractors. Included in these estimates are new construction.;
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additions, alterations or reconstruction, and maintenance and repair; the costs of industrial and
other special equipment not an integral part of a structure are excluded. According to the 1997
Construction Census, the value of completed construction exceeded $161 billion. Single-family
housing construction accounted for almost $147 billion, or more than 90 percent of the total.
Table 4-4. Residential Construction Industry Profile for 1997
Total number of employees
Number of construction
establishments during the
year
Payroll (thousands)
Value of construction
completed nationwide
State with the highest dollar
value of construction work
for establishments with
payroll
Single-Family Housing
Construction
570,990
138,849
$14,964,583
$146,798,768
California
($18,137,680)
Multifamily Housing
Construction
58,896
7,543
$1,794,143
$14,487,308
Florida
($2,403,233)
Source: BOC, 1999b, 1999cT
"Single-Family Housing Construction Trends. As noted earlier, housing construction starts
increased significantly during the second half of the 1990s. In 1999, single-family home
construction starts totaled more than 1.3 million, a level not reached since 1978 (BOC 2001).
As indicated in Table 4-5 by the number of permits issued, Atlanta, Georgia, led all U.S. major
markets for single-family housing construction activity in 19991. The other leading market areas
for single-family construction were Phoenix, Arizona; Dallas-Ft. Worth, Texas; Chicago,
Illinois; and Washington, D.C. Table 4-5 also shows the percent change in construction permits
issued from 1998 to 1999 (U.S. Housing Markets, 1999a).
Multifamily Housing Construction Trends. Construction of structures with multiple housing
units also increased significantly during the 1990s. For example, construction starts of these
1 Permits issued do not necessarily translate into housing starts, since a permit issued in
one year may not lead to actual construction until the next year. Furthermore, some permits
issued never lead to actual construction. Nonetheless, permit counts can serve as a good
indicator of construction activity in the near future.
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buildings increased from about 173,500 in 1991 to more than 338,500 in 1999, an increase of
about 95 percent.
Table 4-5. Busiest Markets for Single-Family
Housing Permits for 1999
Market Area
Atlanta
Phoenix
Dallas-Ft. Worth
Chicago
Washington, DC
Single-family Housing
Permits (1999)
25,066
21,290
17,434
14,954
14,703
Percent Change
From 1998
. +11%
+13%
+6%
+7%
0.07
Source: U.S. Housing Markets, 1999a.
Much of the growth in multifamily housing was in the construction of facilities with more than
five units. According to U.S. Housing Markets (1999b), the top five busiest markets for
multifamily construction permits for 1999 were Dallas-Ft. Worth, Texas; Orlando, Florida; New
York-Long Island; Puget Sound, Washington; and Houston, Texas. Table 4-6 shows the number
of multifamily permits and the percent change in permits issued from 1998 to 1999.
Regional Housing Start Trends (Single-family and Multifamily Structures). The Census Bureau
estimates housing starts at the regional level through statistical analysis of its survey data.
Table 4-6. Busiest Markets for Multifamily
Housing Permits for 1999
Market Area
Dallas-Ft. Worth
Orlando
New York-Long Island
Puget Sound
Houston
Multifamily Housing
Permits (1999)
8,488
7,303
6,255
6,122
5,900
Percent Change
From 1998
-15%
+46%
+55% t ,
+19%
-50%
Source: U.S. Housing Markets, 1999b.
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As shown in Figure 4-2, the Census Bureau divides the United States into four regions:
Northeast2, Midwest3, South4, and West5. Table 4-7 summarizes changes in construction starts
at the regional level for the years 1989 and 1999.
Rl
Regions
Midwest
HI Northeast
E%^j South
| ~[ West .
Figure 4-2. Bureau of Census Housing Regions
As noted earlier, national housing starts have increased significantly over the past decade. At the
regional level, however, growth rates have varied to a large degree. As shown in Figure 4-3 and
The Northeast includes the following states: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New
York, Pennsylvania, Rhode Island, and Vermont.
The Midwest includes the following states: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska,
North Dakota, Ohio, South Dakota, and Wisconsin.
4
The South includes the following states: Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia,
Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma,.South Carolina, Tennessee, Texas, Virginia, and West
Virginia.
The West includes the following states: Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada,
New Mexico, Oregon, Utah, Washington, and Wyoming.
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summarized in Table 4-7, construction of housing increased by nearly 40 percent in the South,
whereas construction starts in the Northeast actually decreased by almost 13 percent
from 1989 levels. Housing starts in the Midwest also increased significantly over 1989 levels
while housing starts in the West remained at about the same level as a decade earlier.
Table 4-7. Changes in Housing Starts by Region (1989 and 1999)
Region
Northeast
Midwest
South
West
Total
1989 Housing Starts
(in thousands)
178.5
265.8
536.2
395.7
1,376.1
1999 Housing Starts
(in thousands)
155.7
347.3
746.0
391.9
1,640.9
Percent Change from
1989 to 1999
-12.77
30.66 ,
39.13
-0.96
19.24
Source: BOC, 1999a, 2001
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800
1988
1990
1992
1996
1994
Year
Northeast-*- Midwest* South ^ West
1998
2000
Figure 4-3. Annual Housing Starts by Region
4.2.3 NONRESIDENTIAL BUILDING CONSTRUCTION GROUP
The NAICS Nonresidential Building Construction group comprises establishments classified
either as Manufacturing and Industrial Building Construction or Commercial and Institutional
Building Construction. The following buildings are considered nonresidential by the U.S.
Census Bureau and fall under either the manufacturing or the commercial classification:
manufacturing and light industrial buildings; manufacturing and light industrial warehouses;
hotels and motels; office buildings; all other commercial buildings not elsewhere classified, such
as stores, restaurants, and automobile service stations; commercial warehouses; religious
buildings; educational buildings; health care and institutional buildings; public safety buildings;
nonresidential farm buildings; amusement, social, and recreational buildings; and all other
nonresidential buildings. Because of the transition from the SIC system used in the 1992
Economic Census to theJNAICS for the 1997 census, a valid comparison of data between the two
censuses is not feasible, and therefore no historical data are shown.
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Manufacturing and Industrial Building Construction. This industry type comprises
establishments primarily responsible for the entire construction of manufacturing and industrial
establishments, such as plants, mills, and factories. Establishments identified as management
firms for manufacturing and industrial building construction are also part of this industry. They
include manufacturing and industrial building general contractors, design builders, engineer-
constructors, joint-venture contractors, and turnkey contractors (BOC, 1999e).
In 1997, there were 7,280 manufacturing and industrial building construction establishments with
payroll (BOC, 1999e). These establishments employed 143,066 people for a total payroll of
more than $5.1 billion. The total value of manufacturing and industrial building construction
work in 1997 was more than $33.5 billion (BOC, 1999e). The value of construction work in
1997 by construction type is shown in Table 4-8 and includes new construction, additions,
alterations or reconstruction, maintenance and repair, and any construction work done by the
reporting establishments for themselves.
Table 4-9 shows the value U.S. of construction work for establishments with payroll by work
location. States are grouped into four geographic regions: Northeast, Midwest, South, and West.
The South and the Midwest each accounted for approximately one-third of total 1997
construction value (southern region, approximately 32.4 percent; Midwest, nearly 30.1 percent).
The West and Northeast made up the remaining third (West, 23.4 percent; Northeast, 11.1
percent). Of the 50 states, California had the highest value of construction work at $3.4 billion,
10.1 percent of the total for the entire United States. Michigan had the second-highest amount at
$2.9 billion (8.7 percent), followed by Texas at $1.9 billion (5.8 percent), and Ohio at $1.8
billion (5.3 percent). The remaining states and Washington, D.C., each had less than 5 percent of
the total value of manufacturing and industrial building construction work in the United States in
1997.
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Table 4-8. Value of Construction Work for Manufacturing and Industrial Building
Construction Establishments With Payroll by Type of Construction, 1997
Type of Construction
Manufacturing and Light
Industrial Buildings
Manufacturing and Light
Industrial Warehouses
Hotels and Motels
Office Buildings
All Other Commercial Buildings,
Not Elsewhere Classified
Commercial Warehouses
Educational Buildings
Health Care and Institutional
Buildings
All Other Nonresidential
Buildings
Building Construction, Total
Nonbuilding Construction, Total1
Construction Work, Not Specified
by Kind
Manufacturing and Industrial
Building Construction, Total2
Value of Construction Work (thousands of dollars)
Total
$17,590,062
7,058,148
432,789
2,478,594
1,141,600
1,040,691 '
823,028
862,907
1,580,244
33,008,063
503,956
2,324
$33,514,342
New
Construction
$10,914,455
5,421,819
373,322
1,570,275
799,522
883,412
541,081
464,788
1,073,758
22,042,431
316,697
Not
Applicable
$22,359,127
Additions,
Alterations, or
Reconstruction
$4,280,143
1,358,864
49,580
810,808
298,166
131,005
255,540
355,116
436,029
7,975,252
123,832
Not
Applicable
$8,099,084
Maintenance
and Repair
$2,395,463
277,466
9,887
97,511
43,912
26,275
26,407
43,003
70,457
2,990,381
63,427
Not
Applicable
$3,053,807
1. This information is shown for the breakdown of total industrial building construction values.
2. Detail may not add to total because of rounding.
Source: BOC, 1999e.
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Table 4-9. Value of Manufacturing and Industrial Building
Construction Work for Establishments with Payroll
by Location of Construction Work, 1997
(thousands of dollars)
Northeast
CT $260,593
ME 170,314
MA 403,700
NH 68,159
NJ 755,854
NY 920,425
PA 1,114,271
RI D
VT 14,812'
Total: $3,708,1282
Midwest
IL $1,208,663
IN 1,207,426
IA 381,922
KS 281,419
MI 2,908,857
MN 593,542
MO 745,632
NE 221,626
ND 89,251
OH 1,772,426
SD D
WI 669,575
Total: $10,080,339^
South
AL $1,080,420
AR 182,142
DE 169,305
DC 3,685
FL 920,179
GA 1,090,761
KY 861,206
LA 521,420
MD 253,778
MS 284,626
NC 921,364
OK 190,593
SC 689,581
TN 946,818
TX 1,934,909
VA 677,103
WV 144,481
Total: $10,872,3712
West
AK $62,907
AZ 561,785
CA 3,440,637
CO 330,551
HI S
ID 776,661
MT 26,176
NV 86,998
NM 377,538
OR 895,078
UT 314,621
WA 915,678
WY 52,326
Total: $7,840,9562
Total Value of Construction for United States: 33,514,3422
D: Withheld to avoid disclosing data of individual companies; data are included in
United States total.
S: Withheld because estimates did not meet publication standards.
1. Sampling error exceeds 40 percent.
2. Totals for regions do not include states with "S" and "D" criteria.
Source: BOC, 1999e. •
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Commercial and Institutional Building Construction. This industry type comprises
.establishments primarily responsible for the entire construction of commercial and institutional
buildings, such as stores, schools, hospitals, office buildings, and public warehouses (BOC,
1999d). Establishments identified as management firms for commercial and institutional
building construction are also part of this industry type, which includes commercial and
institutional building general contractors, design builders, engineer-constructors, joint-venture
contractors, and turnkey contractors (BOC, 1999d).
In 1997, there were 37,430 commercial and institutional building construction establishments in
the United States employing a total of 528,173 people, with a payroll of $19.2 billion (BOC,
1999d). The value of construction work in 1997 by construction type is shown in Table 4-10.
Value includes new construction, additions, alterations or reconstruction, maintenance and repair,
and any construction work done by the reporting establishments for themselves (BOC, 1999d).
Table 4-11 shows the value of commercial and institutional building construction work by
location. The data are reported by state, by region (Northeast, Midwest, South, and West), and
for the entire United States. The South had the highest dollar value of construction activity,
accounting for $47.9 billion (27.7 percent) of commercial and institutional building construction
in the entire U.S. The West accounted for 20.6 percent of the total, followed by the Midwest at
16.8 percent, and then the Northeast at 9.7 percent. Of the 50 states, California had the highest
value of commercial and institutional construction work at $18 billion, or 10.4 percent of the
total for the entire United States. Texas had the second highest value of construction at
approximately $13 billion (7.5 percent), followed by Illinois at $7.9 billion (4.5 percent), and
then Georgia at $7.1 billion (4.1 percent). The remaining states and Washington, D.C. each
accounted for less than 4 percent of the total value of commercial and institutional building
construction work in the United States in 1997.
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Table 4-10. Value of Construction Work for Commercial and Institutional
Building Construction Establishments With Payroll
by Type of Construction, 1997
Type of Construction
Single-Family Houses, Detached
and Attached
Apartment Buildings,
Apartment-Type Condominiums
and Cooperatives
Manufacturing and Light
Industrial Buildings
Manufacturing and Light
Industrial Warehouses
Hotels and Motels
Office Buildings
All Other Commercial Buildings,
Not Elsewhere Classified
Commercial Warehouses
Religious Buildings
Educational Buildings
Health Care & Institutional
Buildings
Public Safety Buildings
Farm Buildings, Nonresidential
Amusement, Social, and
Recreational Buildings
Other Building Construction
Building Construction, Total
Value of Construction Work (thousands of dollars)
Total
$2,690,846
4,081,493
8,083,739
3,325,768
8,313,559
36,147,979
32,715,012
6,929,460
4,324,007
23,974,844
17,446,710
5,345,602
1,904,128
6,529,907
3,429,673
166,818,246
New
Construction
$1,473,065
2,905,159
5,201,932
2,428,651
6,433,138
21,235,715
21,866,915
5,465,600
2,870,724.
15,587,110
11,187,636
4,183,179
1,508,380
5,141,460
1,984,749
110,618,170
Additions,
Alterations, or
Reconstruction
$1,000,110
1,016,097
2,425,390
776,335
1,679,856
13,524,406
9,631,103
1,215,709
1,342,559
7,893,507
5,917,408
1,064,693
272,836
1,275,033
895,522
50,325,006
Maintenance
and Repair •
$217,672
160,237.
456,417
120,783
200,564
1,387,858
1,216,994
248,151
110,724
494,>227
361,666
97,730
122,912
113,414
549,401
5,875,070
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Type of Construction
Nonbuilding Construction1
Construction W.ork, Not
Specified by Kind
Commercial and Institutional
Building Construction, Total2
Value of Construction Work (thousands of dollars)
Total
4,091,548
2,295,888
$173,205,680
New
Construction
2,697,377
Not
Applicable
$113,315,547
Additions,
Alterations, or
Reconstruction
1,205,513
Not Applicable
$51,530,519
Maintenance
and Repair
188,658
Not
Applicable
$6,063,728
1. This information is shown for the breakdown of total industrial building construction values.
2. Detail may not add to total because of rounding.
Source: BOC, 1999d.
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Table 4-11. Value of Commercial and Institutional Building
Construction Work for Establishments With Payroll
by Location of Construction Work, 1997
(thousands of dollars)
Northeast
CT D
ME 385,818
MA 4,518,815
NH 697,186
NJ 4,973,021
NY D
PA 5,966,516
RI D
VT 303,481
Total: $16,844,837'
Midwest
IL 7,860,551
IN 3,132,116
IA 1,610,654
KS 1,609,747
MI 4,791,024
MN 3,361,074
MO D
NE 895,824
ND 297,619
OH 5,620,984
SD D
WI D
Total: $29,179,593'
South
AL D
AR D
DE 891,394
DC 1,724,839
FL D
GA 7,134,326
KY 1,961,212
LA 1,855,800
MD 3,693,531
MS D
NC 5,949,386
OK D
SC 2,417,316
TN 3,751,331
TX 12,953,464
VA 5,076,575
WV 529,092
Total: $47,938,266'
West
AK 509,429
AZ 3,287,644
CA 18,093,906
CO 3,728,688
HI D
ID D
MT 342,606
NV D
NM 913,252
OR 2,599,182
UT 1,796,639
WA 4,155,050
WY 211,989
Total: $35,638,385'
Total Value of Construction for United States: $173,205,6802
D: Withheld to avoid disclosing data of individual companies; data are included in
United States total.
1. Totals for regions do not include states with "D" criteria.
2. Detail may not add to total because of rounding, and because of "D" criteria.
Source: BOC, 1999d.
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4.2.4
HEAVY CONSTRUCTION SUBSECTOR
Industry Overview. The heavy construction industry encompasses broad types of activities with
highway and street construction; bridge and tunnel construction; and water, sewer, and pipeline
construction as the three main types of heavy construction. The U.S. Census Bureau administers
a separate economic census for each of these three types of construction activities.
In general, most of the heavy construction industry indicators (e.g., value of completed work;
employment) have increased over the past two decades, although the health of the industry, like
that of the housing subsector, is closely tied to the overall state of the U.S. economy. This
subsector has experienced both upturns and downturns over the past 20-year period.
The period encompassing the two most recent census years, 1992 and 1997, saw modest growth
in the heavy construction subsector. By 1997, the value of construction completed by the three
main types of heavy construction reached about $80 billion. As shown in Table 4-12, the .
highway construction category of the heavy construction subsector accounted for about 60
percent of the total value of heavy construction. Highway construction employed the majority of
workers in the heavy construction subsector, accounting for about 278,000 of a total of 488,000
employees for all three categories of heavy contructio'n (BOC, 1999g). Of the three heavy
construction categories, only the water, sewer, and pipeline category has experienced a decline in
number of establishments and number of employees.
Regional Distribution of Heavy Construction Activities. The U.S. Bureau of Census reports data
for the heavy construction industries at the state and regional levels. As in the case of the
housing subsector, the Census Bureau divides the United States into four major regions,
Northeast, Midwest, South, and West, each contributing to the total value of construction work.
As shown in Figure 4-4, the South and Midwest accounted for the majority of the establishments
and value of heavy construction work in 1997. In particular, these two regions accounted for 55
percent of the construction firms and 61 percent of the value of construction.
Of the three major types of heavy construction activities, highway.and street construction
accounted for almost 60 percent of the total value of heavy construction activities in 1997. The
distribution of highway construction establishments and the value of completed work among the
different regions of the country are similar to those of the other heavy construction categories
For example, the South contributed more than $16 billion, or 34 percent, to the total value of
highway construction work in the United States. It should be reiterated, however, that the census
provides only a snapshot and that construction activities such as highway construction are
dependent on government funding and can change significantly in magnitude and location over
time.
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Table 4-12. Overview of Heavy Construction
Industry, 1992 and 1997
Year
Highway
'Bridges
Water, Sewer,
and Pipeline
Value of Construction (thousands of dollars)
1992
1997
35,331,607
48,472,284
7,198,275
9,539,041
20,205,048
22,204,058
Number of Establishments
1992
1997
10,090
11,270
1,041
1,177
10,233
8,042
Number of Employees *
1992
1997
257,356
277,979
43,701
47,764
194,252
162,566
1. Number of employees is the sum of all employees during
the pay periods that include the 12th of March, May, August,
and November, divided by four.
Source: BOC, 1992a, 1992b, 1992c, 1999f, 1999g, 1999h.
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NKteast
Total
, Sfewr, atdPjidte
Figure 4-4. Value of Heavy Construction Work by Region, 1997
4.3 INDUSTRY PRACTICES AND TRENDS
4.3.1
OVERVIEW OF CONSTRUCTION LAND-DISTURBING ACTIVITIES
Constructing a building or facility involves a variety of activities, including the use of equipment
that alters the site's environmental conditions. These changes include vegetation and top soil
removal, regrading, and drainage pattern alteration. The following provides a brief description of
typical land-disturbing activities at construction sites and the types of equipment employed.
Construction Site Preparation. Construction activities generally begin with the planning and
engineering of the site and site preparation. During this stage, mobile offices, which are usually
housed in trailers, are established on the construction site. The construction company uses these
temporary structures to handle vital activities such as preparing and submitting applicable
permits, hiring employees and subcontractors, and ensuring that proper environmental
requirements are met. The entire construction yard is delineated with erosion and sediment
controls installed and security measures established. The latter includes installing fences and.
signs to warn against trespassing and to mark dangerous areas. After the site is secured,
equipment is brought to the site (and is stored there throughout the construction period).
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Clearing, Excavating, and Grading. Construction on any size parcel of land almost always calls
for a remodeling of the earth (Lynch and Hack, 1984). Therefore, actual site construction begins
with site clearing and grading. Organic material cannot support the weight of buildings and
should be removed from the top layer of ground. (Some developers stockpile the organic material
for use during the landscaping phase of construction rather than paying for it to be hauled from
the site.) Construction contractors are to ensure that earthwork activities meet local, State, and
Federal regulations for soil and erosion control, runoff, and other environmental controls. The
size of the site, extent of water present, soil types, topography, and weather determine the kinds
of equipment used in site clearing and grading (Peurifoy and Oberlender, 1989). Material that
will not be used on the site should be hauled away by tractor-pulled wagons, dump tracks, or
articulated trucks (Peurifoy and Oberlender, 1989).
Equipment used for lifting excavated and cleared materials include aerial-work platforms,
forwarders, cranes, rough-terrain forklifts, and truck-mounted cranes. In addition, track loaders
are used for digging and dumping earth (Caterpillar, 2000; Construction Equipment On-Line,
1996-1998; Lynch and Hack, 1984; and Peurifoy and Oberlender, 1989).
Excavation and grading are performed by several different types of machines. These tasks can
also be done by hand, but this is generally more expensive (Lynch and Hack, 1984). When
grading a site, builders typically ensure that new grades are as close to the original as possible, to
avoid erosion and storm water runoff (Lynch and Hack, 1984). Proper grading also ensures a flat
surface for development and drains water away from constructed buildings.
Excavation and grading equipment includes backhoes, bulldozers (including the versatile tracked
bulldozer), loaders, directional drilling rigs, hydraulic excavators, motor graders, scrapers,
skid-steer loaders, soil stabilizers, tool carriers, trenchers, wheel loaders, and pipeliners.
Equipment selection depends on functions to be performed and specific site conditions
(Caterpillar, 2000; Construction Equipment On-Line, 1996-1998; Lynch and Hack, ,1984; and
Peurifoy and Oberlender, 1989). Therefore, multiple types of equipment are used throughout the
clearing and grading process.
Self-transporting trenching machines, wheelrtype trenching machines, and ladder-type trenching
machines are also used during site excavation. Self-transporting trenching machines are used to
create shallow trenches, such as for underground wire and cables. This type of machine has a
bulldozer blade attached to the front, is highly maneuverable, and can be used to dig narrow,
shallow trenches. Wheel-type trenching machines also dig narrow trenches, most often for water
mains and gas and oil pipelines. Ladder-type trenching machines are used to dig deep trenches,
such as for sewer pipes. These machines might have a boom mounted at the rear. Along the
boom are cutter teeth and buckets that are attached to chains. As the machine moves, it digs dirt
and moves it to the sides of the newly formed trench (Peurifoy and Oberlender, 1989).
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Power shovels can also be used for excavating soils. They are used on all classes of earth that
have not-been loosened. For solid rock, prior loosening is often necessary. As materials are
excavated, they are immediately loaded onto trucks or tractor-pulled wagons and hauled from the
site (Peurifoy and Oberlender, 1989). Hydraulic excavators, with either a front or a back shovel,
are also used to dig into the earth and to load a hauling vehicle. There are several categories of
hydraulic excavators, including backhoes, back shovels, hoes, and pull shovels. Hydraulic
excavators are one of the most widely used types of excavating equipment because of their ease
of use and their ability to remove the earth that caves as it is moved. They are effective
excavating machines, and they are easy to use in terms of loading some sort of hauling vehicle
(Peurifoy and Oberlender, 1989).
Draglines, used to dig ditches or build levees, can transport soil within casting limits, thus
eliminating the need for hauling equipment (Peurifoy and Oberlender, 1989). Draglines have a
bucket that hangs from a cable. The bucket is brought through the dirt and toward the operator
(Lynch and Hack, 1984). Draglines can be used on both wet and dry ground and can dig earth
out of pits that contain water (Peurifoy and Oberlender, 1989). They are most useful for making
large cuts and channels betow the level of the machine as well as for making valleys, mounds,
slopes, and banks (Lynch and Hack, 1984). Draglines have a lower output than power shovels,
and do not excavate rock as well as power shovels (Peurifoy and Oberlender, 1989).
Draglines can be converted to clamshells by replacing the dragline bucket with a clamshell
bucket. A clamshell is typically used for handling sand, gravel, crushed stone, sandy loam, and
other loose materials; it is not efficient in handling compacted earth, clay, or other dense
materials. A clamshell is lowered into a material, and the bucket closes on the .material. It is
then raised over a hauling vehicle and the materials deposited (Peurifoy and Oberlender, 1989).
Scrapers, either self-powered or drawn by tractors, dig and compact materials by taking up earth
from its underside with toothed scoops and loading it into hauling vehicles. Scrapers are useful
in removing earth and weak or broken rock, and for excavating hills and rock faces. Some
scrapers are designed for long hauls; others with good traction are used on steep slopes (Lynch
and Hack, 1984).
A crawler tractor, which pulls a rubber-tired self-loading scraper, is often used for short-haul
distances. The crawler tractor uses a drawbar pull to load the scraper. It has good traction and
can operate on muddy roads. It is, however, a slower vehicle and thus is more appropriate for
shorter hauls.
Wheel-type tractor-pulled scrapers, which come in two- and four-wheel tractors, are used for
longer hauling distances. Unlike the crawler tractor-pulled scrapers, the wheel-type tractor-
pulled scrapers do not maintain good traction. Under such conditions, a helper tractor,, such as a
bulldozer, might be used (Peurifoy and Oberlender, 1989).
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All these machines shape and compact the earth, a crucial site preparation step. In addition,
earthwork activities might suggest that fill be brought in. In such cases, the fill should be spread
in uniform, thick layers and compacted to a specified density with an optimum moisture content.
Graders and bulldozers are the most common earth-spreading machines. Machines that compact
include tractor-pulled sheep's foot rollers, smooth-wheel rollers, pneumatic rollers, and vibrating
rollers, among other equipment (Peurifoy and Oberlender, 1989). Rollers and scarifiers are used
either to compact or to break up the ground (Lynch and Hack, 1984).
In order to remove rock, it should first be loosened and broken up, usually through drilling or
blasting. Drilling equipment includes jackhammers, wagon drills, drifters, churn rills, and rotary
drills; each is designed to work on a specific size and type of rock. Dynamite and other
explosives are used to loosen rock (Peurifoy and Oberlender, 1989).
Once materials have been excavated and removed and ground cleared and graded, the site is
ready for construction.
4.3.2
CONSTRUCTION SITE SIZE CATEGORIES AND ESTIMATES OF
AMOUNT OF DISTURBED LAND
The proposed effluent guidelines would apply to construction sites of all types (i.e., residential,
commercial, and industrial) of more than one acre (5 acres, in the case of the guideline's Option
2). Because the costs of best management practices (BMPs) for erosion and sediment control are
largely driven by site size, EPA estimated the distribution of construction sites-by size category,
land use type, and geographic region in order to estimate the total cost of the proposed rule. (In
addition, estimating distribution of sites by type allows EPA to estimate the cost to each
construction sector.)
The method used to estimate the number of construction sites by size category, and therefore the
total area disturbed, is based on a number of data sources, including U.S. Census data and data
collected during the Phase II Storm Water rulemaking.
4.3.2.1
National Estimates of Disturbed Acreage
EPA used the U.S. Department of Agriculture's (USDA's) 1997 National Resources Inventory
(NRI) to estimate the level of new U.S. development each year. (NRI is designed to track
changes in land cover and land use over time.) The inventory, conducted every five years, covers
all non-federal lands in the U.S. (75 percent of the U.S. total). The program captures land use
data from some 800,000 statistically selected locations. From 1992 to 1997, an average of 2.2
million acres per year were converted from non-developed to developed status. Table 4-13
shows the allocation of this converted land area by type of land or land cover.
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Table 4-13. Acres Converted from Undeveloped to Developed State",
1992-1997
Type of Land
Cropland
Conservation Reserve
Program land
Pastureland
Rangeland
Forest land
Other rural area
Water areas and federal land
Total
Acres Converted to
Development 1992-1997
(thousands)
Annual Average
574.8
1.5
391.2
. 245.9
939.0
89.1
1.8
2,243.4
Percent Contribution by
Type of Land
26.6%
0.1%
17.4%
11.0%
41.9%
4.0%
0.1%
100.0%
a. NRI defines developed land as a combination of the following land cover/use categories
large urban and built-up areas, small built-up areas, and rural transportation land.
These are defined as follows:
Large urban and built-up areas. A land cover/use category composed of developed tracts
of at least 10 acres and meeting the definition of urban and built-up areas.
Small built-up areas. A land cover/use category consisting of developed land units of 0.25
to 10 acres, which meet the definition of urban and built-up areas.
Rural transportation land. A land cover/use category which consists of all highways,
roads, railroads and associated right-of-ways outside urban and built-up areas; also
includes private roads to farmsteads or ranch headquarters, logging roads, and other
private roads (field lanes are not included).
Urban and built up areas are in turn defined as:
Urban and built-up areas. A land cover/use category consisting of residential, industrial,
commercial, and institutional land; construction sites; public administrative sites; railroad
yards; cemeteries; airports; golf courses; sanitary landfills; sewage treatment plants; water
control structures and spillways; other land used for such purposes; small parks (less than
10 acres) within urban and built-up areas; and highways, railroads , and other
ransportation facilities if they are surrounded by urban areas. Also included are tracts of
ess than 10 acres that do not meet the above definition but are completely surrounded by
Urban and built-up land. Two size categories are recognized in the NRI: areas of 0.25 acre
o 10 acres, and areas of at least 10 acres.
Source: USDA, 2000.
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4.3.2.2
Distribution of Acreage by Project Type
To allocate the NRI acreage among the various segments of the industry, EPA has estimated the
distribution of acres-developed by type of project in the following way. First, EPA multiplied
the number of building permits issued annually by estimates of the average site size for each
project type. Thus for single-family residential construction, EPA multiplied the number of new
single-family home building permits by the average lot size for new single-family construction.
Estimates for other types of construction were based on extrapolations from the U.S. Census
permit data and EPA estimates of average project size. Second, EPA adjusted the estimates of
acres converted to reconcile any differences between the total number of acres accounted for
using this approach and the total acres developed as estimated in the NRI.
Single-family Residential
Census data indicate that in recent years the number of new single-family housing units
authorized has averaged just over 1.0 million units per year (see Table 4-14). The average lot
size for new single-family housing units is 13,553 square feet, or 0.31 acres (1 acre = 43,560
square feet). Using the average lot size (see Table 4-15), however, will underestimate the total
acreage converted for single-family residential projects because it does not include common
areas of developments not counted as part of an owner's lot. These areas include streets,
sidewalks, parking areas, storm water management structures, and open spaces.
Table 4-14. New Single-Family and Multifamily Housing
Units Authorized, 1995-1997
Year
1995
1996
1997
1995-1997 avg
All Housing Units
1,332,549
1,425,616
1,441,136
1,399,767
Single-Family
Housing Units
997,268
1,069,472
1,062,396
1,043,045
Multifamily
Housing Units
335,281
356,144
378,740
356,722
Source: BOC, 2000b.
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Table 4-15. Average and Median Lot Size
for New Single-Family
Housing Units Sold, 1995-1997
Year
1995
1996
1997
1995-1997 avg
Average Lot Size
(Square Feet)
13,665
13,705
13,290
13,553
Median Lot Size
(Square Feet)
9,375
9,100
9,000
9,158
Source: BOC, 1995, 1996, 1997.
To account for these differences, EPA examined data obtained from a survey of municipalities
conducted in support of the Phase II Storm Water rule (EPA 1999). This survey identified 14
communities that consistently collected project type and size data as part of their construction
permitting programs.6 EPA's review of permitting data from these communities covered 852
single-family developments encompassing 18,134 housing units. The combined area of these
developments was 11,460 acres. This means that each housing unit accounted for 0.63 acres
(11,460 acres- 18,1.34 units = 0.63 acres per unit). This estimate, essentially double the average
lot size, appears to more than account for the common areas and undeveloped areas in a typical
single-family residential development. For this reason, EPA averaged the Census estimate of the
national average lot size (0.31 acres) and the Phase II estimate of 0.63 acres per unit to arrive at
an estimate of 0.47 acres per unit. This number was multiplied by the average number of single-
family housing units authorized by building permit, 1.04 million, to arrive at an estimate of
490,231 acres (see Table 4-18).
Multifamily Residential
For residential construction other than single-family housing, EPA divided the average number
of units authorized during 1995-1997 (356,722, from Table 4-14) by the average number of units
per new multifamily building. The average number of units per building was obtained by
examining the distribution of units by unit size class in Census data (BOC 2000b). EPA
estimated the number of buildings in each size class by dividing the number of units in each class
by the average number of units. The total number of units was then divided into the estimated
number of buildings to arrive at an average number of approximately 10 units per building across
6 The communities were: Austin, TX; Baltimore County, MD; Gary, NC; Ft. Collins, CO; Lacey, WA;
Loudoun County, VA; New Britain, CTf Olympia, WA; Prince George's County, MD; Raleigh, NC; South Bend,
IN; Tallahassee, FL; Tuscon, AZ; and Waukesha, WI.
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all building size classes. Dividing 356,722 units authorized (Table 4-14) by 10 units per building
project yields 35,672 individual development projects.
EPA next examined data on the average site size for multifamily residential developments. The
Center for Watershed Protection reports survey results showing that an average building footprint
occupies 15.6 percent of the total site (CWP 2001). EPA assumed that the average-sized
multifamily building (10.8 units) would have two floors and that each unit would occupy the
national average of 1,095 square feet (NAHB 2002). The total square footage accounted for by
living space is thus 11,826 square feet. Multiplying by a factor of 1.2 to account for common
areas and other non-living space (utility rooms, hallways, stairways), and dividing by 2 to reflect
the assumption of a 2-story structure, EPA obtained a typical building footprint of 7,096-square
feet (11,826 x 1.2 * 2 = 7,096). Combining this with the CWP estimate of the building footprint
share of total site size (15.6 percent), the average site size was estimated to be 45,487 square feet
(7,096'* 0.156 = 45,487), or just over 1 acre (1.04 acres).
EPA compared the average site size obtained using this approach with data from the 14
community survey referenced above under the Phase II Storm Water rule. That study's review of
permitting data identified 286 multifamily developments covering a total of 3,476 acres. The
average site size, 12.1 acres, is considerably higher than that calculated above. EPA has no
indication that the permits reviewed in these communities are for projects of a larger-than-
average size. Therefore, for purposes of this analysis, EPA has taken the midpoint of the
estimates, 6.5 acres, as the average size of multifamily projects. This number was multiplied by
the average number of multifamily housing developments authorized by building permit, 35,672,
to arrive at an estimate of 231,868 acres (see Table 4-18).
Nonresidential Construction
EPA lacked current data on the number of nonresidential construction and development projects
authorized annually because the Census Bureau ceased to collect data on the number of permits
issued for such projects in 1995. EPA used regression analysis to forecast the number of
nonresidential building permits issued in 1997, based on the historical relationship between
residential and nonresidential construction activity. Using this approach, EPA estimates that a
total of 426,024 nonresidential permits were issued in 1997. These represent a variety of project
types, including commercial and industrial, institutional, recreational, as well as nonresidential,
nonbuilding projects such as parks and road or highway projects.
EPA first combined a number of project types into a larger "commercial" category, which
included hotels and motels and retail and office projects, as well as religious, public works, and
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educational projects.7 EPA's reasoning for including the latter categories under the commercial
category is based on engineering judgment that erosion and sediment control practices would be
similar across each project type. The total estimated number of commercial permits in 1997 was
254,566 (59.7 percent of the nonresidential total). (EPA calculated a estimate for the industrial,
category, which totaled 12,140 permits (2.8 percent), separately.) The residual 159,318 permits
(37.4 percent), are nonbuilding, nonresidential projects that include parks, bridges, roads, and
highways. EPA accounts for these projects in the steps described below.
For the industrial and commercial categories, EPA reviewed the project size data collected from
the 14-community Phase II rule survey referenced earlier (EPA, 1999). This study identified 817
commercial sites occupying 5,514 acres and 115 industrial sites occupying 689 acres. The
average site sizes are 6.7 and 6.0 acres, respectively.
EPA also reviewed estimates from CWP (2001) on the average percent of commercial and
industrial sites taken up by the building footprint. These percentages, 19.1 and 19.6 respectively,
were multiplied across the model project site sizes of 1, 3, 7.5, 25, 70, and 200 acres to estimate
building size on each site, assuming single-story buildings in each case. These estimates are
shown in Table 4-16.
Table 4-16. Average Building Area
(square feet)
Project Size
(Acres)
1
3
7.5
25
70
200
Commercial
8,320
24,960 .
62,400
207,999
582,397
1,663,992
Industrial
8,555
25,666
64,164
213,880
598,863
1,711,037
Estimates were obtained by multiplying the site size in square
feet by the percentage of the site estimated to be occupied by
the building "footprint," based on data from CWP (2001).
As seen in the table, the average building size corresponding to the 6- to7- acre sites estimated
from the 14-community study are in the 60,000 square feet range. EPA next examined R.S.
The commercial category included: hotels/motels, amusement, religious, parking garages, service
stations, hospitals, offices, public works, educational, stores, and other nonresidential buildings.
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Means' Building Construction Cost Data (2000), which provides cost data for "typical"
commercial and industrial buildings. As part of the cost data, R.S. Means identifies the typical
range of building sizes based on a database of actual projects. Table 4-17 shows the typical size
and size range for a variety of building types that would fall into either the commercial or
industrial category. While some of the building types correspond with the estimated average of
60,000 square feet, these appear high for other categories, such as low-rise office and
supermarkets, warehouses, and elementary schools. EPA believes generally that there are more
small projects than large ones. As a result, EPA inferred that this approach would suggest an
average building size of 25,000 square feet, which implies an average site size of 3 acres, based
on Table 4-16.
To reconcile the estimates obtained from the two approaches, EPA has taken the midpoint of the
estimates. For commercial development, EPA assumes an average site size of 4.85 acres (the
average of 6.7 and 3.0 acres) and for industrial development EPA assumes an average site size of
4.5 acres (the average of 6.0 and 3.0 acres).
liable 4-17. Typical Building Sizes and Size Ranges by Type of
Building
Building Category/Type
Commercial - Supermarkets
Commercial - Department
Store
Commercial - Low-Rise Office
Commercial - Mid-Rise Office
Commercial - Elementary2
Industrial - Warehouse
Typical Size
(Gross Square
Feet)
20,000
90,000
8,600
52,000
41,000
25,000
Typical Range
(Gross Square Feet)
Low
12,000
44,000
4,700
31,300
24,500
8,000
High
30,000
122,000
19,000
83,100
55,000
72,000
a. For purposes of this analysis EPA combines a number of building types, including
educational, under the commercial category.
Source: R.S. Means, 2000. • '
The resulting average project sizes were then multiplied by the estimated number of commercial
and industrial permits to obtain an estimate of the total acreage developed (and thus land acreage
disturbed) for these project categories. Table 4-18 shows the results of this "bottom-up"
approach to estimating the number of acres of land developed. The overall estimate of the
amount of land developed is 2.01 million acres per year. Residential single-family development
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accounts for 24.4 percent of the total, multifamily development for 11.5 percent of the total,
commercial for 61.4 percent, and industrial for 2.7 percent.
Table 4-18. National Estimates of Land Area Developed Per Year,
Based on Building Permit Data
Type of Construction
Residential
Nonresidential
Single-family
Multifamily
Commercial11
Industrial
Total
Permits
Number
1,043,045
35,672
254,566
12,140
1,345,423
Pet. of
Total
77.5%
2.7%
18.9%.
0.9%
100.0%
Average
Site Size"
0.47
6.5
4.9
4.5
--
Acres Disturbed
Number
490,231
231,868
1,234,645
54,630
2,011,374
Pet. of total
24.4%
11.5%
61.4%
2.7%
100.0%
a. For single-family residential, this is the average of the average lot size for new construction in 1999
(BOC, 2000b) and the average obtained in EPA (1999). For all other categories, the site sizes are EPA
assumptions based on representative project profiles contained in R.S. Means (2000) and the 14-
community survey conducted in support of the Phase IINPDES storm water rule (EPA, 1999).
b. A number of project types were grouped together to form the "commercial" category, including:
hotels/motels, amusement, religious, parking garages, service stations, hospitals, offices, public works,
educational, stores, other nonresidential buildings.
The estimate of 2.01 million acres (Table 4-18) of annual construction is close to the estimated
2.24 million acres of annual new urban land obtained from 1997 NRI. Areas not accounted for
in EPA's estimates include those converted as a result of road, highway, bridge, park, monument,
and other non-building construction projects. EPA has not developed engineering costs
applicable to these types of projects, but assumes that the builders and developers of these areas
will face similar compliance costs per acre to the residential, commercial and industrial sectors,
and therefore, the acreage should be included in EPA's analysis. For the purpose of developing
national compliance costs, therefore, EPA has allocated the entire annual new urban acreage
from the 1997 NRI into the four land use categories using the distribution shown in the final
column of Table 4-18. The third column in Table 4-19 summarizes the results of this allocation.
EPA next adjusted the annual developed acreage to account for sites that would not be required
to obtain a permit due to the low rainfall erosivity waiver contained in the Phase II rule, as well
as to eliminate sites less than 1 acre. EPA estimated based on the Phase II economic analysis
that 33,517 acres would qualify for a low soil loss waiver, and analysis of the 14 community
survey data indicates that 33,828 acres would be in sites less than 1 acre. This yields 67,345
acres of annual new development that would not be within the scope of the proposal. EPA
allocated this acreage among the four land uses based on an analysis of the number of permits
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less than five acres contained within each respective segment.. The results of this allocation are
contained in the fourth column of Table 4-19, and the revised NRI acreage accounting for
waivers and sites less than 1 acre is presented in the last column Table 4-19. EPA further
estimated acreage that would be eliminated from coverage given the 5 acre cutoff contained in
Option 2. A discussion of this analysis is included in the Economic Analysis supporting
document.
Table 4-19. National Estimates of Land Area Disturbed Based on
National Resources Inventory Totals
Type of Construction
Residential
Nonresidential
Single-
family
Multifamily
Commercial0
Industrial
Total
Total NRI
Acreage"
546,783
258,616
1,377,070
60,932
2,243,400
Acres Waived or
not Covered
12,905
6,434
44,594
3,412
67,345
Adjusted NRI
Acreage1"
533,878
252,182
1,332,476
57,523
2,176,058
a. This column distributes the total acreage estimated in NRI to be converted on an
annual basis (adjusted for waivers) according to the distribution by type of development
estimated through analysis of permits data contained in Table 4-18.
b. This column presents the total national acreage estimated after adjusting for rainfall
erosivity waivers and sites less than 1 acre.
c. A number of project types .were grouped together to form the "commercial" category,
including: hotels/motels, amusement, religious, parking garages, service stations,
hospitals, offices, public works, educational, stores, other nonresidential buildings.
4.3.2.3 Distribution of Developed Acreage by Project Size and Geography
For each of the four land use categories in Table 4-19, EPA developed a distribution to allocate
developed acre estimates among six different project size categories. The project size
distribution is based on a survey of construction permits issued in 14 communities conducted in
support of the Phase II storm water rule. Table 4-20 shows the distribution of the 14 community
survey data by project size for each land use category. The percentages shown in Table 4-20 •
were used to allocate the total estimated development within each of the four land use sectors in.
Table 4-19 into six site size categories. The results of this analysis are presented in Table 4-21.
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In addition, EPA developed procedures to spatially distribute land development regionally, using
19 eccregions covering the contiguous states. A description of this methodology is presented in
the Environmental Assessment supporting document.
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Table 4-20. Distribution of 14 Community Survey
Permits by Site Size
Site Size (Acres)
No. of
Permits
Acres by Size
Pet. Acres by Size
Single-Family Residential
1
3
7.5
25
70
200
Total
266
228
138
175
30
15
852
Multifamily Residential
1
3
7.5
25
70
200
Total
43
100
61
71
10
1
286
Commercial
1
3
7.5
25
70
200
Total
266
356
86
91
16
0
815
266
684
1,035
4,375
2,100
3,000
• 11,460
43
300
458
1,775
700
200
3,476
266
"1,068
. 645
2,275
1,260
0
5,514
2.3%
6.0%
9.0%
38.2%
18.3%
26.2%
100.0%
1.2%
8.6%
13.2%
'51.1%
20.1%
5.8%
100.0%
- 4.8%
19.4%
11.7%
41.3%
22.9%
0.0%
100.0%
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Table 4-20. Distribution of 14 Community Survey
Permits by Site Size
Site Size (Acres)
No. of
Permits
Acres by Size
Pet. Acres by Size
Industrial
1
'3
7.5
25
70
200
Total
39
55
10
8
3
0
115
39
165
75
200
210
0
689
5.7%
23.9%
10.9%
29.0%
30.5%
0.0%
100.0%
Total
1
3
7.5
25
70
200
Total
614
739
295'
345
59
16
2,068
614
2,217
2,213
8,625
4,270
3,200
21,139
2.9%
10.5%
10.5%
40.8%
20.2%
15.1%
100.0%
Based on permitting data from the following municipalities or counties:
Austin, TX; Baltimore County, MD; Gary, NC; Ft. Collins, CO; Lacey,
WA; Loudoun County, VA; New Britain, CT; Olympia, WA; Prince
George's County, MD; Raleigh, NC; South Bend, IN; Tallahassee, FL;
Tucson, AZ; and Waukesha, WI.
Source: USEPA, 1999
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Table 4-21. Distribution of National Construction by Site
Size and Development Type
Site Size (Acres)
No. of
Permits
Acres by Size
Pet. Acres by Size
Single-Family Residential
1
3
7.5
25
70
200
Total
12,392
10,622
6,429
8,153
1,398
699
3.9,691
12,392
31,865
48,217
203,815
97,831
139,759
533,878
2.3%
6.0%
9.0%
38.2%
18.3%
26.2%
100.0%
Multifamily Residential
1
3
7.5
25
70
200
Total
Commercial
1
3
7.5
25
70
200
Total
3,120
7,256
4,426
5,152
726
73
20,752
64,280 .
86,029
20,782
21,990
4,350
0
197,431
3,120
21,768
33,196
128,794
50,792
14,512
252,182
64,280
258,086
155,866
,549,761
304,483
0
1,332,476
1.2%
8.6%
13.2%
51.1%
20.1%
5.8%
100.0%
4.8%
19.4%
11.7%
. 41.3%
22.9%
0.0%
100.0%
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Table 4-21. Distribution of National Construction by Site
Size and Development Type
Site Size (Acres)
No. of
Permits
Industrial
1
3
7.5
25
70
200
Total
Totals
1
3
7.5
25
70
200
Grand Total
3,256
4,592
835
668
250
0
9,601
83,048
108,498
32,472
35,963
6,723
771
267,475
•Acres by Size
3,256
13,775
6,262
16,698
17,532
0
57,523
83,048
325,494
243,541
899,067
470,638
154,271
2,176,059
Pet. Acres by Size
5.7%
23.9%
10.9%
29.0%
30.5%
0.0%
100.0%
3.8%
15.0%
1-1.2%
41.3%
21.6%
7.1%
100.0%
Based on permitting data from the following municipalities or counties: Austin,
TX; Baltimore County, MD; Gary, NC; Ft. Collins, CO; Lacey, WA; Loudoun
County, VA; New Britain, CT; Olympia, WA; Prince George's County, MD;
Raleigh, NC; South Bend, IN; Tallahassee, FL; Tuscon, AZ; and Waukesha, WI.
Source: USEPA, 1999.
4.4 REFERENCES
BOC. 1992a. 1992 Census of Construction Industries: Highway and Street Construction
Contractors, Except Elevated Highways. U.S. Bureau of the Census, Washington, DC.
http://www.census.gOV/prod/l/constr/92ind/cci06f.pdf. Accessed May 21, 2002.
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BOC. 1992b. 1992 Census of Construction Industries: Bridge, Tunnel and Elevated Highway
Construction Contractors. U.S. Bureau of the Census, Washington, DC.
http://www.census.gOV/prod/l/constr/92ind/cci07f.pdf. Accessed May 21, 2002.
BOC. 1992c. 1992 Census of Construction Industries: Water, Sewer, Pipeline and
Communications andPowerline Construction. U.S. Bureau of the Census, Washington,
DC. http://www.census.gOV/prod/l/constry92ind/cci08f.pdf. Accessed May 21, 2002.
BOC. 1995. Characteristics of New Housing: 1995, Current Construction Reports. U.S. Bureau
of the Census, Washington, DC. http://www.census.gov/prod/l/constr/c25/c25_95a.pdf.
Accessed May 28, 2002.
BOC. 1996. Characteristics of New Housing: 1996, Current Construction Reports. U.S. Bureau
of the Census, Washington, DC. http://www.census.gOV/prod/l/constr/c25/c25-96a.pdf.
Accessed May 28, 2002.
BOC. 1997. Characteristics of New Housing: 1997, Current Construction Reports. U.S. Bureau
of the Census, Washington, DC. http://www.census.gOV/prod/3/98pubs/c25-97a.pdf.
Accessed May 28, 2002.
BOC. 1999a. Housing Starts, Current Construction Reports. U.S. Bureau of the Census,
Washington, DC. http://www.census.gov/prod/99pubs/c20-9901.pdf. Accessed October
1,2000.
BOC. 1999b. Single-family Housing Construction, 1997 Economic Census,
Construction Industry Series. U.S. Bureau of the Census, Washington, DC.
http://www.census.gov/prod/ec97/97c2332a.pdf! Accessed October 2, 2000.
BOC. 1999c. Multifamily Housing Construction, 1997 Economic Census, Construction Industry
Series. U.S. Bureau of the Census, Washington, DC.
http://www.census.gov/prod/ec97/97c2332b.pdf. Accessed October 15, 2000.
BOC. 1999d. Commercial and Institutional Building Construction, 1997 Economic Census,
Construction Industry Series. U.S. Bureau of the Census, Washington, DC.
http://www.census.gov/prod/ec97/97c2333b.pdf. Accessed October 25, 2000.
BOC. 1999e. Manufacturing and Industrial Building Construction, 1997 Economic Census,
Construction Industry Series. U.S. Bureau of the Census, Washington, DC.
http://www.census.gov/prod/ec97/97c2333a.pdf. Accessed October 25, 2000.
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BOC. 1999f. Water, Sewer, Pipeline Construction, 1997 Economic Census, Construction
Industry Series. U.S. Bureau of the Census, Washington, DC.
http://www.census.gov/prod/ec97/97c2349a.pdf. Accessed October 25, 2000.
BOC. 1999g. Highway and Street Construction Contractors. U.S. Bureau of the Census,
Washington, DC. http://www.census.gov/prod/ec97/97c2341a.pdf. Accessed October 25,
' 2000.
BOC. 1999h. Bridge and Tunnel Construction. U.S. Bureau of the Census, Washington, DC.
http://www.census.gov/prod/ec97/97c2341b.pdf. Accessed October 25, 2000.
BOC. 2000a. 1997 Economic Census-construction Sector Special Study: Housing Start
Statistics, a Profile of the Homebuilding Industry. Issued July 2000. U.S. Bureau of the
Census, Washington, DC.
BOC. 2000b. New Privately Owned Housing Units Authorized by Building Permits in Permit-
issuing Places, Annual Data. U.S. Bureau of the Census, Washington, DC.
BOC. 2001. New Privately Owned Housing Units Started: Annual Data, 2001. U.S. Bureau of
the Census, Washington, DC. http://www.census.gov/const/startsan.pdf. Accessed May
23,2002.
Caterpillar. 2000. Caterpillar, Inc. http://www.cat.com
Construction Equipment On-line. 2000. Reed Business Information, U.S. www.coneq.com
CWP. 2001. Impervious Cover and Land Use in the Chesapeake Bay Watershed. Ellicott City,
MD: Center for Watershed Protection, January. Additional data table, "Chesapeake bay
watershed impervious cover results by land use polygon," received via a facsimile from
Tetra Tech, Inc., September 20, 2001.
Lynch, Kevin and Hack, Gary. 1984. Site Planning (3rd ed.). Cambridge, MA: MIT Press.
NAHB. 2002. Characteristics of New Multifamily Buildings 1987-1999. National Association
of Home Builders, http://www.nahb.com/multifamily/characteristics.htm. Accessed May
29,2001.
NAICS. 1997. North American Industry Classification System-U.S. U.S. Department of
Commerce, National Technical Information Service, Washington, DC.
Peurifoy, Robert L. and Oberlender, Garold D. (198.9). Estimating Construction Costs (4th ed.).
New York: McGraw Hill Book Company.
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R.S. Means. 2000. Building Construction Cost Data 58th Annual Edition. R.S. Means Co.,
Kingston, Massachusetts.
R.S. Means. 2001. Heavy Construction Cost Data 15th Annual Edition. R.S. Means Co.,
Kingston, Massachusetts.
USDA. 2000.1997 National Resources Inventory. U.S. Department of Agriculture, National
Resources Conservation Service, Washington, DC. www.nrcs.usda.gov/technical/NRI/.
USEPA. 1999. Economic Analysis of the Final Phase II Storm Water Rule. U.S. Environmental
Protection Agency, Office of Wastewater Management. Washington, DC.
U.S. Housing Markets. 1998. Homebuilders Face a Steep Climb Chasing a 20-year-old-famify
Mark. Meyers Real Estate Information, Inc.
htt]j://www.housingusa.com/ushm/pr/ushm998.pr.html. Accessed October 25, 2000.
U.S. Housing Markets. 1999a. Busiest Markets, Single-family Building. Meyers Real Estate
Information, Inc.
http://www.housingusa.com/ushm/pmts/mulbuzz.html. Accessed October 25, 2000.
U.S. Housing Markets. 1999b. Busiest Markets, Multifamily Construction. Meyers Real Estate
Information, Inc.
http://www.housingusa.com/ushm/pmts/mulbuzz.html Accessed October 25, 2000.
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SECTION 5: TECHNOLOGY ASSESSMENT
This'technology assessment of available data sources is intended to determine the depth and
breadth of effectiveness data for various erosion and sediment controls, and to identify the
amount and quality of data available to describe the performance of all currently used and
innovative runoff control practices, the ability of each practice to effectively control impacts due
to runoff, and the design criteria or standards currently used to size each practice to ensure
effective control of runoff.
5.1 CONSTRUCTION EROSION AND SEDIMENT CONTROLS
5.1.1 INTRODUCTION
Part 1, reported in this sub-section, addresses the erosion and sediment control BMPs for the
construction phase of development. Prior to initiating this aspect of the work, EPA reviewed the
findings of information sources and literature assessments to identify the appropriate definition
of "performance" or the various definitions or "levels" of performance that are considered in
evaluating and defining the levels of performance for these BMPs. A scientific-based approach
to describe the performance of erosion and sediment control BMPs was devised similar to the
approach developed by Barfield and Clar (1985) in the evaluation of the Maryland Erosion and
Sediment Control Standards, as well as the one recently developed in the American Society of
Civil Engineers BMP Database (ASCE, 1999). The approach used in this assessment has been
designed to provide the information needed to address several important issues, including
whether to use a design-based approach, or an effluent-based concentration, or a loading
approach in reporting on the current status of the technology. This sub-section identifies the
following:
• The amount and quantity of data available to describe the performance of all currently used
and innovative runoff control practices.
• The ability of each practice to effectively control impacts due to runoff.
• The design criteria or standards currently used to size each practice to ensure effective
control of runoff.
Before a detailed evaluation of the BMPs can be provided, some background information is
necessary. Sub-section 5.2 describes the procedure for assessing the technology. Sub-section
5.3 provides a historical background on the subject. Next, sub-section 5.4 presents a discussion
of goals, control strategies, criteria, and standards in general, and sub-section 5.5 provides a
detailed description and discussion of each BMP.
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In the discussion of BMPs in sub-section 5.5, the major focus will be on sediment. This does not
imply that there are no other impacts; however, construction BMPs have focused on erosion aiad
sediment control rather than on other impacts.
In the assessment of BMPs> considerable attention is focused on whether to use a design-based
approach, an effluent-based concentration, or a loading approach in reporting on the current
status of the technology. Attention is also given to the recent emphasis in the literature on the
use of an integrated approach to evaluate impacts to the receiving waters and downstream areas.
5.1.2 PROCEDURE FOR TECHNOLOGY ASSESSMENT
5.1.2.1 IDENTIFICATION OF PERFORMANCE GOALS
In assessing the literature, particular consideration was given to definitions of performance of
BMPs and how they addressed the range of receiving water impacts identified. It is important to
point out that the overarching performance goal of all the BMPs is to minimize the impact of
construction site runoff on receiving waters and downstream areas.
Control strategies that have been identified for construction BMPs can be divided into three
categories.
Strategy 1. Control Based on Design Standards—-Control at this level is based on standard
designs that may include such things as volume requirements for reservoirs, detention time, and
trapping efficiency that do not directly limit an allowable discharge to receiving waters or limit a
downstream impact.
Strategy 2. Control Based on Effluent Standards—Control at this level is based on limiting the
quantity of one or more substances such as peak discharge, runoff volume, TSS, and settleable
solids. This directly addresses effluent, but does not directly address downstream impacts.
Strategy 3. Control Based on an Integrated Approach—Control at this level uses an integrated
approach (Snodgrass et al., 1998), including biological, chemical, and physical criteria, to define
BMP performance. A combination of water quality, biohabitat, and geomorphic criteria is used
to evaluate .whether a receiving stream is at the targeted goal pf fishable and swimmable, or the
extent of departure from this goal.
The majority of BMPs address Strategies. 1 or 2. Although Strategy 3 is being discussed in the
literature, it has not been adopted in practice. There is an analog in the surface mining industry,
where a cumulative hydrologic impact analysis on a watershed basis is required by the U.S.
Surface Mining and Reclamation Act of 1977 (PL95-87). When moving from Strategy 2 to
Strategy 3, a number of other parameters are added to the performance criteria in Strategy 2,
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including (1) stream buffer retention and thermal impacts considerations, (2) volume control
considerations such as are presented in the Low Impact Development concept approach, which
are added to the peak discharge and ground water recharge criteria to achieve maintenance of
hydrologic function at a site-specific level, and (3) geomorphic criteria as described by Lane
(1955), Leopold et al. (1964), Rosgen (1996), and others.
An important point must be made about controlling sediment. From a practical standpoint, a
reasonably sized structure should not necessarily be expected to meet an effluent TSS standard
unless the TSS specified in the standard is set at a very high value or unless some form of
chemical treatment is used to enhance flpcculatidn. The settling velocity for primary clay
particles is in the range of feet per month for all but the largest particles. Since these size
particles are frequently encountered in large percentages in sediment from construction sites, the
expected trapping efficiencies will not approach 100 percent, nor will the effluent TSS be hi the
range of 100 mg/L or lower (Haan et al., 1994).
5.1.2.2
GOALS, ENVIRONMENTAL IMPACT AREAS, AND ASSESSMENT
SCALES
For the purposes of this report, impact areas are divided into three categories, local area,
receiving water, and downstream areas.
Local Area. This is the area between the construction site and the receiving stream. Typically,
these areas have ephemeral streams with low baseflows and highly variable flow rates, hi these
areas, the flows fluctuate widely, with geomorphology and habitat being very susceptible to
changes in hydrologic regime (Klaine, 2000). hi some developments, there would essentially be
no local area, and flows would exit directly into receiving waters.
Receiving Waters. This is the point at which flows enter a well-defined stream. Depending on
the local geology, flows may primarily be ephemeral, there may be a well-established baseflow,
or there may be something intermediate between the two extremes. The degree to which flows,
sediment, and chemicals impact the receiving waters depends largely on the type of receiving
water. For example, if the receiving waters have a low baseflow and highly variable flow rates,
the habitat and geomorphology will be very sensitive to significant changes in the hydrologic
regime. However, if the receiving waters have a high baseflow, the sensitivity to changes in .
flow rate will be much less and the primary problems will likely be chemical in nature. Thus, it
is important to address impacts on a site-specific basis.
Downstream Areas. A definition of the downstream area can be somewhat nebulous. (A
definition of the aerial extent of "downstream areas" is something that needs to be developed in
follow-up studies.) However, consideration of this area is important. For example, use of peak
discharge criteria may directly control the local area impacts and impacts to the point at which
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flow enters the receiving waters. If the watershed being considered is combined with other
downstream watersheds and all use peak discharge control without controlling runoff volume,
there can be an increase in flooding due to superposition of long duration peak flows exiting the
numerous reservoirs (Smiley and Haan, 1976). This increased discharge can negatively impact
channel geomorphology, habitat, and riparian areas.
Another important issue related to construction is the fraction of the watershed under
construction at any one time. One argument about the relative importance of the construction
phase versus the post-construction phase is that the construction phase is short-lived and the
impact may be reversible after the site has stabilized. While this argument may have some
validity on the local area, it is invalid when considering the downstream areas. On a larger
watershed under development, major construction may occur in the watershed for a long time,
with a potential long-term major cumulative impact. When considering the entire watershed, it
may be desirable to limit the area under construction at any one time to prevent exceeding some
threshold that would result in an irreversible impact. This indicates the need to conduct a
cumulative impact analysis on a river basin scale to evaluate the potential for such an impact to
occur. . •
When considering area impacts, the following comments can be made about the strategies listed
above.
Strategy 1. No guarantees can be made that impacts would be controlled at any level unless the
design standards are highly conservative. This would result in overdesign for most situations so
that the standard would be adequate for all situations.
Strategy 2. This strategy should ensure control at the local level. Downstream, the impacts may
be positive or negative as a result of the control. Examples include the control of peak discharge
only in storm water runoff. Control of peak discharge on all construction areas at the local level
can result in increased peak discharge downstream (Smiley and Haan, 1976). These increases
result from detaining increased volumes of runoff resulting from urbanization and releasing them
at the predisturbed peak rate over a long period of time. ,
Strategy 3. This approach should ensure control in both the local area and downstream areas.
Scale is very important to BMP effectiveness analyses. A given BMP may be quite effective in
controlling impacts nearby but have a significant negative impact when applied over a large area.
In the final analysis, effectiveness should be evaluated at multiple scales before a decision is
made. This will require both local and watershed level analyses. .
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5.1.2.3
QUALITATIVE VERSUS QUANTITATIVE ASSESSMENT
In the assessments, the issue may be addressed on a qualitative or a quantitative basis. The
difference can be explained in the following manner, using water temperature as an example. It
is well known that turbidity impacts the depth of penetration of solar energy into a waterbody;
hence, turbidity impacts temperature. When evaluating the impact of standards on water
temperature, it is obvious that a TSS standard directly addresses water temperature because of
the impact of TSS on turbidity. Thus, a qualitative analysis would simply state that TSS
standards may impact water temperature, but give no degree to which the standard does impact
temperature. A quantitative analysis, however, would define the degree to which a given TSS
standard increased or decreased the impact of storm water TSS on temperature.
5.1.3 REVIEW OF HISTORICAL APPROACHES TO EROSION AND SEDIMENT
CONTROL
Most early sediment control was related to agriculture and was installed as a way to maintain our
natural resource base. On-site control was the primary emphasis, attempting to prevent erosion
rather than trap sediment. Strategies were developed to minimize exposure of bare soil to the
erosive power of rainfall and runoff, using aboveground cover management, residue
management, strip cropping, and terracing to limit the length of overland flow. Impacts to
receiving streams and downstream areas had not yet been identified as an issue, hi the 1960s,
concern began to be expressed about the quantities of sediment in streams and reservoirs, and
sediment was first identified as a pollutant Initially, the major focus of sediment control was on
the surface mining industry, with the passage of the Clean Water Act and then the Surface
Mining, Reclamation, and Control Act (SMRCA) (PL 95-87) (U.S. Congress, 1977). The first '
approach taken to sediment control was a design standard, requiring a sediment detention basin
with a 24-hour detention time; TSS standards of 35 mg/L average and 70 mg/L peak were also
promulgated, but were not typically enforced. The U.S. Environmental Protection Agency
(USEPA) later evaluated the TSS standard and moved to a settleable solids standard of 0.5 ml/L,
based on a modeling effort that showed that it was not possible to trap fine sediments, but that a
0.5 ml/L settleable solids standard could be met with a reasonably sized sediment basin (Ettinger
and Lichty, 1979).
hi the late 1960s and early 1970s, sediment in streams and waterways originating from urban
construction sites became an issue, which was then addressed in the Clean Water Act. EPA
developed a list of BMPs and standards for their construction. (USEPA, 1971). In general, these
standards were adopted from those of other agencies and were not based on studies related to
urban runoff.
hi 1987, the Clean Water Act was amended to include storm water discharges from urban areas.
The Phase INPDES Stormwater regulations were published in 1990, requiring all municipalities
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with Municipal Separate Storm Sewer System (MS4) serving populations over 100,000,
construction sites 5 acres and larger, and certain industrial sites to obtain a permit. The permit
required the development of a stormwater pollution prevention plan (SWPPP) that typically
included a storm water and sediment control plan. In 1999, the Phase IINPDES stormwater
regulations were published, extending permit coverage to construction sites of 1 acre or larger
and municipalities to 50,000 or 10,000 population if the density is more than 1,000 per square
mile. The regulations allow use of general permits in lieu of individual site or facility permits.
The degree of oversight of construction varies widely among the states.
In the last two decades, increased concern at the local level has been focused on sediment
pollution of streams and waterways, particularly originating from construction, while less
concern has been focused on the impacts of increased construction on storm water and chemical
production. Much of this government concern originated from the Phase I and Phase II NPDES
stormwater regulations. A number of states and their local agencies have developed standards
and BMPs for sediment control, most of which do not have a scientific basis, but were adopted
from other agencies. Some states, however, did conduct studies that gave their standards some
scientific basis. For example, Maryland evaluated its BMP standards in the 1980s by using
modeling techniques and the state changed its sediment basin standards to account for the
impacts of surface area on the trapping efficiency in sediment ponds. Based on typical soils in
the region and modeling studies, the state adopted a surface area to peak discharge ratio of 0.01
cfs/acre as a criterion (Barfield and Clar, 1985; McBurnie, 1990). Maryland was thus the first
state to use a design criterion that was related to the overflow rate. Other states also used some
of Maryland's results (Smolen et al, 1988).
Recent efforts have moved closer to an effluent standard approach. South Carolina conducted a
detailed analysis and published regulations that required a trapping efficiency or settleable solids
standard (SCDHEC, 1995). In addition, results from a detailed model were used to develop
simplified design aids (Hayes and Barfield, 1995; Holbrook et al., 1998). Some municipalities
are following suit to develop scientifically based standards of their own. For example, in 1998
Louisville, Kentucky (Hayes et al., 2001) developed standards and design aids for their storm
water and sediment control, following the example of South Carolina.
There are no analogs in which the integrated approach to storm water and sediment control have
been used on construction sites. The closest analog is the Cumulative Hydrologic Impact
Analysis (CHIA) required in surface mining by the SMRCA. SMRCA requires each applicant
for a surface mining permit to conduct a hydrologic impact analysis. Subsequently, the
regulatory authority is required to conduct a CHIA for the entire watershed. It should be pointed
out that although a CHIA is required, it is seldom undertaken on a scale that is useful.
Many of the advances in sediment control have been based on the capability to predict, a priori.,
the ability of a given design to meet a standard. For example, when the settleable solids standard
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was developed for surface mining, most regulatory authorities adopted it, with the requirement
that permit applicants would demonstrate through the use of widely accepted computer models,
that the proposed design would meet the settleable solids standard.
Most of the early work in modeling sediment production stemmed from efforts in the 1950s to
develop a soil loss equation that would apply to the entire nation and allow evaluation of
alternative erosion control practices. This led to the relationship known as the Universal Soil
Loss Equation (USLE) (Wischmeier and Smith, 1965) and its .subsequent derivative, the Revised
USLE (RUSLE) (Renard et al, 1994). These efforts focus on erosion control; thus, the
relationships do not predict sediment yield. A flurry of efforts were addressed in the late 1970s
and early 1980s leading to the development of sediment yield relationships such as yielding the
Modified USLE (MUSLE) by Williams (Williams, No Date), the CREAMS model (Knisel
1980), and SEDIMOt II (Wilson et al., 1982), and its derivatives. The MUSLE and CREAMS
models did not include methods to evaluate the impact of sediment trapping structures, but
SEDIMOT H contained relationships developed at the University of Kentucky to predict the
impact of reservoirs (Ward et al., 1977; Wilson et al, 1984), check dams (Hirschi, 1981), and
vegetative filter strips (Hayes et al, 1984). The MUSLE and SEDIMOT II models were based
on single storms while the CREAMS model was based on continuous simulation modeling.
Details on these models can be found in Haanetal. (1994). . .
More recently, modeling has improved, resulting in several new relationships. The WEPP
watershed model is one example of a continuous simulation approach. It includes computational
procedures for a wide variety of sediment control structures (Lindley et al, 1998). Another
example of a single storm-based model is SEDIMOT HI (Barfield et al, 1996), which modifies
the earlier SEDIMOT II model to include channel erosion routines and a wide variety of
sediment control techniques. A significant drawback in the SEDIMOT m and WEPP models is
that they do not have a good technique for predicting the impact of filter fence, which is the most
common technique used today for sediment control.
Concerns for changes in geomorphology resulting from flow changes have resulted in several
modeling approaches. Early efforts were focused on what is known as the regime theory, in
which changes in channel property are linked, qualitatively, to changes in flow. Examples
include models of Lane (1955) and Schumm (1977). In addition, some statistically based
models were developed, but they are not universally applicable (Blench, 1970; Simons and
Albertson, 1960). More recently, models have been developed using physically based concepts
to predict changes in geomorphology as related to changes in flow. The models of Chang (1988)
are good examples. It is possible to predict, to a limited extent, the change in channel properties
as impacted by changes in flow.
The impact of changes in flow and geomorphology on habitat is one major area where
information is lacking. Although this deficiency can be addressed in a qualitative manner, it is
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not possible to predict quantitatively how a given change in geomorphology will impact habitat.
Additional information is needed to develop a strategy based on the integrated assessment
approach.
5.1.4 GOALS, CONTROL STRATEGIES, CRITERIA, AND STANDARDS
5.1.4.1 GOALS, CONTROL STRATEGIES, CRITERIA, AND STANDARDS:
HOW THEY RELATE
The relationship between goals, control strategies, criteria, and standards can sometimes be
confusing. For the purposes of the discussion on construction BMPs, the following definitions
will be used.
Goal. The overarching objective of having a storm water, sediment, and pollution control
program is known as the goal. It is what the program is trying to achieve. All BMPs should
relate to that goal. As stated earlier, the goal of this program is to minimize the impact of
construction on receiving water and downstream areas. The impacts of concern are identified in
the Environmental Assessment.
Control Strategies. The methods by which the regulatory agency tries to achieve the goal are
called control strategies.
Criteria. The particular variables that are targeted by a given strategy are known as the criteria.
For example, if the strategy is to control impacts by limiting the discharge of sediment generated
to the receiving waters, then sediment becomes the criterion. ;
Standard. The specific variable chosen for the criteria and its numeric value is referred to as the
standard. For example, if the control strategy is to limit sediment discharge to the receiving
waters, the criterion is sediment, and the particular limiting variable and numeric value chosen is
a peak settleable solids concentration of 0.5 mg/L, then the standard would be a peak settleable
solids concentration of 0.5 mg/L.
The relationship among goals, control strategies, criteria, and standards is shown graphically in
Figure 5-1.
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Criteria 1
Flow Variables*
Sediment Variables*
Geomorphology.
Criteria 2
To Be
Developed
Figure 5-1. Flow Diagram Showing Relationship Among Goals, Strategies, Criteria, and Standards
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5.1.4.2
LEVELS OF PERFORMANCE OR "HOW WELL DO THE
STRATEGIES WORK?"
Table 5-1 provides a description on the level of performance for the three strategies discussed in
sub-section 5.2.1.
Table 5-1. Description of Levels of Performance of Three Control Strategies
Level
0
1
2
3
4
5
Description of Performance
No consideration of impact.
Performance defined by a design standard. No guarantee that the design will control the impact to a
desired level on the specific watershed. Example: reservoir volume standard for runoff control.
Effluent standard based on controlling a single entity entering receiving waters. Control of the single
parameter will not guarantee that the desired protection will occur for receiving waters or
downstream impact. Example: controlling peak storm water discharge or peak TSS.
Effluent standard based on controlling two or more entities entering receiving waters, but not all
entities causing environmental impact. Example: controlling peak discharge and sediment, but not
storage volume or runoff volume.
Effluent standards for all entities entering receiving waters and causing environmental impact. Even
Qontrolling all quantities entering receiving waters will not guarantee that there are no undesired
downstream impacts. Example: Controlling runoff rate, runoff volume, peak discharge, and TSS in
receiving streams does not guarantee that there will be no undesirable biological impacts. i
Control based on integrated evaluation of impacts on receiving stream and downstream.
5.1.4.3 STRATEGIES, CRITERIA, STANDARDS, AND ENFORCEMENT
The effectiveness of a given strategy, criterion, or standard is directly related to the ability of an
enforcement agency to enforce the rules. Thus, a given standard may theoretically provide
excellent protection to the environment, but be so difficult to enforce that it is less effective than.
a less stringent standard that is enforceable. In general, the difficulty in enforcement increases as
the level of desired performance increases. An estimate of relative difficulty in enforcement is
given in Table 5-2 for the various levels of performance from Table 5-1. For example, it is
easiest to enforce the design standard, since enforcement is based entirely on reviewing plans
and inspection of the site to ensure that the plans are put into action properly.
Important issues related to enforcement include the following:
• A priori demonstration by the best computational technology that the proposed design can
meet the standard.
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En
• As-built inspections to verify that the installed practices match the approved plan.
• Self-monitoring of effluent in the case of effluent standards, with spot checks by the
regulatory authority to make sure that evaluations are being done properly.
• Evaluation of downstream impacts.
• Clearly defined rules for monitoring the effectiveness of a practice.
Table 5-2. Descriptions of Levels of Difficulty in Enforcement
Level of
Performance
from Table 1-1
0
1
2
3
4
5
Difficulty in
Enforcing
(Relative)
0
1
2
2.5
2.5
5
Description of Difficulty
Nothing to enforce.
Enforcement consists of reviewing plans and ensuring proper installation
and maintenance.
Enforcement requires some monitoring and typically requires a
preconstruction review of plans and submission of calculations showing
that the standard can be met.
Same as above except multiple variables.
Same as above.
Enforcement required some a priori demonstration of the expected flow
and concentration changes and their impact of the receiving waters and
downstream variables. In addition, routine monitoring of downstream
variables such as geomorphology, aquatic life, aesthetics, and riparian
zones would be required.
A Priori Demonstration of Performance:
A priori demonstration that a given design can meet the standard is very important. Experience
with the surface mining industry indicates that a sediment control plan is no better than its
design. If the best computational technology indicates that the design will not meet the standard,
then field monitoring of the BMP is not likely to show that the, standards are being achieved.
Thus, it will be important to have scientifically based and verified computational technologies to
predict the performance of BMPs relative to meeting a specified standard. '<
In recognition of this need the USEPA funded the development of the National Stormwater BMP
Database project by the Urban Water Resources Research Council of the American Society of
Civil Engineers (ASCE, 1999) in order to establish the state of the art of BMP performance with
respect to pollutant removal and peak discharge control (level 3). The database can be found at:
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http://www.bmpdatabase.org/. The ASCE project team prepared a report that contains several
different methods of evaluating BMP efficiency data. This report presents statistically based
approaches that involve conducting a statistical analysis to characterize inflow and outflow
EMCs, and then evaluates whether or not there is a statistically significant difference between
the two. The application of this approach in evaluating the data contained in the database has led
the study team to conclude that evaluating effluent quality is a good indicator of performance of
BMPs with respect to pollutant removal. A brief summary of the approach is provided in
Appendix A.
As-built Inspections
Another important issue related to enforcement is as-built inspections of installed practices. •
Although the rules may call for certification by an appropriately licensed professional, it is
important that the regulatory authority conduct routine inspections to ensure that the licensed
professionals are doing their job properly.
Monitoring
Finally, there are issues related to self-monitoring versus monitoring conducted by the regulatory
authority. The use of effluent standards would require some type of monitoring to ensure that
performance meets the standards. However, storm water and sediment control structures that
control flows are highly variable and temporally stochastic. This means that it is not possible to
plan ahead when the monitoring will occur. It will be necessary to have trained professionals to
conduct the monitoring.
A monitoring methodology for BMPs should meet three criteria: (1) provide scientifically based
numbers to evaluate effectiveness, (2) be executable and sufficiently simple to allow the use of
trained technicians who would reasonably be available to do the monitoring, and (3) be adequate
to ensure that the desired standards are met without excessive sampling or analysis. The,flrst
criterion could be met by providing clear documentation on the monitoring methodology that
specifies times, frequency, and location of sampling relative to storms, as well as clearly
articulated protocols for handling samples. The second criteria can be met by being sure that the
techniques proposed have actually been field applied by technicians in the monitoring business.
The third criterion can be evaluated by an error analysis that determines the expected accuracy of
measurement as a function of number and frequency of sampling.
Several possible criteria or standards have special measurement problems that should be
mentioned. These include criteria or standards based on trapping efficiency, and/or effluent TSS
and settleable solids (average or peak). The issues associated with these criteria are discussed
below.
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Trapping Efficiency. Literature citations frequently include studies that attempt to measure
trapping efficiency by sampling one or more inflow and outflow concentrations (Barrett et al.,
1995). While this simplicity seems attractive, it is a grossly erroneous measure of trapping
efficiency. A correct definition of trapping efficiency is given in Equation 1:
Equation 1:
where: Mi is inflow total mass
M0 is outflow total mass
Mt is given by integrating the product of inflow concentration and inflow
rate over the duration of a hydrograph
or
Equation 2:
'D
Mt = J
where: C; is inflow concentration
q} is inflow flow rate
t is time
tD is the duration of the storm.
Outflow total mass M0 is calculated by substituting the subscript o for i in Equation 2. Thus, to
monitor trapping efficiency correctly, it is necessary to measure both flow and concentration as a
function of time over the duration of both inflow and outflow. Such measurement is quite
difficult and time-consuming, requiring many samples.
Statistical Evaluation of Inflow/Outflow Data (mean, median, standard deviation,
coefficient of variance). To measure average or peak TSS, it is necessary to measure TSS in the
effluent over the duration of the outflow hydrograph as well as the flow rate. This requires that
multiple samples be taken and that the samples be centered around the peak discharge. The
ACSE database data analysis document has the ability, depending upon the number of samples
collected, to show a difference between various samples. Again, this is time-consuming and
difficult since the timing of an event and the timing of the peak discharge are not known a priori.
The average concentration is a weighted concentration, using flow rate as a weighting function.
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5.1.5
CONTROL TECHNIQUES, BMP SYSTEMS
5.1.5.1
EROSION CONTROL AND PREVENTION
5.1.5.1.1
PLANNING, STAGING, SCHEDULING
General Description
A construction sequence schedule is a specified work schedule that coordinates the timing of
land-disturbing activities and the installation of erosion and sediment control measures. The
goal of a construction sequence schedule is to reduce on-site erosion and off-site sedimentation'
by performing land-disturbing activities and installing erosion and sediment control practices in
accordance with a planned schedule (Smolen et al., 1988).
Construction site phasing involves disturbing only part of a site at a time to prevent erosion from
dormant parts (Claytor, 1997). Grading activities and construction are completed and soils are
effectively stabilized on one part of the site before grading and construction commence at
another part. This differs from the more traditional practice of construction site sequencing, in
which construction occurs at only one part of the site at the time, but site grading and other
site-disturbing activities typically occur simultaneously, leaving portions of the disturbed site
vulnerable to erosion. Construction site phasing must be incorporated into the overall site plan
early on. Elements to consider when phasing construction activities include the following
(Claytor, 1997):
• Managing runoff separately in each phase.
• Determining whether water and sewer connections and extensions can be accommodated.
• Determining the fate of already completed downhill phases.
• Providing separate construction and residential accesses to prevent conflicts between
residents living in completed stages of the site and construction equipment working on later
stages (USEPA, 2000).
Applicability
Construction sequencing can be used to plan earthwork and erosion and sediment control
activities at sites where land disturbances might affect water quality in a receiving waterbody.
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Design and Installation Criteria
Construction sequencing schedules should, at a minimum, include the following (NCDNR 1988'
MDE, 1994): '
• The erosion and sediment control practices that are to be installed
• The principal development activities
• The measures that should be installed before other activities are started -
• The compatibility with the general contract construction schedule
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Table 5-3 summarizes other important scheduling considerations in addition to those listed
above.
Table 5-3. Scheduling Considerations for Construction Activities
Construction Activity
Construction survey stakeout
Pre-construction meeting between owner,
contractor and regulatory agency
Construction access — entrance to site,
construction routes, areas designated for
equipment parking
Clearing and grading required for the
installation of controls •
Sediment traps and barriers — basin traps,
silt fences, outlet protection
Runoff control — diversions, perimeter
dikes, water bars, outlet protection
Runoff conveyance system— stabilize
streambanks, storm drains, channels, inlet
and outlet protection, slope drains
Land clearing and grading — site
preparation (cutting, filling, and grading;
sediment traps; barriers; diversions; drains;
surface roughening)
Surface stabilization— temporary and
permanent seeding, mulching, sodding,
riprap
Building construction — buildings, utilities,
paving
Landscaping and final
stabilization — adding top soil, trees, and
shrubs; permanent seeding; mulching;
sodding; riprap
Schedule Consideration
Prior to initiating any construction activity a construction survey stakeout
should be conducted. The stakeout should identify the limits of disturbance,
' and location of control structures, especially perimeter controls
This meeting should take place before any construction activity begins at the
site. The survey stakeout is reviewed, especially the limits of disturbance and
location of controls
This is the first land-disturbing activity. As soon as construction takes place,
stabilize any bare areas with gravel and temporary vegetation.
In conjunction with the construction access, the clearing and grading required
for the installation of E&S controls should take place.
After construction site has been accessed, install principal basins, with the
addition of more traps and barriers as needed during grading.
Install key practices after the installation of principal sediment traps and
before land grading. Additional runoff control measures may be installed
during grading.
If necessary, stabilize streambanks as soon as possible, and install principal
runoff conveyance system with runoff control measures. The remainder of
the svstems may be installed after grading. •
Implement major clearing and grading after installation of principal sediment
and key runoff control measures, and install additional control measures as
grading continues. Clear borrow and disposal areas as needed, and mark trees
and buffer areas for preservation.
Immediately apply temporary or permanent stabilizing measures to any
disturbed areas where work has been either completed or delayed.
During construction, install any erosion and sedimentation control measures
that are needed.
This is the last construction phase. Stabilize all open areas, including borrow
and spoil areas, and remove and stabilize all temporary control measures.
Effectiveness
Construction sequencing can be an effective tool for erosion and sediment control because it
ensures that management practices are installed where necessary and when appropriate. A
comparison of sediment loss from a typical development and from a comparable phased project
showed a 42 percent reduction in sediment export in the phased project (Claytor, 1997).
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Limitations
Weather and other unpredictable variables may affect construction sequence schedules. The
proposed schedule and a protocol for making changes resulting from unforseen problems should
be plainly stated in an applicable erosion and sediment control plan.
Maintenance
The construction sequence should be followed throughout the project, and the written erosion
and sediment control plan should be modified before any changes in construction activities are
executed. The plan can be updated if a site inspection indicates the need for additional erosion
and sediment control as determined by contractors, engineers, or developers.
Cost
Construction sequencing is a low-cost BMP because it requires a limited amount of a
contractor's time to provide a written plan for the coordination of construction activities and
management practices. Additional time might be needed to update the sequencing plan if the
current plan is not providing sufficient erosion and sediment control.
Although little research has been done to assess the costs of phasing versus conventional
construction costs, it is known that it will be to implement successful phasing for a larger project
(Claytor, 1997).
5.1.5.1.2
VEGETATIVE STABILIZATION
Vegetation can be used during construction to stabilize and protect soil exposed to the erosive
forces of water, as well as during post-construction to provide a filtration mechanism for storm
water runoff pollutants. The following discussion refers to vegetative stabilization as a
construction BMP that stabilizes and protects soil from erosion.
General Description
Vegetative stabilization measures employ plant material to protect soil exposed to the erosive
forces of water and wind. Selected vegetation can reduce erosion by more than 90 percent
(Fifield, 1999). Natural plant communities that are adapted to the site provide a self-maintaining
cover that is less expensive than structural alternatives. Plants provide erosion protection to
vulnerable surfaces by the following (Heyer, n.d.):
• Protecting soil surface from the impact of raindrops.
• Holding soil particles in place.
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• Maintaining the soil's capacity to absorb water.
• Using living root systems to hold soil in place, increasing overall bank stability.
• Directing flow velocity away from the streambank.
• Acting as a buffer against abrasive transported materials.
• Causing sediment deposition, which reduces sediment load and reestablishes the streambank.
The designer should be aware of and respond to local conditions that may influence the
development of vegetative stabilization measures. As with any planting design, climate,
maintenance practices, the availability of plant material (including native species), and many
other factors will influence such considerations as plant or seed mix selection, installation
methods, and project scheduling.
Slope Stabilization. On slopes, the goal of vegetative stabilization is not only to redupe surface
erosion but also to prevent slope failure. Vegetation should provide dense coverage to protect
soils from the direct impact of precipitation and help intercept runoff. A variety of plants should
be used to provide root systems that are distributed throughout all levels of the soil, increasing
slope shear strength and giving plants a greater ability to remove soil moisture. Uniform mats of
shallow rooting plants should be avoided because, while such plants may increase runoff
infiltration, they cannot remove soil moisture beyond the surface level, leaving slopes potentially
saturated and prone to slippage. Shallow, interlocking root systems may also increase the size of
a soil slippage by holding together and pulling down a larger area of slope after a small section
has given way. Large trees that have become unstable may also pull down slopes and should be
removed. Using plants with low water requirements can reduce the potential for soil saturation
from irrigation.
Swale Stabilization. On swales, the goal of vegetative stabilization is to prevent erosion within
the swale, where runoff is concentrated and flows at higher velocities. If natural stream channels
are involved, vegetation with deep root systems should be preserved, or if absent, planted above
the channel to help maintain the channel banks. More information is provided in the subsequent
section dealing with grass-lined swales.
Surface Stabilization. On large, flat areas, the goal of vegetative stabilization is to reduce the
loss of surface soil from sheet erosion. Vegetation should provide complete coverage to reduce
the force of precipitation, which can shift soil particles to seal openings in the soil, reducing
infiltration and increasing runoff. Vegetation should also provide many stem penetrations to
slow runoff and increase infiltration. Deep rooting plants are less critical for erosion control in-
flat areas than on slopes because soils are not subject to the same forces that may cause slippage
on a slope. However, trees and shrubs can increase infiltration, lessening the buildup of runoff,
and transpire large volumes of water, reducing soil saturation.
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In areas susceptible to wind erosion, the goal of vegetative stabilization is to establish direct
protection of the soil. Vegetation should provide dense and continuous surface cover. Binding
the soil deeply is generally not a requirement. The ideal vegetation for this purpose is grass,
which forms a mat of protection. In areas where the vegetation is developed, the grass generally
has high maintenance requirements. In less developed, open areas, unmown grass, including
perennial native species, can be used to provide protection. Trees and shrubs also can provide
protection from the wind.
Shoreline Stabilization. In lakes and ponds, the goal of vegetative stabilization is to prevent
erosion of the shoreline. Wetland plants anchor the bottom of the lake or pond adjacent to the
shore and help dissipate the erosive energy of waves. An important consideration in planting
along shorelines is the need to establish favorable conditions for plant establishment and growth.
These include the proper grading of side slopes and the control of upland erosion to prevent the
buildup of silt and associated pollutants in the water. Designers should maintain awareness of
regulatory requirements that may influence vegetation projects in a wetland environment
(USAF,1998)..
Vegetation used for shoreline stabilization work should be native material selected on the basis.
of strength, resiliency, vigor, and ability to withstand periodic inundation. Woody vegetation
with short, dense, flexible tops and large root systems works well. Other important factors
include rapid initial growth, ability to reproduce, and resistance to disease and insects.
According to Heyer, n.d., most strearribank stabilization plantings have used various willows,
including black willow (Salix nigrd), sandbar willow (S. interior), meadow willow (S.
petiolaris), heartleaf willow (S. rigida), and Ward willow (S. caroliniand). The size used
depends on the severity of the erosion and the type of bank to be stabilized. Whatever the size, it
is important to use dormant cuttings and to remove all lateral branches. Most tree revetment
projects used either eastern red cedar (Juniperus virginiand) or hardwoods such as northern pin
oak (Quercus ellipsoidalis). Important suggestions include the following:
• Choose trees with many limbs and branches to trap as much sediment as possible.
• Select decay-resistant trees.
• Use recently cut trees—dead trees are more brittle and likely to break apart.
• The tree size-diameter of the tree crown should be about two-thirds of the height of the
eroding bank.
• Gut off any trunk without limbs.
• Place the tree revetments overlapping, butt end pointing upstream.
• Begin and end revetments at stable points along the bank.
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• Choose an anchoring system according to the bank material to be stabilized and the weight of
the object to be anchored.
Vegetative measures for streambank stabilization offer an alternative to structural measures and
are becoming well known as bioengineering techniques for streambanks. Utilizing vegetative
material for streambank stabilization could be the first step in the reestablishment of the riparian
forest, which is essential for long-term stability of the streamside and floodplain areas. Each site
must be evaluated separately as to the feasibility of using natural material (Heyer, n.d.).
Vegetative streambank stabilization, with the goal to protect streambanks from the erosive forces
of flowing water, is generally applicable where bankfull flow velocity does not exceed 6 ft/sec
and soils are erosion resistant (Smolen, 1988). Table 5-4 includes general guidelines for
maximum allowable velocities in streams to be protected by vegetation.
Table 5-4. Conditions Where Vegetative Streambank Stabilization Is Acceptable
Frequency of Bankfull Flow
> 4 times/yr
1 to 4 times/yr
Maximum Allowable Velocity for
Highly Erodible Soil
4 ft/sec
5 ft/sec
6 ft/sec
Maximum Allowable Velocity for
Erosion-Resistant Soil ,
5 ft/sec
6 ft/sec ,
6 ft/sec
Source: Smolen, 1988. '
Temporary Vegetative Stabilization. Temporary vegetative cover such as rapidly growing
annuals and legumes can be used to establish a temporary vegetative cover. Such covers are
recommended for areas that (Fifield, 1999):
• Will not be brought to final grade within 30 days or are likely to be redisturbed.
• Require seeding of cut and fill slopes under construction.
• Require stabilization of soil storage areas and stockpiles.
• Require stabilization of temporary dikes, dams, and sediment containment systems. .
• Require development of cover or nursery crops to assist with establishing perennial grasses.
Examples of temporary vegetation include wheat, oats, barley, millet, and sudan. Temporary
seeding may not be effective in arid or semi-arid regions where seasonal conditions (lack of
moisture) prevent germination. It may be necessary to use a mixture of warm and cool season
grasses to ensure germination. Mulching and geotextiles can be used to help provide temporary
stabilization with vegetation, particularly hi situations where establishing cover may be difficult.
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Permanent Vegetative Stabilization. Permanent vegetative cover such as a perennial grass or a
legume cover can be used to establish a permanent vegetative cover. Permanent vegetation is
recommended for (Fifield, 1999)
• Final graded or cleared areas where permanent vegetative cover is needed to stabilize the soil
• Slopes designated to be treated with erosion control blankets
• Grass-lined channels or waterways designed to be channel liners
The following sub-sections discuss the various types or means of providing vegetative
stabilization.
5.1.5.1.2.1
General Description
GRASS-LINED CHANNELS
Grass-lined channels, or swales, convey storm water runoff through a stable conduit. Vegetation
lining the channel reduces the flow velocity of concentrated runoff. Grassed channels are
usually not designed to control peak runoff loads by themselves and are often used in
combination with other BMPs such as subsurface drains and riprap stabilization.
Applicability
Grassed channels should be used in areas where erosion-resistant conveyances are needed, such
as in areas with highly erodible soils and slopes of less than 5 percent. They should be installed
only where space is available for a relatively large cross-section. Grassed channels have a
limited ability to control runoff from large storms and should not be used in areas where velocity
exceeds 5 feet per second unless they are on erosion-resistant soils with dense groundcover at the
soil surface.
Design and Installation Criteria
)
Because of their ease of construction and low cost, vegetated-lined waterways are frequently
used on diversion and collection ditches. USDA's Soil Conservation Service's (SCS)
Engineering Field Manual (1979) recommends the following maximum permissible velocities
for individual site conditions shown in Table 5-5.
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Table 5-5. Maximum Permissible Velocities for Individual Site
Conditions for Grass Swales
Site Location
Areas where only a sparse cover can be established or
maintained because of shale, soils, or climate
If the vegetation is to be established by seeding
Areas where a dense, vigorous sod is obtained quickly
or where the runoff can diverted out of the waterway
while the vegetation is being established
Velocity
3.00 ft/sec (0.91 m/sec)
3.00 to 4.00 ft/sec (0.91 to 1.22 m/sec)
4.00 to 5.00 ft/sec (1.22 to 1.52 m/sec)
Source: USDA, 1979
Grassed waterways typically begin eroding in the invert of the channel if the velocity exceeds
the sheer strength of the vegetation soil interface. Once the erosion process has started, it will
continue until an erosion-resistant layer is encountered. If erosion of a channel bottom is \
occurring, rock or stone should be placed in the eroded area or the design should be changed
(UNEP, 1994).
Grassed waterways on construction land must be able to carry peak runoff events from snpwmelt
and rainstorms (in some areas limited to up to 1 cubic meter of water per second). The size of the
waterway depends on the size of the area to be drained. A typical grassed waterway cross-section
is parabolic-shaped with a nearly flat-bottomed channel, a bottom width of 3 m and channel
depth of at least 30 cm. Side slopes usually rise about 1 m for every 10 m horizontal distance but
may be as steep as a 1 m rise for every 2 m of horizontal distance. The waterway should follow
the natural drainage path if possible (Vanderwel, 1998). The design should be site-specific and
use available, well-established procedures. .
Lined channels are a means of dropping water to lower elevations along steep parts of a
waterway. Those portions of the waterway are precisely shaped and carefully lined with heavy-
duty erosion control matting, a type of geotextile product. The lining is covered with a layer of
soil and seeded to grass. The resulting -channel is highly resistant to erosion. Lined channels are
appropriate for waterways that only carry water occasionally and have slopes of up to 10 percent.
Companies that sell geotextile products provide detailed information on installation of their
products (Vanderwel and Abday, 1998). The design should be site-specific, using well-
established procedures. No standard procedure is available for evaluating the effectiveness of
geotextile liners for pollutant removal.
Grass-lined channels should be sited in accordance with the natural drainage system and should
not cross ridges. The channel design should not have sharp curves or significant changes in
slope. The channel should not receive direct sedimentation from disturbed areas and should be
sited only on the perimeter of a construction site to convey relatively clean storm water runoff.
They should be separated from disturbed areas by a vegetated buffer or other BMP to reduce
sediment loads.
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Although exact design criteria should be based on local conditions, basic design
recommendations for grassed channels include the following:
• Construction and vegetation of the channel should occur before grading and paying activities
begin.
• - Design velocities should be less than 5 ft/sec.
• Geotextiles can be used to stabilize vegetation until it is fully established.
• Covering the bare soil with sod or geotextiles can provide reinforced storm water
conveyance immediately.
• Triangular-shaped channels should be used with low velocities and small quantities of
runoff; parabolic grass channels are used for larger flows and where space is available;
trapezoidal channels are used with large flows of low velocity (low gradient).
• Outlet stabilization structures might be needed if the runoff volume or velocity has the
potential to exceed the capacity of the receiving area.
• Channels should be designed to convey runoff from a 10-year storm without erosion.
• The sides of the channel should be sloped less than 3:1, with V-shaped channels along roads
sloped 6:1 or less for safety.
• All trees, bushes, stumps, and other debris should be removed during construction.
Effectiveness
Grass-lined channels can effectively transport storm water from construction areas if they are
designed for expected flow volumes and velocities and if they do not receive sediment directly
from disturbed areas. The primary function is to carry the flow at a higher velocity without
eroding or overtopping the channel.
Limitations
Grassed channels, if improperly installed, can alter the natural flow of surface water and have
adverse impacts on downstream waters. Additionally, if the design capacity is exceeded by a
large storm event, the vegetation might not be sufficient to prevent erosion and the channel
might be destroyed. Clogging with sediment and debris reduces the effectiveness of grass-lined
channels for storm water conveyance.
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Maintenance ,
Maintenance requirements for grass channels are relatively minimal. During the vegetation
establishment period, the channels should be inspected after every rainfall. Other maintenance
activities that should be carried out after vegetation is established are mowing, litter removal,
and spot vegetation replacement. The most important objective in the maintenance of grassed
channels is the maintaining of a dense and vigorous growth of turf. Periodic cleaning of
vegetation and soil buildup in curb cuts is required so that water flow into the channel is;
unobstructed. During the growing season, channel grass should be cut no shorter than the level
of design flow, and the cuttings should be removed promptly.
Cost
Costs of grassed channels range according to depth, with a 1.5-foot-deep, 10-foot-wide grassed
channel estimated at between $6,395 and $17,075 per trench, while a 3.0-foot-deep, 21-foot-
wide grassed channel is estimated at $12,909 to $33,404 per trench (SWRPC, 1991).
As an alternative cost approximation, grassed channel construction costs can be developed using
unit cost values. Shallow trenching (1 to 4 feet deep) with a backhoe in areas not requiring
dewatering can be performed for $4 to $5 per cubic yard of removed material (R. S. Means,
2000). Assuming no disposal costs (i.e., excavated material is placed on either side of the
trench), only the cost of fine grading, soil treatment, and grassing (approximately $2 per square
yard of earth surface area) should be added to the trenching cost to approximate the total
construction cost. Site-specific hydrologic analysis of the construction site is necessary to
estimate the channel conveyance requirement, however, it is not unusual to have flows on the
order of 2 to 4 cfs per acre served. For channel velocities between 1 and 3 feet per secorid, the
resulting range in the channel cross-section area can be as low as 0.67 square foot per acre
drained to as high as 4 square feet per acre. If the average channel flow depth is 1 foot, then the
low estimate for grassed channel installation is .$0.27 per square foot of channel bottom per acre
served per foot of channel length. The high estimate is $ 1.63 per square-foot of channel bottom
per acre served per foot of channel length.
5.1.5.1.2.2 SEEDING
General Description
Permanent seeding, is used to control runoff and erosion on disturbed areas by establishing
perennial vegetative cover from seed. It is used to reduce erosion, decrease sediment yields from
disturbed areas, and provide permanent stabilization. This practice is both economical and
adaptable to different site conditions, and it allows selection of the most appropriate plant
materials. Seeding is a best management practice that is particularly susceptible to local
conditions such as the climatic conditions, physical and chemical characteristics of the soil,
topography, and time of year.
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Applicability
Permanent seeding is well-suited in areas where permanent, long-lived vegetative cover is the
most practical or most effective method of stabilizing the soil. Permanent seeding can be used
on roughly graded areas that will not be regraded for at least a year. Vegetation controls erosion
by protecting bare soil surfaces from displacement by raindrop impacts and by reducing the
velocity and quantity of overland flow. The advantages of seeding over other means of
establishing plants include lower initial costs and labor inputs.
Design and Installation Criteria
Areas to be stabilized with permanent vegetation must be seeded or planted 1 to 4 months after
the final grade is achieved unless temporary stabilization measures are in place. Successful plant
establishment can be maximized with proper planning; consideration of soil characteristics;
selection of plant materials that are suitable for the site; adequate seedbed preparation, liming,
and fertilization; timely planting; and regular maintenance. Climate, soils, and topography are
major factors that dictate the suitability of plants for a particular site. The soil on a disturbed site
might require amendments to provide sufficient nutrients for seed germination and seedling
growth. The surface soil must be loose enough for water infiltration and root penetration. Soil
pH should be between 6.0 and 6.5 and can be increased with liming if soils are too acidic. Seeds
can be protected with mulch to retain moisture, regulate soil temperatures, and prevent erosion
during seedling establishment.
Seedbed preparation is critical in established vegetation. Spraying seeds on a scraped slope,will
generally not provide satisfactory results. Typical seedbed preparation will begin with a soil test
to determine title amount of lime or fertilizer that should be added. In addition, tillage should be
performed that will break up clods so that seed contact can be established. When the seed is
applied, it should be covered and lightly compacted. An appropriate natural or synthetic mulch is
recommended to provide surface stabilization until the vegetation is established. In addition to
providing surface stabilization, the mulch will also retard evaporation and encourage rapid ~
growth. A suitable tack to hold the mulch may be necessary if the mulch is not otherwise
anchored. Mulches are covered in a subsequent sub-section.
Depending on the amount of use permanently seeded areas receive, they can be considered high-
or low-maintenance areas. High-maintenance areas are mowed frequently, limed and fertilized
regularly, and either (1) receive intense use (for example, athletic fields) or (2) require
maintenance to an aesthetic standard (for example, home lawns). Grasses used for high-
maintenance areas are long-lived perennials that form a tight sod and are fine-leaved.
High-maintenance vegetative cover is used for homes, industrial parks, schools, churches, and
recreational areas.
Low-maintenance areas are mowed infrequently or not at all and do not receive lime or fertilizer
on a regular basis. Plants must be able to persist with minimal maintenance over long periods of
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time. Grass and legume mixtures are favored for these sites because legumes fix nitrogen from
the atmosphere. Sites suitable for low-maintenance vegetation include steep slopes, streambanks
or channel banks, some commercial properties, and "utility" turf areas such as road-banks.
Effectiveness
Seeding that results in a successful stand of grass has been shown to remove between 50 and 100
percent of total suspended solids from storm water runoff, with an average removal of 90 percent
(USEPA, 1993).
Limitations .
The effectiveness of permanent seeding can be limited because of the high erosion potential
during establishment, the need to reseed areas that fail to establish, limited seeding times
depending on the season, and the need for stable soil temperature and soil moisture content
during germination and early growth. Permanent seeding does not immediately stabilize
soils—temporary erosion and sediment control measures should be in place to prevent off-site
transport of pollutants frofn disturbed areas. Use of mulches and/or geotextiles may improve the
likelihood of'successfully establishing vegetation.
Maintenance .
Grasses should emerge within 4 to 28 days and legumes 5 to 28 days after seeding, with legumes
following grasses. A successful stand should exhibit the following: ,
• Vigorous dark green or bluish green seedlings—not yellow
• Uniform density, with nurse plants, legumes, and grasses well intermixed
• Green leaves—perennials remaining throughout the summer, at least at the plant bases',
Seeded areas should be inspected for failure, and necessary repairs and reseeding should be
made as soon as possible. If a stand has inadequate cover, the choice of plant materials and
quantities of Lime and fertilizer should be reevaluated. Depending on the condition of the stand,
areas can be repaired by overseeding or reseeding after complete seedbed preparation. If the
timing is bad, an annual grass seed can be overseeded to temporarily thicken the stand until a
suitable time for seeding perennials. Consider seeding temporary, annual species if the season is
not appropriate for permanent seeding. If vegetation fails to grow, the soil should be tested to
determine whether low pH or nutrient imbalances are responsible. Local NRCS or county
extension agents can also be contacted for seeding and soil testing recommendations.
On a typical disturbed site, full plant establishment usually requires refertilization in the second
growing season. Soil tests should be used to determine whether more fertilizer needs to be
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added. Do not fertilize cool season grasses in late May through July. Grass that looks yellow
may be nitrogen deficient. Nitrogen fertilizer should not be used if the stand contains more than
20 percent legumes. . .
Cost
Seeding costs range from $200 to $1,000 per acre and average $400 per acre. Maintenance costs
range from 15 to 25 percent of initial costs and average 20 percent (USEPA, 1993). R. S. Means
(2000) indicates the cost of mechanical seeding to be approximately $900 per acre, and
demonstrates that the coverage cost varies with the seed type, seeding approach and scale (total
acreage to be seeded). For example, hydro or water-based seeding for grass is estimated to be,
$700 per acre but seeding of "field" grass species is only $540 per acre (Costs include materials,
labor, and equipment, with profit and overhead). If surface preparation is required;, then the
installation costs increase. R. S. Means suggests the cost of fine grading, soil treatment, and
grassing is approximately $2 per square yard of earth surface area.
5.1.5.1.2.3
SODDING
General Description
Sodding is a permanent erosion control practice that involves laying a continuous cover of grass
sod on exposed soils. In addition to stabilizing soils, sodding can reduce the velocity of storm
water runoff. Sodding can provide immediate vegetative cover for critical areas and stabilize
areas that cannot be vegetated by seed. It can also stabilize channels or swales that convey
concentrated flows and reduce flow velocities. While sodding is not as dependent as seeding on
local conditions, it does depend on soil and climatic conditions to be successful. Capability to
water immediately after installation and occasionally until establishment is generally beneficial.
Applicability
Sodding is appropriate for any graded or cleared area that might erode, requiring immediate
vegetative cover. Locations particularly well-suited to sod stabilization are:
• Waterways and channels carrying intermittent flow
• Areas around drop inlets that require stabilization
• Residential or commercial lawns and golf courses where prompt use and aesthetics are
important
• Steeply sloped areas
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Design and Installation Criteria
Sodding eliminates the need for seeding and mulching and produces more reliable results with
less maintenance. Sod can be laid during times of the year when seeded grasses can faili The
sod must be watered frequently within the first few weeks of installation.. Some seedbed
preparation is recommended, including smoothing to provide contact between the sod and the
soil surface and soil testing to determine liming and fertilizer application rates. Since sod
provides instantaneous cover, mulches are not typically recommended, but anchoring may be
appropriate on steep slopes.
The type of sod selected should be composed of plants adapted to site conditions. Sod
composition should reflect environmental conditions as well as the function of the area where
the sod will be laid. The sod should be of known genetic origin and be free of noxious weeds,
diseases, and insects. The sod should be machine cut at a uniform soil thickness of 15 to 25 mm
at the tune of establishment (this does not include top growth or thatch). Soil preparation and
addition of lime and fertilizer may be needed—soils should be tested to determine whether
amendments are needed. Sod should be laid in strips perpendicular to the direction of water flow
and staggered in a brick-like pattern. The corners and middle of each strip should be stapled
firmly. Jute or plastic netting may be pegged over the sod for further protection against washout
during establishment.
Areas to be sodded should be cleared of trash, debris, roots, branches, stones, and clods larger
than 2 niches in diameter. Sod should be harvested, delivered, and installed within a period of
36 hours. Sod not transplanted within this period should be inspected and approved prior to its
installation.
Limitations
Compared to seed, sod is more expensive and more difficult to obtain, transport, and store. Care
must be taken'to prepare the soil and provide adequate moisture before, during, and after
installation to ensure successful establishment. If sod is laid on poorly prepared soil or
unsuitable surface, the grass will die quickly because it is unable to root. Sod that is not
adequately irrigated after installation may cause root dieback because grass does not root rapidly
and is subject to drying out.
Effectiveness
Sod has been shown to remove between 98 and 99 percent of total suspended solids in runoff
(USEPA, 1993). It is therefore a highly effective management practice for erosion and sediment
control.
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Maintenance
Watering is very important to maintain adequate moisture in the root zone and to prevent
dormancy, especially within the first few weeks of installation, until it is fully rooted. Mowing
should not result in the removal of more than one-third of the shoot. Grass height should be
maintained at between 2 and 3 inches. After the first growing season, sod might require
fertilization or liming. Permanent, fine turf areas require yearly maintenance fertilization.
Warm-season grass should be fertilized in late spring to early summer, and cool-season grass in
late winter and again in early fall.
Cost
Average construction costs of sod average $0.20 per square foot and range from $0.10 to $1.10
per square foot; maintenance costs are approximately 5 percent of installation costs (USEPA,
1993). R. S. Means (2000) indicates the sodding ranges between $250 and $750 per 1000 square
feet for 1" deep bluegrass sod on level ground, depending on the size of the area treated (unit
costs value are for orders over 8,000 square feet and less than 1000 square feet, respectively).
Bent grass sod values range between $350 and $500 per 1000 square feet, again the lower value
is more likely for most construction sites because it is for large area applications. (Costs include
materials, labor, and equipment, with profit and overhead).
5.1.5.1.2.4
MULCHING
General Description
Mulching is a temporary erosion control practice in which materials such as grass, hay, wood
chips, wood fibers, straw, or gravel are placed on exposed or recently planted soil surfaces.
Mulching is highly recommended as a stabilization method and is most effective when anchored
in place until vegetation is well established. In addition to stabilizing soils, mulching can reduce
the velocity of storm water runoff. When used in combination with seeding or planting,
mulching can aid plant growth by holding seeds, fertilizers, and topsoil in place; by preventing
birds from eating seeds; by retaining moisture; and by insulating plant roots against extreme
temperatures.
Mulch mattings are materials such as jute or other wood fibers that are formed into sheets and
are more stable than loose mulch. They can also be easily unrolled during the installation
process and are particularly useful in steeper areas or in channels. Netting can be used to
stabilize soils while plants are growing, although netting does not retain moisture or insulate
against extreme temperatures. Mulch binders consist of asphalt or synthetic materials that are
sometimes used instead of netting to bind loose mulches but have been found to have limited
usefulness.
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Applicability
Mulching is often used in .areas where temporary seeding cannot be used because of
environmental constraints. Mulching can provide immediate, effective, and inexpensive erosion
control. On steep slopes and critical areas such as waterways, mulch matting is used with
netting or anchoring to hold it in place. Mulches can be used on seeded and planted areas where
slopes are steeper than 2:1 or where sensitive seedlings require insulation from extreme
temperatures.
Design and Installation Criteria
When possible, organic mulches should be used for erosion control and plant material
establishment. Suggested materials include loose straw, netting, wood cellulose, or agricultural
silage. All materials should be free of seed, and loose hay or .straw should be anchored by
applying tackifier, stapling netting over the top, or crimping with a mulch crimping tool.
Materials that are heavy enough to stay in place do not need anchoring (for example, gravel).
Steepness of the slope will also affect the extent of anchoring the mulch. Other examples
include hydraulic mulch products with 100 percent post-consumer paper content, yard trimming
composts, and wood mulch from recycled stumps and tree parts. Inorganic mulches such as pea
gravel or crushed granite can be used in unvegetated areas.
Mulches may or may not require a binder, netting, or tacking. All straw and loose materials
must have a binder to hold them hi place. Mulch materials that float away during storms can
•clog drainage ways and lead to flooding. The extent of binding depends on the type of mulch
applied. Effective use of netting and matting material requires firm, continuous contact between
the materials and the soil. If there is no contact, the material will not hold the soil and erosion
will occur underneath the material. Grading is not necessary before mulching.
There must be adequate coverage, or erosion, washout, and poor plant establishment will result.
If an appropriate tacking agent is not applied, or if it is applied in an insufficient amount, mulch
will not withstand wind and runoff. The channel grade and liner must be appropriate for the
amount of runoff, or the channel bottom will erode. Also, hydromulch should be applied in
spring, summer, or fall to prevent deterioration of the mulch before plants can become
established. Table 5-6 presents guidelines for installing mulches, but local conditions may
warrant additional requirements.
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Table 5-6. Typical Mulching Materials and Application Rates
Material
Rate per
Acre
Requirements
Notes
Organic Mulches .
Straw
Wood fiber or wood
cellulose
Wood chips
Bark
1-2 tons
0.5-1 ton
5-6 tons
35yd3
Dry, unchopped, unweathered; avoid
weeds.
Air dry. Add fertilizer N, 12 Ib/ton.
Air dry, shredded or hammermilled,
or chips.
Spread by hand or machine; must be
tacked or tied down.
Use with hydroseeder; may be used to
tack straw. Do not use in hot, dry
weather.
Apply with blower, chip handler, or
by hand. Not for fine turf areas.
Apply with mulch blower, chip
handler, or by hand. Do not use
asphalt tack.
Nets and Mats
Jute net
Excelsior
(wood fiber) mat
Fiberglass roving
Cover area
Cover area
0.5-1 ton
Heavy, uniform; woven of single jute
yarn. Used with organic mulch.
Continuous fibers of drawn glass
bound together with a non-toxic
agent.
Withstands water flow.
Apply with compressed air ejector.
Tack with emulsified asphalt at a rate
of 25-35 gal/1,000 ft2.
Effectiveness
Mulching effectiveness varies with the type of mulch used and local conditions such as rainfall
and runoff amounts. Percent soil loss reduction for different mulches ranges from 53 to 99.8
percent used and associated water velocity reductions range from 24 to 78 percent (Harding,
1990). Table 5-7 shows soil loss and water velocity reductions for different mulch treatments.
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Table 5-7. Measured Reductions in Soil Loss for Different Mulch Treatments
Mulch characteristics
100% wheat straw/top net
100% wheat straw/two nets
70% wheat straw/30% coconut
fiber
70% wheat straw/30% coconut
fiber
100% coconut fiber
Nylon monofilament/two nets
Nylon
monofilament/rigid/bonded
Vinyl
monofilament/flexible/bonded
Curled wood fibers/top net
Curled wood fibers/two nets
Antiwash nettingft'ute)
Interwoven paper and thread
Uncrimped wheat straw-2,242
kg/ha
Uncrimped wheat straw— 4,484
kg/ha
Soil loss
reduction
(%)
97.5
98.6
98.7
99.5
98.4
99.8
53.0
89.6
90.4
93.5
91.8
93.0
84.0
89.3
Water velocity reduction
(%)relative to bare soil
73
56
71
78
77
74
24
32
47
59
59
53
45
59
Source: Harding, 1990, as cited in USEPA, 1993.
Limitations ' ,
Mulching, matting, and netting might delay seed germination because the cover changes soil
surface temperatures. The mulches themselves are subject to erosion and may be washed away
in a large storm if not sufficiently anchored with netting or tacking. Maintenance is necessary to
ensure that mulches provide effective erosion control.
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Maintenance
Mulches must be anchored to resist wind displacement. Netting should be removed when
protection is no longer needed and disposed of in a landfill or composted. Mulched areas should
be inspected frequently to identify areas where mulch has loosened or been removed, especially
after rain storms. Such areas should be reseeded (if necessary) and the mulch cover replaced
immediately. Mulch binders should be applied at rates recommended by the manufacturer. If
washout, breakage, or erosion occurs, surfaces should be repaired, reseeded, and remulched, and
new netting should be installed. Inspections should be continued until vegetation is firmly '
established.
Cost
The costs of seed and mulch average $1,500 per acre and range from $800 to $3,500 per acre
(USEPA, 1993). R. S. Means (2000) estimates the cost of power mulching to be $22.50 per
1000 square feet, for large volume applications. In addition, hydro- and mechanical seeding are
approximately $700 to $900 per acre. Coverage cost varies with the seed type, seeding approach,
and scale (total acreage to be seeded). For example, hydro or water-based seeding for grass is
estimated to be $700 per acre, but seeding of "field" grass species is only $540 per acre. (Costs
include materials, labor, and equipment, with profit and overhead.) If surface preparation is
required, then the installation costs increase. R. S. Means (2000) suggests the cost of fine
grading, soil treatment, and grassing, is approximately $2 per square yard of earth surface area.
5.1.5.1.2.5
GEOTEXTILES
General Description
Geotextiles are porous fabrics also known as filter fabrics, road rugs, synthetic fabrics,
construction fabrics, or simply fabrics. Geotextiles are manufactured by weaving or bonding
fibers made from synthetic materials such as polypropylene, polyester, polyethylene, nylon,
polyvinyl chloride, glass, and various mixtures of these materials. As a synthetic construction
material, geotextiles are used for a variety of purposes such as separators, reinforcement,
filtration and drainage, and erosion control (USEPA, 1992). Some geotextiles are made of
biodegradable materials such as mulch matting and netting. Mulch mattings are jute or other
wood fibers that have been formed into sheets and are more stable than normal mulch. Netting
is typically made from jute, wood fiber, plastic,, paper, or cotton and can be used to hold the
mulching and matting to the ground. Netting can also be used alone to stabilize soils while the
plants are growing; however, it does not retain moisture or temperature well.
Geotextiles can aid in plant growth by holding seeds, fertilizers, and topsoil in place. Fabrics are
relatively inexpensive for certain applications—a wide variety of geotextiles exist to match the
specific needs of the site.
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Applicability
Geotextiles can be used for erosion control by using it alone. Geotextiles can be used as matting,
which is used to stabilize the flow of channels or swales or to protect seedlings on recently
planted slopes until they become established. Matting may be used on tidal or streambanks
where moving water is likely to wash out new plantings. They can also be used to protect
expo'sed soils immediately and temporarily, such as when active piles of soil are left overnight.
Geotextiles are also used as separators. An example of such a use is geotextile as a separator
between riprap and soil. This "sandwiching" prevents the soil from being eroded from beneath
the riprap and maintaining the riprap's base.
Design and Installation Criteria
Many types of geotextiles are available. Therefore, the selected fabric should match its purpose.
State or local requirements, design procedures, and any other applicable requirements should be
considered. In the field, important concerns include regular inspections to determine whether
cracks, tears, or breaches are present in the fabric and appropriate repairs should be made.
Effective netting and matting require firm, continuous contact between the materials and the soil.
If there is no contact, the material will not hold the soil and erosion will occur underneath the
material.
Effectiveness
A geotextile's effectiveness depends upon the strength of the fabric and proper installation. For
example, when protecting a cut slope with a geotextile, it is important to properly anchor the
fabric using appropriate length and spacing of wire staples. This will ensure that it will not be
undermined by a storm event.
Limitations
Geotextiles (primarily synthetic types) have the potential disadvantage of being sensitive to light
and must be protected prior to installation. Some geotextiles might promote increased runoff
and might blow away if not firmly anchored. Depending on the type of material used,
geotextiles might need to be disposed of in a landfill, making them less desirable than vegetative
stabilization. If the fabric is not properly selected, designed, or installed, the effectiveness may
be reduced drastically.
Maintenance
Regular inspections should be made to determine whether cracks, tears, or breaches have formed
in the fabric—it should be repaired or replaced immediately. It is necessary to maintain contact
between the ground and the geotextile at all times.
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Cost
Costs for geotextiles range from $0.50 to $10.00 per square yard depending on the type chosen
(SWRCP, 1991). Geosynthetic turf reinforcement mattings (TRMs) are widely used for
immediate erosion protection and long-term vegetative reinforcement, usually for steeply sloped
areas or areas exposed to runoff flows. The Erosion Control Technology Council (a geotextile
industry support association) estimates TRMs cost approximately $7.00 per square yard
(installed) for channel protection (ECTC, 2002a). Channel protection is one of the most
demanding of installations (much more demanding than general coverage of denuded area). The
ECTC estimates the cost to install a simple soil blanket (or rolled erosion control product), seed,
and fertilizer to be $ 1.00 per square yard (ECTC, 2002b).
5.1.5.1.2.6
VEGETATED BUFFER STRIPS
General Description
Vegetated buffers are areas of either natural or established vegetation that are maintained to
protect the water quality of neighboring areas. Buffer zones reduce the velocity of storm water
runoff, provide an area for the runoff to permeate the soil, allow groundwater recharge, and act
as filters to catch sediment. The reduction in velocity also helps to prevent soil erosion.
Applicability
Vegetated buffers can be used in any area that is able to support vegetation, but they are most
effective and beneficial on floodplains, near wetlands, along streambanks, and on steep, unstable
slopes. They are also effective in separating land use areas that are not compatible and hi
protecting wetlands or waterbodies by displacing activities that might be potential sources of
nonpoint source pollution.
Design and Installation Criteria
To establish an effective vegetative buffer, the following guidelines should be followed:
• Soils should not be compacted.
• Slopes should be less than 5 percent.
• Buffer widths should be determined after careful consideration of slope, vegetation, soils,
depth to impermeable layers, runoff sediment characteristics, type and quantity of storm
water pollutants, and annual rainfall.
• Buffer widths should increase as slope increases.
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• Zones of vegetation (native vegetation in particular), including grasses, deciduous and
evergreen shrubs, and understory and overstory trees, should be intermixed.
• In areas where flows are concentrated and velocities are high, buffer zones should be
combined with other structural or nonstructural BMPs as a pretreatment. '•
\
Vegetated strips have been studied extensively, with emphasis placed on their effectiveness in
removing sediment and other pollutants. Vegetated strips are most appropriate at sites where
sediment loads are relatively low, as high sediment loads will cause large quantities of
deposition along the leading edge of the vegetation. This deposition will cause the flow to divert
around the vegetation hi a concentrated flow pattern, which will cause short-circuiting and
greatly reduce removal efficiency. Variability in vegetation density and uniformity often :causes
similar problems. Removal efficiency depends on a combination of slope, length, and width of
the filter; density of the vegetation; sediment characteristics, hydraulics of the flow; and!
infiltration. The interaction of these variables is complex and prevents the process from being
reduced to a simple relationship except on a local basis. For site-specific local conditions,
methods have been developed that allow trapping to be related to strip length and slope.'
Effectiveness
Considerable data have been collected on the effectiveness of buffer strips for specific
conditions. Numerous factors such as infiltration rate, flow depth, slope, dimensions of the
buffer, density and type of vegetation, sediment size, and sediment density impact removal rates.
Recent studies show that even short vegetative buffers can trap high percentages of sediment and
certain chemicals. A significant concern is whether flow is allowed to concentrate, which will
greatly reduce the travel tune through the buffer and prevent the removal of pollutants.
Several researchers have measured greater than 90 percent reductions in sediment and nitrate
concentrations; buffer/filter strips do a reasonably good job of removing phosphorus attached to
sediment, but are relatively ineffective hi removing dissolved phosphorus (Gillman, 1994).
However, since the hydraulics of flow through buffers strips are not well defined and can vary
considerably based on site conditions, it is difficult to consistently estimate the effectiveness of
buffers strips.
Limitations
Vegetated buffers require plant growth before they can be effective, and land must be available
on which to plant the vegetation. If the cost of the land is very high, buffer zones might hot be
cost-effective. Although vegetated buffers help to protect water quality, they usually do not
effectively counteract concentrated storm water flows to neighboring or downstream wetlands.
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Maintenance ' .
Keeping vegetation in vegetated buffers healthy requires routine maintenance, which (depending
on species, soil types, and climatic conditions) can include weed and pest control, mowing,
fertilizing, liming, irrigating, and pruning. Inspection and maintenance are most important when
buffer areas are first installed. Once established, vegetated buffers do not require much
maintenance beyond the routine procedures listed earlier and periodic inspections of the areas,
especially after any heavy rainfall and at least once a year. Inspections should focus on
encroachment, gully erosion, density of vegetation, evidence of concentrated flows through the
areas, and any damage from foot or vehicular traffic. If there is more than 6 inches of sediment
in one place, it should be removed.
Cost
Conceptual cost estimates for grassed buffer strips can be made based on square footage using
unit cost values. R. S. Means (2000) estimates the cost of fine grading, soil treatment, and
grassing to be $2 per square yard of earth surface area. This cost estimate is based on
application of traditional lawn seed. The cost for field seed is lower than lawn seed, reducing the
coverage price. Where gently sloping areas just need to be grassed with acceptable species, the
cost can be as low as $0.38 per square yard.
5.1.5.1.2.7
EROSION CONTROL MATTING
General Description
Erosion control mats can be either organic or made from a synthetic material. A wide variety of
products exist to match the specific needs of the site. Organic mats are made from such materials
as wood fiber, jute net, and coconut coir fiber.. Unlike organic matter, synthetic mats are
constructed from non-biodegradable materials and remain in place for many years. These
organic mats are classified as Turf Reinforcement Mats (TRMs) and Erosion Control and
Revegetation Mats (ECRMs) (USDOT, 1995).
Erosion control matting aids in plant growth-by holding seeds, fertilizers, and topsoil in place.
Matting can be used to stabilize the flow of channels or swales or to protect seedlings on recently
planted slopes until they become established. Matting can be used on tidal or streambanks *
where moving water is likely to wash out new plantings. It can also be used to protect exposed
soils immediately and temporarily, such as when active piles of soil are left overnight.
Applicability
Mulch mattings, netting, and filter fabrics are particularly useful in steep areas and drainage
swales where loose seed is vulnerable to being washed away or failing to survive dry soil
(UNEP, 1992).
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Erosion control mats can also be used to separate riprap and soil. This results in a
"sandwiching" effect, maintaining the riprap's base and preventing the soil beneath from being
eroded.
Design and Installation Criteria
Matting is especially recommended for steep slopes and channels (UNEP, 1992).
Many types of erosion control mats are available. Therefore, the selected product should match
its purpose. Effective netting and matting require firm, continuous contact between the materials
and the soil. If there is no contact, the material will not hold the soil and erosion will occur
underneath the material.
Wood fiber or curled wood mat consists of curled wood with fibers, 80 percent of which are 150
mm or longer, with a consistent thickness and even distribution of fiber over the entire mat. The
top side of the mat is covered with a biodegradable plastic mesh. The mat is placed in thp
channel or on the slope parallel to the direction of flow and secured with staples and check slots.
This is applied immediately after seeding operations (USDOT, 1995).
Jute net consists of jute yarn, approximately 5 mm in diameter, woven into a net with openings
that are approximately 10 by 20 mm (or 0.40 to 0.79 inches). The jute net is loosely laid in the
channel parallel to the direction of flow. The net is secured with staples and check slots at
intervals along the channel. Placement of die jute net is done immediately after seeding
operations (USDOT, 1995).
Coconut blankets are constructed of biodegradable coconut fibers that resist decay for 5 to 10
years to provide long, temporary erosion control protection. The materials are often encased in
ultraviolet stabilized nets and sometimes have a composite, polypropylene structure to provide
permanent turf reinforcement. These materials are best used for waterway stabilization and
slopes that require longer periods to stabilize (USDOT, 1995).
Under the synthetic mat category there are TRMs and.ECRMs. Turf reinforcement mats\SK
three-dimensional polymer nettings or monofilaments formed into a mat. They have sufficient
thickness (>13 mm or 0.5 inch) and void space (>90 percent) to allow for soil filling and
retention. The mat acts as a traditional mat to protect the seed and increase germination. As the
turf establishes, the mat remains in place as part of the root structure. This gives the established
turf a higher strength and resistance to erosion (USDOT, 1995).
Erosion control and revegetation mats are composed of continuous monofilaments bound by
heat fusion or stitched between nettings. They are thinner than TRMs and do not have the void
space to allow for filling of soil. They act as a permanent mulch and allow vegetation to grow
through the mat (USDOT, 1995).
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Effectiveness
The effectiveness of erosion control matting depends upon the strength of the material and
proper installation. For example, when protecting a cut slope with an erosion control mat, it is
important to anchor the mat properly. This will ensure that it will not be undermined by a storm
event.
While erosion control blankets can be effective, their performance varies. Some general trends
are that organic materials tend to be the most effective (Harding, 1990) and that thicker materials
are typically superior (Fifield, 1992), but there are exceptions to both of these trends.
Information about product testing of blankets is generally lacking. One notable exception is the
Texas Department of Transportation, which publishes the findings of their testing program in the
form of a list of acceptable and unacceptable materials for specific uses.
Limitations
Erosion control mats (primarily synthetic types) are sensitive to light and for this reason must be
protected prior to installation. Some erosion control mats might cause an increase in runoff or
blow away if not firmly anchored. Erosion control mats might need to be properly disposed of in
a landfill, depending on the type of material. Effectiveness may be reduced if the fabric is not
properly selected, designed, or installed.
Maintenance
Regular inspections are necessary to determine whether cracks, tears or breaches have formed in
the fabric. Contact between the ground and erosion control mat should be maintained at all
times and trapped sediment removed after each storm event.
Cost
Costs for erosion control mats range from $0.50 to $10.00 per square yard depending on the type
chosen (SWRCP, ,1991). Geosynthetic turf reinforcement mattings (TRMs) are widely used for
immediate erosion protection and long-term vegetative reinforcement, usually for steeply sloped
areas or areas exposed to runoff flows. The Erosion Control Technology Council (a geotextile
industry support association) estimates TRMs cost approximately $7.00 per square yard
(installed) for channel protection (ECTC, 2002a). Channel protection is one of the most
demanding of installations (much more demanding than general coverage of denuded area). The
ECTC estimates the cost to install a simple soil blanket (or rolled erosion control product), seed,
and fertilizer to be $ 1.00 per square yard (ECTC, 2002b).
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5.1.5.1.2.8
TOPSOILING
General Description
Topsoiling is the placement of a surface layer of soil enriched in organic matter over a prepared
subsoil to provide a suitable soil medium for vegetative growth on areas with poor moisture, low
nutrient levels, undesirable pH, and/or the presence of other materials that would inhibit the
establishment of vegetation. Advantages of topsoil include its high organic-matter content and
friable consistency and its available water-holding capacity and nutrient content. The texture
and friability of topsoil are usually more conducive to seedling emergence root growth. In
addition to being a better growth medium, topsoil is often less credible than subsoils, and the
coarser texture of topsoil increases infiltration capacity and reduces runoff. During construction,
topsoil is often removed from the project area and stockpiled. It is replaced over areas to be
grassed or landscaped during the final stages of the project. ;
Applicability
Conditions where topsoiling apply include the following:
• Where a sufficient supply of quality topsoil is available.
• Where the subsoil or areas of existing surface soil present the following problems:
- The structure, pH, or nutrient balance of the available soil cannot be amended by
reasonable means to provide an adequate growth medium for the desired vegetation.
- The soil is too shallow to provide adequate rooting depth or will not supply necessary
moisture and nutrients for growth of desired vegetation.
- The soil contains substances toxic to the desired vegetation.
• Where high quality turf or ornamental plants are desired.
• Where slopes are 2:1 or flatter. :
Design and Installation Criteria
The topsoil should be uniformly distributed over the subsoil to a minimum compacted depth of
50 mm (2 inches) on slopes steeper than 3 horizontal to 1 vertical and 100 mm (4 inches) on
flatter slopes. Thicknesses of 100 to 150 mm is preferred for vegetation establishment via
seeding. The topsoil should not be placed while in a frozen or muddy condition or when the
subsoil is excessively wet, frozen, or in a condition that is detrimental to proper grading or
seedbed preparation. The final surface should be prepared so that any irregularities are corrected
and depressions and water pockets do hot form. • If the topsoil has been treated with soil
sterilants, it should not be placed until the toxic substances have dissipated (USDOT, 1995).
Table 5-8 summarizes the cubic yards of topsoil required for application to various depths.
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Table 5-8. Cubic Yards of Topsoil Required for Application to Various Depths
Depth (inches)
1
2
3
4
5
6
Per 1,000 Sq Ft
3.1
6.2
9.3
,. 12.4
15.5
18.6
Per Acre
134
268
403
536
670
804
Source: Smolen et al., 1988.
On slopes and areas that will not be mowed, the surface may be left rough after spreading
topsoil. A disk may be used to promote bonding at the interface between the topsoil and subsoil
(Smolen et al., 1988).
Effectiveness
No information is available describing the effectiveness of applying topsoil as a BMP.
Limitations
Limitations of applying topsoil can include to following:
• i Topsoil spread when conditions were too wet, resulting in severe compaction.
• Topsoil mixed with too much unsuitable subsoil material, resulting in poor vegetation
establishment.
• Topsoil contaminated with soil sterilants or chemicals, resulting in poor or no vegetation
establishment.
• Topsoil not adequately incorporated or bonded with the subsoil, resulting in poor vegetation
establishment and soil slippage on sloping areas.
• Topsoiled areas not protected, resulting in excessive erosion.
Maintenance
Newly topsoiled areas should be inspected frequently until the vegetation is established. Eroded
or damaged areas should be repaired and revegetated.
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Cost
Top soiling costs are a function of the price of topsoil, the hauling distance, and the method of
application. R. S. Means (2000) report unit cost values of $3 and $4 per square yard, for 4 and 6
inches of top soil cover, respectively. This price is for furnishing and placing of top soil, and
includes materials, labor, and equipment, with profit and overhead.
5.1.5.2 WATER HANDLING PRACTICES
5.1.5.2.1 EARTH DIKE
General Description
An earth dike is a temporary or permanent ridge of soil designed to channel water to a desired
location. Dikes are used to divert the flow of runoff by constructing a ridge of soil that ,
intercepts and directs the runoff to the desired outlet or alternative management practice, such as
a pond. This practice serves to reduce the length of a slope for erosion control and protect
downslope areas. An earth dike can be used to prevent runoff from going over the top of a cut
and eroding the slope, directing runoff away from a construction site or building; to divert clean
water from a disturbed area; or to reduce a large drainage area into a more manageable size.
Dikes should be stabilized with vegetation after construction (NAHB, n.d.).
Applicability
Earth dikes are applicable to all areas; the. size of the dike is correlated to the size of the drainage
area (NAHB, n.d.).
Design and Installation Criteria -
The location of dikes should take into consideration outlet conditions, existing land use, '
topography, length of slope, soils, and development plans. The capacity of earth dikes and
diversions should be suitable for the area that is being protected, including adequate freeboard,
or extra depth that is added as a safety margin. For homes, schools, and industrial buildings, the
recommended design frequency storm is 50 years and the freeboard is 0.5 feet (NAHB, n.'d.).
Earth dikes can be employed as a perimeter control. For small sites, a compacted 2-foot-tall dike
is usually suitable, if hydroseeded. Larger dikes will actually divert runoff to another portion of
the site, usually to a downstream sediment trap or basin. Therefore, the designer should ensure
that they have the capacity for the 10-year storm event, and that the channel created behind the
dike is properly stabilized to percent erosion (Brown et al., 1997). In addition, the downstream
structure must be sized to handle the flow from the dike. Dikes should be designed using
standard hydrologic and hydraulic calculations and certified by a professional hydrologist, or
engineer.
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Diversion dikes should be installed prior to the majority of the soil-disturbing activity. As soon
as the dike form is completed, it should be machine compacted, fertilized, and either seeded and
mulched or sodded. Excavated materials should be properly stockpiled for future use or
disposed of properly. Dikes should have an outlet that functions with a minimum of erosion.
Depending on site conditions and outlet structures, the runoff directed by dikes may have to be
conveyed to a sediment-trapping device, such as a sediment basin or detention pond. As grades
increase over 4 percent, geotextile material or sod may be required to control erosion. Slopes
greater than 8 percent may require riprap. Dikes may be removed when stabilization of the
drainage area and outlet are complete (NAHB, n.d.). Dike design criteria must incorporate site-
specific conditions, as dimensions depend on expected flows, soil types, and climatic conditions.
All of these inputs vary tremendously over different sections of the country.
Effectiveness
No information has been found on the effectiveness of earth dikes used as BMPs, although
terraces often have sediment removal rates of up to 90 percent.
Limitations
An erosion-resistant lining in the channel may be needed to prevent erosion in the channel
caused by excessive grade. In addition, the channel should be deepened and the grade realigned
if there is overtopping caused by sediment in the channel where the grade decreases or reverses.
If overtopping occurs at low points in the ridge where the diversion crosses the shallow draw, the
ridge should be reconstructed with a positive grade toward the outlet at all points. Finally, if
there is erosion at the outlet, an outlet stabilization structure should be installed and if
sedimentation occurs at the diversion outlet, a temporary sediment trap should be installed.
Maintenance
An earth dike should be inspected for signs of erosion after every major rain event. Any repairs
and/or revegetation should be completed promptly (NAHB, n.d.). The following actions can be
taken to properly maintain an earth dike:
• Remove debris and sediment from the channel immediately after the storm event.
• Repair the dike to its original height.
• Check outlets and make necessary repairs to prevent gully formation.
• Clean out sediment traps when they are 50 percent full.
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f
• Once the work area has been stabilized, remove the diversion ridge, fill and compact the
channel to blend with the surrounding area, and remove sediment traps, disposing of unstable
sediment in a designated area.
Cost
The cost of an earth dike depends on the design and materials used. Small dikes can cost,
approximately $2.00 per linear foot, while larger dikes can cost approximately $2.00 per cubic
yard. EPA states that an earth dike can cost approximately $4.50 per linear foot (NAHB, n.d.).
An alternative means to estimate conceptual costs for earthen dikes is to use unit cost values and
a rough estimate of the quantities needed. Shallow trenching (1 to 4 feet deep) with a backhoe in
areas not requiring dewatering can be performed for $4 to $5 per cubic yard of removed material
(R. S. Means, 2000). Based on this value, $2 per linear foot provides for 11 square feet of flow
area and $4.50 per linear foot provides for 24 square feet of flow area. This suggests that the
size of the dike is required prior to specifying a cost, which requires a site-specific hydrologic
evaluation. Based on standards for Virginia (1992), most small drainage areas (made up of 5
acre or less), diversion dikes are approximately 18" tall, with a 4.5' base. Assuming the
excavation volume equals the volume of the dike, the resulting excavation volume is
approximately 7 cubic feet per linear foot, which (conservatively) equates to $1.03 to $1.30 per
linear foot for construction costs. ;
If the earthen dikes are to be permanent, then additional costs are incurred to vegetate the dike.
R. S. Means (2000) estimates the cost of fine grading, soil treatment, and grassing is •
approximately $2 per square yard of earth surface area. This adds approximately $6 per linear
foot of dike. Where gently sloping areas just need to be grassed with acceptable species, the cost
can be as low as $0.3 8 per square yard. , •
5.1.5.2.2
TEMPORARY SWALE
General Description
The term swale (grassed channel, dry swale, wet swale, biofilter) refers to a series of vegetated,
open channel management practices designed specifically to treat and attenuate storm water
runoff for a specified water quality volume. As storm water runoff flows through these
channels, it is treated by filtering through the vegetation in the channel, filtering through a
subsoil matrix, and/or infiltration into the underlying soils. Variations of the grassed swale
include the grassed channel, dry swale, and wet swale. The specific design features and methods
of treatment differ in each of these designs, but all are improvements on the traditional drainage
ditch and incorporate modified geometry and other features for use of the swale as a treatment
and conveyance practice.
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Applicability
Grassed swales can be applied in most situations with some restrictions and are very well suited
for treating highway or residential road runoff because they are linear practices. Perimeter
dikes/swales should.be limited to a drainage area of no more than 0.8 hectare and usually work
best on gently sloping terrain. Perimeter dikes may not work well on moderate slopes, and they
should never be established on slopes exceeding 20 percent (UNEP, 1994).
• Regional Applicability. Grassed swales can be applied in most regions of the country. In arid
and semi-arid climates, however, the value of these practices needs to be weighed against the
water needed to irrigate them.
Ultra-Urban Areas. Ultra-urban areas are densely developed urban areas in which little
pervious surface exists. Grassed swales are generally not well suited to ultra-urban areas because
they require a relatively large area of pervious surfaces.
Storm Water Hot Spots. Storm water hot spots are areas where land use or activities generate
highly contaminated runoff, with concentrations of pollutants in excess of those commonly
found in storm water. A typical example is a gas station or convenience store. With the
exception of the dry swale design, hot spot runoff should not be directed toward grassed
channels. These practices either infiltrate storm water or intersect the groundwater, making use
of the practices for hot spot runoff a threat to groundwater quality.
Storm Water Retrofit. A storm water retrofit is a storm water management practice (usually
structural), put into place after development has occurred, to improve water quality, protect
downstream channels, reduce flooding, or meet other specific objectives. One retrofit
opportunity using grassed swales modifies existing drainage ditches. Ditches have traditionally
been designed only to convey storm water away from roads as quickly as possible. In some
cases, it may be possible to incorporate features to enhance pollutant removal or infiltration such
as check dams (for example, small dams along the ditch that trap sediment, slow runoff, and
reduce the longitudinal slope). Since grassed swales cannot treat a large area, using this practice
to retrofit an entire watershed would be expensive because of the number of practices needed to
manage runoff from a significant amount of the watershed's land area.
Cold Water (Trout) Streams. Grassed channels are a good treatment option within watersheds
that drain to cold water streams. These practices do not retain water for a long period of time
and often induce infiltration. As a result, standing water will not typically be subjected to
warming by the sun in these practices.
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Design and Installation Criteria
Temporary swales should be designed using standard hydrologic and hydraulic calculations.
Designs should be certified by a professional hydrologist, engineer, or other appropriate
professional.
Perimeter dikes/swales should be established before any major soil-disturbing activity takes
place. Dikes should be compacted with construction equipment to the design height plus 10
percent to allow for settlement. If they are to remain in place for longer than 10 days, they
should be stabilized using vegetation, filter fabric, or other material. Diverted water should be
directed to a sediment trap or other sediment treatment area (UNEP, 1994).
In addition to the broad applicability concerns described above, designers need to consider
conditions at the site level. In addition, they need to incorporate design features to improve the
longevity and performance of the practice, while minimizing the maintenance burden. :
Siting Considerations
t
In addition to considering the restrictions and adaptations of grassed swales to different regions
and land uses, designers must ensure that this management practice is feasible at the site in
question. Depending on the design option, grassed channels can be highly restricted practices
based on site characteristics.
Drainage Area. Grassed swales generally should treat small drainage areas of less than 5 acres.
If the practices are used to treat larger areas, the flows and. volumes through the swale become
too large to design the practice to treat storm water runoff through infiltration and filtration.
Slope. Grassed swales should be used on sites with relatively flat slopes (less than 4 percent).
Runoff velocities within the channel become too high on steeper slopes. This can cause erosion
and does not allow for infiltration or filtering in the swale.
Soils /Topography. Grassed swales can be used on most soils, with some restrictions on the
most impermeable soils. In the dry swale, a fabricated soil bed replaces on-site soils to ensure
that runoff is filtered as it travels through the soils of the swale. :
Groundwater. The depth to groundwater depends on the type of swale used. In the dry swale
and grassed channel options, designers should separate the bottom of the swale from the
groundwater by at least 2 feet to prevent a moist swale bottom or contamination of the '
groundwater. In the wet swale option, treatment is enhanced by a wet pool, which is maintained
by intersecting the groundwater.
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Design Considerations
Although the grass swale has different design variations, including the grassed channel, dry
swale, and wet swale, some design considerations are common to all three. One overriding
similarity is the cross-sectional geometry of all three options. Swales should generally have a
trapezoidal or parabolic cross-section with relatively flat side slopes (flatter than 3:1). Designing
the channel with flat side slopes maximizes the wetted perimeter. The wetted perimeter is the
length along the edge of the swale's cross-section where runoff flowing through the swale is in
contact with the vegetated sides and bottom of the swale. Increasing the wetted perimeter slows
runoff velocities and provides more contact with vegetation to encourage filtering and
infiltration. Another advantage to flat side slopes is that runoff entering the grassed swale from
the side receives some pretreatment along the side slope. The flat bottom of all three should be
between 2 and 8 feet wide. The minimum width ensures an adequate filtering surface for water
quality treatment, and the maximum width prevents braiding, that is, the formation of small
channels within the swale bottom.
Another similarity among all three designs is the type of pretreatment needed. In all three design
options, a small forebay should be used at the beginning of the front of the swale to trap
incoming sediments. A pea gravel diaphragm, a small trench filled with river run gravel, should
be used to pretreat runoff entering the sides of the swale.
Two other features designed to enhance the treatment ability of grassed swales are a flat
longitudinal slope (generally between 1 and 2 percent) and a dense vegetative cover in the
channel. The flat slope helps to reduce the velocity of flow in the channel. The dense vegetation
also, helps reduce velocities, protect the channel from erosion, and act as a filter to treat storm
water runoff. During construction, it is important to stabilize the channel before the turf has
been established, either with a temporary grass cover or with the use of natural or synthetic
erosion control products.
In addition to treating runoff for water quality, grassed swales need to convey larger storms
safely. Typical designs allow the runoff from the 2-year storm (for example, the storm that
occurs, on average, once every 2 years) to flow through the swale without causing erosion.
Swales should also have the capacity to pass larger storms (typically a 10-year storm) safely.
The length of the swale necessary to infiltrate runoff waters can be calculated by using a mass
balance of runoff waters and infiltration waters for a triangular-shaped cross-sectional area.
Design Variations
The following discussion identifies three different variations of open channel practices,
including the grassed channel, the dry swale, and the wet swale.
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Grassed Channel. (Discussed in more length in sub-section 5.5.1.2.1) Of the three grassed
swale designs, grassed channels are the most similar to a conventional drainage ditch, with the
major differences being flatter side slopes and longitudinal slopes and a slower design velocity
for water quality treatment of small storm events. Of all of the grassed swale options, grossed
channels are the least expensive, but they also provide the least reliable pollutant removal. The
best application of a grassed channel is as pretreatment to other structural storm water practices.
One major difference between the grassed channel and most of the other structural practices is
the method used to size the practice. Most water quality practices for storm water management
are sized by volume. This method sets the volume available in the practice equal to the Water
quality volume, or the volume of water to be treated in the practice. The grassed channel, on the
other hand, is a flow rate-based design. Based on the peak flow from the water quality storm
(this varies from region to region but a typical value is the 1-inch storm), the channel should be
designed so that runoff takes, on average, 10 minutes to flow from the top to the bottom|of the
channel. A procedure for this design can be found in Design of Storm Water Filtering Systems
(CWP, 1996). .
Dry Swales. Dry swales are similar in design to bioretention areas. These designs incorporate a
fabricated soil bed into their design. The existing soil is replaced with a sand/soil mix that meets
minimum permeability requirements. An underdrain system is used under the soil bed. This
system is a gravel layer that encases a perforated pipe. Storm water treated in the soil bed flows
through the bottom into the underdrain, which conveys this treated storm water to the storm
drain system. Dry swales are a relatively new design, but studies of swales with a native soil
similar to the man-made soil bed of dry swales suggest high pollutant removal. '
Wet Swales. Wet swales intersect the groundwater and behave similarly to a linear wetland cell.
This design variation incorporates a shallow permanent pool and wetland vegetation to provide
storm water treatment. This design also has potentially high pollutant removal. One
disadvantage of the wet swale is that its use in residential or commercial settings is unpopular
because the shallow standing water in the swale is often viewed as a potential nuisance by
homeowners.
Regional Variations
Cold Climates. In cold or snowy climates, swales may serve a dual purpose by acting as both a
snow storage/treatment and a storm water management practice. This dual purpose is j
particularly relevant when swales are used to treat road runoff. If used for this purpose, Iswales
should incorporate salt-tolerant vegetation, such as creeping bentgrass.
Arid Climates. In arid or semi-arid climates, swales should be designed with drought-tolerant
vegetation, such as buffalo grass. As pointed out in the Applicability discussion, the value of
vegetated practices for water quality needs to be weighed against the cost of water needed to
maintain them in arid and semi-arid regions. '-•
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Effectiveness
Swales act to control peak discharges in two ways. First, the grass reduces runoff velocity,
depending on the length and slope of the swale. Second, a portion of the storm water runoff
volume passes through the swale and infiltrates into the soil. Table 5-9 summarizes grassed
swale pollutant removal efficiencies.
Table 5-9. Grassed Swale Pollutant Removal Efficiency Data
Grassed Swale Removal Efficiencies
Study
Goldberg, 1993
Seattle Metro and Washington
Department of Ecology, 1992
Seattle Metro and Washington
Department of Ecology, 1992
Wang etal., 1981
Dormanetal., 1989
Harper, 1988
Kercher, Landon, and Massarelli,
1983
Harper, 1988
Koon, 1995
Occoquan Watershed Monitoring
Lab, 1983
Yousef et al., 1985
Occoquan Watershed Monitoring
Lab, 1983
Yousef etal., 1985
Occoquan Watershed Monitoring
Lab, 1983
Welborn and Veenhuis, 1987
Yu, Barnes, and Gerde, 1993
Dormanetal., 1989 -
Pitt and McLean, 1986
Oakland, 1983
Dorman et al.. 1989
TSS
67.8
60
83
80
98
87
99
81
67
-100
• -
-50
-
31
0
68
65,
0
33
-85
TP
4.5
45
29
-
18
83
99
17
39
-100
8
' -9.1
-19.5
-23
-25
60
41
-
-25
12
TN
-
-
-
-
-
84
99
40
-
-100
13
-18.2
8
36.5
-25
-
-
0
-
-
NO,
31.4
-25
'-25
-
45.
80
99
52
9
-
11 .
-
2
.-
-25
-
11
-
-
-100
Metals
42-62
2-16
46-73
70-80
37-81
88-90
99
37-69
-35 to 6
-100
14-29
-100
41-90
-100 to 33
0
74
14-55
0
20-58
14-88
Bacteria
-100
—25
-25 .
-
-
-
-
-
-
- '
-
-
-
-
-
.
,
0
0
-
Type
Grassed channel
Grassed channel
Grassed channel
Dry swale
Dry swale
Dry swale
Dry swale
Wet swale
Wet swale
Drainage channel
Drainage channel
Drainage channel
Drainage channel
Drainage channel
Drainage channel
Drainage channel
Drainage channel
Drainage channel
Drainage channel
Drainage channel
Limitations
Common problems associated with swales include excessive erosion along unlined channels
(usually because of excessive grade), erosion or sedimentation at the outlet point, or overtopping
of the dike at low points (UNEP, 1994).
Additional limitations of the grass swale include the following:
• Grassed swales cannot treat a very large drainage area.
• Swales do not appear to be effective at reducing bacteria.
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• Wet swales may become a nuisance because of mosquito breeding.
• If designed improperly (for example, proper slope is not achieved), grassed channels will
have very little pollutant removal.
• A thick vegetative cover is needed for these practices to function properly.
Maintenance
As with any BMP, swales must be maintained to continue functioning as effective pollutant
removal methods. Maintenance may include occasional mowing, fertilizing, and liming., In
addition, any areas that become damaged by erosion should be immediately repaired and
replanted. The swales should be protected from concentrated flows and checked for downstream
obstructions.
Cost [
To produce a conceptual cost approximation, grassed channel construction costs can be
developed using unit cost values. Shallow trenching (1 to 4 feet deep) with a backhoe in areas
not requiring dewatering can be performed for $4 to $5 per cubic yard of removed material
(R. S. Means, 2000). Assuming no disposal costs (i.e., excavated material is placed on either side
of the trench), only the cost of fine grading, soil treatment, and grassing (approximately $2 per
square yard of earth surface area) should be added to the trenching cost to approximate the total
construction cost. Site-specific hydrologic analysis of the construction site is necessary to
estimate the channel conveyance requirement and the desired retention time in the swale. It is
not unusual to have flows on the order of 2 to 4'cfs per acre served. ;
For a design channel velocity of 1 foot per second, the resulting range in the channel cross-
section area can be as low as 2 but as high as 4 square feet per acre drained. If the average
channel flow depth is 1 foot, then the low estimate for grassed channel installation is $0.74 per
square foot of channel bottom per acre served per foot of channel length. The high estimate is
$ 1.48 per square foot of channel bottom per acre served per foot of channel length. j
Table 5-10 summarizes additional costs of grass swales.
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Table 5-10. Average Annual Operation and Maintenance Costs for a Grass Swale
Component
Mowing
General grass
care
Debris/litter
removal
Reseeding/
fertilization
Inspection and
general
administration
TOTAL
Estimated
Unit Cost ($)
0.89/100 m2
8.8/100 m2
0.5 1/m2
0.35/m2
0.74/m2
$ for Swale Size:
0.5 m Deep
0.3m Bottom Width .
3m Top Width
145.0
162.98
93.0
5.9
231.0
638.0
$ for Swale Size:
1 m Deep
1m Bottom Width
7 m Top Width
241.0
274.0
93.0
10.37
231.0
850.0
Comments
Mow 2-3 times per year
Grass maintenance area is (top
width + 3 m) x length
Area revegetated is 1% of
maintenance area per year
Inspection once per year
Source: Ellis, 1998.
5.1.5.2.3
TEMPORARY STORM DRAIN DIVERSION
General Description
A temporary storm drain diversion is a pipe that reroutes an existing drainage system to
discharge flow into a sediment trap Or basin. This practice reduces the amount of sediment-
laden runoff from construction sites that enters waterbodies without treatment. Temporary storm
drain diversions can be used when a permanent storm water drainage system has not yet been
installed. It should be recognized that diversion channels can also be installed but are not
considered in the following discussion.
Applicability
A temporary storm drain diversion should be used to temporarily redirect discharge to a
permanent outfall and should remain in place until the area draining to the storm sewer is no
longer disturbed. Temporary storm drain diversions can also be combined with other structures
and used as a sediment-trapping device when the completion of a permanent outfall has been
delayed; alternatively, a sediment trap can be placed below a permanent outfall to remove
sediment before the final flow discharge.
Design and Installation Criteria
Since the diversion is only temporary, the layout of piping and the overall impact of the
diversion's installation on post-construction drainage patterns must be considered. Once
construction is completed, the temporary diversion should be moved to restore the original
system. The following activities should be done at this time:
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• The storm drain should be flushed before the sediment trap is removed.
• The outfall should be stabilized.
• Graded areas should be restored.
• State or local specifications should be checked for more detailed requirements arid ah
appropriate professional should certify that the design meets local hydrologic and hydraulic
requirements.
Effectiveness
If installed properly to capture the bulk of runoff from a construction site, temporary storm drain
diversions can be effective in reducing the discharge of sediment-laden, untreated water to
waterbodies. When used in combination with other erosion and sediment control practices such
as minhriized clearing or vegetative and chemical stabilization, the level of pollution frorn a
construction site can be substantially reduced or eliminated.
Limitations
V . !
Installation of a temporary storm drain diversion may result in the disturbance of existing storm
drainage patterns. Care must be taken to ensure that the original system is properly restored
once the temporary system is removed. The most common source of problems is excessive
velocity at the outlet. Installation of an outlet stabilization structure is typically required and
may be constructed of riprap, reinforced concrete, geotextile linings, or a combination. ;
Maintenance
Once installed, temporary storm drain diversions require very little maintenance. Frequent
inspection and maintenance of temporary storm drain systems, especially after large storms,
should ensure that pipe clogging does not occur and that runoff from the site is being
successfully diverted. After removal of the temporary diversion, the permanent storm drain
system should be carefully inspected to ensure that drainage patterns have not been altered by
the temporary system. '
Cost
Depending on the size of the construction site, a temporary storm drain diversion can be bostly..
Costs include those associated with materials needed to construct the diversion and sediment trap
or basin (mainly piping, concrete, and gravel), and also labor costs for installation and removal
of the system, all of which may involve excavation, regrading, and inspections. Based on the
variety of conditions that can affect storm drain diversion designs, typical costs per installation
are not presented here. However, site-specific cost estimates can be produced using unit cost
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values along with site-specific quantity estimates. R. S. Means (2000) indicates a range of pipe
costs for surface placement, between $5.00 per linear foot for 4" diameter PVC piping, and $9.20
per linear foot for 10" diameter PVC piping. On construction sites, temporary inlets and outlets
are usually formed by small rock-lined depressions. Assuming 4 cubic yards of crushed rock
(1.5" mean diameter) per opening, an inlet and outlet combine to add approximately $200 per
pipe installation, based on $25 per cubic yard of stone (R. S. Means, 2000).
5.1.5.2.4
PIPE SLOPE DRAIN
General Description
Pipe slope drains are used to reduce the risk of erosion on slopes by discharging runoff to
stabilized areas. Consisting of a metal or plastic flexible pipe if temporary, or pipes or paved
chutes if permanent, these drains are placed from the top to the bottom of a slope to carry surface
runoff from the top to the bottom of a slope that has already been damaged by erosion or is at
high risk for erosion. These drains are also used to drain saturated slopes that have the potential
for soil slides.
Applicability
Temporary slope drains can be used on most disturbed slopes to eliminate gully erosion
problems resulting from concentrated flows discharged at a diversion outlet. Slope drains should
be used as a temporary measure for as long as the drainage area remains disturbed. They will
need to be moved once construction is complete and a permanent storm drainage system is
established. Appropriate restoration measures will then need to be taken, such as adjusting
grades and flushing sediment from the pipe before it is removed (UNEP, 1994).
Design and Installation Criteria
Pipe slope drains can be placed directly on the ground or buried under the surface. The inlet
should be located at the top of the slope and should be fitted with an apron, attached with a water
tight connection. Filter cloth should be placed under the inlet to prevent erosion. Flexible pipes,
which are positioned on top of the ground, should be securely anchored with grommets placed
10 feet on center. The outlet at the bottom of the slope should also be stabilized with riprap.
The riprap should be placed along the bottom of a swale that leads to a sediment-trapping
structure or another stabilized structure.
Slope drain pipe sizes are based on drainage area and the size of the design storm. Pipes should
be connected to a diversion ridge at the top of the slope by covering with compacted fill material
where it passes through the ridge. Discharge from a slope drain should be to a sediment trap,
sediment basin, or other stabilized outlet (UNEP, 1994).
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Pipe slope drains should be installed perpendicular to the contour down the slope, and the design
should be able to handle the peak runoff for the 10-year storm. Recommendations of slope drain
diameter are summarized in Table 5-11 (NAHB, n.d).
Table 5-11. Recommended Pipe/Tubing Sizes for Slope Drains
Maximum Drainage
Area (acres)
0-0.5
0.5
0.75
1.0
1.5
2.5
3.5
5.0
Pipe/Tubing
Diameter*(inches)
12
18
21
24
30
Pipe/Tubing
Diameter11 (inches)
12
18
24
Pipe/Tubing
' Diameter0 (inches)
8
10
12
Individually designed
•UNEP, 1994.
bUSDOT, 1995.
°IDNR,1992.
Recently graded slopes that do not have permanent drainage measures installed should have a
temporary slope drain and a temporary diversion installed. A temporary slope drain used^in
conjunction with a diversion conveys storm water flows and reduces erosion until permanent
drainage structures are installed.
The following are design recommendations for temporary slope drains:
• The drain should consist of heavy-duty material manufactured for the purpose and have
grommets for anchoring at a spacing of 10 feet or less.
• Minimum slope drain diameters should be observed for varying drainage areas.
• The entrance to the pipe should consist of a standard flare end section of corrugated metal.
The corrugated metal pipe should have watertight joints at the ends. The rest of the pipe is
typically corrugated plastic or flexible tubing, although for flatter, shorter slopes, a
polyethylene-lined channel is sometimes used.
• The height of the diversion at the pipe should be the diameter of the pipe plus 0.5 foot.
• The outlet should be located at a reinforced or erosion-resistant location.
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Temporary slope drains should be designed to adequately convey runoff for a desired
frequency storm, typically either 2 years or 10 years depending on local regulations. Both
the size and the spacing can be determined based on the contributing drainage area. Drains
are spaced at intervals corresponding to the specified drainage areas. For larger drainage
areas and critical locations, the drains should be sized on an individual basis (USDOT,
1995).
Slope drains should be constructed in conjunction with diversion berms such that the berms
are not overtopped. At the pipe inlet, the top of the berm should be a minimum of 300
millimeters (11.81 inches) higher than the top of the pipe. The entrance should be
constructed of a standard flared end section or a Tee section if designed properly. The
entrance should be placed in a 150 millimeters (5.90 inches) minimum depressed sump
(USDOT, 1995).
The outlet of the slope drain must be protected with a riprap apron. If the slope drain is
draining a disturbed area and sufficient right-of-way is available, the drain may empty into a
sediment trap (USDOT, 1995). Table 5-12 summarizes slope drain characteristics.
Table 5-12. Slope Drain Characteristics
Capacity
Material
Inlet section
Connection to ridge at top of
slope
Outlet
2-yr frequency, 24-hr-duration storm event
Strong, flexible pipe, such as heavy duty, nonperforated, corrugated plastic
Standard "T" or "L" flared-end section with metal toe plate
Compacted fill over pipe with minimum dimensions, 1.5 ft depth, 4 ft top width, and 6
in higher than ridge
Pipe extends beyond toe of slope and discharges into a sediment trap or basin unless
contributing drainage area is stable
Source: IDNR, 1992.
Effectiveness '.
There is currently no information on the effectiveness of pipe slope drains.
Limitations
The area drained by a temporary slope drain should not exceed 5 acres. Physical obstructions
substantially reduce the effectiveness of the drain. A common slope drain problem is
overtopping of the inlet due to an undersized or blocked pipe, or erosion at the outlet point due to
insufficient protection (UNEP, 1994). Other concerns are failures from overtopping because of
inadequate pipe inlet capacity and reduced diversion channel capacity and ridge height
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Solutions to common problems include the following (IDNR, 1992): .
• Washout - A washout along a pipe due to seepage and piping may be caused by inadequate
compaction, insufficient fill, or installation that may be too close to the edge of the slope.
• Overtopping caused by undersized or blocked pipe - The drainage area may be too large.
• Overtopping caused by improper grade of channel and ridge - A positive grade should be
maintained.
• Overtopping caused by poor entrance conditions and trash buildup at the pipe inlet - Deepen
and widen the channel at the pipe entrance and frequently inspect and clear the inlet. ;
• Erosion at outlet - The pipe should be extended to a stable grade or an outlet stabilization
structure is needed.
• Displacement or separation of pipe - The pipe should be tied down and the joints secured.
Maintenance
Pipe slope drains must be inspected after each significant runoff event for evidence of erosion
and uncontrolled runoff. Any repairs to the drain should be made immediately. Significant
amounts of sediment trapped at the outfall should also be removed in a timely manner and
disposed of properly (NAHB, n.d.).
The following actions should be taken to properly maintain a pipe slope drain (IDNR, 1992):
• Inspect slope drains and supporting diversions once a week and after every storm event.
• Check the inlet for sediment or trash accumulation; clear and restore to proper entrance
condition.
• Check the fill over the pipe for settlement, cracking, or piping holes; repair immediately.
• Check for holes where the pipe emerges from the dike; repair immediately:
• Check the conduit for evidence of leaks or inadequate anchoring; repair immediately.
• Check the outlet for erosion or sedimentation; clean and repair, or extend if necessary.
• Once slopes have been stabilized, remove the temporary diversions and slope drains, and
stabilize all disturbed areas.
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Cost
The cost of pipe slope drains and their installation varies with the design and materials used.
Site-specific cost estimates can be produced using unit cost values with site-specific quantity
estimates. R. S. Means (2000) indicates a range of pipe costs for surface placement between
$5.00 per linear foot for 4" diameter PVC piping, and $9.20 per linear foot for 10" diameter PVC
piping. On construction sites, temporary inlets and outlets are usually formed by small rock-lined
depressions. Assuming 4 cubic yards of crushed rock (1.5" mean diameter) per opening, 'an inlet
and outlet combine to add approximately $200 per pipe installation, based on $25 per cubic yard
of stone (R. S. Means, 2000).
5.1.5.2.5
STONE CHECK DAM
General Description
A check dam is a small temporary barrier or dam constructed across a drainage channel or swale
to reduce the velocity of the flow. By reducing the flow velocity, the erosion potential is
reduced, detention times are lengthened, and more sediments are able to drop out of the water
column. Check dams can be constructed of stone, gabions, treated lumber, or logs
(NAHB, n.d.).
Check dams are inexpensive and easy to install. They may be used permanently if designed
properly to allow a high proportion of sediment in the runoff to settle out and reduce velocity
and may provide aeration of the water (NAHB, n.d.). However, the use of check dams in a
channel should not be a substitute for the use of other sediment-trapping and erosion control
measures. As with most other temporary structures, check dams are most effective when used in
combination with other storm water and erosion and sediment control measures.
Applicability
Check dams are commonly used (1) in channels that are degrading but where permanent
stabilization is impractical because of their short period of usefulness and (2) in eroding channels
where construction delays or weather conditions prevent timely installation of erosion-resistant
linings (IDNR, 1992).
V
Check dams are also useful in steeply sloped swales, in small channels, in swales where
adequate vegetative protection cannot be established, or in swales or channels that will be used
for a short period of time where it is not practical to line the channel or implement other flow
control practices (USEPA, 1993). In addition, check dams are appropriate where temporary
seeding has been recently implemented but has not had time to fully develop and take root. The
contributing drainage area should range from 2 to 10 acres. Check dams should be used only in
small open channels that will not be overtopped by flow once the dams are built and should not
be built in steam channels, either intermittent or perennial (UNEP, 1994).
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Design and Installation Criteria
Check dams can be constructed from a number of different materials. Most commonly, they are
made of rock, logs, sandbags, or straw bales. Rock or stone is often preferred because of its
cost-effectiveness and longevity. Logs and straw bales will decay with time and are not
recommended as they may cause waterway blockage if they fail. When using rock or stone, the
material diameter should be 2 to 15 inches. The stones should be extended 18 inches beyond the
banks, and the side slopes should be 2:1 or flatter. Lining the upstream side of the dam with a
foot of 1- to 2-inch gravel may improve the efficiency of the dam (NAHB, n.d.). Logs should
have a diameter of 6 to 8 inches. Regardless of the material used, careful construction of a check
dam is necessary to ensure its effectiveness. j
The distance between rock check dams will vary depending on the slope of the ditch, with closer
spacing when the slope is steeper. The size of stone used in the check dam should also vary with
the expected design velocity and discharge. As velocity and discharge increase, the rock size
should also increase. For most rock check dams, 3 inches to 12 inches is a suitable stone size.
To improve the sediment-trapping efficiency of check dams, a filter stone can be applied to the
upstream face. A well-graded coarse aggregate that is less than 1 inch in size can be used as a
filter stone.
All check dams should have a maximum height of 3 feet. The center of the dam should be at
least 6 inches lower than the edges. This design creates a weir effect that helps to channel flows
away from the banks and prevent further erosion. Additional stability can be achieved by
implanting the dam material approximately 6 inches into the sides and bottom of the channel
(VDCR, 1995).
When installing more than one check dam in a channel, outlet stabilization measures should be
installed below the final dam in the series. Because this area is likely to be vulnerable to further
erosion, riprap or some other stabilization measure is highly recommended.
Effectiveness
Field experience has shown that rock check dams are more effective than silt fences or straw
bales to stabilize wet-weather ditches (VDCR, 1995). Straw bales have been shown to have vary
low trapping efficiencies and should not be used for check dams. For long channels, check dams
are most effective when used in a series, creating multiple barriers to sediment-laden runoff.
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Limitations
Check dams should not be used in perennial streams unless approved by an appropriate
regulatory agency (USEPA, 1992; VDCR, 1995). Because the primary function of check dams
is to slow runoff in a channel, they should not be used as a stand-alone substitute for other
sediment-trapping devices. Also, leaves have been shown to be a significant problem as they
clog check dams; therefore, increased inspection and maintenance might be necessary in the fall.
Common problems with check dams include channel bypass and severe erosion when
overtopped and ineffectiveness due to accumulated sediment and debris. When designing check
dams, the fact that they will reduce the capacity of a channel to transmit storm water runoff and
thus will need to be sized appropriately should be taken into account (UNEP, 1994). The check
dam may also kill grass linings in the channel if the water level remains high after it rains or if
there is significant sedimentation. In addition, a check dam may reduce the hydraulic capacity of
the channel and create turbulence, which erodes the channel banks (NAHB, n.d.).
Maintenance
Check dams should be inspected periodically to ensure that they have not been repositioned as a
result of storm water flow. In addition, the center of a check dam should always be lower than
its edges. Additional stone may have to be added to maintain the correct height. Sediment
should not be allowed to accumulate to more than half the original dam height. Any required
maintenance should be performed immediately. When check dams are removed, care must be
taken to remove all dam materials to ensure proper flow within the channel. The channel should
subsequently be seeded for stabilization (NAHB, n.d.).
Cost
The cost of check dams varies based on the material used for construction and the width of the
channel to be dammed. In general, it is estimated that check dams constructed of rock cost about
$100 per dam (USEPA, 1992). Brown (1997) estimated rock check dam would cost
approximately $62 per installation, including the cost for filter fabric bedding. Other materials,
such as logs and sandbags, may be a less expensive alternative, but they might require higher
maintenance costs.
5.1.5.2.6 LINED WATERWAYS
General Description
Lined channels convey storm water runoff through a stable conduit. Vegetation lining the
channel reduces the flow velocity of concentrated runoff. Lined channels usually are not
designed to control peak runoff loads by themselves and are often used in combination with
other BMPs such as subsurface drains and riprap stabilization. Where moderately steep slopes
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require drainage, lined channels can include excavated depressions or check dams to enhance
runoff storage, decrease flow rates, and enhance pollutant removal. Peak discharges can be
reduced through temporary detention hi the channel. Pollutants can be removed from storm
water by filtration through vegetation, by deposition, or in some cases by infiltration of soluble
nutrients into the soil. The degree of pollutant removal in a channel depends on the residence
time of the water hi the channel and the amount of contact with vegetation and the soil surface,
but pollutant removal is not generally the major design criterion.
Often construction increases the velocity and volume of runoff, which causes erosion in newly
constructed or existing urban runoff conveyance channels. If the runoff during or after
construction will cause erosion hi a channel, the channel should be lined or flow control
practices instituted. The first choice of lining should be grass or sod since this reduces runoff
velocities and provides water quality benefits through filtration and infiltration. If the velocity in
the channel would erode the grass or sod, riprap, concrete, or gabions can be used (USEPA,
2000). Geotextile materials can be used hi conjunction with either grass or riprap linings ;to
provide additional protection at the soil-lining interface. ;
Applicability
Lined channels typically are used in residential developments, along highway medians, or as an
alternative to curb and gutter systems. Grass-lined channels should be used to convey runoff
only where slopes are 5 percent or less. These channels require periodic mowing, occasional
spot-seeding, and weed control to ensure adequate grass cover (UNEP, 1994).
Lined channels should be used hi areas where erosion-resistant conveyances are needed, such as
hi areas with highly erodible soils and slopes of less than 5 percent. They should be installed
only where space is available for a relatively large cross-section. Grassed channels have a
limited ability to control runoff from large storms and should be used with the recommended
allowable velocities for the specific soil types and vegetative cover.
Design and Installation Criteria
The design of a lined waterway requires proper determination of the channel dimensions. It must
ensure that (1) the velocity of the flowing water will not wash out the waterway and that (2) the
capacity of the waterway is sufficient to carry the surface flow from the watershed without
overtopping.
Vegetative-Lined Channels. Grass-lined channels have been previously discussed in detail and
are only summarized hi this section. The allowable velocity of water in the waterway depends
upon the type, condition, and density of the vegetation, as well as the erosive characteristics of
the soil. Uniformity of vegetative cover is important because the stability of the most sparsely
covered area determines the stability of the channel. Grasses are a better vegetative coverthan
legumes because grasses resist water velocity more effectively. <
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Vegetative-lined channels may have triangular, parabolic, or trapezoidal cross-sections. Side
slopes should not exceed 3:1 to facilitate the establishment, maintenance, and mowing of
vegetation. A dense cover of hardy, erosion-resistant grass should be established as soon as
possible following grading. This may necessitate the use of straw mulch and the installation of
protective netting until the grass becomes established. If the intent is to create opportunities for
runoff to infiltrate into the soil, the channel gradient should be kept near zero, the channel
bottom must be well above the seasonal water table, and the underlying soils should be relatively
permeable (generally, with an infiltration rate greater than 2 centimeters [0.78 niches] per hour).
Rock-Lined Channels. Riprap-lined channels may be installed on somewhat steeper slopes
than grass-lined channels. They require a foundation of filter fabric or gravel under the riprap.
Generally, side slopes should not exceed 2:1, and riprap thickness should be 1.5 times the
maximum stone diameter. Riprap should form a dense, uniform, well-graded mass
(UNEP, 1994).
Lined channels should be sited in accordance with the natural drainage system and should not
cross ridges. The channel design should not have sharp curves or significant changes in slope.
Channels should not receive direct sedimentation from disturbed areas and should be established
only on the perimeter of a construction site to convey relatively clean storm water runoff and
separated from disturbed areas by a vegetated buffer or other BMP to reduce sediment loads.
Basic design recommendations for lined channels include the following:
• Construction and vegetation of the channel should occur before grading and paving activities
. begin. ,
• Design velocities should be below 5 feet per second.
• Geotextiles can be used to stabilize vegetation until it is fully established.
• Covering the bare soil with sod or geotextiles can provide reinforced storm water
conveyance immediately.
• Triangular-shaped channels should be used with low velocities and small 'quantities of
runoff; parabolic grass channels are used for larger flows and where space is available;
trapezoidal channels are used with large flows of low velocity (low slope).
• Outlet stabilization structures might be needed if the runoff volume or velocity has the
potential to exceed the capacity of the receiving area.
• Channels should be designed to convey runoff from a 10-year storm without erosion.
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• The sides of the channel should be sloped less than 3:1, with V-shaped channels along roads
sloped 6:1 or less for safety.
• All trees, bushes, stamps, and other debris should be removed during construction.
Effectiveness :
Lined channels can effectively transport storm water from construction areas if they are designed
for expected flow volumes and velocities and if they do not receive sediment directly from
disturbed areas.
Limitations
Lined channels, if improperly installed, can alter the natural flow of surface water and have
adverse impacts on downstream waters. Additionally, if the design capacity is exceeded by a
large storm event, the vegetation might not be sufficient to prevent erosion and the channel
might be destroyed. Clogging with sediment and debris reduces the effectiveness of grass-lined
channels for storm water conveyance. :
Common problems in lined channels include erosion of the channel before vegetation is; fully
established and gullying or head cutting in the channel if the grade is too steep. In addition, trees
and brush tend to invade lined channels, causing maintenance problems. ;
Riprap-lined channels can be designed to safely convey greater runoff volumes on steeper
slopes. However, they should generally be avoided on slopes exceeding 10 percent because stone
displacement, erosion of the foundation, or channel overflow and erosion resulting from a
channel that is too small can occur. Thus, channels established on slopes greater than 10 percent
will usually require protection with rock gabions, concrete, or other highly stable and protective
surfaces (UNEP, 1994). ;
Maintenance
Maintenance requirements for lined channels are relatively minimal. During the vegetation
establishment period, the channels should be inspected after every rainfall. Other maintenance
activities that should be carried out after vegetation is established are mowing, litter removal,
and spot vegetation repair. The most important objective in the maintenance of lined channels is
maintaining a dense and vigorous growth of turf. Periodic cleaning of vegetation and soil
buildup in curb cuts is required so that water flow into the channel is unobstructed. During the
growing season, channel grass should be cut no shorter than the level of design flow, and the
cuttings should be removed promptly. \
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Cost
Costs of grassed channels range according to depth, with a 1.5-foot-deep, 10-foot-wide grassed
channel estimated at $6,395 to $17,075 per trench, while a 3.0-foot-deep, 21-foot-wide grassed
channel is estimated at $12,909 to $33,404 per trench (SWRPC, 1991)
Readers are also referred to the discussion of costs for grass-lined channels, which contains
many of the design and cost elements required for installing lined waterways. Designers have a
range of options for lining new channels. Geosynthetic turf reinforcement mattings (TRMs) can
be used for immediate erosion protection in channels exposed to runoff flows. The Erosion
Control Technology Council (a geotextile industry support association) suggests TRMs cost
approximately $7.00 per square yard (installed) for channel protection (ECTC, 2002a). R. S.
Means indicates machine-placed riprap costs of approximately $40 per cubic yard. The riprap
maximum size is typically between 6 and 12 inches, depending on the channel design velocity. A
cubic yard of riprap will cover between 36 and 18 square feet of channel bed for these riprap
sizes (assuming depth of riprap is 1.5 times the maximum size). These estimates suggests that
riprap lining will be between $10 and $20 per square foot of channel (Costs include materials,
labor, and equipment, with overhead and profit).
5.1.5.3
SEDIMENT TRAPPING DEVICES
The devices listed under this group of BMPs trap sediment primarily through impounding water
and allowing for settling to occur (Haan et al., 1994). Silt fence, super silt fence, straw bale
dikes, sediment traps, and sediment basins all control flow through a porous flow control system
such as filter fabric or straw bales or they use a dam to impound water with a pipe, open channel,
or rock fill outlet. The filtering capacity of silt fence (filter fabric) contributes only a small
amount of trapping, but serves to make the fence less porous and hence increases ponding . For
steady-state flows, the trapping that occurs behind the flow control device can be shown to be
directly proportional to the surface area and indirectly proportional to flow through the system
(Haan et al., 1994). The ratio of the surface area to flow is known as the overflow rate, and
trapping in such systems is predicted by the ratio of overflow rate to particle settling velocity.
Although flows in nature are inherently non-steady state and more complex than steady-state
systems, studies have shown that the best predictor of trapping in such systems is still the ratio of
settling velocity to overflow rate (Hayes et al., 1984). In the case of non-steady state, the
overflow rate is best defined by the ratio of peak discharge from the system to a surface area
(Hayes et al., 1984; McBurnie et al., 1990).
The amount of trapping in these structures depends on the size of the structure, flow rates into
the system, hydraulics of the flow control system, the size distribution of the sediment flowing
into the structure, and the chemistry of the sediment-water system (Haan et al., 1994). Trapping
can be enhanced by chemical treatment of flows into the structure, but the impacts have not been
widely defined for varying mineralogy and chemistry of the sediment-water system (Haan et al.,
1994; Tapp and Barfield, 1986). Recent studies have been conducted on the application of
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polyacrilamides (PACs) to disturbed areas for enhancing settling (Benik et'al., 1998; Masters et
al., 2000; Roa-Espinosa et al., 2000), but results have not been definitive. No known studies
have evaluated the impacts of PAC application to disturbed areas on settling in sediment
trapping devices. !
Sediment flowing into sediment trapping devices is composed of primary particles and I -
aggregated particles. Aggregates are formed when clays, silts, and sands are cemented together
to form larger particles that have settling velocities far greater than those of any individual
particles alone although the degree of aggregation depends on the amount of cementing material
present (typically clays and organic matter). Since the aggregates have higher settling velocities
than primary particles, the degree of aggregation that is present has a large impact on the;
trapping that occurs. Procedures are available to measure the combined size distribution! of
aggregate and primary particle size distribution (Barfield et al., 1979; Haan et al., 1994).!
Procedures are also available to predict particle size distributions of aggregates and primary
particles (Foster et al., 1985) but have not been found to be very accurate for subsoils exposed
during construction in at least one study (Barfield et al., 1983).
In the absence of chemical treatment, the sediment that can be captured in sediment trapping
devices is typically the settleable solids. To trap the smaller size clay particles, structures with
surface areas larger than the construction site itself would have to built in many cases (Barfield,
2000). Chemical treatment can be used to reduce the size, but it has not been adopted on a wide
scale because of the cost and complexity of the operation (Tapp et al., 1981).
Sediment trapping devices also provide some storm water detention by virtue of detaining flows
long enough to allow sediment to settle out and be deposited. However, to operate as a storm -
water detention structure, the design should include storm water detention as well. ;
Virtually all of the available information on sediment trapping structures, both theoretical and
experimental, is on impacts to receiving waters and not downstream effects, m a very limited
analysis, Barfield (2000) combined the SEDIMOTII computer model together with the
FLUVIAL model to theoretically evaluate the impact of sediment trapping structures on -,
downstream geomorphology in a Puerto Rican watershed. ;
5.1.5.3.1
General Description
SILT FENCE
Silt fences are used as temporary sediment barriers consisting of filter fabric anchored across and
supported by posts. Their purpose is to retain sediment from small disturbed areas by reducing
the velocity of sediment-laden runoff and promoting sediment deposition (Smolen et al., 1998).
Silt fences capture sediment by ponding water and allowing for deposition, not by filtration. Silt
fence fabric first screens silt and sand from runoff, resulting in clogging of the lower part of the
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fence. The pooling water allows sediments to settle out of the runoff. Silt fences work best in
conjunction with temporary basins, traps, or diversions.
Applicability
Silt fences are generally placed at the toe of fills, along the edge of waterways, and along the site
perimeter. The fences should not be used in drainage areas with concentrated and high flows, in
large areas, or in ditches and swales where concentrated flow is present.
The drainage area for the fence should be selected based on design storms and local hydrologic
conditions so that the silt fence is not expected to overtop. A typical design calls for no greater
than l/4 acre per 100 feet offence, but this is highly variable depending on climate. The fence
should be stable enough to withstand runoff from a 10-year peak storm. Table 5-13 lists the
maximum slope length specified by the USDOT. These slope lengths should be based on
sediment load and flow rates. This would mean that the values given below should be adjusted
for climatic conditions instead of "one size fits all" for a silt fence to ensure maximum
effectiveness.
Table 5-13. Maximum Slope Lengths for Silt Fences
Slope (%)
<;2
5
10
20
25
30
35
40
45
50
18- inch (460 mm) Fence
250 ft (75 m)
100 ft (30m)
50 ft (15 m)
25 ft (8 m)
6 m (20 ft)
15 ft (5 m)
15ft(5m)-
15 ft (5m)
10 ft (3m)
10 ft (3m)
30- inch (760 mm) Fence
500 ft (150m)
250 ft (75m)
150 ft (45m)
70 ft (21 m)
55 ft (17 m)
45 ft (14 m)
40 ft (12 m)
35 ft (10 m)
30 ft (9 m)
25 ft (8m)
Source: USDOT, 1995.
Typical standards and specifications call for the silt fence to be located on fairly level ground
and follow the land contour. However, field evaluations by Barfield and Hayes (1992,1999) in
South Carolina and Kentucky indicate that installations on the contour as well as along a slope
have problems with undercutting, hi either case, the installations are such that a slight slope may
occur along the fence hi spite of the best installation practices. Runoff can move down the
contour until a weak spot occurs in the buried toe and undercuts the fence. Alternatively, flow
may move to a low spot where it accumulates and causes an overtopping, hi either case,
trapping by the silt fence is essentially zero, and flows have then been concentrated at a point
causing downslope channel erosion.
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Design and Installation Criteria
Design criteria are of two types: ,
Hydrologic design for a required trapping of sediment and flow rate to pass the design storm.
Selection of appropriate installation criteria such that the silt fence will perform as designed.
Hydrologic Design
Hydrologic design should result in a design that passes the design storm without causing damage
while trapping the required amount of sediment. It is necessary to use either a database or; some
type of model to develop the appropriate hydrologic design. Efforts to model the sediment
trapping that occurs through the use of a silt fence have resulted in models that predict the:
settling in the ponded area upstream from the fence {Barfield et al., 1996; Lindley et al., 1998).
The results from model simulations show that trapping depends primarily on the surface area of
the impounded water and the flow rate through the filter. The models utilize a clear water slurry
flow rate, typically specified by the manufacturer, to predict discharge. However, numerous
studies have shown that sediment laden flows cause clogging of the geotextiles used to construct
the fence, dependent on the opening size and size of the sediment (Britton et al., 2001; Wyant,
1980; Barrett et al., 1995; Fisher and Jarret, 1984). Thus, results from model studies to date are
suspect and need to be modified to account for the impacts of clogging on flow rate. Barfield et
al., (2000) developed a model of flow rate using conditional probability concepts, but the results
have not been experimentally verified.
Design aids have been developed for silt fence, using simulations from the SEDIMOT III model
(Hayes and Barfield, 1995). In the model, predictions are made about trapping efficiency using
the ratio of settling velocity for the dlsl of the eroded sediment, divided by the ratio of discharge
to ponded surface area. The design aids yield conservative estimates as compared to the •
SEDIMOT IK model,-but the database used for generating the design aid is based on the
assumption that clogging does not impact flow rates. The discussion above shows that
assumption to be erroneous.
The bottom line on the discussion above is that it is not possible to predict with any expected
accuracy the trapping efficiency of silt fence under a given set of conditions.
Installation Criteria ;
General installation criteria for the silt fence should incorporate the following factors: ;
'dls:15 percent by weight of suspended solids are smaller than those that are trapped by this device;
Similarly djo indicates that 50 percent by weight of suspended solids are smaller than those trapped.
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• The fabric must have sufficient strength to counter forces created by contained water and
sediment (Sprague, 1999).
• The posts must have sufficient strength to counter the forces transferred to them by the fabric
(Sprague, 1999).
• The fabric must be installed to ensure that the loads are all adequately transferred through the
fabric to the posts or the ground without overstressing (Sprague, 1999).
• The fence must be designed based on site-specific hydrologic and soil conditions such that it
will not overtop during design events.
• The fence must be installed (anchored) with a buried toe of sufficient depth so that it does
not become detached from the soil surface.
• In general, the fence requires a metal wire backing to provide sufficient strength to prevent
failure from the weight of trapped sediment and to prevent the.toe of the fabric from being
removed from the ground.
• Maximum drainage area behind the fence should be determined based on the local rainfall
and the infiltration characteristics of the soil and cover.
Silt fence material is typically synthetic filter fabric or a pervious sheet of polypropylene, nylon,
polyester, or polyethylene yarn. The fabric should have ultraviolet ray inhibitors and stabilizers
to provide for a minimum useful construction life of 6 months or the duration of construction,
whichever is greater. The height of the fence fabric should not exceed 3 feet. If standard
strength filter fabric is used, it should be reinforced with a wire fence, extending down into the
trench that buries the toe. The wire should be of sufficient strength to support the weight of the
deposited sediment and water. In general, a minimum 14 gauge and a maximum mesh spacing
of 6 inches is called for (Smolen et al., 1988). Typical requirements for the silt fence physical
properties, as specified in selected local BMP standards and specifications, are included in Table
5-14.
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Table 5-14. Typical Requirements for Silt Fence Fabric
Physical Property
Filtering Efficiency
Tensile Strength at
20% (maximum)
Elongation
Slurry Flow Rate
Water Flow Rate
UV Resistance
Requirements >
Woven Fabric
85%
Standard Strength — 30
pound/linear inch
Extra Strength — 50 pound/linear
inch
0.3 gallon/square feet/minute
15 gallon/square feet/minute
70%
Non- Woven Fabric '.
85% ;
Standard Strength — 50 pound/linear
inch |
Extra Strength — 70 pound/linear inch
4.5 gallon/square feet/minute
220 gallon/square feet/minute ;
85%
Source: NCDNR, 1988; IDNR 1992. i
It should be pointed out that these numbers, particularly the flow rates, could vary widely
depending on the local soil condition due to possible clogging of the filter material.
Material for the posts used to anchor the filter fabric can be constructed of either wood on steel.
Wooden stakes should be buried at a depth sufficient to keep the fence, when loaded with
sediment and water, from falling over. The depth of burial should depend on soil strength
characteristics when saturated and post diameter. Many standards and specifications set a
minimum length of the post of 5 feet long, and a diameter of 4 inches for posts composed of
softwood (e.g, pine), and 2 niches for posts composed of hardwood (e.g., oak)(Smolen et al.,
1988). Steel posts should also be designed based on local soil strength characteristics when wet.
Some standards and specifications for these posts set a minimum weight of 1.33 pound/linear
feet with a minimum length of 4 feet. Steel posts should also have projections to adhere filter
fabric to the post (Smolen et al., 1988).
A silt fence should be erected in a continuous fashion from a single roll of fabric so as to ;
eliminate unwanted gaps in the fence. If a continuous roll of fabric is not available, the fabric
should overlap from both directions only at posts with a mmirnum overlap of 6 inches and be
rolled together with a special flexible rod to keep the ends from separating. Fence posts should
be spaced at a distance based on wet soil strength characteristics and post size and strength;
generally, the posts are spaced approximately 4 to 6 feet apart. If standard strength fabric is
used in combination with wire mesh, the spacing can be larger. Typically, the standards and
specifications call for the posts to be no more than 10 feet apart. If extra-strength fabric is used
without wire mesh reinforcement, some standards call for the support posts to be spaced no more
than 6 feet apart (VDCR, 1995). Again, this spacing should depend on wet soil strength
characteristics and post size.
A silt fence must provide sufficient storage capacity or be stabilized over flow outlets such that
the storage volume of water will not overtop the fence. The return period event (size of the
rainfall event managed) used for design is typically a prerogative of the regulatory agency, For
temporary fences, a 2-year storm event is typically used as a design standard. Fences that will be
hi place for 6 months or longer are commonly designed based on a 10-year storm event
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(Sprague, 1999). The space behind the fence used for impoundment volume must be sufficient
to adequately contain the sediment that will be deposited. Each storm will deposit sediment
behind the fence, and after a period of time the amount of sediment accumulated will render the
fence useless. Frequency offence management is a function of its sizing (i.e. whether the fence
was installed for a 2-year or a 10-year storm event) (Sprague, 1999) and the amount of erosion
that occurs in the area draining to the fence.
Effectiveness
The performance of silt fences has not been well defined. Laboratory studies using carefully
controlled conditions have shown trapping efficiencies in the range of 40 to 100 percent,
depending on the type of fabric, overflow rate, and detention time (Barrett et al., 1995; Wyant,
1980; Wishowski et al., 1998). Field studies have been limited and quite inadequate; however,
the results show that field-trapping efficiencies are very low. In fact, Barrett et al. (1995)
obtained a value of zero percent trapping averaged over several samples with a standard error of
26 percent. Barrett et al. (1995) cite the following reasons for the field tests not showing the
expected results: '
• Inadequate fabric splices .
• Sustained failure to correct fence damage resulting from overtopping
• Large holes in the fabric
• Uhder-runs due to inadequate "toe-ins"
• Silt fence damaged and partially covered by the temporary placement of stockpiles of
materials
Field inspections conducted by Barfield and Hayes (1992) were made in which more than 50
construction sites in South Carolina and Kentucky were visited. Inspections found that silt fence
was seldom installed and, when installed, was rarely set up according to specifications. In areas
where installations did meet standards, it was obvious that flows sought the weakest spot on the
fence and either flowed through cuts in the fabric, or undercut or overtopped the fence. This
flow was thus changed from the overland flow coming into the site to concentrated flow, causing
significant erosion. •
Silt fences are effective at removing large particle sediment, primarily aggregates, sands, and
larger silts. Sediment is removed through impounding of water to slow velocity. It is argued
that the silt fence will not contribute to a reduction hi small particle sediment and is not effective
against other pollutants (WYDEQ, 1999). EPA (1993) reports the following effectiveness
ranges, for silt fences constructed of filter fabric: average total suspended solids removal of 70
percent, sand removal of 80 to 90 percent, silt-loam removal of 50 to 80 percent, and
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silt-clay-loam removal of 0 to 20 percent. However, the EPA numbers from the Nationwide
Urban Runoff Program should not be considered to apply to every location. i
The actual trapping will vary widely for a given design because of differences in hydrolpgic
regimes and soil types.
The advantages of using silt fences include: minimal labor requirement for installation,: low
cost, high efficiency in removing sediment, durability, and sometimes reuse (Sprague, 1:999).
Silt fences are the most readily available and cost-effective control options where options like
diversion are not possible. Silt fences are also a popular choice; because contractors have used
them extensively, the familiarity makes silt fence use more likely for future construction
activities. The visibility of a silt fence is also an advantage, for the fence is "advertising" the use
of erosion and sediment control structures. In addition, the silt fence visibility makes site
inspection easier for contractors and government inspectors (CWP, 1996). •
Limitations
Silt fences should not be installed along areas where rocks or other hard surfaces will prevent
uniform anchoring offence posts and entrenching of the filter fabric because an insufficient
anchor-will greatly reduce the effectiveness of silt fencing and may create runoff channels
leading off-site. In addition, open areas where wind velocity is high may present a maintenance
challenge, as high winds may accelerate deterioration of the filter fabric (Smolen et al., 1988).
When the pores of the silt fence fabric become clogged with sediment, pools of water ate likely
to form on the uphill side offence. Siting and design of the silt fence should account for this
problem and care should be taken to avoid unnecessary diversion of storm water from these
pools which might cause further erosion damage. Silt fences can act as a diversion if placed
slightly off-contour and can control shallow, uniform flows from small, disturbed areas^and
deliver sediment-laden water to deposition areas. :
Silt fences will sag or collapse if a site is too large, if too much sediment accumulates, if the
approach slope is too steep, or if the fence was not adequately supported. If the fence bottom is
not properly installed or the flow velocity is too fast, fence undercuts or blowouts can occur
because of excess runoff. Erosion around the end of the fence can occur if the fence ends do not
extend upslope to prevent flow around the fence (IDNR, 1992).
Maintenance
Site operators should inspect silt fences after each rainfall event to ensure they are intact and that
there are no gaps at the fence-ground interface or tears along the length of the fence. If gaps or
tears are found, they should be repaired or the fabric should be replaced immediately. |
Accumulated sediments should be removed from the fence base when the sediment reaches
one-third to halfway up the height of the fence. Sediment removal should occur more frequently
if accumulated sediment is creating a noticeable strain on the fabric and there is the possibility
that the fence might fail from a sudden storm event.
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Cost
There is a wide range of data on installation costs for silt fences. EPA estimates these costs at
approximately $6.00 per linear foot (USEPA, 1992) while SWRPC estimates unit costs between
$2.30 and $4.50 per linear foot (SWRPC, 1991). Silt fences have an annual maintenance cost
that is 100 percent of installation cost (Brown et al., 1997). These values are significantly greater
than that reported by R. S. Means (2000), which indicates a 3 foot tall silt fence installation cost
between $0.68 and $0.92 per linear foot (for favorable and challenging installations). It should
be noted that the R. S. Means value covers just a single installation, without the expected costs
of maintenance (e.g., removal of collected sediment). In addition, the type of silt fence fabric
employed will also affect the total installation costs.
5.1.5.3.2
SUPER SILT FENCE
General Description
Super silt fence is a modification of a standard silt fence. The two central differences between
the standard silt fence and the super silt fence is that the super silt fence has toe that is buried
more deeply and the backing material is chain .link fence held in place by steel posts-a concept
that originated in Maryland. The Maryland super silt fence requires a Geotextile Class F fabric
over a chain link fence to intercept sediment-laden runoff from small drainage areas. The super
silt fence provides a barrier that can collect and hold debris and soil more effectively than a
standard silt fence, preventing material from entering critical areas. It is best used where the
installation of a dike would destroy sensitive areas, woods, and wetlands.
Applicability
Super silt fences can be used in the same conditions as a silt fence. Fences should follow the
contour of the land. Table 5-15 lists the distance a super silt fence should be from a slope to
ensure maximum effectiveness (MDE, 1994).
Table 5-15. Slope Lengths for Super Silt Fences
Slope (%)
0-10
10-20
20-33
33-50
50+
Slope Length
Minimum
Unlimited
200 feet
100 feet
100 feet
50 feet
Maximum
Unlimited
1,500 feet
1,000 feet
500 feet
250 feet
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Design and Installation Criteria
As with the standard silt fence, design criteria are of two types, hydrologic design for a required
trapping of sediment and flow rate to pass the design storm and selection of appropriate |
installation criteria such that the" silt fence will perform as designed. :
Hydrologic Design \
Hydrologic design criteria are the same as the criteria for the standard silt fence. i
Installation Criteria , •
The criteria used for the Maryland super silt fence indicate the following, although they have not
been tested with field data:
• The fence should be placed as close to the contour as possible, with no section of the silt
fence exceeding a grade of 5 percent for a distance of more than 50 feet.
• Fabric should be no more than 42 inches in height and should be held in place with a 6-foot
chain link fence.
• Fabric should be attached to the steel pole using wire ties or staples. Fabric should be
securely fastened to the chain link fence with ties spaced every 24 inches at the top arid
midsection. ;
• Fabric should be embedded into the ground at a minimum of 8 inches.
• Edges of fabric should overlap by 6 inches.
Table 5-16 describes the physical properties of Geotextile class F fabric (MDE, 1994).
Table 5-16. Minimum Requirements for Super Silt Fence Geotextile Class F Fabric
Physical Properties
Tension Strength
Tensile Modulus
Flow Rate
Filtering Efficiency
Requirements
50 pound/inch
20 pound/inch
0.3 gallon/tf/minute
75%
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Effectiveness
Performance data have not been collected for super silt fences. The fences have been proposed
for locations within a sensitive watershed, or where site conditions prohibit the use of a standard
silt fence. However, until performance data are collected under field conditions, effectiveness is
speculative.
Limitations
Super silt fences are not as likely to fail structurally as are standard silt fences, but they are more
expensive than standard silt fences.
Maintenance
Maintenance requirements for super silt fences are generally the same as for standard silt fences.
Cost
The cost of the super silt fence is more than the standard silt fence because of deeper burial at the
'toe and the cost of chain linked fencing. R. S. Means (2000) indicates a rental price of $10 to $11
per linear foot of chain linked fence for periods up to 1 year. Overall,- rental is expected for most
construction site installation because rental rates are approximately half the price of permanent
chain link fencing.
5.1.5.3.3
STRAW BALE DIKE
General Description
The straw bale dike is a temporary measure used to trap sediment from small, sloping disturbed
areas. It is constructed of straw bales (not hay bales) wedged tightly together and placed along
the contour downslope of disturbed areas. The bales are placed in a shallow excavation, and the
upslope side is sealed with soil. Stakes are driven through the bales into the soil to help hold the
bales in place. The dike works by impounding water, which allows sediment to settle out in the
upslope area (Haan et al., 1994). Straw bale dikes are recommended for short duration
application and are usually effective for less than 3 months because of rapid decomposition
(USDOT, 1995).
Applicability .
Straw bale dikes are generally placed at the toe of fills to provide for a broad shallow sediment
pool. The dikes should not be used in drainage areas with concentrated and high flows, hi large
areas, or in ditches and swales. The location of the straw bale dike should be fairly level, at least
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10 feet from the toe, and should follow the land contour. Table 5-17 lists the distance a istraw
bale dike should be placed from a slope to ensure maximum effectiveness. !
Table 5-17. Maximum Land Slope and Distances Above a Straw Bale Dike
Land Slope (%)
Less than 2
2-5
5-10
10-20
More than 20
Maximum Distance Above Dam (ft)
100
75
50
25
15
Source: USDOT, 1995. !
Design and Implementation Criteria
Hydrologic Design ' ;'.
Hydrologic design dictates the structure necessary to withstand a storm without causing damage
while trapping the required amount of sediment. Either a database or some type of model are
needed to find the appropriate design. Efforts to model the sediment trapping that occurs in
straw bale dikes have resulted in models that predict the settling in the ponded area upstream
from the fence (Barfield et al., 1996; Lindley et.al., 1998). The results from model simulations
show that trapping depends primarily on the surface area of the impounded water and flqw rate
through the filter. The models utilize a clear water slurry flow rate to predict discharge. It is
anticipated, based on visual observations, that sediment will clog the straw bale barrier, reducing
the slurry flow rate. Thus, results from model studies to date are suspect and need to be',
modified to account for the impact of clogging on flow rate.
Installation Criteria
The USDOT's BMP Manual and the Indiana BMP Manual (IN Manual) calls for bales to be:
• Anchored by driving two 36-inch long (minimum) steel rebars or 2 x 2-inch hardwood stakes
through each bale;
• Sized according to the standard bale size of 14 inches x 18 inches x 35 inches;
• Placed in an excavated trench at least 4 inches deep, a bale's width, and long enough that the
end bales are somewhat upslope of the sediment pool;
• Abutted tightly against each other; and,
• Sized such that impounded water depth should not exceed 1.5 feet.
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The USDOT BMP Manual does not require that straw bale dikes be designed; however, the
Indiana Manual limits the drainage area to % acre per 100 feet of dam and the total drainage area
draining to a straw bale dike to 2 acres.
Effectiveness
The information on performance of straw bale dikes is very limited. In laboratory studies of
bales at varying orientations, Kouwen (1990) found that trapping efficiencies ranged from 60 to
100 percent. Field data on trapping have not been collected; however, visual inspection of sites
indicate that straw bales are not properly installed to prevent flows from undercutting of flowing
between bales (Barfield and Hayes, 1992, 1999). In addition, bales deteriorate rapidly and need
to be replaced frequently. Because of these problems, the use of straw bale dikes as a perimeter
control is not recommended, except in special circumstances. Only 27 percent of Erosion and
Sediment Control (ESC) experts rated the straw bale dike as an effective ESC practice, although
its use was still allowed in half of the communities surveyed (Brown and Caraco, 1997).
Limitations
Straw bale dikes should not be used as a diversion, in streams, in channels, or in areas with
concentrated flow. The bales are not recommended for paved areas because of the inability to
anchor the bales (IDNR, 1992).
Care must be taken to ensure that the bales are not installed in an area where there is a
concentrated flow of runoff, in a drainage area that is too large, or on an excessive slope (IDNR,
1992). Under these conditions, erosion around the end of the bales, overtopping and
undercutting of the bales, and bale collapsing and dislodging are likely to occur. Overtopping
will also occur if the storage capacity is underestimated and where provisions are not made for ._
safe bypass of storm flow (IDNR, 1992). Undercutting will occur if the bales are not
entrenched at least 4 inches and backfilled with compacted soil or were not abutted or chinked
properly. Straw bale dikes are likely to collapse or dislodge if the bales are not adequately
staked, or if too much sediment is allowed to accumulate before cleanout (IDNR, 1992).
Maintenance
For the straw bale dike to be most effective, it is important to replace deteriorated bales when
appropriate.
Cost
The cost of straw bale dikes are relatively low, making their use relatively attractive. R. S.
Means (2000) indicates a staked straw bale unit cost of $2.61 per linear foot (Costs include
materials, labor, and equipment, with profit and overhead).
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5.1.5.3.4
SEDIMENT TRAP
General Description
A sediment trap is a temporary control device used to intercept sediment-laden runoff and to trap
sediment to prevent or reduce off-site sedimentation. It is normally a more temporary type of
structure than a sediment pond and is constructed to control sediment on the construction area
during a selected phase of the construction operation. A sediment trap can be formed by;
excavation and/or embankments constructed at designated locations accessible for cleanqut. The
outlet for a sediment trap is typically a porous rock fill structure, which serves to detain the flow,
but a pipe structure can also be used. A temporary sediment trap may be located in a ]
drainageway, at a storm drain inlet, or at other points of discharge from a disturbed area. They
may be constructed independently or in conjunction with diversions and may be used in most
drainage situations to prevent excessive siltation of pipe structures (USEPA, 1992). !
Applicability
Sediment traps can simplify the storm water control plan design process by trapping sediment at
specific spots at a construction site (USEPA, 1992). They should be installed as early in |the
construction process as possible and are primarily effective as a short-term solution to trapping
sediment from construction sites (WYDEQ 1999). Natural drainage patterns should be nbted,
and sites where runoff from potential erosion can be directed into the traps should be selected.
Traps are most effective when capturing runoff from areas where 2 to 5 acres drain to one
location. Sediment traps should not be located in areas where their failure resulting from excess
storm water-runoff can lead to further erosive damage of the landscape. Alternative diversion
pathways should be designed to accommodate these potential overflows. Traps should be
accessible for clean-out and located so that they do not interfere with construction activity, hi
addition, the traps are easily adaptable to most conditions.
Design and Implementation Criteria
Hydrologic Design \
A sediment trap should be designed to maximize surface area and sediment settling. This will
increase the effectiveness of the trap and decrease the likeliness of backup during and after
periods of high runoff intensity. The design of a trap includes determining the storage volume,
surface area, dimensions of spillway or outlet, and elevations of embankment (USDOT, 1995).
Sediment traps should be designed to meet a 2- year, 24-hour duration storm event, but the
selection of a return period varies among regulatory agencies (EDNR, 1992).
Storage volume is created by a combination of excavation of land and construction of an
embankment to detain runoff (USDOT, 1995). Trap storage volume and length of spillway are
determined as a function of the runoff volume and rate for the design storm. These parameters
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will vary depending on return period rainfall and watershed hydrologic characteristics. Some
standards specify a storage volume per acre disturbed. For example, Smolen et al. (1998)
specified that approximate storage capacity of each trap should be at least 67 cubic yards per
acre disturbed draining into the trap, but more recent guidelines suggest 134 cubic yards per acre
of drainage area (VDCR, 2001). Any national standard, however, should be based on runoff
volume and peak discharge in order to be generally applicable. Local regulations can translate
this into applicable volume and area standards.
A more important criterion than storage volume relates to sediment trapping. If a trapping
efficiency is specified, as in the case of South Carolina (SCDHEC, 1995), it is necessary to
design for trapping efficiency. If a TSS or settleable solids effluent criterion is adopted
(SCDHEC, 1995), settleable solids must be estimated. In both cases, a national standard should
address how to estimate trapping efficiency or settleable solids. Efforts to model the sediment
trapping that occurs in sediment traps have resulted in models that predict the settling in the '
ponded area (Barfield et al., 1996; Lindley et al., 1998). The results from model simulations
show that trapping depends primarily on surface area of the impounded water and flow rate
through the rock fill outlet. In fact, the ratio of peak outflow rate to surface area is the best
simple predictor of trapping. The models utilize a modification of the Herrera and Felton (1991)
relationship developed by Haan et al. (1994) to predict discharge rates. The predicted flow rates
do not take into account clogging that can occur in rock fill.. No models or procedures are
available to estimate this clogging or its impact on flow criteria.
Design aids have also been developed for sediment traps, using simulations from the
SEDIMOT HI (Barfield et al., 2001; Hayes et al., 2001). In the model, predictions are made of
trapping efficiency using the ratio of settling velocity for the d15 of the eroded sediment, divided
by the ratio of discharge to ponded surface area. The design aid yields conservative estimates,
but the database used for generating the design aid is based on the assumption that flow rates are
not impacted by clogging. This latter assumption is not likely to be a critical issue, but should be
addressed in future research.
Installation Specifications
USDOT standards call for the embankment to be constructed of compacted earth, at a maximum
height of 5 feet (1.5 meters), a width of 4 to 5 feet (1.2 meters), and side slopes of 2:lor flatter.
These values may change as a result of local criteria and with changing soil characteristics.
Temporary vegetation should be applied to the embankment (USDOT).
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Two types of outlet structures are typically used for sediment traps, a rock outlet and a pipe
outlet. Spillways of large stones or aggregate are the most common type of outlet designed for
sediment traps. The crest of the spillway should be constructed 1 foot below the top of the
embankment and the spillway depth 1.5 feet below the top of the embankment Weir length of
the spillway is determined based on the contributing drainage area (Table 5-18) (USDOT, 1995),
The outlet apron should be a minimum of 5 feet long, and situated on level ground with a filter
fabric foundation to ensure exit velocity of drainage to receiving stream is nonerosive (IDNR,
1992).
The length of the rock outlet should be determined based on peak discharge required and rock
characteristics, typically rock diameter. Flow rate calculations can be made with the relationship
of Herrera and Felton (1991) as modified by Haan et al. (1994). Alternatively, the USDOT has
specified the weir length for a given drainage area as shown in Table 5-18. However, the values
should be adjusted for each climatologic area to account for local hydrologic and return period
rainfall.
Table 5-18. Weir Length for Sediment Traps
Contributing.
Drainage Area
1
2
3
4
5
Weir Length (ft)
4
5
6
10
12
Source: USDOT, 1995.
The pipe outlet, constructed of corrugated metal or PVC pipe riser, is an alternative to the rock
outlet. Pipe diameter is based on the peak discharge rate required. To obtain appropriate;
freeboard, the top of pipe should be placed 1.5 feet below embankment elevation. Perforated
pipe is sometimes used. USDOT suggests perforations of 1- inch (25 mm) diameter holes or
0.5 x 6 inch (13x15 mm) slits in the upper two-thirds of the pipe; however, the discharge should
be calculated for this pipe specification to ensure that it matches the required peak discharge.
The pipe should be placed vertically and horizontally above wet storage elevation
(USDOT, 1995). Riprap should be used as an outlet protection and placed at the outlet of the
barrel to prevent scour from occurring (USDOT, 1995). A stable channel should be provided to
convey discharge to the receiving channel(USDOT, 1995). |
Effectiveness
If it is assumed that the flow can be accurately controlled by the rock fill outlet, sediment traps
should operate as effectively as sediment basins, with trapping efficiencies reduced as a result of
smaller surface areas. The NURP study (USEPA, 1993), Stahre and Urbonas .(1990), and
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Haan, et al., (1994), report that sediment basins effectively trapped sediment and chemical as
shown in Table 5-19. .
Table 5-19. Range of Measured Long-Term Pollutant Removal for
Sediment Detention Basins
Item
Total suspended solids (TSS)
Total phosphorus (TP)
Nitrogen
Organic matter
Lead
Zinc
Hydrocarbons
Bacteria
Removable Percentage
50-70
10-20
10-20
20-40
75-90
30-60
50-70
50-90
Source: Stahre and Urbonas, 1990.
Information on the actual effectiveness of sediment trapsis limited. The discussion should start
first with the flow hydraulics of the rock fill outlet typically employed as a principal spillway for
sediment traps. Procedures for estimating flow through rock fill have been developed by Herra
and Felton (1991) to estimate flow as a function of average rock diameter, standard deviation of
rock size., and flow length. If these parameters could be controlled in an actual situation, the
flow could be accurately predicted. However, given that standard construction practices consist
of end-dumping the rock fill in place, one would expect little correlation between design and
construction and the actual discharge and trapping efficiency would be expected to be '
dramatically different from the design. This analysis does not mean that sediment traps are
ineffective, but that a given design could not be guaranteed to meet the effluent criteria, even
though the predictions indicate compliance. Sediment trapping efficiency is a function of
surface area and inflow rate (Smolen, 1988). Those traps that provide pools with large length-to-
width ratios have a greater chance of success.
Sediment traps remove larger size sediment, primarily sized from silt to sands, by slowing water
velocity and allowing for sediment settling in ponded water (Haan et al., 1994). Although
sediment traps allow for settling of eroded soils, because of their short detention periods for
storm water they typically do not remove fine particles such as silts and clays without chemical
treatment. Sediment settling ability is related to the square of the particle size; halving particle
sizes quadruples the time needed to achieve settlement (WYDEQ 1999). To increase overall
effectiveness, traps should be constructed in smaller areas with low slopes.
Sediment traps are typically designed to remove only sediment from surface water, but some
non-sediment pollutants are trapped as well (Haan et al., 1994).
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Limitations
Common concerns associated with sediment traps are included in Table 5-20.
Table 5-20. Common Concerns Associated with Sediment Traps
Common Concern
Inadequate spillway size
Omission or improper installation of geotextile fabric
Low point in embankment caused by inadequate
Stone outlet apron does not extend to stable grade
Inadequate vegetative protection
Inadequate storage capacity
Contact slope between stone spillway and earth
embankment too steep
Outlet pipe installed in vertical side of trench
Corrugated tubing used as outlet pipe
Result
Results in overtopping of the dam and possible failure
of the structure
Results in piping under the sides or bottom of the stone
and outlet section
Results in overtopping and possible failure ;
Results in erosion below the dam
Results in stone displacement
Results in erosion of embankment
Caused by sediment not being removed from the basin
enough
Results in piping failure ;
Results in piping failure of embankment
Results in crushed pipe and inadequate outlet capacity
Source: IDMR, 1992.
Maintenance
The primary maintenance consideration for temporary sediment traps is the removal of j
accumulated sediment from the basin, which must be done periodically to ensure the continued
effectiveness of the sediment trap. Sediments should be removed when the basin reaches
approximately 50 percent sediment capacity.
A sediment trap should be inspected after each rainfall event to ensure the trap is draining
properly. Inspectors should also check the structure for damage from erosion or piping. 'The
depth of the spillway should be checked and maintained at a minimum of 1.5 feet below the low
point of the trap embankment
Cost
The cost of installing temporary sediment traps ranges from $0.20 to $2.00 per cubic foot of
storage (about $1,100 per acre of drainage). For a recent national assessment, USEPA (1999)
estimated the following costs for sediment traps, which vary as a function of the volume ;of
storage: $513 for 1,800 cubic yards, $1,670 for 3,600 cubic yards, and $2,660 for 5,400 cubic
yards. In addition, it has been reported that a sediment trap has an annual maintenance cdst of 20
percent of installation cost (Brown et al., 1997).
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5.1.5.3.5
SEDIMENT BASINS
General Description
A sediment basin is a storm water detention structure formed by constructing a dam across a
drainageway or excavating a storage volume at other suitable locations and using it to intercept
sediment-laden runoff. Sediment basins are generally larger and more effective in retaining
sediment than temporary sediment traps and typically remain active throughout the construction
period. Jurisdictions that require postdevelopment flow to be less than or equal to
predevelopment flow during construction may employ the designed detention facilities as a
temporary sediment basin during construction.
When sediment basins are designed properly, they can control sediment pollution through the
following functions (Faircloth, 1999):
• Sediment-laden runoff is caught to form an impoundment of water and create conditions
where sediment will settle to the bottom of the basin.
• Treated runoff is released with less sediment concentration than when it entered the basin.
• Storage is provided for accumulated sediment, and resuspension by subsequent storms is
limited.
Applicability
Sediment basins should be located at a convenient concentration point for sediment-laden flows
(NCDNR, 1988). Ideal sites are areas where natural topography allows a pond to be formed by
constructing a dam across a natural swale; such sites are preferred to those that require
excavation (Smolen et al., 1998). - .
Sediment basins are also applicable in drainage areas where it is anticipated that other erosion
controls, such as sediment traps, will not be sufficient to prevent off-site transport of sediment.
Choosing to construct a sediment basin with either an earthen embankment or a stone/rock dam
will depend on the materials available, location of the basin, and desired capacity for storm water
runoff and settling of sediments.
Rock dams are suitable where earthen embankments would be difficult to construct or where
riprap is readily available. Rock structures are also desirable where the top of the dam structure
is to be used as an emergency overflow outlet. These riprap dams are best for drainage areas of
less than 50 acres. Earthen damming structures are appropriate where failure of the dam will not
result in substantial damage or loss of property or life. If properly constructed, sediment basins
with earthen dams can handle storm water runoff from drainage basins as large as 100 acres.
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Design and Implementation Criteria
Hydrologic Design !
A sediment basin can be constructed by excavation or by erecting an earthen embankment across
a low area or drainage swale. Sediment basins can be designed to drain completely during dry
periods, or they can be constructed so that a shallow, permanent pool of water remains between
storm events. Depending on the size of the basin constructed, the basin may be subject to
additional regulation, particularly state and federal regulations related to dam safety.
Sediment basins can be used for any size watershed, but the U.S. Department of Transportation
recommends a drainage area range of 5 to 100 acres (USDOT, 1995). Components of a sediment
basin that must be considered in the hydrologic design include the following (Haan et al., 1994):
• A sediment storage volume sized to contain the sediment trapped during the life of the
structure or between cleanouts.
• A permanent pool volume (if included) above the sediment storage to protect trapped
sediment and prevent resuspension as well as providing a first flush of discharge that has
been subjected to an extended detention period. !
• A detention volume that contains storm runoff for a period sufficient to trap the necessary
quantity of suspended solids.
• A principal spillway that can be a drop-inlet pipe and barrel, a trickle tube, or other type of
controlled release structure.
• An emergency spillway that is designed to handle excessive runoff from the rarer events and
prevent overtopping. \
• The following recommended procedures for conducting the hydrologic design are summarized
from Haan etal. (1994). ;
Sediment Storage Volume. This volume should be sufficient to store the sediment trapped
during the life of the structure or between cleanouts. Sediment storage volume can be calculated
based on 'sediment yield using relationships such as the Revised Universal Soil Loss Equation
with an appropriate delivery ratio (Renard et al., 1994) or a computer model such as !
SEDMOT III (Barfield et al., 1996). Many design specifications, however, base the sediment
storage volume on a volume per acre disturbed. This volume is highly site-specific, depending
on rainfall distributions, soil types, and construction techniques. It is recommended that care be
exercised in developing appropriate values to be sure that existing variations in rainfall
throughout a state or region are incorporated in the statutory requirements.
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Permanent Pool Volume. Providing a first flush of discharge that has been subjected to an
extended detention period can help to minimize degradation of water quality and justify some
permanent pool. The recommended capacity of the permanent pool varies with the regulatory
agency. The U.S. Department of Transportation, for example, recommends 67 cubic yards per
acre (126 mVha) (USDOT, 1995). If an effluent criterion such as allowable peak TSS or peak
settleable solids is used, the final design of both permanent pool and detention volume should be
selected only after using a computer model to predict the expected peak effluent concentrations.
Detention Volume. Storm runoff must be contained for a period of time sufficient to trap the
necessary quantity of suspended solids. Since inflow is occurring simultaneously with outflow,
the detention time for each plug of flow is different and should be considered individually. The
size of the detention volume, as stated above, should also be developed in concert with
determining the size of the permanent pool volume as well as the size of the principal spillway.
When effluent TSS and settleable solids criteria are used, the size of the detention volume and
permanent pool volume should be determined through, on a computer model calculation of
expected effluent concentrations for a given design. The return period used to size the detention
volume depends on the regulatory agency, but a return period of 10 years is typical.
Principal Spillway. The principal spillway is a hydraulic outlet structure sized to provide the
appropriate outflow rate to meet the effluent or trapping efficiency criteria. The principal
spillway should have a dewatering device that slowly releases water contained in the detention
storage over an extended period of time and at a rate determined to trap the required amount of
sediment and/or provide for the appropriate effluent concentration in the design storm. The
more common outlet structures are the drop-inlet structure and the trickle tube. Sizing of the
principal spillway should follow standard hydrologic and sedimentology design procedures but
sizing the structure to simply pass the design storm is inappropriate and will not result in
meeting an effluent or trapping efficiency standard. The size to be used in a given structure
should be determined based on the effluent or trapping efficiency standard being targeted and
site-specific hydrologic and soil conditions. Appropriate design will require the use of a
computer model such as SEDIMOT in (Barfield et al., 1996) or design aids such as those
developed for South Carolina (Hayes and Barfield, 1995). In general, the design is developed to
maximize surface area, which will minimize peak discharge. Since failure of the dam could
result in downstream damage, the design should be done and certified by a licensed engineer
with expertise in hydrologic computation.
It has been proposed that a surface skimmer made of PVC, aluminum, or stainless steel and
designed to prevent trash from clogging and can also be used to replace conventional principal
spillways. The skimmer puts the basin drain just below the water surface, allowing for a
constant head rather than variable head from the bottom. It is proposed that the skimmer allows
water to be released from the top of the basin, which would be the cleanest water, and that the
skimmer properly regulates the fill and draining of the basin (Fairchild, 1999). The skimmer
floats on the surface of the basin and rises as water in the basin rises during the storm. After the
storm the skimmer slowly releases water from the basin. As the basin drains, the skimmer
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settles to the bottom, draining the entire pool except for a pool directly under the skimmer. The
skimmer can be attached directly to an outlet pipe that drains through the dam or can be attached
to an outlet pipe through a riser. It is important to point out that use of the skimmer is ,
controversial and not universally recognized as a good concept. Conventional hydraulic flow
theory would not concur with the statement that the flow would come only from the surface,
unless the pond had significant thermal gradients preventing flow from deeper levels. A single
hole placed just above the sediment cleanout level can also dewater the basin slowly.
Emergency Spillway. Since overtopping of the dam can cause failure and downstream damage,
an emergency spillway is necessary to handle excessive runoff from the rarer events and prevent
overtopping. The design storm for the emergency spillway will depend on the hazard \
classification of the sediment basin. Typical return periods vary between 25 and 100 years, with
25 years recommended by the USDOT. Sizing of the emergency spillway is typically
accomplished to simply transmit the rare event without eroding the base of the spillway.
Procedures for making the hydrologic and hydraulic computations are summarized in Haan et al.
(1994). Again, since failure of the dam could result in downstream damage, the design should
be done and certified by a licensed engineer with expertise in hydrologic computation.
Installation Criteria
The embankment for permanent sediment basins should use standard geotechnical construction
techniques. The fill is typically constructed of earthen fill material placed and compacted in
continuous layers over the entire length of the fill. USDOT recommends 6- to 8- inch layers
(USDOT, 1995). The embankment should be stabilized with vegetation after construction of the
basin. A cutoff trench should be excavated along the centerline of the dam to prevent excessive
seepage beneath the dam, and sized using standard geotechnical computations. USDOT
recommends that a minrmum depth of the cutoff trench should be about 2 feet (600 mm), the
height should be to the riser crest elevation, the minimum bottom width should be 4 feet (1.2 m)
or wide enough for compaction equipment, and slopes should be no steeper than 1:1. ',
Sediment basins can also be constructed with rock dams in a design that is similar to a sediment
basin with an earthen embankment. It is important to remember that rock fill is highly '
heterogeneous and that flow rates calculated with any available procedure are not likely to match
those that will actually occur. Since sediment trapping is inversely proportional to flow r^te, the
trapping efficiency will be impacted significantly. No data are available to determine the
variability of rock fill in actual installations so that confidence intervals can be placed on .
predicted flow rates. Such data should be collected and the confidence intervals calculated prior
to recommending the use of rock dams as outlets on any structures other than sediment traps.
Effectiveness
The effectiveness of a sediment basin depends primarily on the sediment particle size and the
ratio of basin surface area to inflow rate (Smolen et al., 1998; Haan et al., 1994). Basins with a
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large surface area-to-volume ratio will be most effective. Studies by Barfield and Clar (1985)
showed that a surface area-to-peak discharge ratio of 0.01 acres per cubic square foot would trap
more than 75 percent of the sediment coming from the Coastal Plain and Piedmont regions in
Maryland. This efficiency might vary for other regions of the country and should not be used as
a national standard. Studies by Hayes et al. (1984) and Stevens et al. (2001), however, show that
similar relationships can be developed for other locations.
Laboratory data collected on pilot-scale facilities are available on the trapping efficiency of
sediment basins, on effluent concentrations, on dead storage and flow patterns, and on the
impacts of chemical fiocculants on sediment trapping (Tapp et al., 1981; Wilson et al., 1984;
Griffin et al., 1985; Jarrett et al., 1999; Ward et al., 1977, 1979). In general, the laboratory
studies show that pilot-scale ponds can be expected to trap from 70 to 90 percent of sediment,
depending on the sediment characteristics, pond volume, and flow rate. The trapping efficiency
and effluent concentration are, in general, related to the overflow rate and can be reasonably well
predicted using a plug flow model (Ward et al., 1977, 1979) and a Continuously Stirred Tank
Reactor (CSTR) model (Wilson et al., 1982; Wilson et al., 1984). Extensive field-scale data are
-available on long term trapping efficiency in storm water detention basins (Brune, 1953) in
which the annual trapping efficiency is related to the annual capacity inflow ratio of the basin.
These structures are not representative of those used for sediment ponds, but would be
representative of those used for regional detention. A more limited database is available on
single storm sediment trapping in the larger structures (Ward, et al., 1979) and on a field
laboratory structure at Pennsylvania State University (Jarret et al., 1999).
For maximum trap efficiency, Smolen et al. (1988) recommend the following:
• Allow the largest surface area possible, maximize the length-to-width ratio of the basin to
prevent short circuiting, and ensure use of the entire design settling area;
• Locate inlets for the basin at the maximum distance from the principal spillway outlet;
• Allow the maximum reasonable time to detain water before dewatering the basin; and,
• Reduce the inflow rate into the basin and divert all sediment-free runoff.
Jarett (1999) has shown that the smaller the depth of the basin, the more sediment is discharged.
A 0.15 m (0.49 ft) deep basin lost twice as much sediment as a 0.46 m (1.50 ft) deep basin.
Jarrett also found that the performance of a sediment basin will increase with the use of a
skimmer in the principal spillway. The sediment discharged was 1.8 times greater with just a
perforated riser than with a skimmer in the principal spillway. In addition, increasing the de-
watering time, which will allow for more sediment deposition, decreases the sediment loss from
the basin (Jarett, 1999).
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Limitations
Neither a sediment basin with an earthen embankment nor a rock dam should be used in areas of
continuously running water (live streams). The use of sediment basins is not intended for areas
where failure of the earthen or rock dam will result in loss of life, or damage to homes or other
buildings. In addition, sediment basins should not be used in areas where failure will interfere
with the use of public roads or utilities.
Because sediment basins are usually temporary structures, they are often designed poorly and
rarely receive the adequate attention and maintenance. As a result, these basins will not achieve
the function for. which they were designed, especially when conventional outlets cannot property
meter outflow to create an impoundment, thus allowing rapid release of sediment laden water
from the bottom of the basin to escape (Faircloth, 1999). i
Common concerns associated with sediment basins are included in Table 5-21. ;
Table 5-21. Common Concerns Associated with Sediment Basins
Common Concern
Piping failure along conduit
Erosion of spillway or embankment slopes
Slumping or settling of embankment
Bank failure due to slumping
Erosion and caving below principal spillway
Basin not located properly for access
Sediment not properly removed
Lack of anti-flotation
Principal and emergency spillway on design
plans
Safety or health hazard from pond water
Principal spillway too small
Result
Caused by improper compaction, omission of anti-seep collar,
leaking pipe joints, or use of unsuitable soil i
Caused by inadequate vegetation or improper grading and
sloping
Caused by inadequate compaction or use of unsuitable soil
Caused by steep side slopes
Caused by inadequate outlet protection
Results in difficult, ineffective, and costly maintenance
Results in inadequate storage capacity and potential \
resuspension
Results in the riser and barrel being blocked with debris
Results in improper disposal of accumulated sediment .
Caused by gravel clogging the dewatering system :
Results infrequent operation of emergency spillway and ,
increased erosion potential
Source: IDNR, 1992. ;
!
Maintenance :
Routine inspection and maintenance of sediment basins is essential to their continued
effectiveness. Basins should be inspected after each storm event to ensure proper drainage from
me collection pool and determine the need for structural repairs. Erosion from the earthen
embankment or stones moved from rock dams should be replaced immediately. ;
Sediment basins must be located in an area that is easily accessible to maintenance crews for
removal of accumulated sediment. Sediment should be removed from the basin when its storage
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capacity has reached approximately 50 percent. Trash and debris from around dewatering
devices should be removed promptly after rainfall events.
Cost
The sediment basin has a 25 percent annual maintenance cost as a percentage of installation
(Brown et al., 1997).
If constructing a sediment basin with less than 50,000 cubic feet of storage space, the cost of
installing the basin ranges from $0.20 to $1.30 per cubic foot of storage (about $1,100 per acre
of drainage). The average cost for basins with less than 50,000 cubic feet of storage is
approximately $0.60 per cubic foot of storage (USEPA, 1993).
If constructing a sediment basin with more than 50,000 cubic feet of storage space, the cost of
installing the basin ranges from $0.10 to $0.40 per cubic foot of storage (about $550 per acre of
drainage). The average cost for basins with greater than 50,000 cubic feet of storage is
approximately $0.30 per cubic foot of storage (USEPA, 1993).
As an alternative costing method, designers can use cost curves developed for permanent basins
used to manage storm water from urban areas. However, since permanent storm water basins
• typically include design features that would not be included in temporary sediment basins, this
approach is expected to greatly overestimate the actual costs to construct sediment basins. For
many sites, sedimentation basins installed for erosion and sediment control during the
construction phase are retained/modified to meet other runoff management requirements. For
example, site flood prevention requirements for the 10-year rainfall event can be met with a
pond made from a converted sedimentation basin. As a result, sedimentation basins installation
costs are partially offset by a later cost reduction or savings. Work by the Center for Watershed
Protection (CWP, 1996), provides capital cost equations for different types of sediment basins
for permanent installations. For example,
dry extended duration ponds
CC = 8.16 (Vs) A 0.78
and for all ponds regardless of type (including wet ponds) - . •
CC = 20.18 (Vs) A 0.70
Where:
. CC = base construction cost, not including design, engineering, and contingencies
Vs = Storage volume below the crest of the emergency spillway, in cubic feet
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Design, engineering, and contingency costs are given as approximately 32 percent of the base
construction costs. Base construction costs for permanent ponds are composed of approximately
48 percent excavation/grading cost, 36 percent control structure cost, and 16 percent .
appurtenances cost. R. S. Means (2000) suggests the cost to remove the eroded sediment;
collected in a small basin during construction is approximately $4 per cubic yard (value includes
a 100 percent surcharge for wet excavation). Disposal of material on-site will be an additional
cost that can only be computed from site-specific conditions. The cheapest management of
dredge material is application to land areas adjacent to the basin, followed with application of a
vegetative cover.
5.1.5.4
5.1.5.4.1
Description
OTHER CONTROL PRACTICES
STONE OUTLET STRUCTURE
A stone outlet structure is a temporary stone dike installed in conjunction with and as a part of an
earth dike. The purpose of the stone outlet structure is to impound sediment-laden runoff,
provide a protected outlet for an e'arth dike, provide for diffusion of concentrated flow, and allow
the area behind the dike to dewater slowly. The stone outlet structure can extend across the end
of the channel behind the dike or be placed in the dike itself. In some cases, more than one stone
outlet structure can be placed in a dike.
Applicability
Stone outlet structures apply to any point of discharge where there is a need to discharge runoff
at a protected outlet or to diffuse concentrated flow for the duration of the period of construction.
The drainage area to this practice is typically limited to one-half acre or less to prevent excessive
flow rates. The stone outlet structure should be located so as to discharge onto an already
stabilized area or into a stable watercourse. Stabilization should consist of complete vegetative
cover and paving, sufficiently established to be erosion resistant. ;
Design and Installation Criteria
Design criteria are of two types, hydrologic design for a required trapping of sediment and/or
flow rate to pass the design storm; and selection of appropriate installation criteria such that the
stone outlet will perform as designed ;
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Hydrologic Design
The hydrologic design should be based on the design storm and standard hydraulic calculations
and should include the following considerations:
• Design Rainfall and Design Storm. The design storm should be specified by the regulatory
authority. Typically a return period of 2 to 5 years is used. Runoff rates should be calculated
with standard hydrologic procedures, as allowed by the regulatory authority.
• Drainage Area. The drainage area to this structure is typically limited to less than half an acre
to ensure that the flow rates are not excessive.
• Length of Crest and Height of Stone Fill. The crest length and height of stone fill should be
of sufficient size to transmit the design storm without overtopping. The volume of water
stored behind the dike can be estimated, but would require a routing of the storm flow in the
design storm. Flow through the stone outlet can be calculated using the relationships of
Herrera and Felton (1991) as modified by Haan et.al. (1994). The height of the fill should be
small enough to prevent excessive flow velocities through the stone fill and. prevent
undercutting! ' •
• Outlet Stabilization. The discharge from the stone outlet should be stabilized with vegetated
waterways or riprap until the flow reaches a stable channel. Design of the stabilized outlet
should follow procedures presented earlier.
Installation Criteria Specifications
A stone outlet structure should conform to the following specifications:
• The outlet should be composed of 2- to 3- inch stone or recycled concrete equivalent is
preferred, but clean gravel may be used if stone is not available.
• The crest of the stone dike should be at least 6 inches lower than the lowest elevation of the
top of the earth dike and should be level.
• The stone outlet structure should be embedded into the soil a minimum of 4 inches.
• The minimum length of the crest of the stone outlet structure should be 6 feet.
• The baffle board should extend 1 foot into the dike and 4 inches into the ground and be
staked in place.
• The drainage area to this structure should be less than half an acre.
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5.1.5.4.2
ROCK OUTLET PROTECTION
Description :
Rock outlet structures are rocks that are placed at the outfall of channels or culverts to reduce the
velocity of flow in the receiving channel to nonerosive rates.
Applicability
This practice applies where discharge velocities and energies at the outlets of culverts are •
sufficient to erode the next downstream reach and it applicable to outlets of all types such as
sediment basins, storm water management ponds, and road culverts.
Design and Installation Criteria
Hydrologic Design
Hydrologic design consists primarily of selecting the design runoff rate and sizing the outlfet
protection. Standard hydrologic calculations should be used to make the calculation, using an
appropriate return period storm for the outlet being protected. Typical return periods range from
2 to 10 years.
Sizing the outlet protection consists of:
• Selecting the Type of Outlet Protection. The outlet protection may consist of a plunge pool
(scour hole), an apron-type arrangement, or an energy dissipation basin (Haan et al., 1994).
The design of each differs. Plunge pools are typically used for outlet pipes that are eleyated
above the water surface. Aprons are used for other types of outlets. i
• Selecting the Geometry of the Outlet. Plunge pool geometry is based on the flow rate, jpipe
size and slope, tailwater depth, and size of the riprap lining (Haan et al., 1994). Apron
dimensions are determined by the ratio of the tailwater depth to pipe diameter (Haan et al.,
1994). Energy dissipation basins are used as an alternative to the plunge pool. Dimensjions
are a function of the brink depth-in the pipe at the design flow, pipe diameter, and size of
riprap (Haan etal, 1994). ;
!
• Size of Rock Lining. The size of the rock lining is a function of the discharge, pipe size,
tailwater depth, and geometry selected. Details on sizing the rock are given in Haan et al.
(1994).
The design method presented here applies to the sizing of rock riprap and gabions to protect a
downstream area. It does not apply to rock lining of channels or streams. The design of rock
outlet protection depends entirely on the location. Pipe outlets at the top of cuts or on slopes
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steeper than 10 percent cannot be protected by rock aprons or riprap sections due to
reconcentration of flows and high velocities encountered after the flow leaves the apron.
Installation Criteria
The following criteria should be considered.
• Bottom Grade: The outlet protection apron should be constructed with no slope along its
length. There should be no obstruction at the end of the apron. The elevation of the
downstream end of the apron should be equal to the elevation of the receiving channel or
adjacent ground.
• Alignment: The outer protection apron should be located so that there are no beds in the
horizontal alignment.
• Materials: The outlet protection may be done using rock riprap, or gabions. Riprap should
be composed of a well-graded mixture of stone sized so that 50 percent .of the pieces, by
weight, should be larger than the size determined by using the charts. The minimum d50 size
to be used should be 9 inches. A well-graded mixture is defined as a mixture composed
primarily of larger stone sizes but with a sufficient mixture of other sizes to fill the smaller
voids between the stones. The diameter of the largest stone in such a mixture should be
2.0 times the size selected in Table 5-22 (MDE, 1994).
• Thickness: The SHA riprap specification values are summarized in Table 5-22.
Class I
Class II
Class III
D,n (inches)
9.5
16
23
D,nn (inches)
15
24
34
Thickness (inches)
19
32
46
Stone Quality: Stone for riprap should consist of field stone or rough and hewn quarry stone.
The stone should be hard and angular and of a quality that will not disintegrate on exposure
to water or weathering. The specific gravity of the individual stones should be at least 2.5.
Recycled concrete equivalent may be used provided it has a density of at least 150 pounds
per cubic foot and does not have any exposed steel or reinforcing bars.
Filters: A filter is a layer of material placed between the riprap and the underlying soil
surface to prevent soil movement into and through the riprap to prevent piping, reduce uplift
pressure, and collect water. Riprap should have a filter placed under it in all cases. A filter
can be of two general forms: a gravel layer or a geotextile.
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• Gabions: Gabion baskets may be used as rock outlet protection, provided they are made of
hexagonal triple twist mesh with heavily galvanized steel wire. The maximum lined;
dimension of the mesh opening should not exceed 4.5 inches. The area of the mesh opening
should not exceed 10 square inches. Gabions should be fabricated in such a manner that the
sides, ends, and lid can be assembled at the construction site into a rectangular basket of the
specified sizes. Gabions should be of a single unit construction and should be installed
according to the manufacturer's specifications. The area on which the gabion is to be
installed should be graded as shown on the drawings. Foundation conditions should be the
same as for placing rock riprap. Geotextiles should be placed under all gabions. Gabions
must be keyed in to prevent undermining of the main gabion structure.
• The subgrade for the filter, riprap, or gabion should be prepared to the required lines and
grades. Any fill required in the subgrade shall be compacted to a density of approximately
that of the surrounding undisturbed material. '
• The rock or gravel should conform to the specified grading limits when installed in the riprap
or filter, respectively. !
• Geotextiles should be protected from punching, cutting, or tearing. Any damage other than
occasional small holes should be repaired by placing another piece of geotextile fabric over
the damaged part or by completely replacing the geotextile fabric. All overlaps, whether for
repairs or for joining two pieces of geotextile fabric, should be a minimum of 1 foot in
length. ;
• Stone for the riprap or gabion outlets may be placed by equipment. They should be
constructed to the full course thickness in one operation and in such a manner as to avoid
displacement of underlying materials. Care should be taken to ensure that the stone is not
placed so that rolling will cause segregation of stone by size, i.e., the stone for riprap or.
gabion outlets should be delivered and placed in a manner that will ensure that it is
reasonably homogeneous with the smaller stones filling the voids between the larger stones.
Riprap must be placed in a manner to prevent damage to the filter blanket or geotextile
fabric. Hand placement will be required to the extent necessary to prevent damage to the
permanent works. '
• Stone should be placed so that it blends in with the existing ground and the depth to the stone
surface is sufficient to transmit the flow without spilling over onto the unprotected surface.
Effectiveness
There is currently no information on the effectiveness of rock outlet structures.
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Limitations '
Common problems with rock outlet structures include the following:
• Foundation not excavated deep enough or wide enough—restricts the flow cross-section,
resulting in erosion around the apron and sour holes at the outlet.
• Riprap apron should be placed on a suitable foundation to prevent downstream erosion.
• Riprap installed smaller than specified—results in rock displacement; selectively grouting
over the rock materials may stabilize the situation.
• Riprap not extended enough to reach a stable section of the channel—results in downstream
erosion.
• No filter installed under the riprap—results in stone displacement and erosion of the
foundation.
Maintenance
Once a riprap outlet has been installed, the maintenance needs are very low. It should be
inspected after high flows to see if scour has occurred beneath the riprap, if flows have occurred
outside the boundaries of the riprap and caused scour, or if any stones have been dislodged.
Repairs should be made immediately.
Cost
R. S. Means indicates machine-placed riprap costs of approximately $40 per cubic yard. For a
riprap maximum size between 15 and 24 inches, a cubic yard of riprap will cover between 13.5
and 17 square feet for channel bed (assuming depth of riprap as given in Table 5-22). This
suggests that riprap lining will be between $21 and $27 per square foot of outlet (includes
materials, labor, and equipment, with overhead and profit). R. S. Means (2000) provides a cost
range for gabions ($2.80 to $9 per square foot of coverage) for stone fill depths of 6" to 36",
respectively. These costs include all costs of materials, labor, and installation.
5.1.5.4.3
SUMP PIT
Description
A sump pit is a temporary pit from which pumping is conducted to remove excess water while
minimizing sedimentation. The purpose of the sump pit is to filter water being pumped to
reduce sedimentation to receiving streams.
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Applicability
|
Sump pits are constructed when water collects and must be pumped away during excavating,
cofferdam dewatering, maintenance or removal of sediment traps and basins, or other uses as
applicable, such as" for concrete wash out.
Design and Installation Criteria '.
Hydrologic Design :
The only hydrologic calculation is determining the expected flow rate and volume to be handled.
This should follow standard hydrologic computational procedures based on design rainfall,
surface and soil conditions, and the size of the pump. ;
Installation Criteria and Specifications i
The number of sump pits and their locations should be determined by the designer and included
on the plans. Contractors may relocate sump pits to optimize use, but discharge location changes
should be coordinated with inspectors. ;
A perforated vertical sandpipe is wrapped with Vi inch hardware cloth and geotextiles and then
placed in the center of an excavated pit which is then backfilled with filter material consisting of
anything from clean gravel to stone. Water is then pumped from the center of the sandpipe to a
suitable discharge area such as into a sediment trap, sediment basin, or stabilized area. ,
A sump pit should conform to the following specifications:
• Pit dimensions are variable, with the minimum diameter being twice the diameter of the
sandpipe. :
• The sandpipe should be constructed by perforating a 12- to 36-inch diameter pipe, then
wrapping it with ^-inch hardware cloth and geotextiles. The perforations should be H- x 6-
inch slits or 1-inch diameter holes 6 inches on center. \
• The sandpipe should extend 12 to 18 inches above the lip of the pit or riser crest elevation
(basin dewatering), and filter material should extend 3 inches minimum above the anticipated
standing water level.
Effectiveness
There is currently no information on the effectiveness of the sump pit.
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Limitations
The sump pit must be properly maintained and pumped regularly to avoid clogging.
Maintenance
To maintain, sump pits must be removed and reconstructed when water can no longer be pumped
out of the sandpipe.
Cost
R. S. Means (2000) provides information appropriate for assessment of a wide range of
dewatering scenarios (i.e., different sump sizes, dewatering durations, and discharge conditions).
In general, installation of earthen sump pits are listed as costing approximately $1.50 per cubic
foot of sump volume. Piping to and away from the sump ranges from $30 to $60 per linear foot.
Pump rentals and operation range between $150 and $500 per day of pumping, depending on the
rate of dewatering. All costs include material, labor, and equipment, with overhead and profit.
5.1.5.4.4
Description
SEDIMENT TANK
A sediment tank is a compartmented tank container through which sediment-laden water is
pumped to trap and retain the sediment. The purpose of a sediment tank is to trap and retain
sediment prior to pumping the water to drainageways, adjoining properties, and rights-of-way
below the sediment tank site.
Applicability
A sediment tank should be used on sites where excavations are deep and space is limited, such as
urban construction, where direct discharge of sediment-laden water to streams and storm
drainage systems should be avoided.
Design and Installation Criteria
The location of sediment tanks should facilitate easy cleanout and disposal of the trapped
sediment to minimize interference with construction activities and pedestrian traffic. The tank
size should be determined according to the storage volume of the sediment tank, 1 cubic foot of
storage for each gallon per minute of pump discharge capacity.
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Effectiveness
There is currently no information on the effectiveness of sediment tanks.
Limitations :
The sediment tank does not provide any natural infiltration; thus, the trapped sediment and storm
water must be disposed of properly.
Maintenance
To properly maintain the sediment tank, it needs to be in a location that is easy to access.;
COSt ;
There is currently no information on the cost of sediment tanks. ;
5.1.5.4.5 STABILIZED CONSTRUCTION ENTRANCE
Description
The purpose of stabilizing entrances to a construction site is to minimize the amount of sediment
leaving the area as mud attached to motorized vehicles.. Installing a pad of gravel over filter
cloth where construction traffic leaves a site can help stabilize a construction entrance. As a
vehicle drives over the gravel pad, mud and. other sediments are removed from the vehicle's
wheels (sometimes by washing) and offsite transport of soil is reduced. The gravel pad also
reduces erosion and rutting on the soil beneath the stabilization structure. The fabric reduces the
amount of rutting caused by vehicle tires by spreading the vehicle's weight over a larger soil area
than just the tire width. The filter fabric also separates the gravel from the soil below, preventing
the gravel from being ground into the soil. *
Applicability
Typically, stabilized construction entrances are installed at locations where construction traffic
leaves or enters an existing paved road. However, the applicability of site entrance stabilization
should be extended'to any roadway or entrance where vehicles will access or leave the site.
From a public relations point of view, stabilizing construction site entrances can be a worthwhile
exercise. If the site entrance is the most publicly noticeable part of a construction site, stabilized
entrances can improve the appearance to passersby and improve public perception of the
construction project by reducing the amount of mud tracked onto adjacent streets.
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Design and Installation Considerations
Hydrologic Design
Not applicable.
Installation Criteria and Specifications
All entrances to a site should be stabilized before construction begins and further disturbance of
the site area occurs. The stabilized site entrances should be long enough and wide enough so
that the largest construction vehicle that will enter the site will fit in the entrance with room to
spare. If many vehicles are expected to use an entrance hi any one day, the site entrance should
be wide enough for the passage of two vehicles at the same time with room on either side of each
vehicle. For optimum effectiveness, a rock construction entrance should be at least 50 feet long
and at least 10 to 12 feet wide (USEPA, 1992). If a site entrance leads to a paved road, the end
of entrance should be "flared" (made wider as hi the shape of a funnel) so that long vehicles do
not go off the stabilized area when turning onto or off of the paved roadway.
If a construction site entrance crosses a stream, swale, roadside channel, or other depression, a
bridge or culvert should be provided to prevent erosion from unprotected banks.
Stone and gravel used to stabilize the construction site entrance should be large enough so that
they are not carried off-site with vehicle traffic. In addition, sharp-edged stone should be
avoided to reduce the possibility of puncturing vehicle tires. Stone or gravel should be installed
at a depth of at least 6 inches for the entire length and width of the stabilized construction
entrance.
Effectiveness
Stabilizing construction entrances to prevent sediment transport off-site is effective only if all
entrances to the site are stabilized and maintained. Also, stabilization of construction site
entrances may not be very effective unless a wash rack is installed and routinely used (Corish,
1995) but this can be problematic for sites with multiple entrances with high vehicle traffic.
Limitations
Although stabilizing a construction entrance is a good way to help reduce the amount of
sediment leaving a site, some soil may still be deposited from vehicle tires onto paved surfaces.
To further reduce the chance that these sediments will pollute storm water runoff, sweeping of
the paved area adjacent to the stabilized site entrance is recommended.
For sites using wash stations, a reliable water source to wash vehicles before leaving the site
might not be initially available, hi this case, water may have to be trucked to the site at
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additional cost. Discharge from the wash station should be directed into an appropriate sediment
control structure.
i
Maintenance
Stabilization of site entrances should be maintained until the remainder of the construction site
has been fully stabilized. Stone and gravel might need to be periodically added to each
stabilized construction site entrance to keep the entrance effective. Soil that is tracked offsite
should be swept up immediately for proper disposal. •
For sites with wash racks at each site entrance, sediment traps will have to be constructed and
maintained for the life of the project. Maintenance will entail the periodic removal of sediment
from the traps to ensure their continued effectiveness.
Cost
Without a wash rack, construction site entrance stabilization costs range from $1,000 to $4,000.
On average, the initial construction cost is around $2,000 per entrance. When maintenance costs
are included, the average total annual cost for a 2-year period, is approximately $ 1,500. ;
If a wash rack is included in the construction site entrance stabilization, the initial construction
costs range from $1,000 to $5,000, with an average initial cost of $3,000 per entrance. Tptal
annual cost, including maintenance for an estimated 2-year life span, is approximately $2,200
per year (USEPA, 1993). !
5.1.5.4.6
Description
LAND GRADING
Land grading involves reshaping the ground surface to planned grades as determined by an
engineering survey, evaluation, and layout. Land grading provides more suitable topography for
buildings, facilities, and other land uses and helps to control surface runoff, soil erosion, and
sedimentation both during and after construction.
Applicability ;
Land grading is applicable to sites with steep topography or easily erodible soils because it
stabilizes slopes and decreases runoff velocity. Grading activities should maintain existing
drainage patterns as much as possible. • ;
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Design and Installation Criteria
Before grading activities begin, decisions should be made regarding the steepness of cut-and-fill
slopes and how the slopes will be protected from runoff, stabilized, and maintained. A grading
plan that establishes which areas of the site will be graded, how drainage patterns will.be
directed, and how runoff velocities will affect receiving waters should be prepared. The grading
plan also includes information regarding when earthwork will start and stop, establishes the
degree and length of finished slopes, and dictates where and how excess material will be
disposed of (or where borrow materials will be obtained if needed). Berms, diversions, and
other storm water practices that require excavation and filling should also be incorporated into
the grading plan.
A low-impact development BMP that can be incorporated into a grading plan is site
fingerprinting, which involves clearing arid grading only those areas necessary for building
activities and equipment traffic. Adhering to strict limits of clearing and grading helps to
maintain undisturbed temporary or permanent buffer zones in the grading operation and provides
a low-cost sediment control measure that will help reduce runoff and off-site sedimentation. The
lowest elevation of the site should remain undisturbed to provide a protected storm water outlet
before storm drains or other construction outlets are installed.
Effectiveness
Land grading is an effective means of reducing steep slopes and stabilizing highly credible soils
when implemented with storm water management and erosion and sediment control practices in
mind. Land grading is not effective when drainage patterns are altered or when vegetated areas
on the perimeter of the site are destroyed.
Limitations
Construction sites are routinely graded to prepare a site for buildings and other structures.
Improper grading practices that disrupt natural storm water patterns might lead to poor drainage,
high runoff velocities, and increased peak flows during storm events. Clearing and grading of
the entire site without vegetated buffers promotes off-site transport of sediments and other
pollutants. Grading plans should be designed with erosion and sediment control and storm water
management goals in mind; grading crews should be carefully supervised to ensure that the plan
is implemented as intended.
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Maintenance
All graded areas and supporting erosion and sediment control practices should be periodically
checked, especially after heavy rainfalls. All sediment should be promptly removed from
diversions or other storm water conveyances. If washouts or breaks occur, they should be
repaired immediately. Prompt maintenance of small-scale eroded areas is essential to prevent
these areas from becoming significant gullies.
Cost
Land grading is practiced at virtually all construction sites—additional site planning to
incorporate storm water and erosion and sediment controls in grading plans can require several
hours of planning by a certified engineer or landscape architect. Extra time might be required to
excavate diversions and construct berms, and fill materials might be needed to build up low-
lying areas or fill depressions.
Where grading is performed to manage on-site storm water, R. S. Means (2000) suggests 'the
cost of fine grading, soil treatment, and grassing to be approximately $2 per square yard of earth
surface area. Shallow excavation/trenching (1 to 4 feet deep) with a backhoe in areas not
requiring dewatering can be performed for $4 to $5 per cubic yard of removed material. Larger
scale grading requires a site-specific assessment of an alternative grading apparatus and a
detailed fill/excavation material balance to retain as much soil on site as possible.
5.1.5.4.7
Description
TEMPORARY ACCESS WATERWAY CROSSING
A temporary stream crossing is a structure erected to provide a safe and stable way for !
construction vehicle traffic to cross a running watercourse. The primary purpose of such a
structure is to provide streambank stabilization, to reduce the risk of damaging the streambed or
channel, and to reduce the risk of sediment loading from construction traffic. A temporary
stream crossing may be a bridge, culvert, or ford. :
Applicability
Temporary stream crossings are applicable wherever heavy construction equipment must be
moved from one side of a stream channel to the other or where lighter construction vehicles will
cross the stream a number of tunes during the construction period. In either case, an appropriate
method for ensuring the stability of the streambanks and preventing large-scale erosion is'
necessary.
A bridge or culvert is the best choice for most temporary stream crossings. If properly de'signed,
each can support heavy loads, and materials used to construct most bridges and culverts can be
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salvaged after they are removed. Fords are appropriate in steep areas subject to flash flooding,
where normal flow is shallow or intermittent across a wide channel. Fords should be used only
where stream crossings are expected to be infrequent.
Design and Installation Criteria
Because of the potential for stream degradation, flooding, and safety hazards, stream crossings
should be avoided on a construction site whenever possible. Consideration should be given to
alternative site access routes before arrangements are made to erect a temporary stream crossing.
If it is determined that a stream crossing is necessary, an area where the potential for erosion is
low should be selected. The stream crossing structure should be selected during a dry period if
possible to reduce sediment transport into the stream.
If needed, over-stream bridges are generally the preferred temporary stream crossing structure.
The expected load and frequency of the stream crossing, however, will govern the selection of a
bridge as the correct choice for a temporary stream crossing. These types of temporary bridges
usually cause minimal disturbance to a stream's banks and cause the least obstruction to stream
flow and fish migration. They should be constructed only under the supervision and approval of
a qualified engineer.
As general guidelines for constructing temporary bridges, clearing and excavation of the stream
shores and bed should be kept to a minimum. Sufficient clearance should be provided for
floating objects to pass under the bridge. Abutments should be parallel to the stream and on
stable banks. If the stream is less than 8 feet wide at the point where a crossing is needed, no
additional in-stream supports should be used. If the crossing is to extend across a channel wider
than 8 feet (as measured from top of bank to top of bank), the bridge should be designed with
one in-water support for each 8 feet of stream width.
A temporary bridge should be anchored by steel cable or chain on one side only to a stable
structure on shore. Examples of anchoring structures include trees with a large diameter, large
boulders, and steel anchors. By anchoring the bridge on one side only, there is a decreased risk
of causing a downstream blockage or flow diversion if a bridge is washed out.
When constructing a culvert, filter cloth should be used to cover the streambed and streambanks
to reduce settlement and improve the stability of the culvert structure. The filter cloth should
extend a minimum of 6 inches and a maximum of 1 foot beyond the end of the culvert and
bedding material. The culvert piping should not exceed 40 feet in length and should be of
sufficient diameter to allow for complete passage of flow during peak flow periods. The culvert
pipes should be covered with a minimum of 1 foot of aggregate. If multiple culverts are used, at
least 1 foot of aggregate should separate the pipes.
Fords should be constructed of stabilizing material such as large rocks.
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Effectiveness ;
Both temporary bridges and culverts provide an adequate path for construction traffic crossing a
stream or watercourse. ;
Limitations
Bridges can be considered the greatest safety hazard of all temporary stream crossing structures
if not properly designed and constructed. Bridges might also prove to be more costly in terms of
repair costs and lost construction tune if they wash out or collapse (Smolen et al., 1988).
The construction and removal of culverts are usually very disturbing to the surrounding area, and
erosion and downstream movement of soils are often great. Culverts can also create obstructions
to flow in a stream and inhibit fish migration. -Depending on their size, culverts can be blocked
by large debris in a stream and are therefore vulnerable to frequent blockage and washout.
If given a choice between building a bridge or a culvert as a temporary stream crossing, a bridge
is preferred because of the relative minimal disturbance to'streambanks and the opportunity for
unimpeded flow through the channel. The approaches to fords often have high erosion potential.
In addition, excavation of the streambed and approach to lay riprap or other stabilization imaterial
causes major stream disturbance. Mud and other debris are transported directly into the stream
unless the crossing is used only during periods of low flow. ;
E
Maintenance
Temporary stream crossings should be inspected at least once a week and after all significant
rainfall events. If any structural damage is reported to a bridge or culvert, construction traffic
should stop using the structure until appropriate repairs are made. Evidence of streambahk
erosion should be repaired immediately.
Fords should be inspected closely after major storm events to ensure that stabilization materials
remain in place. If the material has moved downstream during periods of peak flow, the|lost
material should be replaced immediately. ;
Cost
In general, temporary bridges are more expensive to design and construct than culverts. Bridges
are also associated with higher maintenance and repair costs should they fail. Additional costs
may accrue to the site team in terms of lost construction time if a temporary structure is washed
out or otherwise fails. ;
Temporary bridging costs range as a function of the width of the bridge span and the duration of
application. If the bridging is permanent, a mean cost of $50 per square foot for an 8-foot wide
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steel arch bridge (no foundation costs included) can be used for conceptual cost estimation
(R. S. Means, 2000). If rental bridging is employed, then rates are probably on the order of 20 to
50 percent of the bridge (permanent) cost, but will range based on the rental duration and
mobilization distance.
5.1.5.4.8
DUST CONTROL
General Description
Dust control measures are practices that help reduce ground surface and air movement of dust
from disturbed soil surfaces. Construction sites are good candidates for dust control measures
because land disturbance from clearing and excavation generates a large amount of soil
disturbance and open space for wind to pick up dust particles. To illustrate this point, research at
construction sites has established an average dust emission rate of 1.2 tons/acre/month for active
construction (WA Dept. of Ecology, 1992). These airborne particles pose a dual threat to the
environment and human health. First, dust can be carried off-site, thereby increasing soil loss
from the construction area and increasing the likelihood of sedimentation and water pollution.
Second, blowing dust particles can contribute to respiratory health problems and create an
inhospitable working environment.
Applicability
Dust control measures are applicable to any construction site where dust is created and there is
the potential for air and water pollution from dust traveling across the landscape or through the
air. Dust control measures are particularly important in arid or semiarid regions where soil can
become extremely dry and vulnerable to transport by high winds.
Also, dust control measures should be implemented on all construction sites where there will be
major soil disturbances or heavy construction activity, such as clearing, excavation, demolition,
or excessive vehicle traffic. Earthmoving activities are the major source of dust from
construction sites, but traffic and general disturbances can also be major contributors (WA Dept
of Ecology, 1992).
The specific dust control measures implemented at a site will depend on the topography, land
cover, soil characteristics and amount of rainfall at the site.
Design and Installation Criteria
When designing a dust control plan for a site, the amount of soil exposed will dictate the
quantity of dust generation and transport. Therefore, construction sequencing and disturbing
small areas at one time can greatly reduce problematic dust from a site. If land must be
disturbed, additional temporary stabilization measures should be considered prior to disturbance.
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A number of methods can be used to control dust from a site. The following is a brief list of
control measures and their design criteria. Not all control measures will be applicable to a given
site. The owner, operator, and contractors responsible for dust control at a site should determine
which practices accommodate theu: needs based on specific site and weather conditions. •
Sprinkling/Irrigation: Sprinkling the ground surface with water until it is moist is an effective
dust control method for haul roads and other traffic routes (Smolen et al., 1988). This
practice can be applied to almost any site. >
Vegetative Cover. In areas not expected to handle vehicle traffic, vegetative stabilization! of
disturbed soil is often desirable. Vegetative cover provides protection to surface soils, and
slows wind velocity at the ground surface, thus reducing the potential for dust to become
airborne.
Mulch: Mulching can be a quick and effective means of dust control for a recently disturbed
area (Smolen et al., 1988).
I
Wind Breaks: Wind breaks are barriers (either natural or constructed) that reduce wind velocity
through a site and therefore reduce the possibility of picking up suspended particles. Wind
breaks can be trees or shrubs left in place during site clearing or constructed barriers such as
a wind fence, snow fence, tarp curtain, hay bale, crate wall, or sediment wall (USEPA,
1992). ;
Tillage: Deep tillage in large open areas brings soil clods to the surface where they rest on top of
dust, preventing it from becoming airborne.
Stone: Stone can be an effective dust deterrent for construction roads and entrances.
Spray-on Chemical Soil Treatments (palliatives): Examples of chemical adhesives include
anionic asphalt emulsion, latex emulsion, resin-water emulsions, and calcium chloride.
Chemical palliatives should be used only on mineral soils. When considering chemical
application to suppress dust, consideration should be taken as to whether the chemicaj is
biodegradable or water-soluble and what effect its application could have on the surrounding
environment, including waterbodies and wildlife. ;
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Table 5-23 shows application rates for some common spray-on adhesives as recommended by
Smolen et al. (1988).
Table 5-23. Application Rates for Spray-On Adhesives
Spray on Adhesive
Anionic Asphalt Emulsion
Latex Emulsion
Resin in Water
Water Dilution
7:1
12.5:1
4:1
Type of Nozzle
Coarse spray
Fine spray
Fine spray
Application (gal/acre)
1,200
235
300
Source: Smolen et al., 1988.
Effectiveness
Sprinkling/Irrigation: Not available.
Vegetative Cover: Not available.
Mulch: Can reduce wind erosion by 80 percent.
Wind Breaks/Barriers: For each foot of vertical height, an 8- to 10-foot deposition zone develops
on the lee.ward side of the barrier. The barrier density and spacing will change its
effectiveness at capturing windborne sediment.
Tillage:.Roughening the soil can reduce soil losses by approximately 80 percent.
Stone: The sizes of the stone can affect the amount of erosion that will take place. In areas of
high wind, small stones are not as effective as a 20 cm stone.
Spray-on Chemical Soil Treatments (palliatives): Effectiveness of polymer stabilization
methods ranges from 70 percent to 90 percent.
Limitations
In areas where evaporation rates are high, water application to exposed soils may require near
constant attention. If water is applied in excess, runoff may result from the site and possibly
create conditions where vehicles could track mud onto public roads.
Chemical applications should be used sparingly and only on mineral soils (not high organic
content soils) because their misuse can create additional surface water pollution from runoff or
contaminate groundwater. Chemical applications might also present a health risk if excessive
amounts are used.
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Maintenance i
Because dust controls are dependent on specific site conditions, including the weather,
inspection and maintenance are unique for each site. Generally, however, dust control measures
involving application of either water or chemicals require more monitoring than structural or
vegetative controls to remain effective. If structural controls are used, they should be inspected
for deterioration on a regular basis to ensure, they are still achieving their intended purpose.
Cost ;
Chemical dust control measures can vary widely in cost depending on specific needs of the site
and level of dust control desired. One manufacturer of a chloride product estimated a cost of
$1,089 per acre for application to road surfaces, but cautioned that cost estimates withoutja
specific site evaluation are rather inaccurate.
5.1.5.4.9
Description
STORM DRAIN INLET PROTECTION
Storm drain inlet protection measures are controls that help prevent soil and debris from dn-site
erosion from entering storm drain drop inlets." Typically, these measures are temporary cbntrols
that are implemented prior to large-scale disturbance of the surrounding site. These controls are
advantageous because their implementation allows storm drains to be used during even thfe early
stages of construction activities. The early use of storm drains during project development
significantly reduces the occurrence of future erosion problems (Smolen et al, 1988).
Three temporary control measures to protect storm drain drop inlets are ;
• Excavation around the perimeter of the drop inlet !
• Fabric barriers around inlet entrances
• Block and gravel protection
Excavation around a storm drain inlet creates a settling pool to remove sediments. Weep holes
protected by gravel are used to drain the shallow pool of water that accumulates around the inlet.
A fabric barrier made of porous material erected around an inlet can create an effective shield to
sediment while allowing water to flow into the storm dram. This type of barrier can slow runoff
velocity while catching soil and other debris at the drain inlet. Block and gravel inlet protection
uses standard concrete blocks and gravel to form a barrier to sediments while permitting Water
runoff through select blocks that are laid sideways.
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In addition to the materials listed above, limited temporary storm water drop inlet protection can
also be achieved with the use of straw bales or sandbags to create barriers to sediment.
For permanent storm drain drop inlet protection after the surrounding area has been stabilized,
sod can be installed as a barrier to slow storm water entry to storm drain inlets and capture
sediments from erosion. This final inlet protection measure can be used as an aesthetically
pleasing way to slow storm water velocity near drop inlet entrances and remove sediments and
other pollutants from runoff.
A new technology that uses an insert trap into the inlet itself has been developed (Adams et al.,
2000). This technique showed good results on initial testSj trapping more than 50 percent of the
incoming sediment in flows typical of those into urban storm drains. This technique is being
further developed with a pending patent application.
Applicability
All temporary controls should have a drainage area no greater than 1 acre per inlet. It is also
important for temporary controls to be constructed prior to disturbance of the surrounding
landscape. Excavated drop inlet protection and block and gravel inlet protection are applicable
to areas of high flow where overflow is anticipated into the storm drain. Fabric barriers are
recommended for smaller, relatively flat drainage areas (slopes less than 5 percent leading to the
storm drain).
Temporary drop inlet control measures are often used in combination with each other and with
other storm water control techniques.
Design and Installation Considerations
Hydrologic Design
Hydrologic computations are not necessary with present technologies. A specified limitation of
1 acre per inlet limits flow rates, dependent on local rainfall and runoff considerations.
Installation Criteria and Specifications
The following criteria should be followed until future research establishes better techniques:
• With the exception of sod drop inlet protection, these controls should be installed before any
soil disturbance in the drainage area. , . -
• Excavation around drop inlets should be dug a minimum of 1 foot deep (2 feet maximum)
with a minimum excavated volume of 35 cubic yards per acre disturbed. Side slopes leading
to the inlet should be no steeper than 2:1. The shape of the excavated area should be
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designed such that the dimensions fit the area from which storm water is anticipated to drain.
For example, the longest side of an excavated area should be along the side of the inlet
expected to dram the largest area. '
• Fabric inlet protection is essentially a filter fence placed around the inlet. The fabric asures
should not be used as stand-alone sediment control measures. To increase inlet protection
effectiveness, these practices should be used in combination with other measures, such as
small impoundments or sediment traps (USEPA, 1992). Temporary storm drain inlet:
protection is not intended for use in drainage areas larger than 1 acre. Generally, storm water
inlet protection measures are practical for relatively low sediment and low volume flows.
Frequent maintenance of storm drain controls is necessary to prevent clogging. If sediment and
other debris clog the water intake, drop intake control measures can actually cause erosion in
unprotected areas. . '
Maintenance
All temporary control measures must be checked after each storm event. To maintain the
sediment capacity of the shallow settling pools created from these techniques, accumulated
sediment should be removed from the area around the drop inlet (excavated area, around fabric
barrier, or around block structure) when the sediment storage is reduced by approximately 50
percent. Additional debris should be removed from the shallow pools on a periodic basis.
Weep holes in excavated areas around inlets can become clogged and prevent water from
draining from the shallow pools that form. Should this happen, unclogging the water intake may
be difficult and costly. i •
Cost •
The cost of implementing storm drain drop inlet protection measures will vary depending on the
control measure chosen. Generally, initial installation costs range from $50 to $150 per inlet,
with an average cost of $100 (USEPA, 1993). Maintenance costs can be high (annually, up to
100 percent of the initial construction cost) because of frequent inspection and repair needs. The
Southeastern Wisconsin Regional Planning Commission has.estimated that the cost of
installation of inlet protection devices ranges from $106 to $154 per inlet (SEWRPC,' 1991).
5.1.5.4.10 POLYACRYLAMIDE (PAM)
General Description
The term polyacrylamide (PAM) is a generic term that refers to a broad class of compounds.
There are hundreds of specific PAM formulations, and all have unique properties that depend on
polymer chain length and number and kinds of functional group substitutions along the chain.
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PAMs are classified according to their molecular weight and ionic charge and are available in
solid, granular, liquid, or emulsion forms.
PAM's effectiveness to prevent or reduce erosion is due to its affinity for soil particles, largely
via coulombic and Van der Waals attraction. These surface attractions enhance particle
cohesion, stabilizing soil structure against shear-induced detachment and transport in runoff. In
a soil application, PAM aggregates soil particles, increasing pore space and infiltration capacity,
resulting in reduced runoff. These larger particle aggregates are less susceptible to raindrop and
scour erosion, thus reducing the potential to mobilize sediments.
Applicability
Because of ease in application, PAM is well suited as a short-term erosion prevention BMP,
especially for areas with limited access or steep slopes that hinder personnel from applying other
cover materials. PAM can be used to augment other cover practice BMPs, though it can be
effective when applied alone. Thus, the ease of application, low maintenance, and relatively low
cost associated with PAM make it a practical solution to soil stabilization during construction.
Application Criteria
PAM can be applied to soil through either a dry granular powder or a liquid spray form. Optimal
application rates to prevent erosion on construction sites are generally less than 1 kg/ha (about 1
Ib/ac) (Tobiason et al., 2000). However, the concentration required can vary for specific soil
properties and construction phases. WDOT (2002) suggests a dosage of 60 mg/L for roadway
erosion and sediment control. This is higher than the rate recommended by the University of
Nebraska for an agricultural application (10 parts per million). To put this into context, one half
pound of PAM inlOOO gallons of water results in a PAM concentration of 60 mg/L, which treats
1 acre of exposed soil to WDOT recommendations.
e
Effectiveness
A study performed in Dane County, Wisconsin, analyzed 15 small plots (1 meter x 1 meter) for
runoff and sediment yield on a construction site. The study concluded that when a solution of
PAM-mix with mulch/seeding was applied to dry soil and compared with the control (no PAM-
mix application to dry soil), an average reduction of 93 percent in sediment yield was found. An
average reduction of 77 percent in sediment yield was the worst performing PAM treatment and
occurred when PAM-mix in solution was applied to moist soil. The application of dry PAM-mix
to dry soil reduced sediment by 83 percent and decreased runoff by 16 percent when compared
to the control. The results show that regardless of the application method, PAM-mix was
effective in reducing sediment yield in the test plots (Roa-Espinosa et al., 2000).
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A second study performed in Washington analyzed the runoff from three different construction
sites: an erosion control test facility, a highway construction site, and an airport runway. Table
5-24 summarizes the 225 samples analyzed in Tobiason et al. (2000). ;
Table 5-24. Turbidity Reduction Values from PAM
Maximum
Median
Minimum
Volume, m3
350
285
133
Turbidity Reduction (%)
99.97
97.6
46
Limitations
Currently PAMs are most commonly produced as dry granules. They completely dissolve and
remain dissolved if mixed properly. If added too quickly or if not stirred vigorously the granules
rapidly form nondissolvable gels on contact with water or collect in low turbulence areas as
syrupy concentrations that dissolve slowly in an uncontrolled pattern over a period of hours or
days (USDA, 1994). - |
In addition, when spilled on hard surfaces, PAM solutions are extremely slippery and hazardous
to foot and vehicle traffic. PAM dust is highly hygroscopic and, if inhaled, could impair
breathing. Certain neutral and cationic PAMs at very high exposure levels produce irritation in
humans and are somewhat toxic to certain aquatic organisms; therefore, PAM should be used in
strict compliance with state and federal label requirements.
Finally, although PAM is rather inexpensive, there are considerable infrastructure needs and
operating costs; thus, sophisticated onsite polymer treatment systems may not be appropriate for
certain projects. ;
1 !
Cost
The cost of PAM ranges from $1.25 per pound to $5.00 per pound (Entry etal., 1999). the cost
of PAM application depends on the system employed. PAM can be used in a centralized
treatment system (e.g., at a sedimentation basin) to treat larger areas, or dispersed in granular or
liquid form, hi Tobiason et al. (2000), the startup costs for the batch treatment system amounted
to $90,000. Monthly expenses averaged $18,000 for operations and maintenance and $13,000
for materials and equipment. The total costs for this phase totaled about $245,000, less than 1
percent of total construction costs. If dispersed through irrigation systems (for agriculture), the
seasonal cost of PAM treatment is $9 to $15 per acre (Kay-Shoemake, et. al., 2000), where a
season probably requires between 5 and 10 applications.
For construction sites, it is more likely that PAM would be applied as an additive to the.
hydroseed mix and applied when final grade is established and cover vegetation is installed.
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Based on a recent scan of the Internet, there are numerous suppliers who provide PAM as a low
cost additive for hydroseeding, suggesting PAM application costs can be incorporated into that
of hydroseeding ($540 to $700 per acre depending on which seed is applied). An additional cost
would be incurred to sample site soils to customize the dosage and delivery mechanisms for
individual sites. In addition, re-application of PAM in granular or liquid form to areas with rill
development (poor vegetation cover) would require additional funds. Where re-application of
granular PAM is used, R. S. Means (2000) suggests a cost of approximately $5 per 1000 square
feet for spreading soil admixtures by hand.
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5.1.6 SUMMARY
The BMP information presented in sub-section 5.1 is summarized in Tables 5-25 through 5-28.
Table 5-25. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.1)
BMP Type
Receiving Water Quality
Physical Impact Mitigation
Other Impacts
Downstream Impacts
lanning/
Staging/
Scheduling
lould be low cost.
One data set shows 42% reduction
in sediment yield due to
planning/staging/scheduling.
Requires additional advance
planning and management.
mpact could be evaluated with
models as well as
experimentally since several
computer models are
available.
Jould be low cost.
Database is poor.
o validated urban runoff models
available for theoretical
analysis of downstream
impacts.
otential exists to modify existing
models to make the analysis
of downstream impacts on
geomorphology.
^o good cause-effect
relationships ',
available.
Other impacts not
evaluated.
Vegetative
Stabilization
'ould be low cost
Can be very effective in some
cases with advance planning.
Can be important on streambanks.
Limited applicability hi the active
construction area.
implements other practices. ••'
Practice is seasonably dependent
hi most of nation.
inpact could be evaluated with
models as well as
experimentally since several
computer models are
available.
Could be low cost.
Database is poor.
<[o validated urban runoff models
available for theoretical
analysis of downstream
impacts.
Potential exists to modify existing
models to make the analysis
of downstream impacts on
geomorphology.
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Development Document for Construction and Development Proposed Effluent Guidelines
Table 5-25. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.1)
BMP Type
Seeding
>
Sodding .
Mulching
--
Physical Impact Mitigation
Receiving Water Quality
Low-cost method for establishing
vegetation.
Occurs near the end of active
construction.
Requires significant time for
establishment.
Need a prepared seedbed.
Good database on impact on soil
, erosion.
Should be supported by other
BMPs.
High-cost method of establishing
vegetation.
Immediate stabilization.
Requires significant management
attention during
establishment.
Good database on impact on soil
erosion.
Very effective way of controlling
erosion.
Works well for grass waterways
and other significant problems
area.
Should be supported by other
BMPs.
Relatively low-cost method of
providing cover.
Can be highly effective in
reducing soil loss when
properly anchored.
Good database on impact on soil
erosion.
Variety of materials can be used.
nstallation is rapid.
fot a stand-alone practice.
Due to interference with
construction operations, the
times that it can be used
during active construction are
limited.
Downstream Impacts
Should not be evaluated as stand-
alone practice, but as part of a
system.
Database is poor.
No validated urban runoff models
available for theoretical
analysis of downstream
impacts.
Some potential exists to modify
existing models to make the
analysis of downstream
impacts on geomorphology.
Should not be evaluated as stand-
alone practice, but as part of a
system.
Database is poor.
No validated urban runoff models
available for theoretical
analysis of downstream
impacts.
Some potential exists to modify
existing models to make the
analysis of downstream
impacts on geomorphology.
Database is poor.
"io validated urban runoff models
available for theoretical
analysis of downstream
impacts.
ome potential exists to. modify
existing models to make the
analysis of downstream
impacts on geomorphology.
Other Impacts
No good cause-effect
relationships available.
Other impacts not
evaluated.
sk> good cause-effect
relationships
available.
Other impacts not
evaluated.
'•Jo good cause-effect
relationships
available.
Other impacts not
evaluated.
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Table 5-25. Summary of Information on Erosion Control and Prevention BMPs
(Snb-section 5.1.5.1)
BMP Type
Erosion
Control
Matting
/Geotextiles
Vegetative
Buffer
Strips
Physical Impact Mitigation
Receiving Water Quality
Cost is highly variable.
Effectiveness in controlling
sediment is variable
depending on type material.
Can provide immediate protection
to exposed soils.
Not a stand-alone practice.
Due to interference with
construction operations, the
times that it can be used
during active construction are
limited.
Disposal is a significant problem
and may require landfilling.
Can be used for channel linings as
stand alone or under riprap.
Fair database on effectiveness in
preventing erosion.
Can be highly effective in trapping
sediment.
Effectiveness is well established
and considerable data
collected.
Well-validated models are
available to predict the
impacts of constructed filter
strips on sediment trapping.
Models are included in watershed
stormwater and sediment
models.
Modifications needed for natural
riparian zones.
Require routine maintenance.
May be most appropriate where
sediment loads are relatively
low.
Downstream Impacts
Database is poor.
No validated urban runoff models
available for theoretical
analysis of downstream
impacts.
Some potential exists to modify
existing models to make the
analysis of downstream
impacts on geomorphology
i
Database is poor.
No validated urban runoff models
available for theoretical
analysis of downstream
impacts.
Some potential exists to modify
existing models to make the
analysis of downstream
impacts on geomorphology
Other Impacts (
No good cause-effect
relationships
available.
Other impacts not
evaluated.
•
1
No good cause-effect
relationships
available. ;
Other impacts not
evaluated. ;
.
;
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Table 5-25. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.1)
BMP Type
Top soiling
Physical Impact Mitigation
Receiving Water Quality
Important in vegetative
establishment.
No protection until cover is
established.
Not a stand-alone practice, but
must be supported by other
BMPs.
No known information to describe
effectiveness and cost not
currently available.
Downstream Impacts
Database is poor.
No validated urban runoff models
available for theoretical
analysis of downstream
impacts.
Some potential exists to modify
existing models to make the
analysis of downstream
impacts on geomorphology
Other Impacts
No good cause-effect
relationships
available.
Other impacts hot
evaluated.
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Table 5-26. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.2)
BMP Type
Physical Impact Mitigation
Receiving Water Quality
Downstream Impacts
Other Impacts
Earth Dike
Used to protect down slope areas.
Should be stabilized prior to use.
Requires maintenance after every
major storm.
Can be significant source of
sediment if not properly
constructed.
Little data available on its
effectiveness as a BMP.
Can be relatively inexpensive,
depending on design.
Not a stand-alone procedure.
No known information available.
No known information
available.
Temporary
Swale
Effectively a grass-lined drainage
ditch with shallow side slopes.
Can be applied in many areas, but
use limited in arid areas.
Contaminants that will harm
vegetation, such as oils and
greases, cannot be discharged to
the system.
Continuous water flow cannot be
tolerated by the grass lining.
Effectiveness depends on
infiltration. Can be a problem of
groundwater pollution with high
water tables.
Some studies show that they export
bacteria.
Some studies show high removal
efficiency for TSS, fair for
nutrients, are variable for metals.
No general relationships available
to predict the impact under widely
varied climates and conditions,
hence the effectiveness cannot be
predicted for a given situation
beyond the limited database.
No known information available.
No known information
available. ;
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Table 5-26. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.2)
BMP Type
Receiving Water Quality
'hysical Impact Mitigation
Downstream Impacts
mporary
Storm Drain
Diversion
(Pipe)
Reroutes existing drainage systems.
Primary benefit is to separate
drainage water originating from
undisturbed and construction and
reduce the volume of water to be
treated.
Can be combined with other
structures, such as sediment traps,
and used for sediment trapping.
. Require little maintenance.
Requires outlet stabilization. Can
be a significant source of sediment
without outlet stabilization.
Can be costly, depending on size,
installation, and removal.
No known information available.
No known information
available.
ipe Slop<
Drain
Routes runoff from concentrated
flow to stabilized areas.
Can be very effective in
eliminating gully erosion problems,
if properly installed and
maintained.
Can be constructed from low-cost
corrugated PVC, but must be
anchored or buried along slope.
Needs to be checked frequently for
sedimentation and other
maintenance problems.
No known information available.
No known information
available.
Dams
Reduces velocity of flow and
prevents erosion.
Stabilizes channel slope on steep
sections by stairstepping.
Can trap small percentages of
sediment behind dam.
Used for short periods of time
where channel lining is impractical.
Limited lab studies show high
effectiveness, but very limited field
studies show low trapping
efficiency.
Must be installed such that
overtopping occurs over the rock
fill and not around the perimeter.
Should not be used in continuously
flowing streams.
Relatively expensive, if properly
installed.
Procedures for predicting impact of
properly installed stone check dams
are available and incorporated into
watershed computer models.
No known information available.
No known information
available.
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Table 5-26. Summary of Information on Erosion Control and Prevention BMPs
Lined
Waterways
• Designed for stability and capacity.
• Local rainfall-runoff conditions
and linings will influence channel
dimensions.
• Require some maintenance during
vegetative establishment.
• Not designed as sediment removal
device, but to prevent channel
Other Impacts
available.
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Table 5-27. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.3)
BMP Typ
Receiving Water Quality
Physical Impact Mitigation
Downstream Impacts
Other Impacts
Silt Fence,
Most widely recognized sediment
control BMP.
Frequently poorly installed with little
design consideration.
Maintenance is frequently poor,
resulting in frequent failure.
Frequent maintenance is required
for proper operation.
^aboratory studies show fair to good
sediment trapping by filter fence,
but limited field studies do not
show the same results.
Evaluations of installations show that
failure is frequent,' coming from
undercutting of the fabric and
subsequent gully erosion.
ihould not be installed where rocks anc
other hard surfaces prevent
anchoring.
'•Jo validated procedures are available
to predict the effectiveness of the
filter fence in trapping sediment,
primarily because of the lack of
validated relationships for
predicting flow through the filter
fence.
'rocedures for evaluating the
anchoring requirements and
support post requirements have not
adequately accounted for variable
soil strength conditions, resulting
in frequent failure of the fence
under loading.
Database is poor.
No validated urban runoff models
available for theoretical analysis
of downstream impacts.
Some potential exists to modify
existing models to make the
analysis of downstream impacts on
geomorphology
No good cause-effect
relationships
available.
Other impacts not
evaluated.
uper Silt
ence
Modification of standard silt-fence to
improve it structurally.
"Jo validation information is available.
{.ecommended to be used where
destruction of the silt fence will
destroy critical areas.
dore expensive than standard silt
fence.
database is poor.
^o validated urban runoff models
available for theoretical analysis
of downstream impacts.
ome potential exists to modify
existing models to make the
analysis of downstream impacts on
geomorphology.
sfo good cause-effect
relationships
available.
)ther impacts not
evaluated.
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Table 5-27. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.3)
BMP Type
Straw Bale
Dike
Sediment
Traps
Physical Impact Mitigation
Receiving Water Quality
Works by impounding water.
Primary trapping mechanism is by
settling behind straw bale dike.
Information on performance is very
limited with much variation in the
limited data.
Should not be used in waterways or as a
perimeter control due to
biodegradation.
Idealized models of performance are
available for systems that are
properly installed.
Formed by excavation and/or
embankment.
Can simplify stprmwater control by
trapping sediment at specific
spots.
Can be installed quickly and serve as
short-term solution to sediment
trapping in small areas.
May require cleahout.
Detailed models as well as simplified
design aids are available to predict
performance in trapping sediment.
Data on performance are available from
both laboratory studies and field
studies.
Will likely control only the settleable
solids unless enhanced settling is
developed with chemical
Downstream Impacts
Database is poor.
No validated urban runoff models
available for theoretical analysis
of downstream impacts.
Some potential exists to modify
existing models to make the
analysis of downstream impacts on
geomorphology
Database is poor.
No validated urban runoff models
available for theoretical analysis
of downstream impacts.
Some potential exists to modify
existing models to make the
analysis of downstream impacts on
geomorphology.
Other Impacts ,
No good cause-effect
relationships ;
available.
Other impacts not
evaluated. ;
f
-.
Data, for trapping
nutrients are :
available, but show
wide variation.;
General models of ;
nutrient trapping are
not available.
Other impacts not
evaluated. . ;
1
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Table 5-27. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.3)
BMP Type
Sediment
Basins
Physical Impact Mitigation
Receiving Water Quality
Normally formed by construction of a
dam.
Stormwater detention basin may serve
as sediment basin during
construction.
Can be used for any size watershed.
May require cleanout.
Data on performance are available both
from laboratory studies and field
studies.
Will likely control only the settleable
solids unless enhanced settling is
developed with chemical
flocculation.
Most reliable and stable structure for
obtaining high sediment trapping
efficiency under widely varying '
conditions.
Must consider dam safety issues since
dam failure is a reasonable
possibility.
Structures are relatively large and can
be expensive.
Downstream Impacts
Database is poor.
No validated urban runoff models
available for theoretical analysis
of downstream impacts.
Some potential exists to modify
existing models to make the
analysis of downstream impacts on
geomorphology.
Other Impacts
Data for trapping
nutrients are
available, but show
wide variation.
General models of
nutrient trapping are
not available.
Other impacts not
evaluated.
,
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Table 5-28. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.4)
BMP Type
Stone Outlet
Structures
Rock Outlet
Protection
Sump Pit
Storm Drain
Met
Protection
Sediment Tank
Physical Impact Mitigation
Receiving Water Quality
Porous outlet structure constructed of
dumped rock, used as the outlet
for earth dikes.
Requires a stabilized outlet channel
until the flow reaches a stable
channel.
Data on the effectiveness are limited to
visual observations of field installations
where failure was frequent due to poor
installation.
Models are available to predict the
performance of stone outlets, but field
data have not been collected to evaluate
the accuracy of the model.
Used to reduce velocity of flow in
receiving channel and prevent
scouring.
Very effective when properly installed.
Design procedures are well established.
Maintenance is low, if properly
installed.
Should be inspected after high flows.
No data on impact.
Used to dewater during excavation.
Effectiveness not evaluated.
Potential exists to theoretically evaluate
the BMP's effectiveness in
trapping sediment.
Could be used at times other than storm
flow, such as removal of
groundwater flow.
Used to trap sediment that would
otherwise flow into storm drain
inlet.
Should be installed prior to land
disturbance.
Effectiveness in removing sediment has
not been evaluated, but is thought
to be low during construction.
Potential exists to use computer models
to evaluate effectiveness.
Cost can be high for maintenance
requirements.
Should not be used as stand-alone
sediment control.
Portable sediment trap.
Flows are pumped in and out of the
tank.
Used where spaced is limited No
effectiveness data are available.
Expected to be relativelv expensive.
Downstream Impacts
No validated urban runoff models
available for theoretical analysis
of downstream impacts.
Some potential exists to modify
existing models to make the
analysis of downstream impacts on
geomorphology.
No data available.
Database is poor.
No validated urban runoff models
available for theoretical analysis
of downstream impacts.
Some potential exists to modify
existing models to make the
analysis of downstream impacts on
geomorphology.
Database is poor.
No validated urban runoff models
available for theoretical analysis
of downstream impacts.
Some potential exists to modify
existing models to make the
analysis of downstream impacts on
geomorphology.
No data available.
Other Impacts
General models of
nutrient trapping are
not available.
Other impacts not
evaluated.
i
No data available.
No data available.:
No data available.
!
No data available.;
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Table 5-28. Summary of Information on Erosion Control and Prevention BMPs
(Sub-section 5.1.5.4)
BMP Type
Stabilized
Construction
Entrance
Temp Access
Waterways
Crossing
Dust Control
Physical Impact Mitigation
Receiving Water Quality
Used to minimize mud and sediment
attached to motorized vehicles.
Consists of an area that is covered with
rocks over which all vehicles must
drive.
Can be combined with a wash station.
Effective only if all entrances are
maintained.
Relatively expensive.
Will not remove highly cohesive clays.
Stabilizes slopes and decreases runoff
velocity.
Can be incorporated into low-impact
development plans.
Not effective when drainage patterns
are altered.
Mot effective when vegetative areas on
perimeter are destroyed.
Practiced at virtually all construction
sites.
No data available on BMP
effectiveness.
Reduces risk to damaging streambed
from construction equipment
tracking.
Can be a bridge, culvert, or ford.
Bridges and culverts preferred, but
more expensive.
Data on effectiveness in reducing
sediment are not available.
•mportant in arid and semi-arid regions.
Applicable to any construction site.
Construction and sequencing and
limiting exposure area can reduce
problems.
Spray-on adhesives are recommended.
Water application may require near
. constant attention.
ixcess water may cause runoff or
tracking of mud.
Very limited effectiveness information
available.
Costs can vary widely, depending on
local conditions.
Downstream Impacts
No data available.
No data available.
No data available.
No data available.
Other Impacts
No data available.
No data available.
Mo data available.
No data available.
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5.2 REFERENCES !
Adams, J, J. Janatzen, D. Loudenslager. 2000. A Device to Alleviate Pollution from Urban
Stormwater. Design Report, Biosystems and Agricultural Engineering, Oklahoma State
University, Stillwater, OK. j
ASCE. 1999, National Stormwater Best Management Practices (BMP) Database, prepared by the
Urban Water Resources Research Council of the American Society of Civil Engineers,
prepared for the US EPA, Office of Science and Technology, Washington, DC. !
http://www.bmpdatabase.org ;
Barfield, B. J. 2000. Presentation on Nonpoint Source Sediment and Stormwater. University of
Puerto Rico, San Juan, PR.
Barfield, B. J., Bamhisel, R. I., Powell, J. C., Hirschi, M. C., and Moore, I. D. 1983.
Erodibilities and Eroded Size Distribution of Western Kentucky Mine Spoil and
Reconstructed Topsail Final Report for Title HI. Institute for Mining and Minerals
Research, University of Kentucky, Lexington, KY. ;
Barfield, B J., and Clar, M. 1985. Development of New Design Criteria for Sediment Traps and
Basins. Prepared for the Maryland Resource Administration. Annapolis, MD, pp. 33.
Barfield, B. J., Haan, C. T>, Stevens, E., and Hayes, J. C., K. F. Holbrook. 2001. "Engineering
Design Aids for Sediment Control Practices," Proceedings of the International
Symposium on Soil Erosion Research for the 21st Century. January 3-5, 2001. Honolulu,
Hawaii. Symposium Sponsored and Published by American Society of Agricultural
Engineers. St. Joseph, MI. . ^
Barfield, B. J. and Hayes, J. C. 1992. Unpublished Results of Field Evaluation of Sediment
Controls in South Carolina Construction Operations. Biosystems and Agricultural
Engineering, Oklahoma State University, Stillwater, OK.
Barfield, B. J. and Hayes, J. C. 1999. Unpublished Results of Field Evaluation of Sediment
Controls in Louisville, KY Construction Operations. Biosystems and
Agricultural Engineering, Oklahoma State University, Stillwater, OK I
I
Barfield, B. J., Hayes, J. C., Fogle, A. W., and Kranzler, K. A. 1996. "The SEDIMOT III - Model
of Watershed Hydrology and Sedimentology," Proceedings of Fifth Federal Interagency
Sedimentation Conference, Las Vegas, NV. 1996. ;
June 2000
5-124
-------
Development Document for Construction and Development Proposed Effluent Guidelines "
Barfield, B. J., Moore, I. D., and Williams, R. G. 1979. "Sediment Yield in Surface Mined
Watersheds," Proceedings Symposium on Surface Mine Hydrology, Sedimentology, and
Reclamation. College of Engineering, University of Kentucky, Lexington, KY.
Barrett, M. E., Kearney, J. E., McCoy, T. G., Malina, J. F.,Charbeneau, R. J. and Ward, G. H.
1995. An Evaluation of 'the Use and Effectiveness of Temporary Sediment Controls.
Technical Report CRWR 261, Center for Research in Water Resources, The University of
Texas at Austin, Austin, TX 78712.
Benik, S. R., B. N. Wilson, D. D. Biesboer, B. Hanse, and D. Stenlund. 1998. The Efficacy of
Erosion Control Products at a MN/DOT Construction Site. Paper No. 982156, American
-_ Society of Agricultural Engineers, St. Joseph, MI
Blench, T. 1970. Regime Theory Design of Canals with Sand Beds. Proceedings of the
American Society of Civil Engineers. 96(IR2): 205-213.
Britton, S. L., Robinson, K. M., and Barfield, B. J. 2001. Modeling the Effectiveness of Silt
Fence. Proceedings 7th Federal Interagency Sedimentation Conference, Reno, NV.
Brown, W. and D. Caraco. 1997. "Muddy Water In - Muddy Water Out?". Article No. 52 hi
The Practice of Watershed Protection. Center for Watershed Protection, Ellicott City,
MD. 2000. http://www.stormwatercenter.net
Brown, W. and T. Schueler. 1997. The Economics ofStormwater BMPs in the Mid-Atlantic
Region. Prepared for: Chesapeake Research Consortium. Edgewater, MD. Center for
" Watershed Protection, Ellicott City, MD. , -
Brown, W., D. Caraco, R. Claytor, P. Hinkle, H.Y. Kwon, T. Schueler, C. Swann, and J.
Zielinski. 1998. Better Site Design: A Handbook for Changing Development Rules in
Your Community. Prepared by Center for Watershed Protection, Ellicott City, MD, for
the Site Planning Roundtable.
Caraco, D. S. 1997. "Keeping Soil in Its Place." Article No. 55 in The Practice of Watershed
Protection. Center for Watershed Protection, Ellicott City, MD. 2000.
http://www.stormwatercenter.net
CWP. 1996. Design of Stormwater Filtering Systems. Prepared for Chesapeake Research
Consortium, Solomons, MD, and U.S. EPA Region 5, Chicago, EL, by Center for
Watershed Protection, Ellicott City, MD.
Chang, H. H. 1988. Fluvial Processes in River Engineering. Wiley Interscience, New York,
432 p.
June 2000
5-125
-------
Development Document for Construction and Development Proposed Effluent Guidelines [ ._
Claytor, R. 1997. "Practical Tips for Construction Site Phasing." Article No. 54 in The Practice
of Watershed Protection. Center for Watershed Protection, Ellicott City, MD. 2000.
http://www.stormwatercenter.net
Corish, K. 1995. Clearing and Grading Strategies for Urban Watersheds. Environmental Land
Planning Series. Publ. No. 95704. Metropolitan Washington Council of Governments,
Washington, DC. http://www.mwcog.org. i
Coyle, JJ. (USD A). 1979. "Grassed Waterways and Outlets". Engineering Field Manual for
Conservation Practices. U.S. Department of Agriculture, Soil Conservation Service
(SCS).Ch7.p.7-7.
Dorman, M.E., J. Hartigan, R.F. Steg and T. Quasebarth. 1989. Retention, Detention and
Overland Flow for Pollutant Removal from Highway Stormwater Runoff Vol. 1.
Research Report. Federal Highway Administration. FHWA/RD 89/202. Also in:
"Performance of Grassed Swales along East Coast Highways." Article No. 114 in The
Practice of Watershed Protection. Center for Watershed Protection, Ellicott City, MD.
2000. http://www.stormwatercenter.net i
Ellis, B. 1998. A Further Guide to Swales: Costs of Operation and Maintenance. PERMEATE.
Scottish Environmental Protection Agency, Stirling, Scotland.
http://www.sepa.org.uk/guidance/scontrol/swales.htm
Entry, J.A., and R.E. Sojka. 1999. Polyacrylamide Application to Soil Reduces the Movement
of Microorganisms in Water. In 1999 Proceedings of the International Irrigation Show,
Irrigation Association, Orlando, FL, November 9,1999, pp. 93-99.
Ettinger, C. E. and J. E. Lichty. 1979. Evaluation of Performance Capability of Surface Mine
Sediment Ponds. Final Report on Contract Number 68-03-2677, Industrial
Environmental Research Laboratory.
Faircloth, W. 1999. "Searching for a Practical, Efficient, Economical Sediment Basin." In
Proceeding of the 30th Conference of the International Erosion Control Association,
Nashville, TN, Feb. 22-26, pp. 272-282. !
Fifield, J. 2000. Designing for Effective Sediment and Erosion Control on Construction Sites.
Forester Press, Santa Barbara, CA.
Fisher, L. S. and Jarrett, A. R. 1984. "Sediment Retention Efficiency of Synthetic FilterFabric".
Transactions of the American Society of Agricultural Engineers. 30(l):82-89.
June 2000
5-126
-------
Development Document for Construction and Development Proposed Effluent Guidelines
Foster, G. R., Young, R. A., and Neibling, W. H. 1985. "Sediment Composition for Nonpoint
Source Pollution Analyses." Transaction of the American Society of Agricultural
Engineers. 28(1): 133-146.
Goldberg. 1993. Dayton Avenue Swale Biofiltration Study. Seattle Engineering Department
Seattle, WA. F '
Griffin, M. L., Barfield, B. J., and Warner, R. C. 1985. "Laboratory Studies of Dead Storage in
Sediment Ponds". Transactions of the American Society of Agricultural Engineers
28(3):799-804. -
Haan, C. T., Barfield, B. J., and Hayes, J. C. 1994. Design Hydrology and Sedimentologyfor
Small Catchments. Academic Press, San Diego, CA.
Harding, M.V. 1990. Erosion Control Effectiveness: Comparative Studies of Alternative
Mulching Techniques. Environmental Restoration, pp. 149-156, as cited in USEPA.
1993. Guidance Specifying Management Measures for Sources of Nonpoint Pollution in
Coastal Waters. EPA 840-B-92-002. U.S. Environmental Protection Agency, Office of
Water, Washington, DC.
Harper, H. 1988. Effects of Stormwater Management Systems on Groundwater Quality. Final
Report. Environmental Research and Design, Inc. Prepared for Florida Department of
Environmental Regulation. Also in: "Runoff and groundwater dynamics of two swales in
Florida. Article No. 113 in The Practice of Watershed Protection. Center for Watershed
Protection, Ellicott City, MD. 2000. http://www.stormwatercenter.net
Hayes, J. C., B. J. Barfield and R. I. Barnhisel. 1984. Performance of Grass Filters under
Laboratory and Field Conditions. Transactions of the American Society of Agricultural
Engineers 27(5): 1321-1331.
Hayes, J. C. and Barfield, B. J. 1995. "Engineering Aids and Design Guidelines for Control of
Sediment in South Carolina". In South Carolina Stormwater and Sediment Control
Handbook for Land Disturbance Activities. South Carolina Department of Health and
Environmental Control. Columbia, SO.
Hayes, J. C., Akridge, A. L., Barfield, B. J. and Holbrook, K. F. 2001. "Simplifying Design of
Sediment Controls in Jefferson County, Kentucky". In Proceedings of Soil Erosion
Research for the 21st Century: An International Symposium and Exhibition, Honolulu,
HI, January 2001. Sponsored by the American Society of Agricultural Engineers.
June 2000
5-127
-------
Development Document for Construction and Development Proposed Effluent Guidelines ;
Herrera, N. M. and G. K. Felton. 1991. "Hydraulics of Flow through a Rockfill Dam Usuig
Sediment-Free Water." Transactions of the American Society of Agricultural Engineers.
34(3):871-875. j
Heyer, T. No Date. Vegetative Measures for StreambankStabilization. U.S. Department of
Agriculture, Forest Service, St. Paul, MN. |
Hirschi, M. C. 1981. "Efficiency of Small Sediment Controls." Unpublished Agricultural
Engineering File Report, Agricultural Engineering, University of Kentucky, Lexington,
KY. (Details of the report are given in Chapter 9 of Haan et al, 1994).
Holbrook, K. F.5 Hayes, J. C. and Barfield, B. J., and A.W. Fogle. 1998. "Engineering Aids and
Design Guidelines for Control of Sediment in South Carolina," In Proceedings of the
International Erosion Control Association Conference. February 1998. '
IDNR. 1992. Indiana Handbook for Erosion Controls in Developing Areas, Guidelines for
Protecting Water Quality through the Control of Soil and Erosion and Sedimentation on
Construction Sites. Division of Soil Conservation, Indiana Department of Natural
Resources, Indianapolis, EN. !
Jarrett, A. 1999. "Designing Sedimentation Basins for Better Sediment Capture". In Proceeding
of the 30th Conference of the International Erosion Control Association, Nashville, TN,
Feb. 22-26, pp. 218-233. :
Kay-Shoemake, J, M. Watwood, R. Sojka, and R. Lentz. 2000. "Soil Amidase Activity in
Polyacrylamide (PAM) Treated Soils and Potential Activity toward Common Amide
Containing Agrochemicals". Biology and Fertility of Soils 31(2): 183-186. >
Kercher, W.C., J.C. Landon and R. Massarelli. 1983. "Grassy Swales Prove Cost-Effective for
Water Pollution Control. Public Works 16: 53-55.
Knisel, W. G., ed. 1980. CREAMS: A Field-Scale Model for Chemicals, Runoff, and Erosion
from Agricultural Management Systems. U. S. Department of Agriculture, Conservation
Research Report No. 26, 640pp. . ' •
Koon, J. 1995. Evaluation of Water Quality Ponds and Swales in the Issaquah/East Lake
Sammamish Basins. King County Surface Water Management and Washington
Department of Ecology, Seattle, WA. |
Kouwen, N. 1990. Silt Fences to Control Sediment on Construction Sites. Technical
Publication MAT-90-03, Research and Development Branch, Ontario Ministry of
Transportation, 1201 Wilson Avenue, Downsview, Ontario, Canada M3M 1J8. ;
June 2000
5-128
-------
Development Document for Construction and Development Proposed Effluent Guidelines
Lane, E. W. 1955. "The Importance of Fluvial Geomorphology in Hydraulic Engineering".
Proceedings oj'the American Society of'Civil Engineers, 81: 1-17.
Leopold, Luna B., M. Gordon Wolman, and John P. Miller, 1964. Fluvial Processes in
Geomorphology. Dover Publications, Inc. Mineola, NY.
Lindley, M., B. J. Barfield, J. Ascough, B. N. Wilson, and E. Stevens. 1998. "The Surface
Impoundment Element for WEPP". Transactions of the American Society of Agricultural
Engineers. 41(3):555-564.
Masters, A., K. A. Flahive, S. Mostaghimi, D. Vaughan, A. Mendez, M. Peterie, S. Radke. 2000:
A Comparative Investigation of the Effectiveness ofPolyacrylamide (PAM)for Erosion
Control in Urban Areas. Paper No. 002176, American Society of Agricultural Engineers,
St. Joseph, MI, pp. 21.
McBurnie, J. C., Barfield, B. J., Clar, M. L. and Shaver, E. 1990. "Maryland Sediment
Detention Pond Design Criteria and Performance". Applied Engineering in Agriculture.
6(2):167-173. . "
MDE. 1994. Maryland Standards and Specifications for Soil Erosion and Sediment Control.
Water Management Administration, Maryland Department of the Environment, Soil
Conservation Service, and State Soil Conservation Committee, Baltimore, MD.
NAHB. No Date. NAHB Research Center Storm Water Runoff & Nonpoint Source Pollution
Control Guide for Builders and Developers. National Association of Home Builders,
Washington, DC.
NCDNR. 1988. North Carolina Erosion and Sediment Control Planning and Design Manual.
North Carolina Sedimentation Control Commission, the North Carolina Department of
Natural Resources and Community Development, and the North Carolina Agricultural
Extension Service, Raleigh, NC.
Oakland, P.H. 1983. "An Evaluation of Stormwater Pollutant Removal through Grassed Swale
Treatment." In Proceedings of the International Symposium of Urban Hydrology,
Hydraulics and Sediment Control, H. J. Sterling, Lexington, KY.
Occoquan Watershed Monitoring Laboratory. 1983; Final Report: Metropolitan Washington
Urban Runoff Project. Prepared for the Metropolitan Washington Council of
Governments. Manassas, VA.
June 2000
5-129 '
-------
Development Document for Construction and Development Proposed Effluent Guidelines \
Pitt, R. and J. McLean. 1986. Toronto Area Watershed Management Strategy Study: Number
River Pilot Watershed Project. Ontario Ministry of Environment and Energy, Toronto,
Ontario, Canada.
Roa-Espinosa, A., G.D. Bubenzer, and E.S.Miyashita. 2000. Sediment and Runoff Control on
Construction Sites Using Four Application Methods of Polyacrylamide Mix. National
Conference on Tools for Urban Water Resource Management and Protection, Chicago,
IL, February 7-10,2000, pp. 278-. ;
Renard, K. G., Foster G. R., Weesies, G. A., McCool, KD. K. and Yoder D. C. 1994. Predicting
Soil Erosion by Water—A Guide to Conservation Planning with the Revised Universal
Soil Loss Equation (RUSLE). Agricultural Research Service Publication, U.S.
Department of Agriculture.
Rosgen, D. L., 1996. Applied River Morphology. Wildland Hydrology, Pagosa Springs, CO.
Seattle Metro and Washington Department of Ecology. 1992. Biqfiltration Swale Performance:
Recommendations and Design Considerations. Publication No. 657. Water Pollution
Control Department, Seattle, WA. Also in: Watershed Protection Techniques. Fall 1994
1(3): 117-119. ;
SCDHEC. 1995. South Carolina Stormwater Management and Sediment Reductions
Regulations. In South Carolina Stormwater Management and Sediment Control
Sedimentology Resource, South Carolina Department of Health and Environmental
Control. Columbia, SC.
Schumm, S. A. 1977. The Fluvial System. John Wiley and Sons, New York. 338pp.
Simons, D.B., and M.L. Albertson, 1960. "Uniform Water Conveyance Channels in Alluvial
Material." Proceedings of the American Society of Civil Engineers. 86(HY5):33-71.
Smiley, J., and C. T. Haan. 1976. "The Dam Problem of Urban Hydrology". Proceedings of the
National Symposium on Urban Hydrology, Hydraulics, and Sediment Control. Cpllege
of Engineering, University of Kentucky, Lexington, KY.
Smolen, M.D., D.W. Miller, L;C. Wyall, J. Lichthardt, and A.L. Lanier. 1988. Erosion and •
Sediment Control Planning and Design Manual. North Carolina Sedimentation Control
Commission and North Carolina Department of Natural Resources and Community
Development, Raleigh, NC.
June 2000
5-130
-------
Development Document for Construction and Development Proposed Effluent Guidelines
Snodgrass, W.J., B.W. Kilgour, L. Leon, N. Eyles, J. Parish, and D.R. Barton. 1998. "Applying
Ecological Criteria for Stream Biota and an Impact Flow Model for Evaluation of
Sustainable Urban Water Resources in Southern Ontario". In: Sustaining Urban Water
Resources in the 21st Century. Proceedings for an Engineering Foundation Conference.
Edited by A.C. Rowney, P. Stahre, and L.A. Roesner. Malmo, Sweden. September 7 -
. 12, 1997.
Stahre, P., and B. Urbonas. 1990. Stormwater Detention For Drainage, Water Quality, and
CSO Management. Prentice Hall, Englewood Cliffs, NJ.
SWRPC. 1991. Costs of Urban Nonpoint Source Water Pollution Control Measures. Technical
report no. 31. Southeastern Wisconsin Regional Planning Commission, Waukesha, WI.
Tobiason, S., D. Jenkins, E. Molash, and S. Rush. 2000. "Polymer Use and Testing for Erosion
and Sediment Control on Construction Sites: Recent experience in the Pacific
Northwest". In: Proceedings of Conference 31. International Erosion Control
Association. Palm Spring, CA, February 21-25, 2000, pp. 41-52.
Tapp, J. S., and Barfield, B. J. 1986. "Modeling the Flocculation Process in Sediment Ponds".
Transactions American Society of 'Agricultural Engineers. 29(3):''41-747.
Tapp, J. S., Barfield, B. J., and Griffin, M. L. 1981. Predicting Suspended Solids Removal in
Pilot Scale Sediment Ponds Utilizing Chemical Flocculation. Research Report IMMR
81/063, Institute for Mining and Minerals Research, University of Kentucky, Lexington,
KY.
UNEP. 1994. Guidelines for Sediment Control Practices in the Insular Caribbean. CEP
Technical Report No. 32. UNEP Caribbean Environment Programme, Kingston,
Jamaica, http://www.cep.unep.org/pubs/techreports/tr32en/content.html
USAF. 1998. USAF Landscape Design: Erosion Control Measures. U.S. Air Force, St Paul
' . MN.
http://www.afcee.brooks.af.mil/ldg/sl8erosioncontrol/cQ3process.html
USDOT. 1995. Best Management Practices for Erosion and Sediment Control. Report No.
FHWA-FLP-94-005. Eastern Federal Lands Highway Design, U.S Department of
Transportation, Sterling, VA.
USDA andNRCS, 1985. National Engineering Handbook. Natural Resources Conservation
Service, Soil Conservation Services.
June 2000
5-131
-------
Development Document for Construction and Development Proposed Effluent Guidelines •
USEPA. 1,971. Control of Sediment Resulting from Construction of Highways and Land
Development. U.S. Environmental Protection Agency, Washington, DC.
USEPA. 1992. Storm Water Management for Construction Activities: Developing Pollution
Prevention Plans and Best Management Practices. EPA 832-R-92-005. U.S. I
Environmental Protection Agency, Office of Water, Washington, DC. '
USEPA. 1992. Storm Water Management for Industrial Activities: Developing Pollution
Prevention Plans and Best Management Practices. EPA 832-R-92-006. U.S.
Environmental Protection Agency, Office of Water, Washington, DC.
USEPA. 1993. Guidance Specifying Management Measures for Sources ofNonpoint Pollution
in Coastal Waters. EPA 840-B-927002. U.S. Environmental Protection Agency, Office
of Water, Washington, DC. >
USEPA. 2000. Urban Nonpoint Source Management Measure Guidance -Draft. U.S. j
Environmental Protection Agency, Office of Water, Washington, DC. ;
Vanderwel, D. and S. Abday. 1998. An Introduction to Water Erosion Control. Alberta,
Agriculture, Food and Rural Development, Alberta, Canada. ;
VDCR. 1995. Virginia Erosion & Sediment Control Field Manual. Second Edition. Virginia
Department of Conservation and Recreation, Division of Soil and Water Conservation,
Richmond, VA.
VDCR. 2001. Virginia Erosion and Sediment Control Law, Regulations, and Certification
Regulations. Virginia Department of Conservation and Recreation, Division of Soil and
Water Conservation, Richmond, VA. |
Wang, T., D. Spyridakis, B. Mar and R. Horner. 1981. Transport, Deposition and Control of
Heavy Metals in Highway Runoff. FHWA-WA-RD-39-10. Department of Civil
Engineering. University of Washington, Seattle, WA. [
Ward, A. D., Haan, C. T., and Barfield, B. J. 1977. Simulation of the Sedimentology of Sediment
Detention Basins. Research Report No. 103, Water Resources Research Institute,
University of Kentucky, Lexington, KY.
Ward, A. D., Haan, C. T., and Tapp, J. S. 1979. The DEPOSITS Sedimentation Pond Design
Manual. OISTL, Institute for Mining and Minerals Research, University of Kentucky,
Lexington, KY. I
June 2000
5-132
-------
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Washington State Department of Ecology (WDEC). 1992. Stormwater Management Manual for
the Puget Sound Basin. Technical Manual. Washington State Department of Ecology,
Olympia, WA.
Welborn, C., and J. Veenhuis. 1987. Effects of Runoff Controls on the Quantity and Quality of
Urban Runoff in Two Locations in Austin, TX. U.S. Geological Survey Water Resources
Investigations Report. 87-4004, pp. 88.
Williams, J. R. No Date. "Sediment Yield Prediction with Universal Equation Using Runoff
Energy Factor". Present and Prospective Technology for Predicting Sediment Yields and
Sources-. Publication ARS-S-40, Agricultural Research Service, U.S. Department of
Agriculture, Washington, DC.
Wilson, B. N., and Barfield, B. J. 1984. "A Sediment Detention Pond Model Using CSTRS
Mixing Theory." Transactions American Society of Agricultural Engineers. 27(5);1339-
- . 1344.
Wilson, B. N., Barfield, B. J., and Moore, I. D. 1982. A Hydrology and Sedimentology
Watershed Model. Department of Agricultural Engineering, University of Kentucky,
Lexington, KY.
Wischmeier, W. H. and D. D. Smith. 1965. Predicting Rainfall-Erosion Losses From Cropland
East of the Rocky Mountains-Guide for Selection of Practices for Soil and Water
Conservation. U. S. Department of Agriculture, Agricultural Handbook No. 282. 47 pp.
Wishowski, J. M., Mamo, M., and Bubenzer, G. D. 1998. Trap Efficiencies of Filter Fabric
Fence. Paper No 982158, American Society of Agricultural Engineers, St. Joseph, MI.
Wyant, D. C. 1980. Evaluation of Filter Fabric for Use as Silt Fences. VA Highway and
Transportation Research Council, Richmond, VA.
WYDEQ. 1999. Urban Best Management Practices for Nonpoint Source Pollution. Point and
Nonpoint Source Programs; Water Quality Division, Wyoming Department of
Environmental Quality, Cheyenne, WY.
http://deq.state.wv.us/wqd/watershed/92171.pdf
Yousef, Y., M. Wanielista, H. Harper, D. Pearce and R. Tolbert. 1985. Best Management
Practices: Removal of Highway Contaminants by Roadside Swales. Final report.
University of Central Florida. Florida Department of Transportation. Orlando, FL. Also
in: "Pollutant Removal Pathways in Florida Swales". Watershed Protection Techniques
Fall 1995. 2(1): 299-301.
June 2000
5-133
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Yu, S., S. Barnes and V. Gerde. 1993. Testing of Best Management Practices for Controlling
Highway Runoff. Virginia Transportation Research Council. FHWA/VA-93-R16, pp. 60.
Also in: Performance of Grassed Swales Along East Coast Highways. Article No, 114 in
The Practice of Watershed Protection. Center for Watershed Protection, Ellicott City,
MD. 2000. http://www.stormwatercenter.net
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SECTION 6: REGULATORY DEVELOPMENT AND RATIONALE
In this section, the methodology used by EPA to develop regulatory options for the construction
and land development industry is described. EPA methodology first evaluated the pollutants
discharged from the industry and evaluated existing Federal, State and local control strategies
designed to manage impacts. Based on this analysis, EPA was able to identify several key
components of existing regulatory strategies that would be applicable for national effluent
guidelines regulations and develop regulatory options around these existing strategies. Following
development of regulatory options, EPA evaluated the costs and environmental benefits of
several options and determined the appropriate option for proposal based on factors such as total
costs, monetized and non-monetized environmental benefits, ease of implementation, industry
financial impacts, and industry acceptance. The following sections describe the components of
this process involving identification of impacts, evaluation of available control strategies, and
formulation of regulatory options. Costs of regulatory options are discussed in Section 7 of this
document while a description of the environmental benefits estimation and industry financial
analyses, can be found in the other supporting documents of this regulation (USEPA 2002 and
2002a). .
6.1 IDENTIFICATION OF INDUSTRY IMPACTS
In developing effluent guidelines for controlling storm water discharges associated with
construction and land development activities, EPA identified pollutants that are attributable to
the industry. In addition to pollutants discharged from construction sites and from long-term
storm water discharges, EPA also looked at the broader range of environmental impacts that the
land development process influences and that could potentially be addressed under effluent
guidelines regulations. These categories include physical impacts to receiving streams due to the
increased frequency of high flow rates and associated discharge of sediment, as well as, thermal
impacts to receiving waters due to the increased temperature of storm water discharges.
These analyses helped EPA to develop regulatory options and associated estimates of costs and
benefits for temporary erosion and sediment controls. This approach allowed for the evaluation
of different combinations of regulatory options when developing an overall regulatory strategy
for this industry, with different combinations addressing various impact areas.
6.1.1 Pollutant Indicators
When determining which pollutants to assess, EPA applied the following priorities for
construction storm water discharges:
Focus on pollutants directly attributable to the industry, using indicator pollutants where
necessary; .
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• Focus on pollutants most commonly encountered under most settings, (i.e., not to pre-
construction site contamination issues or accidental discharges);
•, Focus on pollutants that are most manageable given the current suite of available
technologies; and
• Focus on pollutants that can be addressed under the authority of effluent guidelines. '
EPA conducted an extensive evaluation of the literature to identify pollutants present in siorm
water discharges from construction and land development sites. While the literature contains
extensive information on pollutants present in storm water discharges from urban areas, there
were little data available on pollutants present in storm water discharges from construction sites
during the active construction phase other than for sediment, TSS and turbidity. This is not
surprising, since construction site storm water management is primarily concerned with the
control of solids from exposed soil areas. There is the potential for other pollutants to be
discharged from construction sites depending on factors such as prior land uses. For example, if
the prior land use was agriculture, there is the potential for discharge of pollutants such as
nutrients and pesticides. Likewise, areas of redevelopment that occur on sites where previous
land uses included industry could discharge pollutants such as organics and metals. In addition,
pollutants such as metals and nutrients can be present in native site soils, and could be discharged
from construction sites. However, EPA was not able to identify sufficient data in the literature to
warrant development of controls specific to pollutants other than sediment, TSS and turbidity in
storm water discharges from construction sites. Some literature suggests that pollutants adhere to
sediment so regulating TSS should also act as a control for other pollutants.
There are extensive data in the literature describing pollutants present in storm water discharges
from urban areas. The most comprehensive evaluation of urban storm water was the Nationwide
Urban Runoff Program (NURP) (USEPA, 1983). While somewhat dated, the NURP results are
still valid, and serve as a primary means of characterizing urban runoff pollutants. In addition to
NURP, a variety of other analyses conducted over the past 20 years have contributed greatly to
the understanding of pollutants present in urban storm water runoff. Literally thousands of
references can be found in the literature summarizing hundreds of studies evaluating urban runoff
pollutant levels. As a result, there are sufficient data available to identify the major pollutants
expected to be discharged from new land development activities. Based on these data sources,
EPA identified sediments (measured as TSS), nutrients and metals as pollutants of concern for
this industry. EPA also evaluated the inclusion of organics, pesticides, and bacteria as potential
pollutants of concern, but the literature indicates that control of these pollutants through
conventional storm water management strategies is potentially much more difficult, and that
there are little data linking their presence in storm water discharges directly with new land
development activities. Source control may factor greatly into controlling these pollutant
sources.
Although EPA identified a number of pollutants of concern for this industry, EPA did not
develop regulatory options specifically targeted at controlling each of these individual pollutants.
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Instead, EPA chose to develop regulatory options using an indicator pollutant, TSS. While TSS
levels may not be directly correlated with all pollutants of concern, it is certainly the most widely
reported parameter in the literature due to its relative ease of collection and low cost. In addition,
design of management systems for the control of TSS will likely result in control of pollutants
such as sediment, nutrients and metals that are present in the solid-phase (attached to sediments).
The one pollutant of concern that may not have a strong correlation with TSS is turbidity, since
particles that contribute to turbidity may not be removed through conventional storm water
management practices that control TSS. Particles' that contribute to turbidity may be of such a
fine grain that they will not be removed by the mechanisms whereby most BMPs operate, mainly
settling and filtration.
EPA's assessment of pollutant loadings for the industry was based on mathematical models.
These models were developed using analyses prepared by EPA for the NPDES Phase n
rulemaking (USEPA, 1999), established hydrologic principles and storm water monitoring data
from the literature. EPA estimated annual loadings with and without effluent guidelines from
construction site storm water discharges using 225 site models which varied based on location,
site size and site slope. In its assessment of the industry, EPA elected to use the estimated land
area constructed annually in the nation for the contiguous states, based on the National Resources
Inventory (NRI)(USDA, 2000). EPA did not develop estimates of pollutant loadings for Alaska,
Hawaii, and the U.S. territories, due to a several factors, such as a lack of rainfall data and lack of
data on annual land development. However, due to' the small amount of development that occurs
in these areas, the omission of these areas from the analysis is not expected to contribute a
significant error to EPA's national estimates.
In developing pollutant loadings of the land development industries, a distinction was made
between primary pollutant loadings (e.g., discharge of sediments from disturbed ground surfaces)
and secondary pollutant loadings (e.g., loadings resulting from accelerated erosion of streams
caused by increased high flows from urbanized land uses). This distinction was made because
studies focusing on the impacts of land development have sometimes neglected the secondary
pollutant loadings that result when changes to hydrology cause downstream channels to become
unstable. The secondary pollutant loadings that occur year after year from increased stream
flows have not been well inventoried.1
1 Not all pollutant indicators listed above are directly used by EPA in its benefits
assessment, or in developing the C&D effluent guidelines. Nevertheless, EPA has collected data
to estimate all of the measures for potential future consideration of this and other
industries/activities.
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6.1.2 Physical/Habitat Indicators
In addition to assessing impacts of the construction and land development industry due to
discharge of pollutants in storm water, EPA also developed a methodology for assessing the
physical and habitat impacts caused by changes in hydrology and stream flow. Land
development activities cause significant alterations in the natural hydrologic regime of '
developing watersheds. The removal of vegetation., the compaction of soils by construction
equipment and the construction of impervious surfaces such as roads, driveways and buildings
causes a marked increase in the total volume and peak flow rate of storm water discharges as
compared to forested, open and agricultural land uses. As a result, streams receiving storm water
discharges will frequently undergo significant channel alterations in order to adjust to the altered
hydrologic regime. This alteration results in mobilization of high quantities of sediment and
associated water quality problems. . ; '
EPA's assessment attempted to develop an impacts time line, predicting when certain impacts
will occur. Due to its relatively short duration, construction impacts (or benefits) were assumed
to occur within a single year. The assessment of long-term impacts was based on the 30 year
period immediately following conversion into urban land use. This includes characterization of
physical/habitat impacts related to hydrologic changes (e.g., increased flooding and stream
erosion) and changes in runoff characteristics (e.g., runoff thermal signature). In its modeling
effort, EPA made assumptions that simplify (spatial and temporally) land development,
compressing the period required for land to reach "build-out." EPA performed sensitivity
evaluations to verify that these simplifications do not distort or abrogate its assessment of
potential environmental impacts. ;
Physical/Habitat Measures Estimated by EPA2 include: '.
• Miles of stream urbanized (located within the area urbanized nationally in a single year)
• Number of new stream crossings expected to become fish migration barriers
• Acres of stream habitat lost to new stream crossings
• Acres of stream-side area flooded by the 100-year rainfall event
• Tons of stream bank/bed sediment removed as a result of increased high flow rate frequency
A detailed discussion of EPA's environmental assessment methodology and results is presented
in other supporting documents of this rule (USEPA, 2002 and 2002a). :
2 Not all physical/habitat measures listed above are directly used by EPA in its benefits
assessment, or in developing the C&D effluent guidelines. Nevertheless, EPA has collected data
to estimate all of the measures for potential future consideration of this and other !
industries/activities.
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6.2 DEVELOPMENT OF REGULATORY OPTIONS
In developing effluent guidelines for the construction and development industries, EPA evaluated
a variety of state and local programs to identify various management strategies and regulatory
components that would be applicable on a national basis. For erosion and sediment control and
other temporary BMPs, EPA considered a series of regulatory options. These options are
designed to control the discharge of sediment, storm water and other pollutants from sites when
construction is taking place. EPA considered a range of options that incorporate varying levels
of management and various control strategies. Because long-term storm water management is
beyond the scope of the controls proposed by EPA, the following discussion only presents
information related to options for controlling storm water during the active phase of construction.
The following discussion presents various options that EPA considered.
Codify the EPA Construction General Permit
EPA considered an option that would essentially codify the provisions contained in EPA's
construction general permit (CGP) (USEPA, 1998) as minimum national standards for erosion
and sediment control (i.e., for all states, not only those with EPA as permitting authority) for sites
of 5 acres or more of disturbed land. Requirements include preparing a Storm Water Pollution
Prevention Plan (SWPPP) or equivalent, provisions for installing and sizing sediment basins on
sites with more than 10 acres of disturbed land, requirements for providing cover on exposed soil
areas within 14 'days after construction activity has ceased, and installation and maintenance of
other erosion and sediment control practices and other temporary BMPs on all construction sites,
such as silt fencing, seeding and mulching, diversion dikes and berms, sediment traps, storm
drain inlet protection, channel liners, erosion control blankets and mats, stabilized construction
entrances, litter, trash and debris control, discarded building material control, and concrete truck
wash water control.
Numerical Design Requirements
EPA considered an option that would establish numerical requirements for the design of
sediment basins and traps based on local or regional rainfall patterns and site-specific soil types.
This options could be similar to existing requirements designed for managing storm water
discharges, where sediment controls are sized based on a specified rainfall return frequency (such
as the 2-year; 24-hour storm), or a specified runoff frequency (such as the 90th percentile runoff
event).
Numerical Pollutant Removal Requirements
,EPA considered options that would contain numerical requirements for the removal of specific
pollutants from construction site runoff. EPA initially considered targeting a variety of pollutants
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including sediment, TSS, turbidity, nutrients, metals and other priority pollutants, however there
are little data available supporting the feasibility of controlling pollutants other than sediment (or
associated indicator parameters such asTJ3S, turbidity, total suspended sediment, or settleable
solids). This option could be expressed as either a percent removal through sediment controls
(such as sediment basins or traps), or as a total site reduction (incorporating consideration of
sheet flow and diffuse runoff in addition to discrete conveyances); In addition to establishing
numerical requirements for the control of sediment, EPA preliminarily considered establishing
requirements for removing fine-grained and slowly- or non-settleable particles contained in
construction-site runoff (such as turbidity). This option would likely have relied primarily on
chemical treatment of soils or construction site runoff using polymers or coagulants such as alum
in order to prevent the non-settleable fractions of solids from being transported off-site.
Discharge Monitoring
EPA considered the inclusion of monitoring requirements for evaluating the effectiveness of
erosion and sediment controls. Monitoring of storm water discharges from construction sites
could be used to evaluate the effectiveness of individual sediment controls (such as sediment
basins), or monitoring the receiving water above and below construction sites. Monitoring
requirements could be incorporated with any of the previously discussed regulatory options
considered. . '
i
Inspection and Certification i
EPA considered an option that includes mandatory site inspection, maintenance and reporting
provisions by site owners and operators in order to improve confidence in the implementation
and performance of construction site erosion and sediment controls. These certification
provisions maybe accomplished either through self-inspection by a qualified employee of the
owner and operator (such as a professional engineer or person trained in erosion and sediment
control techniques) or inspection by a third-party (such as a consulting firm). The certification
provisions would consist of a checklist-type certification form that the permittee would be
required to complete at various stages of the project to certify that the provisions contained in the
permittee's SWPPP are being implemented, hi addition, the permittees would be required to
conduct periodic inspections in order to confirm that the permittee is conducting the maintenance
necessary to maintain the functionality of BMPs. The specific activities requiring certification
include: SWPPP preparation; installation of perimeter controls and sediment controls; site
inspections every 14 days; final stabilization of exposed soils and removal of temporary erosion
& sediment controls. The certification and inspection forms would be retained on the site, and
made available to the permitting authority and the public upon request. | -
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6.3 REGULATORY OPTIONS DEVELOPED FOR THE PROPOSED RULE
6.3.1 Option 1 - Inspection and Certification
Option 1 proposed by EPA would establish the site inspection and certification provisions
discussed above as minimum requirements for all construction sites subject to the NPDES storm
water regulations. This includes sites from 1 up to 5 acres that will be required to obtain a permit
once the Phase II regulations are implemented and sites 5 acres or greater that are required to
obtain a permit under the Phase I regulations. The permittee would be required to conduct
periodic inspections and provide certifications as to certain activities (such as SWPPP
preparation, BMP installation, periodic maintenance, etc.). Under this option, these inspections
and certifications would be performed by a qualified professional, such as a registered
professional engineer or person trained in erosion and sediment control. The permittee may
provide self-certifications if qualified.
The specific inspection and certification provisions can be found in the proposed rule language
and are summarized below:
Site log book. The permittee would be required to maintain a record of site activities in a site log
book. The specific requirements and information contained in the log book consists of the
following:
(1) A copy of the site log book would be required to be maintained on site and be made
available to the permitting authority upon request. EPA recommends that the permittee also
make a copy of the site log book available to the public upon request within a reasonable
period;
(2) In the site log book, the permittee shall certify, prior to the commencement of construction
activities, that'any plans required by the permit meet all Federal, State, Tribal and local
erosion and sediment control requirements and are available to the permitting authority;
(3) The permittee would be required to have a qualified professional, conduct an assessment of
the site prior to groundbreaking and certify that the appropriate BMPs described in plans
required by the permit have been adequately designed, sized and installed to ensure overall
preparedness of the site for initiation of groundbreaking activities. The permittee would be
required to record the date of initial groundbreaking in the site log book. The permittee
would also be required to identify and conduct any soil stabilization and BMP maintenance
requirements identified in the permit within 48 hours of their identification;
(4) The permittee would be required to post at the site, in a publicly-accessible location, a
summary of the site inspection activities on a monthly basis. EPA recommends that the
permittee provide contact information for obtaining a copy of the site inspection log book;
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Site Inspections. The permittee or designated agent of the permittee (such as a consultant,
subcontractor, or third-party inspection firm) would be required to conduct regular inspections of
the site and record the results of such inspection in the site log book. Specific inspection
provisions include:
(1) After initial groundbreaking, permittees would be required to conduct site inspections at
least every 14 calendar days and within 24 hours of the end of a storm event of 0.5 inches or
greater. These inspections would be required to be conducted by a qualified professional.
During each inspection, the permittee or designated agent would be required to conduct the
following activities and record the following information:
(i) Indicate the extent of all disturbed site areas and drainage pathways. Indicate site
areas that are expected to undergo initial disturbance or significant site work
within the next 14-day period;
(ii) Indicate all areas of the site that have undergone temporary or permanent
stabilization; - . :
(iii) Indicate all disturbed site areas that have not undergone active site work during
the previous 14-day period;
(iv) Inspect all sediment control practices and note the approximate degree of
sediment accumulation as a percentage of the sediment storage volume (for
example 10 percent, 20 percent, 50 percent, etc.). Note all sediment control
practices in the site log book that have sediment accumulation of 50 percent or
more; and i
(v) Inspect all erosion and sediment control BMPs and note compliance with any
maintenance requirements such as verifying the integrity of barrier or diversion
systems (e.g., earthen berms or silt fencing) and containment systems (e.g.,
sediment basins and sediment traps). Identify any evidence of rill or gully erosion
occurring on slopes and any loss of stabilizing vegetation or seeding/mulching.
Document in the site log book any excessive deposition of sediment or ponding
water along barrier or diversion systems. Note the depth of sediment within
containment structures, any erosion near outlet and overflow structures, and verify
the ability of rock filters around perforated riser pipes to pass water.
(2) Prior to filing of the Notice of Termination or the end of permit term, the permittee or
designated agent would be required to conduct a final site erosion and sediment control
inspection. The inspector would be required to certify that the site has undergone final
stabilization as required by the permit and that all temporary erosion and sediment controls
(such as silt fencing) not needed for long-term erosion control have been removed.
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6.3.2 Option 2 - Codify EPA CGP Requirements with Site Inspection and Certification
Provisions
Option 2 proposed by EPA would require the permittee to prepare a storm water pollution
prevention plan (SWPPP) and implement the erosion and sediment controls contained in the
EPA CGP. In addition, the permittee would be required to conduct periodic site inspections and
provide certifications in a site log book This option would only apply to sites with 5 or more
acres of disturbed land., The details of this option can be found in the proposed rule language and
are summarized below:
General Erosion and Sediment Controls
Each SWPPP would be required to include a description of appropriate controls designed to
retain sediment on site to the extent practicable. These general erosion and sediment controls
would be required to be included in the SWPPP described below. The SWPPP would be
required to include a description of interim and permanent stabilization practices for the site,
including a schedule of when the practices will be implemented. Stabilization practices may
include:
(1) Establishment of temporary or permanent vegetation;
(2) Mulching, geotextiles, or sod stabilization;
(3) Vegetative buffer strips;
(4) Protection of trees and preservation of mature vegetation.
EPA recommends that all controls be properly selected and installed in accordance with sound
engineering practices and, when feasible, manufacturer's specifications.
Sediment Controls
Operators would be required to design and install structural controls to divert flows from exposed
soils, store flows or otherwise limit runoff and the discharge of pollutants from exposed areas
and to describe controls in the SWPPP. These controls are as follows:
(1) For common drainage locations that serve an area with 10 or more acres disturbed at one
time, the operator would be required to provide a temporary (or permanent) sediment basin
that provides storage for a calculated volume of runoff from a 2 year, 24-hour storm from
each disturbed acre drained, or equivalent control measures, where attainable until final
stabilization of the site. Where no such calculation has been performed, the operator would
be required to provide a temporary (or permanent) sediment basin providing 3,600 cubic feet
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^ . !
feet of storage per acre drained, or equivalent control measures, where attainable until final
stabilization of the site. When computing the number of acres draining into a comnjon
location it is not necessary to include flows from off-site areas and flows from on-site areas
that are either undisturbed or have undergone final stabilization where such flows are
diverted around both the disturbed area and the sediment basin. :
(2) In determining whether a sediment basin is attainable, the operator may consider factors
such as site soils, slope, available area on site, etc. hi any event, the operator wouldibe
required to consider public safety, especially as it relates to children, as a design factor for
the sediment basin. Use of alternative sediment controls would be required where site
limitations preclude a safe basin design. '
(3) For portions of the site that drain to a common location and have a total contributing
drainage area of less than 10 acres, the operator would be required to consider installation of
sediment traps or other sediment control devices. •
(4) Where neither a sediment basin nor equivalent controls are attainable due to site limitations,
the operator would be required to install silt fences, vegetative buffer strips or equivalent
sediment controls for all down slope boundaries of the construction area and for those side
slope boundaries deemed appropriate for individual site conditions.
Pollution Prevention Measures
The operator would be required to implement the following pollution prevention measures:
(1) The operator would be required to prevent litter, construction chemicals, and construction
debris from becoming a pollutant source in storm water discharges; and ;
(2) The operator would be required to contain construction and building materials in .
appropriate storage areas and manage the materials to prevent contamination of storm water
runoff. . !
Storm Water Pollution Prevention Plan ;
Permittees would be required to compile Storm Water Pollution Prevention Plans (SWPPPs)
prior to groundbreaking at any construction site. In areas where EPA is not the permit authority,
operators may be required to prepare documents that may serve as the functional equivalent of a
SWPPP. Such alternate documents would satisfy the requirements for a SWPPP so long;as they
contain the necessary elements of a SWPPP. A SWPPP would be required to incorporate the
following information:
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(1) A narrative description of the construction activity, including a description of the intended
sequence of major activities that disturb soils on the site (Major activities include any
clearing, grubbing, excavating, grading, soil stockpiling, and utilities and infrastructure
installation, or any other activity that results in significant disturbance of soils.);
(2) A general location map (e.g., portion of a city or county map) and a site map. The site map
shall include descriptions of the following:
(i) Drainage patterns and approximate slopes anticipated after major grading
activities;
(ii) The total area of the site and the area of the site that is expected to be disturbed by
excavation, clearing,, grading and other construction activities during the life of
the permit; - '
(iii) Areas that will not be disturbed;
(iv) Locations of erosion and sediment controls identified in the SWPPP;
(v) Locations where stabilization practices are expected to occur;
(vi) Locations of off-site material, waste, borrow or equipment storage areas;
(vii) Surface waters (including wetlands); and
(viii) Locations where storm water discharges to a surface water;
(3) A description of available data on soils present at the site;
(4) A description of BMPs to be used to control pollutants in storm water discharges during
construction
(5) A description of the general timing (or sequence) in relation to the construction schedule
when each BMP is to be implemented;
(6) An estimate of the pre-development and post-construction runoff coefficients of the site;
(7) The name(s) of the receiving water(s);
(8) Delineation of SWPPP implementation responsibilities for each site owner or operator;
(9) Any existing data that describe the storm water runoff characteristics at the site (such as data
that may be collected during a site assessment), and
Updating the SWPPP
The operator would be required to amend the SWPPP and corresponding erosion and sediment
control BMPs whenever:
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(1) There is a change in design, construction, or maintenance that is expected to have a
significant effect on the discharge of pollutants; or
(2) Inspections or investigations by site operators, local, State, Tribal or Federal officials
indicate that any BMPs described hi the SWPPP are ineffective in eliminating or ;
significantly mhiimizing pollutant discharges. •]
Site Log Book/Certification ;
The operator would be required to maintain a record of site activities in a site log book, as part of
the SWPPP. The site log book shall be maintained as follows: '.
(1) A copy of the site log book would be required to be maintained on site and be made
available to the permitting authority upon request. EPA recommends that the operator make
a copy of the site log book available to the public upon request within a reasonable period;
(2) In the site log book, the operator would be required to certify, prior to the commencement of
construction activities, that the SWPPP meets all Federal, State and local erosion arid
sediment control requirements and is available to the permitting authority;
(3) The operator would be required to have a qualified professional conduct an assessment of
the site prior to groundbreaking and certify that the appropriate BMPs and erosion and
sediment controls described in the SWPPP have been adequately designed, sized and
installed to ensure overall preparedness of the site for initiation of groundbreaking activities.
The operator would be required to record the date of initial groundbreaking in the site log
book. The operator would be required to certify that the site inspections, soil stabilization
activities, and maintenance activities required by the proposed rule have been satisfied
within 48 hours of actually meeting .such requirements;
i
(4) The operator would be required to post at the site, in a publicly-accessible location,:a
summary of the site inspection activities on a monthly basis. EPA recommends that the
operator provide contact information for obtaining a copy of the SWPPP and a copy of the
site inspection log book; ;
Site Inspections
The operator or designated agent of the operator (such as a consultant, subcontractor, or ^hird-
party inspection firm) would be required to conduct regular inspections of the site and record the
results of such inspection in the site log book. The specific activities that would require j
inspection and certification are: ' ;
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(1) After initial groundbreaking, operators would be required to conduct site inspections at least
every 14 calendar days and within 24 hours of the end of a storm event of 0.5 inches or
greater. These inspections would be required to be conducted by a qualified professional.'
During each inspection, the operator or designated agent would be required to record the
following information:
(i) On a site map, indicate the extent of all disturbed site areas and drainage
pathways. Indicate site areas that are expected to undergo initial disturbance or
significant site work within the next 14-day period;
(ii) Indicate on a site map all areas of the site that have undergone temporary or
permanent stabilization;
(iii) Indicate all disturbed site areas that have not undergone active site work during
the previous 14-day period; .
(iv) Inspect all sediment control practices and note the approximate degree of
sediment accumulation as a percentage of the sediment storage volume (for
example 10 percent, 20 percent, 50 percent, etc.). Record all sediment control
practices in the site log book that have sediment accumulation of 50 percent or
more; and
(v) Inspect all erosion and sediment control BMPs and record all maintenance
requirements such as verifying the integrity of barrier or diversion systems
(earthen berms or silt fencing) and containment systems (sediment basins and
sediment traps). Identify any evidence of rill or gully erosion occurring on slopes
and any loss of stabilizing vegetation or seedrng/mulching. Document in the site
log book any excessive deposition of sediment or ponding water along barrier or
diversion systems. Record the depth of sediment within containment structures,
any erosion near outlet and overflow structures, and verify the ability of rock
filters around perforated riser pipes to pass water.
(2) Prior to filing of the Notice of Termination or the end of permit term, a final site erosion and
sediment, control inspection would be required to be conducted by the operator or designated
agent. The inspector would be required to certify that the site has undergone final
stabilization using either vegetative or structural stabilization methods and that all
temporary erosion and sediment controls (such as silt fencing) not needed for long-term
erosion control have been removed.
Stabilization
The operator would be required to initiate stabilization measures as soon as practicable in
portions of the site where construction activities have temporarily or permanently ceased, but in
no case more than 14 days after the construction activity in that portion of the site has
temporarily or permanently ceased. This provision would not apply in the following instances:
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(1) Where the initiation of stabilization measures by the 14th day after construction activity
temporarily or permanently ceased is precluded by snow cover or frozen ground conditions,
the operator shall initiate stabilization measures as soon as practicable;
(2) Where construction activity on a portion of the site is temporarily ceased, and earth- ;
disturbing activities will be resumed within 21 days, temporary stabilization measures need
not be initiated on that portion of the site.
(3) In arid areas (areas with an average annual rainfall of 0 to 10 inches), semi-arid areas (areas
with an average annual rainfall of 10 to 20 inches), and areas experiencing droughts where
the initiation of stabilization measures by the 14th day after construction activity has
temporarily or permanently ceased is precluded by seasonably arid conditions, the operator
shall initiate stabilization measures as soon as practicable.
Maintenance |
The operator would be required to remove accumulated sediment from sediment traps and ponds
identified as having sediment accumulation greater than 50 percent to restore the original design
capacity,
6.3.3 Option 3 - No Regulation
EPA also considered an option that would not establish effluent guidelines requirements for this
industry.
6.4 REFERENCES ,
USD A. 2000.1997 National Resources Inventory. U.S. Department of Agriculture, Natural
Resources Conservation Service. Washington, DC. (
http://www.nrcs .usda. gov/technical/NRI/ ,
USEPA. 1983. Final Report of the Nationwide Urban Runoff Program. U.S. Environmental
Protection Agency. Washington DC. ,
USEPA. 1998. Reissuance ofNPDES General Permits for Storm Water Discharges from
Construction Activities. ("Construction General Permit.") Federal Register, Vo. 63, No. 31,
p. 7858. February 17, 1998. Washington, DC.
http://cfpub.epa.gov/npdes/stormwater/cpermit.cftn7program id=6
USEPA. 1999. Economic Analysis of the Final Phase II Storm Water Rule. U.S. Environmental
Protection Agency. Washington, DC. ' •
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USEPA. 2002. Economic Analysis of Proposed Effluent Limitation Guidelines and New Source
Performance Standards for the Construction and Development Category; May 2002. EPA
821-R-02-008. http://www.epa.gov/waterscience/guide/construction/
USEPA. 2002a. Environmental Assessment for Proposed Effluent Limitation Guidelines and
New Source Performance Standards for the Construction and Development Category; May
2002. EPA 821-R-02-009. http://www.epa.gov/waterscience/guide/construction/
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SECTION 7: APPROACH TO ESTIMATING COSTS
7.1 OVERVIEW
This section describes EPA's methodology for estimating compliance costs associated with
implementing the regulatory options proposed for the construction and land development effluent
limitation guidelines (ELG). EPA estimated three distinct cost categories: (1) erosion and
sediment control (ESC) costs, including design, installation, operation, and maintenance;
(2) administrative costs to permittees for activities such as site inspections and certification
activities; and (3) administrative costs to permit authorities to incorporate the effluent guidelines
requirements into general permits. Costs contained in categories (1) and (2) are expected to be
borne directly by the construction and development industry.
Costs were evaluated individually for 24 site size class and land use types. EPA developed a
series of model sites for each land use/site size class and estimated costs of proposed options for
each of these model sites. Using estimates of the population of new construction acreage
developed using data from the USDA's National Resources Inventory (NRI), the U.S. Census
Bureau, EPA's NPDES Storm Water Phase II rulemaking, and other national data sources
(described in Section 3 of this document), EPA summed the model site costs to the national
level. A description of this methodology is presented in the Economic Analysis document
(USEPA, 2002).
The total costs of'the proposed rule options are presented in Table 7-1.
Table 7-1. Total Costs of Proposed Rule Options
Option
1 - Inspection and Certification sites ^ 1 acre
2 - Codify EPA Construction General Permit (CGP)
with Inspection and Certification sites £5 acres
3 - No Regulation
Annual Cost (millions 2000 dollars)
126
502
0
7.2 METHODS FOR ESTIMATING EROSION AND SEDIMENT CONTROL COSTS
7.2.1 OVERVIEW
EPA used four land use types to account for variations in construction operations and associated
ESCs employed for various development types. For each land use type, EPA evaluated six site
size classes to account for economies of scale that might occur with certain best management
practice (BMP) design and installation costs (some BMPs are employed only if the site size is
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greater than a threshold value). EPA also considered regional cost adjustments due to variations
in labor, supply, and material costs (see Table 7-2). EPA used an industry standard reference to
establish appropriate adjustment factors for regional compliance costs (R.S. Means, 2000).
The costing analysis started by allocating the estimated annual construction acreage and number
of model sites developed in Section 4 (see Table 4-21) for one of 19 EPA-developed ecoregions
shown in Figure 7-1 (see the Environmental Assessment supporting document (EPA, 2002a) for
a complete description of the EPA ecoregions). Matrices of standard BMP quantities for the
technology-based option (Option 2) were developed for the various model site sizes using the
NPDES Phase II economic analysis (USEPA, 1999) and the Agency's engineering judgement.
By multiplying the two matrices, the total quantity of BMPs for all of the model sites was
determined. EPA estimated the unit costs of each BMP element using R.S. Means (2000), and
data from "The Economics of Stormwater Treatment: An Update" from the Center for Watershed
Protection's (CWP's) book entitled The Practice of Watershed Protection (Schueler, 2000).
Regional costs were adjusted using cost adjustment factors from R.S. Means (2000), and data
were summed across the different site size categories to determine engineering costs at the
national level. Additional costs for factors such as. design and contingencies (described in the
Economic Analysis) were added to these national costs to arrive at the national cost figures
presented in Table 7-1. All costs presented are incremental over current costs to the industry
from existing Federal and State requirements.
EPA used a similar approach to estimate administrative costs to permittees for conducting the
site inspection and certification provisions contained in Options 1 and 2. EPA estimated the
number of site inspections needed and the hours required for conducting site inspections and
certifications for each of the model site sizes. By multiplying these hour estimates by a
professional labor rate, EPA was able to estimate the total administrative costs to permittees.
Similarly, EPA estimated the administrative costs to permitting authorities to revise general
permits to incorporate the effluent guideline requirements by multiplying the estimated hours per
entity by the number of entities to arrive at the national costs.
June 2002
7-2
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Development Document for Construction and Development Proposed Effluent Guidelines
Figure 7-1. EPA Ecoregions
Source: Composited from Omernik, 1987.
June 2002
7-3
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Development Document for Construction and Development Proposed Effluent Guidelines
Table 7-2. Regional Compliance Cost Adjustment Factors
EPA
Hydrologic
Region
1
2
3
4
5
6
7
8
9
10 •
11
12
13 .
14
15
16
17
18
19
Regional Compliance Cost
' Adjustment Factor
! 0.855
0.984
0.900
0.782
i 0.857
0.858
0.870
' 1.032
0.877
0.996
0.810
0.854
0.936
0.908
1.094
1.129
1.052
1.046
1.052
Source: EPA hydrologic regions are composited
from Omernik, 1987. Regional compliance cost
adjustment factors are computed based on city
data from R.S. Means, 2000.
7.2.2
EROSION AND SEDIMENT CONTROL COSTS
In this analysis, EPA has built upon a number of previous assessments of ESC practices,
including the Economic Analysis of the Final Phase II Storm Water Rule (USEPA, 1999). EPA
estimated types and quantities of ESC BMPs that are commonly employed under baseline
conditions during construction activities to mitigate impacts from construction site runoff for 24
land use/site size class models. In addition, in its analysis EPA estimated that requirements
June 2002
7-4,
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Development Document for Construction and Development Proposed Effluent Guidelines •
contained in existing State construction general permit requirements (or, in the non authorized
states, the region-specific EPA construction general permits (CGPs) would be fully implemented.
Although Phase II is not fully implemented at this tune, the requirements will be implemented by
the time final action is taken on these proposed effluent guidelines. Furthermore, as proposed
Option 2 (the only option for which EPA is establishing technology-based requirements)
addressed'only sites with 5 or more acres of disturbed land, the timing of Phase II
implementation is not an issue. .
EPA took a model site approach to estimating the baseline ESC usage and quantities of
materials, as well as design costs and operation and maintenance (O&M) costs that are expected
to be applicable given a range of physical conditions (1 to 7 percent land slopes and different soil
types). Table 7-3 lists the construction site BMPs included in the baseline analysis for various
site sizes. To establish baseline BMP usage, EPA started with the model site estimates generated
during the Phase II rulemaking, scaling up the BMP quantities to sites larger than 5 acres, and
adding sediment basins for larger sites. In the final costing analysis of this option, costs for
BMPs for sites less than 5 acres were eliminated, consistent with the proposed regulatory
requirements for Option 2.
Table 7-3. Construction Site ESC BMP Descriptions and Site Thresholds
ESC BMP Description
Silt Fence, Diversion Dike, Construction Entrances, Stone Check Dams
Mulch
Sediment Traps
Polyacrylamide (PAM)
Sediment Basins
BMP Installation and SWPPP Certifications
Site Inspections - .
Applicable Site Sizes for
ESC BMP Quantity Estimates
> 1 acre
> 1 acre
> 1 acre and < 10 acres
> 1 acres
£ 10 acres
^ 1 acre
£' 1 acres
To determine costs of the regulatory options, EPA first evaluated a variety of State construction
general permits and erosion and sediment control regulations and found that many States have
requirements similar to those contained in the EPA construction general permit, which is the
June 2002
7-5
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Development Document for Construction and Development Proposed Effluent Guidelines |
basis for the requirements contained in Option 2 (see Table 7-4)l. In evaluating existing State
programs, EPA specifically examined the major provisions contained in Option 2, namely
sediment basins designed to provide 3,600 cubic feet per acre of storage; requirements fot
stabilization of exposed soil areas within 14 days of reaching final grade; and site inspections at
least every 14 days. In addition, EPA evaluated whether the annual precipitation in each State is
less than 20 niches, since the soil stabilization requirements are linked to this condition. In the
final analysis of national costs, EPA adjusted the estimates of the national costs for the effluent
guidelines to account for States with programs equivalent to EPA's proposed options. Table 7-5
summarizes the percentage of national costs eliminated due to equivalent State programs. This is
only applicable to Option 2, as EPA has not determined that a significant number of States have
requirements equivalent to Option 1.
It is expected that on some construction sites there will be some portion of land with steeper
slopes and more erosive soils, which will require more intensive management if built upon than
is assumed by EPA's model. Also, a State with less than 20 inches of annual rainfall was
considered to be equivalent to a State that has the 14-day cover requirement when assessing
overall equivalence. Local regulations may require use of ESCs that are more stringent than the
Phase I and II requirements. However, EPA expects that the BMPs selected to develop its model
sites are representative of baseline conditions for the majority of construction activity across the
nation. . . ;
1 Although EPA attempted to obtain comprehensive information, the Agency was not
able to verify the presence of the specific components in Table 7-4 for all States. As a result, the
absence of an entry does not necessarily mean that the State does not currently have an
equivalent requirement.
June 2002
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Development Document for Construction and Development Proposed Effluent Guidelines
Table 7-4. Components of Existing State Erosion and Sediment Control Requirements3
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
District of
Columbia
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Minimum of 3,600
Cubic Feet per Acre
Sediment Basin
Requirement
Yes
Yes
Yes
Yes
Yes
Yes
Yes
, Inspections
Required at Least
Every 14 Days
Yes
Yes
Yes
Yes
14- Day or Less
Stabilization
Requirement
Yes
Yes
Yes
, Yes
Yes
Yes
States with Less than
20 Inches of
Precipitation Per
Year
Yes '
Yes
Yes
Yes
Yes
June 2002
7-7
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Development Document for Construction and Development Proposed Effluent Guidelines
State
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Minimum of 3,600
Cubic Feet per Acre
Sediment Basin
Requirement
Yes
Yes
•
Yes
Yes
Yes
Yes
Yes
•Yes
Yes
Yes
Yes
Inspections
Required at Least
Every 14 Days
Yes
Yes
Yes
1
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
14- Day or Less
Stabilization
Requirement
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
States with Less than
20 Inches of
Precipitation Per
Year
Yes
Yes I
Yes
Yes
i
Yes !
Yes ;
i
1
June 2002
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Development Document for Construction and Development Proposed Effluent Guidelines
State
Wyoming
Minimum of 3,600 .
Cubic Feet per Acre
Sediment Basin
Requirement
Inspections
Required at Least
Every 14 Days
Yes
14- Day or Less
Stabilization
Requirement
States with Less than
20 Inches of
Precipitation Per
Year
Yes
•a. Information is accurate as of May 2002
Table 7-5. State Acreage Equivalent to Proposed Option 2
Option 2
Equivalent State
Acreage for
• Sites >5 acres
755,500
Percent of Annual
(>5 acre) Developed
Acreage Equivalent
41
Once EPA estimated the quantities of ESC BMPs for the model sites, the total baseline cost of
BMP ^installation was calculated from unit costs provided by R.S. Means (2000) and cost curves
from "The Economics of Stormwater Treatment: An Update" (Schueler, 2000). R.S. Means
provides national average unit costs that include materials, installation, and labor. Typically,
users of R.S. Means adjust the national unit costs up or down to obtain their local estimates based
on city-specific adjustment factors provided by R.S. Means. As described previously, EPA
developed and used the regional adjustment factors in Table 7-2 to customize unit costs on an
ecoregion basis, not on a city basis. To compute region-specific unit costs from the national
average value, city-specific adjustment factors provided by R.S. Means were converted into
ecoregion values. First, State-average adjustment factors were estimated based on the values for
cities they contained. Then ecoregion values were computed based on area-weighting for those
states that fell within each ecoregion.
Although R.S. Means is expected to accurately estimate the as-built cost for a particular element,
in certain cases it might underestimate the cost that a developer or ultimate property owner might
need to pay a contractor to construct a particular element. This is due to additional site-specific
cost factors that a contractor may build into a bid package, such as contingencies, allowances for
change orders, additional time and labor for unseen delays due to weather, unanticipated
problems with soils^ etc. However, for the majority of projects, R.S. Means is expected to
provide accurate cost information. In addition, EPA adjusted for contingency costs in its
analysis of economic impacts to the industry (see the Economic Analysis document for a
description of this methodology).
In calculating the total costs for erosion and sediment control activities, EPA added estimated
design, operation, and maintenance costs. Table 7-6 shows design and O&M costs as a fraction
of the capital cost of ESC BMPs. These cost ratios were obtained from published sources such
June 2002
7-9
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Development Document for Construction and Development Proposed Effluent Guidelines
as the CWP report and from the Agency's engineering judgement.
In evaluating the proposed rule options, EPA used the model site approach to first determine the
baseline compliance costs, then to modify BMP sizing and BMP quantities to assess the
incremental costs of regulatory options of the proposed rule. The resulting suite of BMPs
evaluated by EPA in establishing costs of the proposed rule are listed in Table 7-7, along with
their unit costs. Appendix B contains additional tables indicating EPA's estimates of the
standard quantity needed for each BMP listed in Table 7-7, for each land use type and site size.
In addition, Appendix B indicates, for key BMPs, the number of equal size BMPs of a single
type that EPA estimates will be needed to serve a single site (i.e., a single 200-acre site will be
served by four equal-size sediment basins, each of which manages 50 acres).
Table 7-6. Construction ESC BMP Design and Operation and Maintenance Costs
as a Percentage of Capital Costs
, Costed Items
Silt Fence
Diversion Dike
Mulch
Construction Entrance
Stone Check Dam
Sediment Trap
Sediment Basin
Polyacrylamide (PAM)
Effective Life in
Years
1
1
1
1
1
1
1
1
Design Costs as
Percent of
Construction Cost
6%
6%
6%
6%
6%
6%
6%
: 6%
Estimated O&M as Percent of
Original Installation Costs
100% :
10%
2% ;
5%
5% |
20% i
25% '
0
June 2002
7-10
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Development Document for Construction and Development Proposed Effluent Guidelines
Table 7-7. Evaluated Construction Site BMPs that Augment the Suite of Baseline BMPs
BMP
Description
Costing Rationale
Erosion and Sediment Controls
Sediment Basins
for Sites
acres
Standardization to 3,600 cubic feet of storage per watershed acre. Cost based on equation
for installing permanent dry detention pond, computed from the equation:
[8.16 x (volume required, cu. ft./number of ponds per site size)0'78] (Schueler, 2000).
Mulch
Mulching of any denuded surface would be required within 14 days of reaching final grade,
resulting in more frequent mulching of a portion of the site acreage. Cost of mulching is
estimated to be $0.23 per square yard for materials/installation (R.S. Means). For sites
larger than 1 acre, mulching is based on the total site acreage less the area where structures
are being built (estimated as the site impervious coverage). The maximum coverage for
single-family and multifamily residential development is 50% of the total site area,
assuming the remaining acreage is maintained as open space and/or permanent
vegetation/cover is installed.
Polyacrylamide
(PAM)
EPA estimates that a single application of PAM would be used as a temporary stabilization
method until final cover can be installed. PAM was estimated to be appropriate for only
20% of construction sites due to physical constraints. PAM is costed at $200 per acre
treated based on a survey of commercial vendors and the assumption that its application is
similar to that of herbicide for soil treatment ($0.04 per square yard based on spraying from
truck) (R.S. Means). The acreage treated is equal to the site size times the ultimate
impervious area, to a maximum of 50% of.the site size.
Site Administration BMPs
Site Certifications
For each site, certification activities include certification of storm water pollution
prevention plan (SWPPP) completion, certification of BMP installations, and certification
of final stabilization prior to filing of the notice of termination (NOT). Certification adds an
estimated cost of approximately $ 11 per acre for Options 1 and 2.
Site Inspections
For each 10-acre unit in the total site, incremental inspection activities over baseline are: (a)
post-BMP installation; (b) once during building; and (c) at end of construction (prior to
filing of the NOT). Inspection adds an estimated cost of approximately $45 per acre for
Options 1 and 2.
Table 7-8 indicates the relative change in quantities of BMPs associated with Options 1 and 2.
Standard quantities of BMPs outlined in Table 7-3 were increased or decreased according to
multiplication factors in Table 7-8 to reflect changes expected due to each option. For example,
in the case of mulch, EPA estimates that under Option 2, there will be a net increase in the use of
mulch by 20 percent over baseline levels, in part to help meet the requirements for 14-day
coverage of denuded areas. In the case of PAM, EPA anticipates that PAM will be applied to 20
percent of the denuded acreage, as it is an inexpensive and effective means to improve erosion
control.
June 2002
7-11
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Development Document for Construction and Development Proposed Effluent Guidelines . . '
Table 7-8. BMP Quantity Adjustment Factors for Baseline and Proposed Options
BMP Type
Silt Fence
Runoff Diversion
Mulch
Construction
Stone Check Dam
Sediment Trap
Sediment Pond
E&S Certification
E&S Inspection
PAM
Baseline
Construction
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
O.Q
0.0
Optionl Inspection/
Certification
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
Option 2 Inspection/
Certification with
Codification of CGP
1.0 ;
1.0
1.2 ;
1.0 '
1.0 ;
1.0
1.1 '
1.1 ;
1.0
0.2
1
Using the information in Table 7-8, EPA estimated baseline costs as well as the costs for Options
1 and 2. By subtracting the baseline costs from the cost of each option, EPA was able to estimate
the incremental costs of the proposed options. Table 7-9 indicates the estimated national costs
over baseline of the proposed rule options. Values include design, maintenance, and
opportunity/interest costs. States that are considered to be equivalent to EPA's proposed, options
are removed from the total national cost estimate increases. The proposed rule is expected to
increase compliance costs for ESCs under Option 1 by $ 126 million, and by $502 million for .
Option 2 (year 2000 dollars). Option 3 is not expected to have any incremental costs.
June 2002
7-12
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Development Document for Construction and Development Proposed Effluent Guidelines
Table 7-9. National Cost Estimates for Proposed Rule Options
Sector
Single-family Residential
Multifamily Residential
Commercial
Industrial
Total
Option 1 Total Cost
(millions, 1997 dollars)
25.7
12.7
83.8
4.0
126.2
Option 2 Total Cost
(millions, 1997 dollars)
129.7
63.4
296.2
11.8
501.1
7.3 METHODS FOR ESTIMATING ADMINISTRATIVE COSTS
7.3.1 OVERVIEW
The analysis of administrative costs focused on the costs to permit authorities to incorporate the
effluent guidelines requirements into general permits. Administrative costs are expected to be
borne by both EPA and States (or surrogate agencies such as conservation districts). EPA's
assessment is conservative in that it assumes that all States will have to incorporate the effluent
guideline requirements into their permits. However, EPA estimates that approximately 41
percent of developed acreage is under state programs that are equivalent to the proposed
requirements contained in Option 2 and, therefore, will not have to modify their permits to
incorporate these requirements.
7.3.2
ADMINISTRATIVE COSTS TO PERMITTEES
When considering the administrative costs to permittees for implementation of the proposed
options, EPA estimated the number of CGPs it expects to be issued each year. Table 7-10
indicates the number of construction sites under permit EPA estimates are associated with
current development rates, categorized by Option. In its analysis, EPA estimated that
construction sites not affected by effluent guidelines (those smaller than 5 acres in Option 2, and
those smaller than 1 acre in Option 1) would not incur administrative costs.
Annual administrative costs are expected to be borne by construction firms as a result of site
certification and inspection requirements (See Table 7-7). Under Options 1 and 2, site operators
will be required to certify that the Storm Water Pollution Prevention Plan (SWPPP) has been
completed, that BMPs are installed according to the SWPPP, that periodic inspections have been
completed, and that the site has been stabilized prior to filing of the notice of termination (NOT).
EPA estimated that it will take 16 hours per 10 acres developed to meet the inspection
requirement. (For construction sites smaller than 10 acres only 16 hours of inspection is
June 2002
7-13
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Development Document for Construction and Development Proposed Effluent Guidelines
requked.) EPA used the estimates of construction projects by size presented hi Table 4-21 to
estimate the total hours requked to perform administrative activities.
EPA estimated the total national costs associated with site certifications to be $27,712,000 per
year under Option 1 and $16,727,000 per year under Option 2 (1997 dollars). Based on a review
of States with greater than 50,000 acres per year development, EPA estimates that 34 percent of
acres developed are within States with 14-day inspection requkements that are similar to those
proposed under Options 1 and 2. As a result, EPA adjusted downward its estimate of national
site inspection costs to reflect equivalent inspection programs. The total resulting estimates for
site inspection under Options 1 and 2 are $73,161,000 and $44,160,000 per year, respectively.
EPA's estimate of the total annual administrative cost for certification and inspection for Option
1 and 2 are $100,873,000 and $60,887,000, respectively. The total annual administrative costs
are lower for Option 2 because sites of less than 5 acres are not regulated. EPA adjusted these
cost estimates upward to reflect opportunity costs, resulting in overall administrative costs to
permittees of $118,141,000 for Option 1 and $71,290,000 for Option 2. An explanation of this
methodology is presented in the Economic Analysis supporting documentation. :
7.3.3
ADMINISTRATIVE COSTS FOR GENERAL PERMIT REVISIONS
EPA estimated the total one-time costs for permit authorities to incorporate the erosion and
sediment control effluent guidelines requkements into thek general permits. EPA's estimates of
full tune equivalents (FTEs) and costs for each agency to incorporate effluent guidelines
requirements are indicated in Table 7-10. To determine costs of incorporating the effluent
guidelines requkements into existing State CGPs, EPA estimated that each State will requke 200
hours to evaluate and then modify general permits to incorporate new requirements. All 50
States were estimated to encounter administrative costs, even though many States already have
general permits that meet some of the proposed requkements. When dividing costs between
Federal and State entities, EPA's estimated costs will be allocated based on the percentage of
States currently authorized to manage the NPDES program (i.e., 44 of 50, or 88 percent).
Table 7-10. One-Time Hours and Costs to Incorporate Erosion and Sediment Control
Effluent Guidelines Requirements into General Permits (1997 Dollars) !
Program Element
Revise General Permits (hours)
Revise General Permits (dollars)
Federal
1,200
$31,000
State
8,800
$229,000
June 2002
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Development Document for Construction and Development Proposed Effluent Guidelines '
7.4 REFERENCES
Schueler, Thomas R... 2000. "The Economics of Stoimwater Treatment: an Update". Article
No.. 68 in the Practice of Watershed Protection. Center for Watershed Protection, Ellicott
City, MD. http://www.stonnwatercenter.net
Omernik, James M. 1987. Ecoregions of the Conterminous United States. Annal of the
Association of American Qeorgraphers. 77(1): 118-125.
R.S. Means. 2000. Site Work & Landscape Cost Data, 19th Edition. R..S. Means Co., Kingston
MA. .
USEPA. 1999. Economic Analysis of the Final Phase li Storm Water Rule. U.S. Environmental
Protection Agency. Washington, DC.
USEPA. 2002. Economic Analysis of Proposed Effluent Limitation Guidelines and New Source
Performance Standards for the Construction and Development Category; May 2002. EPA
821-R-02-008. http://www.epa.gov/waterscience/guide/construction/
USEPA. 2002a. Environmental Assessment for Proposed Effluent Limitation Guidelines and
New Source Performance Standards for the Construction and Development Category; May
2002. EPA 821-R-02-009. http://www.epa.gov/waterscience/guide/construction/
June 2002
7-1.5
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Development Document for Construction and Development Proposed Effluent Guidelines
APPENDIX A:
STATE REGULATIONS ON THE CONTROL OF CONSTRUCTION
STORM WATER
June 2002
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-------
-------
Development Document for Construction and Development Proposed Effluent Guidelines
APPENDIX B:
SUPPORTING COST DATA
June 2002
-------
-------
Development Document for Construction and Development Proposed Effluent Guidelines __^
APPENDIX B: SUPPORTING COST DATA
OVERVIEW
EPA estimated a reference or standard quantity for each costed best management practice (BMP)
that could be applied to construction erosion and sediment controls (ESCs) (e.g., 621 feet of silt
fence for a 3-acre single-family residential construction site). These reference quantities were set
to serve a range of site conditions and slopes consistent with the requirements of the proposed
rule. Reference quantities were not varied between ecoregions but were varied in response to
alternative levels of management (i.e., regulatory options explored by EPA) as shown in Table
B-l. Note that only where values in Table B-l differ between options and baseline values is there
expected to be a change in the cost for site ESCs.
Reference quantities of various ESCs (or construction controls) are listed in Tables B-2 through
B-10, along with unit costing and the assumptions used in EPA's compliance cost assessment.
Note that for some controls, reference quantities are given in terms of the number of units that
will be constructed (i.e., the number of construction entrances anticipated for a certain size. site).
In addition, where unit costs are nonlinear (i.e., the unit cost varies with the size of the unit), both
a design quantity and a number of units per site size class are required to estimate ESC
compliance costs. An example of this is sediment basins, where the total volume (the site size in
acres times 3,600 cubic feet per acre) is apportioned into a number of installations (i.e., a 70-acre
site is estimated to have 2 installations). This process helps ensure that any economies of scale in
the calculation of compliance costs are reasonable.
National BMP costs were determined using the following three equations that relate site size
class/land use type models to ESC capital, design, and operation and maintenance costs. Note
that Table B-l 1 contains the regional adjustment factors that customize cost estimates for the
19 ecoregions defined by EPA to make its analysis more representative of actual conditions.
Figure B-l presents a flowchart summarizing the overall costing methodology.
June 2002
B-l
-------
Development Document for Construction and Development Proposed Effluent Guidelines
= RAF*J\\ LM*S*Ni*a\%-
•^"" I . I A/ .•
1=1
N,
TRCC - Total Regional Capital (Installation) Cost for a site size class/land use model '•
Qi - Quantity of elements required per installation
Nj5* Number of elements required for a single site size class/land use .
S = Estimated number of sites in the site size class/land use
a - Multiplier for converting quantity to national average cost in 2000 dollars
b = Exponent for converting quantity to national average cost in '2000 dollars
RAF = Regional adjustment factor for converting national average costs to region-specific costs
LM - Level of management; values between 0 and 2 that indicate the degree of application of the element. A value
of 1 indicates the full application of an element based on the reference condition
17
TRDC = RAF *2>^ *| LM *s * NI *a\ ^T
TRDC = Total Regional Design Costs
DF{= Design factor, a multiplier which represents the design cost as a percent of capital costs
Qj = Quantity of elements required per installation
Nj - Number of elements required for a single site size class/land use
S- Estimated number of sites in the site size class/land use ;
a - Multiplier for converting quantity to national average cost in 2000 dollars
b = Exponent for converting quantity to national average cost in 2000 dollars
RAF = Regional adjustment factor for converting national average costs to region-specific costs
LM - Level of management; values between 0 and 2 that indicate the degree of application of the element. A value
of 1 indicates the full application of an element based on the reference condition ;
17
LM = Level of management; values between 0 and 2 that indicate the degree of application of the element. A value
of 1 indicates the full application of an element based on the reference condition.
TROMC = Total Regional Operation and Maintenance Costs ;
OMj= Operation and Maintenance factor, a multiplier which represents the annual operation and maintenance cost
which ensure proper operation of the element :
Q. = Quantity of elements required per installation
Nj = Number of elements required for a single site size class/land use
S m Estimated number of sites in the site size class/land use
a - Multiplier for converting quantity to national average cost in 2000 dollars :
b " Exponent for converting quantity to national average cost in 2000 dollars
RAF = Regional adjustment factor for converting national average costs to region-specific costs
LM = Level of management; values between 0 and 2 that indicate the degree of application of the element. A value
of 1 indicates the full application of an element based on the reference condition.
June 2002
B-2
-------
Development Document for Construction and Development Proposed Effluent Guidelines
able B-l. BMP Quantity Adjustment Factors for Baseline and the Pronosed Onlions
Costed Items
Silt Fence
Runoff Diversion
Construction Phasing
Mulch
Seed and Mulch
Construction Entrance
Stone Check Dam
Sediment Trap
Sediment Pond
E&S Certification
E&S Inspection
Polyacrylamide (PAM)
Alum Treatment
Monitoring of Effluent Quality
Baseline
Construction
1.0
1.0
0.0
1.0
0.0
1.0
1.0
1.0
1.0
0.0
0.0
0.0
0.0
0.0
Option 1 — Inspection/
Certification
1.0
1.0
0.0
1.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
0.0
0.0
Option 2 — Inspection/
Certification with
Codification of CGP
1.0
1.0
0.0
1.2
0.0
1.0
1.0
1.0
1.1
1.1
1.0
0.2
0.0
0.0
June 2002
B-3
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Development Document for Construction and Development Proposed Effluent Guidelines
Table B-2. Quantities of Erosion and Sediment Control Items For
Assessing Compliance Costs for the Construction Industry
Site
size
Acres
1
3
7.5
25
70
200
Feet of Silt Fence
Single-
family
-
621
1,553
5,175
14,490
41,400
Multi-
family
-
722
1,143
3,129
5,238
8,853
Com-
mercial
-
361
600
2,087
3,492
5,902
Indus- '
trial
-
361
600
2,087
3,492
5,902
Feet of Diversion Dike
Single-
family
-
621
1,553
5,175
14,490
41,400
Multi-
family
-
722
1,143
3,129
5,238
8,853
Com-
mercial
-
361
600
2,087
3,492
5,902
Indus-
trial
-
361
600
2,087
3,492
5,902
Both silt fencing and diversion dike lengths were based on 207 feet per acre on the site.
Costs for new installation of silt fence are based on $0.92/ft length, excluding profit and overhead (R.S.
Means, 2000). '
Costs for new installation of diversion ditch are based on $0.55/ft length installation, excluding profit and
overhead (R.S. Means, 2000).
Tab!
le B-3. Quantities of Erosion and Sediment Control Items
Assessing Compliance Costs for the Construction Industry
Site Size
Acres
1
3
7.5
-25
70
200
Mulched Acreage To Control Erosion
Single-family
0.0
0.8
1.9
6.3
17.5
50.6
Multifamily
6.0
6.8
1.9
6.3
17.5
50-0
Commercial
0.0
0.8
1.9
6.3
17.5
50.0
Industrial
0.0
0.8
1.9
6.3
17.5
50.0
For
For sites larger man lacre, muicnmg is nmirea to tne sue acreage times nan me peitcmagc ui uiuuuue
impervious area as a temporary means to stabilize denuded surfaces. The maximum coverage is set to 25%
of the total site acreage. Cost to mulch is set to $0.20 per square yard for materials/installation without
overhead and profit (R.S. Means, 2000).
June 2002
B-4
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Development Document for Construction and Development Proposed Effluent Guidelines
Table B-4. Quantities of Erosion and Sediment Control Items For
Assessing Compliance Costs for the Construction Industry
Site Size
Acres
1
3
7.5
-25
70
200
Acres Treated with PAM
Single-family
0.00
0.84
2.10
7.00
•19.60
56.00
Multifamily
0.00
1.32
3.29
10.96
30.70
87.72
Commercial
0.00
1.50
3.75
12.50
35.00
100.00
Industrial
0.00
1.50
3.75
12.50
35.00
100.00
PAM is costed at $200 per acre per treatment based on a survey of commercial vendors and assuming costs
are similar to herbicide for soil treatment ($0.04 per square yard without profit and overhead based on
spraying from truck). The acreage treated is equal to the site size times the ultimate impervious percentage,
to a maximum of 50% of the site size.
Table B-5. Quantities of Erosion and Sediment Control Items For
Assessing Compliance Costs for the Construction Industry
The Number of Equal Size Units Installed to Provide Required Protection
Site
Size
Acres
1
3
7.5
-25
70
200
Number of Stone Check Dam
Single-
family
0
0
10
35
50
100
Multi-
family
0
0
10
35
50
100
Com-
mercial
0
0
10
35
50
100
Indus-
trial
0
0
10
35
50
100
Number of Sediment Trap
Single-
family
0
1
1
0
0
0
Multi-
family
0
1
1
0
0
0
Com-
mercial
0
1
1
0
0
0
Indus-
trial
0
1
1
0
0
. 0
For stone check dam, assume approximately one unit per 5 acres for sites larger than 5 acres at a cost of
$45.36 per installation, excluding overhead and profit (Phase II Economic Analysis for Phase II Storm
Water Regulations).,
Sediment trap of 3,600 cubic feet per acre served at a cost of $0.22 per cubic foot volume (excludes profit
and overhead).
June 2002
B-5
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Development Document for Construction and Development Proposed Effluent Guidelines
Table B-6. Quantities of Erosion and Sediment Control Items For
Assessing Compliance Costs for the Construction Industry
Site Size
Acres
1
3
7.5
25
70
200
Number of Sediment Basins
Single-family
0
0
1
2
2
4
Multifaniily
o
0
1
2
2
4
Commercial
0
0
1
2
2.
4
Industrial
0
0
1
2
2
4
Sediment pond of 3,600 cubic feet per acre served. Cost in dollars is computed from the equation:
[ 0.76 x 7.47 x (volume required, cubic feet/number of ponds per site size)-78]
The value of 0.76 removes overhead and profit from cost estimate. , '
Table B-7. Quantities of Erosion and Sediment Control Items For
Assessing Compliance Costs for the Construction Industry
Site Size
Acres
1
3
7.5
25
70
200
Number of Construction Entrances
Single-family
0
1
1
1
2
4
Multifaniily
0
1
1
1
2
4
Commercial
0
1
1
1
2
4
Industrial
0
1
1
1
2
4
Costs for construction entrance based on $6.92 per square yard (gravel installed) for a footprint covering
100 square yard, excluding profit and overhead (R.S. Means, 2000).
June 2002
B-6
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Development Document for Construction and Development Proposed Effluent Guidelines
Table B-8. Quantities of Erosion and Sediment Control Items For
Assessing Compliance Costs for the Construction Industry
Administrative BMPs for Erosion and Sediment Control
Management
Site Size
Acres
1
3
7.5
25
70
200
E&S Site Inspection
Single-family
0
1
1
2
7
20
Multifamily
0
1
1
2
7
20-
Commercial
0
1
1
2
7
20
Industrial
0
1
1
.2
7^
20
E&S Site Inspection includes multiple site visits by a certified inspector to verify the proper installation and
operation of ESC BMPs. Values above are the number of half-day site inspections. Costs are based on 16
hours of inspection/documentation time per 10-acre unit of a site, at a rate of $28.44 per hour.
Table B-9. Quantities of Erosion and Sediment Control Items For
Assessing Compliance Costs for the Construction Industry
Administrative BMPs for Erosion and Sediment Control
Management
Site Size
Acres
1
3
!
7.5
25
70
200
E&S Site Certification of Sedimentation Basins
Single-family
0
1
1
1
2
4
Multifamily
0
1
1
1
2
4
Commercial
0
1
1
1
2
4
Industrial
0
1
1
1
2
4
E&S Site Certification includes multiple site visits by a certified inspector to verify the proper installation
of sedimentation basins. Costs based on 2 hours of inspection/documentation by a licensed engineer per 10-
acre unit of a site, at a rate of $56.74 per hour.
June 2002
B-7
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Development Document for Construction and Development Proposed Effluent Guidelines
Table B-10. Quantities of Erosion and Sediment Control Items For
Assessing Compliance Costs for the Construction Industry
Site Size
Acres
' 1
3
7.5
25
70
200
Phasing of Construction
Single-family
0
0
0
2
6
19
Multifamily
0
0
o
1 2
6
19
Commercial
0
0
0
2
6
19
Industrial
0
0
0
2
6
19
For sites larger than 10 acres, the number of remobilizations required is based on a maximum of 10 acres
denuded at any single time to prevent large unstabilized construction sites. Costs are based on $1,000 per
remobilization. ;
June 2002
B-8
-------
Table B-ll. Regional Compliance Cost Adjustment Factors
Region or Ecoregion
1
• 2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Regional Compliance
Cost Adjustment Factors
• 0.85456
0.98351
0.9
0.78103
0.85711
0.85768
0.87
1.03221
0.877
0.99576
6.81034-
0.85357
0.93573
0.9076
1.09438
1.1285
1.05151
1.04609
1.05169
June 2002
B-9
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Development Document for Construction and Development Proposed Effluent Guidelines
June 2002
B40
------- |