WATER POLLUTION CONTROL RESEARCH SERIES
11024—06/70
Combined Sewer Overflow
Abatement Technology
June 1970
U.S. DEPARTMENT OF THE INTERIOR • FEDERAL WATER QUALITY ADMINISTRATION
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HATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the results and progress
in the control and abatement of pollution of our Nation's Waters. They provide
a central source of information on the research, development and demonstration
activities of the Federal Water Quality Administration, Department of the Interior,
through in-house research and grants and contracts with the Federal, State, and
local agencies, research institutions, and industrial organizations.
Triplicate tear-out abstract cards are placed inside the back cover to facilitate
information retrieval. Space is provided on the card for the user's accession
number and for additional key words. The abstracts utilize the WRSIC system.
Water Pollution Control Research Reports will be distributed to requesters as
supplies permit. Requests should be sent to the Project Reports System, Office
of Research and Development, Department of the Interior, Federal Water Quality
Administration, Washington, D. C., 20242.
Previously issued reports on the Storm and Combined Sewer Pollution Control
Program:
WP-20-11 Problems of Combined Sewer Facilities and Overflows, 1967.
WP-20-15 Water Pollution Aspects of Urban Runoff.
WP-20-16 Strainer/Filter Treatment of Combined Sewer Overflows.
WP-20-17 Dissolved Air Flotation Treatment of Combined Sewer Overflows.
WP-20-18 Improved Sealants for Infiltration Control.
WP-20-21 Selected Urban Storm Water Runoff Abstracts.
WP-20-22 Polymers for Sewer Flow Control.
Combined Sewer Separation Using Pressure Sewers.
Crazed Resin Filtration of Combined Sewer Overflows.
Rotary Vibratory Fine Screening of Combined Sewer Overflows.
QBD-4
DAST-4
DAST-5
DAST-6
Storm Water Problems and Control in Sanitary Sewers,
Oakland and Berkeley, California.
DAST-9 Sewer Infiltration Reduction by Zone Pumping.
DAST-13 Design of a Combined Sewer Fluidic Regulator.
DAST-25 Rapid-Flow Filter for Sewer Overflows.
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Combined Sewer Overflow Abatement Technology
A Compilation of Papers Presented
at the Federal Water Quality Administration
"Symposium on Storm and Combined Sewer Overflows"
June 22-23, 1970
Pick Congress Hotel
Chicago, Illinois 60605
for the
FEDERAL WATER QUALITY ADMINISTRATION
DEPARTMENT OF THE INTERIOR
Oune, 1970
For tale by the Superintendent of Documents, U. S. Government Printing Office
Washington. D.C., 20402-Price $2.50
-------
FWQA Review Notice
This report has been reviewed by the Federal
Water Quality Administration and approved for
publication. Approval does not signify that
the contents necessarily reflect the views and
policies of the Federal Water Quality Administration,
nor does mention of trade names or commercial
products constitute endorsement or recommendation
for use.
-------
FORWARD
This compilation of papers entitled "Combined Sewer Overflow Abatement
Technology" has been prepared and made available to you so that you can benefit
from the current demonstration grants and contracts that are being supported
by the FWQA.
During this two day Storm and Combined Sewer Overflow Symposium we will
discuss several demonstration projects. Material from these projects to be
highlighted will include (1) alternatives to storm and combined sewer pollution
in a small urban area; (2) screening and air floatation for solids removal;
(3) underflow deep tunnel system concept; (4) urban erosion and sediment control;
(5) sewer monitoring and remote control; (6) combined sewer overflow regulators;
(7) use of fine mesh screens; and (8) land use and urban runoff pollution.
The concepts and information that this symposium will present, hopefully
will help solve your community's problems or at least stimulate in you some
new ideas as to how you might solve your storm and combined sewer overflow
pollution problems.
Francis T. Mayo
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UNITED STATES
DEPARTMENT OF THE INTERIOR
FEDERAL WATER QUALITY ADMINISTRATION
WASHINGTON, D. C. 20242
OFFICE OF RESEARCH AND DEVELOPMENT
AREA CODE: 703
ASSISTANT COMMISSIONER
Dr. David Stephan 557-7311
PLANNING AND RESOURCES OFFICE
Bruce Fisher 557-7697
Project Coordination, Ferial Bishop 557-7695
DIVISION OF APPLIED SCIENCE & TECHNOLOGY
Allen Cywin, Director 557-7370
Storm & Combined Sewer Pollution Control Branch, William Rosenkranz....557-7369
Industrial Pollution Control Branch, William Lacy 557-7385
Pollution Control Analysis Branch, Ernst Hall 557-7495
Agriculture and Marine Pollution Control Branch, Harold Bernard 557-7388
DIVISION OF PROCESS RESEARCH AND DEVELOPMENT
William Cawley, Director 557-7347
Administrative Office, Roy Simpers 557-7354
Technical Office, Harold Foust 557-7355
Program Office, Dr. Alfred Bacher 557-7351
DIVISION OF WATER QUALITY RESEARCH
William Cawley, Director 557-7347
Administrative Office, Roy Simpers 557-7354
Assistant Director for Engineering, Arnold Joseph 557-7318
Assistant Director for Physical Sciences, Dr. Alphonse Forziati 557-7327
Assistant Director for Biological Sciences, Dr. Frances Allen ....557-7335
OFFICE LOCATION: 1921 Jefferson Davis Highway
Arlington, Virginia 22202
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UNITED STATES
DEPARTMENT OF THE INTERIOR
FEDERAL WATER QUALITY ADMINISTRATION
GREAT LAKES REGION
33 EAST CONGRESS PARKWAY, ROOM 410
CHICAGO, ILLINOIS 60605
AREA CODE: 312
OFFICE OF THE REGIONAL DIRECTOR
Francis T. Mayo, Regional Director 353-5250
Robert J. Schneider, Deputy Regional Director 353-5251
OFFICE OF PUBLIC INFORMATION
Frank M. Corrado, Public Information Officer 353-5800
OFFICE OF ADMINISTRATIVE SERVICES
Ivars P. Antens, Administrative Officer 353-5758
OFFICE OF TECHNICAL PROGRAMS
Carlysle Pemberton, Jr., Director 353-5098
OFFICE OF FACILITIES PROGRAMS
James 0. McDonald, Director 353-5752
OFFICE OF ENFORCEMENT & COOPERATIVE PROGRAMS
Glenn D. Pratt, Acting Director .353-5252
OFFICE OF RESEARCH AND DEVELOPMENT
Clifford Risley, Jr., Director 353-5756
LAKE ERIE BASIN OFFICE
Mr. George Barlow, Director
21929 Lorain Road
Cleveland, Ohio 44126
Area Code: 216 522-4876
UPPER MISSISSIPPI RIVER-
LAKE SUPERIOR BASIN OFFICE
Mr. Dale Bryson, Director
7401 Lyndale Avenue
Minneapolis, Minnesota 55423
Area Code: 612 726-1661
LAKE HURON BASIN OFFICE
Mr. Laurence O'Leary, Director
U. S. Naval Air Station
Grosse He, Michigan 48138
Area Code: 313 676-6500
LAKE MICHIGAN BASIN OFFICE
Mr. Jacob Dumelle, Director
1819 West Pershing Road
Chicago, Illinois 60609
Area Code: 312 353-5638
LAKE ONTARIO BASIN OFFICE
Mr. Lee Townsend, Director
P. 0. Box 4748
4664 Lake Avenue
Rochester, New York 14612
Area Code: 716 621-3140
NATIONAL WATER QUALITY LABORATORY
Dr. Donald I. Mount, Director
6201 Congdon Boulevard
Duluth, Minnesota 55804
Area Code: 218 727-6548
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CONTENTS
SECTION PAGE
1 STORM WATER POLLUTION FROM URBAN LAND ACTIVITY 1
AVCO Economic Systems Corporation
2 ROTARY VIBRATORY FINE SCREENING OF COMBINED SEWER 57
OVERFLOWS
Cornell, Rowland, Hayes and Merryfield
3 ASSESSMENT OF COMBINED SEWER PROBLEMS 107
American Public Works Association
4 THE USE OF SCREENING/DISSOLVED-AIR FLOTATION FOR TREATING 123
COMBINED SEWER OVERFLOWS
Rex Chainbelt, Inc.
5 UNDERFLOW PLAN FOR POLLUTION AND FLOOD CONTROL IN THE 139
CHICAGO METROPOLITAN AREA
City of Chicago
6 SEWER MONITORING AND REMOTE CONTROL 219
City of Detroit
7 STREAM POLLUTION AND ABATEMENT FROM COMBINED SEWER AND 291
OVERFLOW
Burgess and Niple, Limited
8 ORGANIZING FOR SOIL EROSION AND SEDIMENT CONTROL IN OUR 321
NATION'S URBAN AREAS
National Association of Counties
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SECTION I
STORM WATER POLLUTION
FROM
URBAN LAND ACTIVITY
for
Presentation at the
Storm and Combined Sewer Seminar
Federal Water Quality Administration
Great Lakes Region
Chicago, Illinois
June 22-23, 1970
by
Jerry G. Cleveland
Ralph H. Ramsey
Paul R. Walters
AVCO Economic Systems Corporation
Washington, D. C.
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ABSTRACT
An investigation of the pollution concentrations and loads from storm
water runoff in an urban area was conducted in Tulsa, Oklahoma during
the period from October 1968 to September 1969. The scope of the pro-
ject included a field assessment of the storm water pollution by obtaining
samples of the water resulting from precipitation and surface runoff
from selected test areas in the metropolitan area; development of an
analytical procedure for correlation of storm water pollution with selec-
tively defined variables of land uses, environmental conditions, drainage
characteristics, and precipitation; and development of a plan for imple-
menting remedial measures necessary to abate or control sources of
pollution in an urban area.
Storm water runoff samples were collected from 15 "discrete" test areas
in the Tulsa Metropolitan areas. These samples were analyzed in terms
of quality standards for BOD, COD, TOC, organic Kjeldahl nitrogen,
soluble orthophosphate, chloride, pH, solids, total coliform, fecal
coliform, and fecal streptococcus pollutants.
The land usage and environmental conditions of the 15 test areas varied.
The parameter averages that were determined for the test areas ex-
hibited these differences. The range of values for the bacteriological
densities varied from 5, 000 to 400, 000 counts/100 ml for total coliform,
10 to 18,000 counts/100 ml for fecal coliforms, and 700 to 30,000 counts/
100 ml for fecal streptococcus. The average storm water loadings for
other selected pollution parameters ranged from 12 to 48 pounds/acre/
year for BOD, 60 to 470 pounds/acre/year for COD, 0.8 to 3.6 pounds/
acre/year for organic nitrogen, !„ 1 to 80 0 pounds/acre/year for soluble
orthophosphate, and 490 to 5100 pounds/acre/year for total solids.
This investigation was performed for the Storm and Combined Sewer
Pollution Control Branch, Federal Water Quality Administration by
AVCO Economic Systems Corporation under Contract 14-12-187. A
draft copy of the final report has been submitted to FWQA for review
and comment.
REVIEW NOTICE
This report has been reviewed in the Federal
Water Quality Administration and approved
for publication. Approval does not signify
that the contents necessarily reflect the views
and policies of the Federal Water Quality
Administration.
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TABLE OF CONTENTS
INTRODUCTION 9
DESCRIPTION OF THE URBAN AREA 10
CHARACTERIZATION OF THE TEST AREAS 11
ENVIRONMENTAL CONDITIONS 20
SAMPLING INSTRUMENTS AND METHODS USED 23
ANALYTICAL RESULTS OF URBAN STORM WATER
SAMPLES. 27
Bacterial ( 27 )--Organic ( 29 )--Nutrients ( 30 )_-Solids
( 33 )--Other Parameters { 35 )
ESTIMATES OF STORM WATER POLLUTION LOADS FROM
THE STUDY SITES 38
FINDINGS. . 42
RECOMMENDATIONS .44
ACKNOWLEDGEMENTS . . . . 45
REFERENCES • 46
APPENDIX. . . 47
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LIST OF TABLES
TABLE PAGE
1. General Description of the Test Areas ............... 13
2. Percentage of Land Devoted to Various Land Use
Activities in the Fifteen Test Areas, Tulsa, Oklahoma.
3. Population Characteristics of the Fifteen Test Areas. . . 17
4. Drainage Characteristics of Test Areas .............. 18
5. Street and Drainage Channel Characteristics .......... 19
6. Calculated Environmental Index (El) for the Fifteen
Test Areas, Tulsa, Oklahoma ........... ............ 22
7. Geometric Mean for Bacterial Density (Number/100 ml)
in Urban Storm Water from 15 Test Areas in Tulsa,
Oklahoma ... ....... ............................... 28
8. Average and Range for Organic Concentrations in
Urban Storm Water Runoff from 15 Test Areas in Tulsa,
Oklahoma. ....... . ..... ........... ....... .... ...... 31
9. Average and Range for Nutrient Concentrations in Urban
Storm Water Runoff from 15 Test Areas in Tulsa,
Oklahoma ...................... ........ ...... ..... 32
10. Average Values for Solids from 15 Test Areas in
Tulsa, Oklahoma ...... . ..... . ........ .............. 32
11. Calculated Average Yearly Loads from the Fifteen
OQ
Test Areas, Tulsa, Oklahoma .... ......... .......... Jy
12. Average Daily Loads Per Mile of Street from the 15
Test Areas, Tulsa, Oklahoma ........ . ............ . . 39
13. Comparison Between Average Daily Load from Storm
Water Runoff and Effluent from City of Tulsa1 s
Sewage Treatment Plants .................... . ...... 41
14. Selection of Best Multiple Regression Equations ....... 49
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LIST OF ILLUSTRATIONS
FIGURE PAGE
1. Location of Test Areas, Tulsa, Oklahoma ............. 12
2, Schematic Diagram of Storm Water Sequential Sampling
Equipment ............................... - ........ • • ^4
3. Instrument Enclosure and Sampling Probe Located at
Test Area No. 3 ......................... . .......... 25
25
4. Sampling Probe Hinge and Switch .....................
5. Tube Pump, Control Unit, Inverter, and 12- Volt battery
Located in Top Compartment of Enclosure ............. 26
6. Pressure Recorder and Inclined Sequential Sampler
Located in Bottom Compartment of Enclosure .......... 26
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STORM WATER POLLUTION
FROM
URBAN LAND ACTIVITY
INTRODUCTION
This paper covers an investigation of urban area storm water pollution,
or more precisely, an assessment of pollution in storm water as it
relates to land activity. The central purpose of this effort was to de-
sign a method of analysis which would enable the city planner and
engineer to assess the quality as well as quantity of storm water, and
to do so by looking at land activity, selected environmental factors, and
precipitation. In an engineering sense, the process was to relate
land use, land condition, and hydrological input to a pollutional output
for homogeneous areas. The predicted area load thus is aggregated to
provide an estimate of pollution. The process is similar to the deter-
mination of runoff from urban areas.
Given the relationship of man's activities to storm water drainage, altera-
tion in space and/or time through civic actions can be identified that
would reduce pollutional loads. Certain environmental factors such as
watershed characteristics and precipitation, alleviation of pollutant
conditions through civic actions can be identified that would reduce
pollutional loads in storm water. If urban planning and proper regula-
tion of land activity can reduce the overall costs associated with the
achievement of an acceptable quality of the environment in the urban area,
such activities should be considered the first order of business and an
adjunct to any construction of physical systems for collection, disposal,
or treatment.
Jerry G. Cleveland, Project Manager, AVCO Economic Systems/Tulsa
Operation, Tulsa, Oklahoma.
Ralph H. Ramsey, Ph.D., Project Engineer, AVCO Economic Systems/
Tulsa Operation, Tulsa, Oklahoma.
Paul R. Walters, Director, Environmental Systems, AVCO Economic
Systems Corporation, Washington, D. C.
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DESCRIPTION OF THE URBAN AREA
The urban area selected for study was Tulsa, Oklahoma, a relatively
young city. Incorporated in 1907, Tulsa is typical of many southwestern
and western urban areas. From 1940 until today the Tulsa Urban Area
has grown rapidly to a population of over 400, 000.
Tulsa was selected because of (1) separate storm and sanitary sewer
systems and (2) the land use data file maintained by the Tulsa Metropolitan
Area Planning Commission.
Drainage of storm water runoff from urban Tulsa is into two main re-
ceiving streams. The northern part of the city of Tulsa and the north
portion of Tulsa County drain into the Verdigris River, which in turn
drains into the Arkansas River at Muskogee, Oklahoma. The original
townsite and large portions of the western and southern parts of the city
drain directly into the Arkansas River.
Precipitation is generally well distributed throughout the year. The
season of maximum rainfall is the spring and much of this occurs
through thunderstorm activity. The high levels of soil moisture and the
high precipitation intensities produced by the thunderstorms help to
increase the percentage of storm runoff during this season. The pre-
cipitation regimen of the Tulsa area was examined by a study of the
number of events and the amount of rainfall in the events for a five
year period (1964-1968). The mean annual precipitation was 37.25
inches for this period. This amount was produced by an average of 93
events. Of these events, 52 produced amounts in excess of 0. 1 inch and
were probable producers of runoff from subareas within the urban
drainage basins of Tulsa.
10
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As mentioned earlier, Tulsa was selected because of the amount of land
use and planning data available to characterize homogeneous areas for
testing. Subdrainage basins representative of specific classifications
had to be selected, and appropriate sampling sites found. Selection
of discrete areas of land activity, although the main criterion for
selection, was limited by other factors that had to be considered. The
most important of these were:
1. accessibility of the sampling site.
2. size of area large enough to represent certain type
land use.
3. lack of known point sources of pollution in the
drainage area.
4. security of the sampling instruments from vandalism.
The locations of the 15 test areas and sampling sites are indicated in
Figure 1. A summary of the general description of the test areas is
given in Table 1.
Land use activity within each of the 15 drainage sheds was determined
by utilizing the TMAPC's Land Activity File. After the test areas had
been defined by true ridge lines, the census tracts, and the planning
blocks; a retrieval program was written to sum various land use ac-
tivities within each basin. The results of this retrieval are summarized
in Table 2 and Table 3.
The drainage characteristics (see Table 4 and Table 5) of each test area
were determined from the appropriate USGS quadrangle maps and the
City of Tulsa Storm Drain Atlas.
11
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FIGURE 1
LOCATION OF TEST AREAS
TULSA, OKLAHOMA =
.
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TABLE 1
GENERAL DESCRIPTION OF THE TEST AREAS
Test General Specific Socioeconomic
Area Landuse Zoning Class
No. Classification Classification
Remarks
1
Industrial
Commercial
Residential
Industrial
and
Residential
Residential
Pred. U-4A
Small amount
U-3A
Pred. U-3E
some U-1C,
U-2B, U-3A
Some upper-middle
class residential
Pred. U-1C Upper-middle
Small amount class
U-1B, U-3DH
U-4B
U-1C
Pred, U-1C
Light industrial, warehousing, industrial sales--
new industrial development containing little
outside storage--large portion still in construction
stage--water quality should reflect cement company
waste in lower reaches of watershed.
Shopping center with large paved parking areas--
includes drainage from large grassy slope (por-
tion of Pan American Research Laboratories
property)
Relatively new additions with little tree cover and
well-kept lawns--area swimming pool probable
drains into storm sewer--some commercial on
major streets.
Light to moderate industrial with approximately 1/3
residential--far upper reaches drain portion of
Tulsa State Fairgrounds--industrial is approximate-
ly 1/2 older development and 1/2 new development
or open land zoned for industrial use--considerable
amount of outside storage of industrial products--
railway service to most of area for shipping.
Upper-middle class Large older homes--great amount of tree cover--
some lower-upper some small older housing in upper reaches of
class-some lower watershed includes some commercial on major
middle class in streets, drainage from Woodward Park, Tulsa
upper reaches Garden Center, and overflow from Swan Lake.
Residential
portion-lower
middle class
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TABLE 1
GENERAL DESCRIPTION OF THE TEST AREAS (CONT'D)
Teat General Specific Socio-economic
Area Landuse Zoning Class
No. Classification Classification
Remarks
6
8
10
Industrial
Residential
Residential
Residential
Commercial-
Office and
Residential
U-4B
U-1C
U-1C
Pred. U-1C
traces'of
U-4B
3/4 U-3DH
and remain-
der in U-2A
and U-2B
Upper-middle
class
Lower-middle
class
Lower class
Some lower -
middle class
Older industrial area with considerable amount
of outside storage--water quality should reflect
waste from trucking firm--lower middle class
residences make up the upper and eastern reaches
of the watershed.
Postwar addition of mostly three bedroom frame
and brick houses with medium-sized trees--well-
kept area.
Postwar addition of mostly two bedroom frame and
brick houses with medium-sized tree cover.
Older houses of various sizes, many nearing delapi-
dation--ill-kept area residentially with some
commercial on major thoroughfares.
Upper portion of watershed is commercial-office
including multi-story buildings-middle areas of
watershed are largely open areas with considerable
tree cover--these areas have been cleared by the
Tulsa urban renewal authority for eventual rede-
velopment--some urban renewal work is still
underway in the area--lower areas of the water-
shed are old residences of various size houses
with great amount of tree cover.
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TABLE 1
GENERAL DESCRIPTION OF THE TEST AREAS (CONT'D)
Test General Specific Socioeconomic
Area Landuse Zoning Class
No. Classification Classification
Remarks
11 Residential U-1C
and
Commercial
12 Industrial U-4A
and
Commercial
13 Residential U-1A
14 Recreational
15
Lower-middle
class
Lower-upper
class
Residential U-1C
Lower-middle
class
This drainage basin is in the heart of Tulsa's
model city area--mostly small older frame
houses with great amount of tree cover--some
commercial on major streets.
Runways and supporting buildings with some
light industrial--great deal of open grassy areas.
Non-sewered, newly laid concrete pipe into un-
improved open channel, large lots with a number
of swimming pools--well-kept lawns.
Southern Hills Country Club--most of drainage
basin includes golf course.
Postwar addition of small Z-3 bedroom frame and
brick houses with coverage of medium sized trees.
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TABLE 2 PERCENTAGE OF LAND DEVOTED TO VARIOUS LAND USE ACTIVITIES
IN THE FIFTEEN TEST AREAS, TULSA, OKLAHOMA
Test PERCENT OF TOTAL AREA
Area Residential Commercial Industrial Institutional Transportation Open
No. Space
Unused Arterial Other
Space Streets Streets
Total
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
4.23
30.32
56.54
24.94
52.85
32.60
64.97
51.66
46.86
16.02
44.99
0
75.46
26.99
70.25
7.28
22. 38
.91
19.08
1.97
3.26
1. 52
6. 16
10.93
15.53
1.96
0
0
0
0
47.35
.36
18.34
.20
35.05
0
4.74
0
0
5.03
1.41
0
0
0
0. 15
0
4. 18
5.65
6.51
.54
9. 14
1.42
0
1.94
1.84
0
2. 83
0
1.35
1.46
1.44
0
2.98
2.96
2.45
0
3.32
0
.49
.37
48.36
0
0
0
0
24. 55
3.46
.85
9.86
0
0
0
0
0
.61
50.23
0
65.39
0
24.77
.72
16.00
5.33
5.92
2.99
.51
4. 27
4.69
15.53
3.44
0
2.36
0
6.76
6.99
5.42
2.36
5.86
3.94
2. 17
1.52
14.22
10.93
18.93
5.88
0
5.19
4.56
0
7.72
14.80
16.73
16.95
15.78
20.92
22. 33
14. 22
26.55
31. 55
35.80
0
14.62
3.04
21.62
99.95
99.90
100. 18
99.98
99.99
99.98
99.99
100.01
99.96
99.99
99.92
100.00
100.46
99. 98
99.98
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TABLE 3
POPULATION CHARACTERISTICS OF THE FIFTEEN TEST AREAS
TEST
AREA
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
TOTAL P
LIVING
UNITS
100
369
1147
1122
1765
501
616
715
267
425
3396
0
168
77
282
'OPULA'
350
1100
3925
3625
4525
1200
2275
2400
875
885
2800
0
500
250
830
POPULATION
ESTIMATOR
PEO. /UNIT
RESIDENTIAL
AREA
ACRES
3.50
3.00
3.42
3.23
2. 56
2.37
3.70
3.35
3.26
2.08
2. 30
0
3.01
3.01
2.95
29
84
311
234
268
120
128
109
30
33
367
0
160
71
52
RESIDENTIAL
DENSITY
PEO. /RES. ACRE
12.07
13.09
12.62
15.49
16.88
10.00
17.77
22.02
29. 17
26.82
21.25
0
3.13
3.52
15.96
TOTAL
AREA
ACRES
686
272
550
938
507
368
197
211
64
206
815
223
212
263
74
AVERAGE
DENSITY
PEO. /ACRE
0. 51
4.04
7.13
3.86
8. 93
3. 26
11. 55
11.37
13.67
4.30
9.57
0
2.36
0. 95
11. 22
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TABLE 4. DRAINAGE CHARACTERISTICS OF TEST AREAS
TEST
AREA
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
(1)
A
686
272
550
938
507
368
197
211
64
206
815
223
212
263
74
(2)
L
9050
4230
6890
9260
11200
2170
4500
4800
2600
6350
9000
5710
7840
6400
2700
(3)
LC
6000
2040
3000
4800
4800
3600
2100
1800
1380
3300
4200
2400
2600
3480
1600
(4)
H
113
92
186
126
140
91
85
95
60
140
162
58
140
171
30
(5)
Sc
0.011
0.011
0.009
0.010
0.013
0.009
0.013
0.013
0.011
0.032
0.007
0.007
0.015
0.014
0.012
(6)
SL
3. 19
3.48
3.82
2.89
3.29
2. 19
2.89
1.67
1.55
2. 26
1.83
0.75
4.60
4. 25
0.78
(7)
C
30
55
27
51
30
24
32
37
31
74
41
46
23
11
38
(8)
FF
0.83
2.85
2.66
1.77
0.96
1.24
1.94
2.84
1.47
0.82
2.01
1.68
1.37
0.95
1. 26
(9)
GxlO2
1.07
0.95
1.41
1.00
2. 16
0.55
1. 52
2.99
3.61
4.69
2. 24
4.53
2.54
2. 24
3.21
Legend:
1. Test Area (A), acres 5.
2. Length of the main stream (L),
feet. 6.
3. Length of the main stream from 7.
the sampling site to the point 8.
nearest area centroid (Lc) feet.
4. Fall of the watershed (H), feet. 9.
Average main channel slope
(Sc), feet per foot.
Average land slope (SL), percent.
Impervious cover (C), percent.
Form Factor (FF) = 43, 560 A/ (Lc)'
dimensionless.
Geometry Number (G)
(H)
(43,560) (A) (SL)
dimensionle ss
-------
TABLE 5.
STREET AND DRAINAGE CHANNEL CHARACTERISTICS
TEST
AREA
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
TOTAL
AREA
ACRES
686
272
550
938
507
368
197
211
64
206
815
223
212
203
74
STREETS
ARTERIAL1
ACRES
48
15
13
55
20
8
3
30
7
39
48
0
11
12
0
MILES
3. 44
1. 21
1. 07
4. 52
1.63
0. 62
0. 26
2. 48
0. 60
3. 21
4. 00
0
0. 88
1. 14
0
OTHER2
ACRES
53
41
92
159
80
77
44
30
17
65
292
0
31
8
16
MILES
13.83
10.70
24. 01
41.50
20.88
20. 10
11.48
7.83
4.44
16.97
76,21
0
8.09
2.09
4. 18
DRAINAGE CHANNEJ
TOTAL3
MILES
1.71
0.80
1.30
1.75
2. 11
0.41
0.85
0.91
0.49
1.20
1.70
I. 08
1.48
1.21
0. 51
COVERED'
MILES
1.05
1.07
1.25
3.30
2. 14
1.55
1.02
1.08
0.78
1.13
3.75
0
0.82
0
0.69
Arterial streets are major thoroughfares.
^Other streets are all streets less arterial streets.
^ Total drainage channel as used here refers to the length of the main
interceptor channel.
Covered drainage channel as used here refers to all covered drainage
conduit (interceptor and lateral) greater than 24 inches diameter.
-------
ENVIRONMENTAL CONDITIONS
In 1968 the Tulsa City-County Health Department conducted a Commu-
nity Block Survey in the City of Tulsa. The purpose of the survey was to
delineate the general environmental condition that existed in the
community. An analysis of the data resulting from this survey provides
a method of locating environmental conditions which contribute to the
origin, frequency, and distribution of communicable disease within a
community. Also, with this data and additional census block data, a
community can be stratified into socioeconomic areas.
The environmental factors included in the survey were land use, ex-
terior housing quality, water supply, human waste disposal, refuse
storage, rubble accumulations, junked cars, dilapidated sheds, vacant
lot sanitation, poor drainage areas, vector harborage, and the presence
of livestock, poultry, or dog pens.
Since the normal procedure (1) in stratifying a community into socio-
economic strata is not applicable to large areas and could not be applied
to commercial or industrial areas, a method was devised by the author
of this study for determining the general environmental condition of the
fifteen test areas. An Environmental Index (El) was calculated for each
of the test areas, as follows:
Environmental Index (El) = f (housing condition, vacant lot
condition, parcel deficiencies)
Assuming that the parcel deficiencies should be weighted
more heavily than the housing conditions and that the
housing conditions should be weighted more heavily than
the vacant lot conditions:
TTT 2 (A) + B + 3 (C)
EI= _
Where:
Total Housing Structures
A "(1) (G) + (2) (F) + (3) (P)
Note: G = no. of good vacant lots
F = no. of fair vacant lots
P = no. of poor vacant lots
20
-------
Total Vacant Lots
B = (1) (G) + (2) (F) + 3 (P)
Note: G = no. of good vacant lots
F = no. of fair vacant lots
P = no. of poor vacant lots
Total Structures —Total Deficiencies
C" — _
Total Structures
Note; Total deficiencies include the sum total
of refuse, burners, rubble, lumber,
old autos, poor sheds, livestock, poul-
try, and privies.
The above three factors (A, B, and C) are a measure of the general
housing condition, the vacant lot condition, and the parcel deficiencies,
respectively. Factors A and B vary from a low of . 33 to a high of
1.00. Factor C varies from a negative number to 1.00. The smaller
numbers indicate poor environmental conditions while the larger
numbers indicate good environmental conditions.
Applying the above formula will result in a number that varies from a
negative number to a maximum of 1. 00. A value of 1. 00 will denote
an area of all good houses, all good vacant lots, and no parcel deficiencies,
Not included in the above index are several other factors that, if used,
would result in a better measure of the "general environmental condi-
tion of an area. " Such items are: air pollution sources, population and
structure density, point water pollution sources, parks, noise level, and
traffic volume. If these data items were available and each could be ex-
pressed by a number and weighted, a better El could be developed.
Applying the above formula to the survey data, an El for each of the
Test Areas was calculated. Table 6 presents these calculations with the
resulting El.
21
-------
TABLE 6
CALCULATED ENVIRONMENTAL INDEX (El)
FOR THE FIFTEEN TEST AREAS
TULSA, OKLAHOMA
NJ
NJ
Test
Area
No.
Calculated
Factor1
B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
.99
1.00
1.00
1.00
1.00
.68
1.00
1.00
.70
.84
.46
1.00
1.00
1.00
1.00
1.00
.83
1.00
1.00
.62
1.00
1.00
.53
.97
.56
1.00
1.00
1.00
1.00
.99
1.00
.71
.98
.48
.96
.62
-.19
.93
-. 34
.94
1.00
.71
Environmental
Index
(El)
1. 00
.99
. 97
. 86
.99
. 57
.98
.81
.23
.91
.08
1. OO2
.97
1. 00
. 86
Calculated factors from environmental survey data for use in equation 1.
^Test Area No. 12 was assumed to have an El of 1. 00.
-------
SAMPLING INSTRUMENTS AND METHODS USED
The collection of storm water runoff samples required the use of several
different types of instruments and methods. A stationary automatic sam-
pling method was used when a time series of samples was desired.
Standard manual sampling procedures (grab sampling) were used when
baseline samples or additional storm water runoff samples were collected.
The bacteriological samples were collected in sterile plastic bags.
A schematic diagram of the storm water sequential sampling equipment
is shown in Figure 2. Views of the sampling equipment are shown in
Figure 3 through 6.
After sample collection, all samples were stored and analyzed in
accordance with "Standard Methods for the Examination of Water and
Waste Water, Twelfth Edition. " Bacteriological samples were examined
for total coliform, fecal coliform, and fecal streptococcus by the mem-
brane filter (MF) technique with the respective use of M-Endo, M-FC,
and KF Streptococcus media. The organic pollution parameters measured
were 5-day BOD, COD, and TOG. Analyses for TOG (Total Organic
Carbon) were preformed by the Civil Engineering Department, University
of Arkansas with the use of a Beckman TOC Analyzer (Model 915). The
nutritional content of the samples were indicated by tests for organic
Kjeldahl nitrogen and soluble orthophosphates. Measurements were also
made for total solids, suspended solids, dissolved solids, volatile sus-
pended solids, volatile dissolved solids, pH, chloride, and specific
conductance.
During the period from October 1968 to September 1969, a total of
456 composite and grab samples were collected and analyzed from
30 separate precipitation events. A total of 37 baseline samples were
collected on four days from the test areas that had dry weather flow.
23
-------
SCHEMATIC DIAGRAM OF STORM WATER SEQUENTIAL SAMPLING EQUIPMENT
COLE-PARMER MASTERFLEX
TUBE-PUMP
INCLINED
SEQUENTIAL
SAMPLER
PUMP MOTOR CONTROL
OVERFLOW
JUG
TYGON
SAMPLING TUBE
VOLTAGE
REGULATOR
I I I I I I I I I
SWITCH
ALUMINUM CONDUIT
SWITCH
ADJUSTMENT
POLYPROPYLENE PICK-UP TUBE
POLYETHYLENE FLOAT
PRESSURE
BOX
VOLTAGE INVERTER
*— FOXBORO WATER PRESSURE
RECORDER
12 VOLT
MARINE TYPE
BATTERY
I I I I I I I I I I 1 I
. \e\l
I I I I I
CUTAWAY OF TYPICAL DRAIN
STRUCTURE
i n 11111 11 11 rrrn 11 i\
FIGURE 2.
-------
Figure 3. --Instrument enclosure and sampling probe
located at Test Area No. 3.
Figure 4. --Sampling probe hinge and switch.
_
-------
Figure 5. --Tube pump, control unit, inverter, and
12-volt battery located in top compartment of enclosure.
Figure 6. --Pressure recorder and inclined sequential
sampler located in bottom compartment of enclosure.
26
-------
ANALYTICAL RESULTS OF URBAN STORM WATER SAMPLES
This section presents the results of the analytical observations of the
various pollution parameters measured throughout the testing period.
These results are presented in tabular form in five pollution classifica-
tions: Bacterial, Organic, Nutrient, Solids, and Other Parameters.
The results are presented as average values of the separate precipita-
tion events and not from the averaging of the individual samples
collected. This was done to more effectively compare the individual
event characteristics. Since continuous sampling on each site for each
event was not practicable, the averaging of the sequential samples
for the sites which were continuously monitored was felt more represen-
tative for event comparison between these sites and those where only
grab samples were obtained.
Bacterial
The three bacteriological parameters measured on this project were
fecal coliform, total coliform , and fecal streptococcus. All samples
were examined by the membrane filter (MF) technique.
The geometric means of the three bacteriological parameters measured
from each test area are shown in Table 7. Below is a comparison of
the arithmetic mean of the fifteen test areas with the arithmetic average
of the four seasons from the Cincinnati Study (2)
Parameter Number/100 ml.
Tulsa Study Cincinnati Study
All Wooded Street Business
Test Areas Hillside Gutters District
Total Coliform 134,000 65,415 95,750 107,500
Fecal Coliform 1,940 630 13,420 14,950
Fecal Strep. 10,245 10,473 78,825 37,000
For the fifteen test areas, the fecal coliform value was, on the average,
3% of the total coliform value. The average fecal coliform to fecal
streptococcus ratio varied from a low of 0. 081 (Test Area No. 10) to a
high of 0. 893 (Test Area No- 9). These low ratios indicate the source
of the bacterial pollution to be warm-blooded animals other than man
(2). At the start of the project, it was suspected that Test Area No. 13
might record a high fecal coliform to fecal streptococcus ratio due to
this drainage basin being unsewered and utilizing septic systems for
liquid waste disposal. After checking with the authorities at the Tulsa
27
-------
TABLE 7
GEOMETRIC MEAN FOR BACTERIAL DENSITY (NUMBER/100 ml) IN URBAN STORM
WATER FROM 15 TEST AREAS IN TULSA, OKLAHOMA
DATES: SEPTEMBER 1968 TO SEPTEMBER 1969
00
Test Land
Area Use
No. Classification
1 Light Industrial
2 Commercial-Retail
3 Residential
4 Med. Ind. -Residential
5 Residential
6 Medium Industrial
7 Residential
8 Residential
9 Residential
10 Commercial (Office)
11 Residential-Com. Mix
12 Openland and Runways
13 Residential
14 Recreation-Golf
15 Residential
Total Coliform
Geometric
mean
71, 000
43, 000
100, 000
25, 000
150,000
140,000
32,000
240,000
400,000
130, 000
370,000
56, 000
28, 000
5, 000
220, 000
Fecal Coliform
Geometric
mean
940
1,900
3,300
770
1, 500
18, 000
120
450
290
300
620
10
180
370
350
Fecal Streptococcus
Geometric
mean
4, 200
780
15, 000
12, 000
3, 800
24, 000
2, 300
5,800
7, 600
30, 000
6, 800
700
5,700
21, 000
14, 000
-------
City-County Health Department, it was learned that the septic systems
in this area function properly, and very few complaints have been re-
ported from this area in regard to "pooling" of septic systems.
Test Area No. 9 a small drainage area with poor environmental con-
ditions had the highest total coliform geometric mean (400, 000 #/100 ml. ).
The lowest total coliform mean (5, 000 #/100 ml.) was recorded from
Test Area No. 14, which is a Country Club golf course. This low
geometric mean may be due to the small number of sample analyses
from this drainage shed. The one characteristic of this shed which
distinguishes it from the other test areas is that the shed has two small
recreation ponds on the drainage channel; these ponds capture almost
all of the runoff water. The only time that the drainage channel flows is
after or during a precipitation event of high intensity or large amount.
Such an event normally occurs during the spring of the year. Due to this
characteristic, the samples actually collected were from the overflow
of impounded water rather than from actual runoff water.
No clear patterns were established by ranking the test areas by each
separate bacteriological parameter. Patterns refer to groupings as to
land activity --e. g. , residential, commercial or industrial.
Organic
In general, the three organic pollution parameter concentrations cannot
be considered to be high when compared to effluents from secondary
sewage treatment plants. The highest average values, with the excep-
tion of Test Area No. 10, occurred from test areas with moderate to
heavy tree cover. Also, all of these areas had one other common
factor: the condition of the drainage channels offered many opportunities
for the leaves and grass trimmings to become trapped in depressions,
thus allowing an opportunity for decomposition. This condition could
explain the higher average BOD values. Test Area No. 10 is a downtown
commercial type drainage shed with a high percentage of impervious
cover and traffic volume.
The BOD/COD ratio varied from 0. 105 (Test Area No. 10) to 0. 342
(Test Area No. 15). The average ratio from all fifteen sites was 0. 171.
The high ratio from Test Area No. 15 may be due to the small number
of events sampled. Also, Test Area No. 14 is not typical, since the
samples collected were not from runoff, but from overflow water from
the ponds on the drainage shed.
The average BOD/TOC ratio from the fifteen test areas was 0.405. The
range of values was from 0. 289 (Test Area No. 1) to 0. 577 (Test Area
29
-------
No. 15). In general, these ratios are not useful for characterization of
the test areas. The ratios show considerable variation between the test
areas, and each test area has high standard deviations.
Total Organic Carbon (TOC) was measured in conjunction with BOD and
COD to further characterize the test areas. It was hoped that a con-
stant relationship could be found between samples. The TOC/COD ratio
varied from 0.289 (Test Area No. 7) to 0. 847 (Test Area No. 15). The
average of all fifteen test areas was 0.468.
The average values of the fifteen test areas show no positive groupings.
The test areas with the three highest values are each classified
differently. In several instances the TOC concentrations were higher
than the COD concentrations, indicating that the standard COD test does
not detect some organic compounds. At present, this finding cannot be
readily explained.
Table 8 summarizes the analytical results from the fifteen test areas by
averages and ranges which are based on the average of the separate
rainfall events.
Nutrients
Organic Kjeldahl nitrogen and soluble orthophosphate were the nutrients
measured in the study. The average and range of values of these two
components are shown in Table 9.
Several possibilities as to the sources of nutritional pollution can be ad-
vanced with knowledge of the present land use on some of the sites.
Other sites exhibit such variation as to season, level, etc. , that logical
deductions as to cause cannot be made unless more complete land use
information is available.
The organic Kjeldahl nitrogen measured in the runoff could have been
obtained from several sources. The entrainment of organic matter by
surface flows and the eluviation of decay products from organic matter
are probably responsible for a large portion of the nitrogen load. Deriv-
atives from commercial fertilizers are potential high pollution sources
in the event that precipitation events occur at high intensities after
these fertilizers have been applied on the land surface. Ammonia and
organic nitrogen are also washed from the air at rates of 2 to 6 pounds
per year (3).
A valid apportionment of the measured nutrients to these sources is not
possible, and only inferences can be made. In the spring, Test Areas
30
-------
TABLE 8
AVERAGE AND RANGE FOR ORGANIC CONCENTRATIONS IN URBAN STORM WATER
RUNOFF FROM 15 TEST AREAS IN TULSA, OKLAHOMA
DATES: SEPTEMBER 1968 TO SEPTEMBER 1969
Test Land Use
Area Classification
No.
1 Light Industrial
2 Commercial-Retail
3 Residential
4 Med. Ind. -Res.
5 Residential
6 Med. Industrial
7 Residential
8 Residential
9 Residential
10 Commercial (Office)
11 Res .-Com. Mix
12 Openland-Runways
13 Residential
14 Recreation (Golf)
15 Residential
BOD (mg/1)
COD (mg/1)
TOC (mg/1)
Avg.
13
8
8
14
18
12
8
15
10
11
14
8
15
11
12
Max.
23
16
21
29
38
18
17
25
15
27
23
16
39
23
24
Min.
3
2
2
4
3
6
2
3
4
4
4
6
4
6
1
Avg.
110
45
65
103
138
90
48
115
117
107
116
45
88
53
42
Max.
215
94
162
232
261
133
69
405
263
240
167
69
220
74
62
Min.
54
21
20
14
37
39
12
50
40
36
80
21
13
22
18
Avg.
43
22
22
42
48
34
15
37
35
28
33
20
35
29
34
Max.
71
36
31
74
85
42
20
82
61
80
49
40
66
36
75
Mir
17
12
14
22
11
12
0
5
13
0
17
6
17
18
11
-------
TABLE 9
AVERAGE AND RANGE FOR NUTRIENT CONCENTRATIONS IN URBAN
STORM WATER RUNOFF FROM 15 TEST AREAS IN TULSA, OKLAHOMA
DATES: SEPTEMBER 1968 TO SEPTEMBER 1969
Test Land Use
Area Classification
No.
1 Light Industrial
2 Commercial-Retail
3 Residential
4 Med. Ind. -Res. Mix
5 Residential
6 Med. Industrial
7 Residential
8 Residential
9 Residential
10 Commercial (Office)
11 Res.-Com. Mix
12 Ope nland-Runways
13 Residential
14 Recreation (Golf)
15 Residential
Organic
Kjeldahl Nitrogen
(mg/1)
Avg. Max. Min.
1.11 2.95 0.06
0.95 3.61 0.17
1.48 3.28 0.24
0.97 3.03 0.00
0.72 1.80 0.00
0.65 1.50 0.16
0.80 1.60 0.01
0.69 2.52 0.00
0.67 1.30 0.14
0.83 2.40 0.06
0.66 1.82 0.13
0.39 1.26 0.01
1.46 5.32 0.15
0.96 2.40 0.13
0.36 0.98 0.15
Soluble
Orthophosphate
(mg/1)
Avg. Max. Min.
3.49 15. 10 1. 20
0.86 1.50 0.24
1.92 3.70 0.10
1.05 3.00 0.36
0.87 1.53 0.53
0.86 1.40 0.58
0.67 1.43 0.28
1.15 2.60 0.00
1.02 1.92 0.48
0.70 1.50 0.30
1.11 1.88 0.60
0.54 1.68 0.20
1.18 1.97 0.10
0.99 2.25 0.09
0. 81 1. 17 0.35
TABLE 10
AVERAGE VALUES FOR SOLIDS
FROM 15 TEST AREAS IN TULSA, OKLAHOMA
DATES: SEPTEMBER 1968 TO SEPTEMBER 1969
Test Land Use
Area Classification
No. Total
1 Light Industrial 2242
2 Com. -Retail 275
3 Residential 680
4 Med. Ind. -Res. 616
5 Residential 271
6 Med. Industiral 346
7 Residential 413
8 Residential 382
9 Residential 417
10 Commercial-Office 431
11 Res.-Com. Mix 575
12 Openland-Runways 199
13 Residential 469
14 Recreation (Golf) 592
15 Residential 273
Solids
Suspended
Total
205?.
169
280
340
136
195
84
240
260
300
401
89
332
445
183
Volatile
296
48
53
83
54
55
28
96
70
61
95
24
85
206
122
(mg/1)
Dissolved
Total
190
106
400
276
135
151
328
141
157
132
174
110
137
147
89
Volatile
111
70
317
87
76
66
124
75
98
71
83
59
73
53
56
32
-------
2, 3, and 13 exhibit increased levels of organic nitrogen which can be
attributed to fertilization of lawns within these high-income, residential
areas. Other sites have high values during the fall, winter, and spring
which could be assigned to products of organic decay. A decrease of
this form is seen during the growing season due to the rapid assimilation
of any free nitrogen by growing vegetation,,
The varying amounts of orthophosphates found in the analysis of the test
areas can likewise be assigned to various sources. The frequency of
street sweepings; the amounts, types, and location of organic material
and its decay products; the application of commercial fertilizer; the
season; the number of sampled events; and the drainage characteristics
can either singularly or in combination influence the washout of orthophos-
phates from the test site.
The presence of a concrete plant upstream from the sampling point was
the prime cause of high level of orthophosphates in Test Area No. 1.
Test Areas No. 3 and 13 exhibited high average orthophosphate levels
which resulted from the heavy lawn fertilizations in the spring. The
high maximum levels which are shown for 8 and 14 are caused by or-
ganic decay products. Test Area 12 had low orthophosphate levels due
to low runoff volumes and to the lack of decidous vegetation.
If the amounts of orthophosphate washed from the test area are apportioned
just to the impermeable portions of the site as shown on Table 4, Test
Area 10 which is in the central business district has 40 34 pounds--the
lowest annual amount per impermeable acre. This finding appears
reasonable in that most of the runoff-producing portion of the streets is
swept each night, and there is relatively little organic matter from
vegetal sources in the drainage ways of the area. Test Area No. 2 was
also low in pounds per impermeable area, but since it contained a higher
percentage of residential area with its characteristic vegetation the yield
was greater than from the pervious areas. The remaining areas had
larger yields of orthophosphates per impervious area; this finding was
attributed to the larger amounts of tree cover in these older developed
areas.
Solids
The five solids constituents measured on this project were total solids
(TS), suspended solids (SS), volatile suspended solids (VSS), dissolved
solids (DS) and volatile dissolved solids (VDS). The arithmetic averages
of these constituents are summarized in Table 10.
Total solids is the sum total of the suspended solids and dissolved solids
fractions and is closely related to the topography and soil conditions of
33
-------
the various test areas. It should be noted that, due to the sampling
techniques, total solids is not a measure of all solids found in urban
storm runoffo "All solids" would be sum of total solids and the
floating and large particles not picked up by the sampler used on this
project. These "other solids" include such materials as tree limbs,
leaves, paper, plastics, etc. These materials are not only objectionable
as to the aesthetics, but indirectly add to the bacterial, organic, and
nutrient storm water loads. For example, during late fall a large
portion of the leaves reach the storm drainage system and become
trapped in depressions within the system. Between the event that
carries the leaves to the system and the next rainfall event, the leaves
have time to decay and disintegrate, thus adding additional organic
and nutrient contaminants to the runoff water.
The average values for the solids show considerable variation. The
lowest average value (199 mg/1) was found from Test Area No. 120 The
highest average value (2242 mg/1) was found from Test Area No. 1.
This extremely high concentration can be explained by exposed open land.
Shortly after the start of the project, construction began on a large
apartment house complex. The land was stripped of its ground cover,
cuts were made for streets, and water and sewer line trenches were
dug. Construction continued throughout the project. Therefore, this
test area is representative of a drainage basin that is under development.
The second highest average value (680 mg/1) recorded was from Test
Area No. 3. This test area is a new fully developed middle-class sub-
division. A large portion of the main drainage channel is open and
unimproved, with unstable banks.
The percent of suspended solids varied from a low of 38% (Test Area
No. 12) to a high of 82% (Test Area No. 1). The remaining test areas
had percentages from 40% to 60%. The low value from Test Area No.
12 is due to the fact that the runoff comes from airport runways and is
channeled to the main drainage channel by well-kept drainage ditches
alongside the runways. Also, the main sources of suspended solids in
fully developed residential and commercial areas are the streets, in
that they collect the dust, dirt, and clay droppings from automobiles. It
is interesting to note that Test Area No. 12 also had one of the four
highest volatile suspended solids to total suspended solids ratio.
Generally, the volatile suspended solids followed the same pattern as
suspended solids, and formed 20-50 percent of the total suspended solids.
It should be remembered that high values of volatile matter in storm
water may not necessarily be decomposable organic material. The
relatively low BOD values found on this project support this idea, as does
the fact that clay will lose considerable weight on ignition.
34
-------
The average total dissolved solids ranged from a low of 89 mg/1 (Test
Area No, 15) to a high of 400 mg/1 (Test Area 3). The overall mean of
the test areas was 178 mg/1. The volatile portion of the dissolved
solids averaged 49% for the 15 test areas. The range of values was from
33% (Test Area No. 4) to 62% (Test Area No. 9).
Other Parameters
In addition to the bacterial, organic, nutrient, and solids pollution para-
meters measured on this project, the pH, chloride, and specific
conductance were measured.
The range of the average pH from the fifteen test areas varied from a
high of 8. 4 (Test Area No. 1) to a low of 6. 8 (Test Area No. 15). All
of these average values are within the State of Oklahoma's Water Quality
Criteria for the Arkansas River and Verdigris River. The Criteria
call for the pH to be between 6. 5 and 8. 5, and all values below 6. 5 and
above 8. 5 must not be due to a waste discharge. The only observations
of pH values that were higher than these limits were found from Test
Area No. 1, which can be classified as a Light Industrial Area. The
test area recorded a maximum pH of 12. 2 on October 16, 1968. This
particular sample was the third in a series of seven 30-minute composite
samples, and was collected approximately 5.4 hours after the rainfall
event started. All the samples collected from this test area had consis-
tently high pH values. The only sources of land contaminants that could
be found within this drainage shed were piles of cement, waste concrete,
and other waste associated with a concrete batch plant operation. The
batch plant is located on the bank of the unimproved open channel that
drains the lower portion of this shed.
The only test area that approached the lower limit of the State of
Oklahoma's pH criteria was Test Area No. 15. The average pH value
was 6. 8 and the lowest observed value was 6. 4. The pH value of the
runoff from Site 15 can be attributed to contributions from several
factors. The soils of the watershed were developed under forest-like
conditions found along the terraces adjoining the Arkansas River bottoms
before Tulsa developed. These conditions produced soilds which were
slightly acid. This area is located in a fairly old residential area, and
tree cover and other vegetation levels are approaching those levels
once found in the primitive state. The decomposition of vegetation both
on the ground surface and in covered storm sewers of the area contri-
butes to lower pH values in the runoff water.
Average concentrations of chloride (Cl) from the fifteen test areas varied
from 2 mg/1 (Test Area No. 15) to 46 mg/1 (Test Area No. 7). None
35
-------
of these values are excessive considering the average concentrations
found in the two receiving streams in Urban Tulsa. The 50% value for
chloride measured in the Arkansas River at Sand Springs, Oklahoma is
970 mg/1. The average concentration found in Bird Creek is 126 mg/1.
The only samples collected which were expected to show a possible in-
crease in concentrations were those of February 20, 1969. These
samples were collected from runoff originating from melting snow. The
runoff samples were from the street source areas only, since the snow
had not started melting on the roofs and yard areas. The runoff can be
attributed to the heavy traffic volumes on the streets. The results of
these observations were very low (less than 15 mg/1).
Due to the very few snow and ice events in the Tulsa Urban Area, very
limited amounts of salt are applied to the streets for snow and ice con-
trol. The main material used in the City of Tulsa for snow and ice
control is sand. Due to the very limited use, the natural concentrations
found in the receiving streams, and the concentration found from the
fifteen test areas, the chloride (Cl) load reaching the receiving streams
does not present a problem in the Tulsa Area.
The average specific conductance from the fifteen test areas varied
from a low of 36 micromhos/cm to a high of 220 micromhos/cm. The
mean ratios of dissolved solids to specific conductance varied from
1. 19 (Test Area No. 14) to 2. 54 (Test Area No. 15). The overall
average of the means of the test areas was 1. 579. None of the average
values of the fifteen test areas deviated significantly from this mean,
with the exception of Test Area No. 15. This fact tends to indicate
that the dissolved substances in the runoff water from this test area are
higher in organic compounds than in inorganic ions. This finding is
also supported by the relatively high volatile dissolved solids to total
dissolved solids ratio of 0. 594. This ratio, as compared to the other
fifteen test areas, was second highest.
Phenols determinations were made on samples collected on June 17,
1969 from Test Areas No. 2, 5, 6, 10 and 11. The results of these
determinations are shown below;
Test Area No. p, g/1
2 14
5 18
6 10
10 35
11 18
The above five values are within the range (1-30 /•< g/1) as reported in
the Detroit-Ann Arbor study (4). It should be noted, however, that
36
-------
Test Area No. 10 recorded the highest concentrations (35/A g/1). This
test area is a downtown central business district having a high percen-
tage of streets and traffic volumes.
Since phenols are subject to rapid biochemical and chemical oxidation,
they must be preserved and stored at cold temperatures if not analyzed
within 4 hours after collection. Due to this requirement and to the
sampling procedures used on this project, additional determinations
were not made.
37
-------
ESTIMATES OF STORM WATER POLLUTION LOADS
FROM
THE STUDY SITES
In the preceding section, the data presented was based on factual
analytical observations whereas in this section the calculated pollution
loadings presented are estimates. These calculations were based on
valid assumptions and current data. Also, for comparison, the com-
bined effluent loads for the four treatment plants in Tulsa are presented.
The amounts of the various pollution parameters from each site were
obtained by multiplying the average values of the parameter by the
estimated monthly flows. A more representative figure would have
been obtained by basing the figure on the acres of imperviousness with-
in each site. Further differentiaion was not attempted since the samples
taken at each site were not from source points within the sites. Table
11 and Table 12 give the estimted average yearly loads per acre and
the estimated average daily loads per mile of street from each test area,
respectively. Table 13 presents the comparison between the average
daily load from storm water runoff and the effluent from Tulsa's sewage
treatment plants. The characteristics of these plants are:
Flat Rock (4 mgd)--primary and secondary treatment processes —
secondary treatment accomplished by contact stabilization--
discharge to Bird Creek.
Coal Creek (4 mgd)--primary and secondary treatment processes--
secondary treatment processes accomplished with trickling
filters processes—discharge to Bird Creek.
Northside (11 mgd) = -primary and secondary treatment processes--
secondary treatment accomplished with trickling filter pro-
cesses—discharge to Bird Creek.
Southside (21 mgd)--primary treatment processes — discharge to
the Arkansas River.
Considering the loading estimates presented in the tables, it is
reasonable to speculate that with the continued urbanization of the Tulsa
area in conjunction with the demands for increased efficiencies in
domestic and industrial waste treatments facilities, storm water runoff
in the Tulsa area may well become the prime source of stream pollution
within the next decade.
Of greater importance is not the estimated average daily loads, but
the "shock" loads of urban storm water runoff. There are an average
of 52 rainfall events over 0. 1 inch in Tulsa each year. Assuming each
event to be equal and the yearly load to be 365 times the average daily
load, each rainfall event will carry approximately seven times the
38
-------
TABLE 11
CALCULATED AVERAGE YEARLY LOADS FROM
THE FIFTEEN TEST AREAS, TULSA, OKLAHOMA
Test
Area
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Pollution Load: Ibs. /acre/year
Acres
686
272
550
938
507
368
197
211
64
206
815
223
212
263
74
BOD
30
27
14
44
33
21
15
33
20
48
35
25
25
12
25
COD
250
150
110
320
250
160
90
250
230
470
290
140
150
60
90
Organic
Nitrogen
2. 5
3. 3
2.6
3. 0
1. 3
1. 1
1. 5
1. 5
1. 3
3.6
1. 7
1. 2
2.4
1. 1
0. 8
Soluble
Orthophosphate
8. 0
2. 9
3. 3
3. 3
1.6
1.5
1. 3
2. 5
2. 0
3. 1
2. 1
1. 7
2. 0
1. 1
1. 7
Total
Solids
5100
920
1200
1900
490
600
790
840
830
1900
1400
630
780
660
570
TABLE 12
AVERAGE DAILY LOADS PER MILE OF STREET
FROM THE 15 TEST AREAS, TULSA, OKLAHOMA
Test
Area
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Total
Street
Average
BOD COD
Mile s
11.
7.
14.
28.
16.
12.
6.
6.
3.
12.
49.
3.
5.
2.
2.
46
41
87
40
32
24
84
97
11
99
05
3.9*
58
07
06
4.
2.
1.
3.
2.
1.
1.
2.
1.
2.
1.
4.
2.
4.
2.
85
54
41
98
80
70
20
72
12
10
60
53
58
26
47
41.
15.
11.
29.
21.
12.
7.
20.
13.
20.
13.
25.
15.
20.
8.
10
12
46
29
43
73
20
89
09
44
29
47
16
54
67
Load: Ibs. /day/mile of street
Organic Soluble
Total Kjeldahl Orthophosphate
Solids
838
92
120
175
43
49
63
69
47
82
66
113
81
23
56
Nitrogen
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
41
32
26
28
11
09
12
12
07
16
08
22
25
37
07
1.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
30
29
34
30
13
13
10
21
11
13
15
30
20
38
17
*Miles and Acres of Airport Runways
39
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Table 13
Comparison Between Average Daily Load from Storm Water
Runoff and Effluent from City of Tulsa's Sewage
Treatment Plants
Estimated Average Daily Load (Ib/day)
Pollution Storm Water Effluent from Sewage Percent of Storm Water
Parameter Runoff Treatment Plants * Load of Total Load
BOD 4,500 19,000 19%
COD 31,000 67,000 32%
Suspended
Solids 107,000 18,000 84%
Organic Kjeldahl
Nitrogen 350 760 32%
Soluble Ortho-
phosphate 470 11,000 4%
Estimate based on 1968 flows and concentrations
Estimate based on a 50% suspended solids fraction of Total solids.
40
-------
average daily storm water load, which is 160% of the average daily
BOD load from the treatment plants in the City of Tulsa. This load
generally would reach the receiving stream in less than twenty-four
houi s. Such a loading of seven times the average daily load will occur
on the average 52 times per year. This consideration points out the
fact that any treatment facility being utilized for storm water pollution
control in the City of Tulsa will be in operation only approximately 52
day per year, and the effluent from such a facility on these days will
be 160% of the effluent from the sanitary sewage treatment plants.
When considered in the true context, the values of the pollution multipliers
used in this section were based on a limited amount of information. The
limitations emerge since the analysis was performed on a minute fraction
of the flow volume taken over an infinitesimal portion of the time span
in which the flow was occurring. Whether the samples were a represen-
tative mix of the multitudinous factors which contributed to the flow and
pollution is unknown. It is speculation also as to whether the combined
effects of these factors are reporduced over time. What is needed now
is either a detailed and concentrated study on an individual urban site
to thoroughly delineate the occurrence, nature, and concentration of
pollutants in the storm flow so that a sound rational exists for current
sampling procedures or new, versatile sampling techniques and pro-
cedures which better quantify the amounts of runoff and entrained
pollutants encountered in urban situations.
At present, when compared to the ranges of concentration in the pollu-
tion parameters found in the effluents of the municipal treatment plants,
the levels of pollution from storm water runoff found in the study samples
are in themselves no cause for alarm except with the possible exception
of the suspended solids concentrations. In newly developing areas the
magnitude of the sediment loads may cause concern. In developed areas,
however, the urban sediment load may be less than that found in rural
watercourses.
The problem which emerges is the magnitude of the total pollutional
loads which issue from an urban area. The estimates of pollution pre-
sented in this section are therefore presented as valid indicators of the
pollutional loads which are generated annually on each of the study sites.
The continued development of a metropolitan area such as Tulsa, and
the unceasing aggregations of the pollutional loads into the drainage ways
of the area point up the continued decline of a portion of the regional
environment and the emergency of a problem which at present defies
solution in a reasonable manner.
41
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FINDINGS
1. By a study of 15 test areas of representative land use and environ-
mental conditions, the average total coliform, fecal coliform, and
fecal streptococcus densities were determined to vary respectively from
5, 000 to 400, 000 numbers/100 ml, from 10 to 18, 000 numbers/100 ml,
and from 700 to 30, 000 numbers/100 ml.
2. The ranges of the average BOD, COD, and TOG concentrations
from the 15 test areas were, respectively: 8 to 18 mg/1, 42 to 138 mg/1,
and 15 to 48 mg/1. The organic pollution parameter ratios (BOD/COD
and TOG/COD) and certain individual observations indicate that some
organic material of storm water runoff does not show up in the standard
COD test. The organic material may, therefore, include straight-chain
aliphatic components, aromatic hydrocarbons, and pyridine. These
components are not oxidized to any appreciable extent in the COD test.
3. The organic Kjeldahl nitrogen averages from the 15 test areas
varied from 0. 39 mg/1 to 1. 48 mg/1. The two highest averages were
from residential areas of low population densities and good environmental
conditions.
4. The soluble orthophosphate averages varied from 0. 67 mg/1 to 3. 49
mg/1. The highest average value was found from a developing light
industrial area containing large amounts of disturbed land. Located in
the test area was a concrete batch plant which contributed to the source
of phosphates.
5. The average total solids concentration for each of the fifteen test
areas ranged from 199 mg/1 to 2242 mg/1. The highest average value
was eight to nine times greater than the average of the other 14 test
areas and was a result of exposed loose subsoil from a portion of the
test area that was being developed. The suspended solids concentrations
averaged approximately 50% of the total solids and were ten to twenty
times higher than the concentrations reported for the City of Tulsa's
sewage treatment plants.
6. The average pH (8. 4) from Test Area No. 1 approached the State
of Oklahoma's Water Quality Criteria, and several samples exceeded the
standard. The maximum recorded value from Test Area No. 1 was
12. 2.
7. The average chloride (Cl) concentrations from the 15 test areas in
Tulsa, Oklahoma were extremely low (2-46 mg/1) and can be con-
sidered to be of no consequence.
8. The calculated average yearly storm water pollution loads from the
fifteen areas varied as follows:
42
-------
Pollution Range in pounds/acre/year
Parameter Low High
BOD 12 ~48~
COD 60 470
Organic Kjeldahl Nitrogen Q. 8 3.6
Soluble Orthophosphate 1.1 8
Total Solids 470 5100
9. The calculated average daily loads per mile of street by land use
were found to be:
Pollution Range in pounds/day/mile of street
Parameter Residential Commercial Industrial
BOD 2To 2. 3 3.5
COD 14 18 28
Organic Kjeldahl Nitrogen 0. 14 0. 24 0. 26
Soluble Orthophosphate 0.18 0.21 0.21
Total Solids 54 87 112
10. From the foregoing, it is evidently possible to estimate and pre-
dict for planning purposes storm water pollution to be expected in
surface runoff from an urban area by assessment of land activity,
meteorological and hydrological conditions. This will provide a very
useful procedure for planning urban storm water systems and water
quality management.
43
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RE COMMENDATIONS
The recommendations presented below are based on the findings of the
study and are applicable to all urban areas with separate storm drainage
systems. Remedial measures and research of the nature proposed
herein would reduce storm water pollution from urban areas.
Three approaches to abatement and control of the dispersed pollution
load appear to be the most promising. These are: a reduction in total
runoff, a reduction in the rates of runoff, and environmental policy.
1. It is recommended that structural measures be implemented
to affect control within the first two areas. Examples of this
type of control would be (1) devices or schemes that would
eliminate or deplete runoff from rooftops, parking areas, and
streets and (2) implementation of upstream retention programs
for blue-green open space areas within the urban complex.
2. It is recommended that environmental controls be invoked
through the enactment of:
a. Regulations and enforcement procedures to control
urban litter and general sanitary conditions of public
and private areas.
b. Performance standards in subdivision regulations for
builders and contractors in reference to (1) exposing
soil, (2) parcel "housekeeping" measures during and
after construction, and (3) drainage practices during
construction periods.
c. Open storage regulations for commercial and indus-
trial areas.
d. Improved street cleaning and drainage channel main-
tenance practices with the primary intent of storm water
pollution control rather than aesthetics or flood control.
44
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ACKNOWLEDGEMENTS
The authors wish to express their appreciation to the Tulsa Metropolitan
Area Planning Commission for assistance in locating the discrete test
areas, furnishing Land Use Maps, and programming the land use com-
puter retrieval; the City of Tulsa Engineering Department for furnishing
official City Maps, use of precipitation records, and use of City property
for locating the sampling equipment; and the Tulsa City-County Health
Department for use of their environmental survey data.
The authors wish to acknowledge with grateful appreciation the very
important original efforts of Professor George W. Reid and his
experimentation at the University of Oklahoma for the helpful conceptual
inputs to this research effort.
The authors also wish to thank Mr. Charles Johnston for his efforts
throughout the sampling and laboratory analyses period of the study.
Appreciation and a special thanks is due Mr. Gary Miessler for his
assistance in the preparation of this paper.
The typing of the final manuscript by Mrs. Norma Whitworth is
gratefully acknowledged.
This paper, for the most part, was based on two previous papers which
were presented at the ASCE Annual and Environmental Meeting in
Chicago on October 14, 1979 and the 52nd Texas Water Utilities
Associations' Short School, College Station, Texas, March 2, 1970.
The authors and title of these papers respectively are:
"Storm Water Pollution from Urban Land Activity, "
by Jerry G. Cleveland, George W. Reid and Paul R.
Walters.
"Storm Water Pollution from Urban Land Activity",
by Jerry G. Cleveland and Ralph H. Ramsey.
Additional information was taken from the draft copy of final report
which was prepared by AVCO Economic Systems Corporation under
Contract No. 14-12-187 with the Federal Water Pollution Control
Administration, Department of Interior.
45
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REFERENCES
1. Waldrap, Reuel H. , "Community Block Survey and Socioeconomic
Stratification. " U. S. Department of Health, Education, and
Welfare, Public Health Service, Bureau of Disease Preven-
tion and Environmental Control, Atlanta, Georgia.
2. Geldreich, E. E. , Best, L. C., Keener, B. A., and Van Donsel,
D. J. , "The Bacteriological Aspects of Storm Water
Pollution. " Prepublication Copy, U. S. Department of
Health, Education, and Welfare, National Center for Urban
and Industrial Health, Cincinnati, Ohio, 1968.
3. Allison, F. E. , "Nitrogen and Soil Fertility. " Soil, The 1957
yearbook of Agriculture. Washington,D. C. : Government
Printing Office, 1957.
4. Burm, R. J. , Krawczyk, Do R. , and Harlow, G. L. , "Chemical
and Physical Comparison of Combined and Separate Sewer
Discharges. " Journal Water Pollution Control Federation,
Vol. 40, No. 1 (January, 1968), pp. 112-126.
46
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APPENDIX
From the analytical observations and the tabulated independent
variables, multiple regression equations were developed to pro-
vide predictor models for estimating urban pollutant concentrations.
In general, the models are not statistically significant, but they do
provide a technique of estimating a possible range of values. It
must be remembered that these equations were developed from data
collected from drainage basins located in Tulsa, Oklahoma. In all
likelihood they will not apply to all urban areas, especially in
metropolitan drainage sheds which have a high degree of different
land use types, environmental conditions, and drainage characteristics.
Table 14 presents a selection of the best equations by three catagories.
These Catagories are: residential, commercial and industrial, and
mixed. The residential models were based on the seven residential
test areas. The commercial and industrial equations were based on
the test areas which had a high percentage of this kind of activity.
The test areas included in this analysis were Nos. 2, 4, 6, 10, and 11.
The "mixed" regression equations were developed using all test areas
except 12 and 14 which were considered as being non-typical urban
uses. These equations can only be used successfully within the frame
of reference of their development and with logical judgment of their
accuracy.
Calculations with these equations using the minimum and maximum
values of the observed independent variables are presented after Table
14. This is done to show the predictable range of pollutant concentrations
obtained with use of the developed regression equation within the bounds
of the test data. The minimum and maximum values obtained during
the test are shown for comparison. Included also are examples showing
the use of the equations with data from individual test areas.
47
-------
TABLE 14--Continued
GO
Q
W
X
Pollution
Category
Bacterial
Organic
Nutrient
Solids
Inputs
Environmental Index (X^)
Dimensionless
Covered Sewer/Total Length (X2Q)
Ratio
Form Factor (Dg)
Dimensionless
Environmental Index (Xi)
Dimensionless
% Arterial Streets (X2i)
%
Length of Main Stream (02)
Feet
Residential Density (Xjy)
People/Res. Acre
Covered Sewer/Total Length
Ratio
Average Land Slope
Covered Sewer/Total Length (X2Q)
Ratio
% Other Streets (X22)
%
Fall of Drainage Area (04)
Feet
Outputs
Total Coliform
(1000/100 ml)
COD (mg/1)
Organic Kjeldahl
Nitrogen (mg/1)
Equation
565-420 (X, )-49. 3 (X2Q)
-6.70 (D)
R'
.78
:70.8-45.4 (XL) .70
+2.61 (X21) +0.0062 (D2)
= 0. 23-0. (X17)-0. 029 (X2Q) .79
+0. 256 (D6)
Total Solids
(mg/1)
Mg=130+8.99 (X20) +2. 59 (X22) .48
+2.06 (D4)
-'-Coefficient of determination
-------
TABLE 14
SELECTION OF BEST MULTIPLE
REGRESSION EQUATIONS
H
Z
W
Q
»—i
w
W
Pollution
Category
Bacterial
Organic
Nutrient
Solids
Inputs
Environmental Index (Xj)
Dimensionless
Covered Sewer /Total Length (X20)
Ratio
Form Factor (Dg)
Dimensionless
Environmental Index (Xj)
Dimens ionle s B
% Arterial Streets (X2i)
%
Length of Main Stream (D2)
Feet
Residential Density
People/Res. Acre
Covered Sewer/ Total Length (X2Q)
Ratio
Average Land Slope
Covered Sewer/Total Length
Ratio
% Other Streets (X22)
%
Fall of Drainage Area (04)
Feet
Outputs
Total Coliforrn
(1000/100 ml.)
Equation
M.=269-309
4-0.580 (D9)
(X2Q)
COD (mg/1.) M5=69-74. 7 (X, )+3. 68 (X21)
+0.0105 (D2)
R2*
.84
.94
Organic Kjeldahl M? = 0. 02-0. 0072 (XJ7) .79
Nitrogen (mg/1) +0. 200 (X20) +0. 286 (D6)
Total Solids
(mg/1)
M9= -139-15.37 (X20) .59
+ 15.98 (X22) +2.57 (D4)
* Coefficient of determination
-------
TABLE 14--Continued
ij oi
U H
Pollution
Category
Bacterial
Organic
Nutrient
Solids
Inputs
Environmental Index (Xj)
Dimensionless
Main Covered Storm Sewer
Miles
Form Factor (Dg)
Dimensionless
Environmental Index (Xj)
Dimensionless
Main Covered Storm Sewer
Miles
Length to Center of Area
Feet
Environmental Index (X^)
Dimensionless
Covered Sewer/Total Length
Ratio
Average Land Slope
Environmental Index (Xj)
Dimensionless
% Unused Space
Fall of Drainage Area
Feet
CXatputs
Total Coliform
(1000/100 ml.)
TOC (mg/1)
Organic Kjeldahl
Nitrogen (mg/1)
Total Solids
(mg/1)
Equation
R2*
= 119-384 (X^-19.5 (X19) .90
-13.4 (D9)
M6=3.8+4. 76 (XL) +2. 10 (X19) .94
+0.0055 (D3)
= 0. 31-0.0810 (X1) .92
-0.0507 (X2Q) +0.265
M9=1426-715 (Xj) +83. 0'(X29) .78
-7.43 (D4)
-^Coefficient of determination
-------
Example Problems
!„ Total Coliform
The multiple regression equation for Total Coliform (mixed use)
is:
= 565-420 (Xx) -49. 3 (X20) -6. 70 (Dg) Std. Error of Est. =70. 2
For an area with good environment (X^ = EI=1. 00), this equation
reduces to:
49.3 (X20) -6.70 (Dq)
The ranges of values for X2Q and Dg are:
Symbol Min. Max. Item
X20: 0.61 - 3.78 Covered Sewer/Total Length
Dg : 0. 82 - 2. 85 Form Factor
At maximum values for X2Q and Dg> MJ becomes negative:
M1 = 145-49. 3 (3. 78) -6. 70 (2. 85) = -60
Since most values for X2Q are somewhat smaller than the maxi-
mum, however, a negative calculated value for Mj_ would probably
be quite unusual.
For a bad environment (EI=0), the regression equation would be:
M1 = 565-49. 3 (X20) -6. 70
Using minimum values for X2Q and D9> tne maximum concentration
would be:
(This compares with the highest value from the 15 test
areas of 400. )
51
-------
For Test Area 9, for example:
M1 = 565-420 (0.23) -49.3 (1.59) -6.70 (1.47) = 380, which com-
pares favorably with the actual value of 400.
2. COD
The COD equation (mixed use) is:
M5=70. 8-45. 4 (XL) + 2.61 (X21) + 0. 0062 (D2) Std. Error of
Est. = 20. 7
For EI=1. 00 (good environment):
= 25. 4 + 2. 61 (X2i) + 0. 0062 (D2)
For EI=0 (bad environment):
= 70. 8 + 2. 61 (X21) + 0. 0062 (D2)
The ranges of values for X2i and D2 are:
Symbol Min. Max. Item
X21 0 18.93 % Arterial Streets
D2 2170 11, 200 Length of Main Stream
For EI=1.00:
The minimum COD would be:
M5=25. 4 + 0. 0062 (2170) = 38. 9 (minimum from test sites
studied: 42)
For EI=0:
The maximum COD would be:
M5=70.8 + 2.61 (18.93)+ 0.0062 (11200) = 189.6 (maximum
from test sites studied: 138)
52
-------
For residential areas, the multiple regression equation is:
M5= 69-74.7 (Xj) + 3.68 (X21) + 0.0105 (D2) Std. Error
of Est. =1Z.6
Minimum possible from data describing test areas studied:
M5=69-74. 7 (1. 00) + 0. 0105 (2170) = 17
Maximum possible from same data (and with EI=0):
M5=69 + 3.68 (18.93) +0.0105 (11200) = 256
For Site 12;
M5=70. 8 -45. 4 (1) + 2. 61 (3. 94) + 0. 0062 (5710) = 60. 8 (actual
value: 45)
For Site 5, a residential test area:
Mixed Use Equation:
M =70.8-45.4 (0.99) +2.61 (3.94) + 0.0062 (11200) = 106
Residential Use Equation:
M5-69 - 74.7 (0.99) +3.68 (3.94) + 0.0105 (11200) = 127
Actual value: 138
One can conclude that this equation can be a useful predictor, even
near the limits of some of the independent variables.
3. Organic KjeldahL Nitrogen
The regression equation (mixed use) is:
M7 = 0. 23-0 (X17) -0. 029 (X20) + 0. 256 (D6) (Independent of X1?)
Std. Error of Est. =0. 178
53
-------
The ranges of values for X2Q and D^ are:
Symbol Min. Max. Item
X2Q 0.61 3.78 Covered Sewer/ Total Length
D/- 0. 75 4. 60 % Land Slope (At D^O, the land
slope would be at a minimum)
For D£ =0, the equation would be:
M7=0. 23-0. 029 (X2o)
The minimum value from this equation (at X2Q = 3. 78) would be:
M = 0. 23-0. 029 (3. 78) = 0. 12
If there were no covered sewers (X^Q-O), on the other hand, the
nitrogen concentration would depend only upon the land slope:
M? = 0.23 + 0.256 (D6)
For a 4.6% land slope (maximum of test areas studied):
M7=0. 23 + 0. 256 (4. 6) = 1. 41
For Test Area 6:
M- = 0. 23-0. 029 (3.78) + 0.256 (2. 19) = 0.68 actual value: 0.65
For Test Area 13:
M? = 0. 23-0. 029 (0. 55) +0. 256 (4. 60) = 1. 39 actual value: 1. 46
For mixed land use, this regresssion equation was one of the most
accurate ones obtained.
4. Suspended Solids
For commercial and industrial areas:
54
-------
M12=1392-746 (X^ + 83. 1 (X29) -8. 37 (D4)
The ranges of values for the independent variables are:
Symbol Min. Max. Item
Xj 0 1.00 El (could be <0)
XZQ 0 24.77 % Unused Space
D 30 186 Fall of drainage Area
Using these limits, the minimum value for suspended solids
would be:
M12=1392-746 (1.00) +83.1 (0) -8.37 (186) = -911
The maximum would be:
M12=1392-746 (0) + 83. 1 (24. 77) -8. 37 (30) = 3199 (maximum
of test areas studied: 2052)
For Site 1:
M12=1392-746 (1. 00) +83. 1 (24. 77) -8. 37 (113) = 1758
(actual value: 2052)
For Site 12:
M12=1392-746 (1. 00) + 83. 1 (0) -8. 37 (58) = 161 (actual value:
89)
This general equation does not appear to be as useful in extreme
cases as some of the other equations for different parameters.
55
-------
SECTION 2
ROTARY VIBRATORY FINE SCREENING
OF
COMBINED SEWER OVERFLOWS
Primary Treatment of Storm Water Overflow
from Combined Sewers by High-Rate,
Fine-Mesh Screens
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
DEPARTMENT OF THE INTERIOR
CONTRACT 14-12-128
by
Donald M. Marske, Sanitary Engineer
Cornell, Rowland, Hayes & Merryfield
Engineers-Planners-Economists
Corvallis, Oregon 97330
Research and Development Program No. 11023 FDD
March 1970
57
-------
ABSTRACT
The objective of this study was to determine the feasibility, effectiveness, and
economics of employing high-rate, fine-mesh screening for primary treatment of storm
water overflow from combined sewer systems.
The final form of the screening unit stands 63 inches high and has an outside
diameter of 80 inches. The unit is fed by an 8-inch pipe carrying 1700 gpm (122
^
gal/min/ft ) which is distributed to a 60-inch diameter rotating (60 rpm) stainless steel
collar screen having 14 square feet of available screen area and a 165 mesh (105 micron
opening, 47.1 percent open area). The screen is backwashed at the rate of 0.235 gallons
of backwash water per 1000 gallons of applied sewage.
Based on final performance tests run on dry-weather sewage, the unit is capable of
99 percent removal of floatable and settleable solids, 34 percent removal of total
suspended solids and 27 percent removal of COD. The screened effluent is typically 92
percent of the influent flow.
On the basis of a scale-up design of a 25 mgd screening facility, the estimated cost
of treatment is 22 cents/1000 gallons. No finite cost comparisons were made with other
treatment methods; however, when compared to conventional primary sedimentation, the
selection of a screening facility as a treatment method is dependent on the value and
availability of land, the design capacity of the treatment facility, the character of rainfall
and runoff, and the available means of disinfection. It was observed that the proposed
screening facility required 1/10 to 1/20 the land required by a conventional primary
treatment plant.
This report was submitted in fulfillment of Contract No. 14-12-128 between the
Federal Water Pollution Control Administration and Cornell, Howland, Hayes and
Merry field.
59
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INTRODUCTION
NATIONAL IMPORTANCE OF STORM WATER OVERFLOWS
The majority of the existing combined sewers throughout the nation do not have
adequate capacity during heavy storm periods to transport all waste and storm-caused
combined flows to a treatment facility. The overflow is bypassed to a receiving stream,
thus causing pollution in the nation's watercourses.
Combined sewers are designed to receive all types of waste flows, including storm
water. In determining the size of the combined sewer, it has been common engineering
practice to provide capacity for 3 to 5 times the dry-weather flow. During intensive
storm periods, however, the storm-caused combined flow may be 2 to 100 times the
dry-weather flow, making overflow conditions unavoidable. To compound the problem,
most treatment facilities are not designed to handle the hydraulic load of the combined
sewer and, therefore, are required to bypass a portion of the storm-caused combined flow
to protect the treatment facility and treatment process from damage. The nation's
treatment facilities bypass flows an estimated 350 hours during the year, or about 4
percent of the total operation time. The pollutional impact of the storm-caused combined
overflow on the waters of the nation has been estimated as equivalent to as much as 160
percent the strength of domestic sewage biochemical oxygen demand (BOD). This
amount creates a major source of pollution for the nation's watercourses.
The cost to physically separate the storm water from the sanitary wastes through the
use of separate conduits has been estimated to be $48 billion. The development of an
alternative means of treatment could conceivably reduce this cost to one-third A '
OBJECTIVE
The objective of this study is to determine the feasibility, effectiveness, and
economics of employing high-rate, fine-mesh screens for primary treatment of storm
water overflow from combined sewer systems. Prior to actual testing of the screening
unit, several specific work goals were established to meet the objective. During the course
of the investigation, it became apparent that some of these could not be fully met. As a
result, these goals were ammended to fit the limitations of the testing facility. The
specific work goals which were not met, and the changes made, are discussed in the text.
61
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DEMONSTRATION PROCEDURE
SITE DESCRIPTION
The screening facility is located adjacent to the Sullivan Gulch pump station in
Portland, Oregon. The Sullivan station serves a drainage basin of about 25,000 acres of
Portland's metropolitan area, from which it pumps up to 53 million gallons a day (mgd).
The drainage basin is a residential area, with about 30,000 single-family residences within
its boundaries. A broad spectrum of services are available within the basin to support the
population. However, the automobile related services are the most heavily represented in
the drainage basin. This became visually apparent when periodic dumps of waste oil
appeared at the screening facility.
PILOT PLANT OPERATION
GENERAL LAYOUT-Figure 1 illustrates the general layout of the screening facility
and its relation to the Sullivan pump station. The combined sewage flow comes to the
station in a 72-inch horseshoe trunk sewer. Before reaching the pump station, a portion
of the flow is diverted to a bypass channel where it passes through a coarse bar screen
prior to reaching the screening facility's feed pump sump. This diverted flow, which is
now defined as combined sewage overflow, is lifted to the screening units by two 2100
gallon per minute (gpm) vertical turbine pumps. After passing through the screening
units, the treated effluent and solids concentrate, or untreated effluent, are both returned
to the trunk sewer. In an actual installation, the treated effluent will be bypassed to the
receiving stream, and only the solids concentrate will be returned to the interceptor.
DESCRIPTION OF SCREENING EQUIPMENT-A perspective view of a single
screening unit, as it existed in its original form, is shown on Figure 2. The unit is fed
through the influent line with the feed changing direction from vertical to horizontal over
the stationary distribution dome. The flow over the dome is ideally laminar. Upon leaving
the dome, the flow strikes the rotating collar screen at a velocity of 5 to 15 feet per
second, depending on the diameter of the influent line and the flow. The speed of the
collar screen can be varied between 30 and 60 rpm by adjusting a variable drive unit at
the 1/2 horsepower drive motor. Depending on the velocity of the feed, and the fineness,
condition, and speed of the collar screen, approximately 70 to 90 percent of the feed
will penetrate the screen. The remaining 10 to 30 percent, with the retained solids, drops
onto the vibrating horizontal screen for further dewatering. The dewatered solids, through
the vibrating action of the horizontal screen, migrate toward the center of the screen
where they drop through an opening in the screen to a solids discharge pipe. This solids
flow is returned to the interceptor sewer and subsequently to a sewage treatment plant.
The screened flow is discharged to a receiving water body as treated effluent.
62
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SCREENING
FACILITY
ULIIIVAN GULCH
PUMP STATION
FIGURE 1
EXPERIMENTAL PILOT PLANT
SULLIVAN GULCH PUMP STATION
PORTLAND, OREGON
-------
CONTINUOUS
DETERGENT BACKWASH
VARIABLE DRIVE
COLLAR SCREEN MOTOR
STATIONARY
DISTRIBUTION DOME
9 FOOT DIAMETER
ROTATINS COLLAR
SCREEN 10ACRON CLOTH)
VIBRATING HORIZONTAL
SCREEN
ROTATINS HORIZONTAL-
SCREEN BACKWASH SPRAT
OUTER SHELL
(«'-«' OU X
7-0* MSH)
JHSCREENED EFFLUENT
RETURNED TO TRUNK SEWER
SCREENED EFFLUENT
BYPASSED TO RECEIVING
WATER AFTER DISINFECTION
COLLAR SCREEN DETERGENT
BACKWASH SPRAY
FIGURE 2
ORIGINAL SCREENING UNIT
•:-
-------
ASSOCIATED EQUIPMENT-The screens are continuously cleaned with a solution of
hot water and concentrated household detergent. The wash water is heated to
approximately 170 degrees F. with a gas-fired, commercial water heater. The detergent is
injected into the hot water piping by a 10 gpm positive displacement pump. The
detergent is diluted about 800:1 at the spray nozzles, and is discharged at a rate of 1.8
gpm per nozzle at a pressure of 50 pounds per square inch (psi). The collar screen has
two stationary nozzles directed at the outside of the screen, and the horizontal screen has
four nozzles mounted on a rotating bar directed at the underside of the screen.
OPERATION OF SCREENING FACILITY-A specific goal of this study was to
perform all test runs during storm-caused combined sewage conditions. However, after
approximately one-third of the testing was accomplished, the rainy season came to an
end and the project was faced with a possible delay. To avoid this possible one-year
delay, it was decided to complete the study using dry-weather flow. In making this
decision, it was assumed that the differences between dry-weather flow and storm-caused
flow were not great enough to affect the objective of this study.
SAMPLING TECHNIQUE AND FREQUENCY-When the screening operation began,
it was observed that the character of the waste frequently changed in concentration and
color over very short periods of time. This was expected, and it was a specific goal to
detect and characterize these changes with a grab sampling technique. During the course
of the investigation, however, it became desirable to minimize the very short-term
interferences associated with the variability of the sewage so that the long-term
performance of the unit could be evaluated. To do this required composite sampling.
During the testing program, the duration of any one test ranged from a minimum of
one hour to a maximum of twelve hours. In most tests, composite samples were collected
every hour, with each composite consisting of three grab samples of equal volume
collected in the middle of each one-third of that hour. The flow rate to the unit during
any one test was constant. It was this type of composite sampling that was used to
evaluate the long-term effectiveness of the screening unit, and also to obtain a general
and representative description of the sewage being applied to the unit.
Grab sampling was used to describe the more unusual constituents of the sewage that
affected the short-term performance of the screening unit. These unusual constituents
and their affect on performance, were noted and are discussed in the text.
OBSERVATIONS-A schematic diagram of the screening facility, the process streams
sampled, and the observations made on each stream are shown on Figure 3.
65
-------
SULLI
PUMP
VAN GULCH
STATION
COMBINED SEWAGE
x.
COMBINED SEMAGE OVERFL01 INFLUENT
SOLIDS (TOTAL, VOLATILE,
SETTLEABLE)
B.O.D. , D.O., C.0.0.
pH, TEMPERATURE
CI2 DEMAND
MPN
NH4
FLOW RATE
SAMPLE POINT
INTERCEPTOR SEWER TO
SEWAGE TREATMENT PLANT
SCREENING UNIT
SCREENED SOLIDS CONCENTRATE
SOLIDS (TOTAL & VOLATILE)
B.O.D.
C.O.D.
FLOW RATE
WASH WATER
TEMPERATURE
pH
FLOW RATE
CONCENTRATION
OF DETERGENT
BYPASS TO RIVER
SCREEN EFFLUENT
SOLIDS (TOTAL, VOLATILE, SETTLEABLE)
B.O.D., D.O., C.O.D.
Cl2 DEMAND
MPN
FLOW RATE
WASH WATER EQUIPMENT
FIGURE 3
COMBINED SEWAGE OVERFLOW SCREENING
SAMPLING PROGRAM
-------
All laboratory tests were performed according to Standard Methods^"' with the
exception of COD. All samples, except settleable solids, were blended in a Waring blender
prior to analysis to improve the precision of the results. Settleable solids determinations
were made by the Imhoff cone procedure.
The COD test was performed according to the "rapid method" as described by Dr.
John S. Jeris in the May 1967 issue of "Water and Wastes Engineering." The rapid
method COD test made routine collection of organic strength data very reliable because it
minimized the possibility of loss of data, which may have been experienced if only the
5-day BOD test was performed.
During the initial stages of the testing program, parallel tests of BOD and COD were
performed on all process streams to establish a BOD/COD ratio for each stream. During
subsequent tests, only the rapid COD test was run and the BOD/COD ratio was used to
provide a BOD value when this appeared desirable.
EXPERIMENTAL DESIGN AND DATA REDUCTION
EXPERIMENTAL DESIGN-During startup of the screening unit, several variables
were noted in its construction and operation that would affect its performance. These
included influent flow rate, the velocity at which the feed strikes the collar screen;
rotational speed of the collar screen; mesh size and material of the collar and horizontal
screen; duration and frequency of the backwash; and type of detergent used in the
backwash. With this many variables, a means of experimentation was required that would
efficiently evaluate the relative influence each variable had on the overall performance of
the unit. This required an experimental procedure which could investigate several
variables simultaneously, and reveal what the exact effect of each variable was on the
performance of the unit.
To accomplish this, a form of factorial experimental design was used for each
investigation of the testing program. Figure 4 illustrates the initial experiment, which was
designed to investigate the three variables that, at the time, were believed to have the
most effect on performance. This experiment design is statistically termed a 2^ Factorial
Design, Multiple Response Experiment, which means that two levels of three variables are
simultaneously investigated. If all combinations are tested, the experiment requires eight
test runs. Under these particular set of conditions, the experiment can be visualized as a
cube in which each corner of the cube represents a unique combination of the variables
to be tested.
At the completion of the experiment, a cursory evaluation can be made by plotting
any one, or all, of the responses observed at their respective positions on the cube. In
most cases, the observer can immediately determine, by visual inspection, which of the
three variables is contributing the most and/or least to the particular response observed.
67
-------
SETTLEABLE SOLIDS REDUCTION ~N
EFFICIENCIES
86%
79%
EXPERIMENT NO.
62%
93%
RESPONSES
1. SETTLEABLE SOLIDS
REMOVAL
2. TSS REMOVAL
3. VSS REMOVAL
4. B.O.D. REMOVAL
5. DURATION OF TEST RUN
6. CONDITION OF SCREEN
7. SOLIDS CONTENT OF
SCREENINGS.
a. HYDRAULIC CAPACITY
EXP.
NO.
1
2
3
4
5
6
7
B
RUN*
NO.
5
3
7
8
2
4
1
6
COLLAR
SCREEN
175
110
175
110
175
110
175
110
HORIZONTAL
SCREEN
175
175
110
110
175
175
110
110
FLOW
(GPM)
700
700
700
700
1200
1200
1200
1200
'TEST RUNS ARE RANDOMIZED TO MINIMIZE
EFFECT OF A TIME TREND WHICH MAY EXIST
DURING TESTING PERIOD.
FIGURE 4
EXPERIMENTAL DESIGN AND DATA REDUCTION
-------
DATA REDUCTION-While in most cases a visual interpretation of the data is
sufficient during the early stages of an investigation, the limitations of the eye are soon
realized. A mathematical method is used to further inspect the data.
In reference to Figure 4, the effect that any one variable has on a particular response
is calculated by subtracting the average of the four observations at the lower level of the
variable from the average of the four observations at the higher level of the variable. For
example, the observed reductions in settleable solids of the first experiment are plotted at
their respective positions on the experimental diagram of Figure 4. The following
calculation was made to determine the effect that changing the horizontal screen from
175 (105 micron opening, 52 percent open area) to 110 mesh (150 micron opening, 42
percent open area) had on the efficiency of settleable solids reduction.
A fu-v, , 1/1 IA v^ 79 + 75 + 86 + 62 _ „,
Average ol higher level (110 mesh) = . - /o
A <-i , i/nc i^ 81+92 + 85+93 _ ttc
- Average of lower level (175 mesh) = -88
4
Effect = -12 percent
From this calculation, one can conclude that: "When the horizontal screen was
changed from 175 mesh (105 microns) to the coarser 110 mesh (150 microns), the
settleable solids reduction efficiency was decreased by 12 percent, from 88 percent to 76
percent."
Using the same calculation for the collar screen variable and influent flow rate
variable, the results of the first experiment for settleable solids reduction efficiencies can
be summarized as follows:
Effect On
Variable Settleable Solids Reduction
Changing horizontal screen from 175 to 110 Decreased 12 percent
Changing collar screen from 175 to 110 Decreased 2 percent
Changing flow rate from 700 gpm (50 gal/min/ft2)
to 1200 gpm (86 gal/min/ft-) None
From this summary, one can conclude that the size of the horizontal screen most
affects settleable solids removal, and the flow rate applied to the unit least affects
settleable solids removal. If the next experimental design was based on only these results,
a finer horizontal screen would be selected to obtain better results. Likewise, since
increasing the flow rate to 1200 gpm (86 gal/min/ft2) had little effect on the
performance, it would also be natural to try a higher flow rate, since this would increase
69
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the hydraulic capacity of the unit. This type of analysis and reasoning was applied
throughout the testing program; however, for any one experiment, several responses were
evaluated before a change was made in the variables. A review of all the evaluations,
collectively, provided most of the information necessary to evaluate the overall
performance of the unit and to modify the unit to improve its performance.
70
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INVESTIGATIONS
The chronology of the investigations, and the clarifying data, will be discussed in this
section. Information of a more analytical nature will be found in Appendix C.
CHARACTERIZATION OF COMBINED SEWAGE OVERFLOW-Several composite
samples were taken from the trunk sewer during storm periods for the purpose of
characterizing storm-caused combined sewage. A summary of results is presented in Table
1.
TREATMENT CAPABILITIES OF SCREENING UNIT-Several levels of the known
variables were tested. The results of these tests led to several equipment modifications in
the course of developing the screening unit as it now exists. A list of the known
variables, the range at which each was tested, and the level at which the best results
occurred are presented in Table 2. The evolution of the screening unit from its original
form to its present form is illustrated in Figure 5.
The major modifications included removing the vibrating horizontal screen, improving
the backwash procedures, selecting an effective detergent, changing the screen materials
and reducing the size of the influent pipe to increase the velocity of the feed striking the
screen.
71
-------
TABLE 1
SUMMARY OF CHARACTERIZATION OF COMBINED SEWAGE
SULLIVAN GULCH PUMP STATION
PORTLAND, OREGON
FEBRUARY - APRIL, 1969
CHARACTERISTIC
PH
TEMPERATURE, °F
DISSOLVED OXYGEN, MG/L
SETTLEABLE SOLIDS, ML/L
TOTAL SUSPENDED SOLIDS, MG/L
VOLATILE SUSPENDED SOLIDS, MG/L
% VOLATILE SUSPENDED SOLIDS
B.O.D., MG/L
C.O.D., MG/L
B.O.D./C.O.D.
AMMONIA NITROGEN, MG/L
ORGANIC NITROGEN, MG/L
TOTAL NITROGEN, MG/L
NUMBER OF
OBSERVATIONS
26
25
16
25
28
28
28
14
24
14
7
7
7
MEAN
5.0
48.7
8.0
3.1
146
90
67
105
199
.51
5.1
8.2
13.3
STANDARD
DEVIATION
+ .4
+ 6.5
+ 2.2
+ 1.0
+ 59
+ 25
+ 17
+ 36
+ 50
-I- .08
+ 1.4
+ 3.1
+ 4.3
MINIMUM
4.5
34.0
3.7
1.5
70
57
36
57
138
.35
3.7
5.10
9.5
MAXIMUM
6.0
56.0
10.4
5.0
325
166
93
155
324
.64
7.0
14.0
21.0
72
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TABLE 2
RANGE AND LEVEL OF VARIABLES TESTED
VARIABLE
RANGE INVESTIGATED
LEVEL OF BEST
PERFORMANCE
U>
HORIZONTAL SCREEN MESH SIZE
COLLAR SCREEN MESH SIZE
COLLAR SCREEN MATERIAL
COLLAR SCREEN ROTATIONAL SPEED
INFLUENT FLOW RATE
COLLAR SCREEN HYDRAULIC LOADING
VELOCITY OF FEED WATER STRIKING
COLLAR SCREEN
TYPE OF OPERATION
BACKWASH RATIO (GAL. BACKWASH
WATER/1000 GAL. APPLIED WASTE)
110 (150 MICRON OPENING)
TO 175 (105 MICRON OPENING)
105 (167 MICRON OPENING)
TO 230 ( 74 MICRON OPENING)
DACRON CLOTH, MARKET GRADE
STAINLESS STEEL FABRIC, TENSILE
BOLTING CLOTH.'1'
30 RPM TO 60 RPM
700 TO 2000 GPM
50 GAL/FT2/MIN. TO
143 GAL/FT2/MIN.
3 TO 12 FT/SEC.
INTERMITTENT TO CONTINUOUS
.200 GAL/1000 GAL.
TO 25.6 GAL/1000 GAL.
REMOVAL OF HORIZONTAL SCREEN
165 (105 MICRON OPENING,
47.1% OPEN AREA)
TENSILE BOLTING CLOTH
60 RPM
1700 GPM
122 GAL/FT2/MIN.
11 FT/SEC.
4% MIN. ON, % MIN.
OFF FOR BACKWASH
.235 GAL/1000 GAL.
(1) SEE APPENDIX A FOR SCREEN SPECIFICATIONS.
-------
CONTINUOUS
DETER8ENT BACK**!'
WATER
IWSCHEEKCD EFL«H
COLLAR SCREE* OETERSEr
•ACKWASM SPRAT
ORIGINAL FORM
OPERATING CONDITIONS:
INFLUENT FLOW RATE
COLLAR SCREEN SPEED
COLLAR SCREEN
HORIZONTAL SCREEN
BACKWASH RATIO
PERFORMANCE:
SETTLEABLE SOLIDS
REMOVAL
T.S.S. REMOVAL
C.O.D. REMOVAL
SCREENED EFFLUENT
AS % OF INFLUENT
50 TO 86 GPM/FT2
30 RPM
105 TO 150 MICRON
OPENING DACRON CLOTH
105 TO 150 MICRON
OPENING DACRON CLOTH
12.0 TO 20.6 GAL./1000 GAL.
62% TO 93%
10% TO 26%
5% TO 13%
99.99%
Figure 4
74
-------
UNtCKEENCO EFFLUENT
- COLLAR *CHEEK DETERSEHT
•ACKWAtH IPHAY
MODIFICATION 1
REMOVE HORIZONTAL SCREEN
OPERATING CONDITIONS:
INFLUENT FLOW RATE 50 TO 86 GPM/FT'
COLLAR SCREEN SPEED 30 TO 45 RPM
COLLAR SCREEN
105 TO 150
MICRON OPENING
DACRON CLOTH
3.0 TO 5.1 GAL/1000 GAL.
BACKWASH RATIO
PERFORMANCE:
SETTLEABLE SOLIDS
REMOVAL
T.S.S. REMOVAL
C.O.D. REMOVAL
SCREENED EFFLUENT
AS % OF INFLUENT 65% TO 81%
48% TO 90%
18% TO 25%
10% TO 18%
Figure 4 (cont.)
75
-------
DETERSCNT BACKWASH
MTU
LJMKRCENfD EFFLUCVT
"
10* INFLUENT PIPE
• . _.
MODIFICATION 2
DRY-WEATHER COMBINED SEWAGE FEED
STAINLESS STEEL COLLAR SCREEN
OPERATING CONDITIONS:
INFLUENT FLOW RATE
COLLAR SCREEN SPEED
COLLAR SCREEN
50 TO 86 GPM/FT2
30 TO 60 RPM
74 TO 105 MICRON OPENING
MARKET GRADE STAINLESS
STEEL FABRIC
BACKWASH RATIO
PERFORMANCE:
SETTLEABLE SOLIDS
REMOVAL
T.S.S. REMOVAL
C.O.D. REMOVAL
SCREENED EFFLUENT
AS%OF INFLUENT
3.0 TO 5.1 GAL/1000 GAL.
92% TO 100%
11% TO 34%
6% TO 13%
46% TO 74%
Figure 4 (cont.)
76
-------
MODIFICATION 3
MODIFIED DISTRIBUTION DOME
ADDITION OF BACK SPRAY
MODIFIED BACKWASH PROCEDURE
IMPROVED COLLAR SCREEN MATERIAL
OPERATING CONDITIONS:
INFLUENT FLOW RATE
COLLAR SCREEN SPEED
COLLAR SCREEN
BACKWASH RATIO
PERFORMANCE:
SETTLEABLE SOLIDS
REMOVAL
T.S.S. REMOVAL
SCREENED EFFLUENT
AS % OF INFLUENT
100 TO 114 GPM/FTZ
30 TO 60 RPM
167 MICRON OPENING
TENSILE BOLTING CLOTH
.50 TO .57 GAL/1000 GAL.
70%
7%
74% TO 80%
Figure 5
77
-------
0«CE*TR»TEO OETIMENT
»C««»SH *AT«
(10 StC 0*. 20 MIN OFF]
VARIABLE
COLLAR ffCNCEK MOTOR
MODIFIED
DISTRIBUTION DOME
RQTATIM COLLM
SCRUM tTemiLC
• OLTIIM CLOTHt
CONCCHTRATt IOVL
MODIFICATION 4
ADDITION OF CONCENTRATED DETERGENT
BACKWASH WATER
OPERATING CONDITIONS:
INFLUENT FLOW RATE
COLLAR SCREEN SPEED
COLLAR SCREEN
BACKWASH RATIO
PERFORMANCE:
SETTLEABLE SOLIDS
REMOVAL
SCREENED EFFLUENT
AS % OF INFLUENT
100 GPM/FT2
60RPM
167 MICRON OPENING
TENSILE BOLTING CLOTH
.25 GAL/1000 GAL.
90%
90%
Figure 5 (cont.)
DEVELOPMENT OF A HIGH-RATE
FINE-MESH SCREENING UNIT
78
-------
VAMIAILE OftlVE
COLLAR fCRCCN MOTOK
F1ED ITkTIOHAR
RIIUTION DOME
TlNt COLLAR
CM (TCHS1LE
UNSCHEEMED EFFL<
CONCENTRATE BO«L
FINAL FORM
ADDITION OF ORIFICE PLATE
MODIFIED BACKWASH PROCEDURE
OPERATING CONDITIONS:
INFLUENT FLOW RATE
COLLAR SCREEN SPEED
COLLAR SCREEN
BACKWASH RATIO
PERFORMANCE:
FLOATABLE SOLIDS
REMOVAL
SETTLEABLE SOLIDS
REMOVAL
T.S.S. REMOVAL
C.O.D. REMOVAL
SCREENED EFFLUENT
AS % OF INFLUENT
122 GPM/FT2
60 RPM
105 MICRON OPENING
TENSILE BOLTING CLOTH
.235 GAL/1000 GAL.
100%
98%
34%
27%
92%
Figure 5 (cont.)
79
-------
DISCUSSION OF RESULTS
CHARACTERIZATION OF COMBINED SEWAGE
A summary of the characterization of storm-caused combined sewage was presented
in Table 1. This characterization was based on the average of several composite samples
collected during the early stages of the test program. The composite samples consisted of
three grab samples collected over a one-hour period during a test run. Composite
sampling was used in lieu of discreet sampling to obtain a more representative description
of the sewage being applied to the screens over an extended period of operation. A
review of the characterization did not reveal any unusual constituents in the sewage that
could affect the long-term operation of the screening unit.
During this period of characterization, however, it was observed that there were
several unusual constituents in the sewage which markedly reduced the short-term
effectiveness of the screening unit. These include waste oil dumps, waste paint dumps,
and the cleanup wastes associated with a fish packing plant. All of these waste dumps
were of high concentration, low frequency and short duration, and significantly reduced
the hydraulic capacity of the screening unit by their presence. When these constituents
were encountered, grab samples were collected and analyzed.
The waste oil dump appeared about 3:00 p.m. every day and lasted for a period of
approximately five to ten minutes. The oil was present in sufficient concentration to turn
the sewage to a black color. The waste paint dumps were less frequent occurring only
once or twice a week about the same time of day. The duration of the paint's presence
was about the same as the oil and was also of sufficient concentration to change the
color of the sewage. In the case of the paint, it was either a brilliant red or green. Both
of these waste dumps also had a strong volatile odor associated with them.
The dump from the fish packing plant was observed a total of five times and each
time for a period of approximately 15 minutes. No color change was noticeable by its
presence. However, a strong odor of decayed fish made its presence known. The pH of
the sewage during this period was 8.5, considerably above the normal of 5.0.
In each of these waste dumps, the hydraulic capacity of the screening unit was
significantly reduced through grease-blinding of the collar screen. If the screens were not
backwashed during this period, the hydraulic capacity was reduced to a point where only
40 percent of the feed would pass through the screen, down from the normal 80 to 90
percent passing the screen. After the waste dump would pass, the screens would not
recover until they were backwashed. When the screens were backwashed during the waste
dump flows, the reduction in hydraulic capacity was minor.
80
-------
As previously discussed, it became necessary to complete a major portion of the
testing with dry-weather sewage for the lack of storm-caused combined sewage. The
dry-weather sewage was characterized in the same manner as the storm-caused combined
sewage. A comparison of the two sets of data are included in Table 3. For all practical
purposes, the two wastes are similar in character with regard to the affect they have on
the long-term performance of the screening unit. The short-term reductions in hydraulic
capacity, however, were more severe under dry-weather sewage conditions than under
wet-weather sewage conditions.
TREATMENT CAPABILITIES OF SCREENING UNIT
The performance of the screening unit is ultimately evaluated by its ability to remove
organic material from a wastewater stream, and by the volume of wastewater that it can
process. These performance parameters are directly dependent on variables within the
screening unit. The mesh size of the screen, the strength of the screen, the velocity at
which the feed strikes the screen, and the backwash operation are among the most
important variables. The final experiment, which was designed with these variables in
mind, clearly defined the capabilities and limitations of the screening unit.
The final experiment consisted of six 3-hour tests. Each was performed on a different
day. Four of the six tests investigated two levels of influent flow rate and screen-mesh
size. The remaining two tests were duplicated at the intermediate levels to obtain an
estimate of the day-to-day variances in operating the unit and in the character of the feed
water. The tests at the intermediate levels also helped to interpret the final results. The
design of the final experiment and the observations during the experiment are presented
on Figure 6.
An examination of all the observations reveals that each response is dependent on
both the flow rate and the mesh size of the screen. No response is completely
independent of either flow rate or mesh size: however, the unit's efficiency in removing
organic material is more dependent on the screen-mesh size than on the flow rate. The
dependency of removal efficiency on screen-mesh size was expected. If a finer screen is
installed on the unit, one could expect higher removal efficiencies. Other variables,
however, tend to bias this dependency. In most instances, as the flow rate was increased,
slightly poorer removal efficiencies were observed. It is believed the higher flow rates are
fracturing the more friable solids at the surface of the screen and forcing them through
the screen. The slight reduction in removal efficiency observed at the higher flow rate,
however, is more than offset by the increase in hydraulic efficiency.
The hydraulic efficiency, as measured by the percentage of screened effluent and the
condition of the screen, also shows a very strong interdependence on flow rate and
screen-mesh size. As seen on Figure 6, the best hydraulic efficiency and most stable
performance occurs at the higher flow and coarser screen condition. The hydraulic
81
-------
EXPERIMENTAL DESIGN
93%
230 (74 MICRONS)
o —
10 in
tc. I
O
o
165 (105 MICRONS)
105 (167 MICRONS)
©
©
86 114 143
INFLUENT FLOW RATE
(GPM/FT2)
OBSERVATIONS
100% 41% 35% 31.3%
27.5%
99%; 98%
28%; 24.5%
21%; 23.4%
92% 89%
SETTLEABLE SOLIDS REMOVAL
31%
32%
26.5%
19.6%
TOTAL SUSPENDED
SOLIDS REMOVAL
79.1%
89.8% GOOD
C.O.D. REMOVAL
FAILED.REPLACED
.AND FAILED AGAIN
87.1%
91.1; 92.8
92.5% GOOD
GOOD; FAILED, REPLACED
AND SURVIVED
I GOOD
SCREENED EFFLUENT
AS % OF INFLUENT
CONDITION OF SCREEN AT
END OF FOUR-HOUR TEST RUN
FIGURE 6
EXPERIMENTAL DESIGN AND OBSERVATIONS
OF FINAL EXPERIMENT
81 A
-------
TABLE 3
COMPARISON OF STORM - CAUSED COMBINED FLOW
AND
DRY-WEATHER FLOW
CHARACTERISTIC
SETTLEABLE SOLIDS.
ML/L
TOTAL SUSPENDED
SOLIDS, MG/L
C.O.D., MG/L
STORM-CAUSED COMBINED FLOW
NUMBER
OF
OBSERVATIONS
25
28
24
MEAN
3.1
146
199
STANDARD
DEVIATION
i 1.0
± 59
1 50
WIN.
1.5
70
138
MAX.
5.0
325
324
DRY-WEATHER FLOW
NUMBER
OF
OBSERVATIONS
35
35
25
MEAN
4.8
129
345
STANDARD
DEVIATION
± 1.1
± 44
± 138
MIN.
2.5
50
144
MAX.
7.0
244
696
00
-------
efficiency declines as both the flow rate decreases and the screen becomes finer. This is
illustrated more vividly on Figure 7, where the actual flow recorder charts are displayed
at their respective positions on the experimental design. The graphs were generated
continuously by a four-hour flow recorder that pneumatically sensed the head over a
90-degree V-notch weir. The screened effluent flow and the unscreened flow were
recorded simultaneously. The total influent flow was found by summation. The graphs
are discontinuous because the screening unit was shut off for the backwash cycle.
For this final series of tests, the screening unit was operating 4-1/2 minutes on and
1/2 minute off. During the 1/2 minute, the flow was shut off and the screens were
backwashed with an 800:1 dilution of hot water and liquid detergent. At the end of a
20-minute cycle, the flow was shut off, and the screens were backwashed with a 10:1
dilution of water and liquid detergent. The distinction between the two backwash cycles
is easily seen on the flow charts. Frequent backwashing is necessary, as seen on the flow
charts, at the 1200 gpm (86 gal/min/ft2) flow level by the rapidly rising level of the
unscreened flow graph. This need for backwashing diminishes at the higher flow level,
and therefore the frequency of backwashing could have been reduced. Further
examination of the flow charts shows that the flow rate, or velocity of flow, to the
various screen-mesh sizes has a significant effect on hydraulic efficiency and performance
stability.
High velocities and flow rates are limited, however, by the strength of the screen.
Figure 6 shows that the 165 mesh screens (105 microns, 47.1 percent open area) started
failing at 1600 gpm (114 gal/min/ft2). Failure of the 230 mesh screen (74 microns, 46.0
open area) was persistent at 2000 gpm (143 gal/min/ft2). Screen life is also approximated
on Figure 7 by the relative length of chart run. The photographs on Figure 8 illustrate
typical screen failures.
The failure of the steel screens was attributed to the tremendous live load applied to
the screens during high-flow conditions. The forces contributing to the failure include the
velocity head of the flow striking the screen, the centrifugal forces associated with the
rotation of the screen, and the mass of water carried along on the inside of the screen.
By calculating the velocity head and G-force at 2000 gpm and 60 rpm, and assuming a
thickness of water on the inside of the collar screen, the equipment supplier found that
the steel wires of the screens were stressed beyond their yield point soon after the 2000
s-y
gpm (143 gal/min/ftz) was applied.
A failure of this kind was termed a mechanical failure, and the situation was
corrected to a degree in reducing the effective live load on the screen by reducing the
unsupported span of the screen. Recent developments in extending screen life by the
equipment supplier have produced a 165 mesh screen (105 micron opening) that now has
a probable life of 500 hours when operated at 1750 gpm (128 gal/min/ft^). If operated
at 2500 gpm (178 gal/min/ft2), the probable life will drop to 300 hours.
83
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74--
O
Z
I
u
Z
iu
105- -
O
U
167- •
SCREENED EFFLUENT FLOW LEVEL
SOLIDS CONCENTRATE FLOW LE
UN SCREE
PERCENT
RISING LEVEL OF UNSCREENED EFF
FLOW INDICATES THE SCREEN IS
INFLUENT FL<
7.7
H-
OPERATING CONDITIONS: 414 MINUTES ON, 14 MINUTE OFF
FOR NORMAL BACKWASH, AND
V4 MINUTE CONCENTRATED
DETERGENT BACKWASH EVERY
20 MINUTES.
INFLUENT F
84
-------
VEL
NORMAL BACKWASH
!TER NORMAL BACKWASH
/BEFORE DETERGENT BACKWASH
>FTER DETERGENT BACKWASH
•MED EFFLUENT FLOW AS A
AGE OF INFLUENT FLOW
1UENT
BLINDING
DW VELOCITY (FT. PER SEC.)
10.2
114
LOW RATE {GPM/FT2}
12.8
+
143
FIGURE 7
HYDRAULIC CAPACITY OF SCREENING UNIT
85
-------
AT LEFT AND BELOW:
165 MESH TBC AT 114 GPM/FT2.
FAILURE AFTER 6 HOURS
165 MESH TBC AT 122 GPM/FT2,
FAILURE AFTER 12 HOURS
SHOWN AT LEFT
165 MESH TBC AT 122 GPM/FT2,
FAILURE AFTER 6 HOURS
SHOWN AT RIGHT.
FIGURE 8
TYPICAL SCREEN FAILURES
86
-------
Based on the results of the last experiment, a final test was performed to gather data
on extended operation of the unit. The previous tests indicated that the unit operated
best at 1700 gpm (122 gal/min/ft2) on a 165 mesh screen (105 microns, 47.1 percent
open area). To further stabilize the performance, backwash operation was changed to a
30-second wash to 40:1 solution of water and liquid detergent at the end of 4-1/2
minutes of operation. The test lasted for six hours and ended with the failure of three
screens. A summary of the operating conditions, performance data, and character of flow
streams are presented in Table 4. An Imhoff cone comparison of the flow streams is
presented on Figure 9.
The results of the final test show that the unit's ability to remove organic material
from the wastewater stream is good, and is comparable to the efficiency of a primary
clarifier. The hydraulic efficiency of the unit is excellent; however, failure of the three
screens shows that the unit is operating beyond its capacity. The screen is the limiting
component of the entire unit.
87
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TABLE 4
SUMMARY OF EXTENDED TEST
OPERATING CONDITIONS
INFLUENT FLOW RATE - 1700 GPM
(122 GAL./MIN./FT.2}
COLLAR SCREEN SPEED - 60 RPM
COLLAR SCREEN - 165 MESH TBC
(105 MICRON OPENING,
47.1% OPEN AREA)
BACKWASH RATIO - .235 GAL/1000 GAL.
PERFORMANCE DATA
100% REMOVAL FLOATABLE SOLIDS
98% REMOVAL SETTLEABLE SOLIDS
34% REMOVAL TOTAL SUSPENDED SOLIDS
27% REMOVAL C.O.D.
8% OF INFLUENT AS A SOLIDS CONCENTRATE
RUN TERMINATED AT 6 HOURS DUE TO SCREEN
FAILURES.
AVERAGE CHARACTER OF FLOW STREAMS
INFLUENT
SCREENED
EFFLUENT
UNSCREENED
-)- EFFLUENT
oo
oo
FLOW (GAL./MIN.)
(% OF INFLUENT)
1700
100%
1570
92%
130
SETTLEABLE SOLIDS
(ML/L)
5.7
73
TOTAL SUSPENDED SOLIDS
(MG/L)
(POUNDS/MIN.)
122
1.73
87
1.14
542
0.59
C.O.D. *
(MG/L)
(POUNDS/MIN.)
302
4.30
240
3.15
1060
1.15
* B.O.D./C.O.D. =
0.5
-------
100% REMOVAL
OF FLOATABLE SOLIDS
SHOWN AT LEFT
SCREENED EFFLUENT AT LEFT;
AT CENTER SOLIDS CONCENTRATE
AND INFLUENT COMBINED SEWAGE
SHOWN AT RIGHT.
FIGURE 9
IMHOFF CONE COMPARISON
OF FLOW STREAMS
-------
PRELIMINARY DESIGN OF A SCREENING FACILITY
The final performance data of the screening unit shows that fine-mesh screening
could be used for treating combined sewage overflow; therefore, a preliminary design of a
full-scale facility was warranted.
DESIGN CRITERIA
The proposed project site is located in Seattle, Washington. The site is in the heart of
the business district of Seattle and is located within a valuable parking lot at the
intersection of King Street and the Alaskan Way viaduct. The entire area surrounding the
site is constructed on fill material, and almost every structure is supported on piling. The
site is also close to the waterfront of Elliott Bay; therefore, high tide comes to within a
few feet of the ground surface. Construction in this area is difficult and expensive.
The drainage basin above the site includes about 190 acres and is served by a
48-inch, pile-supported, concrete sewer. Since the drainage basin is almost entirely
pavement or building roofs, a runoff coefficient of .95 was assumed to determine storm
water volumes.
The rainfall pattern in the City of Seattle was studied to determine the design
capacity of the screening facility. The intensity and duration of rainfall in the area
received particular attention so that it could be estimated how long the facility would
operate at a certain capacity. The study revealed that measurable precipitation occurred
approximately 1,000 hours each year. While the rainfall occurrences were relatively
frequent, they were of low intensities. Rainfall intensities up to .055 inches/hour produce
a runoff of 10 mgd, and account for 75 percent of the rainfall occurrences. A summary
of this study is shown on Figure 10.
Runoff in excess of 2.75 mgd will produce combined sewage overflow. This flow is
based on the capacity that the dry-weather flow of the drainage basin requires in the
interceptor sewer which carries this flow to the Seattle treatment plant. With the base
flow of 2.75 mgd and the runoff pattern shown on Figure 10, the total volume of
combined sewage overflow would be 282 million gallons a year. Based on the runoff
pattern of this particular drainage basin, a design capacity of 25 mgd was chosen for the
screening facility. With this capability, 96 percent of the total volume of overflow would
receive treatment before being discharged to Elliott Bay. The added cost to achieve 100
percent treatment capabilities cannot be justified, as this would require a 40-mgd facility.
Approximately 40 percent of the 40-mgd facility's capacity would be idle 95 percent of
the time rainfall occurred.
90
-------
AMOUNT AND RATE OF STORM-CAUSED COMBINED OVERFLOW
AT
KING STREET REGULATOR DRAINAGE BASIN
SEATTLE, WASHINGTON
BYPASS 11 MILLION GALLONS
(4% OF TOTAL OVERFLOW VOLUME)
-DESIGN CAPACITY OF SCREENING
FACILITY (96% OF TOTAL OVERFLOW VOLUME)
-TOTAL VOLUME OF OVERFLOW
282 MILLION GALLONS
TOTAL HOURS OF OVERFLOW
AT 2.75 MGD OR GREATER s
100
200
300 400 500 600 700
TOTAL DURATION OF OVERFLOW AT R OR GREATER (HOURS/YEAR)
800
900
FIGURE 10
-------
PRESENTATION OF PROPOSED SCREENING FACILITY
A 25-mgd screening facility requires a structure approximately 30 feet wide and 75
feet long. A perspective of the proposed facility is shown on Figure 11. The elevated
facility is an attempt to illustrate what may be done to conserve the valuable parking
area and still provide an attractive and functional treatment facility. The configuration of
the elevated facility also offers the possibility of its becoming an integral part of an
elevated parking facility. This would provide more parking than is now available, which is
an asset to be considered. The facility does not provide disinfection.
Underground construction of the facility was investigated; however, this presented
several hydraulic problems, and would be more costly than the elevated structure. A
ground level structure for the Seattle facility was not investigated because conservation of
the parking was a major design consideration.
A site plan of the proposed facility is shown on Figure 12. The combined overflow
comes to the facility in the 48-inch sewer and would pass through a Parshall flume prior
to reaching the facility. The flume would provide the primary control for the operation
of the facility. After passing the Parshall flume, the flow would drop into a pump sump
where it would be lifted to the screening units by a single 250 hp, vertical turbine,
mixed-flow pump. The pump speed would be automatically controlled so that the pump
discharge matches the flow in the incoming sewer. After the flow has passed the
screening units, the screened effluent would be returned to the 48-inch interceptor
downstream of the pump sump, and would be discharged to Elliott Bay. The unscreened
flow would be returned to the trunk sewer where it would continue on to the treatment
plant. It is assumed that the influent flow will be adequately disinfected upstream of the
screening facility.
A design capacity of 25 mgd requires the use of ten 2.5 mgd screening units. The
floor plan and sections on Figure 13 illustrate a proposed layout of such a facility.
The screening facility will be designed to operate automatically. The primary control
for the facility would be located in the interceptor at the Parshall flume. The flume
would monitor the depth of flow in the sewer, and screening units would be turned on
and off in increments of 2.5 mgd as the depth of flow in the sewer rises and falls.
Because occasional back washing is necessary, a secondary control system is required to
sense this need and to initiate the process. This would be accomplished by installing a
flow meter on the screened effluent line. The flow signal from the effluent meter would
then be compared to the flow signal from the flume to detect a decrease in hydraulic
efficiency and, therefore, a need to backwash. It is anticipated that when the ratio of
screened effluent flow/influent flow falls below .80, the backwash cycle will be initiated.
92
-------
FIGURE 11
PROPOSED SCREENING FACILITY
PERSPECTIVE
-------
EXISTING
BLDG.
OUTFALL
BAY
I V'COMB
SEWER
A A S K A N
R/W LINE
ALASKAN WAY
42" R(
-------
TO ELLIOTT
EENED
LUENT
PROPOSE D
SCREENING
FACILITY
2VRCP TRUNK SEWER
ALASKAN WAY INTERCEPTOR
FIGURE 12
PROPOSED SCREENING FACILITY
SITE PLAN
95
-------
FIGURE 13
PROPOSED SCREENING FACILITY
FLOOR PLAN AND SECTION
-------
ESTIMATED CONSTRUCTION COST OF SEATTLE FACILITY
The cost of constructing the Seattle screening facility is estimated to be $538,000.
The construction cost estimate is based on estimated 1970 prices and assumes that all
work will be performed by private contracting firms. The estimate also includes an
allowance for design engineering, field surveying, soil exploration, construction
supervision and inspection, legal fees and contingencies. The estimate does not include
the cost of land or the cost of disinfection.
ESTIMATED ANNUAL OPERATION AND MAINTENANCE COSTS
A summary of the annual operation and maintenance costs is shown in Table 5.
Annual labor costs are based on one man-hour for each hour of operation. This is based
on the experience with the pilot unit, and is only an estimate of what may be
experienced in a full-scale facility. Annual maintenance costs are based on 3 percent of
the major equipment costs. Power and utility costs are based on present rates. Screen
replacement costs are based on a predicted life of 500 hours. Costs for cleaning agent are
based on the use of concentrated sodium hydroxide, purchased in bulk lots. The total
annual operation and maintenance cost is estimated to be $18,500.
Table 5
Estimated Annual
Operation and Maintenance Costs
Item Cost
Labor $ 5>600
Equipment Maintenance 3,000
Screen Replacement 3,500
Power 3,000
Gas 1,200
Cleaning Agent 700
Vehicle Operation and Maintenance 1,500
Total Annual Operation and Maintenance $18,500
97
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ESTIMATED TOTAL ANNUAL COST
A total annual cost figure provides the best basis on which an economic comparison
can be made, provided the items to be compared are relatively equal in basic design
considerations. The construction cost estimate for the Seattle facility violates this premise
in that the total cost includes provision for special foundation consideration and special
architectural treatment.
In order to compensate for this in the total annual cost figure, another cost estimate
was prepared for a more conventional type screening facility. In effect, the Seattle
facility was moved to an assumed site that did not have any special foundation problems
or did not require any special aesthetic considerations. It was assumed that this new
structure would be of concrete block walls supported by a concrete wall footing. The
floor would be a concrete slab on grade, and the roof would be of a timber joist system.
All other mechanical and electrical items would be the same as the Seattle facility. These
changes reduced the estimated total construction cost to $496,000 and it is this figure
which is used in the total annual cost figure to represent a more typical screening facility.
The total annual cost summary is presented in Table 6. All costs shown in Table 6
have been adjusted to assumed 1970 prices and include an allowance for design
engineering, legal fees, administrative costs and contingencies. The cost of land and
disinfection is not included. The construction costs are amortized over a period of 25
years assuming an interest rate of 6-1/2 percent. The cost per 1000 gallons is based on
treating a total of 271 million gallons per year.
Table 6
Estimated Total Annual Cost
Estimated Total Construction Cost $496,000
Annual Debt Service 41,000
Annual Operation and Maintenance 18,500
Estimated Total Annual Cost $ 59,500
Estimated Cost Per 1,000 Gallons = 22 Cents
DISCUSSION OF FEASIBILITY
In order to get a feel for the economic position of this type screening facility relative
to other possible methods of treatment, a brief economic comparison was made.
Particular attention was paid to conventional primary sedimentation; however, since a
detailed cost comparison was beyond the scope of this study, no cost figures will be
98
-------
presented. The brief comparison did reveal that screening can be a feasible treatment
method depending on particular conditions present at the site.
A major advantage of conventional primary treatment is that disinfection, by means
of conventional chlorination, can be accomplished within the primary clarifier. This
eliminates the need for a separate chlorine contact chamber which, at the present state of
the art of chlorination, would be required at a screening facility. This, of course,
represents a considerable added cost when disinfection is found to be either desirable or
mandatory.
This advantage, however, could be offset with a new method of disinfection that
could be as efficient as chlorination and at the same time eliminate the long contact time
that is presently required.
Another advantage of conventional primary clarification is that the volume of the
primary clarifier would be large enough to completely hold the storm-caused combined
sewage of the short-duration, low-intensity storm events. After the storm has passed and
the peak flow in the sewer has subsided, the impounded sewage could be returned to the
sewer at a reduced flow rate. This advantage is enhanced when there is a high percentage
of short-duration, low-intensity storms such as in the Seattle area.
The most important disadvantage of conventional primary clarification is the large
amount of land required. It has been estimated, by preliminary layouts, that conventional
primary clarification requires 10 to 20 times more land area than a screening facility. The
actual difference is dependent on the design capacity chosen for a primary treatment
plant, and how much reserve capacity of a primary clarifier is actually used to meet the
flow requirements of a particular drainage basin. This disadvantage becomes more severe
as the size of the drainage basin increases, and as the value of the land increases. The
Seattle site is an example of a site where conventional primary clarification would most
likely not be feasible.
In summary, the screening unit can be an economically feasible method of treating
combined sewage overflows when compared to conventional primary clarification. The
selection of the screening unit as a method of treatment at a particular site, however, will
require the review of at least four factors. These are:
1. The value and availability of land.
2. The size of the drainage basin, and therefore, the design capacity of the
treatment facility.
3. The character of rainfall and the pattern of runoff.
4. Available means of disinfection.
99
-------
Other factors that would require review also would include other methods of
treatment, aesthetic considerations, and ancillary use of the facility, such as surrounding
the Seattle facility with a parking structure. In all, it must be emphasized that each point
of overflow is unique, and all these factors must be reviewed before the most economical
and efficient method of treating combined sewage overflow is selected.
100
-------
CONCLUSIONS
1. High-rate, fine-mesh screening is an economically feasible method of treating
combined sewage overflows. When compared to conventional primary sedimentation,
however, the selection of a screening facility as a treatment method is dependent on
the value and availability of land, the design capacity of the treatment facility, the
character of rainfall and runoff, and the available means of disinfection.
2. The characterization of storm-caused combined sewage and dry-weather combined
sewage did not reveal any unusual constituents which could affect the long-term
effectiveness of the screening unit. These characterizations were compiled on the
basis of several composite samples.
3. The short-term effectiveness of the screening unit is significantly reduced by the
presence of oil and grease in the combined sewage. Oil slugs were observed at least
once a day for a duration of approximately 5 minutes, and were of a concentration
substantial enough to make the sewage appear black in color. The presence of an oil
slug reduces the hydraulic capacity of the screening unit by as much as 50 percent.
Frequent backwashing during the presence of an oil slug will minimize this problem.
4. The vibratory horizontal screen is not required in screening combined sewage
overflow. The presence of the vibratory horizontal screen reduces the hydraulic
capacity of the unit and, in some cases, results in lower removal efficiencies (see
Appendix C).
5. The overall performance of the screening unit is a function of the mesh size of the
collar screen, the rotational speed of the collar screen, the strength and durability of
the collar screen material, and the backwash operation.
6. The removal efficiencies of the screening unit increases as the mesh of the collar
screen becomes finer, and as the volume of the feed applied to the screen increases.
For example, 31 percent removal of total suspended solids was observed at an
influent flow rate of 1200 gpm (86 gal/min/ft2) with a 105 mesh screen (167
micron opening), while 35 percent removal was observed at a flow rate of 2000 gpm
(143 gal/min/ft2) with a 230 mesh screen (74 micron opening).
7. The removal efficiencies of the screening unit are independent of the rotational
speed of the collar screen.
8. The hydraulic efficiency of the screening unit increases as the rotational speed of
the collar screen increases, as the mesh of the collar screen becomes coarser, and as
the velocity of the feed approaching the screen increases.
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9. The life of the collar screen decreases as the velocity of the feed approaching the
screen increases and as the mesh of the screen becomes finer. For example, the
0
screen life observed at an influent flow rate of 1200 gpm (86 gal/min/ftz) with a
105 mesh screen (167 micron opening) was more than four hours, while the screen
life at a flow rate of 2000 gpm (143 gal/min/ft2) with a 230 mesh screen (74
micron opening) was less than four hours.
10. Approximately 90 percent of the screen failures were mechanical failures caused by
hydraulic overloading of the screen. The remaining 10 percent of the failures were
caused by punctures from objects present in the feed.
11. It is possible to produce a 165 mesh screen (105 micron opening, 45 percent open
area) with a probable life of 500 hours while operating at a flow rate of 1750 gpm
(2.5 mgd or 128 gal/min/ft2).
12. The use of a solution of hot water and liquid solvent in lieu of steam, was found
necessary to obtain effective cleaning of the screens.
13. Of the solvents tested, a caustic solution was the most efficient solvent for
backwashing the collar screen.
14. Screen blinding decreases as the velocity of the feed approaching the screen
increases, as the mesh of the screen becomes coarser, as the frequency of backwash
increases, and as the rotational speed of the collar screen increases.
15. A minimum of approximately 4.5 feet of fluid head above the downstream water
surface of the screening unit is required for gravity flow operation.
16. Based on the intensity and duration of rainfall in the Seattle area, a screening
facility in the Pacific Northwest can be expected to be in operation approximately
1000 hours a year.
17. The collar screen material is the limiting component of the screening unit. When a
stronger and more durable screen material is developed, it will be possible to
increase the hydraulic and removal efficiency of the screening unit.
18. The estimated construction cost for a 25 mgd screening facility is $496,000. The
estimated annual cost of operation and maintenance is $18,500. Based on a 25-year
bond issue, with an interest rate of 6-1/2 percent, the total annual cost is estimated
to be 559,500, which puts the cost of treatment at 22 cents/1000 gallons assuming
271 million gallons of overflow a year are treated. These cost figures are based on a
preliminary design of a screening unit for Seattle, Washington, which is presented in
this report.
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19. Based on the scale-up design of the Seattle facility, a screening facility will require
1/10 to 1/20 the land that a conventional primary sedimentation plant.
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RECOMMENDATIONS
1. It is recommended that a full-scale screening facility be designed and constructed to
demonstrate the feasibility of utilizing high-rate, fine-mesh screens in the treatment
of combined sewer overflows.
The results of this study have established the feasibility of the high-rate, fine-mesh
screens. The performance of the screens should now be demonstrated through the
design and operation of a full-scale facility. Based, in part, on the results of this
study, the equipment supplier has developed and tested a second generation unit.
The new unit is operated at 3 mgd (2100 gpm, 150 gal/min/ft^) with a 165 mesh
(105 micron opening) stainless steel screen with little or no deterioration in the
performance observed at the 2.5 mgd level. The equipment supplier has also
developed a new screen that has a probable life of about 500 hours. This represents
a hundredfold increase in life over that observed in this study.
During a period of demonstration, these new units could be tested and further
optimized with regard to inlet conditions, hydraulic capacity, screen life,
backwashing technique, and control systems. The period of demonstration would
also yield firm cost and operational data.
2. As part of a final design effort for a full-scale facility, it is recommended that a
systems analysis be performed to investigate the compatibility of the electrical and
hydraulic machinery.
In the preliminary design of the full-scale facility presented in this study, it was a
relatively simple matter to design a control system to operate the facility. Likewise,
it was also relatively simple to design the hydraulic machinery required of the
facility. The compatibility of the two systems, however, is very difficult to predict.
It is therefore recommended that an analog simulator be employed to simulate the
operation of a screening facility. The results of this study may reveal some basic
problems in control that can be resolved prior to the completion of a final design.
3. It is recommended that flow measurement and sampling facilities be installed at all
combined sewage outfalls where installation of treatment facilities is anticipated.
Based on the experience of this study, continuous flow recording at an overflow
point prior to the design of a treatment facility would be of significant value in
determining both the design capacity of the facility and the total use of the facility.
In addition, sampling facilities would be helpful in determining the character of the
waste to be treated. Composite samples would yield a general description of the
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waste, and grab samples could be collected to determine the quality and frequency
of any unusual constituents that may be present in the waste. If the installation of a
screening facility was anticipated, this information would be required for sizing of
screen materials and estimating the frequency and quality of backwashing.
4. It is recommended that a comprehensive study be conducted to determine an
efficient method of contacting a disinfectant with a treated effluent.
A major advantage in developing high-rate treatment equipment, like the proposed
screening facility, is the ability of the equipment to treat large volumes of waste in
a small area. This advantage would be negated, however, if conventional chlorine
contact times are required to provide disinfection. Based on the findings of this
study, the land required to provide conventional chlorination is 3 to 4 times that
required of the screening facility. In some cases, this requirement can be reduced or
eliminated by utilizing an existing outfall downstream of the facility for the contact
channel; however, this is normally the exception rather than the rule. Therefore, in
order to maintain the space advantage of high-rate treatment equipment, a high-rate
method of disinfection must be developed.
Currently, there is considerable research available describing the bactericidal
mechanism of several different disinfectants. Several of these studies indicate that
acceptable bacterial kills can be obtained with conventional disinfectants at contact
times of 10 minutes or less. Based on these observations, it is recommended that
additional research be performed to develop a contact chamber that will reproduce
these laboratory results in the field. It is believed this research will lead to a contact
chamber with two compartments. The first compartment would be a
mechanically-mixed rapid-mix tank with a detention time of less than 3 minutes.
This complete-mix tank would provide rapid and intimate contact between
disinfectant and effluent. The rapid-mix tank effluent would then enter a period of
quiescent contact provided by a plug-flow type tank with a detention time of less
than 15 minutes. It is this combination of two distinct flow regimes that approaches
many of the laboratory procedures used in bactericidal studies, and it is a type of
flow regime that may provide a more efficient and economical method of
disinfection.
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REFERENCES
1. "Problems of Combined Sewer Facilities and Overflows 1967," Water Pollution
Control Research Series WP-20-11, U. S. Dept. of Interior, FWPCA, December 1,
1967.
2. "Standard Methods for the Examination of Water and Wastewater." 12th Ed., Amer.
Pub. Health Assn. New York (1965).
ACKNOWLEDGMENTS
The author wishes to thank the City of Portland, Oregon, and SWECO, Inc., of Los
Angeles, California, for their cooperation and assistance in conducting this study for the
Federal Water Pollution Control Administration.
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SECTION 3
ASSESSMENT OF COMBINED SEWER PROBLEMS
by
Richard H. Sullivan
Assistant Executive Director
for Technical Services
AMERICAN PUBLIC WORKS ASSOCIATION
Chicago, Illinois
for the
FEDERAL WATER QUALITY ADMINISTRATION
DEPARTMENT OF THE INTERIOR
June, 1970
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ASSESSMENT OF COMBINED SEWER PROBLEMS*
by Richard H. Sullivan
Assistant Executive Director
for Technical Services
American Public Works Association
The water pollution problems which have become the target of public
opinion and public official concern are the sins of the past being imposed
on the present. We are today racing headlong to catch up with yesterday's
custom of using rivers to rid man's environment of his undesirable waste
into the waters most convenient to his urban habitat. Now that there is a
national desire to clean up the discharge of sewage and industrial waste by
construction of treatment plants of adequate processing effectiveness, atten-
tion is turned to another sin of the past that is being imposed on the present-
the discharge of excess flows from combined sewers everytime it rains.
The problem stems from the early use of storm drains to handle
domestic sewage by admitted sanitary flows to these conduits. When sewage
treatment was not practiced, the fact that combined sewers spilled their
waste water into receiving streams was not a matter of concern, but when
'treatment was provided for sanitary sewage it becomes necessary to install
in combined sewer interceptors, regulator devices which would divert dry
weather flow to the treatment plant and during storm run-off period to
excessive flows to receiving waters.
In urban areas where adequate sewage treatment is provided, these
periodic overflows stand as a negative effect which minimizes investment in
pollution control. A water course that is polluted periodically is only
little more usable for most purposes than one that is continuously polluted.
As more and more sewage treatment facilities are provided, meeting Federal
and State Standards for high degrees of treatment, the anomaly of combined
sewer overflows becomes more and more obvious.
COMBINED SEWER FACILITY INVENTORY
In 1967, at the request of the Federal Water Pollution Control
Administration, the American Public Works Association undertook to make an
inventory of combined sewer facilities in the United States. Every local
jurisdiction with combined sewers whose population exceeded 25,000 was
personally interviewed, as well as a large sampling of other jurisdictions--
including communities with a population of less than 500. In all, 641 juris-
dictions were interviewed. We estimated that 46 per cent of the communities
vith 94 per cent of the population and 84 per cent of the area served by
combined sewers were directly interviewed.
The results of the survey indicated that 36,236,000 people, living
on 3,029,000 acres were served by combined sewers. This total indicates
that approximately 29 per cent of the nations total sewered population is
served by combined sewers.
*Prepared for seminar on Storm and Combined Sewer Problems, Chicago, Illinois,
June 22-23, 1970
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Mere numbers do not in themselves make a problem. In the past ten
to fifteen years, there has been a substantial effort to construct waste
water treatment facilities. Overflows from combined sewers are gradually
being identified as one of the continuing sources of pollution. The early
rationale that held that since the overflow was 99 plus per cent storm water
it was "clean" has been disproved. Overflows are polluted.
The small flows of sanitary sewage in large combined sewers results
in low velocities. Solids are therefore settled out along the sewer line.
Storm flows tend to scour out this material and carry it to the overflow.
A large proportion of the sanitary sewerage also escapes in the overflow.
It has been estimated that from three to five per cent of the total organic
load reaching the sewer leaves by the overflow.
A part of the problem of combined sewer overflows is the location
of the overflow facilities and the nature of the receiving waters. Nationally,
most overflows are adjacent to residential or industrially zoned land. The
major receiving waters are dry water courses or waters used for limited body
contact recreation or fishing.
These land and water uses are not suitable places for the discharge
of sewage. Presence of the combined sewer overflows may have a serious
impact upon land development and land values. For a hundred acre tract in
one Michigan city, influenced by one combined sewer overflow, our appraiser
estimated that a value loss of $600,000 in the immediate area and to the
adjacent area of 1,333 acres, $4,476,000. This loss of value results in a
tax loss to the city alone of $70,000 per year.
The American Public Works Association, as a part of its 1967 study,
was asked to estimate the cost of separating combined sewers nationwide. We
analyzed figures for weeks, adjusted for prices, inflation and about every-
thing else, and ended up with $48 billion in 1967 dollars as the answer.
Of this, $30 billion was for work in the public right-of-way and $18 billion
for changing the plumbing on private property. The complete incapability of
many of our major urban areas to bear the disruption of their major commercial
areas and major streets makes complete separation an unlikely goal. Therefore
we also investigated alternatives and from the information available we
estimated that the cost of alternate methods of treatment or control would
amount to about $15 billion. Such methods include in-system and off-system
holding and drainage area control.
The States, in particular, and many other agencies have enacted
regulations which prohibit the construction of new combined sewer systems
or the additions to existing systems. Unhappily some of the progress which
is being made in metropolitan areas is in new suburban developments where
separate sanitary sewers in a great many cases discharge into combined sewers
and add higher concentration of sanitary sewage to the overflows.
Another major finding from our interviews was the determination that
less than 20 per cent of the combined sewer overflow regulators were of a
true dynamic type, that is they could be adjusted to meet various flow
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criteria. Of the 10,025 regulators found in the jurisdictions interviewed,
40 per cent were nothing nothing more than simple weirs, many with design
features which are not responsive to overflow regulation. In fact many were
merely a hole in a manhole to relieve the system.
The use of improper types of regulators for the existing conditions
as well as poor maintenance practices appeared to be one of the major reasons
for unnecessary and prolonged overflows.
Another finding was that infiltration was recognized as being exces-
sive in a great many systems. Although few jurisdictions had apparently
surveyed their systems, treatment plant records indicate the excessive wet
weather flows.
Sewer personnel across the country told us of their efforts to
discontinue the connection of roof gutters, area drains and foundation drains
to the combined sewer system. The flow from these sources is generally
credited with overloading the sewer system, causing both basement flooding,
innundation of mid-city areas and more frequent and prolonged overflows.
Questions were also asked of each jurisdiction as to the number of
personnel and the level of training of employees associated with the opera-
tion and maintenance of the sewer system. In jurisdictions of less than
25,000, on the average less than one-half have a full time registered
engineer or an engineer in training. For the 52 jurisdictions from 10,000
to 50,000, the average was only 3.3 registered engineers in training per
jurisdiction. This group also averaged 5.4 certified plant operations per
jurisdiction. Thus, it appears that generally there may be an inadequate
number of trained personnel available to make maximum utilization of today's
technology.
The full report is available from FWQA as publication WP-20-11
for $1.00.
STUDY OF URBAN STORM WATER POLLUTION
With sewage and industrial waste treatment a reality and the water
resources of the nation—or at least of major watersheds—protected; and
with the overflows of combined sewers effectively regulated and minimized,
in terms of the "two Q's" of quantity and quality of the spilled waste water
to receiving waters, still another "sin" of the past will stand as a challenge
to the present and the future.
This will involve the evolution of a new concept of the pollutional
impact of separate storm water discharges on water courses, lakes and coastal
waters. Since everything is relative, it is understandable that storm water
has in the past been considered harmless as compared with the pollutional
nature of untreated or inadequately treated sewage and industrial wastes
and the nature of combined sewer overflows of admixtures of sewage and storm
water runoff.
But with the elimination or minimization of these two obvious sources
of pollution, it will not be surprising that attention will eventually come
to bear on storm water spills. Are they a source of pollution? What are
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these sources? What could be done about urban runoff waste waters? What
is the role of agricultural land runoff in the total water pollution control
picture and the problem of protecting the nation's water resources for use
and reuse purposes?
Some of the answers of these basic question are found in the study
of Water Pollution Aspects of Urban Runoff which was carried out from 1966
to 1968 by the APWA under a contract with the FWQA. The report on the
study is published as WP-20-15 for $1.50.
"Clean" storm water is polluted. Rain scavenges air pollution out
of the atmosphere; flows across roofs, across grass sprayed with insecticides
and fertilized with nitrogen and phosphorous, pets and birds; along street
gutters which may average a daily accumulation o£ more than a pound of debris
each day per 100 ft. of curb; and finally through catch-basins where the
flow displaces perhaps two cubic yards of stagnate water and carries with
it some of the digested solids from the bottom of the catch-basin. By the
time the storm water reaches the sewer, it may exceed the strength of sanitary
sewage. When salts from snow and ice control, phenols and lead from automobile
exhausts and other contaminates are added, the storm water may have a wide
range of undesirable characteristics.
TYPES OF PROBLEMS
The pollution problems which have been generally identified with
combined sewers include the following:
1. Pollution of receiving waters
a. too frequent overflows
b. dry weather overflows
c. prolonged overflows
d. carryover of solids
e. by-passing to protect waste water treatment plant facilities
2. Disruption of waste x-jater treatment plants
a. concentration of solids and debris in primary treatment
b. wash-out of secondary treatment process due to low strength
flows
c. salt water intrusion
At the heart of most of these problems appears to be the combined
sewer regulator and the capacity of the treatment plant.
Most jurisdictions have not attempted to assess the extent of the
pollution of receiving waters. In many areas the effects of combined sewer
overflows are masked by other major sources of pollution, such as untreated
or poorly treated sanitary sewage, industrial waste, agricultural land run-
off, feed lot runoff, and urban storm water runoff.
The disruptive aspects of combined sewer flow at the waste treatment
plant are readily determined by plant operators. In many instances this
has led to even further diversion or by-passing to minimize treatment plant
problems.
Ill
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The AIWA Research Foundation, under contract with the Federal Water
Pollution Control Administration and some 25 local governmental agencies,
has completed a cooperative study of combined sewer system overflow regulator
facilities and practices. This study covered design, application, construction,
control and operation and maintenance procedures. The specific purpose of
this project was to analyze and evaluate the effectiveness of practices and
to establish long-needed guidelines for more efficient aid dependable control
of overflows and for reduction in the frequency and duration of combined
sewer flows and the resultant pollution in waters receiving such spills.
THE FUNCTION OF REGULATOR DEVICES
The volume of liquid flowing in a combined sanitary and storm water
sewer is greater than the carrying capacity of the interceptor sewer system,
the pumping capacity of a pumping station or the capacity of a sewage treat-
ment plant, during periods of storm and runoff. It is the function of a
regulating device and the chamber in which it is installed to regulate or
control the amount of the flow which is allowed to enter the interceptor
system and to divert the balance to holding or treatment facilities, or to
discharge this balance to a point of disposal in nearby receiving waters.
The regulator, thus, has the function to transmit all dry weather flow to
the interceptor and hence to sewage treatment works, and to "split" the
total combined storm and sanitary flow during periods of runoff so that a
portion of the flow enters the interceptor and the balance is diverted to the
other points listed above.
Regulators may be of various kinds—such as stationary, movable,
mechanical, hydraulic, electrical, fluidic, variable, non-variable, etc.--
but their function is as described. The 1967 study of overflow problems
indicated the need for improvement in regulator devices and in their
operation and maintenance. Over and above today's regulator facilities,
the field of combined sewer service would be benefited by the availability
of other types of devices and modifications of existing equipment. Among
the challenges are greater sophistication in control and actuating facilities,
including on-site remote sensing and control of intercepted flows, paced by
conditions in interceptor and treatment works, and desired diversion of
flows into holding and treatment processes for the effective reduction in
storm water overflow pollution.
Figure 1, Static Regulator, Side outlet connection is a photograph
of a typical static regulator with a low weir. This device, while inexpen-
sive to construct, may be a source of dry-weather overflows due to clogging
and cannot be adjusted to variations in dry-weather flow.
Figure 2, Typical Manually Operated Gate Regulator, although a
static device, can be adjusted to various flow conditions. Such a facility
can be modified with a motor operated gate and proper controls to be a
dynamic regulator, responding to flow conditions in the collector or inter-
ceptor sewer.
Figure 3, Cylinder Operated Gate, indicate the layout of a hydraulic
cylinder gate in Philadelphia. This is a dynamic regulator in as much as
the position of the gate is controlled by a float-off of the collector sewer.
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Figure 4, Float Operated Gate, is an isometric view of a dynamic
gate, the position of which may be regulated by flow in either the collector
or interceptor sewer.
(Insert Fig, 1-4)
The problem of design, manufacture, application and handling of
regulators is made difficult by the conditions under which these devices and
regulator chambers must function. These include complex and often unpredict-
able hydraulic conditions imposed by dramatic changes in runoff due to
storms; the heterogeneous nature of the sewage-storm water which is handled,
including grit, coarse debris and other clogging producing wastes; the corrosive
nature of the liquids; and the humid and corrosive-gaseous conditions in
the regulator chambers. Further complications are created by tide water
backflows and other hard-to-predict hydraulic conditions in interceptor-
treatment plant networks.
Our study of combined sewer regulators involved the interviewing of
a group of jurisdictions and then in cooperation with a panel of consulting
engineers preparing both a report and manual of practice. Representatives
of financially participating jurisdictions as well as the WPCF and the ASCE
served on the steering committees for the study.
The study report, "Combined Sewer Regulator Overflow Facilities" and
the "Manual of Practice for Combined Sewer Regulation and Management" will
soon be available from the FWQA.
Our detailed, extensive interviews of some seventeen jurisdictions
have found only three where the operation of the regulators has been designed
to minimize pollutions by assuring that the interceptor sewer is fully charged.
These three projects have received FWQA demonstration grants. In Seattle,
this is accomplished by a hydraulically operated gate controlled by a bubbler
unit downstream in the interceptor. In Minneapolis-St. Paul Sanitary District,
control is achieved through the use of an inflatable dam, increasing the head
of the orifice discharge to the interceptor sewer. Detroit is also using a
form of "traffic" control to maximize flow in the interceptor.
An additional principle of operation to minimize pollution is to
maximize in-system storage. The Seattle system in particular insures that
all of the collector storage capability is utilized prior to an overflow
event. This capability does much to eliminate dry-weather overflows and
minimize pollution in their system.
Engineering investigaticn s are being made in Seattle to determine
where there is justification for upgrading the facilities. The study is
conducted by monitoring a facility for the length of time and quantity of
flow during overflow events. From the characteristics of the contributory
sewer system, a mass hydrograph is constructed to analyze the quantity and
time of flow should a controlled facility be installed. One recent study
indicated that for one small drainage area, for a short period of time when
eight (8) events occurred which overflowed 6.4 million gallons, that had a
dynamic regulator been installed only one event of 2.7 million gallons would
have occurred, a reduction of 85 per cent in frequency and 42 per cent in
volume.
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When information of this type is available, the value of upgrading
facilities can be made. There are no magic numbers or rules of thumb — an
engineering study is needed in each case.
Some of the major findings and recommendations of the study call for
a reduction in the number of small overflows, total systems management of the
combined sewer system, use of dynamic type regulators to allow response to
hydraulic conditions in the sewers, use of regulators that improve the
quality of the overflow as well as the control of- its quantity, and the need
for improved maintenance and design of regulator facilities.
Figure 5, Spiral Flow Regulator, is a drawing of an experimental
device which has been tested in England to induce helical motion in the flow.
Such a secondary motion tends to concentrate the solids and they may be drawn
off with the flow to the interceptor, improving the quality of the overflow.
Figure 6, Vortex Regulators, is a drawing of two regulators which
have been installed in Bristol, England. The induction of the vortical
motion acts to concentrate the solids in the flow to the interceptor. Both
of these regulators are compact and appear feasible for installation in many
existing situations. We have recommended that additional research be carried
out to define design relationships and the efficiency of the units to remove
solids from the overflow.
(Insert Fig. 5 & 6)
Maintenance was found to be an important factor in the successful
use of various types of regulators. The amount of money allocated gives an
indication as to how effective local officials judge their regulators to be.
Where dynamic regulators have been used and low levels of maintenance have
been provided, the dynamic regulators have often been taken out of service.
The survey found that many regulators have, by necessity, been
constructed where maintenance is difficult and access almost impossible.
Figure 7 is a picture of the boat and barge used by the Allegany County
Sanitary Authority (ALCOSAN) for the maintenance of overflow facilities which
can only be reached from the river.
Figure 8 is a photograph showing the variety of equipment carried on
the barge.
(Insert Fig. 7 & 8)
Th&re must be a commitment upon the local jurisdiction to properly
maintain any new or improved regulators which may be installed in a pollution
control program. Although out of sight, regulator facilities must be kept
in mind.
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ROLE OF INFILTRATION CONTROL
Expenditures for sanitary and combined sewers and treatment facilities
amount to many millions of dollars annually and form a major part of the
total amount budgeted for operations and capital improvement programs in
every urban community.
Unfortunately, in most urban areas, little attention has been given
to making sure that costly sanitary and combined sewers and sewage treatment
facilities function properly, if at all, under wet ground conditions. So-
called "separate" sanitary sewer systems often collect such large infiltration
flows that they are ineffective in performing their primary function. Infil-
tration in sanitary sewers usually causes flows which exceed treatment plant
capacity and, as a result, biological processes are either upset or raw
sewage is by-passed into waterways which were intended to be protected from
such contamination.
Infiltration was revealed as a contributing factor in combined sewer
overflows in a report prepared in 1967 by the AFWA Research Foundation which
was previously described. Thirty-four per cent of the cities interviewed
indicated that infiltration exceeded their specification. The increased
flow in combined sewers due to infiltration decreases its in-system storage
capability and results in more frequent and longer duration of overflows.
Most engineering consultants, scientists, and administrators in the
field of design, operation and management of sanitary sexv'age collection
systems have little quantitative data available to use in estimating the
extent of infiltration and in making value judgements for the most effective
means of prevention and control.
The APWA Research Foundation in cooperation with 35 local jurisdictions
and the FWQA. has undertaken a study of economics of infiltration control,
design and construction practices for new construction and remedies for
existing systems where the cost benefit ratio of control indicates that such
action is desirable. This study will be completed in the next few months.
In this study, the factors contributing to storm and ground water
infiltration are evaluated and analyzed to produce guidelines which will
be of tangible value to designers, administrators and operators of combined
and sanitary sewage collection systems and treatment plants.
The study is designed to aid in the formulation of an effective
research and development program to reduce pollution resulting from combined
sewer overflows and treatment plant by-passing attributable to infiltration.
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FIGURE 1
Static Regulator Side Outlet Connection
-------
STANDARD F a C
"D
O
> r~
-o H —
i m S
i»l
m ™ >
-DC —
m
o
REINFORCED CONCRETE
OPERATING VALVE
Tl
O
C
JO
m
-------
FIGURES
Cylinder-Operated Gate
FIGURE 4
Float Operated Gate - Courtesy Brown & Brown, Manufacturing
118
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FIGURE 5
FLUME INVERT
CROSS CONNECTION FOR OVERFLOW
CONTROL
PIPE FOR NORMAL FLOW
PROFILE ALONG CENTER LINE
OVERFLOW WEIR-S
WITH DIP PLATES
CHANNEL FOR NORMAL
FLOW 8 HEAVY SOLIDS
FLUME FOR
FLOATING
MATERIAL
PIPE FOR NORMAL
FLOW 8 SOLIDS
SECTION "A"-"A"
CONTROL PIPE FOR
OVERFLOW CHAMBER
TO INTERCEPTOR
SECTION "B"-"B"
Courtesy Institute of Civil Engineers
S PIRAL FLOW (HELICAL)
REGULATOR
119
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COMBINED SEWER
STORM SEWER
B
INLET 36 DIA.
FIGURE 6
AFFLE
BRANCH INTERCEPTOR
TO TREATMENT PLANT
SECTION "A"-"A"
WHITE LADIES ROAD
COMBINED SEWER
INLET 4X3
OUTFALL
SCUM BOARD
Courtesy Institute of Civil Engineers
BRANCH.
INTERCEPTOR
SCALE OF FEET
0 5 10 15
zo
ALMA ROAD
VORTEX REGULATORS
120
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FIGURE?
Boat and Barge Used by Allegheny County Sanitary Authority for
Maintenance of Some Overflow Facilities
MGUKt 8
Derrick Barge with Equipment. Allegheny County Sanitary Authority.
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SECTION 4
THE USE OF SCREENING/DISSOLVED-AIR
FLOTATION FOR TREATING COMBINED SEWER OVERFLOWS
by
Donald G. Mason
Technical Center
Rex Chainbelt Inc.
Milwaukee, Wisconsin
for the
United States Department of the Interior
Federal Water Quality Administration
Contract #14-12-40
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ABSTRACT
Results from the many projects now being sponsored by the Federal
Water Quality Administration indicate that the majority of the pollu-
tants present in combined sewer overflow are in the form of particulate
matter. This indicates a high degree of treatment could be obtained
by utilizing an efficient solids/liquid separation process. This
report documents a study on the treatment of combined sewer overflow
by screening and dissolved-air flotation. The objectives of the
project are to determine the effectiveness and cost of a screening/
flotation system.
A combined sewer (Hawley Road) in Milwaukee, Wisconsin was
monitored and laboratory testing which included screening, chemical
oxidation, and dissolved-air flotation was performed. The results
of the laboratory tests indicated a combination of screening/flota-
tion provided a feasible system and a prototype demonstration unit
with a 5 MGD capacity was designed and installed.
The system has been operated on 30 overflows. Removals of BOD,
COD, SS, and VSS have been in the range of 50 to 75%. The waste solids
stream has averaged only about 1 percent by volume of the raw feed
water. Operation has been very satisfactory with a minimum of main-
tenance required. Chemical flocculants have been utilized to increase
the removal efficiencies to the upper values of the above range.
Cost estimates have been made and these indicate a total installed
cost of $12,000 per MGD capacity. These costs do not include land or
interceptor costs to combine a series of overflows. Operating costs
are estimated at l.Oc/1000 gallons without chemical flocculant addition.
Chemical costs should be in the range of 2.0-2.5
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INTRODUCTION
The pollutional characteristics of combined sewer overflow are
being documented through the many federally sponsored projects which
are now underway. Preliminary results indicate that the majority of
the pollutional substances present in combined sewer overflow are in
the form of particulate matter. This indicates that a high degree
of treatment could be obtained by utilizing an efficient solids/liquid
separation process. The objectives of this project (FWQA Contract
#14-12-40) are to determine the design criteria, effectiveness, and
economic feasibility of using screening and dissolved air flotation
to treat combined sewer overflows.
The project is currently underway. Completion is expected by
late spring or early summer of 1970. Discussed herein is a review
of the results obtained to date, tentative design criteria, and
expected removal efficiencies.
SUMMARY AflD CONCLUSIONS
Based on the data collected during the study and reported herein,
it appears that screening/dissolved-air flotation can be utilized as a
successful alternate to sewer separation in some areas. Removals of
BOD, COD, SS, and VSS in the range of 50-75% were recorded for the
30 overflows monitored to date. The solids removed from the overflows
represented only about 1 percent (by volume) of the raw wastewater
flow and had a concentration of 2 to 4%. The entire system is
completely automated and requires a minimum of maintenance.
Cost estimates indicate the complete installed system capital
cost will be $12,000 per MGD capacity. This cost does not include
land or sewer interconnection costs. Operating costs were estimated
at 3.0 to 3.5C/1000 gallons based on the use of flocculating chemicals
to obtain the maximum removal efficiency. Operating costs without
chemicals is estimated at less than l.Oc/1000 gallons.
DESIGN OF TEST FACILITY
During the fall and spring of 1967, the Hawley Road Combined Sewer
in Milwaukee, Wisconsin was monitored. A total of 12 overflows were
sampled. Laboratory scale testing on these samples included screening
with various size media, chemical oxidation, flotation, and disinfec-
tion. Laboratory analyses on the untreated overflow as well as the
effluents from the laboratory bench tests were analyzed for BOD, COD,
SS, VSS, and disinfection requirements. It was determined from this
testing that chemical oxidation did not appear technically feasible (1).
However, encouraging results were obtained from the screening and
flotation tests. These tests served as input data in the design of a
test facility utilizing screening and dissolved-air flotation. A
process flow sheet for the system is shown in Figure 1.
The system basically consists of a screen chamber and a flotation
127
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RAW FLOW
to
oo
WASTE SOLIDS
AIR SOLUTION
TANK
SCREEN
CHAMBER
SCREENINGS
AIR
r- CHEMICAL FLOCCULANT ADDITION
FLOTATION CHAMBER
TREATED
FLOW
FLOATED SCUM
FIGURE 1
PROCESS FLOW SHEET
-------
chamber. The screen is an open ended drum into which the raw waste flows
after passing a ^" bar rack. The water passes through the screen media
and into a screened water chamber directly below the drum. The drum
rotates and carries the removed solids to the spray water cleaning system
where they are flushed from the screen. Screened water is used for flush-
ing. The spray water and drum rotation are controlled by liquid level
switches set to operate at 6 inches of head loss through the screen.
The flotation chamber is a rectangular basin with a surface skimming
system to remove floated scum. Screened water is pressurized and
mixed along with air in an air solution tank. The liquid becomes
saturated with air and when the pressure is reduced minute air bubbles
(less than 100 micron diameter) are formed. This air charged stream
is then mixed with the remaining screened water flow. The bubbles
attach to particulate matter and float it to the surface for sub-
sequent removal by the skimmers. Chemical flocculants may be added
to enhance the removal efficiency of finely divided particulate matter.
The design criteria utilized in the design of the test facility
are shown in Figure 2. These criteria provide the wide flexibility
necessary in a test facility. More precise design criteria will be
given later. The system was designed to treat 5 MGD of combined
overflow.
FIGURE 2
GENERAL DESIGN CRITERIA FOR DEMONSTRATION SYSTEM
Screen
1. Raw Flow Rate 3500 GPM
2. Hydraulic Loading 50 GPM/sq ft
3. Screen Size 50 x 50 297 micron openings
4. Screen Wash 150 GPM maximum
Flotation Tank
1. Flow Rate 3500 GPM
2. Surface Loading 3-9 GPM/sq ft
3. Horizontal Velocity 3 FPM
4. Pressurized Flow Rate 400-1100 GPM
5. Operating Pressure 40-70 PSIG
6. Minimum Particle Rise Rate 0.5-1.5 FPM
All pumps and auxiliary equipment were sized on this flow. The flota-
tion tank is compartmentalized to allow variation in the surface load-
ing without changing the raw flow rate. Pressurized flow rate and
operating pressures can be maintained over a wide range of values. A
photograph of the demonstration system is shown in Figure 3.
129
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:
..
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RESULTS OF OPERATION
The test facility was completed and put on stream in May of 1969.
Since that time 30 overflows have been monitored. It has been observed
that about 25% of these overflows have high pollutional load during
the first portion of the overflow. This period of first flushes has
never lasted longer than one hour and has been as short as 10-15 minutes.
After these flushes pass the characteristics of the overflow become
relatively constant. This period has been called the extended over-
flow period. The range of pollution parameters measured for these 30
storms at the 95% confidence level is shown in Figure 4.
FIGURE 4
CHARACTERISTICS OF COMBINED SEWER
OVERFLOW FROM HAWLEY ROAD SEWER
First Flushes
COD 500-765
BOD 170-182
SS 330-848
VSS 221-495
Total N 17-24
Extended Overflows
COD 113-166
BOD 26-53
SS 113-174
VSS 58-87
Total N 3-6
All values in mg/1 at 95% confidence level.
Coliform 310 x 103 to 1.5 x 103 per ml.
It may be observed that the first flushes data has quite a wide range
of values, while the extended overflow data has a relatively narrow
range. All laboratory analysis were performed according to Standard
Methods (2). The data presented correlates well with combined over-
flow data from the Detroit Milk River Study (3) and other published
data (4).
The operation of the previously described test facility during
the spring, summer and fall of 1969 has provided valuable data on
operational characteristics and removal rates. Figure 5 shows the
data associated with operational variables. The range of values for
screen wash and floated scum volume are shown at the 95% confidence
level.
131
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FIGURE 5
OPERATION DATA FROM HAWLEY ROAD DEMONSTRATION SYSTEM
Length of
Run
Hours
1-4
Raw Flow
Rate
GPM
3500
Screen Wash
As % of Flow
7,
0.29-0.64
Floated Scum
As % of Flow
0.43-0.85
Pressurized
Flow Rate
GPM
400-900
Operating
Pressure
PSIG
40-60
The average run had a length of 1-4 hours. The flow rate for these runs
was held constant at 3500 gpm. Pressurized flow was varied over the
range of 400-900 gpm and the operating pressure from 40-60 psig. Of
considerable importance in the design of this type of system, is the
volume of residual solids produced during operation. As shown in
Figure 5, the volume of water required to backwash and clean the screen
ranges from 0.29 to 0.64 percent of the raw flow rate, while the
volume of floated scum ranges from 0.43-0.85 percent at the 95%
confidence level. Solids concentrations in these streams generally
is in the range of 1 to 2%, and at this concentration they easily flow
by gravity. Disposal methods utilized for these solids streams should
be sufficient to handle the upper limit of the expected sludge volumes.
Under the current contract, the solids are disposed via an interceptor
sewer which directs them to the sewage treatment plant. Other alter-
natives for solids disposal include trucking in tanker trucks or
providing a portable vacuum filter to visit the various treatment
sites and produce a dry cake for hauling to ultimate disposal.
The efficiency of contaminant removal experienced for the overflows
monitored to date, is shown in Figure 6. All runs were started with the
tank full of water from the previous run. For this reason collection
of effluent composite samples was not started until 15-20 minutes into
the run to avoid collecting unrepresentative samples. All other samples
were taken immediately. The tank can also be operated in a near empty
mode for start up. Only a small amount of water is required to allow
immediate start up of the pressurized flow system. Clarification will
then start immediately as raw waste begins to enter the tank.
FIGURE 6
CONTAMINANT REMOVALS IN PERCENT JJY SCREENING AND FLOTATION
Screening and Flotation
Screening
BOD
COD
SS
VSS
NOTES:
Spring
23.4 ± 9.3
33.9 ± 10.7
28.8 ± 10.5
28.2 ± 13.6
Summer-Fall
20.3 ± 6.5
22.4 ± 5.0
24.9 ± 9.8
24.4 ± 13.2
W/0 Chemical
Flocculants
(Spring)
48.4 ± 15.7
52.9 ± 8.7
53.7 ± 11.7
51.0 ± 15.9
W/Chemicals
Flocculants
(Summer-Fall)
50.8 ± 12.5
53.4 ± 8.6
68.3 ± 8.4
64.8 ± 10.0
Removals as % @ 95% confidence level.
Screen openings 297 microns.
Surface loading 3 GPM/sq ft.
132
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Two time periods are shown, spring storms and summer/fall storms. By
observing the screen data in Figure 6, it may be seen that during the
spring storms removals ranged from 23-33 percent for all listed
parameters. This was consistent with the preliminary data collected
the previous year. During the summer/fall storms, however, COD
removals decreased indicating a change in the characteristics of the
overflow. It was determined that an increase in soluble organics
had occurred which was the probable cause for the noted decrease in
COD removal across the screen. The mechanical operation of the
screen has been very satisfactory. The media utilized was type
304SS. No permanent media blinding has been experienced, No build-
up of greases or fats has occurred. Some clogging problems have
been experienced with the spray nozzles, but this was caused by a
sealing problem around the screen, which allowed unscreened water to
pass into the screened water chamber.
The overall removals, i.e. screening plus flotation are also
shown in Figure 6. Removals are shown with and without the addition
of chemical flocculants. The chemical flocculants when utilized were
a cationic polyelectrolyte (Dow C-31) and a flocculant aid (Calgon A25).
The polyelectrolyte dosage was 4 mg/1 and the coagulant aid dosage
was 8 mg/1. Contaminant removal without chemical addition was about
50% for all parameters as shown in Figure 6. Adding chemicals caused
an increase in SS and VSS removals to around 70%. COD and BOD removals,
however, did not increase significantly. This was probably a result
of the increase in soluble organics associated with the summer/fall
overflows. Chemical addition also provided a strengthening effect on
the floated sludge blanket which is very desirable from the solids
handling aspect. Mechanical operation of the flotation tank has been
excellent. No mechanical problems have been experienced. Maintenance
on the entire system is limited to periodic lubrication and requires
less than 6 man hours per month.
Another important aspect in the treatment of combined overflow
is disinfection. Figure 7 shows the effect of chlorination on total
coliform density from various overflows.
FIGURE 7
DISINFECTION DATA FOR COMBINED OVERFLOWS AT IiAWLEY ROAiJ
Raw Coliform Effluent Coliform
Density Chlorine Dosage Contact Time Density
Storm if per ml mg/1 min. per 1UO ml
5 36,OOU 10 15 0
6 5,700 10 15 0
7 1,300 10 15 0
8 7,800 10 15 0
9 6,200 10 15 2
11 20,000 10 15 10
19 310,000 10 10 600
20 160,000 10 10 400
21 55,000 10 10 0
22 82,000 10 10 1500
133
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In storms 5 through 11 chlorine was added in the pressurized flow line
prior to olending with the remainder of the flow in the flotation tank.
ihe dosage was 1U mg/1. The dosage may nave actually been lower in
some of the runs, since sodium hypochlorite was utilized as the source
of chlorine and this solution decreases in strength over a relatively
short period of time. Introduction of the chlorine in the pressurized
flow allowed approximately 15 minute contact time before discharge from
the unit. In storms 19 through 22 chlorine was added to the effluent
from the flotation basin and allowed to react for a ten minute period.
The chlorine was then deactivated with sodium sulfite and coliform
analyses were performed. It may be observed in Figure 7, that coliform
reduction was related to initial coliform density when using a constant
chlorine dosage. In the spring and early summer when coliform densities
were low, good disinfection was obtained. However, in late summer when
coliform density increased, the effluent contained increased numbers of
coliform organisms. Chlorine demand tests were run on some storms. The
chlorine demand was generally in the range of 13 to 17 mg/1.
CONCLPIUAL Dt-SIGN
The use of screening/flotation in full scale installations to
treat combined sewer overflows requires integration of a variable rate
pumping system, a screening/flotation system, and a solids storage
and/or disposal system. Ihe full scale design will be based on a
modular concept. It is envisioned that a number of screening/flotation
modules will be assembled and operated in parallel. A pumping system
and solids storage/disposal system will complete each treatment site.
All components in the integrated system can be automated 100%. Telemetry
will probably be utilized to send the data and monitor the system from
a central location. Figure 8 illustrates the complete treatment system
concept. Raw wastewater enters the sump at a variable rate. The pump-
ing system consists of a series of pumps of both fixed and variable
capacity. A depth gauging system controls the pump output to match raw
waste input. The feed pumps direct the waste flow to the proper screen-
ing/flotation module. It is anticipated that a single screen will feed
two flotation cells. Screening/flotation modules will be put into
service automatically as the flow rate increases. Each screening/
flotation module is capable of a 507. hydraulic overload without a
significant decrease in efficiency. This excess capacity will be
utilized after all modules have been put into service. The solids
removed from the flow will be stored or transported to the sewage treat-
ment plant via an inceptor sewer. As the raw flow subsides various
modules will be removed from service automatically until the overflow
is terminated. The system is thus a floating system with modules auto-
matically put into or taken out of service as required.
Based on the data taken during 30 overflows, Figure 9 presents
the recommended design criteria for screening and dissolved-air
flotation systems treating combined sewer overflow. This criteria is
tentative, since the project has not yet been completed. The most
important criteria associated with screen design include hydraulic
loading and solids loading. The recommended values are those which
134
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SKIMMER SYSTEM
SCREEN
CHAMBERS
RAW TUMPING
SYSTEM
FLOTATION
CHAMBERS
PRESSURIZED
FLOW SYSTEM
FIGURE 8
SYSTEM LAYOUT
-------
FIGURE 9
RECOMMENDED DESIGN CRITERIA FOR SCREENING AND FLOTATION
Screens Flotation
Media - 50 x 50 (297 Micron Openings) Surface Loading - 3 gpm/sq ft][
Hydraulic Loading - 50 gpm/sq ft Horizontal Velocity - 3 fpm
Head Loss Capability - 14 inches water Pressurized Flow - 15%
Solids Loading - 1.4 # DS/100 sq ft Operating Pressure - 50 psig
Cleaning Water - 0.75% Screened Flow Floated Scum Volume -0.95% of Flow
Provisions for Top and Bottom
Skimming
Chemical Flocculant Addition
(1) This value may be conservative, higher values now being tested.
were found satisfactory in the operation of the Hawley Road facility.
With regard to the flotation design criteria, the surface loading
variable is the only one which has not been fully evaluated. Higher
rates are now being investigated, and the affect of these rates on
removal efficiencies will be evaluated. The other criteria for
flotation shown in Figure 9 have been thoroughly evaluated and
proven adequate for combined sewer overflow treatment.
ESTIMATED COSTS OF SYSTEM
There are many factors which must be considered when estimating
costs for a combined sewer overflow treatment system. The basic
areas of consideration are listed below:
1. Screening/flotation system (based on a particular storm
intensity/frequency and runoff rates)
2. Variable rate pumping system
3. Solids storage and/or disposal
4. Land costs
5. Sewer interconnection costs (It is anticipated that a
number of overflow points will be combined to reduce the
number of treatment sites required.)
6. Instrumentation and data telemetry
Estimated costs discussed herein include those costs associated
with items 1, 2, 3 and 6 listed above. Items 4 and 5 are particular
to the individual treatment system and hence cannot be estimated in a
general manner. These costs are therefore not included here. Total
installed cost for the screening/flotation system is estimated at
i?8,000 per MGD capacity. Installed costs for solids storage, variable
rate pumping system and instrumentation is estimated at §4,000 per MGD
capacity. The total system costs less sewer interconnection and land
136
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cost is therefore $12,01)0 per MGU capacity. This cost estimate does
not include consulting engineering fees nor cost of special design
considerations if they are required. This cost is based on an over-
flow rate of 3 gpm/sq ft. If higher overflow rates are possible
costs will be reduced.
A conceptual design and cost estimate has been made for a complete
storm overflow treatment system in a small Wisconsin city. A number of
overflow points were combined to reduce the number of treatment sites.
All storm sewers were screened and all combined sewer overflows were
treated by screening/flotation. A total of 294 acres was served by
the system and the design was based on the once in two year storm. At
a 502 overflow capacity the system will handle the once in 4.5 year
storm. Total system costs including installation was $835,000. Total
treatment capacity was 80 MGD design and 120 MGi) peak flow. Of this
80 HCD approximately 40 MGU is combined overflow and the remaining
is storm sewer overflow. Included in this cost was the combining of 12
overflow points into 5 treatment sites. The cost estimates also
include engineering fees. All land was owned by the city so no
land costs are included in these prices. The above prices stated
on a per acre served basis is equivalent to about $2800/acre.
Operating costs for a screening and flotation system will be low
due to the expected periodic usage when treating combined overflow.
Chemical costs should be in the range of 2.0 to 2.be/1000 gallons,
while operating, maintenance and power costs are expected to be less
than l.OC/1000 gallons.
137
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1. Mason, D. G. , "Interim Summary Report FW\'A Contract #14-12-40,"
July
2 . Standard Methods for the Examination of Water and Wastewater ,
12tu Edition, American Public Healtn Association.
3. Christensen, Ralph, Private Communication, t'WQA, Chicago, Illinois.
4. Gannon, J. and Streck., L. , "Current Developments in Separate
Versus Combined Storm and Sanitary Sewage Collection and Treat-
ment," Presented 42nd Michigan WPCA Conference, June 1^67.
138
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SECTION 5
UNDERFLOW PLAN
FOR
POLLUTION AND FLOOD CONTROL
IN THE
CHICAGO METROPOLITAN AREA
STATE OF ILLINOIS
DEPARTMENT OF PUBLIC WORKS AND BUILDINGS
WILLIAM F CELLINI, DIRECTOR
METROPOLITAN SANITARY DISTRICT
OF GREATER CHICAGO
BEN SOSEWITZ, ACTING GENERAL SUPERINTENDENT
CITY OF CHICAGO
DEPARTMENT OF PUBLIC WORKS
MILTON PIKARSKY, COMMISSIONER
MAY, 1970
139
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ABSTRACT
To solve the problems of flooding and water pollution
in the Chicagoland area, a number of plans have been proposed
and studied. Three of these plans, the Underflow-Storage Plan,
the Deep Tunnel Plan and the Chicago Drainage Plan, are still
viable alternates for the total solution to meet the water
quality standards established by the State and Federal Govern-
ments and the requirement of handling the runoff from a
100-year storm.
During the study of the Underflow-Storage Plan, it
was decided to modify a large relief sewer proposed by the
City of Chicago,as an Underflow Sewer similar to the Metro-
politan area-wide plan but on a much smaller scale. The
Underflow Sewer would be constructed in solid rock, 250 feet
below the ground surface. This sewer is now under construction
with a portion being funded by a demonstration grant from FWQA.
Two additional Underflow Sewers are also under construction by
the Metropolitan Sanitary District at widely separated locations
in the Chicago area in the same dolomitic limestone rock form-
ation. Each of the three Underflow Sewers are being mined by
a machine of different manufacture. The construction of these
Underflow Sewers has confirmed the structural integrity and
the dense impermeability of this underlying rock blanket
throughout the entire Chicago area.
Further evaluation of the three plans indicates that
portions of the Underflow-Storage Plan designated for the First
Phase construction are compatible with future extensions along
the general conceptual lines of any of the three plans. It
is recommended that the final design of the First Phase work
proceed and that all alternates for the Second Phase be
thoroughly and systematically studied concurrently to deter-
mine the final plan. It is necessary to proceed at the earl-
iest possible time to meet the water quality compliance date
of 1978.
141
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TABLE OF CONTENTS
Page
ABSTRACT 141
LIST OF FIGURES 145
LIST OF TABLES 147
DRAINAGE AND POLLUTION PROBLEMS
IN METROPOLITAN CHICAGO 149
THE FLOOD CONTROL PROBLEM 149
THE WATERWAY POLLUTION PROBLEM 151
POSSIBLE SOLUTIONS FOR THE FLOOD CONTROL
AND WATERWAY POLLUTION PROBLEMS 155
SEPARATION OF SEWERS 155
STORAGE IN EXISTING SEWERS 155
UNDERFLOW-STORAGE PLAN 156
DEEP TUNNEL PLAN 156
CHICAGO DRAINAGE PLAN 157
DEMONSTRATION GRANT BY FWQA FOR THE
LAWRENCE AVENUE UNDERFLOW SEWER SYSTEM 159
COMPUTER STUDIES I63
HYDRAULIC MODEL STUDIES 166
CONSTRUCTION 166
RECOMMENDED SOLUTION TO THE PROBLEMS OF
FLOODING AND POLLUGION 178
INTRODUCTION I78
STORAGE-ENTRAPMENT STUDIES 178
PRESENT STATUS OF PLAN FOR POLLUTION
AND FLOOD CONTROL 179
COMBINED UNDERFLOW-STORAGE PLAN 179
COMBINING STORAGE WITH CONVEYANCE 184
UTILIZATION OF SURFACE WATERWAYS 190
RESIDUAL DIRECT SPILLAGE TO WATERWAYS 191
HYDROLOGIC ANALYSIS OF TWO MAXIMUM STORMS 192
POLLUTION MODEL OF THE MAINSTREAM SURFACE
WATERWAY I95
PROTECTION OF GROUNDWATER AQUIFERS 199
PROJECT COST 203
143
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TABLE OF CONTENTS (cont.)
CONSTRUCTION PHASES 211
RECOMMENDED FIRST PHASE CONSTRUCTION 211
SECOND PHASE STUDY 213
SUMMARY AND CONCLUSION 215
ACKNOWLEDGEMENTS 217
BIBLIOGRAPHY 218
144
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LIST OF FIGURES
Paqe
1. Growth in Capacity of City Outlet Sewers 150
2. D.O. Averages Upper Illinois River System 153
3. Drainage Area, Eastwood-Wilson Avenue and/or
Lawrence Avenue Sewer Systems 160
4. Lawrence Avenue Underflow Tributary 162
5. Typical Drop Shaft 167
6. Photograph of Lawrence Manufacturing Tunnel
Mining Machine 169
7. Photograph of Lawrence Avenue Underflow
Sewer Showing Mined Rock 170
8. Relation Between Volume of Entrapment
Facilities and Percent of B.O.D. Trapped 180
9. Waterway Improvements Between Brandon Rd.
and Sag Junction 182
10. Map Showing Flood and Pollution Control
Facilities For Combined Underflow-Storage Plan 185
11. Profile of Main Conveyance Tunnel 186
12. Profile of Calumet Conveyance Tunnel 187
13. Arrangement and Section of Main Tunnels 188
14. Overflow to Mainstream from Combined Sewers
After Exceeding the Underground Storage
of 12,000 Acre-feet 193
15. Analysis of Ultimate Runoff From 300 Square
Miles of Combined Sewer Area, and the Operation
of Underflow Storage Tunnels For a Future
Recurrence of the Oct. 9-10, 1954 Storm 196
145
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LIST OF FIGURES (cont.)
16. Analysis of Ultimate Runoff From 300 Square
Miles of Combined Sewer Area, and the
Operation of Underflow Storage Tunnels For a
Future Recurrence of the July 12-13,1957
Storm. 197
17. Dissolved Oxygen Sag Curves For Recurrence of
Storms Causing Spillage to Mainstream Up-
stream of Lockport 209
18. Study of Exfiltration of Water Due to Internal
Surcharge in Tunnel System During Storm
Periods 204
19. Relation Between Water Levels in Tunnels and
Adjacent Groundwater Levels During Maximum
Storage Period 205
20. Cost of Rock Excavation and Disposal vs.
Size of Tunnels, Without Lining 207
146
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LIST OF TABLES
1. Performance Comparison, Lawrence Avenue
Underflow Sewer - Existing Conventional
Sewers in Area 165
2. Pertinent Data for Lawrence Ave. Sewer
System,Contract No. 1 l71
3. Pertinent Data for Underflow Sewers Being
Constructed by MSDC 175
4. Storage Volume in Main Tunnels 183
5. Estimated Duration, Volume and B.O.D. of
Spillage at Combined Sewer Outlets and
Underflow to Lockport Assuming Recurrence
of Years of Record (1949-64, Inclusive)
and 12,000 Acre-feet of Mainstream Under-
ground Storage
6. Estimated Dissolved Oxygen Conditions in
Mainstream During Severe Storm Periods 198
7. Quantities of Rock Excavation 208
8. Estimated Contract Cost of Tunnels 209
?i n
9. Summary of Project Cost
147
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DRAINAGE AND POLLUTION PROBLEMS
IN METROPOLITAN CHICAGO
THE FLOOD CONTROL PROBLEM
Since the end of the Second World War, Metropolitan
Chicago has undergone a period of extensive urban development.
This development has caused a tremendous increase in the im-
pervious area and larger surface runoff during storm periods.
To alleviate local flooding of basements and underpasses
throughout Chicagoland, hundreds of millions of dollars have
been expended in the construction of new sewerage. While
greatly reducing the undesirable storage of water in basements
and underpasses, a new and increasing problem of flood control
in the rivers and canals is becoming apparent.
During the heavy storm period of October 9-11, 1954,
the Union Station and other downtown buildings were flooded.
To reduce the flood stage in the river, the locks at the
mouth of the Chicago River were opened allowing polluted water
to enter Lake Michigan. This was the first time since the
locks were constructed in 1938 that they were opened to permit
river water to flow into the lake.
Since that time the locks have been opened during
storms of July 12-13, 1957, September, 1961 and August, 1968.
The frequency of requiring lock openings to the Lake for river
flood control is greatly increasing, and will continue to in-
crease as new outlet sewer capacity is added.
The normal and desirable outlet for all storm water
is to the southwest along the Sanitary and Ship Canal to Lock-
port, the DesPlaines River through Joliet to the confluence of
the Kankakee River and through the Illinois River Waterway
System to the Mississippi River.
The Sanitary and Ship Canal designed for a capacity
of 10,000 cubic feet per second was completed in 1900. Be-
cause of drawdown of the water surface at Lockport during
heavy storms, the Canal has been able to handle a peak dis-
charge, for short periods of time, of up to 24,000 cfs.
Figure 1, shows the accumulated growth of outlet
capacity of sewers in the City of Chicago. The total pro-
jected outlet capacity of 65,000 cfs will be reached in 1975.
149
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70
60
GROWTH IN CAPACITY
OF
CITY OUTLET SEWERS
65)000 c.f.s
1975
•
MOUTH OF RIVER
9-7-38
SANITARY 8 SHIP CANAL~7
I860
1980
FIGURE 1
150
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This, of course, is not the required capacity of the waterway
system because of channel storage and offsetting of the sewer
discharge peaks; however, it is a good indicator of the future
flood control problems that lie ahead.
The DesPlaines River north of Hofmann Dam in River-
side has inadequate capacity to drain its fastly urbanizing
tributary area. Large storage reservoirs and/or increased
conveyance capacity must be provided to handle the increasing
runoff.
In the Calumet Area, large acreage is only a few
feet above normal water level of the calumet River and water-
way systems. In many places this provides only small gradients
for the tributary streams and sewer. During large storms, the
O'Brien Locks must be opened permitting river water to flow
through the Calumet River to Lake Michigan. But even this will
not keep the stage sufficiently low in the largest storm periods,
THE WATERWAY POLLUTION PROBLEM
The pollution of the waterway system is another vital
problem confronting the Chicago Metropolitan Area. This same
problem exists for nearly every other large metropolitan area
in the Country. Most of these urban concentrations are drained
by systems of combined sewers which spill to the open water
courses when the sanitary intercepting sewers or treatment
plants are overloaded.
Combined sewers have been estimated to carry approx-
imately 3 percent of the annual sewage volume to the waterways
during storm overflow periods, thus 97 percent of the annual
sewage volume is delivered to the treatment plants. The actual
annual pollution load which is discharged from combined sewers
to the waterways is somewhat greater. This is due to the
cleansing of the sewer inverts during periods of high storm
runoff.
In addition to the pollution of the river caused by
the combined sewer systems, other major contributors are the
sewage treatment plants. Three major treatment plants handle
the household and industrial wastes for the City of Chicago
and much of the suburban area within the Metropolitan Sanitary
District. These plants are the North Side Treatment Works,
the West-Southwest Treatment Works and the Calumet Treatment
Works.
151
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The U.S. Public Health Service study, "Great Lakes,
Illinois River Basin Project" (1) (GLIRBP) in two separate
periods of study in 1961 found the combined effluent of the
three plants was 1238 and 1682 MGD; at a population equivalent
(PE) of 969,000 and 793,000; which is equal to 78.2 and 66.2
tons of 5 day B.O.D. per day, respectively. The average over-
all efficiency for these two periods was 88.3 percent. The
reduction in the effluent PE during the second period was
attributed to the heavy rainfalls occurring during that period
resulting in the direct overflow of pollutants to the water-
courses by combined sewers and therefore not measured at the
plants.
Extensive sludge deposits are formed in the water-
ways downstream of the treatment plants and the many large out-
fall sewers. These sludge deposits have a significant oxygen
demand and thereby use up a large part of the natural oxygen
content in the waterways. At many places where these large
sludge deposits occur, gaseous bubbles are released to dot the
water surface and result in extensive odors along the river
channel.
Other sources of pollution of the rivers are the dis-
charges from industries, and leakage from boats and barges. In-
dustries also use river water for cooling purposes increasing
the temperature by several degrees; this reduces the amount of
dissolved oxygen the water can hold.
The dissolved oxygen (DO) is one of the most import-
ant constituents of the waterway system. All of the above
sources of pollution tend to deplete the dissolved oxygen.
Figure 2 shows the DO in the North Shore Channel, Chicago River,
Sanitary and Ship Canal and the DesPlaines River to the conflu-
ence with the Kankakee River for the two most critical months
of the year. The DO at Wilmette near saturation during this
period, shows a marked reduction below the North Side Treatment
Works, down to near one mg/1 just upstream of the main stem
of the Chicago River where fresh lake water is introduced.
The replenished DO is quickly reduced by the B.O.D. present in
the water plus that of the sludge deposits on the bottom. Be-
low the West-Southwest Treatment Plant, considerable DO is
added along wth the B.O.D. in the effluent from the plant.
The DO continues to diminish to near zero along the Sanitary
and Ship Canal to Lockport. Aeration at Lockport and the flow
from the DesPlaines River adds to the DO. Again at the Brandon
152
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LEGEND
JULY, 1961 '
AUGUST, 1961 — — — -
D. 0. AVERAGES
UPPER ILLINOIS RIVER SYSTEM
AS TAKEN BY
DEPT. OF HEALTH, EDUCATION 8 WELFARE
PUBLIC HEALTH SERVICE
i i
340 336 33O
3OO 395 29O 285 28O 275 27O
RIVER MILES ABOVE GRAFTON
MICH. N-SHOfti CM. N.BH.CHOO.H- SO •*.
••f*: • -* • •"*• *
IANITARY « SHir C AMAl
Ott riAINII RIVI*
III. R.
-------
Road Dam, additional DO is entrained. Almost complete re-
covery is reached, to the saturation point, after confluence
with the large quantity of good water from the Kankakee
River.
The low dissolved oxygen throughout much of the
length of the waterway system indicates the poor condition,
especially in the summer season. Insufficient DO is avail-
able to support desirable fish and aquatic life in the
stream.
The GLIRBP study has shown that the Waterway Sy-
stem through Chicago and downstream to the Kankakee River is
in an extremely polluted condition and can be considered as
a hazard to human health.
154
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POSSIBLE SOLUTIONS FOR THE FLOOD CONTROL
AND WATERWAY POLLUTION PROBLEMS
A number of alternates have been studied for solv-
ing the problems of waterway pollution caused by the spill-
ages from combined sewers. Also for solving the problems of
flood control of the waterways during severe storm periods.
Among those advanced are the following:
SEPARATION OF SEWERS
A complete study of the separation of sewers has
been made for the 300 square mile area of Chicago and vic-
inity , and would require nearly ten thousand miles of san-
itary sewers, many lift stations and interceptors. It has
been estimated that the cost of this separation would be in
the range of 3% to 4 billion dollars.
Even if separation were to be accomplished at this
tremendous cost, and with its concomitant disruption of
traffic in almost every street, the inconvience to all of the
people, the reworking of house and building plumbing, and
the adjustment and relocation of public and private utilities,
it is questionable as to whether it would solve the problems
associated with delivering all wastes to the treatment plants.
Accidental or illegal connections to the wrong sewer and the
possible leakage between sanitary and storm sewers, would make
policing of the six to eight mile long sewer systems impracti-
cal. In addition, it has been shown that storm water itself
carries considerable pollution to the waterways.
The separation of sewers would not provide any
flood benefit to the waterway system.
STORAGE IN EXISTING SEWERS
Consideration was given to storing the runoff of the
smaller storms in the existing sewer systems by the use of
inflatable dams. Such storage, if entirely used, would amount
to approximately 3,200 acre-feet or o.2 inches over the
192,000 acres of the combined sewered area. The entrapment of
combined flow for storms having a runoff of this magnitude
would result in a reduction of spillage of approximately 65
percent. This storage would reduce the frequency of combined
sewer spillages from an average of 60 per year to about 15
per year.
155
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However, because of the flat slope of the sewers
in the Chicago Metropolitan area, this method of reducing the
spillages was not further considered. The velocity generated
in the sewers in the post storm period would not be sufficient
to scour the sediment'deposited during the storage period, and
would result in extensive maintenance problems. Also, this
method would not contribute anything toward the solution of
the flood control problem.
UNDERFLOW-STORAGE PLAN
This plan proposes the construction of a pattern of
large tunnels in the dense Niagaran limestone rock formation,
200 to 300 feet below the surface waterway system. These
tunnels would be sized to provide a linear distribution of
storage volume and conveyance capacity in a pattern which would
intercept all of the approximately 400 outfalls of the exist-
ing combined sewers. The tunnels would be sloped down to low
points, and pumping facilities, opposite the existing sewage
treatment plants. Overflow from the combined sewers, during
storm periods, would drop through shafts to the large storage
tunnels. In the post storm period, the tunnels would be de-
watered by pumping directly to the existing treatment works.
The Underflow-Storage Plan takes advantage of the
lower water level to be established in the Illinois Waterway
at Lockport, Illinois, for improvement of navigation and
flood control of the waterway system. The new water level,
70 feet or more below the level of Lake Michigan, will allow
the construction of tunnels with large underflow conveyance
capacity to Lockport and provide flood protection for the
largest storm of record.
Storage of 18,000 acre-feet or 1.12 inches of run-
off in the tunnel system will provide 98.5% reduction of
pollutants entering the waterway from combined sewer spill-
ages.
Subsequent paragraphs will provide the details of
this plan.
DEEP TUNNEL PLAN (HARZA AND BAUER, CONSULTING ENGINEERS)
This plan is a multi-purpose plan, including hydro-
electric power development, with a "pumped-storage" scheme,
now widely used throughout the world as adjuncts to hydro-
power developments on surface streams or to thermal power
156
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plants. In the Deep Tunnel Plan, storage for hydro-power
would be provided in rock caverns, 600 feet or more below
the surface and in surface reservoirs above ground in the
vicinity of the underground caverns. Reversible pump-gen-
erator units would be used intermittently to move water up-
ward and to develop power during downflow. Power would be
generated and sold to the Commonwealth Edison Company daily
during the hours of peak demand for electricity. Power would
be purchased for pumping, daily, during the periods of low
demand for other uses in the Metropolitan area. Based on an
estimated net revenue, in excess of cost of operation, revenue
bonds would be sold by the Metropolitan Sanitary District to
provide capital for a portion of the multi-purpose project.
The underground caverns and the surface reservoir
would be over-sized beyond the needs for power development to
provide for entrapment and storage of excess spillage from the
combined sewer outlets. Primary sedimentation would be pro-
vided underground at the entrance to the caverns, and the sed-
iment pumped to the existing treatment works. Controlled out-
flow from the surface storage would also be directed to the
existing major treatment works.
The total volumes of the proposed multi-purpose
storage is 35,000 acre-feet below ground and 45,000 acre-feet
above ground, or a total in the system of 80,000 acre-feet, of
which 20,000 acre-feet was considered to be normally needed
for power development, leaving 60,000 acre feet normally avail-
able for pollution and flood control.
The tunnel system to deliver the combined sewer
spillage to the storage and power development site or sites
would be generally of the same pattern as for the Underflow
Plan, with an interconnecting tunnel through Chicago's south-
side connecting the Mainstream and DesPlaines Tunnel System
to the Calumet Tunnel System.
Two locations for storage and power development are
presented; one near the Calumet Treatment Works, and one
near the West-Southwest Treatment Works.
CHICAGO DRAINAGE PLAN (ILLINOIS DIVISION OF WATERWAYS)
This plan presented in a preliminary report in Nov-
ember, 1968, combines navigation, flood control and pollution
157
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control in the areas tributary to the Illinois Waterway up-
stream from Brandon Dam.
For flood control in the Lockport-Joliet Area, as
well as for improved navigation, it is proposed to remove the
Brandon Road Dam and Locks, and the existing Lockport Dam,
Lock, and Controlling Works; to build new twin locks, dam
and controlling works about two miles upstream from the exist-
ing Lockport Dam; and to deepen and widen the channel from
Brandon Road to the new Lockport Locks, so as to lower water
levels in this reach, about 34 feet below present water levels.
Upstream from the new Lockport Dam, the Sanitary and
Ship Canal would be widened to 325 feet, with 150 feet of this
width to be deepened 10 feet. The Lockport Dam would be de-t
signed to maintain dry weather water levels above Lockport, 10
feet lower than at present.
The widening would extend to Willow Springs Road
and the 10-foot lowering of the surface water levels would
extend along the Calumet-Sag Channel and Little Calumet River
to the O'Brien Lock and Dam and along the Sanitary and Ship
Canal to Throop Street. A new dam and lock would be built at
Throop Street with a 10-foot differential head, and the O'Brien
Lock and Control Works rebuilt to accommodate the lowered
water surface.
For pollution control, the Division of Waterways
proposed the installation of storm water detention and sed-
imentation tanks at combined sewer outlets. These would be
of the flow-through type and would discharge all flows in
excess of tank volumes as partially settled combined sewage
into the surface waterways. Solids which settled in the tanks,
together with the liquid retained at the end of each storm-
water runoff period would be drained or pumped into the inter-
cepting sewers of the Metropolitan Sanitary District. Screen-
ing and chlorination at the tank locations as well as mobile
aeration of the waterways might be added to improve the
pollution control.
158
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DEMONSTRATION GRANT BY FWQA FOR
THE LAWRENCE AVENUE UNDERFLOW SEWER SYSTEM
In 1966, the City of Chicago proposed a sewer project
which would demonstrate the principles of the Underflow Plan
but, of course, on a much smaller scale.
The City of Chicago's Five Year Capital Improvement
Program called for the construction of a new Auxiliary Outlet
Sewer System to provide relief from basement and underpass
flooding of an area bounded by the North Branch of the Chicago
River, Irving Park Road, Oriole Avenue and Devon Avenue. (See
Figure 3 ). Preliminary hydraulic studies indicated that a
trunk sewer in the vicinity of Wilson Avenue from the North
Branch of the Chicago River to Melvina Avenue with branches
extending north and south to intercept and unload existing
trunk sewers would provide the necessary flood relief for a
direct drainage area of 3,620 acres.
The proposed sewer system in that program was des-
ignated the Eastwood-Wilson Avenue Sewer System and varied in
size from a 2 barrel 13-foot by 13-foot section at the lower
end near the river to a 7.5-foot circular section at its upper
end.
Consideration was given to lowering the profile of
this sewer to increase the storage available during small
storm periods and to cause it to flow full before discharging
to the river. The storage thus generated would reduce the fre-
quency of spillages from this combined sewer to the river.
Lowering the profile would necessitate pumping of sewage to
the existing sanitary intercepting sewer, increasing the over-
all cost. It would also require that more of the construction
be performed by earth tunnel method. Recent development of
earth mining machines has resulted in lower bid prices in
earth tunnel contracts. However, preliminary soil investigations
indicate that heavy primary steel lining and occasional rock
sections would negate the savings from the use of such machines.
Costs would greatly exceed that of the conventional open cut
construction method.
Recent improvements of the rock mining machines (Moles)
have reduced the cost of tunneling in various kinds of rock
materials for large irrigation and hydroelectric projects
throughout the world. Preliminary cost estimates revealed that
mining in rock may be competitive with open cut methods.
159
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NORTH 1101
TMATM1NT PIANT
\ Vn t
'^zM V^
-------
Lowering the profile of the Eastwood-Wilson sewer
over one hundred feet into bed rock and constructing it as an
"Underflow Sewer" looked promising. Sanitary flow would not
normally, in dry weather periods, enter the tunnel and there-
fore would not be pumped on a continuous basis. Pumping would
be required, however, for dewatering of the tunnel to the
existing sanitary intercepting sewer in the post rainfall
period.
The Department of Public Works retained the Harza
Engineering Company to study alternate methods of constructing
the proposed Eastwood-Wilson Auxiliary Outlet Sewer System.
The studies were to include a comparison of costs of construct-
ing the sewer by open cut and tunnels, the maintenance and
operating costs, and their recommendations on the best method
to fit the City's needs.
It was decided to construct a lined tunnel sewer in
the Niagaran limestone formation approximately 250 feet under
the surface of Lawrence Avenue and demonstrate the feasibility
of the "Underflow" concept. See Figure 4. The rock tunnel
would be excavated by a tunnel boring machine. Lawrence Avenue,
an arterial street, was selected as the route of the sewer be-
cause of the requirement of the mole to travel in nearly a
straight line. Because the tunneling would be so far below
the surface, traffic in that arterial street and commercial
activities would not be interrupted, as would be the case with
the conventional open cut construction.
The tunnel would be 12,800 feet long at 12 feet in
diameter and 9,300 feet long at 17 feet in diameter. A branch
tunnel in Harding Avenue extending south' from Lawrence Avenue
to Berteau Avenue, a distance of 4,000 feet would also be
12 feet in diameter. Approximately 18,000 feet of new con-
ventional branch sewers would relieve the overloaded existing
sewers and convey the flow to the tunnel inlet shafts. Ten
inlet shafts would be constructed to supply the tunnel and one
25-foot diameter outlet shaft for the discharge drainage.
The total storage in the tunnels and shafts will be
about 4,000,000 cubic feet or about 0.30 of an inch over the
3,620 acre drainage area. This storage would provide space
for the runoff from rainfall accumulation up to about 0.9
inches without overflowing to the river.
161
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UNDERFLOW PLAN
40
•••UNOftriOW SIWII
••••MlOM-lIVil MIDI* tfttU
LAWRENCE AVENUE
UNDERFLOW TRIBUTARY
FIGURE 4
162
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COMPUTER STUDIES
In order to analyze the Lawrence Avenue Underflow
sewer system under actual operating conditions, a mathematical
model of the system was simulated in a computer program. Each
hour of rainfall during an entire year was analyzed. The
amount of rainfall along with the corresponding hourly code
was recorded on punched cards. The computer was programmed to
determine the net runoff from the impervious and pervious
areas for each hour of rainfall. For the impervious area,
a small amount of depression storage was subtracted from the
first hours of rainfall of each storm to obtain the net runoff
supply. On pervious areas, depression storage and varying
amounts of infiltration depending on wet or dry antecedent
conditions were subtracted from the rainfall to determine the
net runoff supply. The total runoff was then calculated by
weighing the net runoff supply from the impervious and the
pervious areas in accordance with the imperviousness ratio of
the tributary drainage area.
A hydrograph with a mass equal to the net runoff
supply was then developed. The base of this hydrograph can be
varied for the time of concentration of the tributary sewer
system. The hydrographs for adjacent hour periods having a
net runoff supply were then added together, somewhat similar
to the method used in summing the unit hydrographs in river
hydrology.
Sanitary flow was added to these runoff hydrographs
to obtain the combined flow hydrographs for every rainfall
period of the year. For this study 0.01 cubic feet per second
per acre was used as the sanitary flow rate. This rate has
been verified as a good approximation for the quantity of
sanitary flow by the U.S. Public Health Service studies on the
Roscoe Street sewer system which serves a similar drainage
area.
At each overflow point of the existing sewer system,
it was assumed that up to two times the dry weather flow
would continue to flow by the overflow weir and along its
present route to the treatment plant. The excess flow over
and above two times the dry weather flow spills down into
the tunnel system.
163
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The sanitary flow at these overflow points is
assumed to be uniformly mixed in the total combined flow up-
stream of the controlling weir. Four factors were set for
the pollutional load in the combined flow. These included
suspended solids in sanitary sewage, suspended solids in
storm water, B.O.D. in sanitary sewage and B.O.D. in storm
water. The sewer was sized for only its necessary convey-
ance capacity to handle the calculated runoff from a five-year
frequency on its tributary drainage area.
A graph of the storage volume was plotted against
the water surface pool elevation in the tunnel. This data was
placed in the computer with linear interpolation between sets
of points. When the volume of inflow to the tunnel exceeded
the total storage volume, the excess water was discharged to
the river. Limitations were placed in the program, on the max-
imum discharge flowing through the system, since storms ex-
ceeding the design capacity of the existing sewer system and
the new tunnel system would cause upstream basements to flood.
This flooding would limit the maximum discharge through the
system. This eventuality was provided for in the computer by
flood routing procedures and limiting the maximum discharge to
1,500 cfs.
A set time after the last hour of rainfall of a
storm period, the dewatering pumps were turned on. The pumps
were set at 48 cubic feet per second which would provide com-
plete dewatering of the tunnel to the interceptor in 24 hours.
The B.O.D. in the tunnel was assumed to be pumped
to the interceptor or to overflow to the river at the instan-
taneous concentration in the system. The suspended solids
were divided into two parts, that which would remain in sus-
pension and that which would settle as a function of tunnel
velocity. That portion which remained in suspension was
pumped during dewatering or overflow to the river at the in-
stantaneous concentration in the system. The volume of sus-
pended solids that settled to the bottom was assumed to be re-
moved by flushing and pumping after the tunnel was dewatered.
Table 1 shows the results summarized for five years
of records using the rainfall as it occurred at Midway Airport,
U.S. Weather Bureau Gage for 1956 to 1960 inclusive.
164
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Table I
PERFORMANCE COMPARISON
LAWRENCE AVENUE UNDERFLOW SEWER - EXISTING CONVENTIONAL SEWERS IN AREA
A Summary of Computer Calculations Based on Hourly Precipitation Records for 5 Years Period 1956 - I960
CRITERIA
HOURS OF PRECIPITATION
TOTAL PRECIPITATION (Inches)
EXISTING CONVENTIONAL Number
SEWERS IN AREA Duration (Hrs .)
OVERFLOW TO RIVER Suspended
Solids (Lbs.)
B.O.D. (Lbs.)
LAWRENCE AVENUE Number
UNDERFLOW SEWER Duration (Hrs .)
OVERFLOWS TO RIVER Suspended
Solids (Lbs.)
B.O.D. (Lbs.)
REDUCTION (Percent) Number
IN OVERFLOWS DUE TO Duration Hrs.)
LAWRENCE AVENUJL Suspended
UNDERFLOW SEWER Solids (Lbs.)
B.O.D. (Lbs.)
MAXIMUM STORAGE TIME Hours
IN TUNNEL - STARTING
DEWATERING PUMPS Days
4 HOURS AFTER RAINFALL
(PUMP CAPACITY - 48 GFS)
1956
446
Z2.23"
52
156
557,400
81 ,600
4
9
73,600
11,3 00
92%
94%
87%
86%
87
3.6
1957
631
44.29"
79
336
1,882,500
236,000
6
22
763,300
75,900
92%
93%
60%
68%
70
2.9
1958
456
26.35"
55
183
840^900
114,700
6
17
156,200
20,300
89%
91%
81%
82%
63
2.6
1959
631
38.68"
61
282
1,406, 100
182,700
4
15
542,300
52,000
93%
95%
61%
72%
68
2.8
I960
547
27, 84"
47
218
877.700
124,200
6
25
199,400
25, 100
87%
89%
77%
80%
89
3.7
5 Year
Average
542
32"
59
235
1,112,900
147,800
.5
18
347JOOO
36,900
91%
92%
73%
78%
75
3. 1
Prepared by:
The City of Chicago, Department of Public Works, Bureau of Engineering
-------
HYDRAULIC MODEL STUDIES
Ten drop shaft structures were required to connect
the existing high level sewers and the connecting sewers to
the rock Underflow Tunnel. These drop shafts were all slight-
ly over 200 feet in length. Harza Engineering Company and the
St. Anthony Falls Hydraulic Laboratory were retained to study
and test various configurations with the aid of models, and to
determine the best method to destroy the energy of water fall-
ing this distance. Another problem to be studied with the
computer and a hydraulic model was the surges that may result
when the fast filling tunnel suddenly becomes full during
large storms.
The final drop shaft configuration is shown in
Figure 5. This scheme uses a slotted wall with one side for
water and the other air, during low tail water. The slots in
the wall suck in air to be mixed with the water. This air-
water mixture having a much lower density, greatly reduces the
impact on the bottom. A large chamber or tumbling basin permits
the water and air to separate before the water enters the
tunnel.
During heavy storms after the tunnel is full and high
tail water exists, the water flows down both sides of the shaft
so as to reduce the hydraulic losses through the structure.
CONSTRUCTION
The Lawrence Avenue Underflow Sewer System was pro-
posed to be constructed under several contracts. The first con-
tract was for the outlet shaft near the river, 9,126 feet of
17-foot and 16,638 feet of 12-foot concrete lined rock tunnel.
Soil borings and rock cores showed that the dolomitic limestone
rock was very dense and at the level of the tunnel, little water
problems were expected.
Contract Number 1 was awarded to the low bidder in
November 1967 at a price of $10,792,094. This cost was to be
financed with $1,500,000 from a Federal Water Quality Adminis-
tration grant and the remaining from the City of Chicago's
Sewer Bond Program.
166
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VENT
CHAMBER
HIGH
LEVEL
SEWER
OPEN GRATING and ENTRANCE MANHOLE
MAINTENANCE
MANHOLE
SLOTTED
WALL
DROP
SHAFT
TUMBLING
BASIN
TUNNEL
SEWER
\f
EXIT
CONDUIT
TYPICAL DROP SHAFT
167
FIGURE 5
-------
The contractor elected to use the mole designed for
the smaller 12-foot tunnel as a pilot tunnel for the 17-foot
and later enlarge it to full size by drill and blast methods.
A tunnel mining machine, built by the Lawrence Manufacturing
Company of Seattle, Washington, was used. The photograph of
the machine being placed in the tunnel is shown in Figure 6.
The actual cut of the machine is 13'-8" so as to allow for the
concrete lining. Figure 7 shows the very smooth walls of the
portion mined by the machine. A summary of pertinent data
for this contract is shown in Table 2.
An inspection of the mined portion of the tunnel
revealed that the bedrock consists essentially of a light gray
to gray massive fine grained dolomitic limestone with horizon-
tal clay partings. The horizontal clay partings probably re-
present bedding planes, and were partially obscured by the mach-
ine operation. Occasional areas were washed clean by seepage
from fractures and/or joints, and in these areas, the bedding
planes had an average thickness of about 1/4 inch to 5 inches.
There is no apparent opening or space along bedding planes
throughout the excavated portion of the tunnel as is evidenced
by the lack of obvious seepage of groundwater through the
bedding planes.
No faults occurred in the inspected area. The major
fractures and/or joints in the tunnel are basically vertical
and run in either a northeast to southwest or northwest to
southeast direction. The fracture and/or joint openings are
generally 1/8 inch to almost 1 inch thick. A grayish green
to green clay generally was found in the fracture and/or
joint openings.
As mentioned above, there was no apparent seepage
of groundwater from the bedding planes. Approximately 75 per-
cent of the fractures and/or joints had at least some water
seepage. Generally, the walls and ceiling of the tunnel were
damp. The quantity of seepage water which collected in the
tunnel amounted to only about 20 gallons/minute/mile.
During the construction of the first contract of
the Lawrence Avenue Underflow System, it was learned that the
mining machine had some difficulty maintaining line and grade.
This was caused by the pilot shaft at the front of the machine
which served to pull the machine along behind it. This problem
was later rectified when jacks were added behind the cutting
face of the second machine which was used.
168
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-
-------
- I
•
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TABLE 2
Pertinent Data For
LAWRENCE AVE. SEWER SYSTEM
CONTRACT NO. 1
Length of Tunnel:
In Lawrence Ave.
In Lawrence Ave.
In Harding Ave.
*9,126 feet of 15'-6V x 19'-5"
12,670 feet of 12 foot dia.
3,968 feet of 12 foot dia.
25,764 feet
*6,760 feet mined by machine
to 13'-8" and enlarged by
drill and blast method and
2,366 feet full face drill and
blast with finished section of
8" liner to dimensions of
15'-6%" x 19'-5".
Depth below Ground
245 feet max., 220 feet min,
Slope of Sewer
2.5 per 1000
O.S. Diameter specified: (Mined
by Machine):
In Lawrence Ave. (1st 9,126')
In Lawrence Ave. (2nd 12,670')
In Harding Ave. (3,968')
18' -4"
13' -4*
13'-4"
O.S. Diameter Actual:
In Lawrence Ave. (1st 9,126')
In Lawrence Ave. (2
In Harding Ave.
nd
12,670')
16'-10Vfx20'-9" D&B or enlarged
from machine bore of 13'-8".
13'-9" dia.
13'-9" dia.
I.S. Diameter:
In Lawrence Ave. (1st 9,126')
In Lawrence Ave. (2nd 12,670')
In Harding Ave. (3,968')
15'-6J5"xl9'-5" (lined)
12'-0" dia. (if lined)
12'-0" dia. (if lined)
Tail Tunnel
61 feet
Shaft
27 feet dia. and 256 feet deep
171
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TABLE 2 (cont.)
Pertinent Data For
LAWRENCE AVE. SEWER SYSTEM
CONTRACT NO. 1
Contract Costs (Bid):
1. Shaft
2. 12 foot dia. Tunnel
17 foot dia. Tunnel
3. 12 foot dia. Lining
17 foot dia. Lining
4. Rock Bolts
5. Wire Mesh
Total
$ 600,000
4,658.640
3,732,534
998,280
730,080
67,500
5,000
$10,792,094
Increased Storage (without cone,
lining in the 12' dia. section)
In Lawrence Ave. (west of
Sta. 91+50)
In Harding Ave.
Total
31% increase in Volume
16,610 cubic yards
5,202 cubic yards
21,812 cubic yards
Award Date
November 1, 1967
Term of Contract
1,095 days
Specified date of completion
November 5, 1970
Normal Shifts
24 Hours Mon. through Sat.
Progress to Date:
In Lawrence Ave.:
Machined mined (13'-8")
Drill & Blast Enlargement
Full Face Drill & Blast
In Harding Ave. (13'-9")
6,760 feet (1-31-69)
6,760 feet (9-22-69)
2,383 feet (Sta.91+43)(5-7-70]
2,710 feet (5-7-70)
Progress Max. Week
347 feet (3 shifts, week
ending 11-23-68)
Progress Max. Day
92 feet (2 shifts on 4-21-70)
Maximum Penetration ft./hr.
8.6 Maximum
Comp. Strength Rock p.s.i.
11,400 to 29,600
172
-------
TABLE 2 (cont.)
Pertinent Data For
LAWRENCE AVE. SEWER SYSTEM
CONTRACT NO. 1
Mining Machine:
Manufactured by
Thrust of Machine
Drive of Machine
Operation Voltage
Make of Bits
Number of Cutters
Dia. of Cutterhead:
Machine No. 1
Machine No. 2
Length of Machine:
Assembly
Drawbar
Power Train
Auxiliary Power Train
Total
Lawrence Mfg. Co.
1,300,000 lb.(Max.) 850,000 Lb.Op.
5-125 hp. Motors
480 Volts
Lawrence Mfg. Co.
29 Disc-Type with carbide inserts.
13'-8" dia. in Lawrence Ave.
13"-9" dia. in Harding and Lawrence
19 '-ll'-
lS'-11"
23i_7"
25'-4"
84'-9"
Tunnel Power Line
4,160 Volts
Conveyor System Manufacturer
Lawrence Mfg. Co. with a Good-
year Belt 24" wide by 84' long,
Muck Cars
Length of Train
Track Gauge
Locomotives
6 Cubic Yards
9 Cars
36"
10 Ton, Plymouth Diesel, 86 hp.
Ventilation
28" Vent line
2-40 hp Vent fans made by the
Joy-Axivane Co.
14,000 CFM each.
One 15 hp fan at street level
to prevent any line back pressures,
Contractor
J. McHugh Construction Co.
S. A. Healy Co., and Kenny
Construction Co.(a joint venture)
Resident Engineer
John Redmore
173
-------
The most significant causes of time delays in this
contract consisted of: the replacement of a burned-out trans-
former; replacement of burned out electrical cables and blown
electrical switches; replacement of cutting wheels, conveyor
rollers and muck buckets; repairs to the pilot shaft; and
removing the original machine and installing its modified
replacement.
In March, 1970, a second contract was awarded for
8,400 feet of earth tunnel, which will serve as the collect-
ing sewers to intercept critical relief points in the exist-
ing City sewer system. Sizes of these tunnels, to be con-
structed in medium to hard blue clay, range from 5 to 9% feet
in diameter. This contract went for $2,393,645 and will be
financed entirely by the City's Sewer Bond Program.
Another small contract for drilling three (3) mon-
itoring wells was let in August, 1969 at $45,805 to test the
groundwater quality and pressure at three levels of the aquifer.
This contract includes level recorders and sample pumping fac-
ilities.
Three more contracts are required to finish the
entire Lawrence Avenue Underflow System. These are for the
ten drop shaft structures, pumping stations and outfall stru-
tures, and at some future date a contract for additional collect-
ing sewers. After the completion of these contracts, the total
cost of the Lawrence Avenue Underflow System will be approximate-
ly $21,000,000.
Subsequent to placing the Lawrence Avenue Underflow
Sewer System under construction, two more large Underflow
Sewer Systems were started in the Chicago Area by the Metro-
politan Sanitary District of Greater Chicago. One of these is
a 15-foot diameter Underflow Sewer in Crawford Avenue from the
Calumet Sag Channel to 105th Street, a length of 18,300 feet.
The other is a 12-foot diameter Underflow Tunnel having a
length of 17,600 feet, and serving the LaGrange-Brookfield sub-
urban communities.
It is noteworthy that the three Underflow Sewers, all
being constructed in the same dense Niagaran limestone strata,
are being constructed by mining machines of different manu-
factures. Tables 2 and 3 show the pertinent data of the three
jobs.
174
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TABLE 3
Pertinent Data For Underflow
Sewers Being Constructed by MSDC
Lawndale Ave. & 47th
St. SWIS 13A
127th & Crawford
Ave. Calumet
18E-Ext. A
Length of Tunnel
Depth below ground
Slope of Sewer
O.S. Diameter Specified
O.S. Diameter Actual
I.S. Diameter (if lined)
Tail Tunnel
Shaft
Contract Costs Bid
1. Shaft 850,000
2. Tunnel 4,567,206
3. Lining 793,530
4. Bulkhead included
Total 6,210,736
17,634 feet
235 Max. 201 Min.
2.1 per 1000
13 '-4"
13 '-10"
12'-0"
250 feet
30' and 28'x206'
deep
Revised Bid
850,000 1,000,000
4,503,724* 4,763,200
0 1,190,476
above 1,000
5,350,724* 6,954,675
18,320 feet
223 Max. 216 Min.
1.5 per 1000
16 '-4"
16--10"
15 '-0"
260 feet
29' and 27'x223'
deep
Revised
1,000,000
4,763,200
0
1,000
5,764,200
* includes credit for rock
material and refund on Elec.
Agreement ($360/lin.ft.
credit on rock) .
Increased Storage
(without Cone, lining)
36% increase in
Volume 24,000
Cubic Yards
26% increase in
Volume 31,000
Cubic Yards
Award Date
Term of Contract
Specified Date of
Completion
Normal Shifts
Progress to Date
June 6, 1968
930 Days
Jan. 5, 1971
24 hrs. Mon. thru
Fri. 16 hrs. Sat.
5,845 ft. (1-7-70)
May 17, 1968
933 Days
Dec. 16, 1970
24 hrs. Mon.
thru Sat.
4,860 ft. (1-6-70)
175
-------
TABLE 3 (cont.)
Lawndale Ave. & 47th
St. SWIS 13A
127th & Crawford
Ave. Calumet
18E-Ext. A
Progress Max. Week
467 feet
480 feet
Progress Max. Day
113 feet
129 feet
Max. Penetration ft./hr,
5.5 avg. 7.2 max. 4.9 avg. 7.2 max.
Comp. Strength Rock psi.
15,000 to 24,900
23,500 to 39,000
Mining Machine
Manufactured by
Thrust of Machine
Drive of Machine
Operation Voltage
Make of Bits
Number of Cutters
Length of Machine
Dia. of Cutterhead
James S. Robbins &
Assoc. Inc.
890,000 Ib. (Max.)
6-100 hp motors
460 Volts
James S. Robbins &
Assoc. Inc.
27 Disc-Type
plus Tri-Cone
37 feet
13'-10"
Jarva, Inc.
2,200,000 Ib.(Max.)
8-125 hp motors
480 Volts
Reed Drilling
Tools
54 Reed Type OKC
Tungsten Carbide
insert
35 feet
16'-10"
Conveyor System
Manufactured by
Moran Eng. Co. Card Corp.
96' Bridge Con- 260' conveyor
veyor(20" widebelt) Supporting a
to 132'(18" wide 30" belt
belt)car loader
Muck Cars
Length of Train
Track Gauge
Locomotives
4.4 Cubic Yards
10 Cars
24"
10 Ton, Plymouth
Diesel, 70 hp
10 Cubic Yards
10 Cars
36"
15 Ton, Plymouth
Diesel, 160 hp
Ventilation
30" Vent line 36" Vent line
2-100 hp Vent fans Joy-Axivane fans
@ 12,000 CFM ea. 31,000 CFM max.
Contractor
S.A.Healy Company
& Kenny Cons. Co.
(a joint venture)
S.and M. Con-
tractors, Inc.
Resident Engineer
Geo. A. Taylor
Thomas P. Vitulli
Tunnel Power Line
7,200 Volts
7,200 Volts
176
-------
Although the mining machines have had considerable
problems in the 11,000 to 29,000 psi rock, they are now making
over 500 feet per week. There is no question that these
machines can perform in this type of rock. It is the writer's
opinion that the maximum size limitation in this rock will be
in the 20 to 25 feet diameter range for the next several years.
Sizes above 25 feet diameter, contemplated in the area-wide
Underflow Plan, will be constructed by the drill and blast
method.
The construction of these Underflow Sewer Systems
will demonstrate the feasibility of constructing, economically,
a detention reservoir to greatly reduce the pollution caused
by overflows from combined sewers, far below the surface in
public right-of-way, while providing the conveyance capacity
to reduce basement and underpass flooding. It will also dem-
onstrate the practicability of constructing a much enlarged
Underflow System beneath the waterways to serve the entire
300 square mile combined sewer area in the City of Chicago and
the surrounding Metropolitan Area. When the enlarged Underflow
System is completed, the Lawrence Avenue Underflow Sewer and
the two being constructed by the Metropolitan Sanitary District
will become branches to the trunk lines under the waterways.
At that time the pumping stations serving these three initial
Underflow Sewers will be abandoned.
177
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RECOMMENDED SOLUTION TO THE PROBLEMS
OF FLOODING AND POLLUTION
INTRODUCTION
Because of the urgency of meeting the water quality
standards, SWB-15, (2) established by the Illinois State San-
itary Water Board and approved by the Federal Government,
studies Were continued on the various solutions to the flood-
ing and pollution problems.
In February 1968, a Technical Advisory Committee of
prominent engineers in the field of sanitation and drainage
was established to review the several plans advanced for solv-
ing the pollution and flood control problems of the Chicago
Metropolitan Area. The Technical Advisory Committee was charged
with establishing criteria by which each plan would be eval-
uated, and finally to make recommendations to the Flood Control
Coordinating Committee on the plan or composite plan which would
be best suited to economically solve these problems.
Such a plan would be primarily aimed at solving the
pollution of the waterway system caused by the overflow from
combined sewers during rainfall periods and eliminating flood-
ing of the waterway in time of heavy storms. The plan must pro-
vide for meeting the criteria established by the State Sanitary
Water Board for each water course not only as to the quality of
water but as to time of implementation. The recommended plan
must be adequate to handle a recurrence of the greatest storm
of record without requiring the discharge of river or canal
water to Lake Michigan.
The final plan selected, although meeting the criteria
established for pollution abatement and flood control, should
be as broad and as multiple-purpose as possible. Such other
areas as recreation, esthetics, navigation and power generation
should be considered if economically justified.
STORAGE-ENTRAPMENT STUDIES
Since there was considerable difference of opinion as
to the effect of storage on entrapment of pollutants, a sub-
committee with members selected to represent the three principle
local agencies of the Technical Advisory Committee made some
detailed computer studies involving the relationship between the
volumes of underground storage (acre-feet) and the trap efficiency
(percent of total B.O.D. spillage that would be trapped in under-
ground storage).
178
-------
These computer studies resulted in the relationship shown in
Figure 8.
From this study, it appeared that the percent of en-
trapment varies greatly with the amount of storage until reach-
ing between 15,000 and 20,000 acre-feet when applied to the 300
square mile combined sewer area. Above 20,000 acre-feet, the
increase in entrapment is at a far slower rate per increment of
volume. If capital cost per acre-foot were constant for all
volumes, then to achieve a trap efficiency greater than 98 per-
cent might appear uneconomical and unwarranted. However, many
other compensating factors in the cost of providing such stor-
age volume must be carefully evaluated.
PRESENT STATUS OF PLAN FOR POLLUTION AND FLOOD CONTROL
The authors have generally agreed that the First Phase
Construction, to be outlined in the subsequent paragraphs of
this report, is compatible with the Metropolitan Sanitary Dis-
trict's, the City of Chicago's and the State Division of Water-
ways ' proposed plans. This is with the complete understanding
that as detailed design progresses on this First Phase, con-
veyance tunnel configuration, size, elevation, storage volume,
treatment of the overflows and locations may require some mod-
ifications to provide the most economical system. The exten-
sion of the underflow tunnel to the DesPlaines River at Lock-
port, lowering of the waterways for navigation and flood control,
or generating hydro-electric power to offset a part of the cap-
ital cost under the Second Phase work, require further eval-
uation.
The elected officials of the various agencies, however, have
not adopted the First Phase Construction, nor any of the
three plans as of this writing. Implementation of the projects
will depend on policies established and commitments made by
these agencies.
In the following paragraphs, the complete Underflow-Storage
Plan is presented only to provide the reader with the re-
lationship of the First Phase to the overall plan.
COMBINED UNDERFLOW-STORAGE PLAN
A modified form of the initial Underflow Plan pro-
posed in the 1966 report has been developed and is referred to
179
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<
ex
O
Q
O
6
WE I AREA, 31 0 Sq.-Mi.er 192,000 ACRES
) I I I L I 1 I I I I I I I I I I I I I i I I t I )
10,000 20,000 30,000 40,000 50,000 60,000
STORAGE IN ACRE MET
RELATION BETWEEN VOLUME
OF ENTRAPMENT FACILTIES
AND PERCENT OF B.O.D. TRAPPED
FIGURE 8
180
-------
as the Combined Underflow-Storage Plan.
Since the Illinois Division of Waterways has sol-
idified their recommendations regarding waterway improvements,
and have prepared specific recommendations and requested
action by the U.S. Corps of Engineers to reconstruct that
portion of the Illinois Waterway through Joliet. As already
stated, their recommendations include the removal of the Brand-
on Road Dam and Lock and the existing Lockport Lock and Con-
trolling Works, and the construction of a new dual lock and
control gates in the waterway about 2 miles upstream from the
existing Lockport Lock. This will extend the water levels of
the Dresden Pool upstream to the new Lockport Lock, where the
low-water differential water surface will become about 74 feet.
The corresponding differential, during maximum flows, has not
been accurately determined but will probably be about 70 feet.
The proposed relocation of the locks and deepening of the
channel is shown on Figure 9.
The completion of the above described work will move
the possible point of low-level discharge for an underflow
tunnel, or tunnels, about 10 miles upstream from that shown
in the 1966 Chicago Underflow Report. The utilization of this
low-level point of discharge for peak flows becomes more
attractive.
Also shown on Figure 9 is a proposed widening of the
Sanitary and Ship Canal from the new Lockport Dam and Locks to
Sag Junction.
A project, already approved by Congress and awaiting
funding, provides for the widening of the channel to 225 feet.
The Chicago Drainage Plan now proposed by the Illinois
Division of Waterways recommends the widening of this reach to
325 feet to accommodate barge tows which currently operate on
the Illinois Waterway as far upstream as Brandon Road Pool and
to increase flood conveyance capacity.
The Division of Waterways Plan also recommends a
10-foot deepening of the Canal for a width of 150 feet to
further increase conveyance capacity.
The Combined Underflow-Storage Plan herein recommend-
ed assumes a widening to 325 feet, without any deepening.
181
-------
Ntw Dam, Twin Lock*
and Controlling Work*
at Site of Editing
Controlling Work*
Drop Shaft* from
Canal to Underflow
Bank Un«
—
Sag Channel
Normal Water Suffoc*
Existing Lockport Dam, Power House
and Locks To Be Removed
Brandon Road Dam and
Locks To Be Removed
Sanitary and Ship Canal Between Lockport
and Sag Junction To Be Widened
New Lockport Dam and Twin Locks
(Including Controlling Works for Both
Overflow and Underflow)
WATERWAY IMPROVEMENTS
BETWEEN BRANDON RO
AND SAG JUNCTION
FOR
FLOOD CONTROL AND NAVIGATION
-------
TABLE 4
STORAGE VOLUME IN MAIN TUNNELS
LOCATION
Mainstream
Mainstream
Mainstream
Mainstream
Mainstream
TOTALS
Calumet Br.
Calumet Br.
Calumet Br.
Calumet Br.
TOTALS
DesPlaines Br.
GRAND TOTALS
SIZE
Twin 26'x50'
Twin 26'x50'
Single 26'x50'
17' $
12' $
Single 26'x50'
Single 26'x50'
14' «
10' *
Single 26'x50'
LENGTH
(MILES)
11.99
20.38
13.53
3.00
12.80
61.70
8.27
12.45
2.00
2.29
25.01
19.50
106.21
VOLUMES IN ACRE FEET
PER MILE
302.0
302.0
149.0
27.3
13.7
149.0
149.0
18.8
9.2
149.0
PHASE 1
3,621
2,016
82
175
5,894
1,232
37
21
1,290
7,184
PHASE 2
6,155
6,155
1,855
1,855
2,906
10,916
TOTAL
12,049
3,145
2,906
18,100
TO
-------
COMBINING STORAGE WITH CONVEYANCE
The City of Chicago presented, in September, 1968,
the Composite Drainage Plan, which considered the possibility
of providing mined storage areas at four locations along the
main tunnel, plus one in the Calumet Area and one along the
DesPlaines River Tunnel. This was proposed in order to provide
temporary detention storage closer to the various origins of
spillage water and thereby reduce conveyance distances, and
consequently the cost of conveyance tunnels. This concept of
geographical spreading of the underground storage volume is
further extended in the Underflow-Storage Plan.
It is now suggested that the main tunnels be re-sized
so as to serve both as conveyance tunnels and as continuous
storage reservoirs. The revised pattern is shown in Figure 10
attached hereto. The total length of underflow-storage tunnels
is about 106 miles.
It is proposed that the principal tunnels be 26 feet
wide and 50 feet high and have paved inverts plus sidewall
lining (in their lower portions only). The principal or main-
stream tunnels from Lockport to Lake Street would be Twin
Tunnels, as shown in Figure 10.
It is also proposed that the inverts slope to low
points opposite each of the three major existing treatment
works as shown on the profiles in Figures 11 and 12. Pumping
stations are proposed at these points having a combined pumping
capacity of about 2,000 cfs, which is about equal to 3/4 of the
total ultimate dry weather average flow through the three major
treatment works.
A cross-section of the proposed principal tunnels
is shown in Figure 13.
The total storage volume of the tunnels shown for
construction on Figure 10 is equal to 18,000 acre-feet, or
1.12 inches of runoff from the entire 300 square miles of com-
bined sewer area. The distribution of this storage volume is
shown in Table 4. Again, referring to Figure 8, it would
accomplish, on a long term basis, an average of more than
98.5 percent entrapment of combined sewer B.O.D. spillages.
184
-------
North Side .
Treatment Works &
Tunnel Dewatering
Pumping Station
-v \
..A
LEGEND
UNDER FLOW-STORAGE TUNNELS
1" Phase - 2 Bbl.
1st Phase - 1 Bbl.
2nd Phase - 2 Bbl.
2nd Phase - 1 Bbl.
3"1 Phase - T Bbl.
' •— West-Southwest
Treatment Works
Tunnel .Dewatering.
Pumping Station
ADDITIONAL UNDERFLOW BRANCHES
PROPOSED AND UNDER CONTRACT -
BOUNDARIES OR COMBINED SEWER AREAS
Canal-to-Underllow
Control .Structure
Calumet Treatment
Works & Tunnel
Dewatering
Pumping Station
Sanitary and Ship Canal
To Be Widened
r Proposed New Lockport
Dam & Control Gates
Coupled With Outflow
Controlling Works From
Underflow Storage Tunnels
Existing Lockport Dam To Be Removed
Plaines River
Fo Be Lowered
r Surface Lowered 34'
Existing Brandon Road Dam
To Be Removed
UNDERFLOW STORAGE PLAN
FIGURE 10
185
-------
, DESPLAINES
RIVE*
OJ
£«
L. SANITARY .AND SHIP CANAL „
m END PHASE I»T PHASE
_ 10. JS Ml. L 4,4« Ml. 5. 97 Ml.
„ N. 8 S BRANCHES OF^
CHICAGO RIVER
2ND PHASE
JJSMI j 4. 40 Ml.
jl **- 'L'o.«M..
-• i « *
181 wi . 9.85 Ml.
K 0.79 MI. J
fe" >
MCLJODCT i
. onUnli
CHANNEL
1ST PHASE
r i.oo MI.
JM,3.BOMI. ., I^3.K)MI; w
ui i oow'/> {^
^ z
-r
>
HI
o
c
•yo
m
285
290
295
300
305
310
315
320
325
330
340
-------
O
73
SANITARY
., AND SHIP CANA
CALUMET SAG CHANNEL
OGLESBYAVE
LITTLE CAL. RIVERA S
»A 'I30THI
EASEMENT
BALTIMORE AVE.
TUNNEL OUTLET
CONTROL! NG
WORKS
W.L.-70.0TO-75.0
-100
EL. ZI9.9
-1000
290
295
300
505
310
320
329
-------
L_ 160 to 200
: 1
70'
<:_ Of Waterway
70'
D Q
Proposed
Twin Tunnels
n"
i i
L.J
Future
O
10
--
TYPICAL ARRANGEMENT
OF WATERWAY ft TUNNELS
is1;
'
"o
to
W
'
26'± ,
23' _f
n \ \
,18"
cv| ^-Concrete Lining
TUNNEL SECTION
ARRANGEMENT AND
SECTION OF MAIN TUNNELS
FIGURE 13
188
-------
The pumping rate of 2,000 cfs. will completely de-
water the full volume of these tunnels in about four and one-
half days, it is intended that dewatering will commence at
the end of each storm runoff period at the treatment works.
The distribution of the pumping capacity for de-
watering stations would bear the following comparative re-
lationship to the presently projected ultimate rates of flow.
Treatment Works Ultimate Ultimate Tunnel
Dry Weather Max.Rate Dewatering
Average of Flow Capacity
(C.F.S.) (C.F.S.) (C.F.S.)
North Side 500 1,000 350
West-Southwest 1,500 3,000 1,100
Calumet 750 1,500 550
Totals 2,750 5,500 2,000
The rate of delivery of entrapped combined sewer spill-
age to the treatment works would therefore be equal to 73 per-
cent of the ultimate dry weather average flow or 96 percent of
the estimated dry-weather flows in the year 1978. The present
design basis for treatment works enlargement is based upon max-
imum flows, 100 percent greater than the ultimate dry weather
flows.
Dewatering the entire storage volume of the tunnel
system at the above rate would require 109 hours, or 4 days,
13 hours. This would represent the maximum detention period
in the tunnel system and could be expected to occur at a fre-
quency of about once in two years.
Assuming mass runoff rainfall ratios varying between
1/10 at 0.1 inch of mass rainfall to 4/10 at 2.5 inches of
mass rainfall, and based on average frequencies various mass
rainfall quantities, the probable storage detention periods
and frequency of occurrence would be about as follows:
189
-------
Frequency Runoff Vol.Stored Detention
1 time per year 1.0 in. 16,000 Ac.Ft. 4 days
8 ' 0.25 " 4,000 " " 1 day
24 " " " 0.08 " 1,300 " " 8 hours
40 " " " 0.04 " 650 " " 4 "
To minimize escape of odors from the pumpage,
especially during the 4-day pumping periods, expected to occur
about once per year, the pump discharge.should be connected to
the existing intercepting sewer in such a way as to obtain
blending with the fresher sewage without undue turbulence.
If desired, at the end of each pumping period, flush-
ing water can be admitted to the upper end of the sloping
tunnel inverts in quantities not exceeding the pump capacity
of their respective pumping stations, so that the tunnels will
be both empty and free of sludge deposits after each storm
runoff period. The depth of flow in the 26'x50' tunnels,
during flushing, would be between 4 and 6 feet.
The remaining 1% percent or less of combined sewer
spillage, which is not accommodated by storage, represents
the excess runoff from storms of small frequency — less than
once in two years. At such times, the tunnels will serve as
flow-through conveyance tunnels operating as submerged con-
duits or flowing traps and delivering the excess volume to the
extended Dresden Pool, and to the highly aerated flow at the
base of the new Lockport Lock and Dam. During these heavier
storm periods, flow over the Lockport Dam and from the DesPlaines
River below Hofmann Dam will provide adequate dilution water to
keep the dissolved oxygen through the extended Dresden Pool
above the requirements of SWB-8 (3).
UTILIZATION OF SURFACE WATERWAYS
At all times, except when combined sewer spillages
in any one storm period, exceed the volume of entrapment in
the storage-conveyance tunnels, the surface waterways would
be conveying only the treatment works effluents, surface run-
off from areas not connected to the Underflow-Storage System,
wastewater from industries, and dilution waters from Lake
Michigan. With the proposed upgrading of treatment works and
industrial plant effluents, and the allowable but greatly
190
-------
reduced dilution quantities, the stream quality in dry
weather will readily meet prescribed standards (SWB-15).
When the spillage volume exceeds the underground
storage, the hydraulic gradient in the tunnels will rise
rapidly toward the water levels in the surface waterways.
This would generally occur first in the upstream ends of the
tunnels. The underflow tunnels which, for lesser storms, serve
as underground storage, would become a major auxiliary con-
veyance facility delivering the excess flood flows to Lockport.
The combined conveyance to Lockport via the Sanitary and Ship
Canal (with widening below Sag Junction, but without any deep-
ening) plus the conveyance via the underflow tunnel would be
sufficient to permanently prevent overbank flooding or release
of polluted water to Lake Michigan which, since 1954, has
occurred with increasing frequency. Under the plan proposed
herein, the combined discharge capacity of the surface canal
plus the twin underflow tunnels is about 43,000 cubic feet per
second or 3,580 acre-feet per hour. Compare this with the
existing Sanitary and Ship Canal, completed in 1900, which was
designed for 10,000 cubic feet per second, but under flood
conditions has discharged up to 24,000 cubic feet per second.
RESIDUAL DIRECT SPILLAGE TO WATERWAYS
The initial portions of underflow to Lockport will
deliver substantial quantities to Lockport by below-surface
conveyance prior to the discharge of any pollution from the
combined sewer outlets to the surface waterways upstream from
Lockport. In some storm periods, this additional feature of
the underflow-storage plan will entirely prevent spillage of
pollution to surface waterways. Even in the infrequent more
extreme storm periods, it will greatly reduce surface water-
way pollution in the areas, upstream from Lockport.
In order to evaluate the effect of this pre-pollution
flow through the tunnels, a separate computer analysis of
all combined sewer spillages for a 16-year period was made.
In this analysis for the mainstream tunnel alone, with 12,000
acre-feet of storage and a dewatering pumpage rate of 1,000 cf.s.
following each storm period, (the pumpage proposed herein for
the mainstream tunnel would be 1,450 cfs., however, this cap-
acity would also serve the DesPlaines River Underflow Tunnel)
there were only 6 storm periods in 16 years, 1949-64, which
191
-------
would overtax the storage volume of 12,000 acre-feet.
The hydrographs of estimated flow at combined sewer
outlets along the mainstream in excess of the storage volume
for a future recurrence of these 6 storms are shown in
Figure 14.
Backwater computations for the underflow tunnels
shown in Figure 11, indicate that, before the hydraulic gra-
dient would reach river levels at Wilmette, quantities of
spillage rates could accumulate to a rate of flow of 12,000
cfs. passing through the tunnels at McCook (just west of
West-Southwest Treatment Works).
Using 12,000 cfs. as a dividing line on Figure 14,
the underflow and overflow quantities were determined for
6 storm periods mentioned above. The data shown in Figure 14
is tabulated in Table 5. It will be seen in this tabulation
that, if the proposed underflow-storage plan had been in
operation, the total hours of spillage in excess of storage
for the 16-year period would have been approximately 43 hours
or an average of 3 hours per year. Also, that the hours of
spillage directly to the river at the combined sewer outlets
would be only 15 hours, or an average of 1 hour per year.
HYDROLOGIC ANALYSIS OF TWO MAXIMUM STORMS
A further analysis has been made of the impact of
the possible recurrence of the two maximum storms of record,
which occurred in October, 1954 and in July, 1957. Data
obtained by computer runs of the storms are plotted on
Figures 15 and 16.
Conditions of maximum probable future development and
land use affecting runoff conditions were assumed in the study
of the combined adequacy of the proposed underflow tunnels and
the improved surface channels downstream from Sag Junction to
the proposed new Lockport Controlling Works. It was calculated
that after filling 18,000 acre-feet of underground storage,
the flow in the underflow tunnels could reach a rate of 14,000
cfs. before rising hydraulic gradients upstream would cause
spillage into the surface waterways at the combined sewer out-
lets, and that the maximum combined outlet capacity of tunnels
and the Sanitary and Ship Canal would be 43,000 cfs.
192
-------
40
020
I
] Spllloo,. To Sorlw* Waterway at Combln*4 Sewer Outlets
tfri-i-i-iii-iti'i-i (For VoiUm. •** to
I BOD SM Taklt 2 )
I Plow To Locksort via Underflow Tunnel*
F^VVWJ (Far Volum. and 6.0 0. S.« Tabu 2 ) '
I
iiiiiiitii
^. •^rj^rrrr-
12349 •
A.M. SEPT 14, l»«l
IO II 12 I 2 3 4 9 B
P.M. A M .JULY 13,1957
3436
P.M. »Err.2S,l9«l
NOfM<
ID Data From Computer Studio of 16 Yean of Rainfall Records (I949-B64 Inc )
For 127,000 Ac.Tributary To The Mainttream Waterway From Wilmette To
Summit.
(2) Plotted Data It For 6 Maximum Storm Perlodi.
(3)Dlvidlng Line Between Underflow and Surface Flow OzpOO cf») !• Eetimated
Maximum Rote of Underflow, Downstream From W.-SW. rrgatment Works
Before Hydraulic Gradient In Underflow Tunnels Rite* To River Levels M
Wllmetle.
O
C
70
OVERFLOW TO MAINSTREAM FROM COMBINED
SEWERS AFTER EXCEEDING THE UNDERGROUND
STORAGE OF ItfrO.QjD
OCT. IO, 1*54
TIME 'HOURS
-------
TABLE 5
ESTIMATED DURATION, VOLUME AND B.O.D..
OF SPILLAGE AT COMBINED SEWER OUTLETS
AND UNDERFLOW TO LOCKPORT. ASSUMING
RECURRENCE OF YEARS OF RECORD
(1949-64 INCLUSIVE) AND 12,000 ACRE-FEET OF
MAINSTREAM UNDERGROUND STORAGE
(For Graphical Presentation, See Figure 14)
Storm
June 15, 1949
June 2, 1950
Oct. 10, 1954
July 13, 1957
Sep. 13, 1961
Sep. 25, 1961
Totals
Spillage to Waterway
Upstream from Lockport
Time
Hrs.
-
-
4.50
7.25
3.25
—
15.00
Volume
Ac. -Ft.
-
-
7,215
19,058
4,518
-~
30,791
B.O.D.
K.Lbs.
-
-
356
1,255
458
—
2,069
Underflow to Lockport
Time
Hrs.
3.50
1.25
22.25
7.50
5.25
3.00
j
42.75
Volume
Ac. -Ft.
1,016
107
12,383
7,879
4,342
553
26,280
B.O.D.
K..Lbs.
227
40
1,295
497
474
125
2,658
194
-------
The results of these analyses are shown on Figures
15 and 16. Figure 15 indicates that the proposed underflow-
storage plan will be able to handle all flow rates expedi-
tiously with some margin of safety. Figure 16 indicates a
narrow margin of over-run between the expected runoff hydro-
graph under the assumed future land use and development and
the storage-plus-conveyance capacity of the proposed plan.
It indicates that under the ultimate development, there would
be some spillage into Lake Michigan.
The storm in July, 1957, far exceeded in total vol-
ume of rainfall in such a short time period than any other
storm of record and has been variously classified as having
a probability of recurrence interval well in excess of
100 years. It also had exceptional uniform rainfall rates
and volumes over the entire Chicago Metropolitan Area. We
have assumed, therefore, that the cost/damage ratio is too
high to warrant expansion of present planning to develop com-
plete protection against the possible repetition of this
storm. Since the ultimate land use as assumed may not occur
for several decades, expenditures to meet this ultimate
possibility can be deferred until after a decade or two of
experience with the facilities proposed herein. Future in-
crease in both storage and conveyance can be accomplished by
additional lengths of large tunnels, paralleling the initial
tunnels. Such an added tunnel, for example, under the main-
stream from Willow Springs to Lockport would add 15.8 miles
of 26'x50' tunnel, and would provide an additional 2,350 acre-
feet of storage and 525 acre-feet per hour of additional out-
let capacity at an overall cost of 95 million dollars. To
spend this additional amount at this time is not advisable.
POLLUTION MODEL OF THE MAINSTREAM SURFACE WATERWAY
In order to determine, with a reasonable degree of
certainity, whether the Underflow-Storage Plan would meet the
requirements of the State Sanitary Water Board's Rules and
Regulations SWB-15, a Pollution Model of the waterway was pro-
grammed for the electronic computer.
The computer model is essentially that which was
presented at the December 2, 1968 Technical Advisory Committee
meeting. Input data, required for this program, include the
initial conditions and all incremental data such as the flow
rates, B.O.D., D.O., and temperature of all flows entering
195
-------
WEIGHTED RAINFALL ON TRIBUTARY AREA '
GAGES:
EVANSTON 8%
MAYFAIR 2T
DOWNTOWN IS
MIDWAY 29
CALUMET 23
I 100%
SPILLAGE FROM SEWER OUTLETS
I
ULTIMATE DRY WEATHER FLOW FROM
3 TREAT PLANTS ANTECEDENT TO
RAINFALL (2700C FS)
' I ' 1 1 J 1 1 1 1 1 1 L
ADDITIONAL FLOW FROM THE N BR CHICAGO RIVER
AND THE LITTLE ft GRAND CALUMET RIVERS
OUTSIDE OF THE COMBINED SEWERED AREAS '
FLOW FROM COMBINED
SEWER OUTLET AREA
ULTIMATE MAXIMUM FUOW FROM S PLANTS AND AFTER STORM (SSOOC FS.)
1 I I i • ' i 1 1 1 1 1 1 1 1 1 L—U_l 1 1 u
DISCHJ^OE THROUGH SANITARY AND SHIP CANAL"- SAG JUNCTION TO LOCKPORT
o
c
TO
DISCHARGE OF ALL COMBINED SEWERS,IN THE 300SQ Ml.
COMBINED SEWERED AREA.TO EITHER THE UNDERFLOW-
STORAGE TUNNELS OR THE SURFACE WATERWAYS
I
SPILLAGE FROM SEWERS TO DESPLAWES
RIVER (NOT TRIBUTARY TO S. a S. CANAL)
MAXIMUM VOLUME OF STORAGE IN
WATERWAY ABOVE ELEVATION -2.0
FLOW IN WATERWAY SEE
ABOVE
FLOW THROUGH
UNDERFLOW-STORAGE
TUNNEXS TO LOCKPORT
STORAGE TUNNELS
F ULTIMATE
FF
UrtDERFLOW*TOHAGE
TUNNELS FOR A FUTURE RECURRENCE
OF THE OCT. 9-10,1954 STORM
INCREASE FLOW THROUGH UNDERFLOW - STORAGE TUNNELS
IING GATES AT WILLOW SPRING SHAFT
-------
P.M. JULY 12, 1957
o
c
10
m
WEIGHTED RAINFALL ON
TRIBUTARY AREA
OASES: EVANSTON--
MAYFAIR
DOWNTOWN --
MIDWAY;
CALUMET-,—
ADDITIONAL FLOW FROM
THE N. BR. CHICAGO RIVER
AND LITTLE ft GRAND
CALUMET RIVERS OUTSIDE
OF COMBINED SEWERED AREAS
RELEASE OF WATER FROM
CANAL AT LOCKPORT PRIOR
TO OVERFLOW FROM SEWER
SPILLAGE FROM
ULTIMATE DRY WEATHER
FLOW TREAT PLANTS
ANTECEDENT TO RAINFALL
ULTIMATE MAXIMUM FLOW FROM 3 PLANTS DURING ANJD AFTER STORM (5500
L ,t. 1 1 1 1 1
LOCKPORT
DISCHARGE THROUGH SANHARYowd
DISCHARGE OF ALL COMBINED
SEWERS, IN THE 300 SO. Ml
COMBINED SEWERED AREA TO
EITHER UNDERFLOW-STORAGE
TUNNELS OR SURFACE
WATERWAYS
,•0
IP
Ri*.o
JI8,OOOAF;v
/\N UNDEWUJW
sSTORAGExS
s TUNNELS 5S
^vvvvv^
SPILLAGE FROM SEWERS TO DE3 PLAINES
RIVER (NOT TRIBUTARY T.O S.8 S. CANAL)
MAXIMUM VOLUME OF STORAGE IN
WATERWAY ABOVE ELEVATION -20
OVERFLOW TO LAKE MICHIGAN ASSUMING
ULTIMATE DEVELOPMENT OF 300 SO. Ml
TRIBUTARY AREA |
FLOW IN WATERWAY
ABOVE |
FLOW THROUGH UNDERFLOW
STORASE TUNNELS TO
LOCKPORT I
^r «
PM JULY 12, 1957
I
ANALYSIS OF ULTIMATE RUNOFF
FROM 300 SQUARE Mill .OF
COMBINED SEWER AREA, AND JUE
OPERATION OF UNfcWLOW STORAGE
TUNNELS FOR A fUTUM~ RECURRENCE *
OF THE JULY 12 - 13.T957 STORM
I
AM JULY 13,1967
To"
-------
TABLE 6
ESTIMATED DISSOLVED OXYGEN CONDITIONS
IN MAINSTREAM DURING SEVERE STORM PERIODS
1
2
3
U
5
6
7
e
9
10
11
12
13
Ik
ft*Mh Mb*r
Apd
taoatloB
UllMtt*
To
ETUI* ton
RTMMtoa
To
I. Bite Tr*»t. ttu.
R. Sid* Tr«it. *».
To
Immoo* AT*.
I**T*nO* AT*.
To
AOdiMB St.
AddlMD St.
To
forth Art.
north AVI.
To
Chlonfjo Klw
Chieigo RlT*r
To
Aahlnd AT*.
AchUad AT*.
To
Clocro AT*.
Cletro AT*.
Mrl*B AT*.
•wife AT*.
TO
Bodt*lj»
•odtfclni
To
'VlUov Byrlnsi
Vlllaw Sjrlafi
To
SM jwetioa
S*« JMWtlOD
To
LMOBt
"IT*
Oo
9-1
Ma.
D.O.
6.99
5.3«»
5.01
H.ae
k.2i
3.96
3.n
3.38
H.HO
k.ae
k.it
f
3.»7
v.ia
*.03 •
UKMT
0, 195
•DOT*
5
PPM
0
0
0
k
12
35
26
38
89
32
3«
tl
W.
M
«
B*lm
nt™-
PPH
0
0
0
0
0
>
10
is
0
0
0
7
0
0
1C.
Ma.
D.O.
5.1»0
*.2«
^>>7
3.78
3.78
3.62
3.05
2.M
3.31
3.09
t.92
a.7«
3.38
3.K
JvUr
13, 1»
Boor*
5
m
0
15
7
7
to
M
3*
«6
36
to
Wt
»o
50
57
57
tolov
™r^
PfM
0
0
0
1
3
13
22
31
22
«5
28
33
31
3«
8*1
12-13
Mia.
D.O.
6.90
5.61
5.15
k.26
*.17
3.66
3.11
8.57
3.9*
3.T8
3.«3
3.*o
3.66
3>7
>t««bu
, 1961
lav*
5
PM
0
0
0
3
13
37
30
U
33
38
*3
50
50
57
aia
I
PPM
0
0
0
0
0
10
15
85
k
18
18
2%
19
25
Total 1
Below Tat
D.O. U
Y**r Pi
5
PPM
0
15
7
1*
*5
116
90
188
100
US
us
1U
1
-------
the mainstream from combined sewers, treatment works,
industries, power plants and Lake Michigan dilution water,
and from branch waterways. (N.Branch and Cal.-Sag Channel)
Of the 6 storms that would exceed the underground
storage of 12,000 acre-feet in the mainstream underflow
tunnels, only three would exceed the underflow conveyance to
Lockport, See Figure 14.
Combined flow from the sewer outlets would spill to
the mainstream waterway in a future recurrence of the three
exceptionally heavy storms. The Pollution Model was used to
determine the impact that these scillages would have on the
dissolved oxygen in the mainstream waterway between Wilmette
and Lockport, and a separate analysis was made for the Des
Plaines River from Lockport to the Kankakee River.
Table 6 gives the minimum dissolved oxygen during
each storm for all 14 reaches between Wilmette and Lockport.
Also, the time in hours is recorded, during which the D.O. was
below 5 ppm and 4 ppm. The most critical reaches appear to
be numbers 8 and 12. Figure 17 shows the oxygen sag curves
for certain reaches of the waterway, including the DesPlaines
River, for a recurrence of the October 9-12, 1954, July 12-13,
1957 and the September 13-14, 1961 storms.
It can be seen in Table 6 that for reach number 14
oxygen was below 5 ppm for 162 hours and below 4 ppm for
61 hours in the entire 16 years analyzed. Thus, the dis-
solved oxygen in this reach of the waterway would be above
4 ppm more than 99.96 percent of the time. This can be ac-
cepted as being in compliance with the standards established
by the Sanitary Board's Rules and Regulation, SWB-15.
PROTECTION OF GROUNDWATER AQUIFERS
It is important in any plan which contemplates the
storage of polluted stormwater in underground tunnels or
reservoirs, that necessary precautions be taken to adequately
protect the groundwater resources of the Chicago Region.
There are four aquifers in the Chicago Metropolitan
Area which are arranged successively with regard to depth
below the ground surface as follows: 1) the sand and gravel
aquifer in the glacial drift, 2) the shallow dolomite or
Silurian dolomite aquifer, 3) the Cambrian-Ordovician aquifer,
and 4) Mt. Simon aquifer.
199
-------
DES PLAINES RIVER NEAR JOLIET
a
a
u
X
a
u
_
o
M
5
X
c
c
L^
>
_>
O
OCTOBER 1954
DES PLAINES RIVER NEAR JOLIET
O.
01 6
z
z
Ul
e 4
X
O
S 2
O
n
- 0
15
JULY 1957
0€S PLAINES RIVER NEAR JOLIET
6
14
16 I 17
SEPTEMBER 1961
DISSOLVED OXYGEN SAG CURVES
FOR RECURRENCE OF STORMS
CAUSING SPILLAGE TO MAINSTREAM
UPSTREAM OF LOCKPORT
FIGURE 17
200
-------
The sand and gravel aquifer is widely scattered
through the region and in many cases is hydraulically inter-
connected with the silurian dolomite aquifer. The upper two
aquifers, referred to as the shallow aquifers, are the source
of well water for many homes, industry and some villages in
the suburban areas which are not supplied Lake Michigan water
by the Chicago Water System. The shallow aquifer extends to
a maximum depth of about 400 feet and is recharged locally by
the downward percolation from streams and rainfall infiltration.
As shown in Figures 11 and 12, the tunnels herein proposed are
located in the dolomite or lower portion of this aquifer.
A relatively impermeable shale formation, having a
thickness of 150 to 300 feet, called the Maquoketa Group, lies
below and separates the shallow Silurian aquifer from the
Cambrian-Ordovician aquifer. The Cambrian-Ordovician and the
Mt. Simon aquifers are partially separated by another lower
shale formation called the Eau Claire Group. The Cambrian-
Ordovician and the Mt. Simon aquifers are referred to as the
Deep aquifers. The Galena-Platteville Dolomite, shown in
Figures 11 and 12, forms the upper portion of the Cambrian-
Ordovician Aquifer.
The greatest sources of water for deep well pumps
which supply many communities and industry, are the Ironton-
Galesville and the Glenwood-St. Peter sandstone formations
within the Cambrian-Ordovician aquifer. These sandstone
strata lie below the Galena-Platteville Dolomite, in the
Chicago Region, but are recharged from rainfall infiltration
and surface water percolating through the outcroppings of this
aquifer in Western Illinois and Southern Wisconsin. Because
pumping from this deep aquifer is exceeding the recharge rate,
the piezometric level in this lower aquifer is dropping at the
rate of 10 to 15 feet per year.
As already stated, the Underflow-Storage tunnels
herein proposed are to be located in the Niagaran dolomite
formation in the Silurian or shallow aquifer. The tunnels
will be 75 to 300 feet below the normal piezometric water
table in that aquifer. Since the tunnels will be located gen-
erally, in the lower part of the Niagaran rock formation,
which is more dense and less permeable than the weathered and
fractured, near-surface, rock of the same formation, it is
expected that leakage into or out of the tunnels will be small.
201
-------
Computer calculations of runoff for every hour of
rainfall in 16 years of records, 1949 to 1964 inclusive, as
previously mentioned show that the 6 largest storms, during
the 16-year period, would if they recurred after com-
pletion of the plan proposed herein cause overflow to the
waterway at Lockport. During the time of overflow, the hy-
draulic gradient in the Underflow-Storage tunnelw would be at
Elevation -70 or above. The calculated summation of this
time of overflow for all 6 storms is less than 43 hours, with
about 22 hours of the total occurring during an assumed re-
currence of the October 9-10, 1954 storm.
Since there are approximately 140,000 hours in 16
years, the hydraulic gradient or pressure level in the Under-
flow-Storage tunnels would be below Elevation -70.0 more than
99.97 percent of the time.
Since the upper portion of the Underflow-Storage
tunnel section is not proposed to be concrete lined, the per-
colation of groundwater into the tunnels will slowly lower
the piezometric head in the aquifer in the immediate vicinity
of the tunnels. This is similar to what occurs at the many
quarry sites in the Chicago area. After a period of several
months, the water table within the aquifer would stabilize
forming a groundwater valley over and along each of the
tunnels.
Within this relatively dry valley, all free water
will have been removed from the pores, joints and cracks and
crevices of the rock creating a considerable volume of avail-
able storage. During heavy rainfall periods when the surface
runoff exceeds the storage volume of the Underflow-Storage
tunnels, the higher pressures in the tunnels will cause water
to move outward into the rock at a slow rate filling those
voids. Studies were made to determine the distance the
water would travel as a function of the duration of surcharge
by several methods. The most severe results from the stand-
point of groundwater pollution were obtained by a study which
assumed that the water would travel outward from the tunnel
along radial paths filling the voids as it moves. Values of
void ratio of 0.0002 and a permeability coefficient of
1.0 gpd/ft2 were used for this dense rock at the level of the
proposed tunnels.
202
-------
Figure 18 shows the radial distance the water would
travel as a function of the duration and magnitude of the
surcharge.
This graph was applied to the storm causing the long-
est period of overflow. (Storm of October 9-10, 1954). Assum-
ing a static level of the piezometric water level above the
tunnels to be at Elevation -200, the water table would rise less
than 50 feet above the roof of the tunnels during the approx-
imately 24 hours of overflow to the waterway. See Figure 19.
Soon after the conclusion of the overflow period, dewatering
of the tunnels would commence, internal pressure in the tunnels
would dimish to the roof levels and infilatration would again
re-establish the groundwater valley to its pervious shape. It
is apparent that no temporary storm surcharge period, which
causes outward flow from the tunnel, will refill the normal
groundwater valley established by the much more prevalent con-
dition of infiltration into the tunnels.
It can therefore be concluded that no pollution of
the aquifers will be caused by the construction and operation
of the Underflow-Storage tunnels in Niagaran limestone form-
ations, and that this valuable water resource of groundwater
supply will be preserved.
Conditions in the Galena-Platteville Dolomite
present a different picture. Here, as previously stated, the
groundwater resources are steadily being depleted and the piez-
ometric level has already fallen to more than 300 feet below
ground surface and is expected to continue downward at 10 to
15 feet per year.
Unlined tunnels or reservoirs at these lower levels
would now or in the near future be relatively higher than the
steadily receding groundwater level. In order to prevent
pollution of the aquifer, in this case, would require con-
tinuous recharging of the rock strata in the vicinity of the
tunnels or reservoirs, or limitation of withdrawals to the
natural recharge rates.
PROJECT COST
The largest single item of cost of the proposed pro-
ject is the excavation, hauling and disposal of rock.
203
-------
This Radio/Mode/ of the Exfi/fratio*
fo Me Aquifer /s one of Several Sfud/ed.
INsmore Conservative and Tfo/vfore Show
A Greater Penetration of Wafer wfo /A?
A ft//far ffaff wov/d prabab/y occur.
40
NJ
O
70
50
40
30
20
10
TUNNEL
STATIC PIEZOMETRIC
WATER TABLE AFTER
TUNNEL CONSTRUCTION
10 tO 10 40
DURATION OF SURCHAHOI, HOURS
STUDY OF EXFILTRAJION OF WATER DUE TO
INTERNAL SURCHARGE IN TUNNEL SYSTEM
DURING STORM PERIODS
oo
-------
-100- •
N
I- -150-
UJ
_j
UJ
-200-•
o
-250--
-300
SPILLAGE PERIOD TO CHICAGO RIVER 8 S.S. CANAL
RIVER LEVEL-^2
DRESDEN POOL EL.» -
RELATION BETWEEN
WATER LEVELS IN
TUNNELS AND ADJACENT
GROUNDWATER LEVELS
DURING MAXIMUM
STORAGE PERIOD
SPILLAGE PERIOD AT LOCKPORT
ELEVATION OF HYDRAULIC GRADIENT
IN UNDERFLOW STORAGE TUNNELS
DEWATERING PERIOD
-ELEVATION OF PIEZOMETRIC WATER LEVEL
IN THE SILURIAN DOLOMITE AQUIFER
ABOVE UNDERFLOW STORAGE TUNNELS
ASSUMED STATIC WATER
LEVEL NEAR TOP OF TUNNELS
OCTOBER 1954
-------
To arrive at a conservative estimate for the rock ex-
cavation (including hauling and disposal) conferences have
been continued with manufacturers of rock drilling, blasting
and hauling equipment. These companies have had wide exper-
ience in working with contractors engaged in rock tunneling
throughout the United States and elsewhere.
These conferences and studies were a continuation of
similar conferences and inspection trips, participated in
by the Bureau of Engineering, as well as the Metropolitan San-
itary District and their consultants.
Figure 20 shows graphically the variation in unit
cost of rock excavation with the size of the tunnels and the
number of simultaneously worked tunnel headings. Prices per
cubic yard vary from $60.00 for a 10-foot diameter single tunnel
with two headings to $5.65 per cubic yard for cavern (room and
pillar) excavation with multiple headings. The principal
governing factor appears to be the size or face area of the head-
ings. For the combined Underflow-Storage tunnels, with 26-foot
wide by 50-foot high tunnel faces, the estimates are $8. 81 per
cubic yard for single tunnels and $8.03 per cubic yard for twin
tunnels.
Table 7 shows the quantities of rock excavation re-
quired for the various tunnel sizes and locations.
Table 8 shows the overall contract cost of the tunnels
required, classified as to size, location and construction phase
Table 9 is a summary of Total Project Cost, including
contingencies, and engineering and supervision.
206
-------
COST OF ROCK EXCAVATION
AND DISPOSAL VS. SIZE
OF TUNNELS, WITHOUT LINING
I 30 —
O
u
20
10
LAWRENCE AVENUE
-M. S. D. CONTRACT 13A
LAWRENCE AVENUE
M.S.D. CONTRACT 18E
UNDERFLOW
STQtAOE, PLAN
SINGLE 26'*50'$t.fl
MINED STORAGE $S.45/CU.Y».
J I 1 I I L
10 20 30 40 50 60 70 SO 90 100
SOLID ROCK MINiD - C'Y'/LIN. FT.
FIGURE 20
207
-------
TABLE 7
QUANTITIES OF ROCK EXCAVATION (Main Tunnels Only)
(Rock "in situ", or solid rock)
LOCATION
Mainstream
Mainstream
Mainstream
Mainstream
Mainstream
TOTALS
Calumet Br.
Calumet Br.
Calumet Br.
Calumet Br.
TOTALS
es Plaines Br.
SIZE
Twin 26'x50'
Twin 26'x50'
Single 26'x50'
17' *
12' *
Single 26'x50'
Single 26'x50'
14' *
10' *
Single 26'x50'
GRAND TOTALS
LENGTH
(MILES)
11.99
20.38
13.53
3.00
12.80
61.70
8.27
12.45
2.00
2.29
25.01
19.50
106.21
ROCK EXCAVATION - THOUSAND CU.YDS.
PER MILE
502.0
502.0
251.0
51.6
26.9
251.0
251.0
36.0
19.8
251.0
PHASE I
6,030
3,406
155
344
9,935
2,090
72
45
2,207
12,142
PHASE 2
10,250
10,250
3,120
3,120
4,880
18,250
TOTAL
20,185
5,327
4,860
30,392
Ni
O
00
Note: -
Loose rock to be handled is estimated at 140% of volume shown
or approximately 42 million cubic yards.
-------
TABLE 8
ESTIMATED CONTRACT COST OF TUNNELS
PHASES 1 AND 2
LOCATION
Mainstream
Mainstream
Mainstream
Mainstream
Mainstream
TOTALS
Calumet Br.
Calumet Br.
Calumet Br.
Calumet Br.
TOTALS
Des Plaines Br.
GRAND TOTALS
COST OF BRANCHES
Tributary to
Tributary to
SIZE
Twin 26'x50'
Twin 26'x50'
Single 26'x50'
17' *
12' *
Single 26'x50'
Single 26'x50'
14' *
10' 4>
Single 26'x50'
LENGTH
(MILES)
11.99
20.38
13.53
3.00
12.80
61.70
8.27
12.45
2.00
2.29
25.01
19.50
106.21
COST IN THOUSAND DOLLARS
PER MILE
5,500
5,500
3,000
2,700
2,000
3,000
3,000
2,300
1,700
3,000
PHASE I
65,945
40,590
8,100
25,600
140,235
24,810
4,600
3,893
33,303
173,538
- Phase 3 Total Phase :
Calumet Branch - 36,650
DesPlaines Branch -35,000
Total Phases 1,
PHASE 2
112,000
112,000
37,350
37,350
58,500
207,850
TOTAL
252,235
70,653
58,500
381,388
5 71,650
2 & 3 $453,038
o
<£>
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TABLE 9
SUMMARY OF PROJECT COST
Tunnels (See Table 8) $453,038,000
Pumping Stations 50,000,000
Pump Discharge Conduits 3,000,000
Drop Shafts From Combined
Sewer Outlets to Tunnels 65,000,000
Drop Shafts From River to
Tunnels 6,000,000
Tunnel Outflow Controlling
Works @ Lockport 5,000,000
Subsurface Exploration 5,000,000
TOTAL CONTRACT COST $587,038,000
Miscellaneous Work (Use 5%) 29,352,000
$616,390,000
Engineering & Supervision, 10% 58,610,000
TOTAL PROJECT COST $675,000,000
Cost as of May, 1970
E.N.R. Construction Cost Index 1,417.41
210
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CONSTRUCTION PHASES
RECOMMENDED FIRST PHASE CONSTRUCTION
The authors recommend that the First Phase con-
struction be started at the earliest possible date in order
to meet the requirements of Water Quality Standards of the
State and Federal Governments. These standards require com-
pliance by 1978.
The First Phase construction of the Underflow-Stor-
age Plan would include the large conveyance tunnels under the
North Shore Channel; Chicago River and its North and South
Branches, and South Fork; and the Sanitary and Ship Canal; all
between the Wilmette controlling works and the outlet of the
Southwest Side Intercepting Sewer, Contract 13-A, an Under-
flow Sewer, just west of Harlem Avenue. The First Phase con-
struction would also include the conveyance tunnels beneath
the Calumet Sag Channel, Little Calumet and Calumet Rivers,
all lying between the outlet of the Calumet Intercepting Sewer,
Contract 18-E, an Underflow Sewer at Crawford Avenue and the
95th Street Pumping Station.
A new Underflow Sewer to the west through Skokie,
Illinois, and extensions of the Lawrence Avenue Underflow
Sewer to the north, would intercept combined sewer overflow
outlets along the North Branch of the Chicago River upstream
of its confluence with the North Shore Channel.
Drop shafts, connecting all combined sewer overflow
outlets along the route of the First Phase tunnels should be
constructed. Also the three major pumping stations for de-
watering the tunnels to the treatment plant facilities, must
be constructed under the First Phase work.
The First Phase would serve a tributary area of
about 240 square miles and have an underground storage of
about 7,000 acre-feet or the equivalent of 0.56 inches of
storage. Referring to Figure 8, and prorating for area
(300/240 x 7,000 AF = 8,000 AF), it appears that 95 percent
of the pollutants would be entrapped from the tributary
240 square mile combined sewer area.
The construction under the First Phase of the Com-
bined Underflow-Storage Plan, would greatly reduce the spill-
ages from 75 percent of the combined sewer outlets, covering
211
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80 percent of their tributary drainage area. It is anti-
cipated that the First Phase construction, coupled with
effluent improvements at the treatment plants will substant-
ially meet the waterway standards for many reaches of the
waterway system.
It is understood that the tunnel configuration, size,
elevation, storage volume and location may be modified some-
what as detailed engineering design progresses. However, the
following cost estimate for the First Phase construction is
believed to be conservative.
Underflow-Storage Tunnels $173,538,000
Three Pumping Stations 53,000,000
Drop Shaft Connections 50,000,000
Subsurface Exploration 4,000,000
Miscellaneous Facilities 12,000,000
$292,538,000
Engineering & Supervision 10% ± 28,962,000
$321,500,000
It appears that considerable benefit will be acc-
omplished at less than one-half of the total cost of the Com-
bined Underflow-Storage Plan by the construction of the First
Phase. It should be emphasized, however, that the First Phase
will not accomplish the basic criteria established. It will
not provide complete flood relief to prevent discharge of
river water to Lake Michigan, the needed relief from flooding
along the DesPlaines River and Calumet Waterways, nor will it
intercept combined overflow outlets from some 20 percent of
the combined sewer area. All of these requirements must be
included in the Second Phase work.
The schedule for completing the First Phase work
is becoming very critical. In order to have any possible
chance of meeting the compliance date of 1978, it is im-
perative that the First Phase engineering design be started
immediately.
212
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SECOND PHASE STUDY
Concurrently with the engineering design work of
the First Phase, a study should be made of the Second Phase.
There still remains a difference of opinion regarding the
most economical method of handling the runoff during excess-
ive storm periods.
The Combined Underflow-Storage Plan proposes stor-
age in transit and underflow conveyance through large tunnels
200 to 300 feet below the Calumet Sag Channel and Sanitary
and Ship Canal to a lower water surface at Lockport. The
Deep Tunnel Plan proposes to store all of the storm water run-
off in large underground mined storage chambers 600 to 800
feet below the surface, and in surface reservoirs, and to
produce and sell peaking power to defray a part of the cost
of the pumping-generating facilities and reservoirs. The
Chicago Drainage Plan proposes channel lowering and widening
to provide both surface storage and to improve conveyance
capacity. Also, such widening and lowering of water surfaces
would be of benefit to navigation.
The First Phase construction as set forth herein,
will be compatible with expanding under the Second Phase
along the lines of either of the three general plans proposed,
with only minor modifications thereto.
Mined storage chambers could be added at 600 to
800 feet below the ground level in the McCook and Calumet Areas
to form the lower reservoirs of a pump-storage system, as
proposed in the Deep Tunnel Plan. Siphon overflow shafts
could connect the Underflow-Storage tunnels in the shallower
Niagaran strata limestone formations. The Underflow-Storage
tunnels and pumping stations at the treatment plants under the
First Phase work, would handle the runoff from the small to
medium storms. In the excessive rainfall periods, runoff that
exceeds the Underflow-Storage tunnels would spill through the
siphon shafts to large mined reservoirs. The combined storage
of the First Phase Underflow-Storage tunnels, the low level
mined chambers and surface reservoirs would meet the criteria
set forth for both the flood control and pollution problems.
The First Phase construction would also eliminate
the need of providing retention tanks at the combined sewer
outlets as proposed in the Chicago Drainage Plan. Further,
studies with the computer water quality model would determine
the amount of additional underground storage that may be re-
quired to meet the waterway standards (SWB-15) for all
reaches.
213
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The waterway improvements for navigation and flood
control proposed in the Chicago Drainage Plan, would provide
the necessary outlet capacity. Studies may show that large
pumping facilities at the western terminus of the First Phase
Underflow-Storage tunnels are needed to lift the water to
the enlarged Sanitary arid Ship Canal and Sag Channel, during
the larger storm periods.
The First Phase construction, of course, can be
expanded, as outlined herein, as the Combined Underflow-
Storage Plan.
Extension of some of the Underflow-Storage tunnels
and Underflow Sewers in the Second Phase, will be required in
any plan, to intercept the combined sewers along the DesPlaines
River and northwest communities, and through the Little Cal-
umet River area.
A systematic study of all alternates should be
undertaken to determine the merits of each of the plans pro-
posed. It is by such a study that the best and most econ-
omical scheme from a benefit/cost standpoint can be deter-
mined for the Second Phase construction.
214
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SUMMARY AND CONCLUSION
Having outlined some of the major problems assoc-
iated with flooding of basements and underpasses and the
inadequacy of present rivers and canals to carry off flood
flows, it becomes apparent that major flood control fac-
ilities, at great expenditure of monies, are required.
The polluted condition of these open watercourses must also
be eliminated to meet the standards established by the State
and Federal pollution control agencies. A primary source
of pollution, namely, the spillages of polluted water from
combined sewers in time of storms, has been the subject of
this study and report.
Three separate schemes have been described for
solving these flooding and pollution problems in the Chicago
Metropolitan Area. These are the Underflow Storage Plan,
the Deep Tunnel Plan and the Chicago Drainage Plan.
A large relief sewer system proposed in the City's
Capital Improvement Program has been redesigned as an Under-
flow Sewer along the conceptual plan of the metropolitan area-
wide Underflow-Storage Plan. This Underflow Sewer in Lawrence
Avenue is now being constructed with the aid of a FWQA de-
monstration grant for $1,500,000. Since the time this project
was started, two other Underflow Sewers were placed under con-
struction by the Metropolitan Sanitary District.
The construction of these sewers has already de-
monstrated the anticipated quality of the dense dolomitic
limestone rock which is prevalent throughout the Chicagoland
area, and the structural ability of such rock to adequately
support the proposed large tunnels.
A complete description of the Underflow-Storage
Plan has been presented which will reduce the spillage of
pollutants to the surface waterways by over 98.5 percent and
provide the necessary flood control to handle the 100-year
frequency storm. Preliminary runs with a mathematical com-
puter water quality model indicate that the Underflow-Storage
Plan, together with improved sewage treatment plants, will
clean up the waterways so that they will be in compliance
with the State and Federal Standards.
It is recommended that the First Phase of the
Underflow-Storage Plan, which would include the construction
of tunnels along the North Shore Channel, Chicago River System
and Sanitary and Ship Canal between Wilmette Controlling Works
and Harlem Avenue be started immediately. Also, this First
215
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Phase should include tunnels along the Sag Channel, Little
Calumet and Calumet Rivers between Crawford Avenue and the
95th Street Pumping Station. Drop shaft connections and
pumping facilities would be constructed along the route of
the tunnels under the First Phase work.
It is estimated that the First Phase would cost
approximately $322,000,000 and would provide a direct bene-
fit to a 240 square mile tributary combined sewer area.
Pollution quantities which now overflow to the waterways in
time of storm from that area, would be reduced by 95 percent.
The First Phase work can be expanded in the Second
Phase along the lines of either the Underflow-Storage Plan,
the Deep Tunnel Plan, or the Chicago Drainage Plan. It is
further recommended that a complete conceptual study of the
Second Phase work be done concurrently with design and con-
struction of the First Phase.
216
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ACKNOWLEDGEMENTS
This report was prepared by the Bureau of Engineer-
ing, Department of Public Works, City of Chicago; and review-
ed by the Division of Waterways, Department of Public Works
and Buildings, State of Illinois; and the Engineering Depart-
ment of the Metropolitan Sanitary District of Greater Chicago.
217
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BIBLIOGRAPHY
1. Report on the Illinois River System, "Water Quality
Conditions", Part 1 Text, by the U.S. Public Health
Service, Great Lakes - Illinois
River Basins Project, January 1963.
2. "Illinois Sanitary Water Board, Rules and Regulations
SWB-15", Water Quality Standards, Adopted June 28, 1967
and Reapproved March 5, 1968.
3. "Illinois Sanitary Water Board, Rules and Regulations
SWB-8", Illinois River and Lower Section of DesPlaines
River, December 15, 1966.
4. "Combined Underflow-Storage Plan for Pollution and
Flood Control in the Chicago Metropolitan Area" by
the City of Chicago, Department of Public Works,
Bureau of Engineering, September 1969.
5. "Flood and Pollution Control, A Deep Tunnel Plan for
the Chicagoland Area" by Harza Engineering Company and
Bauer Engineering, Inc., May 1966.
6. "Chicago Drainage Plan" by the State of Illinois
Department of Public Works and Buildings, November, 1968
7. "The Chicago Underflow Plan for Flood and Pollution
Control", by the City of Chicago, Department of Public
Works, Bureau of Engineering, 1966.
8. A Report to the Technical Advisory Committee on Flood
Control, "Composite Drainage Plan for the Chicago Area",
by the City of Chicago, Department of Public Works,
Bureau of Engineering, September 1968.
218
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SECTION 6
DETROIT
SEWER MONITORING
and
REMOTE CONTROL
Research Project, Aiming at the Reduction of Combined Sewer
Overflow Pollution in Detroit using System Monitoring &
Remote Control Techniques
FEDERAL WATER
QUALITY ADMINISTRATION
DEPARTMENT OF THE INTERIOR
by
Detroit Metro Water Department
735 Randolph Street
Detroit, Mich. 48226
F.W.Q.A. RESEARCH & DEVELOPMENT PROJECT 11O2OFAX
June,197O
-------
SEWER MONITORING AND REMOTE CONTROL-DETROIT
ABSTRACT
Detroit is faced with the problem of preventing pollution of the Detroit and
Rouge Rivers from its combined sewer system overflows. As an alternative
to undertaking a dubiously effective sewer separation program, estimated to
cost in excess of two billion dollars, the Detroit Metro Water Department has
installed the nucleus of a sewer monitoring and remote control "system " for
controlling the pollution from the combined overflow from many small storms
at a cost of slightly over two million dollars.
The "system" includes telemetering rain gages, sewer level sensors, overflow
detectors, a centrally located computer and data-logger, and a centrally
located operating console for controlling pumping stations and selected regu-
lating gates. Installation has been virtually completed and now enables apply-
ing such pollution control techniques as "storm flow anticipation", "first flush
interception", selective retention" and "selective overflowing".
An evaluation of the effectiveness of this initial installation will serve as the
basis for determining what additional pollution control facilities are required,
what suburban monitoring and remote control is essential, what computer
related equipment for pump and valve control can be used for more effective
pollution control, what automatic sampling and analysis will be most valuable
in the synchronous operation of the sewerage system and what design para-
meters should be used in the construction of new or supplemental sewers or
treatment facilities.
KEYWORDS: 1. Combined Overflows 5. First Flush Interception
2. System Monitoring 6. Selective Retention
3. Remote Control 7. Selective Overflowing
4. Storm Flow Anticipation
"This interim report is submitted in partial fulfillment of Research and
Development Project 11020 FAX between the Federal Water Quality
Administration and the Detroit Metro Water Department.
221
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TABLE OF CONTENTS
SECTION TITLE PAGE
Abstract 221
List of Figures 225
List of Tables 226
I Introduction 227
Possibilities of Monitoring & Remote Control 229
Potential Benefits 230
Monitoring Vs Cost of Separation 230
Detroit's Topography 231
Detroit Sewerage System Characteristics 233
II Monitoring and Remote Control Equipment 239
Rain Gages 240
Level Sensors 240
Telemetering Signals 245
Proximity Sensors 245
Electrode Sensors 250
Digital Computer 250
Data Loggers 250
Teletypewriter 255
Operator Console and Monitor 255
Central Control Panel 255
Remotely Operated Pump Stations 255
Remote Operated Gates 257
III Operation of the System 259
Anticipating Major Storms 259
Anticipating Small Storms 260
Small Storm Storage 260
Storage in Sewer vs Sedimentation 262
Detroit Experience with Sewer Deposits 262
Quality of Overflow 266
Quantity of Overflow 266
"Selective Retention" & Selective Overflowing" 273
Sampling 273
Monitoring Benefit - Better Regulator Settings 276
Monitoring Benefit - Effect on Rouge Interceptor 276
Suburban Flow 277
Start-Up Problems 277
Construction, Contract and Equipment Problems 277
223
-------
CONTENTS (Continued)
SECTION TITLE PAGE
IV Post Construction Evaluation Plan (1970) 281
V Future Objectives (1971-75) 282
VI Acknowledgement 283
APPENDIX A 285
224
-------
LIST OF FIGURES
NUMBER TITLE PAGE
1 Service Area of the Detroit Metro Water
Department Wastewater Treatment Plant 228
2 Detroit's Original Watershed 232
3 Areas Requiring Storm Pumpage 234
4 Combined vs Separated Areas 235
5 Float Controlled Regulator 236
6 Telemetered Rain Gage Areas 241
7a Rain Gage Installation 242
b Rain Gage Mechanism 242
8 Flow Diagram of Monitored Points
on Detroit Sewer System 243
9 Detroit Level Sensor 244
10 Level Sensor Installation 246
lla Pedestal for Level Sensor 247
b Power & Telephone Service Drop on Utility Pole 247
c Slot in Pavement for Condu it from Pedestal to Manhole 247
12a, b Typical View of Equipment inside of a Pedestal Cabinet 248
13 Proximity ffensor Installation 249
14 Electrode Sensor Installation 251
9 S?
15 Tone Signal Receivers
16 Digital Computer 252
17 Typewriter for Data Logging 253
18 Monitor and Teletypewriter 2-^
19 Profile - Rivard Sewer - Bluehill System 254
225
-------
FIGURES (Continued)
NUMBER TITLE
20 Central Control Panel
21 Freud Storm Pumping Station
22 Translatory Wave in Storm Sewer
23 Storage Possibility in Conner Sewer
24 Flushing Gate Installation
25 Variation of Unit Amounts of BOD '68
26 Variation of Unit Amounts of BOD '69
27 Variation of Unit Amounts of Oils & Greases '68
28 Variation of Unit Amounts of Oils & Greases '69
29 Variation of Unit Amounts of Suspended Solids '68
30 Variation of Unit Amounts of Suspended Solids '69
3la Sampling Vehicle
b Hydraulic Hoist on Sampling Vehicle
c Automatic Sampling Unit
d Portable Battery Charger on Sampling Vehicle
32 Possible Remote Sluice Gate Location
33 Combined Sewer Outfalls in the Detroit System
LIST OF TABLES
TABLE TITLE
I-A Average of Daily Grab Samples Jun-Dec '68
I-B Average of Daily Grab Samples Jun-Dec '68
I I-A Average of Daily Grab Samples Jan-Jul '69
I I-B Average of Daily Grab Samples Jan-Jul '69
PAGE
256
256
261
263
265
267
268
269
270
271
272
275
275
275
275
278
279
PAGE
286
287
288
289
226
-------
SECTION I
INTRODUCTION
The pollution resulting from combined sewerage systems is the one common
problem which has plagued all sanitary engineers doing work in the older
cities of this country. Overflows from these combined sewers (those which
carry sanitary sewage, storm water runoff and industrial wastes) have been
increasing and they may now be classified as one of the primary pollution
problems of this era. Our forebears built these combined systems, which
economically carry dry weather flow to interceptors, with the thought in
mind that overflows would be infrequent, of relatively short duration and
sufficiently dilute so as not to harm receiving waters. However, with the
growth and development of our urban centers (which appear to have ever
expanding impervious surfaces) these same sewers now spill a high portion
of this mixed flow, untreated, to receiving streams during runoff from major
storms. This report deals with one approach toward controlling this major
cause of degradation to our nation's vital natural resource.
The Detroit Metro Water Department (DMWD) is a regional agency that
serves 70 communities in Southeastern Michigan with drinking water and pro-
vides wastewater interception and treatment service to 55 communities.
(These figures as of JANUARY 1970) It has contracted to serve dozens of
additional communities in the near future. Basically, the pure water needs of
40% of the population of the State of Michigan are served by DMWD and the
same agency is providing wastewater disposal service to 30% of the State'
populace.
The agency also has the responsibility for constructing, operating and
maintaining the sewer collection, the drainage and the water distribution
system within the City limits of Detroit. The suburban communities which
are served by DMWD have each retained responsibility for the operation and
maintenance of their local sewer collection and water distribution networks.
The map on Figure 1 shows the status of wastewater disposal service in
Southeastern Michigan as of January 1970.
The entire DMWD service area is presently connected to a 1200 M.G.D.
single treatment plant located near the junction of the Detroit and Rouge Rivers.
The capacity at the plant is being expanded and the facilities are being upgraded
under an agreement with the Michigan Water Resources Commission. This
agreement is one of the resulting actions to come from the 1965 Conference on
Pollution of the Detroit River, Lake Erie and their Tributaries. Construction
at the plant site began in July of 1969 and the advanced treatment facilities now
being installed will remove between 80 and 90% of all impurities such as sus-
pended solids, dissolved organics, phosphates, phenols and oils as well as
keeping coliform bacteria limits to less than 1000 per 100 ml.
227
-------
i
I :
'
PROPOSCO FUTURE
'} DMWS WASTEWMER TREATMENT
PLANT
OA ~K\L A NO
f
MAC OMB
CHESTERFIELD
.-HIGHLAND WHITE
LAKE
,
vjERCE \--\
l' U'w.BLOoV
FIFI n %
MAICOMB C
sr c L A i R
UPERIOR CANTON
AREA PRESENTLY SERVED
AREAS BEING ADDED-1969- 72
AREAS SERVED BY OTHERS (WAYNE CO.)
POSSIBLE FUTURE EXPANDED SERVICE AREA
AUGUSTA • SUMPTER
EXISTING SEWERS & INTERCEPTORS
INTERCEPTORS-BEING CONSTRUCTED OR DESIGNED
POSSIBLE FUTURE INTERCEPTORS
PROPOSED FUTURE
. DMWS WASTEWATER TREATMENT PLANT
FIGURE I
SERVICE AREA
OF
DETROIT METRO WATER DEPARTMENT
WASTEWATER TREATMENT PLANT
-------
The Agreement with the Michigan Water Resources Commission also calls for
the City of Detroit to take immediate steps to decrease the frequency, magni-
tude, and pollutional content of all overflows of combined sewage, industrial
wastes, and storm water from the City's sewerage system to the Detroit and
Rouge Rivers. The Agreement further stipulates that a study be made of
methods and costs of achieving these desired reductions and this project is a
direct part of that study.
POSSIBILITIES OF MONITORING AND REMOTE CONTROL
In order to utilize the potential of such pollution control techniques as "storm
flow anticipation", "first flush interception", "selective retention", and
"selective overflowing", one needs to have instantaneous and accurate informa-
tion about the behavior of the overall sewerage system. This information must
include rainfall events taking place within (and without) the contributory drainage
area, sewer and interceptor levels, and the status of pumps, valves, and back-
water gates. It is of equal importance to be able to remotely control the pumps
and valves so that one may react in accordance with the data being received.
The Detroit Metro Water Department has been monitoring water pressures
and remotely operating water pumping stations and valves throughout the metro-
politan area for eight years. Utilizing this experience, DMWD studied the
possibilities of installing a sewer monitoring system with remote control of
sanitary and storm pumping stations and regulating gates. With the aforemen-
tioned pollution control techniques in mind, the following factors related to the
decision to install a monitoring and remote control system.
1. There are large areas served by pumping stations whose tributary
lines could be used as storage areas during small storms.
2. The grades of the sewers, either rectangular boxes or cylinders,
are relatively flat which would permit substantial storage under level condi-
tions, near the outfalls.
3. Interceptors along the Detroit and Rouge are fed through float-
controlled regulators equipped with sluice gates which appear to be adaptable
to conversion to remote controlled power actuated regulators.
4. Most of the 71 outfall points are equipped with backwater gates and/or
dams which serve as automatic retention devices.
5. Interconnections exist throughout the system which could be used for
flow routing if remote controlled gates are added.
6. From knowledge of the particular industries connected to certain
sewers, there apparently would be a wide variation in the quality of dry
weather effluent.
229
-------
7. To be able to evaluate any method which attempts reduce combined
overflows it is first necessary to establish the existing conditions.
Monitoring would allow the collection of these data.
POTENTIAL BENEFITS
With central system monitoring and remote control, the following benefits
appeared possible:
1. The sewerage system could be operated to completely contain a small
spot storm.
2. Runoff could be anticipated, sewers could be emptied and in readiness.
Grossly contaminated first flushes in areas adjacent to the interceptor could
selectively be captured, especially during large storms.
3. All flow near the end of a large storm could be held in the system for
subsequent treatment.
4. Regulators could be adjusted to get the most efficient use of the
interceptor and set to favor the most grossly contaminated inlets.
5. Backwater from floods entering unprotected outfalls in the northwestern
part of the City could be selectively controlled.
6. Information on the level of flow within the sewers would provide
sufficient lead time so that pumps could be operated to minimize basement
flooding in the east side areas which have no gravity relief outlets.
7. The flow to the wastewater plant from various segments of the City
could be better balanced.
8. The data collected could be used for deriving new design criteria which
would be of benefit for future improvements to the sewerage system.
MONITORING VS COST OF COMPLETE SEPARATION
Complete separation of the combined sewerage system of the City of Detroit
into separated storm and sanitary sewers has been estimated to cost over
$2 billion and would probably take from 30 to 50 years to accomplish. Separa-
tion would require excavation at nearly every house in the City to change the
connections, and appears also to have the following drawbacks.
230
-------
1. There is no assurance that all cross connections can be eliminated by
separation. Detroit has a separated area on its east side in which a single
storm water connection to the sanitary system can go undetected for 2 or 3
years even after the agency is aware that it probably exists and is causing
problems..
2. The first flush in a 100% storm sewer is highly contaminated.
Selective interception of this flush will undoubtedly be required in the future.
3. Time is a factor. System Monitoring and Remote Control could be
installed and in operation within two years -- rather than 40 years. The
benefits would begin immediately.
Detroit believes that storm anticipating, monitoring, storm storage and
remote control will be somewhat effective (but to a lesser degree) on larger
storms, such as rainfall rates of 2" per hour or greater. However, the
major advantage will be in retaining more of the runoff from smaller storms
which contribute the most highly contaminated overflows.
DETROIT'S TOPOGRAPHY
The terrain in Detroit is gently sloping to flat. There are no hills within the
City limits. From a high elevation of 667 ft. (USGS) above sea level at
Wyoming and Eight Mile to the mean elevation of 576 at the Detroit River,
there is a fall of 91 ft. in a sewer distance of 14.5 miles. This gives an
average fall of only 1.17 ft. in a 1,000 ft. length. The net hydraulic fall is
even less since the lateral sewers at the upper extremity of the system are a
minimum of 8 ft. deep. This flat condition makes for nearly horizontal
slopes to the gravity sewer system with particularly flat grades in the lower
reaches where possible volumetric storage can be affected.
The ground slopes largely from the north to the south except in the area of
the Rouge River Valley where the ground slopes to the east and to the west
toward the river.
Figure 2 shows the original watershed within Detroit.
The original sewers generally followed the slope of the drainage basins . The
north and northeast sections slope gently into what were known as Conner
Creek and Fox Creek, respectively. The central portions of the city slope
gently directed to the Detroit River. The western portion of the City is
drained by the Rouge River which meanders through northern suburbs,
through Detroit and through southwestern suburbs to reach the Detroit River.
When relief of the original sewers was needed, the relief lines were con-
structed at right angles to the rivers in order to get the shortest lengths and
steeper grades.
231
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EIGHT MILE
•
FIGURE 2- DETROIT'S ORIGINAL WATERSHED
-------
Detroit's sewers were installed by tunnel or open cut method through glacial
till or lacustrine clays. No rock ledges were encountered in building these
tunnels.
DETROIT SEWERAGE SYSTEM CHARACTERISTICS
Approximately 85% of the 139 sq. miles within Detroit can be drained by
gravity sewers and 15% of the area requires lift pumps. Nearly 98% of the
sewerage system is of the conventional combined type.
Figure 3 shows the areas of the City of Detroit served by large sewerage
lift stations. Stormwater from the Bluehill Pumping Station even requires
repumping by the Freud or Conners Stations for discharge to the Detroit
River.
The diked area in southeast Detroit, which was reclaimed from the Detroit
River by enterprising real estate men over forty years ago during a period
of low water, is several feet below River elevation.
Figure 4 shows a small area north of Mack Avenue which was developed as a
separated sewer system. The sanitary flow outlets by gravity to the Detroit
River Interceptor at Alter and Jefferson. However, to accelerate the street
flow and roof conductor runoff, all storm flow from the district is drained
into the deeper Conner-Freud storm pumping complex.
The Detroit River Interceptor is located adjacent to the river. It varies in
size from 8 ft. at the east city limits to 16 ft. I.D. at the treatment plant.
It flows by gravity from the Grosse Pointe area to the treatment plant with
only one lift, at the Fairview Sanitary Lift Station.
Along the Rouge River the Oakwood-Northwest Interceptor in the Rouge Valley
intercepts sanitary flow from the various combined outfalls along the Rouge
River and brings this flow to the treatment plant. It crosses under the River
at several points by inverted siphon. This interceptor varies in size from
4 ft. to 12'-9" I.D.
Figure 5 shows a typical float controlled regulator which allows flow into the
interceptors. These regulators are normally set to close when flow in the
interceptors nears the 7/10ths point.
Some 77% of the regulators were manufactured by Brown and Brown Co. and
are actuated by tell-tale pipes connected to the interceptor. When water
levels in the interceptor rise, the float rises in the float chamber, which in
turn, through a series of chains or cables and a transmission shaft, allows
the regulator gate to close, shutting off combined flow into the interceptor
before the interceptor floods out. When the regulator closes, all of the
combined flow is then carried to the outfall and into the receiving stream.
233
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PUMPED AREAS
i i
•
i
OAKWOOD
PUMPING STATION
FIGURE 3
LOCATION
OF
DETROIT STORM PUMPING STATIONS
AND
AREAS SERVED.
-------
a MILE RO
I •
' '
SEPARATED
7fAREA
WOgtPOINTt
INTERCEPTOR
OHOSSE PCKNTl
JHORES
FIGURE 4
COMBINED « SEPARATED
AREAS
IN DETROIT
-------
hO
FIGURE 5
DIAGRAM
SHOWING TYPICAL OPERATION
OF
FLOAT CONTROLLED-SEWER REGULATOR
-------
Wherever needed, Detroit has installed protective backwater gates or dams
downstream of the regulator to prevent backflow from entering the inter-
ceptor from the rivers. Some outfalls are lower than the average river
levels and during periods of high water many outfalls are completely sub-
merged.
237
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SECTION II.
MONITORING AND REMOTE CONTROL EQUIPMENT
The following equipment^ has been installed by this project:
(a) 14 telemetering rain gages supplied by Belfort Instrument Co.,
Baltimore, Maryland.
(b) 80 telemetering sewer level sensors, 40 telemetering interceptor level
sensors, and 4 telemetering river level sensors. The sensor cells were
fabricated by the contractor to DMWD specificat ions and the transmitters
and receivers were supplied by Quindar Electronics, Inc., Springfield,
N. J.
(c) 30 telemetering proximity sensors on backwater gates supplied by
Minneapolis - Honeywell.
(d) 38 telemetering probe-type dam overflow sensors, which consist of a
set of electrodes with an amplifier, supplied by B/W Controller Corp.,
Birmingham, Michigan.
(e) 1 central digital computer with drum and disc memory Model PDP8 supplied
by the Data Master Division of the Bristol Co., Glen Cove, New York.
(f) 3 data loggers (computer controlled typewriters) with 30 inch platens
supplied by I. B. M. Corp.
(g) 1 teletypewriter for input, output and alarm supplied by Teletype
Corporation, Skokie, Illinois.
(h) 1 operator console supplied by the Data Master Division of the Bristol
Co., Glen Cove, New York.
(i) Central Control Panel containing the following equipment:
8 sets of equipment for the remote control and monitoring of pumping
stations supplied by Quindar Electronics Inc., Springfield, New Jersey.
5 sets of equipment for the remote control and monitoring of sluice and
flushing gates, also supplied by Quindar Electronics. The gates were
supplied by the Rodney-Hunt Co. of Orange, Mass, and the motor
1. All commercial products were purchased on a low bidder basis and mention
by name does not imply endorsement by the Federal "Water Quality Adminis-
tration or the Detroit Metro Water Departm ent.
239
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operators for these gates were from Philadelphia Gear Corp.,
Philadelphia, Pennsylvania.
18 recorders for pump station suction and discharge lines supplied by
the Bristol Co., Glen Cove, New York.
Details of the aforementioned equipment are explained below.
(a) Rain Gages
Figure 6 shows the locations of the telemetering rain gages. These are
tipping bucket gages which telemeter a pulse signal to the central-control
office for every 1/100 of an inch of rain. The gages, one of which is shown
on Figure 7a are for the most part installed on the flat roofs of DMWD
buildings. Figure 7b shows a close-up view of the gage mechanism.
These roofs are not perfect sites, as an exposed location in an open field
would possibly be less influenced by wind effects, but all such open sites in a
big city would be subject to vandalism, so the compromise of a location on a
low flat roof was made.
Whereas the tipping bucket gages are primarily for operation, the existing
set of 16 spring wound 8-day clock weighing rain gages (which are generally
adjacent to the new gages ) are being kept in service as an accuracy check and
for the purpose of historical record.
(b) Level Sensors
The location of telemetering level sensors are shown on Figure 8. These
are located on all the larger trunk line sewers 10 ft. diameter and larger,
plus on certain critical smaller upstream lines. Level sensors are also
installed at all wet wells of all pumping stations.
Detail of Detroit Level Sensor
The sewer level sensor, as shown on Figure 9 consists of a 2" I.D.
polyvinylchloride tube some 11 inches long to which is attached a 1/4" O.D.
nylon tube. Dry air is entrained in the cell and tubing. When the sewer
water level rises, it slightly compresses the trapped air in the pressure
cell which in turn compresses the air in the 1/4" nylon tube which actuates
a transmitting bellows located in pedestal cabinet on the surface.
240
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FIGURE 6
AREAS SERVED
f
TELEMETERING RAIN GAGES
WTMIES3CNS POJTGONS
CITY «• DETROIT
-------
FIGURE 7CL-RAIN GAGE INSTALLATION
FIGURE 7b-RAIN GAGE MECHANISM
242
-------
FLOW DIAGRAM OF MONITORED
POINTS ON DETROIT SEWBH SYITEM
-------
PVC CAP SOCKET TYPE
WITH J^ TAPPED MOLE-]
NYLON TUBING
NYLON FITTING
ID. PVC PIPE
BOTTOM
FIGURE 9
DETAIL OF LEVEL
SENSOR
INSTALLATION
244
-------
These sensors are installed as shown in Figure 10 in existing manholes along
sewers and interceptors. The cell is slanted about 15° downstream to avoid
being fouled by debris. Near the surface, the nylon tubing is inserted in a
3/4" metallic conduit which has been installed some 3" deep in a cut slot in
the asphalt or concrete pavements. The slots were filled with either hot
asphalt or epoxy concrete, respectively, to quickly restore the street to
service.
Figure lla shows a typical sensor pedestal located about 3 ft. in back of the
curb. Figure lib shows the power and telephone service drops brought in at
the nearest utility pole and Figure lie shows a typical slot cut in the pavement
running from the pedestal to a manhole. Figures 12a and 12b show a typical
view of the equipment inside the cabinet on the pedestal.
The equipment consists of the pressure bellows, a signal transmitter, and
level indicator. The 1/4" nylon tubing from the manhole plus the power line
bringing in 120 V. A.C. current and the telephone leased line all enter the
pedestal from underground. Power is purchased on a yearly basis, therefore
no meter is required at these installations.
Telemetering Signals
The tone transmitter is a single rectangular box which was shown in the upper
left hand of Figure 12b. The signal cycle is 5 seconds in length with the first
second being a null tone to clear the receiver.
At the level sensing points the cells are calibrated so that if it had 40 feet of
water above it, the transmitter would generate a 4-second analog signal. This
4-second signal is considered to a 100% reading and coupled with the 1 second
null tone we have a 5 second cycle. Therefore, if the height of the water was
20 feet the transmitter would send out a 2-second signal which would be
equivalent to a 50% reading. The signal would then be 3 seconds long with
the first second again being the null tone. The transmitter continuously broad-
casts this signal on an assigned frequency. As many as 10 different signals
are multiplexed over a single leased telephone line from the field installations
into the central computer.
(c) Proximity Sensors
At the locations shown on Figure 13, a sensor block of ferrous metal is attached
to the backwater gate and placed in series through a magnetic coupling with the
proximity sensor. A continuous discrete signal is transmitted rntil the gate is
opened. When the gate is opened, the circuit is broken and an "open " signal is
recorded on the circuit.
245
-------
FIGURE 10
TYPICAL LEVEL CELL
INSTALLATION
IN
SEWER MANHOLE
246
-------
i
;
I
II
I Ml
FIGURE lla-PEDESTAL FOR
LEVEL SENSOR
FIGURE lie -SLOT IN PAVEMENT
FOR CONDUIT FROM
PEDESTAL TO THE
MANHOLE
FIGURE lib-POWER &
TELEPHONE SERVICE
DROP ON UTILITY POLE
-------
i •
!
FIGURE I2a FIGURE 12 b
TYPICAL VIEW OF EQUIPMENT INSIDE OF A PEDESTAL CABINET
-------
/-TIMBER BACKWATER GATE
CLEARANCE AS REQUIRED
PROXIMITY SENSOR
CONDUIT FITTING
FILLED WITH DUCT
SEAL-7 [^SIGNAL WIRE
V CONDUIT TO JUNCTION
SENSOR BLOCK
TONE SIGNAL-
TRANSMITTER
=»ROXIMITY SENSOR
BACKWATER GATE
HIGH WATER LEVEL
LOW WATER LEVEL
. - = - "=" T$X- .y -^ /«V^- vil '«-.
w -y. # a; 4, ^ . ;i- .A :«, y.A. ' V
'• ' - -
BACKWAT ER GATE CHAMBER
FIGURE 13-PROXIMITY SENSOR INSTALLATION
249
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(d) Probes
At dams or weirs, as shown on Figure 14, a two-element probe is anchored
upstream of the dam and slightly above the dam crest. When both elements
are wet, the circuit is completed, the continuous discrete signal is interrupted
and an "open" signal is recorded on the circuit.
(e) Digital Computer
The tone receivers are arranged as a battery of interchangeable modules
directly adjacent to the computer as shown on Figure 15. There is a receiver
for every transmitter, which is tuned to the same frequency as the transmitter.
The signal interpreted by the tone receiver is next transmitted through relays
to the computer.
Since the tone signals are transmitted on differing frequencies and several
signals are multiplexed on one leased phone line, they must be unscrambled
by the tuned receiver units.
The computer shown on Figure 16 receives these various signals. This
device in turn computes and totalizes rainfall data from the rain gages and
depth of flow data from the level sensors.
This is a program type of digital computer with a disc-drum memory. There
is space to add three additional memory discs at a later time. It has a pre-
sent capacity of 36,000 words of memory.
(f ) Data-Loggers
The computer actuates a bank of three special long platen electric typewriters
as shown on Figure 17.
The sewer levels and status of outfall sensors are tabulated in double space
columns. The rainfall data are tabulated in two lines of figures (single space)
under the heading for the given gage. The upper figure is the calculated rainfall
intensity in inches per hour during the preceding five minutes, with the
cumulative total rain in inches tabulated directly below the calculated rate.
These data are routinely tabulated every hour during dry weather, but are
actuated to 15 minute or 5 minute tabulations either by rainfall of .01" or by
higher flow conditions in the combined sewers.
Typical sewer or interceptor levels are tabulated on the typed sheets showing
levels, say at points 3, 2 and 1. The typed levels show the actual depth of
flow at these sensor points. These tabulated data inform the central control
operator that storm flow will be arriving at a pump station or remotely
operated regulator. As an example, Figure 19 shows the profile of the
Rivard sewer which flows into the Bluehill Storm Pumping Station. With the
level information and the profile the operator can visualize the incoming
flow and decide on a course of action. The central control office has been
furnished a file of such profiles for each main trunk line sewer flowing to a
pump station or remotely operated regulator.
250
-------
I 9
Ul
;
1
t
i
-POWER 1 TELEPHONE
CIRCUITS
CONDUIT
V- LEVEL INDICATOR A
I/ TRANSMITTER
-PEDESTAL
STREET PAVEMENT
: Y ' >TS
I i I' •****
L-_J M
1 IURICO CAM.E
I CMMVIN* »«Wt*»TCH»t tWMAL )
L-J
CLEANOUT PLUG
UPPER ELECTROOE
VTOP OF 0AM
OWER ELECTRODE
WATER SURFACE
TYPICAL ELICTHQOC
FIGURE 14
SENSOR INSTALLATION
FOR OVERFLOWS
AT
DAMS OR WEIRS.
-------
[\5
tn
i >
FIGURE 15-TONE SIGNAL
RECEIVERS
FIGURE 16-DIGITAL COMPUTER
-------
FIGURE 17-TYPEWRITER FOR DATA LOGGING
FIGURE 18-MONITOR AND TELETYPEWRITER
253
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IJO
III
1
m
• .
FIGURE 19-PROFILE - RIVARD SEWER- BLUEHILL SVSTEM
-------
(g) Teletypewriter
The typewriter for programming the computer is shown on Figure 18.
Changes of instruction to the computer are given through this machine.
This teletypewriter will also instantaneously print data on any called point;
high and low level alarms or communications outages.
(h) Operator Console and Monitor
The operator console which is also a monitor shown in Figure 18 allows the
personnel at the control center to call for a complete print out on the data
logger at any time. This equipment may also be used to monitor one specific
level sensor so that observations may be made of the instantaneous changes
taking place between data logger printouts.
(i) Central Control Panel
All present operation of the sewerage system pumps and valves is manual
from the control center switchboard panel as shown on Figure 20.
Experience and parameters are being developed which will, in time permit
automated operation of the pumps. One program would control storm operation,
another would be for dry weather conditions and a third program would control
in-system storage.
A flow diagram is superimposed on the board to aid the operators in
controlling pumps and valves. Directly above each pump control is a recorder
showing the recorded elevation of the wet well and the discharge level of each
station. These telemetered elevations are furnished by a completely indepen-
dent system of transmitters and receivers, therefore the recorders continue
to function even if the computer is temporarily out of service. This allows
the operators to act in the event of an emergency.
The central portion of the pump control panel which is shown in Figure 20
allows the remote control of a sanitary pump station, a storm station and also
monitors which pumps are operating at the wastewater plant. Adjacent and to
the left of the pump control switchboard is the switchboard which controls the
regulating gates and flushing gates. The operation of these gates is controlled
from the central office based on the telemetered information which comes in on
the three computer operated typewriters.
Remotely Operated Pumping Stations
Figure 21 shows the inside of one of the remote pumping stations. The
conversion involved only the addition of relays and some minor electrical
work. There is a roving maintenance man who visits the remotely operated
stations daily when they are not pumping and once every shift during periods
of pumpage.
255
-------
I * I
FIGURE 21-FREUD STORM PUMPING STATION
256
-------
Seven storm and/or sanitary pumping stations are operated remotely from the
central control panel. The pumps of one stormwater station and the waste-
water plant are not remotely operated but are monitored by the central
control office.
There is no early plan to operate the Conner Storm Pumping Station by remote
control as this station is over 40 years old. The pump impellers are raised
and require manual priming. Remote operation will undoubtedly be considered
at a later date. Operation of the pumps at the Wastewater Plant and Conners
Storm Station are coordinated with the other stations in the system by tele-
communication from central control with the operators on duty at these loca-
tions .
Remote Operated Gates
In order to selectively load the interceptor system, it was desirable to
remotely operate regulators at Warren-Pierson, at Michigan-Southfield, and
at Baby Creek. The existing sluice gates at these locations are being modified,
to accept motor operators and the work should be complete by the spring of
1970. These locations were shown on Figure 8. These three points regulate
flow from approximately 37% of the City.
The installation of flushing gates at the 3 barrel Conner sewer is discussed
later.
At the Conner's Station, provisions will be made to remotely operate the
regulating gates which control the flow entering the interceptor from the
Conner's Gravity Sewer.
257
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SECTION III
OPERATION OF THE SYSTEM
The basic concept of Monitoring and Remote Control is that as a storm moves
across the City from west to east (the usual route) , the operators at the
Central Control Center begin to act in accordance with the data received to
apply the pollution control techniques that were mentioned earlier. (The inter-
ceptor may be well pumped down to accept more flow, a small storm may be
retained, storage may be effected within the pumped system, and the first
flush of a storm may be better retained. All of these steps would be cen-
trally controlled.) This concept of actually operating a combined sewerag e
system is snow possible since the above described equipment provides
not only the data required to make decisions but also provides the means by
which affirmative action can be taken to better utilize the full potential of the
available storage capacity. It is no longer necessary to build a system and
leave it buried underground, more or less forgotten, until problems arise from
overloading, sludge build up, or flooding.
The following discussion is based on the limited experience that DMWD has
had through 1969 with the components of the system that are in operation. The
remote controlled sluice gates have not been placed in service at this time
(January 1970) and therefore that portion of the discussion will be theoretical.
Although the primary aim of this project is the reduction of combined overflows
it must be kept in mind that this goal must be accomplished in such a manner
as to avoid endangering the health and property of the local citizens. The use
of basements as detention basins is not a justifiable alternative to preventing
the occurence of a combined sewer overflow. Therefore, the discussion of
the different safety factors and back-up systems of this project should be of
interest to all readers.
ANTICIPATING MAJOR STORMS
The network of 14 rain gages gives the ability to anticipate the impact of a
major storm. The four western gages are from 3 to 7 miles west of the
City of Detroit city limits since a majority of storms come from this direc-
tion. This gives the central control operators from 3 hours to 6 hours of
lead time to have the system pumped down in order to store a small storm
(by taking advantage of storm travel time and the running time in the barrel).
During May and June of 1969, the control center operators began utilizing
these rainfall data to pump down the levels in interceptors and selected storm
barrels to determine how much storm overflow they could prevent. The gate
monitors were already in operation at this time. The operators found that they
were able to entirely contain certain spot storms, plus holding several
259
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scattered 1/4" to 1/2" city wide rains on various occasions. It appears that
the concept of "anticipating" a rain is easily understood by the operators and
in-line storage can be accomplished.
When storing water in the low level barrels and in the wet wells, there is a
hazard to the storm system in the event of a sudden intense storm.
This possibility is illustrated on Figure 22 which shows a condition which can
occur at several of the storm pumping stations. The flow from an intense
storm tends to suddenly fill the barrel with the higher level flow, which
travels faster than lower level flow, thus overtaking the earlier part of the
storm. V- travels faster than V4 and V. travels faster than V^, and so on.
Thus one can have a sudden wall of water, or translatory wave, as shown in
Stage III arriving at the pump station, which without monitoring, would not be
expected at the station and could cause extensive flooding. In certain cases,
this phenomenon could lift manholes in the street with the surge pressures.
The monitoring system should give the central control office enough lead time
to enable the operators on duty to anticipate this water. The operators can
then be prepared to turn on an adequate number of pumps when the water arrives.
(Pumps cannot be placed in operation until the starting water level is reached
in the wet well of the station. Severe damage can occur if the pumps are
started in a dry situation. )
ANTICIPATING SMALL. STORMS
In order to safely practice storm storage in the sewer barrels, it is necessary
to determine the correlation between the various storm intensities and the
recorded downstream stormflow. Thiessen's polygons, which were shown
earlier in Figure 6, are being used by DMWD rainfall analysts to establish
the relationships. From precipitation and flow data, the sewer hydrographs
of the maximum storm that can be stored in the various combined systems are
being developed for each area. It is quite obvious that each sewer system will
have a different storage capacity depending on imperviousness of the tributary
area, sizes of storage barrels, depth of storage in the trunk line, slope of the
barrel, depth of tributary arms, depths of basements and other factors.
For any program of planned storage, it is assumed that the wastewater
plant will be operating to capacity for a considerable time prior to, during and
after a storm.
SMALL STORM STORAGE
The in line storage of small storms within the barrel of the existing sewers is
dependent upon the following factors:
260
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STAGE I
WAVES SPACED
PROFILE
SCALES :HORZ. r=*ooo'
VERT. \'= 15'
STAGE II
WAVES OVERTAKING
130
120
I 10
STAGE III-
COMMON WAVE FRONT
FIGURE 22
TRANSLATORY WAVE IN STORM SEWER
DURING INTENSE STORMS
ASHLAND-ALGONQUIN 5TORM SYSTEM
40
i
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1. Size of box or cylinder
2. Slope of the conduit
3. Imperviousness of tributary area
4. Time elapsed since previous rain
5. Available height in sewer before gates open
6. Intensity or length of storm
7. The level of the river
8. Available capacity in the interceptor
Figure 23 shows a typical arrangement at an outfall which illustrates certain
of these factors. The depth of water (15 ft. ), the flat grade, the height the
water must be raised before gates open, and the effect of added storage if the
river level is raised even one foot should be noted. At the time the backwater
gate opens, there is a depth of 15.01 feet of water in the outfall with a total
quantity of stored water of 6.3 million cu. ft. in this outfall (assuming dead
level conditions). The water surface actually is not quite level but curves as a
backwater curve so there is somewhat more water upstream of the gate,
depending on the amount being diverted into the interceptor. In these situations
the backwater gates are the safety valves of the storage operation which could
open before there is danger of basement flooding. Available storage at the
various outfalls either upstream of pumps or backwater gates are being
calculated and tabulated for use by the system control operators.
STORAGE IN SEWERS - vs. - SEDIMENTATION
Any storage of runoff in larger trunk line sewers results in reduced velo-
city. Velocities below 2 ft. per second usually cause graded sedimentation
with coarse deposits occurring upstream where the velocities are still
relatively high and finer deposits downstream where the velocities are still
relatively high and finer deposits downstream where the velocities approach
zero.
DETROIT EXPERIENCE WITH SEWER DEPOSITS
Initially, storage is to be attempted at:
(1) The Hubbell-Southfield Outfall
a double box with each box 14'-6" wide x 12'
(2) The Baby Creek Outfall
a triple box each box being 14'-6" wide x 17'-6"
(3) The Conner Gravity Outfall
a triple box with each box 15'-9" wide x l7'-6"
(4) The five storm pumping stations
Detroit has had the following experience with sewer deposits:
262
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! -
<7
-
53B MILLION CU FT
(>CLM«0)
FIGURE 23
STORAGE POSSIBILITY
IN
CONNER QMAI/ITY BARRELS
SECTION AA
-------
About ten years ago the Baby Creek barrels and the Conner barrels were used
to store dry weather flow in order to moderate the variations in the hydraulic
load on the treatment plant. Sedimentation occurred in both the Conner and
Baby Creek barrels. About four years ago, when the treatment plant began
to operate the system at a lower hydraulic gradient, the deposits in the Baby
Creek were gradually moved to the treatment plant. Some initial problems of
overloading the grit chamber and breaking flights in the primary tanks did
result. The sediment deposits in the Conner barrels were not dislodged by
the lower gradient and the deposits still exist in the Conner barrel in substan-
tial amounts.
Therefore to take these expected sedimentary deposits into account, storage
in gravity sewers is being initially attempted only at locations where there
are double or triple barrels. This will give a built-in safety factor and also
will allow any required flushing to be accomplished by diverting flows.
Figure 24 shows the arrangement at the Conner sewer barrels, where
flushing gates will be installed at the point where the sewer changes from two
barrels to three barrels. This is the point where the deposits have not been
moved along by the lower hydraulic gradients at the wastewater plant. Slots
and guides have been installed in the transition chamber to permit lowering
and raising cable supported 7-ft. high gates in the 17-ft., 6-inch high combined
sewer barrels. A level sensor has been installed in a manhole located about
300 ft. upstream of the flushing gates. After a storm has occurred (during
which time the gates are up) and the level in the barrel is showing below the
7-ft. level on the sensor, two of the 7-ft. gates are lowered (say the number
3 and number 2 gates) as shown in Figure 24 which forces all flow into the
No. 1 barrel and will flush this barrel. Correspondingly, after four hours of
flushing of the east barrel, the No. 3 gate can be raised, and the No. 1 gate
lowered in order to flush the opposite west barrel. After about eight hours of
flushing, all gates are raised in order to be ready for the next storm. The
flushing at present is deliberately shortened in order not to overload the grit
chamber at the treatment plant. After all deposits have been cleaned from
all barrels, it will be possible to routinely flush each barrel in regular sequence
by a predetermined program.
There are two reasons for using only 7 foot high gates in these 17'-6" barrels.
The first was dictated by the available space between the crown of the sewer
and the street surface. The second reason is again the safety factor. If for
some reason the electronic remote control equipment should become inoperable
when the gates are in a down position it is possible for the flow to top the gates
without causing flooding upstream. A secondary system for raising the gates
utilizing power take-off equipment from a truck is also being installed.
264
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•
•:•
Q«* TYPICAL TRANSMITTER
BBL COMBINED SEWER
LEVEL SENSOR
ACROSS-OVER OPENINGS
3 BBL COMBINED SEWER
•'••
LUSHING GATES
FLUSHING GATES CLOSED
GATE OPEN
SECTION ArA
FIGURE 24-FLUSHING INSTALLATION
o
5LJUDGE
DEPOSITS
rvxxxxxxxxx^
f y xxx x x xx x X x.
xxxxxxxxxxx
x" w vx x xx xxxLx
-------
By using the "storm flow anticipation" technique coupled with in line storage
we feel that "first flush interception" is possible especially with the smaller
storm events and in the case of some scattered spot storms. Before discussing
the ideas of "selective retention" and "selective overflowing" it is first nece-
ssary to have some background on the quality and quantity of the overflows.
QUALITY OF OVERFLOW
The sanitary engineer and governmental agencies must establish criteria for
overflow quality. The pollutants that each sewer line carries vary from
outfall to outfall. These variations are rather wide. The system operator
must discriminate between outfalls in order to secure the greatest benefit
to the river.
Figures 25 and 26 graphically show two sets of the averaged variations in B.O.D.
which occur along certain trunk line sewers, as revealed by our program of
manual sampling. These data are tabulated in Tables I-A, I-B, 2-A and 2-B
located in APPENDIX I. For example, it is obvious that some consideration
must be given to intercepting as large a portion as possible of the high B.O.D.
in the Orleans sewer during a storm.
Figures 27 and 28 show two sets of the averaged variations in the oils and
greases from samples collected in 1968 and 1969 from the trunk sewers. There
are rather striking variations from sewer to sewer. Again it is obvious that
special consideration should be given the greases in the Orleans, the Baby
Creek and Flora sewers.
Figures 29 and 30 shows two sets of averaged variations of suspended solid
from the same samples. It can be seen from these figures that there are
many lines with a high concentration of solids and one would be hard pressed
to single out any particular line for special attention.
The tables also give data on the averaged variations of phenols and total
phosphate. It can be seen that two lines, Baby Creek and Dearborn (Miller)
Road) carry a high concentration of phenols while the phosphate concentra-
tions are fairly uniform throughout the system.
These charts represent variations during dry weather flow. The mass dia-
grams have not been adjusted as to quantity of flow and therefore, these are
concentrations. Corresponding data on storm overflow will be collected later.
QUANTITY OF OVERFLOWS
DMWD has developed a program for a computer which is independent of the one
used in the monitoring system. This program will determine the actual volume
of a combined overflow, in cubic feet, that is discharged from each major
outfall at the time of a storm overflow. The integration is rather complicated
under either open channel or full conduit conditions. The sensor points on
backwater gates and dams provide the elapsed time the outfall is spilling.
266
-------
EIGHT MILL RD
DGHT MILC flP
r )
&
• !
FIGURE
CITY OF DETROIT SEWER SYSTEM
MAP
SHOWING \*RIATION OF UNIT AMOUNTS
OF
BIOCHEMICAL OXYQCN DCMANO
FOUND IN ORYWEATHER FLOW AT THE
OUTFALLS SHOWN.
JUNE-DEC B8"
-------
EIGHT MIL F RO
E.IGHT MILE RD
'
'^
,,.
rtCURE 26
CITY OF DETROIT SEWER SYSTEM
MAP
SHOWING VARIATION OF UNIT AMOUNTS
OF
BIOCHEMICAL OXYGEN DCMAND
FOUND IN DRYWEATHER FLOW AT THE
OUTFALLS SHOWN.
JAN.-JULY'69"
-------
U8MT KUHB
FIGURE 27
CITY OF DETROIT SCWt* JYSTIM
MAP
SHOWING SMIATION Of UNIT AMOUNTS
OF
OIL AND GMAMI
FOUND IN DKYWCATHCft FLOW AT THE
OUTFALLS SHOWN
JUNE-DECW
-------
M
CITY OF DETROIT SCWCft SVlTfM
MAP
SHOWING VMIATION OF UNIT AMOUNTS
or
OIL AMOGMEAKI
FOUND IN DHYWCATHCN FLOW AT THC
OUTFALLS SHOWN.
JAN-JULY W
-------
i 3
i
riSURE 29
CITY OF DETROIT SEWER SYSTEM
MAP
SHOWING VARIATION OF UNIT AMOUNTS
Of
SutKNMD SOLID*
FOUND IN DRYWEATHER FLOW AT THE
OUTFALLS SHOWN.
JUNE DEC. -wr
-------
I .
-1
IJ
FIGURE 30
CITY OF DETROIT SEWER SYSTEM
MAP
SHOWING VARIATION OF UNIT AMOUNTS
OF
SU*PCNOCD SOLIDS
FOUND IN ORYWEATHER FLOW AT THC
OUTFALLS SHOWN.
JAN.-JULY 189"
-------
The upstream sewer level sensors give the varying hydraulic gradients
above the outfall. From these data, the total discharge is integrated to deter-
mine the total overflow to the river.
The present level sensors on 25 of the larger outfalls will permit calcula-
tion of the runoff from 86% of the area of the city. Measurement of the flow
from the balance of the smaller outfalls has been deferred because of the
capital cost for equipment. However, some very reasonable estimates of
the overflow can be secured since elapsed time of spilling is known, plus
average runoff per square mile from other comparable areas.
"SELECTIVE RETENTION" AND "SELECTIVE OVERFLOWING"
The preceding charts and the accompanying tables reflect a high level of
pollutants in sewers from industrial areas, slaughterhouses, laundries,
refineries or breweries. By contrast, sewers draining large parking lots,
parks or residential areas carry relatively low quantities of these same
pollutants. The levels of pollution will be expected to vary during each
period of overflow. To secure the greatest benefit to the river, consideration
must also be given to the duration of overflow as well as the major type of
pollutant being spilled. By developing criteria for each outfall the schedule
would call for allowing a higher percentage from the least polluted outfall to
overflow to the river in order to route the more polluted flow to the treatment
plant.
At present with three remote control sluice gates and the five storm pumping
stations it will be possible to begin using "selective retention" and "selective
overflow".
During storm events after the operators have learned the "storm flow anticipa-
tion" technique they then can close down the east side pumping stations allowing
storage to take place in the wet wells while leaving interceptor capacity for
the westerly sewers. As the storm moves across the City the remote sluice
gates in the west can be closed causing storage to begin in the westerly sewers
while the interceptor is then utilized to carry flow from the east.
In some storm events this may cause overflows to occur but it is expected
that much of the gross pollution can be entrapped for treatment. In the future
as more regulators are set up for remote operation these techniques could be
expanded.
SAMPLING
Under the piesent manual sampling program, grab samples collected during a
regular work week are refrigerated and delivered to the wastewater plant once
daily for standard analysis. One automatic mechanical sampler has been
installed for around the clock collection and several others are to be added
273
-------
later. These and supplemental samples collected manually during storms
will be utilized in comparing the degree of pollution under varying conditions.
It will also be necessary to collect samples from the receiving waters so
that comparisons can be made to see what improvements in water quality
have occurred.
Figure 31a shows the type of vehicle used by a 2 man crew for picking up grab
samples. This particular vehicle is also equipped to service the automatic
sampler located in the shed on the right side of the picture.
This shed is set over an open manhole and chained to the manhole steps to
prevent vandalism.
Figure 31b shows the hoist that is mounted on the truck for lowering the
sampler into underground locations. Figure 3lc shows a closer view of the
automatic sampler which takes a continuous sample but cycles every half
hour to fill a new bottle. With this machine 48 bottles will be filled in a
24 hour period. Variable time cycles and flow rates are possible. The
sampler may be operated on 120 volt AC or on 12 Volt DC current. The
location shown here uses two 12 volt automotive batteries wired in parallel
to provide the necessary amperage. Figure 3ld shows the portable battery
charger mounted in the truck. This charger is plugged into a 120 volt AC
power source each night so that fresh batteries are available for each days
operation.
The pumping unit for the automatic sampler is mounted on the manhole steps
below die sampling unit which shown in figure 31c. Since the pump is a
vacuum type the maximum lift is approximately 18 feet.
Different sampling heads are under investigation since the debris (paper,
rags, plastic from disposal diapers, etc. ) in a combined line has a tendency
to wrap around them and cause blockages.
The type of suction pump used by this sampler will continue to operate without
causing any damage to itself even if no flow is available to be drawn up into the
collection unit. The collection unit will continue to cycle each half hour yielding
empty bottles. Therefore it is expected that we will be able to sample combined
overflows at different outfalls by placing the unit in operation in a dry overflow
chamber and having it await a rain of sufficient size to cause an overflow to
occur.
2
This particular sampler is manufactured by Rock and Taylor of Birmingham
2. All commercial products were purchased on a low bidder basis and mention
by name does not imply endorsement by the Federal Water Quality Adminis-
tration or the Detroit Metro Water Department.
274
-------
! -
- I
-
a. SAMPLING VEHICLE AND SAMPLING STATION
b. HYDRAULIC HOIST
C. AUTOMATIC SAMPLER
d. PORTABLE BATTERY CHARGER
FIGURE 31 - SAMPLING EQUIPMENT
-------
England and is distributed in the United States by Megator Corp. of Pittsburg,
Pennsylvania. Other samplers of U.S. manufacture are now available.
MONITORING BENEFIT - BETTER REGULATOR SETTINGS
Prior to the installation of the monitoring system on the outfalls, there was no
way of knowing which regulators were slow or overloaded, sluggish, blocked
by debris or affected by peculiar conditions in their district. All backwater
gates and regulators, were however, inspected weekly but with the monitoring
system if an overflow continues to occur after all others have ceased, or if
an overflow occurs during a dry period, action can be taken immediately to
alleviate the problem.
Optimum condition
The optimum setting of a particular regulator is a setting which will take in
the maximum portion of the highest suspended solids, B.O.D. and other
pollutants and conversely to set other regulators on the cleaner water out-
falls to take in minimum portions without overloading the treatment plant.
Based upon the outfall sampling program, the regulators are being re-set
to more closely fit the optimum condition.
MONITORING BENEFIT - EFFECT ON ROUGE INTERCEPTOR
The Northwest-Rouge Interceptor lies within the Rouge River Valley and
actually makes four separate crossings of the Rouge River. As mentioned
before, only where the interceptor passes under the Rouge shipping channel
is there a normal inverted siphon crossing. The other crossings are made
by slightly lowering the grade for the crossing. These crossings do not
create true inverted siphons except under high storm conditions.
Along the upper three miles of the interceptor at outfalls which are not yet
protected by backwater gates, a major flood along the Rouge can flow back
across the diversion dams into the interceptor. This causes undue load on
the wastewater plant. The Lyndon, Schoolcraft, Puritan, Seven Mile Road
and Frisbee outfalls still require backwater gates. (See Figure 8 for locations)
In order to exclude this load of high river water, a sluice gate at Warren -
Pier son is being connected for remote operation so that the Rouge River
water could be shut off during flood stage.
Three river level sensors are installed at three critical points along the
Rouge River to enable the central control office to follow the height and
progress of a flood crest as it moves down the section of the river where
there is no backwater gate protection. As long as the crest is below the
lowest dam at Lyndon, (which is more than 99% of the time) the Warren-
Pierson sluice gate is held in the open position to take intercepted dry
weather flow.
276
-------
SUBURBAN FLOW
A factor which at this time limits additional in-system storage is the rather
high volume of stored flow which is received from suburban communities for
treatment at the Detroit Wastewater Plant. Five large detention basins in
suburban areas retain storm runoff for gradual release to the interceptor
over as much as a three day period. It appears that de-watering priorities and
schedules may be desirable or necessary in the future. This type of scheduling
would be a type of flood routing and has caused DMWD to consider other
possible locations for remotely operated sluice gates to implement such a
program. Figure 32 shows a possible gate location in the junction between a
trunk sewer and a relief line. Other ideas are also being investigated.
START-UP PROBLEMS
There have been numbers of unexpected problems in placing this monitoring
system in operation. Many difficulties were experienced in getting the leased
lines properly connected. The computer program required several adjustments
to produce usable data on the typewriters. Slight variations in voltage affected
the memory of the computer. During early stages, there were unexpected
down times due to failures of transistors. There has been a problem of cali-
brating each level sensor or rainfall sensor to get exact correspondence of
sewer level or rainfall data with the computer typed data. As these problems
are solved, the engineering staff is now getting data which are now much more
useful and dependable as a basis for developing parameters for use in future
operations.
CONSTRUCTION, CONTRACT, AND EQUIPMENT PROBLEMS
Miscellaneous problems have arisen during and after the construction phase of
the project, especially with the sensor installations. One problem that came
up three times involved the placing of pedestals in locations that made local
property owners unhappy. Although the pedestals are all on public property,
care should be taken to anticipate such situations as having a pedestal installed
too near a driveway or having it fall directly in front of a homeowner's front
door. The location of the manhole, of course, is the governing factor but the
pedestal can usually be shifted a few feet laterally to satisfy most citizen
complaints.
The original plan for sensor installation (See Figure 10) did not call for the
use of conduit but it was included at FWQA's request.
This has proven to be a wise decision since it allows for the replacement of
the 1/4" nylon tubing with a minimum of such problems as traffic disruption.
There have been a few locations where the conduit has risen out of its slot
in the pavement. To eliminate this problem in later installations, we have
277
-------
POSSIBLE LOCATION FOR REMOTELY
OPERATED SLUICE GATE
TYPICAL PORT HOLE CONNECTION
IN THE
DETROIT SEWER SYSTEM
FROM
PUBLIC SEWER INTO RELIEF SEWER.
FIGURE 32 - POSSIBLE REMOTE SLUICE GATE LOCATION
278
-------
been cutting the conduit and placing a sleeve approximately half way between
the manhole and the pedestal. This should allow the necessary movement
required to keep the conduit from buckling because of the traffic loads.
Traffic volumes should be considered when preparing a contract for installa-
tion of this type of equipment. In Detroit, as well as many other cities, a
traffic department will limit the time that certain streets or parts of streets
may be closed. This information should be made available to potential
bidders so that problems do not arise after contract execution has taken place.
The use of air rather than a bubbler gage in the Detroit level sensor has not
caused any unusual problems. Some temporary installations have been operating
nearly two years without any maintenance. T^sts were conducted during an
extremely cold period of December 1968 to see if any freezing problems might
arise. The float controlled gate at one regulator was manually closed causing
sewage to rise in the line and actuate the sensor at temperatures as low as
- 6°F with no adverse affects. Blockage from oil and debris in these combined
lines has not occurred. It is envisioned that an annual preventive maintenance
program will be set up and each fall each of the air lines will be blown down
with dry air. The valving set-up inside of each pedestal cabinet (See Figure
12) has been so designed to allow such an operation.
It has been found that once the 1/4" nylon tubing has been cut that an
effective splice cannot be made. One tube was cut with a pavement breaker
and all attempts at splicing have failed and an air leak continued to occur.
In the future when a break occurs the complete piece of tubing from the level
cell to the valve inside of the pedestal cabinet will be replaced. We at DMWD
feel that the problems arising from use of the low maintenance air type level
sensor are far out weighed by the benefits of the lower capital and operating
costs.
279
-------
SECTION IV
POST CONSTRUCTION EVALUATION PLAN (1970)
1. Complete computer programming of mathematical models of each outfall
so that in conjunction with pump station records the volume of overflows
may be calculated.
2. Correlate volume of overflows with rainfall data and develop hydrographs.
3. Allow and record overflows by using the "Monitoring and Remote Control"
system so tha t comparisons may be made and improvements documented.
4. Complete calculation and tabulation of all available storage volumes that
may be used during times of overflows.
5. Collection and analysis of additional storm and river samples.
6. Evaluation by weight of all types of pollution from each overflow point to
provide data for a study on regulator float settings.
7. Storm flow routing studies to allow for maximum benefit from monitoring
data and to pinpoint locations for future flow controllers.
8. Cost - Benefit Study.
9. Publication of Final Report.
281
-------
SECTION V
FUTURE OBJECTIVES (1971-75)
1. Further storm routing studies with emphasis on suburban flow entering
the system.
2. Development of new design criteria to aid in future expansion and
improvement to the system.
3. Study the possibilities of off-line storage operated in conjunction with
the monitoring program.
4. Study needs for and usefulness of supplemental computer related
equipment for control center (i.e. lighted panels, graphic printouts,
tapes, cards, self instrumentation, water quality inputs, etc.).
282
-------
SECTION VI
ACKNOWLEDGEMENT
F.W.Q.A. RESEARCH AND DEVELOPMENT PROJECT 11020 FAX
DETROIT - SEWER MONITORING AND REMOTE CONTROL
by
DETROIT METRO WATER DEPARTMENT
BOARD OF WATER COMMISSIONERS
JohnH. McCarthy, President
Charles H. Beaubien
Oscar A. Wagner
John D. McEwen
Henry R. Kozak
William Haxton
George J. Fulkerson
David Boston, Secretary
Gerald J. Remus, General Manager and Chief Engineer
ENGINEERING DIVISION
H. Werner - Assistant Chief Engineer
DESIGN
E. Cedroni
D. Suhre
J. Brown
F. Daskus
I. Schuraytz
C. Chapin
A. Davanzo
C. Schultz
R. Hagan
C. Barksdale
Head Engineer - General
Head Engineer - Wastewater
Acting Sanitary Engineer
Electrical Engineer
Mechanical Engineer
Sr. Associate Electrical Engineer
Associate Civil Engineer
FIELD
Field Engineer
Sr. Associate Civil Engineer
Associate Civil Engineer
283
-------
ACKNOWLEDGEMENT (CONTINUED)
OPERATIONS DIVISION
G. Dehem - Superintendent of Operations
W. Herrscher - Superintendent of Maintenance
A. Shannon - Chief of Water & Sewage Treatment
W. Callfas - Chief Water System Supervisor
J. Urban - Chief Engr. - Wastewater Plant
T. Standen - Supervisor of Mech. Maintenance
E. Fisher - Superintendent of Building Maintenance
E. Kline - Regulator Foreman
REPORT - DELINATION AND PRODUCTION
S. Beer C. Porter
Q. Washington E. Tulecki
We wish to acknowledge at this time that the development
of the Detroit system of Monitoring and Remote Control
was a "Team Project", rather than an individual brain
child. It was a team project in the finest sense of word
with the engineers, the operating personnel, the field
crews, the contractors forces, and the governmental
representatives all working together towards developing
an operating system. It has been a real pleasure to have
worked on such a team.
284
-------
APPENDIX A
285
-------
TABLE I-A
Average of Daily Grab Samples - 1968
Sewer Location
Pembroke
Frisbee E.S.
Frisbee W.S.
7 Mile E.S.
7 Mile W.S.
McNichols
Puritan E.S.
Puritan W.S.
Fenkell-Lyndon
Schoolcraft
Glendale
Plymouth
W. Chicago
Joy Road
Tireman
Hubbell-Southfield
Dearborn (Miller Rd.)
Baby Creek
Flora
Carbon
Pulaski
Dearborn Avenue
Schroeder
Dragoon
Campbell
Morrell
Ferdinand
Summitt
Scotten
Susp. Sol.
mg/1
195
194
192
532
790
180
332
335
423
180
482
592
1350
915
387
78
270
502
238
452
817
733
223
702
185
166
146
327
195
BOD
mg/1
111
90
148
458
267
158
181
234
184
192
113
298
197
202
149
43
144
227
162
109
181
222
97
203
107
125
111
183
95
Tot.P
mg/1
14.8
10.2
16.1
15.0
16.8
11.2
18.2
16.6
15.4
16.3
11.4
16.3
15.9
16.4
15.3
3.1
7.4
7.9
8.3
11.3
10.4
10.6
10.5
4.3
8.0
4.3
8.8
4.4
4.7
Phenols
mg/1
78
79
104
177
151
117
163
144
137
214
81
89
89
111
195
75
9700
2775
235
200
276
129
193
236
348
109
144
238
145
Oil & Grease
mg/1
34
32
70
75
83
95
58
86
49
48
67
230
100
100
26
22
55
2775
1395
62
140
77
116
20
122
65
84
82
443
286
-------
TABLE I-B
Sewer Location
Me Kins try
Swain
W. Gd. Blvd.
24th
21st
18th
12th
llth
3rd
First-Hamilton
Woodward
Brush -Bates
St. Antoine
Hastings
Rivard
Riopelle
Orleans
St. Aubin
Dubois
Chene
Adair
Leib
Mt. Elliott
Helen
Iroquois
McClellan
Conner
Ashland
Manistique
Fox Creek
Susp. Sol.
mg/1
203
69
117
149
498
648
387
92
239
140
155
342
53
180
342
142
1005
335
234
336
333
165
232
209
182
220
348
327
384
411
BOD
mg/1
92
21
88
217
270
390
207
116
174
186
38
221
120
90
201
68
723
299
305
233
233
109
208
170
108
148
84
156
146
204
Tot.P
mg/1
5.4
4.7
5.1
6.9
7.5
7.0
4.4
5.9
4.9
2.7
2.9
3.6
3.1
7.1
5.4
4.1
12.7
8.6
5.9
8.8
8.0
5.8
6.6
9.5
6.9
6.3
2.7
6.1
8.8
6.7
Phenols
mg/1
183
227
60
78
113
125
98
58
111
39
110
136
81
147
115
98
87
76
220
185
223
190
166
164
156
169
278
220
613
232
Oil & Grease
mg/1
177
11
25
104
858
99
116
14
163
31
38
84
23
52
39
36
301
127
66
408
60
25
71
45
34
51
123
40
52
88
287
-------
TABLE II-A
Average of Daily Grab Samples - 1969
Sewer Location
Pembroke
Frisbee E.S.
Frisbee W.S.
7 Mile E.S.
7 Mile W.S.
McNichols
Puritan E.S.
Puritan W.S.
Fenkell-Lyndon
Schoolcraft
Glendale
Plymouth
W. Chicago
Joy Road
Tireman
Hubbell-Southfield
Dearborn (Miller Rd.)
Baby Creek
Flora
Carbon
Pulaski
Dearborn Avenue
Schroeder
Dragoon
Campbell
Morrell
Ferdinand
Summitt
Scotten
Susp. Sol.
mg/1
149
105
117
172
70
115
85
253
411
302
399
200
163
147
170
78
402
446
294
309
453
115
239
625
205
197
213
163
204
BOD
mg/1
198
192
120
80
211
98
110
99
134
104
64
260
111
107
122
43
166
109
52
110
528
230
251
246
151
154
259
205
29
Tot.P
mg/1
13.3
12.9
9.6
11.4
11.4
6.8
11.5
10.6
13.6
15.0
12.5
17.3
9.0
13.5
15.4
3.1
8.3
7.6
6.8
8.5
7.3
9.3
7.5
8.0
7.8
5.9
8.2
3.1
8.8
Phenols
mg/1
130
222
180
212
326
163
212
218
239
286
159
247
239
148
149
75
1250
963
257
214
99
249
269
142
165
181
109
152
125
Oil & Grease
mg/1
57
53
29
14
60
24
19
19
31
26
28
42
25
24
19
19
64
121
182
34
689
41
81
680
87
74
550
89
29
288
-------
TABLE II-B
Sewer L ocation
McKinstry
Swain
W. Gd. Blvd.
24th
21st
18th
12th
llth
3rd
First -Hamilton
Woodward
Brush -Bates
St. Antoine
Hastihgs
Rivard
Riopelle
Orleans
St. Aubin
Dubois
Chene
Adair
Leib
Mt. Elliott
Helen
Iroquois
McClellan
Conner
Ashland
Manistique
Fox Creek
Susp. Sol.
mg/1
471
189
210
169
271
762
80
227
422
184
413
225
119
218
142
224
1005
729
267
338
460
148
229
268
240
268
248
257
101
228
BOD
mg/1
213
84
128
86
210
328
24
139
152
76
103
206
49
163
124
169
730
424
350
233
226
109
157
1-57
199
198
84
195
111
146
Tot.P
mg/1
6.5
3.2
6.4
4.8
5.0
6.1
2.0
8.5
4.3
3.7
4.6
3.1
3.5
5.4
5.2
8.2
11.9
10.5
6.7
8.9
7.0
5.8
7.6
11.5
8.1
9.1
3.7
5.8
4.0
4.8
Phenols
mg/1
199
329
191
179
131
188
81
49
107
18
122
115
73
206
120
243
70
112
265
185
236
173
179
105
96
95
322
146
130
228
Oil & Grease
mg/1
188
23
44
91
162
132
13
38
157
45
65
33
14
57
21
133
240
73
81
409
91
25
44
51
55
35
43
27
22
26
289
-------
rCAMJ*y
I I ELLIOTT _HELEN_
"ir-
-^ m •
L j /-o PS.
-1 _____ lL _______ ' /— -
EN- ITLYNDON "1
OUTFALLS ORLEANS TO FOX CREEK
CABA- GRJS_- WOOD- BATES
r ~ 7~ ~] CJER EJRSI _. PwoLbn WARP^ r
:,f lit ,J!-i
W. GRAND __2f'_
SWAIN _ T ^LVt). - j&L
^BPnr
__ui!._Jr"^LJt
I Li._SJiB^
. - - ma
—JL
_ _JL_ _J| ____ I _____ I
-
L_ -
OUTFALLS SWAIN TO RIOPELLE
OAKWQOD DE.ARBORN SOLVAY, 5CHRO -
CARBON F PS. RJLASKI ~ |£fflX_.
-_-_j^^j JL. JL Ji ^L:
OUTFALLS MILLER TO SCQTTEN
COMBINED SEWER OUTFALLS
CITY OF DETROIT
FIGURE 33
-------
SECTION 7
STREAM POLLUTION & ABATEMENT
FROM COMBINED SEWERS
BUCYRUS, OHIO
BY
RICHARD F. NOLAND
DALE A. DECARLO
BURGESS AND NIPLE LIMITED
CONSULTING ENGINEERS
2015 W. FIFTH AVENUE
COLUMBUS, OHIO 43212
291
-------
ABSTRACT
This paper contains results taken from a detailed engineering investigation
and comprehensive technical study to evaluate the pollutional effects
from combined sewer overflows on the Sandusky River at Bucyrus, Ohio which
evaluated the benefits, economics and feasibility of alternate plans
for pollution abatement from the combined sewer overflows. The City of
Bucyrus is located near the upper end of the Sandusky River Basin which
is tributary to Lake Erie. Bucyrus has an incorporated area of about
2,340 acres, a population of 13*000, and a combined sewer system with an
average dry weather wastewater flow of 2.2 million gallons per day. A
year long detailed sampling and laboratory analysis program was con-
ducted on the combined sewer overflows in which the overflows were
measured and sampled at 3 locations comprising (&% of the City's sewered
area and the river flow was measured and sampled above and below
Bucyrus.
The results of the study show that any 20 minute rainfall greater than
0.05 of an inch will produce an overflow. The combined sewers will over-
flow about 73 times each year discharging an estimated annual volume of
350 million gallons containing 350,000 pounds of BOD and 1,4-00,000
pounds of suspended solids. The combined sewer overflows had an average
BOD of 120 mg/1, suspended solids of 4?0 rag/1, total coliforms of
11,000,000 per 100 ml and fecal coliforms of 1,600,000 per 100 ml. The
BOD concentration of the Sandusky River, immediately downstream from
Bucyrus, varied from an average of 6 mg/1 during dry weather to a high
of 51 ng/1 during overflow discharges. The suspended solids varied from
an average of 4-9 «g/l during dry weather to a high of 960 mg/1 during
overflow discharges. The total coliforms varied from an average of
400,000 per 100 ml during dry weather to a high of 8,800,000 per 100 ml
during overflow discharges.
A method of controlling the pollution from combined sewer overflows is
presented along with the degree of protection, advantages, disadvantages
and estimate of cost. The method presented is an interceptor sewer and
lagoon system. The most economical method of providing a high degree of
protection to the Sandusky River is by collecting the combined sewer over-
flows with a large interceptor and using an aerated lagoon system to treat
the waste loads from the overflows.
The report from which this paper was prepared was submitted in fulfillment
of Contract 14-12-401 between the Federal Water Pollution Control Adminis-
tration and Burgess & Niple, Limited, Columbus, Ohio.
293
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STREAM POLLUTION AND ABATEMENT
FROM COMBINED SEWir.fi AND OVERFLOW
BUGYRUS, OHIO
Bucyrus, Ohio Is located nea.r the headwaters of the 1421 square mile drainage
area of the Sandusky River Basin in northern Ohio. The drainage area above the
City is 90 square miles and consists of mostly level, agricultural land. The
current estimated population of the City is 13,000 with an incorporated area of
about 2,3^0 acres. The topography of the City is generally flat to slightly
rolling. The study area is shown on Figures 1, 2 and 3« The mean a.nnual precipi-
tation is 36 inches.
The Sandusky River downstream from Bucyrus is a source of water supply for
the cities of Upper Sandusky, Tiffin and Fremont. The principal pollution
problems in the Sandusky River are sediment, oxygen consuming materials, bacteria,
phosphates and nitrates. The stream drains rich agricultural lands which con-
tribute significant amounts of sediment and nutrients. The area around Bucyrus
is intensely cultivated. At the present time all communities discharging sewage
effluent to the Sandusky River provide secondary treatment facilities.
Future water management plans for the principal cities in the watershed are
based on utilizing the natural flow in the River and upground storage reservoirs
as the major source of water for the area. Reduction in the pollution dis-
charging to the River thus becomes very important if the desired water quality
is to be achieved and maintained for the intended uses.
This is a study to determine the possibility of intercertion of all or part
of the combined sewer overflow for treatment prior to release to the stream$
also to determine the relationship of rainfall events to overflow events and the
volume of flow and waste load discharged to the Sandusky River. Weirs for
measuring overflows during rainfall were installed at the overflow points of
three selected sewer districts. Samples were collected during selected
295
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STUDY AREA
MILES
SCALE
0
10
20
1421
353
98O
LEGEND
Droinoge oreos enclosed by shoded
Drainage areas enclosed by unshaded
lines —-— —— (sq miles)
Drainage areas above points
indicated by arrows - sq. miles
Approximate low-water elevation
in feet above sea level
Figure No. I
SANDUSKY RIVER
Droinoge Area
296
-------
}0a
Figure No 2
GENERAL PLAN OF
coksaeo SEWER DISTRICTS
BUCTRUS.OHO
297
-------
Overflow 8 Weir Location
,Roin Gduge Locotion
r **• ..- /
PHYSICAL DATA
Sewered Drainage Area 452 Acres
Non-Sewered Drainage Area 162 Acres
Impervious Area 33.7 Acres
Average Slope 0.65 %
Population 4300
Figure No. 3
NO. 17 SEWER DISTRICT
Bucyrus, Ohio
CONTOUR INTERVAL 5 FEET
SCALE IN FEET
0 IOOO 20OO
t • I .... I
-------
overflow events to determine overflow characteristics and the effects on the
stream.
The dry weather wastewater flow in the combined sewer system is intercepted
at 24 points along the River and conveyed downstream in an interceptor sewer
to the wastewater treatment plant. The plant is conventional activated sludge
and discharges into the Sandusky River. Most of the sewers are (fit" minimum grade
due to the flat terrain.
A detailed study of the City and the sewer system was made and three
districts were selected for study. These were No. 8, with 179 acres, No.
17 with 452 acres, and No. 23 with 378 acres. No. 17 is shown in the
accompanying figures. These are the three largest drainage districts in
Bucyrus and represent 64% of the total sewer drainage area. A complete de-
tailed hydraulic analysis was made of the sewer system in these districts.
A rectangular Weir (See Figure 4) was built at each of the three overflow
points to measure overflow during rainfall. The weirs were constructed of
1" plywood which was bolted on to steel angles imbedded in concrete. The weirs
were sized to pass the maximum capacity of the trunk sewer at the overflow points.
Water level recorders were installed in instrument shelters behind the weirs.
All recorders were equipped with automatic starters which would start the clocks
at predetermined water levels. An automatic starter was devised for the samplers
that started the clocks when the water level reached a predetermined height behind
the weirs. Samplers could therefore be left unattended prior to and during an
overflow.
A continuous record of the flow in the Sandusky River, both above and below
Bucyrus, was obtained during the study period. This was accomplished by using
the records from ah existing recording gage operated by the U. S. Geological Survey
299
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NO. 8 OVERFLOW WEIR
NO. 17 OVERFLOW WEIR
Figure No. 4
300
-------
and a stream gaging station installed by us prior to the beginning of the study.
The combined sewer overflows and the River were sampled during many storms
throughout the study period to determine the quality of the overflow and the
pollution loads. Only the overflows at No. 8, }7, and 23 sewer districts were
sampled. From July, 1968 through January, 1969 samples were collected manually.
After February 1, 1969 automatic samplers were installed and supplemented by
manually sampling. Laboratory analyses were performed on all overflows and river
samples selected for 18 different physical and chemical tests.
Project personnel made 16 trips during wet weather to Bucyrus from July
1968 until September, 1969 to collect samples Of predicted overflows. There
were 10 days out of 16 that overflows actually occurred and were sampled. Grab
samples were collected manually during five overflow events that occurred prior
to February 8, 1969. Samples of the remaining 5 overflow events were collected
by automatic samplers and project personnel.
The relationship of rainfall and runoff was studied by the use of several
different methods. Hyetographs and Unit Hydrographs were developed for the
design storm. The graphs for No. 17 district are shown in Figure 5. A straight
line relationship was found between maximum rainfall intensity for a given duration
and peak overflow rate. The least amount of deviation was produced by a rainfall
of 20 minute duration.
Following is the mathematical formula for the relationship for No. 17 overflow:
Maximum Twenty Minute Rainfall versus Peak Overflow Rate
Q = Peak flow, cfs
I f Maximum average 20 minute rainfall intensity, In./Hr.
No. 17 Overflow
1) No Antecedent Rainfall
I ^0.39, Q - 110 (I - 0.18)
I >0.39, Same as with Antecedent Rainfall
2) Rainfall within 24 hours
Q = 60 (I - 0.03)
301
-------
K 4
CO
tn
z
Ld
H
g
Z
<
00
0
rO
=L
200
MU XIMUM
SEWER C
MITHOU1
I 2 3
TIME - HOURS
AFTER START OF RAINFALL
Figure No. 5
Rainfall and Overflow
Two Year, One Hour Storm
No. 17 Overflow
302
-------
The volumes of overflow were related to rainfall by means of the unit hydrograph.
Since the peaks of the unit hydrographs are directly proportional to their volume,
there was also a straightline relationship between the rainfall and overflow volumes.
This relationship is expressed as the following mathematical formula:
Twenty Minute Rainfall versus Overflow Volume.
0 = Overflow Volume, Depth on Sewer district in inches
P - Rainfall, inches
No. 17 Overflow
1) No Antecedent Rainfall
P£ 0.13, 0 = 0.51 (P - 0.06)
P 0.13, Same as with Antecedent Rainfall
2) Rainfall within 24 hours
0 = 0.28 (P - 0.01)
Part of the laboratory results of the overflow samples from the three selected
districts have been summarized and presented in Table 1. This table presents the
average, minimum, maximum and medium values of the chemical and bacteriological
characteristics of all the individual overflow samples collected during this
study^ Sewer District 8 had an average BOD Concentration of 170 milligrams per liter
which is considerably higher than the average BOD Concentration of Sewer
Districts $17 and 23, each of which had an average of 107 mg. and 108 mg. per
liter, respectively. The average suspended solids concentration of 480 mg. per
liter for the overflow samples is much higher than the average of 160 mg. per
liter for the dry weather samples.
The significant water quality characteristics of the overflow samples which
include BOD, suspended solids, total solids, and nitrogen series, total phosphates
and chlorides have been graphed in comparison to time after start of overflow and
are shown in Figures 6 to 12. These curves very clearly show the first flushing
effect of the storm water. A summary of the waste loads discharged into the
Sandusky River from each of the five overflows sampled and measured have been
calculated and summarized in Table 2. This Table shows that the August 9, 1969
overflow event (No. 5 in the table) discharged into the Sandusky River from just
303
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TABLE 1
SUMMARY OF LABORATORY ANALYSES
ON OVERFLOW SAMPLES
LOCATION
1 . Overflow No. 8
No. of analyses
Average
Minimum
Maximum
Med 1 an
2. Overflow No. 17
No. of analyses
Average
Minimum
Maximum
Median
3. Overflow No. 23
No. of analyses
Average
Minimum
Maximum
Median
BOO
mq/l
47
170
II
560
140
54
107
II
265
100
52
108
23
365
78
COD
mg/l
13
372
64
735
394
20
476
120
920
440
21
391
105
795
355
SUSPENDED
SOLIDS
mq/l
42
533
20
2440
360
44
430
90
990
400
32
477
120
1050
385
VOLATILE
SUSPENDED
SOLIDS
mg/l
13
182
70
440
180
24
238
80
570
160
20
228
70
640
200
TOTAL
SOLIDS
mq/l
40
1647
150
3755
1260
33
863
310
I960
780
25
916
370
1965
830
304
-------
••
CD
O
O
.
9 i Zl
O to
O o
?:•
; -....
HOURS AFTER START OF OVERFLOW
-------
2500
w
e
-r W
O — Tl
5! ua
=3 w
o *
9 |
A
o" =t
* o
d
2000
1500
Y) NOV 15 68
First Flow
NOV. 15'68
Second Flow
3 FEB. 8'69
MAR 24'69
MAY 7'69
JUN.13'69
?) AUG.9'69
HOURS AFTER START OF OVERFLOW
-------
us
• •
»i
! 2
HOURS AFTER START OF OVERFLOW
-------
:
00
P 5' 31
O (O
-o =r c
HOURS AFTER START OF OVERFLOW
-------
UJ
c
vo
i
9 5* 21
CD
-
« .
o
o>
o
- AMMONIA NITROGEN
ORGANIC NITROGEN
MAR. 24 69
First Flow
MAR. 24 69
Second Flow
JUN. 13'69
HOURS AFTER START OF OVERFLOW
-------
• .
H
• '
O O
< U>
-------
500
400
<
it
o 300
• •
O
"— O
O.
A
-------
TABLE 2
SUMMARY OF WASTE LOADS FOR EACH OVERFLOW EVENT
I.
2.
3.
4.
5.
Average
mq/l
120
5!
86
146
161
104
1 18
172
1 16
41
3!
36
177
112
112
BOD
Total
Ibs.
98
118
190
406
201
415
149
765
50
194
216
460
331
312
420
1063
600
1040
670
lbs/100/
ac.
55
26
50
112
92
40
28
43
57
185
69
II 1
336
230
178
Average
ma/I
570
615
670
675
670
505
430
454
660
375
413
652
_
306
-
SUSPENDED
SOLIDS
Total
Ibs.
464
1416
1480
3360
931
1539
725
3195
184
514
1234
1932
3100
4200
7700
14778
.
2850
-
Ibs/IOO/
ac.
260
313
390
520
340
192
103
114
325
1700
900
2050
.
630
-
2310
312
-------
three districts, 2300# of BOD in approximately 2 hours, this is more BOO than
was received at the wastewater treatment plant in 24 hours of dry weather flow.
Extrapolating the 2300# of BOD to include all 24 sewer districts, gives the total
of 3500# of BOD discharged to the river.
In studying the river response to rainfall, an urban runoff hydrograph was
developed which showed the distinct effect of the runoff from the urban area on the
river. The significant runoff reaches the downstream gage approximately one hour
after the start of the rain. The river reaches a peak flow two hours later, as
shown in Figure 13. In 7 hours the river returns to its prestorm level and remains
until the runoff from the upstream drainage area arrives. The time of arrival
depends entirely on the velocity in the River. The lag time of the peak flow follow-
ing the end of the rains, varies from 40 hours to 17 hours for river flows of 4 to 300
C.F.S. at the upstream gage.
The wastewater loads, discharged from combined sewer overflows, depends on a
number of factors, including duration and intensity of rain fall, volume of runoff,
number of days between overflow events, efficiency of street cleaning operations
and design characteristics of the sewer system. The relationship between BOD and
suspended solids and load discharged per 100 acres is shown in Figures 14 and 15.
Generally the longer the period of time between overflows, the larger the waste load
for a particular overflow volume.
Some of the conclusions from this study were:
1. Any 20 minute rainfall greater than five-hundreds of an inch, will
produce an overflow of wastewater into the Sandusky River at Bucyrus. A rainfall
of this intensity and duration, or greater, will occur on the average of once every
five days.
2. A typical summer thunder shower occurred on June 13, 1969 and produced
1.1 inches of rain with a duration of 78 minutes and an average intensity of 84
hundreds of an inch per hour. The runoff from this storm discharged into the
Sandusky River through the combined sewer overflows, 5.2 million gallons of combined
sewer wastewater; 1580# of BOD and 23,0005? of suspended solids.
3. A storm on August 9, 1969 which produced .5 inches of rain in about 75
313
-------
t,
a.
u
a
:
2345
TIME-HOURS
(PERCENT BASED ON 30 MINUTE TIME INTERVALS )
Figure No. 13
Distribution Graph for Urban Runoff
Downstream Gauge
314
-------
H
n
o -n
If
o
CD 1_
O -P>
O
Q
QT-
K
U
u
O
ot
Ul
Q
2
z
o:
,->
,,:
r:
-
G
150
200
250
300
BOD - LBS. PER 100 ACRES
-------
g_
? £
c
Vt
3 •__
S" 01
o.
ex
0)
SUSPENDED SOLIDS - 100 LBS. PER 100 ACRES
-------
minutes, increased the BOD concentration of the Sandusky River downstream
from Bucyrus from 11 mg per liter at river flow of 9 c.f.s. to 51 mg
per liter at a river flow of 130 c.f.s.
4. The combined sewers will overflow about 73 times each year, dis-
charging an estimated total annual volume of 350,000,000 gallons, or about
1,000,000 gallons per day.
5. The combined sewer overflows have an average BOD of 120 mg per
liter, suspended solids of 470 mg per liter. Total coliforms of 11 million
per 100 ml and fecal coliforms of 1.6 million per 100 ml.
6. The combined sewer overflows at Bucyrus discharge an estimated
350,000 pounds of BOD and 1,400,000 pounds of suspended solids annually into
the Sandusky River.
7. The BOD concentration of the Sandusky River, immediately downstream
from Bucyrus, varied from an average of 6 mg/1 during dry weather to a high
of 51 mg/1 during overflow discharges. The suspended solids varied from an
average of 49 mg/1 during dry weather to a high of 960 mg/1 during overflow
discharges. The total coliforms (by membrane filter technique) varied from an
average of 400,000 per 100 ml during dry weather to a high of 8,800,000 per
100 ml during overflow discharges.
8. The estimated yearly discharge of 15,700 pounds of nitrate nitrogen
(12,200 pounds from overflows and 3,500 pounds from wastewater plant) from
Bucyrus is rather insignificant when compared to the 136,000 pounds and 192,000
pounds found in the river coming from the upper drainage basis on April 19, 1969
and May 19, 1969, respectively.
9. The nitrate nitrogen concentration of the Sandusky River, upstream
from Bucyrus, varied from a low of 0.4 mg/1 as NO,,to a high of ?2.mg/l. il.t
317
-------
hiph concentrations occurred during high river flows in the spring of the
year. The estimated nitrate nitrogen discharged from the upstream drainage
area is 2,300,000 pounds annually.
10. The combined sewer overflows discharge about 30,000 pounds of
phosphates (PO 4) into the river annually. The wastewater treatment
pl,?.nt discharges about 160,000 pounds of PO, eatth year. An estimated
110,000 pounds of PO, per year came from the upstream drainage area.
From this investigation and study the design storms and waste loads have
been determined for Bucyrus and are shown in Table 3. An interceptor
Sawer and Lagoon System is proposed. The benefits from controlling pollution
due to combined sewer overflows by the use of an "interceptor and Lagoon
System" are many.
(a) Reduces pollution of the river both within the city of Bucyrus
and downstream.
(b) Stream protection surpasses that to be achieved by combined sewer
separation in that all runoff up to the design storm will be inter-
cepted and treated.
(c) Increases the value of the stream to the public in the City
and downstream from the City.
(d) Reduces a health hazard within and below the City.
(e) A clean stream provides the possibility through use of landscape
architecture to beautify the stream, enhance its esthetic value and
make it a real asset to the community.
The total cost of the proposed Interceptor Sewer and Lagoon System is about
$5,200,000 compared to $9,000,000 for sewer separation.
318
-------
TABLE 3
DESIGN STORMS AND WASTE LOADS
Overflow
Total Volume BOD Suspended Solids
Rainfall Million Ibs. Ibs.
Design Storms Inches GaI Ions Average Maximum Average Maximum
2-yr., I hr. 1.23 13.4 14,000 18,000 53,500 90,000
l-yr., 24 hr. 2.3 26 14,000 17,100 68,000 76,000
319
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Proposed Gravity Interceptor Sewer
isting Interceptor Sewer
New Pump Static
(Overflows Only)
LAGOON
o o
SYSTEM
Present Waste Treatment
Plant
Figure No. 16
ALTERNATE SOLUTION
INTERCEPTOR a LAGOON SYSTEM
320
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SECTION 8
ORGANIZING FOR SOIL EROSION
AND SEDIMENT CONTROL
IN OUR NATION'S URBAN AREAS
by
Mel D. Powell, LL.B., Ph.D.
Director of Contract Research
National Association of Counties
Research Foundation
for the
STORM AND COMBINED SEWER SEMINAR
United States Department of the Interior
Federal Water Quality Administration
Chicago, Illinois
June 22-23, 1970
321
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America has reached a point where it can no longer ignore the
very real environmental dangers that are created as by-products of
technological growth. In few places are these dangers to the environ-
ment more real than in the watersheds and river basins within which
the nation's massive urban and suburban growth is taking place.
In the nation's suburban areas, extensive alternation of the
landscape and intensive use of the land have resulted in serious im-
balance between soil and water. As a result, erosion and sediment,
traditionally considered as exclusively agricultural problems, have
become serious problems in urban and suburban America.
Despite the fact that suburban erosion and sediment cause extensive
pollution of water bodies, cost millions annually in damages to homes,
roads and recreational areas and in some areas even threaten domestic
water supplies, very few localities in the nation have organized and
implemented erosion and sediment control measures.
As a means of encouraging positive action at the local level, the
Federal Water Quality Administration awarded the National Association
of Counties Research Foundation a grant to investigate the problem of
sedimentation and to develop a guidebook for local policy making offi-
cials. The guidebook published in March 1970 describes the administrative,
legal and organizational tools available and necessary to successful soil
erosion and sediment control programs. The concepts and strategies rec-
ommended are based on actual programs in effect in various localities.
Our findings, therefore, are based on numerous on-site examinations and
interviews with state, county and municipal officials, soil and water
conservation people, as well as homebuilders and roadbuilders.
The purpose of the guidebook is to assist local policy-making
officials in making sound resource management decisions by providing
comprehensive information on the various aspects of control programs
in the belief that local officials share much of the responsibility
for proper resource management.
323
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Erosion and Sediment are Local Problems
Erosion and sediment inflict heavy damages upon local governments,
businesses and citizens. The financial costs to local communities caused
by these problems has been staggering in many areas. These costs are
born by the local communities either through higher taxes or direct ex-
penditures to repair damage to private property. Many of these costs are
unnecessary in that through proper planning and organization, much of the
damage can be prevented.
I think we can agree that citizens elect local government officials
to take the necessary steps to prevent damages to their property. Local
officials, therefore, share much of the responsibility for preventing
such damage.
Increasingly, local officials are being reminded that they must assume
their share of the responsibility for managing the natural resources of
their community. The federal and state governments can and do offer guide-
lines and assistance to local areas. However, the bulk of the responsibility
for proper management of the environment must come from local officials, as
well as concerned citizens, professional conservationists, businesses and
industries. The role of local officials is important in this connection
because they are primarily responsible for making the basic policy decisions
with regard to how local resources are allocated and used. As the demand
of local resources, such as land, increases, the demand for wise decisions
with regard to their use will also increase.
Organizing for Control
There are two important organizational features of local control
programs which we might note. First, organizational approaches may vary
considerably from place to place in accordance with local variations in
physical, historical, legal, political, financial and demographic charac-
teristics. To be effective, a control program will have to be organized
on the basis of these local conditions. The first condition that should
be considered is the nature and extent of the local problem. This may
mean that research will be needed to determine where and how much soil
is being eroded, what the effects of sediment are, and what measures can
be taken.
Second, control programs should be organized in such a way as to in-
clude all interested and relevant groups and agencies. There are several
reasons for this, the most important being that this approach encourages
cooperation. The experience of several on-going control programs suggests
that the importance of cooperation cannot be overemphasized. It has been
a key factor in the success of many county efforts. An example is avail-
able in Montgomery County, Maryland, which organized and implemented a
pioneer sediment control program in 1965. Their program, which is now
being used as a model by other counties, made cooperation among local
325
-------
agencies the key factor.
Local leaders emphasize that the program would be ineffective in
its present form without a high level of involvement and cooperation by
numerous local, state and federal agencies and groups. Local groups
involved in this cooperative program include the local homebuilding
association, the county soil and water conservation district, citizens'
groups, conservation societies, a water management agency, a planning
commission and a department of public works, among others.
The Multi-disciplined Approach
Because so many groups and individuals are intimately associated
with the problems, it may be appropriate to organize a control program on
a basis which will encourage the participation of all groups and agencies
which have an interest in, or which will be affected by, the control pro-
gram once it becomes operational. There are several reasons for this
which have been substantiated by the experiences of several communities.
First, by involving as many groups as possible, the chances are lessened
that the program will divide those who contribute to the erosion and sedi-
ment problem and those who are attempting to correct it. In most cases
these positions are not clear, and in many cases they are interchangeable;
that is, those who create sediment, such as homebuilders, may also be
attempting to control sediment, and those who are responsible for con-
trolling sediment, such as local governments, are also causing it. Thus,
a value of the task force approach is that it helps to promote a unified
and realistic recognition of the nature of the erosion and sediment problem.
Another reason for obtaining involvement of diverse groups in the
control program is that the manpower resources available to the program
can be increased by utilizing personnel from various participating groups.
To be effective, a control program requires professionally trained per-
sonnel. The task force approach makes available personnel trained in
various disciplines when they are needed. For example, soil scientists
and other technically trained personnel are often available on a coopera-
tive basis from local soil conservation districts; hydrology experts are
available from state departments of water resources or their equivalents;
departments of public works are normally staffed with professional engineers,
as are the homebuilding organizations; and planning agencies can contri-
bute professional planners from their staffs. Citizens' groups are also
sources of manpower and can carry out important responsibilities in
connection with public education programs.
Another reason for encouraging involvement is to reduce resistance.
Where several groups work together, the resulting control program is likely
to be more effective.
326
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The Role of Local Government
Establishing control over erosion and sediment involves making
decisions with regard to how local resources are to be planned, allo-
cated and used. Specifically, a control program will frequently affect
land use policy, the quality of water resources, and will require the
use of local funds to support the control effort.
A control program therefore represents a form of resource management
which must be regarded as a responsibility of local government officials.
But the responsibility of local officials is to develop the organizational
and procedural forms for gaining control over erosion and sediment. The
following four (4) steps suggest some of the important aspects of organ-
izing a control program:
(1) formal recognition by local elected officials of the need for
erosion and sediment control;
(2) formulation of administrative and legal controls;
(3) assignment of specific responsibilities to local agencies;
(4) provisions for on-site inspection of erosion and sediment sources,
including procedures for evaluating the effectiveness of the control
program and for maintenance of control devices.
Looking at step one closely, formal recognition of the need for
erosion and sediment control by local elected officials serves several
purposes, each of which is important to effective control. First,
formal recognition represents an official statement that erosion and
sediment problems do exist. In order for local agencies to exercise
effective control, they will need the support of local officials who have
the responsibility for making policy decisions related to land-use activ-
ities. Second, a formal recognition and acknowledgement of a need for
control by local officials serves the purpose of establishing the position
of the "public interest" in favor of control. This, in effect, forms the
justification for specific follow-up legislation. A third purpose served
by a formal recognition of control is related to timing. Once erosion
occurs, and sediment is yielded, the damage is done. It is not possible
to halt damage at this point, and costly repairs usually result, fre-
quently at public expense. A formal recognition of control serves to
notify the general public that, henceforth, efforts will be made to
control erosion and sediment.
Step two—It is not usually possible to develop a control program
within a short period of time. Hastily developed provisions may be inef-
fective if they are either too demanding or not demanding enough. One
characteristic of successful control programs now in operation is that
the legal provisions and administrative procedures, which constitute the
backbone of control programs, have not been abruptly imposed but instead
have been developed to their present form over a long period of time.
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Compliance with control legislation will be difficult to enforce
unless the community is aware of and understands the need for regulation.
A period of time will be needed for the members of the community to be-
come acquainted with the control program and how it affects them. This
time period can also be used to make adjustments in the program to meet
unanticipated problems. Accordingly, it may prove helpful to launch the
program on a voluntary basis for a period of time in order that various
parties can make appropriate adjustments. Legal provisions and admin-
istrative procedures can then be made firm at a later date when initial
difficulties have been worked out. A balanced and flexible approach to
this aspect of the program's development process may be important to
overall success.
For many types of suburban erosion, controls may be implemented by
placing stipulations within subdivision regulations. These stipulations
set in motion a series of administrative and operational activities de-
signed to control sediment yields by limiting erosion from subdivision
developments and other construction activities. Some local governments
have curtailed erosion and sediment from housing developments by stipu-
lating within their subdivision regulations that homebuilders must include
within their preliminary subdivision plans adequate provisions for con-
trol. The preliminary plans are reviewed by appropriate local agencies
for approval and recommendation. In this way, protection is built into
the subdivision planning process and protection is provided, in most
cases, before construction begins.
It may be necessary to make use of grading regulations in cases where
grading of land will contribute to the problem. Grading permits may be
used to regulate the timing of development, the extent to which grading
operations may disturb the soil, and may also regulate sloping operations
and vegetation removal. Normally, the issuance of grading permits is a
function of a department of public works. Specific control specifications
are usually technical in nature and generally are of interest only to
those parties having a direct interest in controlling sediment. These
detailed standards can be printed and made easily available to builders,
local agencies and other interested parties. These standards, however,
should be supported by general standards which are part of local legal
codes.
Other methods that local governments can use to control erosion and
sediment include land-use planning policies and certain types of zoning.
Step 3—Once appropriate legislation is incorporated into legal codes,
it will be necessary to implement the regulations by assigning adminis-
trative responsibilities to appropriate local agencies.
Under the task force approach, responsibility for administering
controls is shared by several local agencies. Specific responsibilities
may be assigned according to the capabilities of each respective agency.
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A frequently used approach is to require that the local planning commission
review the subdivision plans to evaluate the probable effectiveness of
control measures proposed by the builder. Frequently, copies of the sub-
division plans are made available to the department of public works where
they are reviewed for erosion control. In some control programs, sub-
division plans are forwarded to local soil conservation districts where
soils experts and other professionals review proposed erosion control
measures and make recommendations for improvement when necessary. Other
local agencies, such as sewer and water agencies, are also included.
There are sources of erosion and sediment other than those which are
caused by private developers. Construction of public facilities, such
as highways, sewers, and public buildings are major causes of suburban
soil erosion. To be effective, an erosion and sediment program will
need to control these causes as well as others.
Highway erosion is widespread in the United States, and various
technical means have been developed to help control this costly problem.
In many instances highway departments can receive technical assistance
from local conservation agencies. This is sometimes arranged by inter-
governmental agreements between appropriate local agencies. Intergovern-
mental agreements can also be used in efforts to control erosion from
construction of public facilities, such as schools and other public
buildings, and sewers, and they can also be employed to coordinate munici-
pal and county control efforts.
In order to achieve comprehensive control, sediment from public as
well as private causes will need to be curtailed. It is important that
public agencies take the leadership in controlling sediment caused by
their own construction activities.
Step 4—To be effective, a control program will need to provide for
on-site inspection of construction activities. In most cases, this function
is carried out by a local agency, such as the public works department. The
inspection function serves the purpose of identifying problems, examining
control devices, and evaluating the effectiveness of various control tech-
niques. Evaluation of the program's effectiveness is necessary in order
that modifications in the program can be made to improve control.
Leadership
If a community chooses to use the task force as an organizational
approach, it is important that the task force group select one organi-
zation or individual to provide leadership. This step is necessary in
order to provide the coordination needed in the program, to schedule and
conduct meetings, to help orchestrate various activities, and to ensure
continuity in the overall program. One important function of the leader-
ship may be to ensure that an objective evaluation of the program is
conducted periodically. The leadership should see to it that the program
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proceeds on a continuous basis and that guidelines and needs are provided
for future task force group activities.
I have attempted to describe some considerations involved in organ-
izing a control program and I have briefly discussed some specific
organizational structures that may be suitable, with modifications, to
a variety of local situations.
The multi-disciplined approach to organization outlined represents
only one pattern that may be employed in efforts to control sediment.
However, the experiences of several communities using this approach indi-
cates that it is an attractive organizational format which helps to promote
full community involvement and cooperation so necessary for effective
control.
Let me reemphasize that erosion and sediment problems in suburban
and developing areas can be brought under control, in most instances.
What is most needed at this time is an effort toward building a wide-
spread understanding of the problem at the community level, and the
desire and energy to construct a workable community-wide system to ad-
minister available human resources.
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Community Action Guidebook
for Soil Erosion and Sediment Control
We have divided the guidebook into ten chapters. The first nine
chapters address a specific aspect of control. We have attempted to
refine, for local officials, their role in relation to erosion and
sediment control specifically, and their role with regard to overall
resource management generally. Following is a complete copy of
Chapter Ten, which is, in effect, an action plan presented in out-
line format and incorporating the key elements of the previous nine
chapters.
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chapter ten
Action Guide for
Erosion and Sediment Control
LOCAL GOVERNMENT'S ROLE
Environmental quality has deteriorated so seriously that
local governments now have only two choices: to conduct
effective environmental control programs at the local level,
or to pass local responsibility and authority for control
programs to state and federal levels by default. Local
officials should provide leadership to their departments and
to their communities in maintaining a clean environment
and managing local resources.
Very few local governments have accepted responsibility
for developing sedimentation control programs, and
consequently, experience with erosion and sediment
control in urban areas has not been extensive. However,
citizens are beginning to demand that community
resources, including soil and water, be properly managed.
Since the county is an areawide unit of government, serving
urban, suburban, and rural citizens, county officials are in
an excellent position to respond to the public's demand by
establishing effective areawide sedimentation control
programs.
The guidebook is based on 10 months of research,
including on-site visits to local sedimentation control
programs across the nation, to state level control
operations, and to various federal agencies. In addition, the
guidebook is based on the recommendation made by 200
experts in water quality and soil conservation at the
National Conference on Sediment Control, held in
Washington, D.C., September, 1969.
This chapter represents a synthesis of sedimentation
control concepts, principles, and techniques, which can be
converted into general action plans by local, state and
federal levels of government.
WHAT SHOULD LOCAL GOVERNMENT DO?
Local elected officials can establish a sedimentation
control program by taking the following basic sieps:
I. Appoint a Task Force.
Local elected officials should begin their sediment
control program by appointing a sediment control task
force to develop recommendations for the program.
In most existing urban programs, this task force
was made up of individuals from the planning
commissions, water and sewer agencies, home builders
associations, soil conservation districts, professional
engineers associations, contractors groups, U.S. Soil
Conservation Service, State Department of Water
Resources, and others concerned with the problem.
II. Establish Task Force Objectives. The Task Force
should fulfill the following basic objectives:
(1) Determine through physical and demographical
studies the nature and extent of the local
sedimentation problems.
(2) Determine existing erosion and sediment control
practices exercised by local public agencies, and
private developers contractors.
(3) Determine what state and local laws exist
regarding water pollution and land use.
(4) Decide what should be done by local
governments, areawide government, and private
industry, and how they can best cooperate in
carrying out the program.
(5) Insure that development and construction
activities do not result in environmental
pollution.
III. How to Proceed
(1) See that the program is premised on providing
control for the totality for every watershed
lying, whole or in part, within local jurisdictions.
Frequently, the county is the areawide unit
which meets this requirement. Where a single
county is not large enough to solve the areawide
sediment control problem, the multi-county
approach may be best. In some large
metropolitan areas where erosion, and sediment
problems cross jurisdictional boundaries,
councils of government may offer an excellent
vehicle to stimulate local officials to think, plan.
and act in broad terms of mutual problem areas
and to encourage jurisdictions to effect a
mutually complementary system for
sedimentation control.
Sometimes special purpose governments
may be used because of their expertise in erosion
control. If a special purpose government must be
used, it is better to work through existing special
purpose governments (where possible) rather
than to create new ones.
Jurisdictions can cooperate through various
techniques: by jointly performing some or all
aspects of the control program; by contracting
between cities and counties; and by transferring
responsibility for a function from, one level of
government to another. Through these and other
techniques, local governments can take
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advantage of economies of scale to implement an
areawide control program.
(2) Determine whether necessary legal authority has
been delegated by the state. If state enabling
legislation is not adequate, officials should do as
much as possible within existing law and decide
what changes are needed. Then, they can work
through their state association of counties and
other interested groups for passage of
comprehensive sedimentation control enabling
legislation.
The legal basis for local governments to
control land use is state enabling law. Without
this enabling authority, local governments
cannot acquire land, develop facilities, or spend
public funds to regulate and control erosion and
sediment. To ensure that local governments have
the necessary powers, legislation should allow
political subdivisions to manage sediment in
coordination with other .environmental
protection programs.
Home rule cities and counties must closely
examine their charters to be sure they have the
authority to plan, regulate, and operate a
sedimentation control program.
State legislation should give local
government authority to:
(a) acquire land, buildings, and facilities
by purchase, lease, eminent domain,
and donation;
(b) plan and zone for the protection of
watersheds and natural drainage
courses;
(c) adopt and enforce necessary
ordinances, rules, and regulations;
(d) use various sources of revenue such as
bonds, taxes, general appropriations,
fees and service charges, and state and
federal assistance programs;
(e) make intergovernment agreements and
contracts;
(f) regulate private contractors and
developers through the issuance of
permits and licenses;
(g) prohibit any type of environmental
pollution.
(3) Require that soil and water conservation
considerations be incorporated incorporated in
community plans. Plans may be prepared by an
interagency committee of interested
departments, by a single department, by a
consultant, or by a combination of local
departments and consultants.
Community plans should include:
(a) data on population, land use,
transporation, and public facilities and
utilities:
(b) considerations of the climate,
topotraphy, geology, and related
factors, with the technical assistance
of any needed specialists so that
development and construction
activities are not detrimental to the
community's land and water
resources;
(c) presentation and evaluation of feasible
immediate and long-range solutions.
(4) Require that development and construction
project plans be prepared in coordination with
community plans.
Project plans should include specifications
for needed erosion and sediment control
measures.
(5) To prepare the best possible plans and achieve
implementation, elected officials should:
(a) solicit cooperation on an areawide
basis from city and county planners,
public works agencies, health officers,
engineers, soil conservation districts,
other appropriate departments, and
interested citizens;
(b) plan to inform the public about the
need for a comprehensive erosion and
sediment control program;
(c) provide leadership and initiative to
ensure acceptance and
implementation of the plan.
(6) Decide what type of organization is needed and
assign operating responsibilities.
No one organizational pattern for erosion
and sediment control can be said to be best.
Local conditions and custom will determine
which one or combination of agencies can be
assigned responsibility for administration of the
control program. The sedimentation control
agency or agencies must be responsible to elected
officials of general purpose governments.
Regardless of organization, the following
functions must be performed: policy making;
public information; budgeting; planning and
review; drafting, adoption, and enforcement of
standards; and operation of the system.
The main criterion for determining what
place a sedimentation control program should
have in the orgainzational structure of a local
government that existing agencies should be used
to carry out the program rather than creating a
new agency.
(7) Obtain technical information on current
community plans, and the community's
geological, topological, and soil conditions.
The program should stress the physical
limitations of every development and
construction site. Also, this should be considered
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in all land-use decisions. Basic principles would
include the development of large areas in small,
workable increments, the holding of exposure
time to a minimum and adapting site plans to the
natural topography.
Timely installation or structures, storm
drains, streets, and gutters is necessary plus
applicable conservation measures, such as the use
of mulch (as a temporary cover), temporary
seedings, early installations of permanent
vegetation, and the use of temporary structures,
terraces, waterways, and debris basins.
(8) Prepare a financial plan and capital budget so
that both immediate operating expenditures and
long-range capital financing needs are provided
for.
Although much of the cost for providing
sedimenation control will be assumed by private
industry (i.e., developers and builders), local
government will still be responsible for providing
control related to public improvements and for
their maintenance, e.g., parks, reservoirs, open
channel linings, etc.
Since the system must be financed within
the constraints of state laws and local charters
these should be thoroughly examined during the
planning process. Local governments can finance
the system when necessary following methods:
taxes, bond issues, loans, and/or service charges.
The local capital improvement budget should
schedule the financing of all necessary control
facilities and equipment.
If the sedimentation control program is
operated on an areawide basis, economies of
operation will often benefit each jurisdiction.
(9) Find out what federal, state, and private
technical and financial assistance is available and
take advantage of it.
Technical assistance from federal state, and
private sources is available to local governments
to develop measures related to sediment control.
On the federal level, the primary sources of
financial and technical assistance are the
Department of Agriculture the Department of
the Interior and Departme'nt of Housing and
Urban Development. Imaginative use of
assistance from other federal agencies may
provide help for local sedimentation control.
Many states provide technical assistance fur
soil and water conservation through conservation
districts and other special purpose governments
such as flood control districts. While financial
assistance is currently limited, recent
appropriation trends indicate a growing response
to environmental needs.
The home building industry, universities,
professional societies and private organizations
also can provide information and assistance.
(10) Direct the program's agencies to respond quickly
to all citizen complaints and conduct a
continuing educational program to inform the
public about the need for land use control in
relation to water pollution control.
(11) Use as many public information tools as possible
to reach citizens.
Among these tools are meetings at which
slides and films are shown; creation of events
such as "go-see" trips; speakers bureaus;
brochures and flyers; radio, T.V., newspapers,
and newsletter coverage and announcements;
exhibits; and communications media
endorsement.
(12) Employ a qualified committee of representatives
from public agencies, citizens groups, and
industry to periodically review, evaluate, and
report on the effectiveness of the program.
(13) Suivey recruitment needs. Where they exist,
solicit personnel from other levels of
government, professional organizations, and
universities. Also, technical manpower may, in
many cases, be involved in the program as a form
of technical assistance from other local, state and
federal government agencies.
(14) In-house training will be needed for program
personnel, especially for planners, and regulatory
and maintenance personnel. It should be noted
that during the development of these ordinances
and the program, local soil conservation districts
are available to work with local public agencies,
consultants, and engineers in the design and
installation of erosion control practices.
IV. Make the Sedimentation Control Program Developed
by the Task Force State Local Government Policy.
Charge local government department heads with
responsibility for developing policies and procedures
designed to implement the program, and solicit the
voluntary cooperation of the building industry.
Sedimentation control programs to date that
appear to work best are those that initially evolve
from some type of voluntary action. Urban
sedimentation control is a new field and all concerned
need an opportunity to test their ideas. Where
developers, planners and conservationists have an
opportunity to cooperate voluntarily on erosion
control projects, a solid foundation for future
regulatory program is provided for.
V. Make Sediment Control Mandatory Through Adoption
of an Ordinance or Land-Use Regulations.
The responsibility for developing the ordinance or
land-use regulation can best be assumed by the Task
Force. Also Task Force members know the existing
regulations and they have developed the basic
guidelines for the voluntary program.
The ordinance or land-use regulation, when
developed, would set the local standards. They should
be conceptual in scope; flexible in methods; positive in
direction; prohibitive of any type of land or water
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pollution; and above all, they must be clearly
understandable. They should be designed to control the
occasional irresponsible developer.
The ordinance or regulation should designate the
local agencies to be responsible for enforcing the
standards, e.g., plan, review and inspection.
WHAT SHOULD STATE GOVERNMENT DO?
I. Provide comprehensive state enabling legislation to
permit counties to manage soil and water resources.
Also, counties should be permitted and encouraged to
contract with internal municipalities and other
counties to develop areawide sedimentation control
programs.
Develop clear state guidelines with regard to
sedimentation standards. Water quality standards,
based on federal guidelines (Federal Water Pollution
Control Act of 1956, the Water Quality Act of 1965,
and the Clean Water Restoration Act of 1966) have
been adopted by all 50 states. States should ensure
that criteria for sedimentation control be included in
these standards.
III. Provide financial and technical assistance to local
sedimentation control programs. Such assistance can
be delivered through state agencies, should help local
programs conduct watershed research, conduct soils
studies, and provide major capital improvements, etc.
IV. Develop and execute an information distribution
program. Local governments and their agencies,
planning commissions, soil conservation district
personnel, etc., need to be informed on state laws and
their inte-pretation, what state assistance is available,
state policy guidelines, state planning programs and
other state activities.
V. Offer traning to local government and private industry
in sedimentation control techniques and principles.
VI. Develop and enforce a state sedimentation control
program to help control erosion and sediment on all
state projects and activities including highway
construction and maintenance, and state building
projects.
WHAT SHOULD THE
FEDERAL GOVERNMENT DO?
I. Help to promote national recognition of urban erosion
and sediment as constituting a major threat to
environmental quality.
II. Continue to contribute to technical and non-technical
research programs related to all aspects of urban
erosion and sediment problems.
III. Continue and improve upon financial and technical
assistance programs for state and local governments.
IV. Develop and enforce a federal sedimentation policy to
help control erosion and sediment on all federal
projects, and federally sponsored projects, including
federal buildings, federal highways, and on all federal
lands and waters. Sedimentation control policy should
be enforcible on all appropriate federal contracts.
whether carried out by public or private agencies.
U.S. GOVERNMENT PRINTING OFFICE : O—1 97O—81 8—273
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