Recent Additions

Retrofitting Control Facilities for Wet Weather Flow Treatment
(PDF, 7.1 MB, 210 pp, about PDF)
EPA/600/R-00/020
2000
Available technologies were evaluated to demonstrate the technical feasibility and cost effectiveness of retrofitting existing facilities to handle wet-weather flow. Cost/benefit relationships were also compared t construction of new conventional control and treatment facilities. Desk top analyses of 13 separate retrofit examples were performed for (1) converting or retrofitting primary settling tanks with dissolved air flotation and lamellae and/or microsand-enhanced plate or tube settling units, (2) retrofitting existing wet-weather flow storage tanks to provide enhanced settling/treatment and post-storm solids removal, (3) converting dry ponds to wet ponds for enhanced treatment, (4) retrofitting wet-weather flow storage tanks for dry-weather flow augmentation, (5) using storage for sanitary sewer overflow control, (6) retrofitting for industrial wastewater control in a combined sewer system, and (7) bringing outdated/abandoned treatment plants back online as wet-weather flow treatment facilities. This analysis demonstrated that retrofitting existing wet-weather flow facilities can be technically feasible in most cases and may be more cost effective than construction of new conventional control and treatment facilities. The feasibility and cost effectiveness of retrofitting was found to be a function of site-specific conditions and treatment requirements. Retrofitting processes will better enable communities to meet EPA's National CSO Policy and stormwater permitting program requirements....Continue Reading.

Real Time Control of Urban Drainage Networks
EPA/600/R-06/120
2006
Real-time control (RTC) is a custom-designed, computer-assisted management technology for a specific sewerage network to meet the operational objectives of its collection/conveyance system. RTC can operate in several modes, including a mode that is activated during a wet weather flow event to control local flooding and sewage releases. RTC of conveyance systems has been emerging as an attractive and cost-effective approach that can be undertaken in addition to (or in lieu of) more traditional construction-focused alternatives such as sewer separation or construction of storage facilities. Although there are still relatively few documented applications of RTC to large urban sewerage systems, the technology has been successfully implemented.

RTC implementation includes several different aspects, including hydraulics, instrumentation, remote monitoring, process control, software development, mathematical modeling, organizational issues, and forecasting of rainfall or flows. Addressing each of these issues in detail would require a large document, beyond the scope of this report. Accordingly, the report provides a summary and a broad introduction to these different issues and does not elaborate on them in great detail.

The main goal of the report is to provide a guide on RTC technology to facilitate its understanding and acceptance by the user community. The primary audience is the practicing engineer, in a municipality or in a consulting firm, who has had limited exposure to RTC. Also, the report should serve as a resource document for use by federal and state program officials and regulators, researchers, and the interested public.

There is no simple or single “recipe” for successful RTC implementation. The report provides some guidance for the methodology to be used in the design, development, and implementation of RTC systems, but it does not identify or recommend a single solution that will fit any municipality or any set of operational issues...Continue Reading.

Performance of Stormwater Retention Ponds and Constructed Wetlands in Reducing Microbial Concentrations
EPA/600/R-06/102
2006
Stormwater runoff can transport high concentrations of pathogens to receiving waters. Bacteria indicator organisms, as surrogates for pathogens, are the most often reported cause of receiving water impairments. Stormwater best management practices (BMPs) are often considered effective tools to mitigate the effects of stormwater pollutants before they appear in receiving waters. However, BMP performance for pathogen removal is not well documented. Many questions remain on the transport and fate of indicator bacteria that enter and exit stormwater BMPs.

The National Risk Management Research Laboratory (NRMRL), part of U.S. EPA’s Office of Research and Development (ORD) investigated the fate of indicator organisms in the stormwater runoff entering and exiting two commonly used BMPs, constructed wetlands and retention ponds. This research used controlled-condition, pilot-scale systems that represent larger field-scale systems to determine the dominant mechanisms that influence the reduction of indicator organism concentrations. The pilot-scale work was supported by bench-scale laboratory experiments investigating the effects of single parameters such as temperature, sunlight, and salinity on indicator organism inactivation rates. Presented in this report are the results of developing techniques for creating bacterially enriched stormwater, bench-scale studies, and the pilot-scale BMP research. Bench-scale study results show that the temperature and sunlight affect the inactivation rates significantly. Results from the pilot-scale research suggest that constructed wetlands and retention ponds lower microbial concentrations in stormwater runoff. Bacteria inactivation generally followed the first-order, K-C* empirical model that acknowledges an irreducible concentration. Factors such as sunlight and temperature provide much of the inactivation in indicator bacteria, but other factors (e.g., predation, sedimentation, filtration, sorption, pH, and BOD) appear to also influence indicator bacteria concentrations. Future research validating results of the pilot-scale systems to field-scale systems should be done.

Developing microbial inactivation models to predict effluent concentrations from BMPs will help reduce the uncertainty and improve the capabilities of surface water quality models. First-order models that do not consider background concentrations or resuspension, may underestimate actual bacterial concentrations....Continue Reading.

BMP Modeling Concepts and Simulation
EPA 600/R-06/033
2006
In order to minimize impacts of urban non point source pollution and associated costs of control (storage and treatment) associated with wet-weather flows (WWFs), stormwater runoff volumes and pollutant loads must be reduced. A number of control strategies and so-called “best management practices” (BMPs) are being used to mitigate runoff volumes and associated non point source (diffuse) pollution due to WWFs and include ponds, bioretention facilities, infiltration trenches, grass swales, filter strips, dry wells, and cisterns. Another control option is popularly termed “low impact development” (LID) – or hydrologic source control – and strives to retain a site’s pre-development hydrologic regime, reducing WWF and the associated non point source pollution and treatment needs.

Methodologies are needed to evaluate these BMPs, their effectiveness in attenuating flow and pollutants, and for optimizing their cost/performance since most models only partially simulate BMP processes. Enhanced simulation capabilities will help planners derive the least-cost combination for effectively treating WWFs. There is currently a confusing array of options for analyzing hydrologic regimes and planning for LID. Integrating available BMP and LID processes into one model is highly desirable.

This work analyzes several current modeling methods to evaluate BMP performance with the intention of facilitating the integration of improved BMP modeling methods into the U.S. Environmental Protection Agency (EPA) Storm Water Management Model (SWMM). Several other models are examined as part of this study. Options for enhancement of SWMM’s LID simulation capabilities are also presented. Two extensive case studies in Portland, Oregon help to clarify current SWMM capabilities and needs for enhancement. The effort documented in this report is linked to a parallel effort at the University of Colorado related to optimization strategies for WWF control...Continue Reading.

Methods for Optimizing Urban Wet-Weather Control System (PDF by Chapters, 394 Kb, 15 pp)
EPA/600/R-06/034
2006
To minimize impacts of urban nonpoint source pollution and associated costs of control (storage and treatment) associated with wet-weather flows (WWFs), stormwater runoff volumes and pollutant loads must be reduced. A number of control strategies, so-called “best management practices” (BMPs) are being used to mitigate runoff volumes and associated nonpoint source (diffuse) pollution due to WWFs. They include ponds, bioretention facilities, infiltration trenches, grass swales, filter strips, dry wells, and cisterns. Another control option is popularly termed “low impact development” (LID) – or hydrologic source control – and strives to retain a site’s pre-development hydrologic regime, reducing WWF and the associated nonpoint source pollution and treatment needs.

Methods are needed to evaluate these BMPs, their effectiveness in attenuating flow and pollutants, and to optimize their cost/performance since most models only partially simulate BMP processes. Enhanced simulation capabilities will help planners derive the least-cost combination for effectively treating WWFs. There is a confusing array of options for analyzing hydrologic regimes and planning for LID. Integrating available BMP and LID processes into one model is highly desirable.

Described in this report is a methodology that integrates simulation (“what–if” analysis) and optimization (“what’s– best” analysis) for evaluating which of the myriad of alternative wet-weather controls deserves the title of “best.” The optimization analysis integrates process simulation, cost-effectiveness analysis, performance specification, and optimization methods to find this “best” solution. All of these analyses are performed using a spreadsheet platform. Following a general review of optimization methods and previous applications to wet-weather control optimization, a series of spreadsheet based tools are described. Use of these spreadsheets allows for an improved method for spatial analysis and therefore, to a more accurate representation of land use. A spreadsheet-based method for analyzing precipitation records to partition them into storm events or to develop intensity-duration-frequency curves is presented, along with simple methods for estimating infiltration and performing flow routing. Influent pollutant loads may be described simply as event mean concentrations (EMCs). A spreadsheet version of the STORM model for continuous simulations is presented, followed by an update on the cost of wet-weather controls. A primer on optimization methods describes the ease of using these techniques in a spreadsheet environment and the application of these tools to optimize storm sewer design is discussed. At the conclusion, an integrated stormwater management optimization model that combines land use optimization and a storage-release system is outlined.

The effort documented in this report is linked to a parallel effort at Oregon State University titled: BMP Modeling Concepts and Simulation. This work analyzes several current modeling methods to evaluate BMP performance with the intention of facilitating integration of improved BMP modeling methods into the EPA’s Storm Water Management Model (SWMM). Several other models are examined as part of this study. Options for enhancement of SWMM’s LID simulation capabilities are also presented. Two extensive case studies in Portland, Oregon help to clarify current SWMM capabilities and needs for enhancement...Continue Reading.

White Paper on Improvement of Structural Integrity Monitoring for Drinking Water Mains
EPA/600/R-05/038
2005
The improvement of water main structural integrity monitoring (SIM) capability as an approach for reducing high risk drinking water main breaks and inefficient maintenance scheduling is explored in this white paper. Inadequate SIM capability for water mains can cause repair, rehabilitation, or replacement (R₃) to be scheduled either late or early. Late R₃ can allow serious deterioration, main breaks, and their associated consequences to occur. Early R₃ is inefficient, which adversely affects system maintenance priorities and economics. Existing SIM technologies inadequately characterize various combinations of pipe materials, configurations, and failure modes. Fortunately, substantial research to improve SIM is underway or planned, but mostly for high risk, non-drinking water applications. A systematic effort by EPA and other Federal agencies, in cooperation with relevant stakeholders, is recommended to identify, prioritize, and capitalize on opportunities to accelerate SIM capability improvement. Acceleration of SIM improvement research is especially important at this time, since: (1) for the next 30+ years a steep rise in R₃ decision-making is projected for our aging water mains; (2) multiple technology transfer, collaboration, and leveraging opportunities exist; and, (3) SIM capability improvement takes time...Continue Reading.

Filter Fence Design Aid for Sediment Control at Construction Sites
EPA/600/R-04/185
2004
The focus of environmental policy and regulation is increasing on water quality issues. Particularly, there is a more widespread awareness that sediment is one of the most prevalent pollutants and that the impacts of excess sediment released into lakes and rivers can be as damaging as those caused by agricultural or industrial chemicals. Due to their nature, construction sites are typically principal sources of undesirable sediment releases. To make construction activity easier, sites are generally cleared of all vegetation. The exposed soil is then made further susceptible to erosion by being disturbed by grading and vehicle traffic. Frequently, the only action taken to attempt to control sediment releases is the installation of a filter/silt fence. This approach is not generally successful, for several reasons:

• The fence is not installed as recommended by existing guidelines.
• The fence is not adequately maintained over time.
• The fence is not located for effective control of sediment.
• The site is not suitable for a silt fence.

The first two items can best be addressed through public education along with adoption and enforcement of regulations. The third and fourth items can be addressed through development of a design aid, which was the objective of this research...Continue Reading.

The Use of Best Management Practices (BMPs) in Urban Watersheds
EPA/600/R-04/184
2004
Stormwater is part of a natural hydrologic process. However, human activities, especially those in an urban environment, cause significant changes in patterns of stormwater flow from land into receiving waters. The undesirable impacts of stormwater runoff can be controlled by prudent management efforts, referred to as best management practices (BMPs). The purpose of this report is to provide a general information on the most commonly used structural BMP options, the design considerations involved, and the general guidelines for monitoring, selection, implementation, and associated costs of BMPs in urban watersheds...Continue Reading.

Stormwater Best Management Practice Design Guide
EPA/600/R-04/121
2004
As this document is being published by U.S. Environmental Protection Agency’s Office of Research and Development, its primary focus is not the promulgation of regulation or the enforcement of policy. Instead, this is a forward looking document that tries to develop ways to address water quality issues of best management practices (BMPs) in the absence of a complete regulatory framework. The intended audience for this document is the municipal planners, regulators and watershed managers who will be deciding how BMPs will be applied in their locality.

In the past, BMP models were purely hydrologic; now they require two components: hydrology and quality. The purpose of this document is two-fold:

• to present the state-of-the-practice for BMP design for water quality control
• to aid the end user in making better choices.

This document is the first volume of a three-volume series that provides guidance on the selection and design of stormwater management BMPs. This volume provides general considerations associated with the selection and design of BMPs.

Volume 2 provides specific design guidance for a group of onsite BMP control practices that are referred to as vegetative biofilters, and includes the following BMP control practices:

• grass swales
• filter and buffer strips
• bioretention cells.

Volume 3 provides specific guidance for basin type BMPs, which are the most widely used type of BMP. The basin types that are covered include:

• extended detention basins (dry)
• retention ponds (wet)
• constructed wetland ponds
• infiltration basins.

Volume 2 is also the only volume that contains the full storm routing which is applicable to all treatment controls detailed in Volume 2 and 3.

The purpose of this three-volume series is to guide the selection of BMPs that will be effective in preventing or mitigating the adverse impacts of urbanization either through retrofitting of existing BMPs or application of newly constructed BMPs to new development. There is sufficient evidence to indicate that urbanization is causing environmental impacts. Existing BMP technologies can resolve some of the impacts. There are continuing innovative BMP efforts such as bioretention, infiltration basins and low impact development that are being pursued at the research level and in some actual applications, which should improve our ability to reduce or prevent impacts due to urbanization and land-use changes.

The authors have also developed a spreadsheet tool - Integrated Design and Assessment for Environmental Loadings (IDEAL) - which can aid the reader in examining the hydrology, sediment transport and water quality for BMP devices. Aspects of the capabilities of the IDEAL spreadsheet tool are demonstrated through the use of relevant equations for BMP water quality design and several examples as presented in Volume 2 and Volume 3...Continue Reading.

Sewer Sediment and Control A Management Practices Reference Guide
EPA/600/R-04/059
2004
Sewer sediment is one of major sources of pollutants in urban wet-weather flow (WWF) discharges that include combined-sewer overflow (CSO), separate sanitary-sewer overflow (SSO), and stormwater runoff. During low-flow, dry-weather periods, sanitary wastewater solids deposited in combined sewers have significant adverse impacts on the integrity of the sewerage system and receiving-water quality. In the US, estimates of dry-weather flow deposition in combined sewers vary from 5 to 30% of the daily inputs of solids and pollutants. In Europe, average deposition rates have been measured at between 30 and 500 g/m/d. Even sewers that are supposedly designed to be 'self-cleansing' will have transient sediment deposits and part of the load in transport will move near the sewer invert...Continue Reading.

Stormwater Treatment at Critical Areas The Multi-Chambered Treatment Train
EPA/600/R-99/017
1999
This is the first volume for this report series and describes the work conducted during the early years of this project through recent full-scale tests. Other volumes in this report series describe the results of field investigations of storm drain inlet devices and the use of filter media for stormwater treatment.

The first project phase investigated typical toxicant concentrations in stormwater, the origins of these toxicants, and storm and land-use factors that influenced these toxicant concentrations. Nine percent of the 87 stormwater source area samples analyzed were considered extremely toxic (using the Microtox™ toxicity screening procedure). Thirty-two percent of the samples exhibited moderate toxicity, while fifty-nine percent of the samples had no evidence of toxicity. Only a small fraction of the organic toxicants analyzed were frequently detected, with 1,3-dichlorobenzene and fluoranthene the most commonly detected organics investigated (present in 23 percent of the samples). Vehicle service and parking area runoff samples had many of the highest observed concentrations of organic toxicants. All metallic toxicants analyzed were commonly found in all samples analyzed...Continue Reading.