EPA/600/X-99/XXX December 1999 Guidance Manual for Integrated Wet Weather Flow (WWF) Collection and Treatment Systems for Newly Urbanized Areas (New WWF Systems) Final Project Report by Robert Pitt and Melissa Lilburn Department of Civil and Environmental Engineering The University of Alabama at Birmingham Birmingham, Alabama S. Rocky Durrans, and Steve Burian Department of Civil and Environmental Engineering The University of Alabama Tuscaloosa, Alabama Stephan Nix College of Engineering and Technology Northern Arizona University Flagstaff, Arizona John Voorhees and Jeff Martinson Engineering Programming Consultants Madison, Wisconsin Project Officer Chi-Yuan Fan Urban Watershed Management Branch Wet Weather Flow Program U.S. Environmental Protection Agency Edison, New Jersey 08837 National Risk Management Research Laboratory Office of Research and Development U.S. Environmental Protection Agency Cincinnati, Ohio 45268 Notice (draft only, report not reviewed yet) The information in this document has been funded wholly or in part by the United States Environmental Protection Agency under cooperative agreement no. CX 824933-01-0 for the University of Alabama at Birmingham. Although it has been subjected to the Agency’s peer and administrative review and has been approved for publication as an EPA document, it does not necessarily reflect the views of the Agency and no official endorsement should be inferred. Also, the mention of trade names or commercial products does not imply endorsement by the United States government. ii Foreword Today’s rapidly developing and changing technologies and industrial products and practices frequently carry with them the increased generation of materials that, if improperly dealt with, can threaten both public health and the environment. The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation’s land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. These laws direct the EPA to perform research to define our environmental problems, measure the impacts and search for solutions. The National Risk Management Research Laboratory is responsible for planning, implementing, and managing research, development, and demonstration programs to provide an authoritative, defensive engineering basis in support of the policies, programs, and regulations of the EPA with respect to drinking water, wastewater, pesticides, toxic substances, solid and hazardous wastes, and Superfund-related activities. This publication is one of the products of that research and provides a vital communication link between the researcher and user community. The purpose of this report is to prepare a guidance manual integrating wet weather flow (WWF) collection and treatment systems for newly urbanized areas (New WWF Systems). It presents an extensive literature survey and discussion on changes in the design methods for urban wet weather runoff collection systems. It also integrates two computer models that can be easily used by designers and planners to comprehensively consider both drainage and water quality objectives in collection system designs. E. Timothy Oppelt, Director National Risk Management Research Laboratory iii Abstract This research project develop and demonstrated a methodology to guide design engineers in developing appropriate wet weather flow (WWF) drainage systems. Specific aspects of this guidance document address the historically mutually conflicting objectives of providing drainage services at the same time as decreasing stormwater pollutant discharges. Numerous drainage design procedures have been used for more than 100 years in the western world. However, major changes have occurred frequently over this period of time in response to specific problems encountered. Unfortunately, current drainage design procedures, while providing adequate levels of service if correctly implemented, commonly conflict with attempts to reduce stormwater pollutant discharges and associated receiving water problems. Water quality aspects of wet weather flow discharges and associated receiving water problems have only been studied for a relatively short period (a few decades), compared to conventional drainage designs (a few centuries), and few large-scale drainage systems adequately address both of these suitable objectives. This report presents a methodology that incorporates procedures that can be applied to the broad range of conditions that are likely to be encountered in the U.S. to address both drainage and water quality objectives. The methodology builds upon past experiences in drainage design (including some currently not being used in the U.S.) and uses current design tools that are readily available. As an example, it may be appropriate to consider the use of combined sewers and WWF discharge treatment in heavily urbanized areas. Source area controls, especially biofiltration practices that can be easily implemented with simple grading, may be appropriate in newly developing areas. In addition, critical source areas (such as vehicle service facilities) may require more extensive on-site treatment strategies. In-line storage with large diameter sewerage may also be appropriately utilized in some areas, depending on land costs and availability. Other design strategies addressed in this report include the conventional concept of design storms that have worked reasonably well for drainage objectives. Unfortunately, single design storms have been found to be generally inadequate in water quality evaluations of WWFs. Quasi-continuous evaluations over long periods of time may be more appropriate for these combinations of objectives. The use of inexpensive computers enables more comprehensive design evaluations to be rapidly and cost-effectively made. The use of computers has become common in many aspects of engineering practice, including drainage design and water quality evaluations. No currently available model adequately integrates these multiple objectives into a single system. This research activity therefore developed a methodology that includes the integration of two currently used computer models (SWMM for drainage design and CSO evaluations, plus SLAMM for source area runoff volume and pollutant reduction evaluations). Both of these programs are freely available and their use will not require the purchase of software. This research included the preparation of software utilities that makes the integrated use of these programs as seamless as possible. In addition, this project includes selected enhancements to both of these models to incorporate recent research results and innovations. Four of the investigators of this project were responsible for the design and programming of these models. iv Contents page Foreword …………………………………………………………………………………………………… ii Abstract …………………………………………………………………………………………………….. iii Tables ………………………………………………………………………………………………………. v Figures ……………………………………………………………………………………………………… vi 1.0 Introduction and Overall Design Approach ……...…………………………………………………… 1-1 Design methodology issues …………………...………………………………………………………... 1-2 Design methodology framework …………...…………………………………………………………... 1-5 References ………………………………………………………………………………………………. 1-15 2.0 The Beneficial Uses of Stormwater in Urban Areas and the Need for Change in Urban Water Management ………………………………………………………………………………………………... 2-1 Stormwater as an aesthetic element in urban areas …………………………………………………….. 2-1 Guidelines for the reuse of stormwater in urban areas ………………………………………………….. 2-4 The need for change in urban water management ……………………………………………………… 2-8 References ………………………………………………………………………………………………. 2-10 3.0 Historical Review of Wet Weather Flow Management and Designs for the Future ……………………. 3-1 Literature review methodology …………………………………………………………………………. 3-2 Ancient wet weather management practices ……………………………………………………………. 3-8 Wet weather practices: Middle Ages to the Nineteenth Century ……………………………………….. 3-11 Wet weather practices: 1960 – 1960 ……………………………………………………………………. 3-15 Wet weather practices: 1960 to the present …………………………………………………………….. 3-20 Summary of literature …………………………………………………………………………………... 3-46 Future outlook …………………………………………………………………………………………... 3-48 References ………………………………………………………………………………………………. 3-50 4.0 Current and Future Design Practices …………………………………………………………………... 4-1 Current storm drainage design practices ………………………………………………………………... 4-1 Wet weather flow management: Lessons learned from the past ………………………………………... 4-7 Stormwater drainage design objectives …………………………………………………………………. 4-16 Design of wet weather flow systems in the future ……………………………………………………… 4-19 References ………………………………………………………………………………………………. 4-22 5.0 The Integration of SWMM and SLAMM ……………………………………………………………… 5-1 Introduction ……………………………………………………………………………………………... 5-1 SWMM, the EPA’s Storm Water Management Model ………………………………………………… 5-3 SLAMM, the Source Loading and Management Model ………………………………………………... 5-24 SLAMM/SWMM Interface Program……..………...…………………………………………………... 5-46 References ………………………………………………………………………………………………. 5-48 Appendix A: The Integration of Water Quality and Drainage Design Objectives ………………………… A-1 Appendix B: U.S. EPA Urban Rainfall-Runoff Quality Data, U.S. EPA/USGS NURP Data, and Ontario’s B-1 TAWMS Data Plots ……….….……………………………………………………………………………. Appendix C: Using SLAMM ……………………………………………………………………………….