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Stormwater Management Guidebook

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Stormwater Management Guidebook Stormwater Management Guidebook Prepared for: District Department of the Environment Watershed Protection Division District of Columbia Prepared by: Center for Watershed Protection 8390 Main Street Ellicott City, MD 21043 July 2013 Acknowledgements A major undertaking such as this requires the dedication and cooperative efforts of many individuals. Dr. Hamid Karimi, Director of Natural Resources; Sheila Besse, Associate Director of Watershed Protection; Jeff Seltzer, Associate Director of Stormwater Management; and Timothy Karikari, Branch Chief of Technical Services deserve credit for their overall leadership and support for this project. Their willingness to allow staff to pursue ideas to their fullest and provide necessary time, resources, and managerial support laid the foundation for much innovation. Project Manger Rebecca C. Stack, DDOE-Technical Services Lead Authors Greg Hoffmann, P.E., Center for Watershed Protection Rebecca C. Stack, DDOE-Technical Services Brian Van Wye, DDOE-Stormwater Management Editor Sherry Schwechten, DDOE-Stormwater Management Contributors and Peer Reviewers Joseph Battiata, P.E., Center for Watershed Protection Evan Branosky, DDOE-Stormwater Management Gerald Brock, Ph.D., George Washington University Josh Burch, DDOE-Planning and Restoration Collin R. Burrell, DDOE-Water Quality Walter Caldwell, DDOE-Inspection and Enforcement Jonathan Champion, DDOE-Stormwater Management Reid Christianson P.E., Ph.D., Center for Watershed Protection Laine Cidlowski, Office of Planning Richard DeGrandchamp, Ph.D., University of Colorado/Scientia Veritas Elias Demessie, DDOE-Technical Services Diane Douglas, DDOE-Water Quality Matthew Espie, DDOE-Stormwater Management Alex Forasté, Williamsburg Environmental Group, Inc. Laura Gardner, Center for Watershed Protection Timothy Karikari, P.E., CPESC, CFM, DDOE-Technical Services Melissa Keeley, Ph.D., George Washington University Tim Klien, DDOE-Inspection and Enforcement Sarah Lawson, Ph.D., Rainwater Management Solutions Leah Lemoine, DDOE-Planning and Restoration Susan Libes, Ph.D., Coastal Carolina University, Conway, SC Kelly (Collins) Lindow, P.E., (Center for Watershed Protection)/RK&K Dennis Lye, Ph.D., US EPA Massoud Massoumi, DDOE-Technical Services Abdi Musse, P.E., DDOE-Technical Services Phetmano Phannavong, P.E., C.F.M., DDOE-Technical Services Philip C. Reidy, P.E., Geosyntec Consultants Stephen Reiling, DDOE-Planning and Restoration Emily Rice, DDOE-Stormwater Management Tom Schueler, Chesapeake Bay Stormwater Network Jeff Seltzer, P.E., DDOE-Stormwater Management Tanya Spano, MWCOG-Water Resources Bill Stack, P.E., Center for Watershed Protection Meredith Upchurch, DDOT-Stormwater June M. Weintraub, ScD, San Francisco Department of Public Health iii Preface Technical information regarding future updates to the District of Columbia Stormwater Management Guidebook will be available at http://ddoe.dc.gov/publication/stormwater- guidebook. Notices regarding future versions of the manual will be posted on this website. Future versions are expected to occur, at most, once a year. v Contents Acknowledgements .................................................................................................................................... iii Preface .......................................................................................................................................................... v List of Tables ............................................................................................................................................ xvi List of Figures ......................................................................................................................................... xviii List of Equations ....................................................................................................................................... xx Chapter 1 Introduction to the Stormwater Management Guidebook ............................................. 1 1.1 Introduction .................................................................................................................................. 1 1.2 Purpose and Scope ........................................................................................................................ 1 1.3 Impacts of Urban Runoff .............................................................................................................. 2 1.3.1 Hydrologic Impacts ............................................................................................................... 2 1.3.2 Water Quality Impacts .......................................................................................................... 4 1.4 References .................................................................................................................................... 6 Chapter 2 Minimum Control Requirements ...................................................................................... 7 2.1 District of Columbia Stormwater Management Performance Requirements ............................... 7 2.2 Stormwater Retention Volume ..................................................................................................... 9 2.3 Water Quality Treatment Volume .............................................................................................. 13 2.4 Extreme Flood Requirements ..................................................................................................... 20 2.5 Minimum Criteria for Determining Extreme Flood Requirements ............................................ 20 2.6 Additional Stormwater Management Requirements ................................................................... 22 2.7 Hydrology Methods .................................................................................................................... 22 2.8 Acceptable Urban BMP Options ................................................................................................ 23 Chapter 3 Stormwater Best Management Practices (BMPs) ......................................................... 27 3.1 Standard Best Management Practice Design Guidance Format ................................................. 27 3.2 Green Roofs ................................................................................................................................ 29 3.2.1 Green Roof Feasibility Criteria ........................................................................................... 29 3.2.2 Green Roof Conveyance Criteria ........................................................................................ 30 3.2.3 Green Roof Pretreatment Criteria ....................................................................................... 31 3.2.4 Green Roof Design Criteria ................................................................................................ 31 3.2.5 Green Roof Landscaping Criteria ....................................................................................... 35 3.2.6 Green Roof Construction Sequence .................................................................................... 37 3.2.7 Green Roof Maintenance Criteria ....................................................................................... 39 3.2.8 Green Roof Stormwater Compliance Calculations ............................................................. 40 3.2.9 References ........................................................................................................................... 40 3.3 Rainwater Harvesting ................................................................................................................. 43 vii 3.3.1 Rainwater Harvesting Feasibility Criteria ........................................................................... 45 3.3.2 Rainwater Harvesting Conveyance Criteria ........................................................................ 47 3.3.3 Rainwater Harvesting Pretreatment Criteria ....................................................................... 48 3.3.4 Rainwater Harvesting Design Criteria ................................................................................ 50 3.3.5 Rainwater Harvesting Landscaping Criteria ....................................................................... 62 3.3.6 Rainwater Harvesting Construction Sequence .................................................................... 62 3.3.7 Rainwater Harvesting Maintenance Criteria ....................................................................... 63 3.3.8 Rainwater Harvesting: Stormwater Compliance Calculations ............................................ 65 3.3.9 References ........................................................................................................................... 65 3.4 Impervious Surface Disconnection ............................................................................................. 67 3.4.1 Impervious Surface Disconnection Feasibility Criteria ...................................................... 69 3.4.2 Impervious Surface Disconnection Conveyance Criteria ................................................... 70 3.4.3 Impervious Surface Disconnection Pretreatment Criteria ................................................... 70 3.4.4 Impervious Surface Disconnection Design Criteria ............................................................ 70 3.4.5 Impervious Surface Disconnection Landscaping Criteria ................................................... 74 3.4.6 Impervious Surface Disconnection
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