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HomeMy WebLinkAboutSWMM TOC and Preface.pdf CITY OF AUBURN Public Works Surface Water Management Manual November 2009 Revision #1 Effective June 6, 2014 City of Auburn Department of Public Works 25 West Main Auburn, WA 98001-4998 Notice This manual was developed and written by the City of Tacoma Environmental Services Maintenance Division and Science and Engineering Division staff. It has been modified for use within the City of Auburn with written permission from the City of Tacoma. Acknowledgement The City of Auburn would like to thank the City of Tacoma for permission to use the Tacoma Surface Water Management Manual (SWMM) as the basis for this document. The City would further like to acknowledge that the Tacoma SWMM was developed and written by the City of Tacoma Environmental Services Maintenance Division and Science and Engineering Division staff. Special thanks to Lorna Mauren, PE and the Tacoma Science and Engineering Division for providing an editable electronic version of the Tacoma SWMM. SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 i Table of Contents Table of Contents Preface..........................................................................................................................................................................1 Objective ..........................................................................................................................................................1 Organization of this Manual.................................................................................................................................2 How to Use this Manual........................................................................................................................................3 Development of Best Management Practices (BMPs) for Stormwater Management......................................4 Best Management Practices (BMPs)................................................................................................................................4 Source Control BMPs........................................................................................................................................................4 Treatment BMPs...............................................................................................................................................................4 Flow Control BMPs...........................................................................................................................................................4 Related Documentation........................................................................................................................................5 Department of Ecology’s Stormwater Management Manual.............................................................................................5 Applicable Federal, State and Local Regulatory Requirements........................................................................................5 Volume I: Stormwater Site Planning.........................................................................................................7 Purpose of this Volume........................................................................................................................................7 Content and Organization of this Volume..........................................................................................................7 Chapter 1 Development and Redevelopment Impacts..................................................................................8 1.1 Hydrologic Changes................................................................................................................................................8 1.2 Water Quality Changes...........................................................................................................................................8 1.3 Biological Changes..................................................................................................................................................9 Chapter 2 Areas with Special Development Requirements........................................................................10 2.1 Groundwater Protection Area 2.............................................................................................................................10 2.2 Impaired Water Bodies..........................................................................................................................................10 2.3 Floodplains............................................................................................................................................................10 Chapter 3 Minimum Requirements for New Development and Redevelopment.......................................11 3.1 Overview of the Minimum Requirements...............................................................................................................11 3.2 Exemptions............................................................................................................................................................12 3.2.1 Road Maintenance..................................................................................................................................12 3.2.2 Parking Lots and Parking Lot Maintenance.............................................................................................12 3.2.3 Underground Utility Projects....................................................................................................................13 3.2.4 Minor Clearing and Grading....................................................................................................................13 3.2.5 Emergencies...........................................................................................................................................13 3.2.6 Key Terms...............................................................................................................................................13 3.3 Applicability of the Minimum Requirements...........................................................................................................14 3.3.1 New Development...................................................................................................................................17 3.3.2 Redevelopment.......................................................................................................................................17 3.3.3 Assessed Value.......................................................................................................................................18 3.3.4 Roads......................................................................................................................................................18 3.3.5 Cumulative Impact Mitigation Requirement.............................................................................................19 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 ii Table of Contents 3.4 Description of Minimum Requirements..................................................................................................................21 3.4.1 Minimum Requirement #1: Preparation of a Stormwater Site Plan.........................................................21 3.4.2 Minimum Requirement #2: Construction Stormwater Pollution Prevention (SWPP)...............................21 3.4.3 Minimum Requirement #3: Source Control of Pollution...........................................................................22 3.4.4 Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls..............................23 3.4.5 Minimum Requirement #5: On-Site Stormwater Management................................................................23 3.4.6 Minimum Requirement #6: Runoff Treatment.........................................................................................24 3.4.7 Minimum Requirement #7: Flow Control.................................................................................................25 3.4.8 Minimum Requirement #8: Wetlands Protection.....................................................................................27 3.4.9 Minimum Requirement #9: Operation and Maintenance.........................................................................29 3.4.10 Minimum Requirement #10: Off-Site Analysis and Mitigation.................................................................29 3.5 Exceptions.............................................................................................................................................................30 Chapter 4 Preparation of Stormwater Site Plans.........................................................................................33 4.1 Stormwater Site Plan Outline.................................................................................................................................33 4.2 Plans Required After Stormwater Site Plan Approval............................................................................................40 4.3 Land Use Submittal Requirements........................................................................................................................40 Appendix A Regulatory Requirements.............................................................................................................41 Appendix B Stormwater Site Plan Submittal Requirements Checklist.........................................................46 Appendix C Hydraulic Analysis Worksheet.....................................................................................................53 Appendix D Maintenance Standards for Drainage Facilities.........................................................................55 Appendix E Wetlands and Stormwater Management Guidelines..................................................................85 Volume II: Stormwater Management for Construction Sites...............................................................113 Purpose of this Volume....................................................................................................................................113 Content and Organization of this Volume......................................................................................................113 Chapter 1 The 12 Elements of Construction Stormwater Pollution Prevention.....................................114 Chapter 2 Developing a Construction Stormwater Pollution Prevention Plan (SWPPP)......................123 2.1 General Requirements and Guidelines...............................................................................................................123 2.1.1 BMP Standards and Specifications.......................................................................................................123 2.1.2 General Principles.................................................................................................................................124 2.2 Step-by-Step Procedure......................................................................................................................................124 2.2.1 Step 1 – Data Collection........................................................................................................................124 2.2.2 Step 2 – Data Analysis..........................................................................................................................125 2.2.3 Step 3 – Construction SWPPP Development and Analysis..................................................................127 2.3 Construction SWPPP Checklists.........................................................................................................................128 Chapter 3 Standards and Specifications for Best Management Practices (BMPs).................................134 3.1 Source Control BMPs..........................................................................................................................................135 3.1.1 BMP C101: Preserving Natural Vegetation...........................................................................................135 3.1.2 BMP C102: Buffer Zone........................................................................................................................138 3.1.3 BMP C103: High Visibility Plastic or Metal Fence.................................................................................139 3.1.4 BMP C104: Stake and Wire Fence.......................................................................................................140 3.1.5 BMP C105: Stabilized Construction Entrance.......................................................................................141 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 iii Table of Contents 3.1.6 BMP C106: Wheel Wash.......................................................................................................................144 3.1.7 BMP C107: Construction Road/Parking Area Stabilization...................................................................146 3.1.8 BMP C120: Temporary and Permanent Seeding..................................................................................148 3.1.9 BMP C121: Mulching.............................................................................................................................154 3.1.10 BMP C122: Nets and Blankets..............................................................................................................156 3.1.11 BMP C123: Plastic Covering.................................................................................................................161 3.1.12 BMP C124: Sodding..............................................................................................................................164 3.1.13 BMP C125: Compost.............................................................................................................................165 3.1.14 BMP C126: Topsoiling...........................................................................................................................167 3.1.15 BMP C127: Polyacrylamide for Soil Erosion Protection........................................................................170 3.1.16 BMP C130: Surface Roughening..........................................................................................................173 3.1.17 BMP C131: Gradient Terraces..............................................................................................................175 3.1.18 BMP C140: Dust Control.......................................................................................................................177 3.1.19 BMP C150: Materials On Hand.............................................................................................................179 3.1.20 BMP C151: Concrete Handling.............................................................................................................180 3.1.21 BMP C152: Sawcutting and Surfacing Pollution Prevention.................................................................181 3.1.22 BMP C153: Material Delivery, Storage and Containment.....................................................................182 3.1.23 BMP C154: Concrete Washout Area.....................................................................................................184 3.1.24 BMP C160: Certified Erosion and Sediment Control Lead....................................................................190 3.1.25 BMP C161: Payment of Erosion Control Work......................................................................................192 3.1.26 BMP C162: Scheduling.........................................................................................................................193 3.1.27 BMP C180: Small Project Construction Stormwater Pollution Prevention............................................194 3.2 Runoff, Conveyance and Treatment BMPs.........................................................................................................196 3.2.1 BMP C200: Interceptor Dike and Swale................................................................................................196 3.2.2 BMP C201: Grass-Lined Channels.......................................................................................................199 3.2.3 BMP C202: Channel Lining...................................................................................................................203 3.2.4 BMP C203: Water Bars.........................................................................................................................205 3.2.5 BMP C204: Pipe Slope Drains..............................................................................................................207 3.2.6 BMP C205: Subsurface Drains.............................................................................................................210 3.2.7 BMP C206: Level Spreader...................................................................................................................213 3.2.8 BMP C207: Check Dams......................................................................................................................215 3.2.9 BMP C208: Triangular Silt Dike (Geotextile-Encased Check Dam)......................................................218 3.2.10 BMP C209: Outlet Protection................................................................................................................222 3.2.11 BMP C220: Storm Drain Inlet Protection...............................................................................................224 3.2.12 BMP C231: Brush Barrier......................................................................................................................234 3.2.13 BMP C232: Gravel Filter Berm..............................................................................................................236 3.2.14 BMP C233: Silt Fence...........................................................................................................................237 3.2.15 BMP C234: Vegetated Strip..................................................................................................................243 3.2.16 BMP C235: Straw Wattles.....................................................................................................................244 3.2.17 BMP C240: Sediment Trap...................................................................................................................247 3.2.18 BMP C241: Temporary Sediment Pond................................................................................................251 3.2.19 BMP C250: Construction Stormwater Chemical Treatment..................................................................258 3.2.20 BMP C251: Construction Stormwater Filtration.....................................................................................265 3.2.21 BMP C252: High pH Neutralization using CO2......................................................................................269 3.2.22 BMP C253: pH Control for High pH Water............................................................................................272 Appendix A Standard Notes for Erosion Control Plans................................................................................273 Appendix B Background Information on Chemical Treatment....................................................................274 Appendix C Construction SWPPP Short Form..............................................................................................277 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 iv Table of Contents Volume III: Surface Water Quantity Control and Conveyance............................................................307 Purpose of this Volume....................................................................................................................................307 Content and Organization of this Volume......................................................................................................307 Chapter 1 Hydrologic Analysis....................................................................................................................308 1.1 Minimum Computational Standards.....................................................................................................................308 1.2 Western Washington Hydrology Model...............................................................................................................308 1.3 Single-Event Hydrograph Method........................................................................................................................309 1.3.1 Design Storm.........................................................................................................................................309 1.3.2 Curve Number.......................................................................................................................................309 1.4 Closed Depression Analysis................................................................................................................................310 Chapter 2 Flow Control Design....................................................................................................................312 2.1 Roof Downspout Controls....................................................................................................................................312 2.1.1 Selection of Roof Downspout Controls..................................................................................................312 2.1.2 Downspout Infiltration Systems.............................................................................................................313 2.1.3 Downspout Dispersion Systems............................................................................................................319 2.1.4 Bioinfiltration “Rain Gardens”................................................................................................................321 2.1.5 Collect and Convey...............................................................................................................................326 2.2 Infiltration Facilities for Stormwater Flow Control ................................................................................................327 2.2.1 Purpose.................................................................................................................................................327 2.2.2 Description............................................................................................................................................327 2.2.3 Application.............................................................................................................................................327 2.2.4 Design Methodology..............................................................................................................................329 2.2.5 Simplified Approach..............................................................................................................................329 2.2.6 Detailed Approach.................................................................................................................................330 2.2.7 Site Characterization Criteria................................................................................................................334 2.2.8 Design Infiltration Rate Determination – Guidelines and Criteria..........................................................338 2.2.9 Three Methods for Determining Long-term Infiltration Rates for Sizing Infiltration Facilities.................339 2.2.10 Site Suitability Criteria (SSC).................................................................................................................343 2.2.11 Design Criteria for Infiltration Facilities..................................................................................................345 2.2.12 Construction Criteria..............................................................................................................................346 2.2.13 Maintenance Criteria.............................................................................................................................347 2.2.14 Verification of Performance...................................................................................................................347 2.2.15 Infiltration Basins...................................................................................................................................347 2.2.16 Infiltration Trenches...............................................................................................................................349 2.3 Detention Facilities..............................................................................................................................................351 2.3.1 Detention Ponds....................................................................................................................................351 2.3.2 Detention Tanks....................................................................................................................................367 2.3.3 Detention Vaults....................................................................................................................................371 2.3.4 Control Structures.................................................................................................................................375 2.3.5 Other Detention Options........................................................................................................................386 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 v Table of Contents Chapter 3 Conveyance System Design and Hydraulic Analysis.............................................................387 3.1 Conveyance System Analysis Requirements......................................................................................................387 3.1.1 On-site Analysis....................................................................................................................................387 3.1.2 Offsite Analysis (1/4 mile Downstream Analysis)..................................................................................388 3.2 Design Event.......................................................................................................................................................388 3.2.1 Additional Design Criteria......................................................................................................................389 3.3 Methods of Analysis............................................................................................................................................389 3.3.1 Rational Method....................................................................................................................................390 3.4 Pipes, Culverts and Open Channels....................................................................................................................396 3.4.1 Pipe Systems........................................................................................................................................396 3.4.2 Culverts.................................................................................................................................................413 3.4.3 Open Channels.....................................................................................................................................424 3.5 Outfalls Systems..................................................................................................................................................440 3.5.1 Outfall Design Criteria...........................................................................................................................440 3.5.2 Tightline Systems..................................................................................................................................448 3.5.3 Habitat Considerations..........................................................................................................................448 3.6 Pump Systems....................................................................................................................................................448 3.6.1 Design Criteria.......................................................................................................................................449 3.6.2 Pump Requirements..............................................................................................................................449 3.6.3 Additional Requirements.......................................................................................................................449 3.6.4 Sump Pumps.........................................................................................................................................450 3.7 Easements and Access......................................................................................................................................450 3.7.1 Public Easements..................................................................................................................................450 3.7.2 Private Easements................................................................................................................................451 3.7.3 Maintenance Access.............................................................................................................................451 Appendix A Auburn Design Storm.................................................................................................................453 Appendix B Procedure for Conducting a Pilot Infiltration Test...................................................................454 Volume IV: Source Control Best Management Practices....................................................................457 Purpose of this Volume....................................................................................................................................457 Content and Organization of this Volume......................................................................................................457 Chapter 1 Frequently Asked Questions......................................................................................................458 1.1 Applicability..........................................................................................................................................................458 1.2 Pollutants of Concern..........................................................................................................................................458 1.2.1 pH..........................................................................................................................................................458 1.2.2 Total Suspended Solids........................................................................................................................458 1.2.3 Oils and Greases...................................................................................................................................458 1.2.4 Oxygen-demanding Substances...........................................................................................................458 1.2.5 Metals....................................................................................................................................................459 1.2.6 Bacteria and Viruses.............................................................................................................................459 1.2.7 Nutrients................................................................................................................................................459 1.2.8 Toxic Organic Compounds....................................................................................................................459 1.2.9 Other Chemicals and Substances.........................................................................................................459 1.3 Types of Source Control BMPs...........................................................................................................................460 1.3.1 Operational BMPs.................................................................................................................................460 1.3.2 Structural BMPs....................................................................................................................................460 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 vi Table of Contents Chapter 2 Worksheet for Commercial and Industrial Activities...............................................................461 Chapter 3 BMPs for Homeowners...............................................................................................................465 3.1 Automobile Washing (for Single-Family Residences)..........................................................................................465 3.1.1 Suggested BMPs...................................................................................................................................465 3.2 Automobile Maintenance.....................................................................................................................................466 3.2.1 Required BMPs.....................................................................................................................................466 3.2.2 Suggested BMPs...................................................................................................................................466 3.3 Storage of Solid Wastes and Food Wastes.........................................................................................................467 3.3.1 Suggested BMPs...................................................................................................................................467 3.4 Composting.........................................................................................................................................................467 3.4.1 Suggested BMPs...................................................................................................................................467 3.5 Yard Maintenance and Gardening.......................................................................................................................468 3.5.1 Required BMPs.....................................................................................................................................468 3.5.2 Suggested BMPs...................................................................................................................................468 3.6 Swimming Pool and Spa Cleaning and Maintenance..........................................................................................469 3.6.1 Required BMPs.....................................................................................................................................469 3.6.2 Suggested BMPs...................................................................................................................................469 3.7 Household Hazardous Material Use, Storage, and Disposal..............................................................................469 3.7.1 Required BMPs.....................................................................................................................................470 3.7.2 Suggested BMPs...................................................................................................................................470 3.8 General Home Maintenance................................................................................................................................471 3.8.1 Suggested BMPs...................................................................................................................................471 3.9 Pet Waste............................................................................................................................................................471 3.9.1 Suggested BMPs...................................................................................................................................471 Chapter 4 BMPs for Commercial and Industrial Activities........................................................................472 4.1 BMPs to Consider for all Activities.......................................................................................................................472 4.2 Cleaning and Washing Activities.........................................................................................................................473 4.2.1 BMP A101: Cleaning or Washing of Tools, Engines and Manufacturing Equipment...........................473 4.2.2 BMP A102: Cleaning or Washing of Cooking Equipment......................................................................476 4.2.3 BMP A103: Washing, Pressure Washing and Steam Cleaning of Vehicles/Equipment/Building Structures..............................................................................................................................................478 4.2.4 BMP A104: Collection and Disposal of Wastewater in Mobile Interior Washing Operations.................481 4.3 Transfer of Liquid or Solid Materials....................................................................................................................483 4.3.1 BMP A201: Loading and Unloading Areas for Liquid or Solid Material.................................................483 4.3.2 BMP A202: Fueling at Dedicated Stations............................................................................................488 4.3.3 BMP A203: Vehicle Maintenance Activities...........................................................................................494 4.3.4 BMP A204: Mobile Fueling of Vehicles and Heavy Equipment.............................................................496 4.4 Production and Application Activities...................................................................................................................499 4.4.1 BMP A301: Concrete and Asphalt Mixing and Production at Stationary Sites......................................499 4.4.2 BMP A302: Concrete Pouring, Concrete Cutting, and Asphalt Application at Temporary Sites...........501 4.4.3 BMP A303: Manufacturing and Post-Processing of Metal Products.....................................................503 4.4.4 BMP A304: Wood Treatment Areas......................................................................................................505 4.4.5 BMP A305: Commercial Composting....................................................................................................507 4.4.6 BMP A306: Landscaping and Lawn/Vegetation Management..............................................................509 4.4.7 BMP A307: Painting, Finishing and Coating of Vehicles, Boats, Buildings and Equipment..................514 4.4.8 BMP A308: Commercial Printing Operations........................................................................................516 4.4.9 BMP A309: Manufacturing Operations – Outside.................................................................................517 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 vii Table of Contents 4.5 Storage and Stockpiling Activities.......................................................................................................................519 4.5.1 BMP A401: Storage or Transfer (Outside) of Solid Raw Materials, By-Products or Finished Products..................................................................................................................................519 4.5.2 BMP A402: Storage and Treatment of Contaminated Soils..................................................................522 4.5.3 BMP A403: Temporary Storage or Processing of Fruits or Vegetables................................................523 4.5.4 BMP A404: Storage of Solid Wastes and Food Wastes.......................................................................525 4.5.5 BMP A405: Recyclers and Scrap Yards................................................................................................527 4.5.6 BMP A406: Treatment, Storage or Disposal of Dangerous Wastes......................................................528 4.5.7 BMP A407: Storage of Liquid, Food Waste or Dangerous Waste Containers......................................529 4.5.8 BMP A408: Storage of Liquids in Above-Ground Tanks.......................................................................532 4.5.9 BMP A409: Parking and Storage for Vehicles and Equipment.............................................................535 4.6 Construction and Demolition Activities................................................................................................................536 4.6.1 BMP A501: Clearing, Grading and Preparation of Construction Sites..................................................536 4.6.2 BMP A502: Demolition of Buildings.......................................................................................................537 4.6.3 BMP A503: Building, Repair, Remodeling and Construction.................................................................538 4.7 Dust Control, and Soil and Sediment Control......................................................................................................540 4.7.1 BMP A601: Dust Control at Disturbed Land Areas and Unpaved Roadways and Parking Lots...........540 4.7.2 BMP A602: Dust Control at Manufacturing Sites...................................................................................542 4.7.3 BMP A603: Soil Erosion and Sediment Control at Industrial Sites........................................................543 4.8 Other Activities....................................................................................................................................................544 4.8.1 BMP A701: Commercial Animal Handling Areas...................................................................................544 4.8.2 BMP A702: Log Sorting and Handling...................................................................................................545 4.8.3 BMP A703: Boat Building, Maintenance and Repair.............................................................................546 4.8.4 BMP A704: Logging..............................................................................................................................549 4.8.5 BMP A705: Mining and Quarrying of Sand, Gravel, Rock, Peat, Clay and Other Materials..................551 4.8.6 BMP A706: Swimming Pool and Spa Cleaning and Maintenance........................................................552 4.8.7 BMP A707: De-Icing and Anti-Icing Operations for Streets & Highways...............................................553 4.8.8 BMP A708: Roof and Building Drains at Manufacturing and Commercial Buildings.............................554 4.8.9 BMP A709: Urban Streets.....................................................................................................................555 4.8.10 BMP A710: Railroad Yards...................................................................................................................557 4.8.11 BMP A711: Maintenance of Public and Utility Corridors and Facilities.................................................558 4.8.12 BMP A712: Maintenance of Roadside Ditches......................................................................................560 4.8.13 BMP A713: Maintenance of Stormwater Drainage and Treatment Facilities.......................................562 4.8.14 BMP A714: Spills of Oil and Hazardous Substances............................................................................564 4.8.15 BMP A715: Water Reservoir, Transmission Mainline, Wellhead, and Hydrant Flushing Activities.......566 4.8.16 BMP S101: Eliminate Illicit Storm Drainage System Connections........................................................568 4.8.17 BMP S102: Dispose of Contaminated Stormwater and Waste Materials Properly...............................569 4.8.18 BMP S103: Discharge Process Wastewater to a Sanitary Sewer, Holding Tank, or Water Treatment System......................................................................................................................570 4.8.19 BMP S108: Implement Integrated Pest Management Measures..........................................................571 4.8.20 BMP S109: Cleaning Catch Basins.......................................................................................................572 4.9 Cover and Surround Activities.............................................................................................................................573 4.9.1 BMP S104: Cover the Activity with a Roof or Awning...........................................................................573 4.9.2 BMP S105: Cover the Activity with an Anchored Tarp or Plastic Sheet................................................574 4.9.3 BMP S106: Pave the Activity Area and Slope to a Sump, Holding Tank, or Oil/Water Separator........575 4.9.4 BMP S107: Surround the Activity Area with a Curb, Dike, or Berm or Elevate the Activity...................576 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 viii Table of Contents Chapter 5 Regulations and Requirements..................................................................................................580 5.1 City of Auburn Codes and Ordinances................................................................................................................580 5.2 State, Federal, and Other Regulations and Requirements..................................................................................580 5.2.1 Washington State Department of Ecology Requirements for the Discharge of Process Wastewaters Directly to Surface Waters...............................................................................................580 5.2.2 Washington State Department of Ecology Requirements for Dangerous Waste Generators...............581 5.2.3 Washington State Department of Ecology Stormwater NPDES Permit Requirements.........................581 5.2.4 Washington State Department of Ecology Requirements for Underground and Above Ground Storage Tanks..........................................................................................................................582 5.2.5 U.S. Environmental Protection Agency and Ecology Emergency Spill Cleanup Requirements............582 5.2.6 Washington State Department of Agriculture Pesticide Regulations....................................................582 5.2.7 Puget Sound Clean Air Agency Air Quality Regulations.......................................................................582 Appendix A Quick Reference Phone Numbers..............................................................................................583 Appendix B Recycling/Disposal of Vehicle Fluids and Other Wastes.........................................................584 Appendix C Example of an Integrated Pest Management Program (IPM)...................................................585 Appendix D Recommendations for Management of Street Wastes............................................................588 Volume V: Water Quality Treatment BMPs...........................................................................................603 Purpose of this Volume....................................................................................................................................603 Content and Organization of this Volume......................................................................................................603 Chapter 1 Treatment Facility Selection Process........................................................................................604 1.1 Step-by-Step Selection Process for Treatment Facilities....................................................................................604 Chapter 2 Treatment Facility Menus...........................................................................................................610 2.1 Oil Control Menu..................................................................................................................................................610 2.1.1 Performance Goal.................................................................................................................................610 2.1.2 Options..................................................................................................................................................610 2.1.3 Application on the Project Site..............................................................................................................611 2.2 Phosphorus Treatment Menu..............................................................................................................................611 2.2.1 Performance Goal.................................................................................................................................611 2.2.2 Options..................................................................................................................................................611 2.3 Enhanced Treatment Menu.................................................................................................................................612 2.3.1 Performance Goal.................................................................................................................................612 2.3.2 Options..................................................................................................................................................612 2.4 Basic Treatment Menu........................................................................................................................................613 2.4.1 Performance Goal.................................................................................................................................613 2.4.2 Options..................................................................................................................................................614 Chapter 3 General Requirements for Stormwater Facilities.....................................................................615 3.1 Design Flow Volume and Flow Rate....................................................................................................................615 3.1.1 Water Quality Design Flow Volume.......................................................................................................615 3.1.1 Water Quality Design Flow Rate...........................................................................................................616 3.1.2 Flows Requiring Treatment...................................................................................................................616 3.2 Sequence of Facilities.........................................................................................................................................617 3.3 Setbacks, Slopes, and Embankments.................................................................................................................618 3.3.1 Setbacks................................................................................................................................................618 3.3.2 Side Slopes and Embankments............................................................................................................619 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 ix Table of Contents 3.4 Facility Liners.......................................................................................................................................................620 3.4.1 General Design Criteria.........................................................................................................................620 3.4.2 Design Criteria for Treatment Liners.....................................................................................................622 3.4.3 Design Criteria for Low Permeability Liner Options...............................................................................622 3.5 Hydraulic Structures............................................................................................................................................624 3.5.1 Flow Splitter Designs.............................................................................................................................624 3.5.2 Flow Spreading Options........................................................................................................................627 Chapter 4 Pretreatment................................................................................................................................632 4.1 Purpose...............................................................................................................................................................632 4.2 Application...........................................................................................................................................................632 4.3 BMPs for Pretreatment........................................................................................................................................632 4.3.1 BMP T610 Presettling Basin.................................................................................................................632 Chapter 5 Infiltration and Bio-infiltration Treatment Facilities.................................................................634 5.1 Purpose...............................................................................................................................................................634 5.2 Application...........................................................................................................................................................634 5.3 Site Suitability......................................................................................................................................................634 5.3.1 Setback Criteria (SSC-1).......................................................................................................................635 5.3.2 Groundwater Protection Areas (SSC-2)................................................................................................635 5.3.3 High Vehicle Traffic Areas (SSC-3).......................................................................................................635 5.3.4 Soil Infiltration Rate/Drawdown Time for Treatment (SSC-4)................................................................636 5.3.5 Depth to Bedrock, Water Table, or Impermeable Layer (SSC-5)..........................................................636 5.3.6 Soil Physical and Chemical Suitability for Treatment (SSC-6)..............................................................637 5.3.7 Seepage Analysis and Control (SSC-7)................................................................................................637 5.3.8 Cold Climate and Impact of Roadway Deicers (SSC-8)........................................................................637 5.3.9 Verification Testing of the Completed Facility.......................................................................................637 5.4 Site Characterization...........................................................................................................................................638 5.4.1 Field Methods used to Determine Subsurface Characterization...........................................................638 5.4.2 Design Infiltration Rate Determination...................................................................................................640 5.5 BMPs for Infiltration and Bio-infiltration Treatment..............................................................................................644 5.5.1 BMP T710 Infiltration Basins.................................................................................................................645 5.5.2 BMP T720 Infiltration Trenches.............................................................................................................646 5.5.3 BMP T730 Bio-infiltration Swale............................................................................................................648 Chapter 6 Sand Filtration Treatment Facilities...........................................................................................650 6.1 Purpose...............................................................................................................................................................650 6.2 Description...........................................................................................................................................................650 6.3 Applications and Limitations................................................................................................................................656 6.4 Site Suitability......................................................................................................................................................656 6.5 Design Criteria.....................................................................................................................................................656 6.5.1 Objective...............................................................................................................................................656 6.5.2 Sand Filter Sizing..................................................................................................................................656 6.6 Construction Criteria............................................................................................................................................659 6.7 Maintenance Criteria...........................................................................................................................................659 6.7.1 BMP T810 Sand Filter Vault..................................................................................................................661 6.7.2 BMP T820 Linear Sand Filter...............................................................................................................664 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 x Table of Contents Chapter 7 Biofiltration Treatment Facilities................................................................................................666 7.1 Purpose...............................................................................................................................................................666 7.2 Applications.........................................................................................................................................................666 7.3 Site Suitability......................................................................................................................................................666 7.4 Best Management Practices................................................................................................................................666 7.4.1 BMP T910 Basic Biofiltration Swale......................................................................................................667 7.4.2 BMP T920 Wet Biofiltration Swale........................................................................................................683 7.4.3 BMP T930 Continuous Inflow Biofiltration Swale..................................................................................685 7.4.4 BMP T940 Basic Filter Strip..................................................................................................................686 7.4.5 BMP T950 Narrow Area Filter Strip.......................................................................................................689 Chapter 8 Wetpool Facilities........................................................................................................................691 8.1 Purpose...............................................................................................................................................................691 8.2 Best Management Practices................................................................................................................................691 8.2.1 BMP T1010 Wetponds - Basic and Large.............................................................................................692 8.2.2 BMP T1020 Wetvaults...........................................................................................................................708 8.2.3 BMP T1030 Stormwater Treatment Wetlands.......................................................................................714 8.2.4 BMP T1040 Combined Detention and Wetpool Facilities .....................................................................720 8.3 Combined Detention and Wetvault......................................................................................................................724 8.4 Combined Detention and Stormwater Wetland...................................................................................................726 8.4.1 Sizing Criteria........................................................................................................................................726 8.4.2 Design Criteria.......................................................................................................................................726 8.4.3 Inlet and Outlet Criteria.........................................................................................................................726 8.4.4 Planting Requirements..........................................................................................................................726 Chapter 9 Oil and Water Separators............................................................................................................727 9.1 Purpose...............................................................................................................................................................727 9.2 Description...........................................................................................................................................................727 9.3 Applications/Limitations.......................................................................................................................................727 9.4 Site Suitability......................................................................................................................................................730 9.5 Design Criteria.....................................................................................................................................................731 9.5.1 General Considerations.........................................................................................................................731 9.5.2 Criteria for Separator Bays....................................................................................................................731 9.5.3 Criteria for Baffles..................................................................................................................................732 9.6 Oil and Water Separator BMPs...........................................................................................................................732 9.6.1 BMP T1110 API (Baffle type) Separator Bay........................................................................................733 9.6.2 BMP T1111 Coalescing Plate (CP) Separator Bay...............................................................................735 Chapter 10 Emerging Technologies..............................................................................................................737 10.1 Background.........................................................................................................................................................737 10.2 Emerging Technology and the City of Auburn.....................................................................................................737 10.3 Ecology Role in Evaluating Emerging Technologies...........................................................................................737 10.4 Evaluation of Emerging Technologies.................................................................................................................737 10.5 Assessing Levels of Development of Emerging Technologies............................................................................738 10.6 Examples of Emerging Technologies for Stormwater Treatment and Control.....................................................739 Appendix A Basic Treatment Receiving Waters............................................................................................741 Appendix B Procedure for Conducting a Pilot Infiltration Test...................................................................743 Appendix C Geotextile Specifications............................................................................................................745 Appendix D Turbulence and Short-Circuiting Factor....................................................................................747 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xi Table of Contents Volume VI: Low Impact Development and On-Site Stormwater Management..................................749 Purpose of this Volume....................................................................................................................................749 Content and Organization of this Volume......................................................................................................749 Chapter 1 General Requirements................................................................................................................750 1.1 Objectives............................................................................................................................................................750 1.2 Site Assessment..................................................................................................................................................750 1.3 Site Planning and Layout.....................................................................................................................................750 1.4 Retain Native Vegetation.....................................................................................................................................751 1.5 Minimize Clearing and Grading Impacts..............................................................................................................751 Chapter 2 Low Impact Development Best Management Practices...........................................................752 2.1 Application...........................................................................................................................................................752 2.2 Best Management Practices................................................................................................................................752 2.2.1 Dispersion and Soil Quality BMPs.........................................................................................................753 2.2.2 Site Design BMPs.................................................................................................................................769 2.2.3 Low Impact Development BMPS...........................................................................................................771 Glossary ......................................................................................................................................................789 References ......................................................................................................................................................830 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xii Figures Figures Figure I-3-1. Determining Minimum Requirements for New and Redevelopment Project Sites.................15 Figure I-3-2. Determining Minimum Requirements for Flow Control..........................................................16 Figure I-3-3. Determining Minimum Requirements for Road-Related Projects..........................................20 Figure II-3-1. Stake and Wire Fence.........................................................................................................140 Figure II-3-2. Stabilized Construction Entrance........................................................................................142 Figure II-3-3. Small-Site Stabilized Construction Entrance.......................................................................143 Figure II-3-4. Wheel Wash........................................................................................................................145 Figure II-3-5. Nets and Blankets – Slope Installation................................................................................159 Figure II-3-6. Nets and Blankets – Channel Installation...........................................................................160 Figure II-3-7. Soil Erosion Protection – Plastic Covering..........................................................................163 Figure II-3-8. Surface Roughening by Tracking and Contour Furrows.....................................................174 Figure II-3-9. Gradient Terraces...............................................................................................................176 Figure II-3-10. Temporary Concrete Washout Facility..............................................................................188 Figure II-3-11. Prefabricated Concrete Washout Container with Ramp...................................................189 Figure II-3-12. Typical Grass-Lined Channels..........................................................................................201 Figure II-3-13. Temporary Channel Liners................................................................................................202 Figure II-3-14. Soil Erosion Protection – Rip Rap Protection....................................................................204 Figure II-3-15. Pipe Slope Drains..............................................................................................................209 Figure II-3-16. Cross-Section of a Level Spreader...................................................................................214 Figure II-3-17. Detail of a Level Spreader.................................................................................................214 Figure II-3-18. Check Dams......................................................................................................................217 Figure II-3-19. Sediment Barrier – Triangular Sediment Filter Dikes........................................................220 Figure II-3-20. Sediment Barrier – Geosynthetic Dike..............................................................................221 Figure II-3-21. No Figure Placeholder.......................................................................................................223 Figure II-3-22. Drop Inlet with Block and Gravel Filter..............................................................................227 Figure II-3-23. Gravel and Wire Mesh Filter..............................................................................................228 Figure II-3-24. Catchbasin Filter...............................................................................................................229 Figure II-3-25. Block and Gravel Curb Inlet Protection.............................................................................231 Figure II-3-26. Curb and Gutter Sediment Barrier.....................................................................................233 Figure II-3-27. Brush Barrier.....................................................................................................................235 Figure II-3-28. Silt Fence...........................................................................................................................241 Figure II-3-29. Silt Fence Installation by Slicing........................................................................................242 Figure II-3-30. Straw Wattles....................................................................................................................246 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xiii Figures Figure II-3-31. Cross-Section of a Sediment Trap....................................................................................250 Figure II-3-32. Sediment Trap Outlet........................................................................................................250 Figure II-3-33. Sediment Pond..................................................................................................................255 Figure II-3-34. Sediment Pond Cross Section..........................................................................................255 Figure II-3-35. Sediment Pond Riser Detail..............................................................................................256 Figure II-3-36. Riser Inflow Curves...........................................................................................................257 Figure II-3-37. Floating Platform with Struts.............................................................................................260 Figure II-C-38. Sample Erosion and Sediment Control Plan....................................................................283 Figure II-C-39. Construction Entrance......................................................................................................291 Figure II-C-40. Stake and Wire Fence......................................................................................................292 Figure II-C-41. Sediment Barrier – Silt Fence...........................................................................................293 Figure II-C-42. Sediment Barrier – Triangular Sediment Filter Dikes.......................................................294 Figure II-C-43. Sediment Barrier – Geosynthetic Dike.............................................................................295 Figure II-C-44. Sediment (Berm) Barrier – Straw Wattle Rolls.................................................................296 Figure II-C-45. Sediment (Berm) Barrier – Sandbag Berm.......................................................................297 Figure II-C-46. Catch Basin Protection – Bag Filter..................................................................................298 Figure II-C-47. Catch Basin Protection – Inlet Gravel and Filter Fabric...................................................299 Figure II-C-48. Water Runoff Containment/Control – Sediment Trap Cross-Section...............................300 Figure II-C-49. Water Runoff Containment/Control – Sediment Trap Outlet............................................301 Figure II-C-50. Water Runoff Containment/Control – Drainage Swale Cross-Sections...........................302 Figure II-C-51. Soil Erosion Protection – Erosion Blankets and Turf Reinforcement Mats......................303 Figure II-C-52. Soil Erosion Protection – Rip Rap Protection...................................................................304 Figure II-C-53. Soil Erosion Protection – Pipe Slope Drains....................................................................305 Figure II-C-54. Soil Erosion Protection – Tarp Covering..........................................................................306 Figure III-2-1. Typical Downspout Infiltration Trench................................................................................316 Figure III-2-2. Alternative Downspout Infiltration Trench System for Coarse Sand and Gravel...............317 Figure III-2-3. Typical Downspout Dispersion Trench...............................................................................318 Figure III-2-4. Typical Infiltration Pond/Basin............................................................................................328 Figure III-2-5. USDA Textural Triangle.....................................................................................................337 Figure III-2-6. Observation Well Details....................................................................................................350 Figure III-2-7. Typical Detention Pond......................................................................................................353 Figure III-2-8. Typical Detention Pond Sections.......................................................................................354 Figure III-2-9. Overflow Structure..............................................................................................................355 Figure III-2-10. Examples of Permanent Surface Water Control Pond Sign............................................359 Figure III-2-11. Weir Section for Emergency Overflow Spillway...............................................................367 Figure III-2-12. Typical Detention Tank.....................................................................................................368 Figure III-2-13. Detention Tank Access Detail..........................................................................................369 Figure III-2-14. Typical Detention Vault....................................................................................................372 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xiv Figures Figure III-2-15. Flow Restrictor (TEE).......................................................................................................380 Figure III-2-16. Flow Restrictor (Baffle).....................................................................................................381 Figure III-2-17. Flow Restrictor (Weir).......................................................................................................382 Figure III-2-18. Simple Orifice...................................................................................................................383 Figure III-2-19. Rectangular, Sharp-Crested Weir....................................................................................383 Figure III-2-20. V-Notch, Sharp-Crested Weir...........................................................................................384 Figure III-2-21. Sutro Weir.........................................................................................................................384 Figure III-2-22. Riser Inflow Curves..........................................................................................................385 Figure III-3-23. Nomograph for Sizing Circular Drains Flowing Full.........................................................399 Figure III-3-24. Circular Channel Ratios...................................................................................................401 Figure III-3-25. Backwater Calculation Sheet...........................................................................................403 Figure III-3-26. Backwater Pipe Calculation Example ..............................................................................405 Figure III-3-27. Debris Barrier...................................................................................................................412 Figure III-3-28. Headwater Depth for Smooth Interior Pipe Culverts with Inlet Control............................415 Figure III-3-29. Headwater Depth for Corrugated Pipe Culverts with Inlet Control...................................416 Figure III-3-30. Junction Head Loss in Structures....................................................................................419 Figure III-3-31. Head for Culverts (Pipe W/”N”=0.012) Flowing Full with Outlet Control..........................420 Figure III-3-32. Head for Culverts (Pipe W/”N”=0.024) Flowing Full with Outlet Control..........................421 Figure III-3-33. Critical Depth of Flow for Circular Culverts......................................................................422 Figure III-3-34. Ditches – Common Section..............................................................................................427 Figure III-3-35. Drainage Ditches – Common Sections ............................................................................428 Figure III-3-36. Geometric Elements of Common Sections......................................................................429 Figure III-3-37. Open Channel Flow Profile Computation.........................................................................433 Figure III-3-38. Direct Step Backwater Method – Example.......................................................................434 Figure III-3-39. Mean Channel Velocity vs Medium Stone Weight (W50) and Equivalent Stone Diameter.................................................................................................................438 Figure III-3-40. Riprap Gradation Curve...................................................................................................439 Figure III-3-41. Pipe/Culvert Outfall Discharge Protection........................................................................443 Figure III-3-42. Flow Dispersal Trench......................................................................................................444 Figure III-3-43. Alternative Flow Dispersal Trench...................................................................................445 Figure III-3-44. Gabion Outfall Detail........................................................................................................446 Figure III-3-45. Diffuser TEE (an example of energy dissipating end feature).........................................447 Figure IV-4-1. Pressure Wash Water Recovery System..........................................................................474 Figure IV-4-2. Drip Pan.............................................................................................................................484 Figure IV-4-3. Drip Pan Within Rails.........................................................................................................485 Figure IV-4-4. Loading Dock with Door Skirt.............................................................................................487 Figure IV-4-5. Loading Dock with Overhang.............................................................................................487 Figure IV-4-6. Oil/Water Separator Layout...............................................................................................489 Figure IV-4-7. Covered Fuel Island...........................................................................................................490 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xv Figures Figure IV-4-8. Surrounding Activities Containing Oversized Equipment..................................................493 Figure IV-4-9. Enclose the Activity............................................................................................................518 Figure IV-4-10. Cover the Activity.............................................................................................................518 Figure IV-4-11. Covered Storage Area for Bulk Solids (including berm if needed)..................................520 Figure IV-4-12. Material Covered with Plastic Sheeting...........................................................................521 Figure IV-4-13. Secondary Containment Vessel......................................................................................530 Figure IV-4-14. Locking System for Drum Lid...........................................................................................531 Figure IV-4-15. Covered and Bermed Containment Area.........................................................................531 Figure IV-4-16. Mounted Container..........................................................................................................531 Figure IV-4-17. Above-Ground Tank Storage...........................................................................................534 Figure IV-4-18. Hydrant Flushing..............................................................................................................567 Figure IV-4-19. Examples of Covered Activities.......................................................................................573 Figure IV-4-20. Tarp Covering..................................................................................................................574 Figure IV-4-21. Paved Area with Sump Drain...........................................................................................575 Figure IV-4-22. Above-Ground Tank with Impervious Walls and Floor....................................................577 Figure IV-4-23. Containment Types..........................................................................................................578 Figure IV-4-24. Standby Generator...........................................................................................................579 Figure V-3-1. Flow Splitter, Option A........................................................................................................625 Figure V-3-2. Flow Splitter, Option B........................................................................................................626 Figure V-3-3. Flow Spreader Option A – Anchored Plate.........................................................................628 Figure V-3-4. Flow Spreader Option B – Concrete Sump Box.................................................................629 Figure V-3-5. Flow Spreader Option C – Notched Curb Spreader...........................................................630 Figure V-3-6. Flow Spreader Option D – Through-Curb Ports.................................................................631 Figure V-5-7. Observation Well Details.....................................................................................................649 Figure V-6-8. Sand Filtration Basin Preceded by Presettling Basin (Variation of a Basic Sand Filter)....651 Figure V-6-9. Sand Filter with a Pretreatment Cell (top view)..................................................................652 Figure V-6-10. Sand Filter with a Pretreatment Cell (side view)...............................................................653 Figure V-6-11. Sand Filter with Level Spreader (top view).......................................................................654 Figure V-6-12. Sand Filter with Level Spreader (side view).....................................................................655 Figure V-6-13. Sand Filter Vault (top view)...............................................................................................662 Figure V-6-14. Sand Filter Vault (side view).............................................................................................663 Figure V-6-15. Linear Sand Filter..............................................................................................................665 Figure V-7-16. Typical Swale Section.......................................................................................................667 Figure V-7-17. Geometric Formulas for Common Swale Shapes............................................................669 Figure V-7-18. The Relationship of Manning’s n with VR for Various Degrees of Flow Retardance (A-E).....................................................................................................675 Figure V-7-19. Biofiltration Swale Underdrain Detail................................................................................677 Figure V-7-20. Biofiltration Swale Low-Flow Drain Detail.........................................................................677 Figure V-7-21. Swale Dividing Berm.........................................................................................................678 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xvi Figures Figure V-7-22. Biofiltration Swale Access Features.................................................................................682 Figure V-7-23. Typical Filter Strip.............................................................................................................687 Figure V-7-24. Filter Strip Lengths for Narrow Right-of-Way....................................................................690 Figure V-8-25. Wetpond (top view)...........................................................................................................693 Figure V-8-26. Wetpond (side view).........................................................................................................694 Figure V-8-27. Headwater Depth for Smooth Interior Pipe Culverts with Inlet Control.............................697 Figure V-8-28. Headwater Depth for Corrugated Pipe Culverts with Inlet Control...................................698 Figure V-8-29. Critical Depth of Flow for Circular Culverts.......................................................................699 Figure V-8-30. Circular Channel Ratios....................................................................................................700 Figure V-8-31. Wetvault............................................................................................................................709 Figure V-8-32. Stormwater Wetland – Option 1........................................................................................717 Figure V-8-33. Stormwater Wetland – Option 2........................................................................................718 Figure V-8-34. Combined Detention and Wetpond (top view)..................................................................721 Figure V-8-35. Combined Detention and Wetpond (side view)................................................................722 Figure V-8-36. Alternative Configurations of Detention and Wetpool Areas............................................725 Figure V-9-37. API (Baffle Type) Separator..............................................................................................728 Figure V-9-38. Coalescing Plate Separator..............................................................................................729 Figure V-9-39. Spill Control Separator (not for oil treatment)...................................................................730 Figure V-D-40. Recommended Values of F for Various Values of vH/Vt..................................................747 Figure VI-2-1. Typical Dispersion Trench.................................................................................................756 Figure VI-2-2. Standard Dispersion Trench with Notched Grade Board..................................................757 Figure VI-2-3. Typical Downspout Splashblock Dispersion......................................................................758 Figure VI-2-4. Typical Concentrated Flow Dispersion for Steep Driveways.............................................760 Figure VI-2-5. Sheet Flow Dispersion for Driveways................................................................................762 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xvii Tables Tables Table I-D-1. Maintenance Standards..........................................................................................................55 Table I-E-2. Water Quality Ranges Found in Study Wetlands..................................................................100 Table II-3-1. Temporary Erosion Control Seed Mix..................................................................................152 Table II-3-2. Landscaping Seed Mix.........................................................................................................152 Table II-3-3. Low-Growing Turf Seed Mix.................................................................................................152 Table II-3-4. Bioswale Seed Mix...............................................................................................................152 Table II-3-5. Wet Area Seed Mix...............................................................................................................153 Table II-3-6. Meadow Seed Mix................................................................................................................153 Table II-3-7. Mulch Standards and Guidelines..........................................................................................155 Table II-3-8. Materials on Hand................................................................................................................179 Table II-3-9. Storm Drain Inlet Protection.................................................................................................224 Table II-3-10. Geotextile Standards..........................................................................................................237 Table II-3-11. Vegetated Strips.................................................................................................................243 Table II-3-12. Sediment Trap Sizing.........................................................................................................249 Table II-C-13. Sediment Trap Sizing.........................................................................................................286 Table II-C-14. Temporary Erosion Control Seed Mix................................................................................289 Table II-C-15. Mulch Standards and Guidelines.......................................................................................290 Table III-1-1. BMP Designs in Western Washington................................................................................308 Table III-1-2. Runoff Curve Numbers for Selected Agricultural, Suburban and Urban Areas..................311 Table III-2-3. Bioretention Soil Mix Aggregate Component......................................................................323 Table III-2-4. Sizing Table for Rain Gardens............................................................................................325 Table III-2-5. Modeling Assumptions for Rain Garden Sizing...................................................................326 Table III-2-6. Infiltration Rate Reduction Factors to Account for Biofouling and Siltation Effects for Ponds................................................................................................................333 Table III-2-7. Recommended Infiltration Rates based on USDA Soil Textural Classification...................340 Table III-2-8. Alternative Recommended Infiltration Rates Based on ASTM Gradation Testing..............341 Table III-2-9. Correction Factors to be Used with In-Situ Infiltration Measurements to Estimate Long-Term Design Infiltration Rates..................................................................................342 Table III-2-10. Permanent Surface Water Control Pond Sign Specifications...........................................359 Table III-2-11. Plant Selection Guide........................................................................................................363 Table III-2-12. Values of Cd for Sutro Weirs.............................................................................................379 Table III-3-13. Percentage Impervious for Fully Developed Conditions Offsite Tributary Areas..............389 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xviii Tables Table III-3-14. Runoff Coefficients – “C” Values for the Rational Method................................................391 Table III-3-15. Coefficients for the Rational Method.................................................................................392 Table III-3-16. Rainfall Intensities for the City of Auburn..........................................................................393 Table III-3-17. “n” and “k” Values Used in Time Calculations for Hydrographs........................................395 Table III-3-18. Percentage Impervious for Modeling Fully Developed Conditions....................................397 Table III-3-19. Manning’s “n” Values for Pipes..........................................................................................400 Table III-3-20. Backwater Calculation Sheet Notes..................................................................................404 Table III-3-21. Maximum Pipe Slopes, Velocities and Anchor Requirements..........................................408 Table III-3-22. Allowable Structures and Pipe Sizes.................................................................................408 Table III-3-23. Constants for Inlet Control Equations*..............................................................................417 Table III-3 24. Entrance Loss Coefficients................................................................................................423 Table III-3-25. Values of the Roughness Coefficient “n”...........................................................................430 Table III-3-26. Channel Protection............................................................................................................431 Table III-3-27. Rock Protection at Outfalls................................................................................................440 Table III-3-28. Additional Storm Drain Easement Widths.........................................................................451 Table III-A-29. Design Storm Precipitation Values...................................................................................452 Table IV-4-1. Uncovered Fuel Island Separator Sizing Requirements.....................................................491 Table IV-D-2. Typical TPH Levels in Street Sweeping and Catch Basin Solids.......................................597 Table IV-D-3. Typical c-PAH Values in Street Waste Solids and Related Materials................................598 Table IV-D-4. Typical Metals Concentrations in Catch Basin Sediments.................................................598 Table IV-D-5. Recommended Parameters & Suggested Values for Determining Reuse & Disposal Options.............................................................................................................599 Table IV-D-6. Recommended Sampling Frequency for Street Waste Solids...........................................600 Table IV-D-7. Pollutants in Catch Basin Solids – Comparison to Dangerous Waste Criteria..................600 Table IV-D-8. Typical Catch Basin Decant Values Compared to Surface Water Quality Criteria............601 Table IV-D-9. Typical Values for Conventional Pollutants in Catch Basin Decant...................................601 Table IV-D-10. Catch Basin Decant Values Following Settling................................................................602 Table V-1-1. Screening Treatment Facilities Based on Soil Type............................................................609 Table V-2-2. Treatment Trains for Phosphorus Removal.........................................................................612 Table V-2-3. Treatment Trains for Enhanced Treatment..........................................................................613 Table V-3-4. Treatment Facility Placement in Relation to Detention Facilities.........................................618 Table V-3-5. Lining Types Recommended for Runoff Treatment Facilities..............................................621 Table V-3-6. Acceptable Gradation for Compacted Till Liners.................................................................623 Table V-6-7. Sand Specifications..............................................................................................................658 Table V-6-8. Clay Liner Specifications......................................................................................................658 Table V-7-9. Sizing Criteria.......................................................................................................................670 Table V-7-10. Stability Check Steps (SC) Guide for Selecting Degree of Retardance..........................674 Table V-7-11. Guide to Selecting Maximum Permissible Swale Velocities for Stability...........................675 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 xix Tables Table V-7-12. Grass Seed Mixes Suitable for Biofiltration Swale Treatment Areas.................................680 Table V-7-13. Groundcovers & Grasses Suitable for the Upper Side Slopes of a Biofiltration Swale in Western Washington...........................................................................................680 Table V-7-14. Recommended Plants for Wet Biofiltration Swale.............................................................681 Table V-8-15. Emergent Wetland Species Recommended for Wetponds...............................................706 Table V-8-16. Distribution of Depths in Wetland Cell...............................................................................719 Table V-B-17. Correction Factors to be Used with In-Situ Infiltration Measurements to Estimate Long-Term Design Infiltration Rates..................................................................................744 Table V-C-18. Geotextile Properties for Underground Drainage Survivability Properties (WSDOT 2008 Standard Specifications or most current version).....................................745 Table V-C-19. Geotextile for Underground Drainage Filtration Properties (WSDOT 2008 Standard Specifications or most current version)..............................................................................745 Table V-C-20. Geotextile Strength Properties for Impermeable Liner Protection.....................................746 Table VI-2-1. Bioretention Soil Mix Aggregate Component......................................................................774 Table VI-2-2. Sizing Table for Rain Gardens............................................................................................777 Table VI-2-3. Modeling Assumptions for Rain Garden Sizing..................................................................778 SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 1 Preface Preface This manual provides guidance on the measures necessary to control the quantity and quality of stormwater produced by new development and redevelopment. This guidance contributes to the protection of receiving waters and is in compliance with the Washington State Department of Ecology (Ecology) water quality standards. These water quality standards include: • Chapter 173-200 WAC, Water Quality Standards for Groundwaters of the State of Washington • Chapter 173-201A, Water Quality Standards for Surface Waters of the State of Washington • Chapter 173-204, Sediment Management Standards Objective The objective of this manual is to establish minimum requirements for development and redevelopment projects of all sizes in the City of Auburn. It does this by providing guidance concerning how to prepare and implement stormwater site plans. The minimum requirements are satisfied by the application of Best Management Practices (BMPs). This manual is applicable to all types of land development – including residential, commercial, industrial, and roads. This manual can also be helpful in identifying options for retrofitting BMPs at existing development sites where appropriate. In such situations, application of BMPs from this manual is encouraged. The City recognizes, however, that there can be site constraints that make the strict application of these BMPs difficult. This manual is designed to be equivalent to Ecology’s 2005 Stormwater Management Manual for Western Washington. Ecology considers its manual to include all known, available and reasonable methods of prevention, control, and treatment (AKART). Ecology’s manual has no independent regulatory authority. However, Ecology has required as a condition of the City’s General Permit for Discharges from Municipal Separate Storm Sewers, the adoption of stormwater program components that are the substantial equivalent to the minimum requirements found in Ecology’s 2005 manual. The primary reason for using BMPs is to protect beneficial uses of water resources through the reduction of pollutant loads and concentrations, and through reduction of discharges (volumetric flow rates) causing stream channel erosion. If it is found that, after the implementation of BMPs advocated in this manual, beneficial uses are still threatened or impaired, additional controls may be appropriate. To accomplish these objectives the manual includes the following: • Minimum Requirements that cover a range of issues, such as preparation of Stormwater Site Plans, pollution prevention during the construction phase of a project, control of potential pollutant sources, treatment of runoff, control of SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 2 Preface stormwater flow volumes, protection of wetlands, and long-term operation and maintenance. The Minimum Requirements applicable to a project vary depending on the type and size of the proposed project. • Best Management Practices (BMPs) that can be used to meet the minimum requirements. BMPs are defined as schedules of activities, prohibitions of practices, maintenance procedures, managerial practices, or structural features that prevent or reduce adverse impacts to waters of Washington State. BMPs are divided into those for short-term control of stormwater from construction sites, and those addressing long-term management of stormwater at developed sites. Long-term BMPs are further subdivided into those covering management of the volume and timing of stormwater flows, prevention of pollution from potential sources, and treatment of runoff to remove sediment and other pollutants. • Guidance on how to prepare and implement Stormwater Site Plans. The Stormwater Site Plan is a comprehensive report that describes existing site conditions, explains development plans, examines potential offsite effects, identifies applicable Minimum Requirements, and proposes stormwater controls for both the construction phase and long-term stormwater management. The project proponent submits the Stormwater Site Plan to the City of Auburn for review, and the City uses the plan to evaluate a proposed project for compliance with stormwater requirements. It is not the intent of this manual to make the City of Auburn a guarantor or protector of public or private property with regard to land development activities. Organization of this Manual The Surface Water Management Manual is divided into six volumes: • Volume I defines the geographic scope of the manual, provides the information on stormwater flow and quality control, and describes how to prepare and implement a Stormwater Site Plan. • Volume II describes BMPs for short-term stormwater management at construction sites. • Volume III covers hydrologic analysis and BMPs to control flow volumes from developed sites. • Volume IV describes BMPs to minimize pollution generated by potential pollution sources at developed sites. • Volume V presents BMPs to treat runoff that contains sediment or other pollutants from developed sites. • Volume VI presents BMPs for low impact development. A Glossary at the end of the manual defines terminology used in all six volumes. A list of References provides both source documentation and a list of additional information resources. SURFACE WATER MANAGE MENT MANUAL NOVEMBER 2009 3 Preface How to Use this Manual This manual is designed for a variety of users.  Project proponents should start by reviewing the minimum requirements described in Volume I. Volume I also describes a Stormwater Site Plan and provides guidance on how to develop this plan.  City staff will use this manual to review Stormwater Site Plans, check BMP designs and provide technical advice to project proponents. City staff will also use this manual as a reference when designing public works projects. All development and redevelopment projects within the City of Auburn shall meet the requirements of this manual unless specifically exempted by this manual or the City Engineer.  The City Engineer shall have authority to modify requirements to protect the health, safety or welfare of the public on the basis of information regarding threatened water quality, erosion problems or potential habitat destruction, flooding, protection of uninterruptible services, or endangerment to property. The City Engineer shall also have the authority to modify requirements based upon increases in requirements imposed by state or federal agencies, where existing requirements are not applicable to the particular site, or other pertinent factors.  Permits may refer to this manual or the BMPs contained in this manual. In those cases, affected permit-holders or applicants should use this manual for specific guidance on how to comply with those permit conditions. Where requirements in this manual are also mandated by any other law, ordinance, resolution, rule or regulation, the more restrictive requirement shall apply. Note: Drawing and detail figures included throughout these volumes are intended for illustrative purposes only. Where any discrepancy exists between figure elements and specific design criteria, the design criteria shall take precedence. SURFACE WATER MANAGE MENT MANUAL NOVEMBER 2009 4 Preface Development of Best Management Practices (BMPs) for Stormwater Management The method by which this manual controls the adverse impacts of development and redevelopment is through the application of Best Management Practices. Best Management Practices (BMPs) Best Management Practices are defined as schedules of activities, prohibitions of practices, maintenance procedures, and structural and/or managerial practices, that when used singly or in combination, prevent or reduce the release of pollutants and other adverse impacts to waters of Washington State. The types of BMPs are source control, treatment, and flow control. BMPs that involve construction of engineered structures are often referred to as facilities in this manual. For instance, the BMPs referenced in the menus of Chapter 2 in Volume 5 are called Treatment Facilities. Source Control BMPs Source control BMPs prevent or reduce pollution, or other adverse effects of stormwater, from occurring. In this manual, source control BMPs are classified as operational or structural. Examples of source control BMPs include methods as various as using mulches and covers on disturbed soil, putting roofs over outside storage areas, and berming areas to prevent stormwater run-on and pollutant runoff. It is generally more cost-effective to use source controls to prevent pollutants from entering runoff than to treat runoff to remove pollutants. Treatment BMPs Treatment BMPs include facilities that remove pollutants by simple gravity settling of particulate pollutants, filtration, biological uptake, and soil adsorption. Treatment BMPs can accomplish significant levels of pollutant load reductions if properly designed and maintained. Flow Control BMPs Flow control BMPs typically control the rate, frequency, and flow duration of stormwater surface runoff. The need to provide flow control BMPs depends on whether a development site discharges to a stream system or wetland, either directly or indirectly. Stream channel erosion control can be accomplished by BMPs that detain runoff flows and also by those which physically stabilize eroding stream banks. Both types of measures may be necessary. Only the former is covered in this manual. The size of such a facility can be reduced by changing the extent to which a site is disturbed. In regard to wetlands, it is necessary to not alter the natural hydroperiod. This means control of flows from a development such that the wetland is within certain elevations at different times of the year and short-term elevation changes are within the prescribed limits. If, however, the wetland was fed by local groundwater elevations during the dry season, the impervious surface additions and the bypassing practice may cause variations from the dry season elevations which might need mitigation. The city has additional requirements that are related to surface water management, including wetlands, critical areas, and flood protection. Refer to the City of Auburn Code. SURFACE WATER MANAGEMENT MANUAL NOVEMBER 2009 5 Preface Related Documentation Department of Ecology’s Stormwater Management Manual This manual was modeled after the Stormwater Management Manual for Western Washington, published by the Department of Ecology in February, 2005. Ecology’s stormwater manual was originally developed in response to a directive of the Puget Sound Water Quality Management Plan (PSWQA 1987 et seq.). The Puget Sound Water Quality Authority (since replaced by the Puget Sound Partnership) recognized the need for overall guidance for stormwater quality improvement. It incorporated requirements in its plan to implement a cohesive, integrated stormwater management approach through the development and implementation of programs by local jurisdictions, and the development of rules, permits and guidance by Ecology. The Puget Sound Water Quality Management Plan included a stormwater element (SW-2.1) requiring Ecology to develop a stormwater technical manual for use by local jurisdictions. Ecology’s original stormwater manual (the Stormwater Management Manual for the Puget Sound Basin, published in 1992) was developed to meet this requirement. In the years hence Ecology updated its stormwater management guidance and requirements applicable to all of western Washington. Refer to Volume I, Appendix A for the regulatory requirements which support the relationship between the Auburn manual and Ecology’s manual. Applicable Federal, State and Local Regulatory Requirements Refer to Volume I, Appendix A for all applicable federal, state, and local regulatory requirements for this manual. • Endangered Species Act • Section 401 Water Quality Certifications • Puget Sound Water Quality Management Plan • Ecology NPDES Program • Hydraulic Project Approvals • Aquatic Lands Use Authorizations • Watershed/Basin Planning • Total Maximum Daily Loads • Underground Injection Control Authorization THIS PAGE INTENTIONALLY LEFT BLANK.