Table of Contents Preface... xv Objective... xv Organization of this Manual...xvi How to Use this Manual...xvii Development of Best Management Practices (BMPs) for Stormwater Management...xviii Best Management Practices (BMPs)... xviii Source Control BMPs... xviii Treatment BMPs... xviii Flow Control BMPs... xviii Related Documentation... xx Department of Ecology s Stormwater Management Manual...xx Applicable Federal, State and Local Regulatory Requirements...xx Volume 1: Stormwater Site Planning...1 Chapter 1 Development and Redevelopment Impacts...2 1.1 Hydrologic Changes... 2 1.2 Water Quality Changes... 2 1.3 Biological Changes... 3 Chapter 2 Watershed Designations...4 2.1 City of Tacoma Watersheds... 4 2.2 Land Use... 6 2.3 Impaired Water Bodies... 8 2.4 Floodplains... 8 2.5 Tacoma s Watersheds Summary Descriptions... 8 2.6 Watershed Flow Control and Water Quality Requirements... 18 Chapter 3 Minimum Requirements for New Development and Redevelopment...24 3.1 Overview of the Minimum Requirements... 24 3.2 Exemptions... 25 3.3 Applicability of the Minimum Requirements... 27 3.4 Description of Minimum Requirements... 34 3.5 Exceptions... 45 Chapter 4 Preparation of Stormwater Site Plans...47 4.1 Stormwater Site Plan Outline... 47 4.2 Plans Required After Stormwater Site Plan Approval... 54 i Table of Contents
4.3 Land Use Submittal Requirements... 54 Appendix A Regulatory Requirements...57 Appendix B Stormwater Site Plan Submittal Requirements Checklist...62 Appendix C Hydraulic Analysis Worksheet...68 Appendix D Maintenance Standards for Drainage Facilities...70 Appendix E Wetlands and Stormwater Management Guidelines...102 Appendix F Bond Qualities Worksheet...130 Volume 2: Stormwater Management for Construction Sites...135 Chapter 1 The 12 Elements of Construction Stormwater Pollution Prevention...136 Chapter 2 Developing a Construction Stormwater Pollution Prevention Plan (SWPPP)...145 2.1 General Requirements and Guidelines... 145 2.2 Step-by-Step Procedure... 146 2.3 Construction SWPPP Checklists... 152 Chapter 3 Standards and Specifications for Best Management Practices (BMPs)...158 3.1 Source Control BMPs... 159 3.2 Runoff, Conveyance and Treatment BMPs... 221 Appendix A Standard Notes for Erosion Control Plans...300 Appendix B Background Information on Chemical Treatment...301 Appendix C Construction SWPPP Short Form...304 Volume 3: Surface Water Quantity Control and Conveyance...335 Chapter 1 Hydrologic Analysis...336 1.1 Minimum Computational Standards... 336 1.2 Western Washington Hydrology Model... 337 1.3 Single-Event Hydrograph Method... 337 1.4 Closed Depression Analysis... 338 Chapter 2 Flow Control Design...340 2.1 Roof Downspout Controls... 340 2.2 Infiltration Facilities for Stormwater Flow Control... 356 2.3 Detention Facilities... 379 Chapter 3 Conveyance System Design and Hydraulic Analysis...412 3.1 Conveyance System Analysis Requirements... 412 3.2 Design Event... 413 3.3 Methods of Analysis... 414 3.4 Pipes, Culverts and Open Channels... 421 3.5 Outfalls Systems... 466 3.6 Pump Systems... 474 3.7 Easements, Access, and Dedicated Tracts... 476 Appendix B Procedure for Conducting a Pilot Infiltration Test...480 ii Table of Contents
Volume 4: Source Control BMPs...483 Chapter 1 Frequently Asked Questions...484 1.1 Applicability... 484 1.2 Pollutants of Concern... 484 1.3 Types of Source Control BMPs... 486 Chapter 2 Worksheet for Commercial and Industrial Activities...487 Chapter 3 BMPs for Homeowners...491 3.1 Automobile Washing (for Single-Family Residences)... 491 3.2 Automobile Maintenance... 492 3.3 Storage of Solid Wastes and Food Wastes... 493 3.4 Composting... 493 3.5 Yard Maintenance and Gardening... 494 3.6 Swimming Pool and Spa Cleaning and Maintenance... 495 3.7 Household Hazardous Material Use, Storage, and Disposal... 496 3.8 General Home Maintenance... 497 3.9 Pet Waste... 498 Chapter 4 BMPs for Commercial and Industrial Activities...499 4.1 BMPs To Consider for all Activities... 499 4.2 Cleaning and Washing Activities... 500 4.3 Transfer of Liquid or Solid Materials... 510 4.4 Production and Application Activities... 526 4.5 Storage and Stockpiling Activities... 546 4.6 Construction and Demolition Activities... 564 4.7 Dust Control, and Soil and Sediment Control... 568 4.8 Other Activities... 572 4.9 Cover and Surround Activities... 601 Chapter 5 Regulations and Requirements...608 5.1 City of Tacoma Codes and Ordinances... 608 5.2 State, Federal, and Other Regulations and Requirements... 609 Appendix B Recycling/Disposal of Vehicle Fluids and Other Wastes...615 Appendix C Example of an Integrated Pest Management Program...616 Appendix D Recommendations for Management of Street Wastes...619 Volume 5: Water Quality Treatment BMPs...635 Chapter 1 Treatment Facility Selection Process...636 1.1 Step-by-Step Selection Process for Treatment Facilities... 636 Chapter 2 Treatment Facility Menus...642 2.1 Oil Control Menu... 642 2.2 Phosphorus Treatment Menu... 643 2.3 Enhanced Treatment Menu... 644 iii Table of Contents
2.4 Basic Treatment Menu... 646 Chapter 3 General Requirements for Stormwater Facilities...647 3.1 Design Flow Volume and Flow Rate... 647 3.2 Sequence of Facilities... 648 3.3 Setbacks, Slopes, and Embankments... 649 3.4 Facility Liners... 651 3.5 Hydraulic Structures... 655 Chapter 4 Pretreatment...663 4.1 Purpose... 663 4.2 Application... 663 4.3 Best Management Practices (BMPs) for Pretreatment... 664 Chapter 5 Infiltration and Bio-infiltration Treatment Facilities...665 5.1 Purpose... 665 5.2 Application... 665 5.3 Site Suitability... 665 5.4 Site Characterization... 669 5.5 Best Management Practices (BMPs) for Infiltration and Bio-infiltration Treatment... 675 Chapter 6 Sand Filtration Treatment Facilities...681 6.1 Purpose... 681 6.2 Description... 681 6.3 Applications and Limitations... 687 6.4 Site Suitability... 687 6.5 Design Criteria... 687 6.6 Construction Criteria... 690 6.7 Maintenance Criteria... 690 Chapter 7 Biofiltration Treatment Facilities...697 7.1 Purpose... 697 7.2 Applications... 697 7.3 Site Suitability... 697 7.4 Best Management Practices... 697 Chapter 8 Wetpool Facilities...722 8.1 Purpose... 722 8.2 Best Management Practices... 722 8.3 Combined Detention and Wetvault... 754 8.4 Combined Detention and Stormwater Wetland... 756 Chapter 9 Oil and Water Separators...757 9.1 Purpose... 757 9.2 Description... 757 9.3 Applications/Limitations... 757 iv Table of Contents
9.4 Site Suitability... 760 9.5 Design Criteria... 761 9.6 Oil and Water Separator BMPs... 762 Chapter 10 Emerging Technologies...768 10.1 Background... 768 10.2 Emerging Technology and the City of Tacoma... 768 10.3 Ecology Role in Evaluating Emerging Technologies... 768 10.4 Evaluation of Emerging Technologies... 769 10.5 Assessing Levels of Development of Emerging Technologies... 769 10.6 Examples of Emerging Technologies for Stormwater Treatment and Control... 770 Appendix A Basic Treatment Receiving Waters...771 Appendix B Procedure for Conducting a Pilot Infiltration Test...773 Appendix C Geotextile Specifications...775 Appendix D Turbulence and Short-Circuiting Factor...777 Volume 6: Low Impact Development and On-Site Stormwater Management...779 Chapter 1 General Requirements...780 1.1 Objectives... 780 1.2 Site Assessment... 780 1.3 Site Planning and Layout... 780 1.4 Retain Native Vegetation... 781 1.5 Minimize Clearing and Grading Impacts... 781 Chapter 2 Low Impact Development Best Management Practices...782 2.1 Application... 782 2.2 Best Management Practices... 782 Glossary...819 References...864 v Table of Contents
Figures Figure 1. City of Tacoma Watersheds... 5 Figure 2. South Tacoma Groundwater Protection District (STGWPD)... 12 Figure 3. Natural Resource Damage Assessment (NRDA) Areas and Other Sensitive Habitat Sites... 13 Figure 4. Determining Minimum Requirements for New and Redevelopment Project Sites... 28 Figure 5. Determining Minimum Requirements for Flow Control... 29 Figure 6. Determining Minimum Requirements for Road-Related Projects... 33 Figure 7. Stake and Wire Fence... 164 Figure 8. Stabilized Construction Entrance... 166 Figure 9. Small-Site Stabilized Construction Entrance... 167 Figure 10. Wheel Wash... 169 Figure 11. Nets and Blankets Slope Installation... 183 Figure 12. Nets and Blankets Channel Installation... 184 Figure 13. Soil Erosion Protection Plastic Covering... 187 Figure 14. Surface Roughening by Tracking and Contour Furrows... 198 Figure 15. Gradient Terraces... 200 Figure 16. Temporary Concrete Washout Facility... 212 Figure 17. Prefabricated Concrete Washout Container with Ramp... 213 Figure 18. Typical Grass-Lined Channels... 226 Figure 19. Temporary Channel Liners... 227 Figure 20. Soil Erosion Protection Rip Rap Protection... 229 Figure 21. Pipe Slope Drains... 234 Figure 22. Cross-Section of a Level Spreader... 239 Figure 23. Detail of a Level Spreader... 239 Figure 24. Check Dams... 242 Figure 25. Sediment Barrier Triangular Sediment Filter Dikes... 245 Figure 26. Sediment Barrier Geosynthetic Dike... 246 Figure 27. Inlet Gravel & Filter Fabric... 248 Figure 28. Drop Inlet with Block and Gravel Filter... 252 Figure 29. Gravel and Wire Mesh Filter... 253 Figure 30. Catchbasin Filter... 254 Figure 31. Block and Gravel Curb Inlet Protection... 256 Figure 32. Curb and Gutter Sediment Barrier... 258 Figure 33. Brush Barrier... 260 Figure 34. Silt Fence... 266 vi List of Figures
Figure 35. Silt Fence Installation by Slicing... 267 Figure 36. Straw Wattles... 271 Figure 37. Cross-Section of a Sediment Trap... 275 Figure 38. Sediment Trap Outlet... 275 Figure 39. Sediment Pond... 280 Figure 40. Sediment Pond Cross Section... 280 Figure 41. Sediment Pond Riser Detail... 281 Figure 42. Riser Inflow Curves... 282 Figure 43. Floating Platform with Struts... 285 Figure 44. Sample Erosion and Sediment Control Plan... 310 Figure 45. Construction Entrance... 318 Figure 46. Stake and Wire Fence... 319 Figure 47. Sediment Barrier Silt Fence... 320 Figure 48. Sediment Barrier Triangular Sediment Filter Dikes... 321 Figure 49. Sediment Barrier Geosynthetic Dike... 322 Figure 50. Sediment (Berm) Barrier Straw Wattle Rolls... 323 Figure 51. Sediment (Berm) Barrier Sandbag Berm... 324 Figure 52. Catch Basin Protection Bag Filter... 325 Figure 53. Catch Basin Protection Inlet Gravel and Filter Fabric... 326 Figure 54. Water Runoff Containment/Control Sediment Trap Cross-Section... 327 Figure 55. Water Runoff Containment/Control Sediment Trap Outlet... 328 Figure 56. Water Runoff Containment/Control Drainage Swale Cross-Sections... 329 Figure 57. Soil Erosion Protection Erosion Blankets and Turf Reinforcement Mats... 330 Figure 58. Soil Erosion Protection Rip Rap Protection... 331 Figure 59. Soil Erosion Protection Pipe Slope Drains... 332 Figure 60. Soil Erosion Protection Tarp Covering... 333 Figure 61. Typical Downspout Infiltration Trench... 344 Figure 62. Alternative Downspout Infiltration Trench System for Coarse Sand and Gravel... 345 Figure 63. Typical Downspout Dispersion Trench... 346 Figure 64. Typical Infiltration Pond/Basin... 357 Figure 65. USDA Textural Triangle... 366 Figure 66. Observation Well Details... 378 Figure 67. Typical Detention Pond... 381 Figure 68. Typical Detention Pond Sections... 382 Figure 69. Overflow Structure... 383 Figure 70. Examples of Permanent Surface Water Control Pond Sign... 387 Figure 71. Weir Section for Emergency Overflow Spillway... 392 Figure 72. Typical Detention Tank... 393 Figure 73. Detention Tank Access Detail... 394 vii List of Figures
Figure 74. Typical Detention Vault... 397 Figure 75. Flow Restrictor (TEE)... 405 Figure 76. Flow Restrictor (Baffle)... 406 Figure 77. Flow Restrictor (Weir)... 407 Figure 78. Simple Orifice... 408 Figure 79. Rectangular, Sharp-Crested Weir... 408 Figure 80. V-Notch, Sharp-Crested Weir... 409 Figure 81. Sutro Weir... 409 Figure 82. Riser Inflow Curves... 410 Figure 83. Nomograph for Sizing Circular Drains Flowing Full... 423 Figure 84. Circular Channel Ratios... 425 Figure 85. Backwater Calculation Sheet... 427 Figure 86. Backwater Pipe Calculation Example... 429 Figure 87. Debris Barrier... 438 Figure 88. Headwater Depth for Smooth Interior Pipe Culverts with Inlet Control... 441 Figure 89. Headwater Depth for Corrugated Pipe Culverts with Inlet Control... 442 Figure 90. Junction Head Loss in Structures... 445 Figure 91. Head for Culverts (Pipe W/ N =0.012) Flowing Full with Outlet Control... 446 Figure 92. Head for Culverts (Pipe W/ N =0.024) Flowing Full with Outlet Control... 447 Figure 93. Critical Depth of Flow for Circular Culverts... 448 Figure 94. Ditches Common Section... 453 Figure 95. Drainage Ditches Common Sections... 454 Figure 96. Geometric Elements of Common Sections... 455 Figure 97. Open Channel Flow Profile Computation... 459 Figure 98. Direct Step Backwater Method Example... 460 Figure 99. Mean Channel Velocity vs Medium Stone Weight (W50) and Equivalent Stone Diameter... 464 Figure 100. Riprap Gradation Curve... 465 Figure 101. Pipe/Culvert Outfall Discharge Protection... 469 Figure 102. Flow Dispersal Trench... 470 Figure 103. Alternative Flow Dispersal Trench... 471 Figure 104. Gabion Outfall Detail... 472 Figure 105. Diffuser TEE (an example of energy dissipating end feature)... 473 Figure 106. Pressure Wash Water Recovery System... 501 Figure 107. Drip Pan... 511 Figure 108. Drip Pan Within Rails... 512 Figure 109. Loading Dock with Door Skirt... 514 Figure 110. Loading Dock with Overhang... 514 Figure 111. Oil/Water Separator Layout... 516 Figure 112. Covered Fuel Island... 517 viii List of Figures
Figure 113. Surrounding Activities Containing Oversized Equipment... 520 Figure 114. Enclose the Activity... 545 Figure 115. Cover the Activity... 546 Figure 116. Covered Storage Area for Bulk Solids (including berm if needed)... 547 Figure 117. Material Covered with Plastic Sheeting... 548 Figure 118. Secondary Containment Vessel... 558 Figure 119. Locking System for Drum Lid... 559 Figure 120. Covered and Bermed Containment Area... 559 Figure 121. Mounted Container... 559 Figure 122. Above-Ground Tank Storage... 562 Figure 123. Hydrant Flushing... 595 Figure 124. Examples of Covered Activities... 601 Figure 125. Tarp Covering... 602 Figure 126. Paved Area with Sump Drain... 603 Figure 127. Above-Ground Tank with Impervious Walls and Floor... 605 Figure 128. Containment Types... 606 Figure 129. Standby Generator... 607 Figure 130. Flow Splitter, Option A... 656 Figure 131. Flow Splitter, Option B... 657 Figure 132. Flow Spreader Option A Anchored Plate... 659 Figure 133. Flow Spreader Option B Concrete Sump Box... 660 Figure 134. Flow Spreader Option C Notched Curb Spreader... 661 Figure 135. Flow Spreader Option D Through-Curb Ports... 662 Figure 136. Observation Well Details... 680 Figure 137. Sand Filtration Basin Preceded by Presettling Basin (Variation of a Basic Sand Filter)... 682 Figure 138. Sand Filter with a Pretreatment Cell (top view)... 683 Figure 139. Sand Filter with a Pretreatment Cell (side view)... 684 Figure 140. Sand Filter with Level Spreader (top view)... 685 Figure 141. Sand Filter with Level Spreader (side view)... 686 Figure 142. Sand Filter Vault (top view)... 693 Figure 143. Sand Filter Vault (side view)... 694 Figure 144. Linear Sand Filter... 696 Figure 145. Typical Swale Section... 698 Figure 146. Geometric Formulas for Common Swale Shapes... 699 Figure 147. The Relationship of Manning s n with VR for Various Degrees of Flow Retardance (A-E).. 705 Figure 148. Biofiltration Swale Underdrain Detail... 707 Figure 149. Biofiltration Swale Low-Flow Drain Detail... 707 Figure 150. Swale Dividing Berm... 708 Figure 151. Biofiltration Swale Access Features... 713 ix List of Figures
Figure 152. Typical Filter Strip... 718 Figure 153. Filter Strip Lengths for Narrow Right-of-Way... 721 Figure 154. Wetpond (top view)... 724 Figure 155. Wetpond (side view)... 725 Figure 156. Headwater Depth for Smooth Interior Pipe Culverts with Inlet Control... 728 Figure 157. Headwater Depth for Corrugated Pipe Culverts with Inlet Control... 729 Figure 158. Critical Depth of Flow for Circular Culverts... 730 Figure 159. Circular Channel Ratios... 731 Figure 160. Wetvault... 740 Figure 161. Stormwater Wetland Option 1... 748 Figure 162. Stormwater Wetland Option 2... 749 Figure 163. Combined Detention and Wetpond (top view)... 752 Figure 164. Combined Detention and Wetpond (side view)... 753 Figure 165. Alternative Configurations of Detention and Wetpool Areas... 755 Figure 166. API (Baffle Type) Separator... 758 Figure 167. Coalescing Plate Separator... 759 Figure 168. Spill Control Separator (not for oil treatment)... 760 Figure 169. Recommended Values of F for Various Values of v H /Vt... 777 Figure 170. Typical Dispersion Trench... 786 Figure 171. Standard Dispersion Trench with Notched Grade Board... 787 Figure 172. Typical Downspout Splashblock Dispersion... 788 Figure 173. Typical Concentrated Flow Dispersion for Steep Driveways... 790 Figure 174. Sheet Flow Dispersion for Driveways... 792 Figure 175. Threshold Discharge Area... 859 x List of Figures
Tables Table 1. Maintenance Standards... 70 Table 2. Water Quality Ranges Found in Study Wetlands... 117 Table 3. Temporary Erosion Control Seed Mix... 176 Table 4. Landscaping Seed Mix... 176 Table 5. Low-Growing Turf Seed Mix... 176 Table 6. Bioswale Seed Mix... 177 Table 7. Wet Area Seed Mix... 177 Table 8. Meadow Seed Mix... 177 Table 9. Mulch Standards and Guidelines... 179 Table 10. Materials on Hand... 203 Table 11. Storm Drain Inlet Protection... 249 Table 12. Geotextile Standards... 262 Table 13. Vegetated Strips... 268 Table 14. Sediment Trap Sizing... 274 Table 15. Sediment Trap Sizing... 313 Table 16. Temporary Erosion Control Seed Mix... 316 Table 17. Mulch Standards and Guidelines... 317 Table 18. BMP Designs in Western Washington... 336 Table 19. Runoff Curve Numbers for Selected Agricultural, Suburban and Urban Areas... 339 Table 20. Bioretention Soil Mix Aggregate Component... 351 Table 21. Sizing Table for Rain Gardens... 353 Table 22. Modeling Assumptions for Rain Garden Sizing... 354 Table 23. Infiltration Rate Reduction Factors to Account for Biofouling and Siltation Effects for Ponds.. 362 Table 24. Recommended Infiltration Rates based on USDA Soil Textural Classification... 368 Table 25. Alternative Recommended Infiltration Rates Based on ASTM Gradation Testing... 369 Table 26. Correction Factors to be Used with In-Situ Infiltration Measurements to Estimate Long-Term Design Infiltration Rates... 370 Table 27. Permanent Surface Water Control Pond Sign Specifications... 388 Table 28. Small Trees and Shrubs with Fibrous Roots... 390 Table 29. Values of C d for Sutro Weirs... 404 Table 30. Runoff Coefficients C Values for the Rational Method... 416 Table 31. Coefficients for the Rational Method... 417 Table 32. Rainfall Intensities for the City of Tacoma... 418 Table 33. n and k Values Used in Time Calculations for Hydrographs... 420 Table 34. Percentage Impervious for Modeling Fully Developed Conditions... 422 Table 35. Manning s n Values for Pipes... 424 Table 36. Backwater Calculation Sheet Notes... 428 xi List of Tables
Table 37. Maximum Pipe Slopes, Velocities and Anchor Requirements... 433 Table 38. Allowable Structures and Pipe Sizes... 434 Table 39. Constants for Inlet Control Equations... 443 Table 40. Entrance Loss Coefficients... 449 Table 41. Values of the Roughness Coefficient n... 456 Table 42. Channel Protection... 457 Table 43. Rock Protection at Outfalls... 466 Table 44. Additional Storm Drain Easement Widths... 477 Table 45. Design Storm Precipitation Values... 479 Table 46. Uncovered Fuel Island Separator Sizing Requirements... 518 Table 47. Typical TPH Levels in Street Sweeping and Catch Basin Solids... 628 Table 48. Typical c-pah Values in Street Waste Solids and Related Materials... 628 Table 49. Typical Metals Concentrations in Catch Basin Sediments... 629 Table 50. Recommended Parameters & Suggested Values for Determining Reuse & Disposal Options... 630 Table 51. Recommended Sampling Frequency for Street Waste Solids... 631 Table 52. Pollutants in Catch Basin Solids Comparison to Dangerous Waste Criteria... 631 Table 53. Typical Catch Basin Decant Values Compared to Surface Water Quality Criteria... 632 Table 54. Typical Values for Conventional Pollutants in Catch Basin Decant... 632 Table 55. Catch Basin Decant Values Following Settling 1... 633 Table 56. Screening Treatment Facilities Based on Soil Type... 641 Table 57. Treatment Trains for Phosphorus Removal... 644 Table 58. Treatment Trains for Enhanced Treatment... 645 Table 59. Treatment Facility Placement in Relation to Detention Facilities... 649 Table 60. Lining Types Recommended for Runoff Treatment Facilities... 652 Table 61. Acceptable Gradation for Compacted Till Liners... 654 Table 62. Sand Specifications... 689 Table 63. Clay Liner Specifications... 689 Table 64. Sizing Criteria... 700 Table 65. Stability Check Steps (SC) Guide for Selecting Degree of Retardance... 704 Table 66. Guide to Selecting Maximum Permissible Swale Velocities for Stability*... 705 Table 67. Grass Seed Mixes Suitable for Biofiltration Swale Treatment Areas... 710 Table 68. Groundcovers & Grasses Suitable for the Upper Side Slopes of a Biofiltration Swale in Western Washington... 711 Table 69. Recommended Plants for Wet Biofiltration Swale... 712 Table 70. Emergent Wetland Species Recommended for Wetponds... 737 Table 71. Distribution of Depths in Wetland Cell... 750 Table 72. Correction Factors to be Used with In-Situ Infiltration Measurements to Estimate Long-Term Design Infiltration Rates... 774 Table 73. Geotextile Properties for Underground Drainage... 775 xii List of Tables
Table 74. Geotextile for Underground Drainage Filtration Properties... 775 Table 75. Geotextile Strength Properties for Impermeable Liner Protection... 776 Table 76. Bioretention Soil Mix Aggregate Component... 804 Table 77. Sizing Table for Rain Gardens... 807 Table 78. Modeling Assumptions for Rain Garden Sizing... 808 xiii List of Tables
xiv List of Tables