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Pennsylvania Stormwater
Best Management Practices
Manual
DRAFT - JANUARY 2005
Prepared For:
Department of Environmental Protection
Bureau of Stormwater Management
Division of Waterways, Wetlands and Erosion Control
Table of Contents
Pennsylvania Stormwater
Best Management Practices
Manual
2ND Draft - JANUARY 2005
Under Contract No. 2003-WWEC-1
Prepared By:
Cahill Associates Inc.
104 S. High Street
West Chester, PA 19382
(610) 696-4150
With assistance from:
Amy Green Associates
Flemington, NJ
GeoSyntec Consultants
Boxborough, MA
Low Impact Development Center, Inc.
Rockville, MD
Pennsylvania Environmental Council
Philadelphia, Harrisburg, Pittsburgh, PA
RoofScapes, Inc.
Philadelphia, PA
ii Draft Pennsylvania Stormwater Management Manual
Table of Contents
Table of Contents
Section 1 Introduction and Purpose of Stormwater BMP Manual ............................. 1
1.1 Introduction and Purpose of This Manual .............................................................................. 4
1.2 A Brief Review of Stormwater Problems in Pennsylvania ..................................................... 6
1.3 The Existing Stormwater Management System in Pennsylvania: Overview ........................ 8
1.4 Recent Changes to Pennsylvania’s Stormwater Management System ................................ 9
Section 2 Stormwater and Pennsylvania’s Natural Systems ................................... 15
2.1 The Hydrologic Cycle ........................................................................................................... 18
2.1.1 Precipitation ....................................................................................................... 19
2.1.2 Infiltration ............................................................................................................ 22
2.1.3 Evapotranspiration ............................................................................................. 22
2.1.4 Groundwater Recharge and Stream Base Flow ................................................ 24
2.1.5 Surface Runoff ................................................................................................... 25
2.2 Hydrologic Impacts of Development and Impervious Surfaces ........................................... 26
2.3 Stormwater Management ..................................................................................................... 30
2.4 Stormwater and Water Quality ............................................................................................. 35
2.5 Major Watersheds and Stream Systems ............................................................................. 41
2.6 Important Natural Systems of Pennsylvania........................................................................ 43
2.6.2 Soils .................................................................................................................... 47
2.6.3 Vegetation .......................................................................................................... 50
2.6.4 Physiography ..................................................................................................... 52
2.7 References ........................................................................................................................... 55
Section 3 Stormwater Management Principles, Goals, and a Management Model 59
3.1 Introduction .......................................................................................................................... 62
3.2 Recommended Site Control Guidelines .............................................................................. 62
3.2.1 Recommended Volume Control Guideline ........................................................ 64
3.2.2 Extended Detention (CG-2 only) ........................................................................ 72
3.2.3 Recommended Peak Rate Control Guideline (CG-1 and CG-2) ....................... 72
3.2.4 Recommended Water Quality Control Guideline (CG-1 and CG-2) .................. 73
3.3 Stormwater Standards for Special Areas ............................................................................. 74
3.4 Boiling it Down: Top Ten Principles for Stormwater Management in Pennsylvania ............ 75
Section 4 Comprehensive Stormwater Management: Integrating Site Design, Non-
Structural, and Structural BMP's ............................................................... 77
4.1 Recommended Site Design Procedure for Comprehensive Stormwater Management ...... 80
4.2 The Site Design Checklist for Comprehensive Stormwater Management .......................... 82
4.3 Importance of Site Assessment ........................................................................................... 86
4.3.1. Background Site Factors .................................................................................... 86
4.3.2. Site Factors Inventory ........................................................................................ 87
4.3.3. Site Factors Analysis .......................................................................................... 87
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Table of Contents
Section 5 Comprehensive Stormwater Management: Non-Structural BMP's ........ 91
5.1 Introduction .......................................................................................................................... 94
5.2 Non-Structural Best Management Practices........................................................................ 94
5.3 Non-Structural BMP’s and Stormwater Methodological Issues ........................................... 96
5.4 Protect Sensitive and Special Value Resources.................................................................. 97
BMP 5.1: Protect Sensitive and Special Value Features ................................................... 99
BMP 5.2: Protect/Conserve/Enhance Riparian Areas ..................................................... 105
BMP 5.3: Protect/Utilize Natural Flow Pathways in Overall Stormwater Planning and
Design ............................................................................................................... 113
5.5 Cluster and Concentrate .....................................................................................................119
BMP 5.4: Cluster Uses at Each Site; Build on the Smallest Area Possible ..................... 121
BMP 5.5: Concentrate Uses Areawide through Smart Growth Practices ........................ 129
5.6 Minimize Disturbance and Minimize Maintenance............................................................. 141
BMP 5.6: Minimize Total Disturbed Area – Grading ........................................................ 143
BMP 5.7: Minimize Soil Compaction in Disturbed Areas ................................................. 150
BMP 5.8: Re-Vegetate and Re-Forest Disturbed Areas, Using Native Species .............. 156
5.7 Reduce Impervious Cover ................................................................................................. 163
BMP 5.9: Reduce Street Imperviousness ........................................................................ 165
BMP 5.10: Reduce Parking Imperviousness ..................................................................... 171
5.8 Disconnect / Distribute / Decentralize ................................................................................ 177
BMP 5.11: Rooftop Disconnection ..................................................................................... 179
BMP 5.12: Disconnection from Storm Sewers ................................................................... 183
5.9 Source Control ................................................................................................................... 187
BMP 5.13: Streetsweeping................................................................................................. 189
Section 6 Comprehensive Stormwater Management: Structural BMPs ............... 195
6.1 Introduction ........................................................................................................................ 198
6.2 Groupings of Structural BMPs ........................................................................................... 198
6.3 Manufactured Products ...................................................................................................... 199
6.4 Volume/Peak Rate Reduction by Infiltration BMPs ........................................................... 201
BMP 6.1: Porous Pavement with Infiltration Bed ............................................................. 203
BMP 6.2: Infiltration Basin ................................................................................................ 225
BMP 6.3: Subsurface Infiltration Bed ............................................................................... 233
BMP 6.4: Infiltration Trench .............................................................................................. 243
BMP 6.5: Rain Garden/Bioretention ................................................................................ 253
BMP 6.6: Dry Well / Seepage Pit ..................................................................................... 269
BMP 6.7: Constructed Filter ............................................................................................. 277
BMP 6.8: Vegetated Swale .............................................................................................. 289
BMP 6.9: Vegetated Filter Strip ........................................................................................ 309
BMP 6.10: Infiltration Berm & Retentive Grading .............................................................. 325
6.5 Volume/Peak Rate Reduction BMPs ................................................................................. 337
BMP 6.11: Vegetated Roof ................................................................................................ 339
BMP 6.12: Rooftop Runoff - Capture & Reuse ................................................................. 353
6.6 Runoff Quality/Peak Rate BMPs ....................................................................................... 363
BMP 6.13: Constructed Wetland ....................................................................................... 365
iv Draft Pennsylvania Stormwater Management Manual
Table of Contents
BMP 6.14: Wet Pond/Retention Basin .............................................................................. 377
BMP 6.15: Dry Extended Detention Basin ........................................................................ 389
BMP 6.16: Water Quality Filter .......................................................................................... 401
6.7 Restoration BMPs .............................................................................................................. 409
BMP 6.17: Riparian Buffer Restoration .............................................................................. 411
BMP 6.18: Landscape Restoration .................................................................................... 431
BMP 6.19: Soil Amendment & Restoration ........................................................................ 443
6.8 Other BMPs and Related Structural Measures.................................................................. 453
BMP 6.20: Level Spreader ................................................................................................. 455
BMP 6.21: Special Detention Areas - Parking Lot, Rooftop .............................................. 469
6.9 Protocols for Structural BMPs ............................................................................................ 475
Protocol 1: Infiltration Systems Guidelines ....................................................................... 477
Protocol 2. Soil Evaluation and Investigation for Infiltration BMP’s .................................. 485
Section 7 Stormwater Management for Urban Areas ............................................. 495
7.1 Introduction ........................................................................................................................ 498
7.2 Urban Water Quality .......................................................................................................... 499
7.3 Urban Land Characteristics That Influence Stormwater Management ............................. 500
7.4 Stormwater Control Guidelines and Urban Areas .............................................................. 505
7.5 Water Quality Issues in Urban Areas ................................................................................. 505
7.6 BMP Selection and Suitability for Urban Areas ................................................................. 506
Case Study 1: Sadie Tanner Mossell Alexander, University of Pennsylvania Partnership School 509
Case Study 2: Fencing Academy of Philadelphia ......................................................................... 510
Case Study 3: Department of Environmental Protection Southeast Regional Office .................... 511
Case Study 4: Ford Motor Company Rouge River Manufacturing Plant ...................................... 512
7.8 References ......................................................................................................................... 513
Section 8 Special Stormwater Management for Highways and Roads ................. 515
8.1 Introduction ........................................................................................................................ 518
8.2 Roadway Runoff Quality Issues ........................................................................................ 519
8.3 BMP Considerations for Roadways ................................................................................... 520
8.4 Specific BMP Considerations ............................................................................................. 524
8.4.1 Limited Access Highways, Interstates and Turnpikes (Principal Arterials) ...... 524
8.4.2 New Streets and Residential Roads ................................................................ 524
8.5 Gravel Roads ..................................................................................................................... 525
8.6 References ......................................................................................................................... 527
Section 9 531
Stormwater Calculations and Methodology ................................................................ 531
9.1 Introduction to Stormwater Methodologies ........................................................................ 534
9.2 Existing Methodologies for Runoff Volume Calculations and their Limitations ................. 534
9.2.1 Runoff Curve Number Method ......................................................................... 534
9.2.2 Small Storm Hydrology Method ....................................................................... 535
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Table of Contents
9.2.3 Infiltration Models for Runoff Calculations ....................................................... 536
9.3 Existing Methodologies for Peak Rate/Hydrograph Estimations and their Limitations ..... 537
9.3.1 The Rational Method ........................................................................................ 537
9.3.2 Modified Rational Method ................................................................................ 537
9.3.3 SCS (NRCS) Unit Hydrograph Method ............................................................ 537
9.4 Computer Models ............................................................................................................... 538
9.4.1 HEC Hydrologic Modeling System (HEC-HMS) ............................................... 538
9.4.2 SCS/NRCS Models: TR-20 and TR-55 ............................................................ 538
9.4.3 Storm Water Management Model (SWMM) ..................................................... 538
9.5 Precipitation Data for Stormwater Calculations ................................................................. 539
9.6 Water Quality ..................................................................................................................... 540
9.6.1 Analysis of Water Quality Impacts from Developed Land .............................. 541
9.6.2 Analysis of Water Quality Benefits from BMPs ............................................... 543
9.6.3 Water Quality Analysis ..................................................................................... 545
9.7 Guidance for Stormwater Calculations for CG1 and CG2 ................................................. 546
9.7.1 Stormwater Calculation Process ...................................................................... 546
9.8 Non-structural BMP Credits ............................................................................................... 549
9.8 References and Additional Information Sources ............................................................... 578
Section 10 Case Studies: Innovative Stormwater Management Approaches and
Practices .................................................................................................... 581
10.1 Introduction ........................................................................................................................ 584
10.2 Outline of Information Needed for Case Studies ............................................................... 585
10.3 Case Studies ...................................................................................................................... 586
Case Study 1: Penn State University - Centre County Visitor Center, Centre County ................ 586
Case Study 2: Dennis Creek Streambank Restoration, Franklin County ..................................... 594
Case Study 3: Commerce Plaza III, Lehigh County
Case Study 4: Flying J. Truck Plaza for Welsh Oil of Indiana Truck Refueling Terminal ............. 598
Case Study 5: Ephrata Performing Arts Center ............................................................................ 602
Case Study 6: Lebanon Valley Agricultural Center ...................................................................... 604
Case Study 7: Penn State University Berks County Campus ...................................................... 605
Case Study 8: Warm Season Meadows at Williams Transco ..................................................... 608
Case Study 9: Hills of Sullivan Residential Subdivision ............................................................... 610
Case Study 10: Applebrook Golf Course Community .................................................................. 613
Case Study 11: Swan Lake Drive Development ........................................................................... 616
vi Draft Pennsylvania Stormwater Management Manual
Table of Contents
Draft Pennsylvania Stormwater Management Manual vii
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