- Introduction
- Ch. 1 Stormwater Management Requirements
- Ch. 2 Submission, Review, and Approval Procedures
- Ch. 3 Site Design and Stormwater Management Integration
- Ch. 4 Stormwater Management Practice Guidance
- Ch. 5 Construction Guidance
- Ch. 6 Post-Construction and Operations and Maintenance Guidance
- Appendices
- Download
- Back to Chapters
- Manual Organization and Purpose
- Stormwater Regulations
- Private Development Services
- Stormwater Billing and Incentives
- Stormwater Management in Philadelphia
- Applicability and Submission Process
- Preferred Design Approach
- Back to Chapters
- 1.0 Introduction
- 1.1 Applicability Factors
- 1.2 Stormwater Regulations
- 1.3 Stormwater Retrofits
- Back to Chapter 1
- 1.2.1 Post-Construction Stormwater Management Requirements
- 1.2.2 Erosion and Sediment Control Requirement
- Back to Chapter 1
- 1.3.1 Retrofit Project Applicability and Initiation
- 1.3.2 Retrofit Project Requirements and Guidance
- Back to Chapters
- 2.0 Introduction
- 2.1 Existing Resources and Site Analysis
- 2.2 Review Paths
- 2.3 Review Phases
- 2.4 Expedited Post-Construction Stormwater Management Plan Reviews
- 2.5 PWD’s Development Review Process
- 2.6 PWD’s Role in Philadelphia's Development Process
- 2.7 PWD and Pennsylvania Department of Environmental Protection
- Back to Chapter 2
- 2.2.1 Development Compliance Review Path
- 2.2.2 Development Exemption Review Path
- 2.2.3 Demolition Review Path
- 2.2.4 Stormwater Retrofit Review Path
- Back to Chapter 2
- 2.3.1 Development Compliance Review Path
- 2.3.2 Development Exemption Review Path
- 2.3.3 Demolition Review Path
- 2.3.4 Stormwater Retrofit Review Path
- Back to Chapter 2
- 2.4.1 Disconnection Green Review
- 2.4.2 Surface Green Review
- 2.4.3 Expedited PCSMP Review Process
- Back to Chapter 2
- 2.7.1 National Pollutant Discharge Elimination System Permits
- 2.7.2 Other PA DEP Requirements
- Back to Chapters
- 3.0 Introduction
- 3.1 Site Assessment and Stormwater Management Strategies
- 3.2 Stormwater Management Design
- 3.3 Infiltration Testing and Soil Assessment for SMP Design
- 3.4 How To Show Compliance
- 3.5 Integrated Stormwater Management Examples
- Back to Chapter 3
- 3.0.1 How to Use This Chapter
- 3.0.2 Integrated Site and Stormwater Management Assessment and Design Process Overview
- 3.0.3 Interactions between Design Strategies, Stormwater Regulations, and Review Paths
- Back to Chapter 3
- 3.1.1 Background Site Factors and Site Factors Inventory
- 3.1.2 Site Factors Analysis
- 3.1.3 Integrated Design Approach
- 3.1.4 Non-Structural Design
- 3.1.5 Disconnected Impervious Cover
- 3.1.6 SMP Functions
- 3.1.7 Pollutant- Reducing Practices and Roof Runoff Isolation
- 3.1.8 How to Use SMPs to Comply with the Regulations
- Back to Chapter 3
- 3.2.1 Major SMP Types
- 3.2.2 SMP Hierarchy and Selection Process
- 3.2.3 Placing SMPs in Series
- 3.2.4 Stormwater Management Banking and Trading
- 3.2.5 SMP Design Guidance and General Requirements
- 3.2.6 Loading Ratio Requirements
- 3.2.7 Planting and Vegetation Guidance
- 3.2.8 Operations and Maintenance
- Back to Chapter 3
- 3.3.1 Infiltration Testing and Soil Characterization Plan Development
- 3.3.2 Soil Characterization Requirements
- 3.3.3 Infiltration Testing Requirements
- 3.3.4 Soil Characterization Procedures
- 3.3.5 Infiltration Testing Procedures
- 3.3.6 Evaluation of Infiltration Testing Results
- Back to Chapter 3
- 3.4.1 Regulatory Compliance Documentation Requirements
- 3.4.2 Storm Sewer Design Requirements
- 3.4.3 Calculation Methods and Design Tools
- Back to Chapter 3
- 3.5.1 Commercial Office Building Development
- 3.5.2 Residential Multi-Family Development
- 3.5.3 Full Build-Out
- 3.5.4 Trails
- 3.5.5 Athletic Fields
- 3.5.6 Streets
- Back to Chapters
- 4.0 Introduction
- 4.1 Bioinfiltration/ Bioretention
- 4.2 Porous Pavement
- 4.3 Green Roofs
- 4.4 Subsurface Infiltration
- 4.5 Cisterns
- 4.6 Blue Roofs
- 4.7 Ponds and Wet Basins
- 4.8 Subsurface Detention
- 4.9 Media Filters
- 4.10 Pretreatment
- 4.11 Inlet Controls
- 4.12 Outlet Controls
- Back to Chapter 4
- 4.1.1 Bioinfiltration/ Bioretention Introduction
- 4.1.2 Bioinfiltration/ Bioretention Components
- 4.1.3 Bioinfiltration/ Bioretention Design Standards
- 4.1.4 Bioinfiltration/ Bioretention Material Standards
- 4.1.5 Bioinfiltration/ Bioretention Construction Guidance
- 4.1.6 Bioinfiltration/ Bioretention Maintenance Guidance
- Back to Chapter 4
- 4.2.1 Porous Pavement Introduction
- 4.2.2 Porous Pavement Components
- 4.2.3 Porous Pavement Design Standards
- 4.2.4 Porous Pavement Material Standards
- 4.2.5 Porous Pavement Construction Guidance
- 4.2.6 Porous Pavement Maintenance Guidance
- Back to Chapter 4
- 4.3.1 Green Roof Introduction
- 4.3.2 Green Roof Components
- 4.3.3 Green Roof Design Standards
- 4.3.4 Green Roof Material Standards
- 4.3.5 Green Roof Construction Guidance
- 4.3.6 Green Roof Maintenance Guidance
- Back to Chapter 4
- 4.4.1 Subsurface Infiltration Introduction
- 4.4.2 Subsurface Infiltration Components
- 4.4.3 Subsurface Infiltration Design Standards
- 4.4.4 Subsurface Infiltration Material Standards
- 4.4.5 Subsurface Infiltration Construction Guidance
- 4.4.6 Subsurface Infiltration Maintenance Guidance
- Back to Chapter 4
- 4.5.1 Cistern Introduction
- 4.5.2 Cistern Components
- 4.5.3 Cistern Design Standards
- 4.5.4 Cistern Material Standards
- 4.5.5 Cistern Construction Guidance
- 4.5.6 Cistern Maintenance Guidance
- Back to Chapter 4
- 4.6.1 Blue Roof Introduction
- 4.6.2 Blue Roof Components
- 4.6.3 Blue Roof Design Standards
- 4.6.4 Blue Roof Material Standards
- 4.6.5 Blue Roof Construction Guidance
- 4.6.6 Blue Roof Maintenance Guidance
- Back to Chapter 4
- 4.7.1 Pond and Wet Basin Introduction
- 4.7.2 Pond and Wet Basin Components
- 4.7.3 Pond and Wet Basin Design Standards
- 4.7.4 Pond and Wet Basin Material Standards
- 4.7.5 Pond and Wet Basin Construction Guidance
- 4.7.6 Pond and Wet Basin Maintenance Guidance
- Back to Chapter 4
- 4.8.1 Subsurface Detention Introduction
- 4.8.2 Subsurface Detention Components
- 4.8.3 Subsurface Detention Design Standards
- 4.8.4 Subsurface Detention Material Standards
- 4.8.5 Subsurface Detention Construction Guidance
- 4.8.6 Subsurface Detention Maintenance Guidance
- Back to Chapter 4
- 4.9.1 Media Filter Introduction
- 4.9.2 Media Filter Components
- 4.9.3 Media Filter Design Standards
- 4.9.4 Media Filter Material Standards
- 4.9.5 Media Filter Construction Guidance
- 4.9.6 Media Filter Maintenance Guidance
- Back to Chapter 4
- 4.10.1 Pretreatment Introduction
- 4.10.2 Filter Strips
- 4.10.3 Forebays
- 4.10.4 Swales
- Back to Chapter 4
- 4.11.1 Inlet Control Introduction
- 4.11.2 Flow Splitters
- 4.11.3 Curbless Design/Curb Openings
- 4.11.4 Energy Dissipaters
- 4.11.5 Inlets
- Back to Chapter 4
- 4.12.1 Outlet Control Introduction
- 4.12.2 Orifices
- 4.12.3 Weirs
- 4.12.4 Risers
- 4.12.5 Underdrains
- 4.12.6 Level Spreaders
- 4.12.7 Impervious Liners
- 4.12.8 Micro Siphon Drain Belts
- 4.12.9 Low Flow Devices
- Back to Chapters
- 5.0 Introduction
- 5.1 Construction Inspection
- 5.2 Common Construction Issues
- 5.3 Construction Documentation
- Back to Chapter 5
- 5.1.1 Coordinating Inspections with Other PWD Units
- 5.1.2 Preconstruction Processes
- 5.1.3 Construction Processes
- 5.1.4 Final Inspection
- 5.1.5 Post-Construction Submissions
- Back to Chapter 5
- 5.2.1 Erosion and Sediment-Related Construction Issues
- 5.2.2 Stormwater Management Practice-Related Construction Issues
- Back to Chapters
- 6.0 Introduction
- 6.1 Operations and Maintenance
- 6.2 Stormwater Management Practice Inspection Guidance
- 6.3 Stormwater Credits Program
- Back to Chapter 6
- 6.1.1 Maintenance Requirements for Property Owners
- 6.1.2 Operations and Maintenance Agreements
- Back to Chapters
- Appendix Index
- A. Glossary
- B. Abbreviations
- C. PWD Stormwater Regulations
- D. Watershed Maps
- E. Plan and Report Checklists
- F. Design Guidance Checklists
- G. SMP Maintenance Guide Documents
- H. Infiltration Testing Log
- I. Landscape Guidance
- J. Construction Certification Package
- K. Record Drawing Sample
- L. Standard Details
- Back to Appendices
- Table E-1: General Plan Sheet Requirements
- Table E-2: Existing Conditions Plan Requirements
- Table E-3: Conceptual Stormwater Management Plan Requirements
- Table E-4: Erosion and Sediment Control Plan Requirements
- Table E-5: Standard Erosion and Sediment Control Notes
- Table E-6: Standard Sequence of Construction Notes
- Table E-7: Post-Construction Stormwater Management Plan Report Requirements
- Table E-8: Record Drawing Requirements
- Back to Appendices
- F.1 Stormwater Regulation Compliance
- F.2 Post-Construction Stormwater Management Plan
- F.3 Erosion and Sediment Control
- F.4 Disconnected Impervious Cover
- F.5 Infiltration Testing and Soil Assessment
- F.6 Hydrologic Model and Calculation Methods
- F.7 Bioinfiltration/ Bioretention
- F.8 Porous Pavement
- F.9 Green Roofs
- F.10 Subsurface Infiltration
- F.11 Cisterns
- F.12 Blue Roofs
- F.13 Ponds and Wet Basins
- F.14 Subsurface Detention
- F.15 Media Filters
- F.16 Pretreatment
- F.17 Inlet Controls
- F.18 Outlet Controls
F.16 Pretreatment
F.16.1 Filter Strip Design and Material Standards
- Verify that the plans include an appropriate sequence of construction that is specific to the construction of the filter strip. Refer to Section 4.10.2 for guidance. [Section 2.3.1]
- If discharge of concentrated flow to the filter strip is proposed, verify that a level spreading device is proposed to provide uniform sheet flow. [Section 4.10.2, 2]
- If filter strips are proposed in high-use areas, verify that precautions are taken to minimize disturbance of the filter strip, such as signage fences, and placement of sidewalks or paths to minimize pedestrian or vehicular traffic. [Section 4.10.2, 3]
- If energy dissipaters and/or flow spreaders are not proposed to be installed with the filter strip, verify that the flow path to the filter strip does not exceed 75 feet for impervious ground cover or 150 feet for pervious ground cover. [Section 4.10.2, 4]
- Verify that the contributing drainage area does not exceed five acres and does not exceed a drainage area to filter strip area ratio of 6:1. [Section 4.10.2, 5]
- If no energy dissipaters and/or flow spreaders are provided up-gradient of the filter strip, verify that the slope of the contributing drainage area to the filter strip does not exceed 5%. [Section 4.10.2, 6]
- Verify that the slope of the filter strip does not exceed 8%. Slopes less than 5% are generally preferred. Filter strips with slopes that exceed 5% should implement check dams to encourage ponding and prevent scour and erosion of the filter strip area. [Section 4.10.2, 7]
- Verify that the slope (parallel to the flow path) of the top of the filter strip, after a flow spreading device, is less than 1% and gradually increases to the designed value to protect from erosion and undermining of the device. [Section 4.10.2, 8]
- Verify that the plans indicate that plants must be established at the time of filter strip completion (at least three months after seeding), and that runoff must not be allowed to flow across the filter strip until the vegetation is established. [Section 4.10.2, 9]
- Verify that the filter strip length is in accordance with Table 4.10-2 of the Manual. [Section 4.10.2, 10]
- For contributing flow paths less than 30 feet in length, verify that the filter strip length is in accordance with Figure 4.10-1 of the Manual. [Section 4.10.2, 11]
- For contributing flow paths greater than 30 feet in length, verify that the filter strip meets the required flow characteristics for maximum velocity and depth listed in Table 4.10-3 of the Manual. [Section 4.10.2, 12]
F.16.2 Forebay Design and Material Standards
- Verify that the plans include an appropriate sequence of construction that is specific to the construction of the forebay. Refer to Section 4.10.3 for guidance. [Section 2.3.1]
- For forebays within large SMPs such as ponds and wet basins, verify that the forebay contains 10% to 15% of the total permanent pool volume of the larger SMP. [Section 4.10.3, 1]
- For forebays within smaller SMPs such as bioinfiltration/bioretention basins, verify that the storage volume is sized to retain 0.25 inches of runoff per acre of contributing directly connected impervious area (DCIA), with an absolute minimum of 0.1 inch per impervious acre. [Section 4.10.3, 2]
- Verify that the plans include a stone berm to physically separate the forebay from its associated SMP. The berm should span the entire width of the basin. [Section 4.10.3, 3]
- Verify that the plans include inlet controls for the forebay, including riprap aprons, stone placed in concrete, or some other type of energy dissipation device to rapidly reduce the inflow velocity for erosion/scour protection and to encourage settlement of suspended solids. [Section 4.10.3, 4]
- Verify that the plans indicate that permanent vertical markers constructed of durable materials are to be installed within the forebay area to indicate the sediment depth. [Section 4.10.3, 5]
- Verify that adequate inspection and maintenance access is provided to allow for periodic sediment removal; this is most commonly provided via stabilized and mildly sloping graded areas that can be accessed by heavy equipment. [Section 4.10.3, 6]
- Verify that exit velocities from the forebay are non-erosive. Refer to the latest edition of the Pennsylvania Department of Environmental Protection (PA DEP) Erosion and Sediment Pollution Control Program Manual for information on design standards for erosion and sedimentation control practices. [Section 4.10.3, 7]
F.16.3 Swale Design and Material Standards
- Verify that the plans include an appropriate sequence of construction that is specific to the construction of the swale. Refer to Section 4.10.4 for guidance. [Section 2.3.1]
- If a swale is designed as a primary SMP, verify that the swale meets all Design Guidance Checklist design standards noted in Appendix F.7, Bioinfiltration/Bioretention, as well as all applicable swale Design Guidance Checklist design standards below. [Section 4.10.4, 1]
- Verify that the swale can convey the ten-year, 24-hour storm event with a minimum of six inches of freeboard and a maximum depth of 18 inches. Flow over check dams may be estimated using a weir equation. [Section 4.10.4, 2]
- Verify that the swale is designed to resist erosion. It is recommended that the swale convey the two-year, 24-hour storm event without erosion. The latest edition of the PA DEP Erosion and Sediment Pollution Control Program Manual is recommended as a reference for these calculations. Verify that soil mix, vegetation, and temporary or permanent stabilization measures are adjusted as needed. [Section 4.10.4, 3]
- Verify that the plans indicate that plants must be established at the time of swale completion (at least three months after seeding). [Section 4.10.4, 4]
- Verify that energy dissipaters are provided at points of concentrated inflow into the swale. [Section 4.10.4, 5]
- Verify that the side slopes for all parabolic channel swales do not exceed 2(H):1(V) (the recommended side slope is 3(H):1(V)), and that the side slopes of all mowed areas do not exceed 4(H): 1(V) to avoid “scalping” by mower blades. [Section 4.10.4, 7]
- Verify that check dams intended to provide ponding in swale SMP designs are not porous, as water should be ponded behind each check dam and forced to infiltrate. If the swales are only being used for conveyance or to increase time of concentration, etc., check dams may be porous. [Section 4.10.4, 8]