- 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.6 Hydrologic Model and Calculation Methods
F.6.1 Hydrologic Model
- Verify that all DCIA within the project’s limits of earth disturbance is routed to an SMP. [Section 1.2.1; Section 3.4.1]
- Verify that the modeled drainage areas are accurate and consistent with the plans’ drainage areas. [Section 3.4.1]
- Verify that all SMP bypass areas within the project’s limit of earth disturbance are accounted for in the hydrologic calculations’ stormwater model. [Section 3.4.1]
- Verify that the links are correct. A point of analysis (POA) must be determined for comparison of the predevelopment and post-development conditions. A POA may serve one or several drainage areas and/or SMPs. Multiple POAs must be identified for project sites with multiple points of discharge. Points of analysis should only be linked when they drain to the same sewershed or waterway. [Section 3.4.1]
- Verify that the routing of devices within the stormwater model is provided and consistent with the plan’s proposed design. [Section 3.4.1]
- Verify that the stormwater outlet controls configuration is correct and consistent with the plans. [Section 3.4.1]
- Verify that runoff from pervious and impervious areas is calculated separately. Weighted curve number values between pervious and impervious areas are not acceptable. [Section 3.4.3]
- Verify that the precipitation depths used for all design storm events are in accordance with the design rainfall data listed below, pursuant to PennDOT Drainage Manual, Chapter 7, Appendix A, Field Manual For Pennsylvania Design Rainfall Intensity Charts From NOAA Atlas 14 Version 3 Data (2010 or latest). [Section 3.4.3]
Design Precipitation Depth (inches) | |||||||
---|---|---|---|---|---|---|---|
Duration | 1-year | 2-year | 5-year | 10-year | 25-year | 50-year | 100-year |
24 hours | 2.83 | 3.40 | 4.22 | 4.95 | 6.10 | 7.16 | 8.43 |
- Verify that the Manning’s n values used within the stormwater model are correct and consistent with the plans’ proposed pipe material. A Manning’s n value of 0.013 must be used for RCP, VCP, and CIP, and a value of 0.011 must be used for PVC and HDPE. [Section 3.4.3]
- Verify that the stormwater model uses the minimum time step allowable by the implemented hydrologic software (which is 0.01 hours in HydroCAD and 1 minute in Hydraflow or a maximum of 0.01 hours. [Section 3.4.3]
- Verify that the SMP storage provided is correct and consistent with the plans. A porosity of 0.20 for soil media, 0.30 for sand, and 0.40 for stone must be used. [Chapter 4]
F.6.2 Runoff Estimation
- Verify that the appropriate NRCS Curve Number Method curve number values are used in the runoff estimation calculations. Refer to Table 3.4-2 of the Manual. [Section 3.4.1; Section 3.4.3]
- When performing Water Quality slow release rate calculations for a project in a combined sewer area for which infiltration is not feasible, verify that a curve number of 98 is used with a precipitation depth of 1.7 inches when routing the Water Quality storm event. [Section 3.4.1]
- When performing Flood Control calculations, verify that all non-forested pervious areas are considered meadow in good condition for predevelopment runoff calculations. Non-forested pervious area consists of the following cover types: meadow, grass/lawn, brush, gravel, dirt, porous pavements, and any combination of these cover types. [Section 3.4.1]
- When performing Flood Control calculations for a Redevelopment project, verify that, in addition to any other pervious area, 20% of the existing impervious cover, when present, is considered meadow (good condition) for the predevelopment runoff calculations. [Section 3.4.1]
F.6.3 Flow Routing
- Verify that time of concentration calculations are provided for all predevelopment areas. [Section 3.4.1]
- Verify that the time of concentration paths are shown on the drainage area maps and are labeled with slopes, cover types, and lengths for each type of flow (sheet, shallow concentrated, etc.). [Section 3.4.1; Appendix E, Table E-7]
- Verify that the time of concentration paths are shown from the hydraulically most distant point of the drainage area to a point of interest within the drainage area, and that the paths are perpendicular to each area’s contours. [Section 3.4.3]
- Verify that the minimum post-development time of concentration used for any path is six minutes. [Section 3.4.1; Section 3.4.3]
- Verify that the correct two-year design precipitation depth (P-2) is used in the sheet flow component of the time of concentration calculations. [Section 3.4.3]
- Verify that the correct Manning’s n values (roughness coefficients) are used in the sheet flow component of the time of concentration calculations. Refer to Table 3.4-5 of the Manual. [Section 3.4.3]
- Verify that a maximum sheet flow length of 100 feet is used if the flow is not concentrated. [Section 3.4.3]
F.6.4 Stormwater Conveyance Pipe Capacity
- Verify that pipe capacity calculations are provided for all stormwater conveyance pipes that are not connected to the roof drainage system. [Section 3.4.2]
- Verify that all storm sewer pipes are sized to have adequate capacity to safely convey the ten-year, 24-hour storm event without surcharging the crown of the pipe. [Section 3.4.2]
- Verify the runoff coefficients used in the pipe capacity calculations. A runoff coefficient value of 0.35 must be used for pervious areas, and 0.95 must be used for impervious areas. [Section 3.4.2]
- Verify the precipitation intensity used in the pipe capacity calculations. The precipitation intensity for a five-minute inlet concentration time in the ten-year storm event must be 6.96 inches per hour. [Section 3.4.2]
- Verify that the Manning’s n values used with Manning’s Equation for calculating full channel pipe flow are correct and consistent with the plans. A Manning’s n value of 0.013 must be used for RCP, VCP, and CIP, and a value of 0.011 must be used for PVC and HDPE. [Section 3.4.2]
- Verify that all roof drainage systems are sized pursuant to the Philadelphia Plumbing Code. [Section 3.4.2]
- Verify that the minimum size of a storm drain or any of its branches that drain a roof or area drain is three inches in diameter.
- Verify that the main roof drain has a slope that is greater than 1/16 inch per foot.