- 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
1.3 Stormwater Retrofits
This Section of the Philadelphia Water Department (PWD) Stormwater Management Guidance Manual (Manual) is intended to aid applicants and vendors who are developing Stormwater Retrofit projects in navigating the Manual and additional relevant resources. This Section also highlights the differences between the Stormwater Retrofit Review Path and other Review Paths presented in Section 2.2.
1.3.1 Retrofit Project Applicability and Initiation
As discussed in Section 1.1.1 of this Manual, development projects categorized as Stormwater Retrofits are defined as the voluntary rehabilitation and/or installation of SMPs on a property to better manage stormwater runoff. These projects are implemented by property owners who are motivated to:
- Lower their Stormwater Management Service Charge (Stormwater Charge) with stormwater credits;
- Provide triple bottom line benefits to their property’s occupants that SMPs with green surface expressions can provide;
- Demonstrate commitment to sustainability or environmental stewardship goals; and
- Transform underutilized space on their property to benefit Philadelphia’s waterways and health.
In order for a project to be classified as a Stormwater Retrofit and not a different development type, the project must follow the following criteria:
- Development work and earth disturbance is limited to the installation of the approved stormwater management practice (SMP) and its components. Minor non-stormwater related work may be approved if it does not meet the earth disturbance threshold for applying Stormwater Regulations in the project’s watershed.
- Existing cover types in the predevelopment condition must remain consistent in the post-development condition, unless:
- Impervious area (or area functioning as impervious area, such as compacted gravel) is converted to well-draining pervious grass area or a surface SMP. The new cover type must provide stormwater management benefits and generally comply with requirements within the Stormwater Management Service Charge Credits and Appeals Manual (Credits and Appeals Manual) for open-space stormwater credits (Applicants of Stormwater Retrofit projects proposing any depaving work are encouraged to contact Stormwater Billing and Incentives to confirm exemption from Stormwater Regulations); or
- The earth disturbance involved with any site improvements or changes in cover type are less than 15,000 square feet (or the appropriate disturbance threshold for triggering Stormwater Regulations, dependent on the project’s watershed).
Property owners who are interested in voluntarily managing stormwater on-site are encouraged to apply for a Stormwater Grant. More information about the Stormwater Grant Program, including how to apply, is available on the Stormwater Grants website. This website also provides a link to the Stormwater Grants Application Guide, which outlines the requirements needed for a Stormwater Grant Application. These requirements include, but are not limited to, a Conceptual Stormwater Management Plan, environmental due diligence, and a project budget. If a Stormwater Retrofit project applies for a Stormwater Grant, their Stormwater Grant Application will serve as their Conceptual Review Phase, with their Stormwater Grant award serving as their Conceptual Approval. These Stormwater Grant projects will enter the Post-Construction Stormwater Management Plan (PCSMP) Review Phase after being awarded a Stormwater Grant unless their Conceptual Stormwater Management Plan significantly changes after their Stormwater Grant award.
Classification of a project as a Stormwater Retrofit is ultimately determined by the judgement of PWD staff. Once a project has been confirmed as a Stormwater Retrofit, it will be reviewed by Stormwater Billing and Incentives. The applicant is referred to Sections 2.2.4 and 2.3.4 for more information on how Stormwater Billing and Incentives reviews Stormwater Retrofit plans.
Stormwater Billing and Incentives can be reached during normal business hours (8 am to 5 pm) at (215) 685- 6070 or pwd.stormwatercredits@phila.gov for Credits and Incentives Program-related questions.
1.3.2 Retrofit Project Requirements and Guidance
Stormwater Billing and Incentives reviews stormwater management plans for compliance with managing the first 1.5 inches of runoff as described in the Post-Construction Stormwater Management (PCSM) Water Quality requirement of the Stormwater Regulations. They should also meet all criteria for the Erosion and Sediment Control Requirement listed in Section 1.2.2. To learn more about Stormwater Credit eligibility after completion of the Stormwater Retrofit project, the applicant is referred to Section 6.3. Stormwater Retrofit projects do not need to incorporate aspects from Flood Control, Channel Protection, or Public Health and Safety Release Rate requirements.
Applicants designing a Stormwater Retrofit project should reference Section 1.2.1 for understanding the full Water Quality requirement. However, key differences to note for Stormwater Retrofit reviews are listed below.
Administrative Differences
- There are no review or approval fees for Stormwater Retrofit projects.
- There are no expedited reviews for Stormwater Retrofits. Certain SMP types and stormwater management strategies are considered more competitive in the Stormwater Grant award process for grant-funded Stormwater Retrofit projects.
- Stormwater Retrofit projects do not need to submit a full Construction Certification Package, including material receipts. However, projects should submit construction photographs of key installation points along with their Record Drawings.
- Stormwater Retrofits that receive Stormwater Grant funding will have additional timeline requirements. Applicants should follow recommendations in Section 2.3.4 and contact the Stormwater Billing and Incentives team to review intended project timelines.
Technical Design Differences
- The applicant is encouraged to manage any feasible drainage area on the private property, which is not limited to the earth disturbance area.
- The area within the limit of earth disturbance is not required to be managed. Earth disturbance is less indicative of the amount of stormwater management for Stormwater Retrofit projects than projects required to meet PCSM Requirements.
- Stormwater Retrofits are not required to implement pollutant-reducing practices in the combined sewer area of the city where infiltration is not feasible. These systems are only required for subsurface detention SMPs proposed in the Municipal Separate Storm Sewer System (MS4) for Stormwater Retrofits. Due to this Water Quality difference, Stormwater Retrofits do not consider roof runoff isolation as a design factor.
- Stormwater Billing and Incentives will review disconnected impervious cover (DIC) disconnection strategies on a case-by-case basis, as the majority of Stormwater Retrofits involve SMPs and depaving funded by Stormwater Grants. Tree credits, as described in this Manual, are not a credited stormwater management type for Stormwater Retrofit projects. However, tree canopies can be a strategy for obtaining stormwater credits on a property’s stormwater bill according to the Credits and Appeals Manual. Additionally, some DIC features such as green roofs, may have different management requirements as a Stormwater Retrofit. For up to date information, the applicant should discuss any DIC strategies with Stormwater Billing and Incentives.