Last Updated 08/07/2026
Stormwater Regulations and Fees in Philadelphia
The City of Philadelphia has enacted a Stormwater Ordinance in order to maintain a healthy environment for the citizens of Philadelphia, prevent flooding, protect drinking water sources, and comply with the Federal Clean Water Act. The City of Philadelphia is the permitting authority for all land disturbing activities and requires the land owner to maintain all on-site stormwater control facilities and all open space areas (e.g. parks or “green” areas) required by the approved stormwater control plan. The City of Philadelphia will only provide construction permits to projects that establish a plan to manage stormwater runoff occurring during the construction process. Stormwater fees will be calculated and collected by the city. Stormwater credits and grants are available to non-residential properties that engage in stormwater best management practices and/or maintain stormwater management facilities. The City of Philadelphia, under the NPDES program, also has the authority to inspect properties for noncompliance and can issue a notice of violation (NOV) for any deficiency or infraction onsite. Property owners are responsible for the maintenance of any stormwater facilities or practices located on the property. The City of Philadelphia has the authority to inspect stormwater facilities and practices in order to ascertain that they properly maintained and functioning.
Stormwater Fee & Credits
Non‐residential customers’ fees are based on the measured gross area and impervious area on their parcels. The rates for each of these rate components are: $0.526 per 500 square feet of gross area and $4.145 per 500 square feet of impervious area. The stormwater charge for a parcel is equal to: (gross area rate * gross area of the property) + (impervious area rate * impervious area of property).
Gross Area (GA): All of the parcel area within the legally described boundaries except streets, medians, and sidewalks in the public right-of-way.
Impervious Area (IA): A surface, which is compacted or is covered with material that restricts infiltration of water, including semi-pervious surfaces such as compacted clay, most conventionally hard-scaped surfaces such as streets, driveways, roofs, sidewalks, parking lots, attached and detached structures, and other similar surfaces.
Credit Eligibility
Customers on a Non-residential or Condominium parcel with at least five-hundred (500) square feet of gross area and whose water, sewer, and SWMS accounts(s) are not past due are eligible to apply for credits.
Impervious Area Reductions (IARs) Credit
PWD currently offers IARs for the following five categories:
- Tree Canopy Cover
- Roof Leader/Downspout Disconnections
- Pavement Disconnections
- Green Roofs
- Porous Pavement
IARs result in a direct reduction of the billable IA on a parcel. The customer must demonstrate that the IARs calculated on the parcel meet the requirements defined below.
Note: IARs require ongoing maintenance in order to maintain their effectiveness and are subject to renewal requirements.
Calculation of SWMS Charge with Credits
In the case of parcels that are eligible for one or more classes of credits and/or IARs, the total monthly IA and GA charges are calculated in the following sequence:
– Step 1: Determine any areas that meet the IAR criteria and subtract the total IAR area from the billable IA.
– Step 2: Determine any applicable credits. The approach used in calculating the IA and GA credits varies depending on a property’s drainage characteristics and existence of an active NPDES permit for stormwater industrial discharge activities. The IA and GA credits are calculated as follows:
i. NON-SURFACE DISCHARGE Areas without NPDES Credits: For areas of a property that do not discharge stormwater to a surface water body, applicable credits are calculated as follows:
• The IA Credit is calculated by applying an 80% maximum credit factor to the parcel’s IA square footage that is managed (IA Managed).
• For the GA underneath the IA Managed, the GA Credit is calculated by applying an 80% maximum credit factor to the square footage of IA Managed.
• For any open space areas (GA minus IA), a GA Credit up of 80% may be applied, as applicable
ii. NON-SURFACE DISCHARGE Areas with NPDES Credits: For areas of a property that do not discharge stormwater to a surface water body and the property has an active NPDES permit for industrial stormwater discharge activities, applicable credits are calculated as follows:
• The IA Credit is calculated by applying an 87% maximum credit factor to the parcel’s IA square footage that is managed (IA Managed).
• For the GA underneath the IA Managed, the GA Credit is calculated by applying an 87% maximum credit factor to the square footage of IA Managed.
• For any open space areas (GA minus IA), a GA Credit maximum of 87% may be applied, as applicable.
• If the property is not eligible for any GA or IA credits, then the property will receive a 7% credit towards both the IA and GA square footage.
iii. SURFACE DISCHARGE Areas without NPDES Credits: For areas of a property that discharge stormwater to a surface water body, applicable credits are calculated as follows:
• The IA Credit is calculated by applying a 90% maximum credit factor to the parcel’s IA square footage that is managed (IA Managed).
• For the GA underneath the IA Managed, the GA Credit is calculated by applying a 90% maximum credit factor to the square footage of IA Managed.
• For any open space areas (GA minus IA), a GA Credit maximum of 90% may be applied, as applicable.
iv. SURFACE DISCHARGE Areas with NPDES Credits: For areas of a property that discharge stormwater to a surface water body and the property has an active NPDES permit or industrial stormwater discharge activities, applicable credits are calculated as follows:
• The IA Credit is calculated by applying a 97% maximum credit factor to the parcel’s IA square footage that is managed (IA Managed).
• For the GA underneath the IA Managed, the GA Credit is calculated by applying a 97% maximum credit factor to the square footage of IA Managed.
• For any open space areas (GA minus IA), a GA Credit maximum of 97% may be applied, as applicable.
– Step 3: The final billable IA and GA (Final IA and Final GA) are calculated as the total IA and GA minus any applicable IA and GA credits, determined in Step 2.
– Step 4: The IA and GA charges are then calculated based on the Final IA and GA square footage (calculated in Step 2) and the IA and GA rates defined in PWD Regulations, Section 304.0.
Gross Area Stormwater Credit
Two options are available to customers to receive GA Credit.
– Option 1: Management of the First-Inch of Runoff (Impervious Area Only)
GA Credit is automatically achieved when a parcel is approved for IA Credit through management of the first inch of runoff. The area that receives IA Credit will also receive an equivalent amount of GA Credit for the land area underneath the IA.
– Option 2: GA Credit Based on NRCS-CN (Open Space Only)
This option is only applicable to the open space of a parcel. Under this option, the customer must demonstrate a Natural Resource Conservation Service Curve Number (NRCS-CN) that meets one of the values contained in the Curve Number Scale found in Appendix 1. The CN represents the runoff potential for a particular soil and ground cover.
A percent reduction is applied for each whole number below a CN of 75. A CN of 55 may yield the maximum applicable GA Credit. The percent reduction that is applied varies depending on a property’s discharge characteristics and the existence of a NPDES permit for industrial stormwater discharge activities. The CN Scale in Appendix 1 provides the GA Credit associated with the different scenarios. More information on NRCS-CN is available in the Stormwater Management Guidance Manual.
Credits Application Processing
PWD will conduct technical review of credits only after receipt of a complete application, including the fee and all required supporting documentation. PWD will review a credits application only if the customer’s water, sewer, and stormwater charge payments pertaining to the parcel are current.
Site Inspections
After a customer submits a credits or credits renewal application, PWD may inspect the parcel to verify the information provided in the application and in the supporting documentation. It is the responsibility of the customer to allow PWD access to the parcel.
Following submission of a credits or credits renewal application, the customer shall grant the City, its employees, or authorized agents permission to enter the parcel on providing forty-eight (48) hour written notice and, in any case, at reasonable times and without unreasonable disruption, to inspect the parcel to ensure that the information provided in the application accurately represents the current parcel conditions.
View State Page
Resources
Philadelphia Stormwater Appeals
View Website
Philadelphia Water Department Rates and Charges
View PDF
Philadelphia Stormwater Incentive Grants Manual
View PDF
Philadelphia Stormwater Incentive Grant Program
View PDF
Greened Acre retrofit Program Grant
View PDF
Philadelphia Stormwater Grants Application Guide
View PDF
Philadelphia Stormwater Homepage
Visit Website
Philadelphia Construction Guidance
Visit Website
Philadelphia Stormwater Management Requirements
Visit Website
Frequently Asked Questions
Who maintains stormwater facilities after construction in Philadelphia?
The property owner. Philadelphia is the permitting authority for all land disturbing activities and requires landowners to maintain all on-site stormwater control facilities and any open space areas, such as parks or green areas, required by the approved stormwater control plan. Construction permits are only issued to projects that establish a plan for managing runoff during construction, a responsibility that continues once the project is complete. AQUALIS can help property owners in Philadelphia build a maintenance plan that meets this ongoing obligation.
Can the City of Philadelphia inspect my stormwater facilities?
Yes. Under the NPDES program, the city has the authority to inspect properties for noncompliance and can issue a notice of violation for any deficiency or infraction found on-site. This applies to any stormwater facilities or practices located on your property, since you’re responsible for keeping them properly maintained and functioning.
How is my stormwater fee calculated in Philadelphia, Pennsylvania?
For non-residential customers, the fee is based on your parcel’s gross area and impervious area. The rates are $0.526 per 500 square feet of gross area and $4.145 per 500 square feet of impervious area. Your total charge equals your gross area multiplied by its rate, plus your impervious area multiplied by its rate.
Can I reduce my stormwater fee in Philadelphia?
Yes, if you’re a non-residential or condominium property owner with at least 500 square feet of gross area and current water, sewer, and stormwater accounts. Philadelphia offers Impervious Area Reductions for tree canopy cover, roof leader and downspout disconnections, pavement disconnections, green roofs, and porous pavement, each of which directly reduces your billable impervious area. AQUALIS can help property owners identify which reductions and credits apply to their site.
Will the city inspect my property after I apply for a stormwater credit in Philadelphia?
Yes, potentially. After you submit a credits or renewal application, the Philadelphia Water Department may inspect your parcel to confirm the application matches actual site conditions. You’re required to grant access with 48 hours written notice, at reasonable times, without unreasonable disruption.
Are there grants available for stormwater projects on my Philadelphia property?
Possibly, for non-residential property owners. The Stormwater Management Incentives Program (SMIP) grant supports the design and construction of stormwater mitigation measures like detention basins, green roofs, porous paving, and rain gardens, with awards generally capped at $100,000 per impervious acre managed. Recipients must execute an Operations and Maintenance Agreement as part of the grant. AQUALIS can help property owners put together a competitive SMIP application.
What best management practices does Philadelphia recognize for stormwater management?
The city’s Stormwater Management Guidance Manual describes a wide range of accepted BMPs, including green roofs, rain barrels and cisterns, filter strips, bioretention systems, detention basins, vegetated swales, constructed wetlands, wet ponds, subsurface vaults, subsurface infiltration systems, and porous pavement. Each is designed to manage either the volume, rate, or quality of stormwater runoff, and the right choice depends on your site’s specific conditions.
The information on this page is provided for general informational purposes only and is not legal advice. Regulations change frequently — AQUALIS makes no warranty as to the accuracy or completeness of this content, and any reliance on it is at your own risk. Consult a qualified professional or your local regulatory authority to confirm requirements applicable to your specific property.
