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  • Allison Stalker

Stormwater Management Practices

Updated: Aug 29, 2023

The City of Philadelphia has recently changed their stormwater management policies along with the system used to charge customers. On October 6, 2010, a seminar was conducted to explain these changes and also offer methods and programs to reduce any negative impacts from the changes. I attended this seminar and have summarized some of the important “take aways” from the meeting below —-

Previously, the stormwater charge on a monthly water bill was based on the size of the water meter. Many commercial customers had expressed their concern that they were overpaying. For example, a high-rise building typically has a large meter to provide water to upper floors, however, the area that comes in contact with stormwater is small, usually just a rooftop. This means that these types of buildings were paying large monthly stormwater bills for services they didn’t fully use. As of July 2010 the system has changed to be based on the impervious, or hard, area and also the property size. 80% of the bill will be based on impervious area and 20% will be based on gross area, or property size.

Many business owners who attended the October 6 meeting are upset with these changes. Some of these business owners went from paying a few hundred dollars a month to a few thousand dollars a month in stormwater fees. Businesses that have large parking lots or asphalt areas are hit the hardest by these changes. To help mitigate these cost increases, the Philadelphia Water Department (PWD), under the direction of the EPA and PADEP, have created a credits and incentives program. Under this program, three different types of credits are offered: Impervious Area (IA) credits; Gross Area (GA) credits; and NPDES credits. The IA and GA were discussed at length in the seminar and a number of professionals offered ways to maximize a customer’s credit.

The largest credits usually come in the form of IA credits, since the IA is 80% of the monthly bill. To receive this credit, the customer must demonstrate the management of the first inch of runoff from the IA. The stormwater management practice (SMP) must collect and treat water as defined in Section 4.3.1 of the Stormwater Management Guidance Manual available on the PWD website. These SMPs can take many forms including rain gardens, rain catchers, basins, green rooftops, and porous asphalt. A GA credit can be obtained by the attenuation of the peak rate of runoff. The SMPs used for IA credits can often also be used for GA credits.

To receive these credits, the customer should first meet with a professionally engineer or planner and work with them to create a stormwater management plan for the property. This plan should then be submitted to the PWD. It is encouraged that the customer meet with the PWD to ensure that the design is understood before any money is spent. If the PWD accepts the plan upon site inspection and design review, then construction may begin. Only after construction of all SMPs is complete can Form B, the Stormwater Credits Application, be submitted.

The main concern that I found most attendees had with this process is that these SMPs are expensive to design and construct. Some of the projects that have been completed included nearly $200,000 spent on the SMP. The Philadelphia Industrial Development Corporation (PIDC) has worked together with PWD to create the Stormwater Management Incentives Program. This program offers 1% interest loans of up to $1,000,000 to aid in the design and construction of SMPs. There is currently only $5,000,000 available for these loans. While many customers have significant concerns with these changes, I believe that the City of Philadelphia has created a valid opportunity for green growth in the city. The new system divides the program costs more fairly among properties.

For information on PIDC and the Stormwater Management Incentives Program follow this link:

For information on stormwater billing and how the changes may affect your business follow this link:

For Form B, the Stormwater Credits Application, follow this link:

Ms. Stalker is an Environmental Intern at our firm. She is also attending Drexel University for her Masters in Environmental Science.



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