By Zoe Cohen, Azavea and Caroline Koch, WaterNow Alliance

The Philadelphia Water Department (PWD) offers a number of incentives to encourage property owners to retrofit their property and install green stormwater infrastructure (GSI) to manage stormwater onsite. They have successfully worked with businesses (both small and large), faith-based institutions, hospitals, and other nonprofits over the past decade interested in adding these cost-saving GSI to their buildings and grounds.

What is the Stormwater Credits Explorer?

To encourage more commercial property owners to apply for PWD stormwater grants, build distributed green infrastructure, and receive credits to reduce their stormwater bills, PWD, together with Philadelphia based professional services firm that builds geospatial web applications Azavea, developed the Stormwater Credits Explorer—an app that virtually adds GSI tools to non-residential properties and calculates potential savings on their stormwater bill through the Credits Program. Launched in 2015, the user-friendly, web-based tool makes it easy (and fun) for non-residential property owners to see the financial benefits of GSI features like green roofs and porous pavement. The Credits Explorer turns any non-residential property into a canvas where a user can sketch out ideas of up to 5 different types of “Stormwater Tools,” including Green Roofs and Rain Gardens, Permeable Pavers and different types of storage basins. The tools enable users to lay out potential changes while keeping realistic limits for that given property. As Stormwater Tools are added or removed, the application updates the monthly stormwater charge for that property. Users can rapidly get a sense of the feasibility and cost-savings of adding stormwater infrastructure systems.

Benefits of Stormwater Credits Explorer to PWD

The Stormwater Credits Explorer not only drives participation in PWD incentive programs and helps property owners save money, this innovative tool benefits PWD. The more non-residential property owners that install GSI to keep stormwater out of the city’s combined sewer system the closer Philadelphia will be to achieving the objectives of its Green City, Clean Waters plan—a 25-year plan to reduce the volume of stormwater entering the city’s combined sewers using green infrastructure and to expand stormwater treatment capacity with traditional infrastructure improvements.

As of August 2021, PWD incentives for private non-residential property have created 740 greened acres. (A “greened acre” is an acre of previously impervious area that is reconfigured to utilize GSI to manage at least one inch of stormwater runoff or ~30,000 gallons of stormwater.) And in Fall 2021, $20 million in grants will be given to private and non-city-owned properties for installing green stormwater infrastructure. PWD anticipates that continued, and increased, use of the Stormwater Credits Explorerwill lead to even more retrofits and greened acres.

Since the 2015 launch of the platform, PWD and Azavea continue to work closely to maintain this application. Led by a project manager and a team of software engineers, Azavea updates software libraries, fixes bugs, and swaps-in the latest satellite imagery layer as they are made available. PWD’s team of GIS specialists, engineers, and city planners work together to ensure the tool is accessible to customers and updated as needed to incorporate any changes in the structure of the credits program.

Check out the full case study on the PWD Credit Explorer in WaterNow’s Tap into Resilience Toolkit.

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