New Report Identifies Opportunities to Expand Green Stormwater Infrastructure in Philadelphia Through Real Estate Redevelopment Projects

A tree sits on a grassy patch. In the distance a city skyline is visible.
Philadelphia The Philadelphia skyline emerges in a view from the Belmont Plateau. © J. Smith from Visit Philly

Media Contacts

Confusing and lengthy approval requirements, high staff turnover, zoning variances, and perceived maintenance costs are among the top challenges cited by Philadelphia real estate developers when considering green stormwater infrastructure (GSI) within development projects, according to a new report co-authored by the Sustainable Business Network of Greater Philadelphia (SBN), The Nature Conservancy (TNC) and The Water Center at Penn (WCP).

The new findings, based on a year’s worth of interviews with private developers and City of Philadelphia municipal staff, will aid officials in identifying existing bottlenecks in the City’s development review process and offer potential solutions for streamlining reviews to facilitate broader GSI adoption by developers. The Philadelphia Water Department (PWD) has identified GSI as a critical tool in achieving its Green City Clean Waters initiative, a 25-year plan to reduce pollution from stormwater runoff and combined sewer overflows.

In its key takeaways, the report finds that while it is widely agreed upon that PWD is communicative and committed to assisting developers with navigating the review and approval processes, stormwater management is still often perceived as a costly and/or time-consuming hindrance—rather than an asset—in the development process and thus is avoided when possible.

Water flows out of a large metal pipe into a puddle.
Philadelphia Philadelphia has a combined sewer system that is prone to overflows following wet weather events, like rainfall or snowmelt. © Sickter6/Creative Commons

The report’s authors also examined current stormwater regulations, plumbing and landscaping codes, additional zoning requirements, and existing green incentives, creating a new visualization guide showing the entire development review process from start to finish for real estate development projects in Philadelphia. The graphic illustrates the ways in which the City of Philadelphia’s real estate development review process intersects with PWD’s stormwater review process, clarifying this stepwise process for developers and offering the potential for future efficiencies.

The study’s authors hope that the report will be yet another tool to aid GSI implementation and support citywide efforts to invest in nature-based solutions for cities.

“This white paper and accompanying visualization guide are keys to addressing a very clear need for investing in and bolstering private investment in green stormwater infrastructure and vegetated practices within Philadelphia as we approach the 15-year mark for Green City, Clean Waters,” said Alex Cupo, GSI Partners Manager at SBN. “Meeting the City of Philadelphia’s Greened Acre goals by 2031 will require a sizable leap in private investment. It is our hope that this guide will assist developers and the City of Philadelphia alike as a tool to navigate the city’s redevelopment process and identify new areas for collaboration and innovation.”

Philadelphia has a combined sewer system that is prone to overflows following wet weather events, like rainfall or snowmelt. When sewers reach their capacity, the mix of wastewater and stormwater is discharged into nearby waterways, leading to contamination in rivers and creeks, erosion of the landscape, unsafe health and recreation conditions for people, and habitat degradation for native plant and animal species. GSI involves a variety of soil-water-plant systems that intercept stormwater, send portions into the ground and air, and, in some cases, release a portion slowly back into the sewer system. The process reduces stormwater pollution and combined sewer overflows.

“Stormwater is the fastest-growing source of freshwater pollution in the world. As flooding and overflow events continue to increase, GSI will become even more critical for urbanized landscapes to adapt to the changing climate, especially those with combined sewer systems like Philadelphia,” said Lyndon DeSalvo, Urban Project Manager at TNC in Pennsylvania and Delaware.

Quote: Lyndon DeSalvo

Stormwater is the fastest-growing source of freshwater pollution in the world. As flooding and overflow events continue to increase, GSI will become even more critical for urbanized landscapes to adapt to the changing climate, especially those with combined sewer systems like Philadelphia.

Urban Project Manager for TNC PA

PWD has identified GSI delivered via private development as one of its critical pathways to meeting its clean water goals. PWD measures its progress towards these goals in “greened acres”—a term used to describe the volume of stormwater managed by green tools. One greened acre leads to more than 27,000 gallons of managed stormwater during a 1” storm. To date, the Green City, Clean Waters program has reduced overflows by more than 3 billion gallons on average annually.

The majority of private development projects in Philadelphia are considered “redevelopment” due to historic urbanization and the lack of undeveloped land in the city. Redevelopment is the development of land that involves the demolition, removal and replacement of existing structures or impervious surfaces.

“GSI can provide many co-benefits to communities, including improving air and water quality, mitigating extreme heat, reducing flood risk, and ensuring equitable access to green space,” said DeSalvo. “What this new report shows us is that there are many ways to improve the development process in Philadelphia to increase stormwater projects that include ‘green’ elements such as trees, rain gardens, and green roofs. Now, all stakeholders navigating the development process have a guide to better understand the necessary reviews and approvals, including those related to stormwater management, with the ultimate goal of increasing GSI implementation to improve water quality and make our communities more resilient.”

Based on findings from interviews with developers, City staff and other stakeholders, the research team developed a set of 13 recommendations to address the seven identified pain points of the development review process.

Key recommendations include:

  • Increase stormwater credits for vegetated GSI
  • Streamline zoning code bonuses and expand to other district
  • Combine GSI and landscaping requirements in the zoning code
  • Increase support for GSI maintenance


“We’d like to thank PWD, the development community, and the City agencies we spoke with for their time and willingness to share their experiences with the development process. With their contributions, we hope this report will demystify the development process so that developers of any capacity and any size are able to incorporate GSI into their projects,“ said Emma Denison, Communications and Student Manager at the Water Center at Penn.

Funding for this project was provided by SBN through a grant from the William Penn Foundation.

Four people in vests hold shovels and dig into a dirt patch in a paved lot.
Philadelphia TNC works to implement green infrastructre accross Philadelphia. © Marc Steiner

For More Infromation

For more information about TNC's work in Philadelphia, visit:

× Four people in vests hold shovels and dig into a dirt patch in a paved lot.

About the Sustainable Business Network of Greater Philadelphia:

The Sustainable Business Network of Greater Philadelphia is building a just, green, and thriving economy. We empower the region’s diverse independent businesses to do well by doing good; we advance industries critical to a vibrant, local, equitable, and climate-resilient economy; and we advocate for an economic ecosystem that centers localism, serves community needs, shares wealth, and protects the environment. 

Since our founding in 2001, SBN has remained the region’s only membership and advocacy organization playing the important role of serving Greater Philadelphia’s independent values-driven business community.


About The Water Center at Penn:

The Water Center at Penn is a community-focused research center working to find integrated solutions to the multiple challenges facing our world’s water systems and their watersheds. We strive to be a trusted, reliable partner whose work accelerates water equity by connecting, convening, and collaborating across the sector.

The Water Center’s research approach is centered around working alongside communities, bringing their knowledge and expertise to the solutions addressing their water challenges, sharing power and responsibility, and encouraging communities to take the lead in determining priorities, questions to be asked, and the approach to answering those questions.  We share resources, education, training, and applied knowledge to support community goals.

The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world’s toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. The Nature Conservancy is working to make a lasting difference around the world in 77 countries and territories (41 by direct conservation impact and 36 through partners) through a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit or follow @nature_press on X.