Home to two major rivers and a vast network of creeks and streams, the City of Philadelphia is also one of the nation’s most urbanized cities. Over the past century, many of Philadelphia’s creeks and streams have been replaced with sewer pipes and the city’s natural surfaces paved over or developed. This urbanization has essentially changed the water cycle by preventing infiltration and groundwater recharge while compromising the water quality of receiving rivers. To address federal requirements to improve water quality, the Philadelphia Water Department (PWD) has designed a stormwater management plan, known as Green City, Clean Waters (GCCW), that not only addresses the physical environment, but also brings additional societal benefits. In doing so, PWD has relied on the strength of its partnerships with city agencies, such as Philadelphia Parks and Recreation (PPR), to craft innovative and repeatable projects. This interagency collaboration has been critical to PWD’s success in implementing GCCW.

The combined sewage system that serves most of Philadelphia’s prewar neighborhoods poses a substantial burden on the city’s waterways. During significant rainfall, sewage plants are overwhelmed by the combined flow of stormwater runoff and sewage. As a result, excess wastewater bypasses the sewage plants and is dumped directly into the city’s rivers and streams. Philadelphia, like other cities with combined sewer systems, is required by the Environmental Protection Agency (EPA) through the Clean Water Act to remedy this situation.

As the lead city agency responsible for meeting Clean Water Act permit requirements, PWD has begun to implement a first-of-its-kind approach to address combined sewer overflows primarily through green stormwater infrastructure (GSI). Through GCCW, Philadelphia has committed to spending approximately $2.4 billion over the next 25 years to mitigate combined sewer overflows by capturing stormwater from more than one-third of the city’s impervious surfaces through a variety of green and traditional methods.

GSI comprises a range of soil-water-plant systems that intercept stormwater, infiltrate a portion of it into the ground, evaporate a portion of it into the air, and in some cases slowly release a portion of it back into the sewer system. By capturing stormwater close to where it lands, GSI keeps runoff out of underground sewer pipes, thereby ensuring polluted water does not end up in creeks and rivers. GSI is a departure from the conventional approach of expensive gray infrastructure, or centralized single-purpose infrastructure that treats stormwater as a waste product. Enormous tanks and deep tunnels temporarily store the combined rainwater and sewage until the storm passes. The combined sewage is then transported back into the city’s sewer system to be treated at a wastewater plant.

In addition to reducing combined sewer overflows and pollution to achieve regulatory compliance, Philadelphia’s long-term goal is to provide triple-bottom-line benefits.

“There is real value in implementing GSI solutions when communities can see immediate results and share the multitude of benefits they bring,” says PWD Commissioner Howard Neukrug. “In addition to providing ecological services by managing rainfall, the plan is also about revitalizing our city, neighborhood by neighborhood.”

Only two years into the plan, the city is already beginning to reap environmental benefits such as enhanced air quality, social benefits such as increased recreational opportunities and economic benefits such as new job creation. Since the program’s inception, PWD and its partners have constructed or are in the process of designing and constructing 172 stormwater tree trenches, 25 stormwater bumpouts, 48 rain gardens, 50 porous paving sites and 132 other GSI projects.

A major goal of the program is to leverage PWD’s investments through a variety of public and private partnerships to maximize program benefits. PWD has employed creative strategies to work with other city agencies such as PPR.

“The partnership between PWD and PPR marks a new level of inter-agency cooperation,” says Deputy Mayor and PPR Commissioner Mike DiBerardinis. “Investing in stormwater management has been a win-win for both agencies; it has allowed PPR to capitalize on and improve the condition of our most abundant resource — public land.”

PWD prioritizes projects on public lands, which serve as ideal sites for stormwater management due to ease in acquisition of use, cost-share opportunities and community support. Another key focus has been on the development of innovative yet repeatable designs, as well as decision frameworks usable by involved parties.

An important strategy in creating acreage for GSI implementation is the PPR Green2015 Plan. The main goal of Green2015 is to add 500 acres of new, publicly accessible, green space to the city by 2015. Top opportunity sites for new parks are underutilized public land such as vacant lots, schoolyards and recreation centers in neighborhoods that have little to no access to green space. In serving to both catch stormwater and provide recreation amenities, Green2015 is a catalyst for PPR, PWD and the Trust for Public Land to strategically plan and pilot innovative neighborhood-scale projects that can be replicated.

The first of many Green2015 projects to come that target new open space in underserved areas of the city, Ingersoll Commons will transform a city-owned vacant lot in lower North Philadelphia into a 10-unit affordable housing development and a new city park. All 10 units will face the park, away from their legal street frontage, allowing for a focus on security and increased activity at the park. The park features rain gardens to collect and infiltrate runoff from the site and adjacent blocks. PWD, PPR and the Department of Public Property have partnered with affordable housing developer Community Ventures on this opportunity to create a model of sustainable redevelopment.

Shissler Recreation Center, once a cinder field and most recently a vacant grass field, has been transformed through a joint initiative among PWD, PPR, the Mural Arts Program, the Pennsylvania Horticultural Society and the New Kensington Community Development Corporation. The Shissler site was originally a railroad yard, an emblem of Kensington’s role as an industrial center. Today, the site features a turf recreation field and a spraypark. New stormwater tree trenches and bioinfiltration basins manage onsite runoff and runoff diverted from adjacent streets and sidewalks.

Finally, a one-acre stormwater wetland, constructed on a parcel of historic Fairmount Park known as Saylor Grove, treats an estimated 70 million gallons of urban stormwater per year before it is discharged into the Monoshone Creek. The Monoshone Creek is a tributary of the Wissahickon Creek, a source of drinking water for the City of Philadelphia. In treating stormwater runoff, the wetland improves source water quality and minimizes the impacts of storm-related flows on the aquatic and structural integrity of the nearby river ecosystem. This project, a partnership among PWD, PPR, the Pennsylvania Department of Environmental Protection, Center in the Park and Wissahickon Restoration Volunteers, is a highly visible urban GSI retrofit.

Philadelphia believes that its Green City, Clean Waters plan can serve as a model for other cities interested in implementing GSI. By mimicking the natural water cycle and addressing stormwater as a holistic resource, the city will become a more desirable place to live, work and play.


Amy Liu is a city planner with the Philadelphia Water Department. For more information, contact Mark Focht at PPR.