By Ellen Kohler, JD, MS
Director of Applied Research and Programs
The Water Center at Penn

The City of Philadelphia adopted the Green City, Clean Waters (GCCW) plan in 2011 under the Clean Water Act to reduce pollution resulting from combined sewer overflows. The problem: large storms result in untreated sewage being directed to the rivers around Philadelphia including the Delaware River, the Schuylkill River, Cobbs Creek, Darby Creek, and the Tookany-Tacony Frankford watersheds. Combined sewers carry both rain runoff and sewage to wastewater treatment plants where it is all treated before being discharged to rivers and other water bodies. During large storm events, the system becomes overloaded and cannot carry all of the runoff and sewage to the plant where excess flow is diverted without treatment to rivers and streams, also known as combined sewer overflow or CSO. Lots of cities throughout the country have combined systems and suffer from pollution as a result of CSOs. 

The Clean Water Act is designed to protect existing high water quality and to improve water quality in rivers where there are problems. The goal is to have all waters in the country be clean enough that people can swim in them and fish can live in them. Since the passage of the act almost 50 years ago, we have improved the water quality of so many rivers, streams and lakes because permits limit the amount of pollution that can flow into our waterways. CSOs are a remaining big challenge to meeting the goals of the Clean Water Act.

In 2011, Philadelphia’s GCCW represented an innovative approach to the challenge that many cities have now emulated. Instead of focusing the solution solely on enormous underground tunnels to separate runoff from sewage, the city has adopted a plan that includes lots of green stormwater infrastructure above ground to help reduce the amount of stormwater getting into the gray parts of the system – the inlets and pipes that go to the wastewater treatment plan. 

Water Center executive founder Howard Neukrug was the Philadelphia Water Department’s commissioner when the GCCW plan was adopted. As water commissioner, Neukrug initiated the city’s Green City Clean Waters program, a 25-year effort that has added 2,800 rain gardens, tree trenches, and other green tools at 800 sites around the city, keeping nearly 3 billion gallons of polluted water from entering the riverways.

An essential element of the GCCW plan is the triple bottom line benefits that the green stormwater infrastructure will bring to the city’s residents that cannot be provided by stormwater inlets and underground pipes. The plan’s long-term vision involves creating amenities for the people who live and work in the city including:

  • A large-scale street tree program to improve appearance and manage stormwater at the source on City streets
  • Increased access to and improved recreational opportunities along green and attractive stream corridors and waterfronts
  • Preserved open space utilized to manage stormwater at the source 
  • Converted vacant and abandoned lands to open space or redeveloped responsibly 
  • Restored streams with physical habitat enhancements that support healthy aquatic communities (LTCP Update GCCW at 1-2)

As characterized in the plan, the goal is “to regain the resources in and around streams that have been lost due to urbanization, both within the City of Philadelphia and in the surrounding counties, while achieving regulatory compliance objectives in a cost-effective manner.” (LTCP Update GCCW at 1-2). 

Last year marked the 10th year of implementation under the GCCW. The Water Center along with partners at the University of Maryland Environmental Finance Center, the WaterNow Alliance, PennFuture and the Nature Conservancy embarked on a review of implementation and analysis of the sustainability of financing to meet the plan’s goals by 2036. This research team brought together experts in green stormwater infrastructure program development and financing. The team worked with Philadelphia Water Department staff to ensure that our work addressed the specific issues that PWD was experiencing with implementation on private and non-city public lands. 

To date, PWD’s work on private property has been successful. However, the GCCW envisions a substantial rate of increase in greened acre over the remaining plan years. In addition, many of the projects implemented to date have not had the amount of green elements – trees and plants – as the GCCW envisioned and PWD wants to support. Identifying ways that PWD’s program implementation on private and non-city public lands needs to adapt to meet these challenges were the focus of the team’s analysis.

Analysis of Program Effectiveness on Private and Non-city Public Lands 

While the City has made significant progress in hybridizing the City’s stormwater system to include both gray and green infrastructure and improving the functionality of the system overall in terms of volume and water quality, even maintaining the current rate of implementation without adaptation will not result in meeting the overall plan target by 2036. 

The team’s analysis, briefly summarized below, found that PWD and the City need to invest more in the green stormwater infrastructure grant program for private and non-city public lands and those investments need to be at least steady but more likely increasing over the remaining 15 years of plan implementation. 

The lack of consistent funding for the program makes it challenging for private project developers to know whether there would be funding to support multiple projects. And since the funding is only provided through a grant structure, there is uncertainty about the likelihood of success in getting a grant. These are significant hurdles for private landowners and create racial equity issues because the grant funding is not resulting in enough projects in the parts of the City that have the most significant stormwater issues related to CSOs and flooding. In the early years of the program, less than half of the projects on private land included some kind of vegetation. This lack of vegetation adds to the racial equity issues because the City’s residents are not experiencing the triple bottom line benefits of projects without vegetation. Additionally, racial equity has not been an explicit priority for the grant program, resulting in projects not being implemented in places they are needed the most. 

The research team is aware that these conclusions are well understood by PWD. It is important for other city officials, city residents and stakeholders to understand these challenges in order to support the needed adaptations to meet the GCCW plan targets and vision. 

Based on their conclusions, the team developed a set of eight recommendations around financing strategies and program improvements that are being vetted and refined. The next step in the project is to finalize the recommendations and support PWD as it adapts the GCCW to realize the thriving city it envisions. 


Ellen joins the Water Center after serving as the Program Director for Water Resources at the University of Maryland’s Environmental Finance Center. Her work there focused on water resource management issues challenging communities in the mid-Atlantic region, particularly supporting multi-municipal collaborations to improve water quality and integrated water planning to address drinking water, wastewater and stormwater management. Addressing these challenges has required rethinking financing strategies that provide more equitable outcomes for communities continuing to experience environmental burdens. She brings more than 25 years of experience addressing the legal, regulatory and policy context of water quality and natural resource challenges. Her career began at the US Department of Justice in Washington DC as a trial attorney in the Environmental and Natural Resources Division handling wildlife litigation. After a move to northern Michigan, she started a business providing natural resources policy and legal services for a range of clients including watershed groups, conservation organizations, tribal governments and local governments. Returning to the mid-Atlantic region in 2012, she helped lead a team developing a funding mechanism for source water protection in the Brandywine-Christina watershed as the project manager for the Delaware Chapter of the Nature Conservancy and provided consulting services to several watershed associations and conservation organizations who all shared a commitment to improving water quality in the Delaware River basin. She received her JD from the University of Colorado at Boulder and her MS from the University of Michigan School of Natural Resources (now Environment and Sustainability).