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Green Infrastructure and the Future of Philadelphia

Contributed by Stu Berg, Melissa Muroff & Jane Winkel

Green City, Clean Waters, Philadelphia’s Long Term Control Plan Update, details its innovative strategy for achieving compliance with the Clean Water Act. Philadelphia is not alone among older cities with recurrent unauthorized combined sewer overflows (CSOs) of untreated runoff, sewage, and debris discharged into local rivers, but, Philadelphia is unique in its answer to this complex problem.

 Like all cities facing EPA settlement agreements for violations of National Pollutant Discharge Elimination System (NPDES) permits and the Federal Clean Water Act, Philadelphia must rectify the violations and come into compliance or face exorbitant fines. The plan to rectify the violations and come into compliance is called a Long Term Control Plan Update, which Philly branded as Green City, Clean Waters. The EPA’s clock is ticking; Philadelphia has 25 years to control its CSO’s and reduce its water pollution to legal levels. Recognizing that investing in Green City, Clean Waters is non-optional and urgent, we commend the Water Department’s strategy.

 Traditionally, when faced with such an EPA settlement decree, cities have responded with grey infrastructure: raising taxes across the board and lobbying for a federal earmark to fund a public works project involving ripping up city streets to install larger sewer pipes, building new treatment plants, enlarging existing plants and every city citizen pays. Lots of construction means lots jobs, but the resulting work is more or less hidden from view. Seasonal flooding in parts of the city is mitigated, and when the work is complete, hopefully raw sewage is no longer being discharged into rivers with each big rain storm.

 But this is a new era, and the Philadelphia Water Department surprised even the EPA with its chutzpah. The likelihood of securing a federal earmark for grey infrastructure hovers around 0%, so the Water Department threw a stormwater management Hail Mary pass and committed to the EPA that it will convert Philly into a living Green Machine that processes rainwater without more grey infrastructure. One-third of the pervious cover in the City’s Combined Sewer System will be greened and will filter or store the first one inch of rainwater with each storm. This is green infrastructure: those with impervious surfaces on their property pay. Lots of construction means green jobs (and green jobs training!); the work results in new urban green spaces; mitigation of seasonal flooding in parts of the city, and after a significant percent of the City is greened, sewage ends up where it belongs — in the treatment plants and not into our rivers.

 Celebrating rainwater as a resource, rather than burying it underground in pipes, provides other benefits for Philly residents in addition to stormwater management. Capturing the rain in vegetation, helps to clean the air, mitigate the urban heat island, create habitats and increase quality of life.

 Redesigning a third of the city to mimic the hydrologic characteristics of an undeveloped, untouched landscape is no easy task. Philadelphia has one of the nation’s oldest stormwater infrastructure systems with over 3,000 miles of underground pipe, some of which are the original wooden constructions.  The system serves 135 sq. mi., 64 sq. mi. of which utilize a combined sewer system with outfalls into many Philadelphia watersheds.

 The Green City, Clean Waters program is a collaboration among the PWD and various city departments, including the Streets Department, the Mayor’s Office of Sustainability, the Housing Authority, the Redevelopment Authority, the Zoning Commission and Licenses and Inspections. The City has pledged $2.4B in capital construction and maintenance costs over 25 years to meet water quality goals, and $260M in stream restoration and wetland creation.  Even more significant will be the investment of developers in as they build in compliance with the City’s stormwater regulations.  New construction and re-developed sites meeting the stormwater regulation’s earth disturbance threshold are required to manage stormwater on site by limiting the release rate and treating runoff before it discharges into the City’s storm sewer system. 

 The beauty of Green City, Clean Waters is that the cost to city residents depends on the amount of impervious surface on their own property. Why should the Friends Center contribute an amount commensurate with the airport? The Friends Center has invested far more than the airport in progressive measures to manage stormwater and controls the runoff from their impervious surfaces. The program is fundamentally fair and will ultimately incentivize smart urban greening among City officials and City residents. The City has invested in programs to support those commercial owners most financially impacted by Green City, Clean Waters. Low-interest revolving loans, free consulting, and reduced utility fees for voluntary compliance are all available.

 While the new regulations are a giant leap forward for environmental policy, at this stage a poor return on investment on some green infrastructure poses an obstacle to the success of the program. In this economy, businesses are understandably reluctant to voluntarily spend thousands of dollars to comply with the City’s stormwater regulations without more attractive incentives. Additionally, most stormwater management Best Management Practices (BMPs) recommended by the City, with the exception of green roofs, porous pavement, and below-structure infiltration galleries, take up take up space that could otherwise be dedicated to other uses, including parking.  How shall we overcome this barrier? We favor lowering the stormwater regulation’s earth disturbance threshold to trigger required compliance. In most watersheds, including the Delaware River watershed (including Center City), the current threshold is 15,000 sf — too high to trigger compliance in many cases. Now, developers can avoid the stormwater regulations  by rehabbing an existing building without significantly changing the footprint of a property. If the earth disturbance threshold were smaller, more properties would be subject to the City’s stormwater regulation and green infrastructure measures would then make financial sense to bottom line conscious businesses.

 We are excited that the PWD recognizes green roofs as a key element in Green City, Clean Waters. Yes, we are biased about green roofs, but they are beautiful and pervious – compliance silver bullets. Note that commercial, industrial, public and residential developments cover an estimated 77% of the city! Roof runoff constitutes the largest stormwater contribution in the City’s sewer system. What’s the financial case for a green roof? Monthly stormwater fees for every 1,000 sf of impervious area can be reduced from roughly $10 to $2 a sf by converting impervious cover to pervious cover.  Under the City’s stormwater regulations, a 25,000 sf commercial development can save $200 per month or $2,400 per year by managing their stormwater with a green roof. The Department of Revenue also offers a business privilege tax credit worth up to $100,000 to property owners who install a green roof.

Philadelphia – the greenest city in the U.S.? Pie in the sky? Not anymore!

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