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Philadelphia water management: from grey to green infrastructure

 
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Philadelphia has become a leader in green water management. Measures include replacing 30% of its concrete roads with porous ones. Photograph: Corbis

 

Powered by Guardian.co.ukThis article titled “Philadelphia water management: from grey to green infrastructure” was written by Sadhbh Walshe, for guardian.co.uk on Monday 10th June 2013 14.40 UTC

Every year storm-water run-off causes nearly 10tn gallons of polluted water to be dumped into America’s rivers and oceans. As cities across the country struggle to comply with federal regulations surrounding pollution, Philadelphia is emerging as a model of innovation in water management by opting for cost effective natural solutions to an expensive man-made problem.

Concrete and rainfall

It’s not by chance that Philadelphia has become a leader in green water management. Two major rivers flow through the city, and historically it had a vast network of creeks and streams. Over the past 100 years or so of relentless development, many of these creeks and streams have been replaced with concrete pipes and sewers, and most of the city’s naturally porous surfaces have been paved over, making it impossible for rain water to be absorbed where it falls.

As Larry Levine of the Natural Resources and Defense Council (NRDC) explains: “When we pave over the earth and prevent water seeping into the ground, we put barriers in the way of natural processes. Storm water has to go somewhere. Today, most of it goes into concrete systems.”

Unfortunately, these concrete systems are not always able to accommodate all the storm water that comes their way. The Philadelphia Water Department (PWD) estimates that, when all the impervious cover in the city is exposed to one inch of rainfall, it generates about 327m gallons of storm water. This first inch of rainfall gathers most of the surface pollutants before being routed into the city’s combined sewage systems. If the system becomes overwhelmed with excessive runoff, it is designed to overflow. When it does, you get raw sewage mixed with polluted storm water spewing directly into the rivers and creeks.

From grey to green infrastructure

A few years ago, when faced with having to come up with a viable long-term storm-water management plan to meet their obligations under the Clean Water Act, the PWD saw an opportunity to reinsert nature into what had become an unnatural equation. Instead of opting to expand the traditional grey infrastructure and build more pipes and tanks to treat wastewater, they chose to invest in green infrastructure to restore nature’s ability to capture water where it falls and treat it as a resource before it ever becomes waste.

When a cost benefit analysis showed the latter option to be far less expensive than the former (around $2.4bn over 25 years for the green approach as opposed to $8bn for the grey), the city became convinced that it was making the right decision.

Managing water the green way involves a multi-pronged approach, ranging from distributing rain barrels to residents free of charge and planting strategically located rain gardens in parks, on curb-sides and on rooftops, to the more challenging and costly task of replacing 30% of the city’s concrete roads and pavements with porous ones.

The ultimate goal is to minimise the need for large storage tanks and treatment plants by enabling the water to be captured where it falls. The PWD’s public affairs manager, Joanne Dahme, is quick to point out, however, that the new green infrastructure is not meant to replace the old grey infrastructure, but to complement it. “The green approach could not work without a good traditional foundation. Pipes and sewers are the backbone of our system, but the green helps the grey do a better job.”

Bills, bills, bills

So far the programme is mostly funded directly by the city’s ratepayers, some of whom have not been happy to see their storm-water bills increase. However, the PWD did not simply institute an across-the-board rate rise, but switched from a meter-based system to a more equitable system based on parcel size. This has meant that some businesses, such as parking lots, which would have had relatively low bills based on water usage, are now paying much higher rates based on how much storm water their property generates to the sewer system. Meanwhile, high rises that do not have a lot of impervious cover will have seen their rates decrease.

The beauty of the new fee system is that it incentivises private property owners to retrofit their sites with green infrastructure. Those who take advantage of the credit incentives will not just see their rates go down but ultimately as the city becomes greener and there is less storm water to deal with, rates will go down for everyone. The new fees will not be fully phased in until 2014, but Dahme says that business owners facing higher storm-water fees have already expressed a lot of interest in working with the PWD to retrofit their properties, and the city is looking at several cost-sharing opportunities.

Private investment

The city is also working to leverage private capital to support the transition from grey to green. According to Eron Bloomgarden, a partner at EKO Asset Management, who specialises in this area, there are a lot of investors interested in environmental impact. The key is to develop compelling financial products for them to put their money to work in. “We can do for green infrastructure (GI) what the Energy Savings Corporations (ESCOs) did for green energy. ESCOs were able to encourage investment by demonstrating the long term energy savings, GISCOs can do the same thing for green infrastructure.”

 

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