Philadelphia to harness storm water

A storm drain in the city's Crescentville area

With water becoming an increasingly valuable resource, it is no surprise that cities and countries are doing everything they can to harness as much of it, and waste as little of it that they can. With that in mind, Philadelphia has announced a $1.6 billion plan to utilise storm water, instead of diverting it to rivers and storm drains.

The 20-year plan, said to be one of the country's most ambitious, will see the city essentially redesigned to included a plethora of rain gardens, green roofs, thousands of additional trees, porous pavement, and more.

What this would do is enable the city to be filled with 'sponges' that would absorb - or at the very least - stall the billions of gallons of rainwater that overwhelm the city sewer system every year.

As well as the usual benefits of such a project - more jobs, higher property values, better air quality and less energy use - it has been praised for its innovation, which will depart from the usual engineered tunnels and sewage plant expansions that major cities usually opt for.

"This is the most significant use of green infrastructure I've seen in the country, the largest scale I've seen," said Jon Capacasa, regional director of water protection for the Environmental Protection Agency, who decides whether the scheme is green lit

"We commend Philadelphia for breaking the ice," he said.

Many hope the idea will be expanded in other cities, as it is a problem that is not just suffered by Philadelphia. Currently, the city has a century old sewer system that, when it rains, has to deal with run-off from the streets and waste-water from bathrooms and kitchens. However, more often than not, the system overflows.

With no place to go, the water - now laced with road oil, litter, and raw sewage - gushes from 164 pipes directly into local rivers. It is estimated that the amount of overflowing water exceeds 14 billion gallons a year.

Any plans to separate the storm-water and sanitary lines were quickly dismissed when it was realised that it would involve reconfiguring 1,600 miles of pipes and digging up every yard of pavement. That left two traditional, but ineffective, ideas: massively expanding the city's three sewage plants or building gigantic underground tunnels to hold the overflow until it could be pumped back out and treated.

Both options were expensive and not just that, but on sunny days the capacity is wasted. That's when the thinking started to shift;

"Instead of figuring out how to manage this pollution, maybe we should be looking at how to prevent it in the first place," said Howard Neukrug, director of the Office of Watersheds in the Water Department. "Let's break down some of the barriers against nature and deal with rainwater where it lands."

As such, a plan was launched to "peel back" the city's concrete and asphalt and replace them with plants - with rain gardens, green roofs, heavily planted curb extensions, vegetated "swales" in parking lots, and mini-wetlands. This meant that previously impervious streets would be replaced with paving made out of larger particles that let rainwater flow through and leave no puddles behind.

It is a grand scheme and one that has much support, but it does have flaws. Firstly cost, it is estimated that implementing the plan will add $8 to the typical resident's monthly sewer bill over the next two decades, more than the EPA would like. Also, the EPA wants to see overflows reduced by 85 percent; this plan gets the city to just 80 percent.

Despite this, it has won a lot of support. "I believe it's the most significant investment in transforming the city that we'll see in our lifetimes," said Patrick Starr, senior vice president of the Pennsylvania Environmental Council. "It will change the way neighbourhoods look, the way many streets and blocks look."

What is clear is that cities such as New York and Chicago will be watching Philadelphia closely to see if the scheme works. If so, it is an idea that could go national.

Images: Philly.com

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