Philadelphia’s Battle Against Impervious Asphalt
from Streetsblog Capitol Hill by Tanya Snyder
...
Katherine Gajewski, Philly’s sustainability director, says the change was a shock to the system for some people. “Imagine a car rental shop with acres and acres of impervious pavement,” she said, “but it only has three employees in the office and so they’ve always had a low water bill.” But now, with the city factoring in a company’s larger water footprint, its water bill could go from $400 to $2,500. Meanwhile, a skyscraper’s water bill could go in the opposite direction, with its high consumption mitigated by its slender footprint and a high surface-to-volume ratio.
Like attempts at market rate parking or congestion pricing, the stormwater effort forces people to pay the true costs of their behavior, including environmental impact. And though advocates for transportation options may not think about sewer overflow on their list of environmental hazards caused by the automobile, car-based infrastructure poses one of the biggest threats to sound stormwater management.
Philadelphia’s goal is to capture the first inch of rainfall in any storm event. They aren’t trying necessarily to use the water – Philadelphia doesn’t have a water shortage. The problem is that a big rain will overfill the sewers and flow into the waterways, causing a major water pollution problem. (In Philadelphia, unlike some cities with more modern water systems, stormwater and wastewater go to the same place. Under normal circumstances, that place is the water treatment plant. When the sewers are overwhelmed, it flows out to rivers and creeks.) The problem has knocked Philadelphia out of compliance with the Clean Water Act. For every acre of impervious asphalt “greened,” the city says, they reduce runoff by a million gallons a year.
And of course, climate change, caused in part by all the cars running on all that asphalt, is bringing about more and more severe weather events that are creating more and more burden for struggling water systems and causing more and more water pollution.
...