The city led a list of 14 municipalities for its commitment to infrastructure and design changes like green roofs, permeable pavement, tree plantings and rain gardens to capture rainfall and reduce runoff pollution by slowing the flow of stormwater into the city's antiquated sewer system.
"Philadelphia recognizes that green infrastructure, which stops rain where it falls, is the smartest way to reduce water pollution from storms," said Karen Hobbs of the Natural Resources Defense Council, which released the "Rooftops to Rivers" report Wednesday and is one of several environmental advocacy groups that helped the city develop its water management plan. "It often only takes a fraction of an inch to trigger this kind of pollution."
Around 60 percent of Philadelphia has what is called a "combined sewer system," which allows runoff from streets and wastewater from bathrooms and kitchens to flow through the same pipes. The drainage system can handle that in dry weather, properly sending wastewater to water treatment plants and storm water to streams, but rainfall creates overflows that send storm water laced with motor oil, trash, and human waste pouring into surrounding waterways.
More than a decade ago, officials ruled out separating storm water and sanitary lines as was done in newer parts of the city because that would mean reconfiguring 1,600 miles of pipes at enormous expense. Other traditional options - a huge expansion of the city's three sewage plants or construction of gigantic underground tanks to hold overflows - were less efficient and prohibitively expensive.
Officials in Philadelphia, the country's fifth-largest city with 1.5 million people, then began working with state officials and environmental consultants on a major departure from the conventional approaches. They crafted a plan to install green roofs on city buildings, plant trees and other vegetation along sidewalks, and repave streets, basketball courts and parking lots with porous asphalt and concrete that let rainwater flow through.
In June, city and state officials unveiled a 25-year, $2 billion effort to modify infrastructure to reduce the amount of rainwater tainted with road oil, litter and raw sewage flowing into rivers and streams. The changes are expected to eventually reduce sewer overflow into the city's waterways each year, including the Delaware and Schuylkill rivers, by 5 billion to 8 billion gallons - an 80 percent to 90 percent reduction.
The new "Rooftops to Rivers" study looked at six key elements for developing green infrastructure plans and Philadelphia was the only city that met all six criteria. They include identifying a dedicated funding source for the improvements, creating incentives for private property owners, using green infrastructure in comprehensive land and making a long-term plan for how to roll out the changes.
"We're looking under every rock to do whatever we can to provide incentives and make it easy on folks, whether they're developers or homeowners," said Howard Neukrug, commissioner of the Philadelphia Water Department.
The report said five other municipalities met five criteria on its "Emerald City" six-point scale: Milwaukee, New York, Portland, Ore.; Syracuse, N.Y.; and Washington, D.C. Meeting four of six criteria were Aurora, Ill., and Toronto.
The Philadelphia plan's "strength lies in the fact that it is part of a long-term plan, and incorporates both carrots and sticks for the city's residents and businesses," said Erika Staaf, clean water advocate from the environmental group PennEnvironment.
Natural Resources Defense Council: http://www.nrdc.org