Philadelphia and the U.S. Environmental Protection Agency signed an agreement in April that paves the way for $2 billion in green infrastructure investment over the next 25 years for controlling combined-sewer overflows, or CSOs, and managing stormwater more sustainably. The agreement pledges EPA's endorsement of the "Green City, Clean Waters" plan, a long-range commitment to protect and enhance the city's watersheds by managing stormwater with bioretention, tree trenches, swales, green roofs, rain gardens and porous pavement.

"Every year, approximately 11 billion gallons of combined sewage spills into [the city's] rivers and streams," says Chris Crockett, Philadelphia Water Dept. deputy commissioner of planning and environmental services. "Green infrastructure is needed for decreasing the city's impervious surface and reducing CSOs."

Philadelphia is pushing the nation's largest commitment to green infrastructure for dealing with CSOs and urban runoff issues, says Jon Capacasa, director of water protection for EPA's Region 3.

Larry Levine, a Natural Resources Defense Council senior attorney, says the current pact builds upon a June 2011 agreement and consent order between the city and Pennsylvania that supports the use of green infrastructure for reducing sewage overflows. The partnership "provides for the city and the EPA to collaborate on pilot projects now and to hammer out a more comprehensive consent order in the coming months," Levine says.

The city is issuing RFPs for planning and design work and evaluating bids for construction of green infrastructure projects. "In fact, $30 million of green infrastructure is currently being installed," Crockett says. "In the near future, we anticipate the amount of work to increase to $50 million per year."

The Philadelphia Water Dept. has 100 blocks of green street projects going out for bid in the next few months; construction is expected to ensue this year. Moving forward, Crockett expects all future water and sewer line replacements will include an evaluation on the feasibility of installing green infrastructure.