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Green infrastructure: making the city a sponge

Marc Lefkowitz  |  02/03/09 @ 9:53am

At the recent NACWA Sustainable Infrastructure national water quality conference in Cleveland, we heard some very eye-opening speeches about how water and sewer departments around the country are embracing green, not gray, infrastructure to handle the first flush of storm water.

In the same month that the Solar 2007 conference revealed the progress Pennsylvania has made funding and installing solar and wind (thanks to its Renewable Portfolio Standard), we learned that Philadelphia-and Milwaukee, Chicago and Portland-are leaps ahead of Northeast Ohio in reducing water pollution, stream erosion and aquatic life impacts. They're doing it by creating stormwater agencies and developing a green infrastructure, which includes green roofs, rain gardens, tree cover, even downspout disconnection and porous pavement. Philly has a management plan for each of its five watersheds, and it created a Stormwater agency that is on the verge of revolutionizing how it handles the environmental problems from storms washing pollutants into rivers and lakes.

Philly is introducing legislation that will allow the stormwater agency to start billing customers based on how much impervious cover is on their property, rather than the old way of estimating your sewer bill based on water use. The city also wants to offer incentives to grow more green and less grey infrastructure-including a city council proposal for a 25% tax credit for installing a green roof (up to $100,000).

"We're looking at what our impacts are from the perspective of a fish," says Chris Crocket, Water Dept. Manager of Watershed & Engineering services. "The damage done to our streams over 200 years can't be fixed in 20 years. A whole watershed approach is our goal."

Philly is combining CSO replacement work (like Northeast Ohio's $2 billion, 20-year CSO project) with low impact development (LID) including repaving municipal lots and basketball courts at city parks with porous pavement, installing green roofs, and working with the city's building department to fast-track development projects that have an LID plan.

State legislation enabled the stormwater authority to exist under county control.

In Chicago, research efforts are leading to a permeability index of Cook County, says Steve Wise, Natural Resources Program Manager at the Center for Neighborhood Technology. GIS mapping and analysis will determine costs and hydrolic benefit of green infrastructure. CNT even has an online calculator that can estimate, at lot-scale, the cost and benefit of implementing green instead of grey infrastructure.

The non-profit group is working with Cook County on its green infrastructure plan. The county is proposing a property tax that will pay for a stormwater agency and projects like Chicago's Green Alleyway Program ? replacing 1,900 miles of back alleys with porous pavement.

"I call it un-paving the way to a solution," Wise says. "The goal is to reduce sewerage overflows, create more green space, restore urban land and increase real estate value."

Greening a city can make it more sustainable by allowing water to infiltrate into soil instead of running off into storm sewers (the more pavement, the bigger the sewer system).

Green roofs offer a big bang for the buck, says Dan Rees, a researcher with World Resources Institute in Washington, D.C. His organization mapped out green vs. gray space in Washington, and, using computers and models with unit area reduction factors, discovered that 2.5 acres of green roof (or 8 to 9 acres of trees) leads to 1 million gallon reduction in stormwater rushing into the system.

Meanwhile Milwaukee has a $900 million overflow reduction plan that includes a "stormwater rule" for 28 municipalities to reduce runoff on all properties greater than .5 acres. The city allows residents to disconnect the downspouts from their homes to flow into backyard gardens. Its Every Drop Counts campaign includes an $850,000 annual budget for an Urban Ecology Center that has sold 6,150 rain barrels for $30, $500,000 for porous pavement at city parks, planted 50 rain gardens and demonstrated rain gardens, green roofs and wetlands at municipal sites, including the sewer district's offices. They city has reduced its stormwater runoff by one-third.

Dean Marriot, director of Portland's Bureau of Environmental Services, explained the city's Green Streets program.

Some 45 streets that were deemed unnecessarily wide will be narrowed with curb bump-outs that double as rain gardens. The project, tested successfully on three city streets, will be concentrated in an area of town with a lot of basement flooding (it's expected it will reduce the flooding).

"The initial solution was to dig up the street and put in a sewer," Marriot says of the Siskiyou green street, which he estimates cost $500/year to maintain. "We put in a rain garden instead, and it takes all the stormwater on the street."

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