Evanston aldermen tonight are scheduled to award a contract for what’s being called a “green” alley paving project.

And, no, it doesn’t involve the use of green-tinted concrete.

Instead, the plan is to use a permeable concrete pavement that has pores or openings to allow water to pass through the surface and percolate into the ground.

Public Works Director John Burke says the concrete will be eight-inches thick, and the alley will have a five-foot deep trench down the middle.

That should allow stormwater to flow into the ground — and eliminate the need for drainage pipes connected into the city sewer system.

While the design eliminates the cost of the pipes, it still is expected to cost 10 to 15 percent more than a traditional concrete alley with conventional drainage.

But Burke says the environmental benefits are significant and the cost of the porous concrete product is expected to drop over time as demand for the product increases.

If the product was widely used in the city it would significantly reduce demand on the city’s sewer system.

The green alley approach has been used at several sites in the City of Chicago, and Burke says Evanston city staff who designed the new project in-house visited some of the Chicago sites.

The alley scheduled for the test project is north of Dobson Street and runs from Ashland Avenue east toward Asbury Avenue.

The staff is proposing that the contract, for $259,000, be awarded to MY BAPS Construction Corporation of Chicago, a minority-owned firm that has done similar project in Chicago.

Update 9/23/08: The City Council approved the project unanimously Monday night.

Bill Smith is the editor and publisher of Evanston Now.

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