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.

Join the Conversation


  1. Are the landowners in the
    Are the landowners in the area getting assessed for this?

    I think the normal arrangement is that landowners with property abutting the alley have to pay 1/2 the cost while the city pays the other half.

    Is the city doing this project gratis? If “yes” why was that alley chosen and not other places in the city?

    If the normal arrangement is being followed, are the landowners paying the extra cost involved and did they approve it? Or is the city using conventional figures to assess landowners and they, in turn, are paying the difference between the “green” solution and the conventional solution?

    The city’s paying for it with federal block grant funds and general obligation bonds. The theory is that since this is an experiment, the residents shouldn’t be stuck with the bill for something that may not work.
    Also, a substantial portion of the alley faces a city park — so the city would have to pay for that part itself anyway.
    BTW, there are two east-west alleys on this block, and the paving project only involves the more southerly one.
    — Bill

  2. Green Alley Handbook
    CDOT worked with a local Landscape Architecture firm to develop the “Green Alley Handbook” which can be viewed by following this link:


    The handbook does a great job of explaining, in laymen terms, what the intent of the green alley pilot program is, and how it will benefit residents and the environment. Chicago’s green alley program, along with the Green Alley Handbook, was also featured in this month’s Landscape Architecture magazine and has won a national award from the American Society of Landscape Architects.

    I wish that the city had incorporated some of these techniques in to my alley when it was repaved in 2005, but at least they’re going to give it a try now. This is a great way to improve the awful condition of some alleys in our city, and improve the overall stormwater runoff quality that gets ultimately discharged back into Lake Michigan.

  3. green alleys
    i have to guess that the trough down the middle of the alley will be 5 INCHES deep not 5 feet. think of all the small cars and dogs lost, garbage trucks marooned, baby strollers swallowed up. good heavens.

    unless of course the trench is only an inch or so wide.

    bill: please enlighten me.


    I believe they’re talking about a 5 foot deep trench — probably filled with gravel or something like that — under the surface of the pavement. (Even a five inch drop in the surface of the alley would hang up small cars.)
    — Bill

    1. Green alley – drainage
      The drainage trench down the middle is covered by the permeable concrete paving. Water flows “through” the tiny openings in the concrete and is then collected in the trench underneath. On the surface, there won’t be any visible drains or openings, though the alley will be built so that it slopes to the center to ensure that water moves away from homes and into the drainage system.

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