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Green Building Curmudgeon

Helping the Environment, One Drop at a Time

Installing porous masonry pavers instead of concrete or asphalt is one way to reduce runoff and related pollution.

There is a lot of discussion about pervious paving and its contribution to the environment. Standard paving materials collect pollutants like oil, chemicals, and rubber tire particles from vehicles, pesticides, and dirt, only to have rain wash it off into our waterways, degrading our fresh water supply. Natural landscapes allow rain to percolate down through the soil, taking various pollutants with it, filtering and cleaning them as they flow down, typically arriving clean and clear by the time they reach the water table. We do need hard surfaces to walk, bike, and drive on, so what is the solution? Pervious paving to the rescue Available in many forms, pervious paving provides us with a surface both structurally sound and porous to water. Pervious concrete is similar to the standard product, but it’s made with smaller aggregate and no sand. The result is roughly the texture of a Rice Krispy treat, with open pockets that allow water to flow through the surface to the ground below. Usually placed over about 12 inches of gravel and a geotextile base, pervious concrete can absorb all but the most severe rain events, eliminating almost all water runoff wherever it is installed. Other pervious products include expanded plastic mesh filled with grass and porous paver stones installed over a gravel base.

Do your part Reducing the amount of runoff from your project can provide additional points in almost every green-building program, it can help with building department approvals when you have to retain water on your lot, and it helps keep pollutants out of streams and rivers. The initial cost is higher than standard paving products, but like most things green, we get what we pay for. Once we stop looking at first costs and consider what our choices are doing to the environment as a whole, pervious products much more sense. And they’re fun to pee on, too.

2 Comments

  1. Robert Guico | | #1

    Pervious pavement in harsher climates
    I'm considering budgeting for a pervious driveway (and perhaps a path to the front door), but I haven't seen much research done in the "snow and ice" area.

    Up here in the Chicago area, snow and ice are inevitable. It's easy to push snow off an asphalt driveway with a shovel, but how will this material handle shovels and snowblowers? Will it be more or less likely to heave and crack during the freeze-thaw cycle?

  2. User avater
    Carl Seville | | #2

    Cold Climate
    Pervious concrete works in cold climates as long as you have enough gravel below it to hold whatever rain falls before it freezes. This will vary based on your climate. There are installations in Chigaco as well as New Hampshire.

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