Conservation Notes: Pervious asphalt installed in Chisago County

This patch of pervious pavement covers a portion of a parking lot at the Waters Edge Condominiums in Lindstrom. Photo supplied

This patch of pervious pavement covers a portion of a parking lot at the Waters Edge Condominiums in Lindstrom. Photo supplied

Something new has come to Chisago County.

The first pervious asphalt was installed in the county at the end of September.  It is located in a portion of a parking lot at the Waters Edge Condominiums in Lindstrom.

Pervious asphalt appears the same as normal asphalt, but functions much differently.  It still supports traffic, but it allows water to run through the parking lot instead of over it.  Pore spaces left in the asphalt allow water to drain through to layers of rock beneath the parking lot.  These layers help hold water while it soaks into the ground and filters chemicals and pollutants out of the water as it flows through the layers.

There are other benefits of pervious asphalt as well.  It dries faster after rain and snow removal.  Ice doesn’t build up on the surface because water is able to melt and drain away through the pore spaces.  This eliminates the need for de-icing salts and reduces ice-related injuries in the winter.

There are several examples of pervious asphalt, as well as pervious concrete and pervious pavers, in other areas of Minnesota, especially in the Twin Cities area.  The concept of pervious surfaces is not new; in fact, states on the East Coast have been using the technique for more than 40 years.  Many of these first projects are still functioning at full capacity, meaning pervious pavements have a long practice life, providing many years of benefit.  To continue functioning at full strength, a twice-yearly vacuuming is needed to keep the pore spaces open so water can continue to infiltrate.

For more information about water quality improvement projects happening in the County, visit the Chisago SWCD’s website at www.chisagoswcd.org.

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