Landscape Architect Articles

Going Green with Pervious Concrete05-19-08 | News

Going Green with Pervious Concrete

Pervious concrete recharges groundwater, resulting in zero discharge of polluted runoff into waterways, lessening of urban flooding, improved health of adjacent trees, on-site bioremediation of pollutants, and a reduction or elimination of the need for storm drain infrastructure.

Manhattan Beach, Calif. has taken a significant step toward protecting the earth?EUR??,,????'???s resources by installing pervious concrete in nine city parking lots. Pervious concrete pavement is a permeable, porous material that is often said to resemble a rice cake. Pervious pavements help improve ocean water quality by allowing storm and nuisance water to infiltrate into the ground, decreasing the amount of runoff carrying pollutants.

The Manhattan Beach pervious parking lot project was made possible by a $900,000 competitive grant awarded to the city from the Calif. Water Resources Control Board. Pervious concrete is not a new material. It was originally used 100 years ago in Europe as structural insulation in buildings. It has been successfully used as a paving material in Europe for the past 80 years and in the American Southeast for the past 20 plus years.

?EUR??,,????'??Unlike conventional concrete, you can?EUR??,,????'???t do slump or compact tests with pervious, so it?EUR??,,????'???s a little harder to predict,?EUR??,,????'?? explains Ish Medrano, engineering technician for Manhattan Beach. ?EUR??,,????'??Although pervious concrete has been used in many other cities, it?EUR??,,????'???s our first time using the material, so there is a bit of a learning curve.?EUR??,,????'??

One of the challenges faced by the Manhattan Beach team over the course of construction was the tighter tolerances required by pervious concrete as compared to traditional concrete. ?EUR??,,????'??Pervious concrete needs to be placed, covered and cured more quickly,?EUR??,,????'?? says Medrano, ?EUR??,,????'??We worked with the police and fire departments to close off the road so the trucks would be able to get here on time. We timed the trucks so they came just when we needed them. And we used a conveyer belt to pour the concrete so it was in constant motion.?EUR??,,????'??

Medrano adds, ?EUR??,,????'??Another example of something we hadn?EUR??,,????'???t figured on is that after the pervious concrete has dried, it takes two coats of paint to draw the street markings, where usually it takes one. This is because of the irregular texture of the cured pervious concrete. Little things like this that we?EUR??,,????'???re learning will help us know how to approach the next pervious project, and sharing our experiences with other contractors, owners, and municipalities who embark on pervious concrete projects can be helpful to them.?EUR??,,????'??