Pervious concrete may eliminate need for storm drains

Published 27 June 2009

A Minnesota town experiments with a new concrete paving method that lets rainwater pass right through the street surface to prevent damaging runoff

The Obama administration has allocated billions of dollars of the stimulus package to shoring up the aging U.S. infrastructure. There is an interesting infrastructure experiment going on in Minnesota, as Shoreview, Minnesota, is betting on a new “green” concrete paving method that lets rainwater pass right through the street surface to prevent damaging runoff. Pervious concrete — made of gravel and cement minus the sand that gives regular concrete its impenetrable density — has the porous quality of a Rice Krispies bar. Because it will allow water to drain straight to the ground below, Shoreview will install about a mile of pervious concrete streets without storm sewers in a neighborhood on Lake Owasso.

This $1 million, all-in bet on the new pavement technology has many cities looking at the Shoreview experiment, wondering whether they might try the same approach. “This is the first complete commitment to using a pervious pavement on a residential street replacement” in Minnesota, said Shoreview Public Works Director Mark Maloney.

Minneapolis Star Tribune’s Laurie Blake writes that over the past five years, other Minnesota cities, including Minneapolis and Richfield, have been experimenting with pervious concrete on parking lots and other hard surfaces, hoping for better storm-water management. But in Shoreview, “We are completely replacing a storm drainage system with a pavement that will infiltrate” water to the ground, Maloney said. Tests “have shown that it is as durable as standard concrete for low-volume roads,” Maloney said. “The science behind that is very sound and supported.”

There are, however, few examples of a local government saying “this is going to be our pavement in lieu of a sewer system,” he said. “We won’t have catch basins, pipes and (settling) ponds.” Cities are finding that piping storm water to settling ponds eventually fills the ponds with sediment that has to be dredged out and disposed of as toxic material, Maloney said. If there is an alternative that lets soil naturally filter out pollutants as rain soaks into the ground, cities are keenly interested, he said.

That possibility sold the Shoreview City Council on the project. Some residents questioned how the unusual pavement would look and how it would perform under severe weather conditions. They also asked how it might feel to someone who fell off a bike onto the surface. Despite such questions, council members were eager to use the pavement to protect nearby Lake Owasso, whose water quality has been declining. “This community is very