Slow the flow

Pervious concrete helps protect water by acting like an industrial wetland

The Rice Krispies Treat-like pervious concrete can help protect water sources.

The Rice Krispies Treat-like pervious concrete can help protect water sources.

Here’s what usually happens when water hits a paved surface: It puddles, then eventually flows to a gutter, down a storm drain, and ultimately releases itself—along with the oils, chemicals and other pollutants it brings with it—into nearby creeks, streams, rivers and lakes.

“It’s flowing too fast,” says Don Vetter of the Sierra Nevada Concrete Association. “If you’re able to percolate it, slow it down, the earth acts as a filter, thus protecting the river from total dissolved solids and nitrogen, which are the two things that cause algae blooms, which reduces oxygen and hurts the fish.”

Enter pervious concrete—a form of concrete that looks like a gray Rice Krispies Treat and allows water to flow through it rather than off of it. Bacteria in the soil beneath the concrete naturally absorb things like petroleum hydrocarbons that otherwise would go into a waterway.

“You look at people oversprinkling,” says Paulette Salisbury of the California Nevada Cement Association. “That’s a terrible use of that water. If it were running onto a pervious pavement, it would go back into the earth and other plants can use it, or go down into the aquifer as Mother Nature intended it.”

In addition to protecting water, pervious concrete is also a safer surface during the winter, as it prevents puddles from becoming ice.

Engineers and contractors expect to see more pervious concrete in the Truckee Meadows following a city of Reno ordinance passed this spring. The ordinance calls for stormwater runoff controls from non-point sources (i.e. rain, sprinklers) to be in place for new construction and retrofits. Those controls could include natural structures like rain gardens and swales, as well as structural controls, like pervious concrete parking lots, driveways and sidewalks.

The SNCA and city of Reno held a pervious concrete installation course for contractors and engineers in June to put them on a path to become certified installers of what can be a tricky substance to work with. A class for designers is being held in September.

“We’re hoping to help local industry be able to respond when this sort of job is required,” says Lynell Garfield, a Reno Public Works hydrologist. “There are currently no local contractors we can hire if we want pervious concrete, so we’re trying to provide the brain trust for that.”

With plans to retrofit the McKinley Arts and Cultural Center, where rainwater has been affecting its historical attributes, the city of Reno specified the use of pervious concrete. Using Truckee River Fund grant money and Clean Water Act funding, the city is using a series of techniques to prevent stormwater runoff from the building into the Truckee. They include rain gutters, a rain transport system, a rain garden, and a pervious concrete parking lot. It’s intended to be a strong demonstration site for reducing stormwater runoff.

“There are no other real examples of it in Reno,” says Terri Svetich, senior civil engineer of Reno Public Works. “That’s why we’re doing this now with grant funding, so we can pave the way to do more.” The project is taking place between now and this winter.

More ways to protect the water:

• Water lawns more often, but for shorter time periods. ex: three times each watering day, 10 minutes each time

• Xeriscape your yard to reduce the amount of water reaching storm drains