The harsh truth about hardscape

Kick impervious surfaces to the curb

Bill Goggia of A & A Concrete demonstrates how water seeps right through a pervious concrete walkway on the Chico State campus.

Bill Goggia of A & A Concrete demonstrates how water seeps right through a pervious concrete walkway on the Chico State campus.

PHOTO courtesy of chico state

Sustainable Space columnists Lori Brown and Greg Kallio are professors in the College of Engineering, Computer Science and Construction Management at Chico State University.

Here comes the rain
With our area finally experiencing a fairly significant storm event, this is a good time to check out the city’s obvious lack of natural or vegetated open space.

Look around. Chico certainly has a fair number of trees, but most of them are growing in a minimal amount of land or in planter boxes. Downtown is primarily made up of buildings and a sea of eco-unfriendly hardscape—parking lots, roads, sidewalks, patios, pathways and other paved areas. Even our somewhat newly remodeled downtown park has a disturbingly large quantity of concrete as its main surface with a few rather inaccessible grassy areas tossed in for a greener look.

Runoff blues
As the stormwater hits these surfaces you don’t have to imagine what is happening to it; you can watch the water run along the gutters and into the city storm drains. These drains flow to either a creek or the city of Chico’s municipal water-treatment facility. Very little, if any, of the rain in these hardscape areas actually filters back into the earth, as it is supposed to do.

If only the California Stormwater Quality Association (CASQA) handbooks were around for our forefathers and city developers, maybe they would have enrolled in a few green-building and sustainable-design classes through the UC Davis Extension program. A couple of the courses: Sustainable Water Resources Management in Site Design and Development; and Pervious Pavement: An Eco-Friendly Hardscape (this one would have helped to pave the way to creating a more sustainable downtown).

Impervious perils
The two most common—and cheapest—materials typically used for covering land to create hardscape surfaces are concrete and asphalt concrete (AC). Both materials create impervious surfaces that obstruct the natural hydrology of rainwater and its ability to seep back into the ground. The natural water table in the region goes lower as a result, leading to an environmental imbalance.

Using alternative paving materials designed to be pervious has a measurable impact on the ability of stormwater to be filtered and cleaned, and therefore contributes to recharging the groundwater with purified water. Keep in mind that this is the stuff we drink!

Earth-friendly alternatives
Contractors and developers working on commercial projects being built from the ground up should consider the environmental impacts of their site design, paying special attention to the amount of impervious areas. One eco-friendly option to consider is replacing them with pervious concrete, permeable pavers or grass pavers.

While it takes some work, there are significant benefits to jack-hammering out the concrete surrounding buildings and homes, and replacing it with alternative sustainable paving materials. In addition to helping contribute to better stormwater management, you also could save energy by being surrounded by less hardscape and more vegetation.

Imagine if the next time you walked through the downtown Thursday Night Market all of the concrete and AC in the area was replaced with open-grid grass pavers. Do you think it might be just a little cooler? It would certainly be more beautiful!