Create an Eco-Friendly Driveway

Photo: istockphotos
Look beyond cement and blacktop to prevent harmful rainwater runoff

Most urban and suburban driveways are hard concrete or blacktop. They are built thick and built tough. Tough enough to stave off the heavy tread of heavy-duty tires beneath heavy-duty cars and trucks. But while concrete driveways do provide a smooth surface to park your car, play some recreational b-ball or teach kids how to ride a bike in safety, one thing they don’t usually do is absorb water.

Instead, rainwater runs off the driveway, ending up in storm drains and sewers or water treatment plants. This can be a real problem in urban areas, where pavement often out-landscapes green spaces. The subsequent water overflow in sewers and treatment plants can force raw sewage to be dumped into rivers and streams. Contrarily, because of the concentration of water in storm drains, small streams often do not get enough water and dry up between storms, essentially starving out delicate watersheds.

One driveway may not seem like it makes much of a difference, but if you've ever watched storm water run down your driveway to join the hundreds of gallons running down the street along the curb, you can guess how much good water—water that would’ve otherwise gone into your landscape— is lost to the dark mystery of the municipal drainage system.

Reduction of water runoff is the door to an eco-friendly driveway. And the key to that door is porosity. If water can get through to the surface beneath your drive, it can reenter the water table from whence it came and continue on its natural path through the Earth's life-giving circulatory system.

There are two good ways of doing this: porous pavement or no pavement at all.

Porous Pavement

Porous pavement is like concrete that doesn't sweat the little stuff. As you probably know, concrete is usually made up of cement, crushed rocks and sand or other fine material. Porous concrete is made of essentially the same stuff, but leaves out the finer materials. This leaves voids between the aggregate within the pavement, enabling water to pass through to a stone reservoir beneath. That stone slowly allows the water to percolate down into the soil.

In the past, permeable pavements have had problems with durability, failing because the ingredients did not bind together properly. However, some major technological advancements have occurred, and porous pavements are now being used in all sorts of applications, from driveways to cart paths to walkways. This 2005 article from the journal Stormwater gives detailed information on the many different types of porous pavements.

Green Grass

Of course, the logical opposite of a paved driveway would be an unpaved one, making it a simple extension of the lawn. Unfortunately, over time, ruts would form and the driveway would turn into an untidy mess of mud and standing water. That's why pavement is so convenient in the first place. In the effort to find a happy medium, innovators developed structural lattice.

Made from plastic or cement, this approach provides excellent load-bearing strength while preventing compaction, which also helps to protect plant root systems, which in turn makes for even better drainage. The pavers have large, typically uniform grids through which vegetation can grow— think of them as grass pavers. They drastically reduce rainwater runoff compared to impermeable surfaces.

I had the pleasure of seeing one of these driveways in action last fall at the Build It Green! Home Tour in Portland, Oregon, a city well known for its rain and storm water runoff issues. While standing at the front entry to a particular home I watched for five minutes as rain pounded the permeably-paved driveway, not a puddle formed and no stream of water funneled out into the street. It was at that time the eco-friendliest driveway I had ever seen (although I do not know where the pavers were sourced from).

As I said earler, there are plastic and cement options available. The plastic is made of high-density polymers and is incredibly strong and long-lasting. I simply prefer cement because it can be recycled easier. And speaking of grass pavers, check out Grasspave² from Invisible Structures, Inc. This variation is load-bearing and looks just like a sodded lawn, using integrated plastic latticework to prevent compaction while still allowing water to fall through.

Dan Harding is a well-versed veteran of solar critique, commentary and reporting.  He has published well over 1,000 articles on a wide variety of solar industry topics, ranging from cutting-edge technology and gadgetry to political satire and powerful editorials. CalFinder is proud to tout Dan as our resident solar expert. He holds a B.A. in English from Michigan State University, and enjoys reading, writing and home construction.