Pervious — you've heard the word, but don't know why it's important. Take a deep breath — not because it's hard to understand — but because breathing is what pervious is all about.
The way the soil breathes, of course. Pervious, or permeable, hardscaping is becoming so important that cities, such as Ashland, limit the amount of lot development that can be covered with an impervious surface, according to Amy Anderson, assistant planner with the city.
Need lots of parking area, but don't want your landscaping to look like a "concrete jungle?" Permeable bricks, flagstones and pavers are strong enough to drive or park on. But lawn lovers can opt for an even greener solution called grass or turf pavers. These porous interlocking grids are made of recycled polyethylene products or permeable concrete that look like a honeycomb with little hollow squares. Once the grid is laid, the "holes" can be filled with decorative gravel or topsoil and then planted with grass or ground cover.
Once installed and filled, your parking area is a beautiful and durable grass "pavement." The grid system protects the grass roots, prevents runoff and can serve as erosion control or soil stabilization. Grids filled with grass should be treated as a lawn and may need watering and/or mowing. For you low-maintenance gardeners, fill the grids with gravel. Karen Marshall of Naturescape Designs says she likes to use Pami Pebble, an attractive earth-tone mix available from local stone suppliers.
Check grids occasionally for clogging or poor drainage and sweep or vacuum to remove debris and keep the surface unclogged.
Pervious or permeable hardscaping allows water and air to penetrate the soil. That's important for a lot of reasons. In a natural environment, rain falls on the ground where soil and plants absorb and filter most of the water before it finds its way into nearby creeks and streams. Areas that are covered with impenetrable surfaces, such as buildings, concrete or asphalt paving, interfere with this process either by blocking it entirely and contributing to flooding or by diverting it as runoff. This runoff not only collects and carries pollutants and chemicals into the waterways but also erodes and washes away the soil.
Building with porous materials brings us closer to the natural cycle. It can be as easy as building your pathways of crushed gravel instead of concrete. Permeable surfaces include porous landscaping fabric instead of plastic around plants in your garden and pathways of gravel and bark mulches for areas not heavily traveled. For harder surfaces, like patios and driveways, a variety of new and beautiful products exist.
"Porous or permeable concrete has the structural strength of ordinary concrete," says Ron Andrews, dispatcher for Rock 'N' Ready Mix in Central Point. It is a special mixture of concrete that allows water to penetrate into the ground. It can be used for driveways, patios and sidewalks and he especially recommends it for areas around trees.
Pervious concrete was used in the new parking lot of S & B James Construction Company in White City. "We read about it and became fascinated by it," says Tom Hall, one of the owners. He hopes it will be the answer to tough new restrictions requiring developers to install "storm water retention systems" to clean and hold water before releasing it slowly back into the storm drains. His company is somewhat of a pioneer in the use of pervious concrete, having recently used it in a subdivision street in Ashland, another small parking area and a partial alley in Medford.
"If you want very, very smooth concrete, it's not," he adds, comparing its texture to a "Rice Krispie Treat."
And it can be beautiful, whatever your style. It can be stamped in designs and colored, poured as one unit or installed as individual pavers, bricks or flagstone in patterns like basket weave or herringbone. Installation should be over a gravel bed to allow drainage.
It is a little pricier than regular concrete, perhaps 10 percent, says Andrews. There are some maintenance issues as well. "Leaves, dirt and debris can build up and clog the surface and may need to be vacuumed or swept off," says Bret Bartholomy, general manager of Rock 'N' Ready Mix. Watch for poor drainage or puddling of water on the surface. He recommends using a broom or shop vacuum to clean off the surface and restore its porous quality.
Permeable hardscapes do double duty. They help protect water quality, reduce runoff and pollution and help prevent erosion and flooding. And they preserve your sense of style, whether on a meandering pathway or pervious concrete driveway. Pervious — you can breathe easy now.