Here’s an engineering riddle: What has the texture of a Rice Krispie treat but is strong enough to support a fire truck? No, it’s not a snack for Superman. It’s permeable pavement.
Permeable pavement, also commonly referred to as pervious or porous pavement, is often created using either asphalt or concrete. It can also include a wide variety of materials such as open-joint paving blocks (called pavers), decomposed granite or gravel pavement, synthetic turf, crushed glass and even wooden decks or boardwalks. The main advantage of all these options is the ability of the material to allow water to flow through it. According to SustainableConcrete.org some pervious concrete, allows “over 300 inches of water per hour to pass through.”
Porous pavement has been around for a few decades and its applications are increasing. Primarily developed as a form of stormwater control, it allows rainwater to seep into the ground instead of contributing to storm drain run-off. Moisture prone states have been using this technique since the 1970’s to control runoff, erosion, flooding and to help recharge aquifers close to the surface.
This technology is gaining new ground in thirsty states like Arizona and California. ConcreteNetwork.com noted that western states have shown an interest in using pervious concrete for its environmental benefits. “For example, pervious concrete is helping communities in California and Washington restore groundwater supplies and reduce pollution of coastal waters, which can endanger fragile aquatic ecosystems and even swimmers.”
Here in Arizona, a number of communities throughout the state have employed pervious pavement in Green Building applications. Flagstaff featured Arizona’s first use of pervious concrete at a parking lot near the Applied Research & Development building, an award winning LEED building at Northern Arizona University.
The City of Scottsdale installed pervious concrete parking at a Park & Ride on Thunderbird and Scottsdale Road in 2014. Scottsdale Green Building Project Manager Anthony Floyd noted several benefits from using the material. He specifically mentioned how this application acts as an alternative retention basin and therefore re-appropriates land that ordinarily would be dedicated to a retention basin. Also the large pore space or “voids” within the material helps mitigate the heat island effect common in urban areas.
Gary Meyers, Senior Project Manager for the Scottsdale Park & Ride project stated the project has been “well received” and gave the technology a “thumbs up” with “no performance issues to date.”
In addition, Arizona State University (ASU) installed pervious pavement at a parking lot located at the ASU Art Museum in Tempe in 2007 and the City of Glendale installed 140,000 square feet for the Glendale Park & Ride in 2008.
Progressive Hardscape of Phoenix was the primary contractor involved in the Scottsdale, Tempe and Glendale projects. Mike Riggs, General Manager of Progressive Hardscape noted that the cost of permeable concrete is coming more in line with conventional concrete and the applications are increasing. Riggs shared that, depending upon project size and location, the unit cost of permeable concrete can range between $6 – $8 per square foot; about 20% more than typical concrete.
To really determine the viability of using permeable pavement as an alternative to conventional materials, the overall project goals need to be assessed. When considering the environmental benefits, the ability to re-appropriate the land as well as the cost of typical stormwater management systems, permeable pavement can often be a viable economic alternative.
All this is encouraging news for drought prone states like California and Arizona where water retention and infiltration is a key component of economic growth.
– Sandra Hurlbut