"We started getting calls about porous asphalt pavements," recalls Dave Vogt, a Bend, OR-based contractor. "So in 2008 we decided to take the lead in central Oregon and show this market how porous asphalt could solve the stormwater management problems we're facing."
Vogt succeeded. Last year his firm, Hooker Creek Companies, placed two test sections of porous asphalt pavement. They handle stormwater well, so Hooker Creek upped the ante by constructing the first full-size porous asphalt parking lot in that part of the state at the firm's new equipment rental store in Redmond.
Today, the firm gets calls to present the technology to various forums of contractors and engineers. With that, porous asphalt is a new market for Hooker Creek.
Just as Hooker Creek's business model worked well for them, so it can work well for other asphalt contractors. It's a good idea to start by building a successful project or two. Then you have a demonstration project to showcase to others. Word spreads, you make some presentations, engineers and environmental authorities like what they hear, and you're up and running.
"The best promotional tool for porous asphalt is the product itself," says Jim Huddleston, executive director of the Asphalt Pavement Association of Oregon.
How it works
Porous asphalt pavement is not new, but it's new to many asphalt contractors. Asphalt has a successful track record of porous pavements dating back to the late 1970s. Cahill Associates, an engineering firm, has been involved in the design and construction of more than 200 porous asphalt pavements since the 1980s.
Cahill has reported no failures on pavements for which proper design and construction procedures were followed, according to Kent Hansen, P.E., Director of Engineering, National Asphalt Pavement Association (NAPA).
Porous asphalt pavements are designed for dual duty. They provide pavements for parking and roads and serve as stormwater storage and infiltration systems.
What's more, the demand for porous asphalt pavements is growing because they offer site planners and public works officials the opportunity to manage stormwater in an environmentally friendly way, says Hansen.
From the bottom up, the standard porous pavement structure consists of:
- An uncompacted subgrade to maximize the infiltration rate of the soil.
- A geotextile fabric that allows water to pass through, but prevents the migration of fine material from the subgrade into the stone recharge bed.
- A stone recharge bed consisting of clean single-sized crushed large stone with about 40 percent voids. The stone chamber serves as a structural layer and temporarily stores stormwater as it infiltrates into the soil below.
- An optional stabilizing course or "choker course" consisting of clean single-sized crushed stone smaller than the bed's larger stone. That stabilizes the surface for the paving equipment.
- An open-graded asphalt surface with interconnected voids that allow stormwater to flow through the pavement into the stone recharge bed.
Reaching the specifiers
Grimes Asphalt and Paving Corp., of Grimes, IA, has become a leading marketer and builder of porous asphalt pavements in their state. The firm built its first porous asphalt pavement - a nature trail in suburban Des Moines - in 2004. Since then, Grimes Asphalt has installed seven porous asphalt projects, says Stephen Moyna, a project manager at the firm.
Customers for porous asphalt are both public agencies and private businesses. Grimes Asphalt's first project was built for the Metro Waste Authority's Regional Collection Center in Bondurant, IA. The next was a parking lot for Luther Park Center, an assisted care center in Des Moines. The customer was a private developer.
"We had done other standard paving projects for this developer," says Moyna. "They had heard that Grimes was doing porous asphalt, and they wanted to be environmentally friendly. So we assisted with the design and construction of the parking facility. Then we put up a sign at Luther Park that graphically illustrates how porous pavement works."