Porous street test in Salem, Oregon, paves way for future use

Daily Journal of Commerce (Portland, OR), Jun 20, 2007 by Alison Ryan

Rain fell Friday in Salem in a sheer drizzle - barely enough to dampen the roads, and definitely not enough to put the large-scale system of porous streets at Pringle Creek Community to serious work.

The narrow black lines that ribbon through the 139-lot housing development's 30 acres, developers say, will comprise the largest porous community street system in the United States. They're also, experts say, expected to be a test case for how porous paving works in a bigger way.

Porous paving uses are growing, but the idea is nothing new. Porous asphalt pavement has been in use, mostly in parking lot projects, since the 1970s. But over the past decade, said Jim Huddleston, executive director of the Asphalt Pavement Association of Oregon, interest - like it has for solar energy and natural building methods - has increased exponentially.

"I've seen the street and highway demand coming forward," Huddleston said. "So how are we going to design these systems to work on streets and roads rather than just parking lots?"

The team working on the Pringle Creek project has a few ideas. But installing a porous street system to serve the development, they told a crowd of 50 during a panel discussion last week at Pringle Creek, came with some challenges. Standard concrete installation is fairly straightforward, said Scott Erickson, president of Evolution Paving Resources, but with porous concrete the margin of error is very small - and the industry is still working to understand the differences.

"It was so new at 20 years," he said, "that it was really easy to screw up."

Keeping pervious surfaces from becoming impervious is key. In building Pringle Creek's streets, said Bill Lulay, project manager at North Santiam Paving, allowing for future infiltration meant doing things in a different sequence - a sequence that wouldn't compact the subgrade. Keeping pavement clear when home construction begins to muddy up the new streets, he said, will be another challenge.

"Everybody thinks it might work," Lulay said, "but until someone actually steps forward and does it, you don't know."

A test case in North Portland has shown - so far - that porous asphalt and concrete can withstand city traffic. In August 2005, the city installed a test project on four blocks of North Gay Avenue. The project, which uses different combinations of porous and standard paving materials, is Portland's first, said Bob Cynkar, community outreach representative for the city's Bureau of Environmental Services.

The four-block project also shows the higher cost of porous materials. Paving with conventional materials would have cost about $156,000; the porous asphalt and concrete demonstration, according to the city, cost about $240,000.

Porous streets do cost more, Pringle Creek developer Don Myers said. But they also, he said, allow 90 percent of the stormwater that falls on Pringle Creek to go back down into the aquifer.

"Yeah, you drive on them; you work on them," Myers said. "But the main reason we put them in was as a stormwater management tool."

The streets at Pringle Creek are just starting to get their lanes wet. And some of the permitting process - including getting Department of Environmental Quality approval for the streets' stormwater contributions and fire marshal approval for the narrow streets - was tough, said Chuck Gregory, a civil engineer at W&H Pacific. But, he said, he sees many more applications for the work that's been done at the new community.

"I didn't realize at the start," he said, "how significant this was going to be."