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Bike path a test project for permeable pavement

Cyclists in Spokane’s Lincoln Heights and Glenrose neighborhoods may have a little bumpier ride starting next year, but at least it’ll be drier.

Construction is set to begin in 2015 on what will be one of the city’s more modern bike lanes, stretching for almost a mile on Havana Street from Glenrose Road to 37th Avenue. It will be made of permeable pavement, which is rougher than standard asphalt because it isn’t made with sand and other fine particles. By being porous, it allows stormwater to drain through, instead running over, its surface.

During inclement seasons, porous asphalt won’t allow any water to stay on its surface and freeze into a harrowing skin of ice.

“That’s what we’re hoping. That’s what they found in other parts of the county,” said Marcia Davis, a principal engineer with the city’s integrated capital management program. “What they found is it works great, except when you get that frozen mist. But Spokane is really unique. We have things in common with a lot of places, but we still wanted to do this as a pilot.”

The city is planning to use the pavement to help divert stormwater from its treatment plants, part of its plan to stop toxins from entering the Spokane River.

Instead of letting dirty stormwater flow into drain pipe and potentially into the river, the water seeps through pores in the pavement into the gravel and dirt beneath the street, where it is filtered through the soil and treated on site.

Permeable pavement is fairly new, but it has been used regionally for years. Pringle Creek, a sustainable development in Oregon’s Willamette Valley, used porous asphalt for all its roads in 2007. Issaquah, Bremerton, Snohomish County and Washington State University’s Puyallup campus have all successfully used permeable pavement in the last decade.

Concerns persist about permeable pavement’s durability. Worries over the asphalt’s pores getting clogged by fine dirt, and its strength in the face of countless cars and trucks trundling over it, aren’t easily dismissed. Bike lanes are considered a preferable way of using the porous surface because bikes don’t wear on the road as much.

Still, the city hopes to use the pervious roadway in more situations and is pairing with Gonzaga University to test its durability and its need for maintenance in the Logan neighborhood on Sharp Avenue between Pearl and Cincinnati streets.

One section of the road will be completely made of porous asphalt. Another will use the material only on the street’s bike lanes and parking spaces. The intersection at Addison Street will be made of pervious concrete, another type of permeable pavement.

“We’re using that as a demonstration project,” Davis said. “We’re working with Gonzaga University to come up with standards for design, construction and maintenance.”


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