Rain washes clean in Burns Park porous alley project

When it rains, it pours in Washtenaw County. Rain falling onto impervious pavement courses into storm water systems which carry pollutants such as motor oil that wash off the county's roads into creeks and the Huron River. To better manage capacity in the storm water system and raise water quality, permeable pavement installations that allow rainwater to soak into the ground, where natural filtration occurs before rainwater makes its way into the groundwater, are becoming increasingly popular eco-conscious projects in municipalities.

As such, a porous alley is planned for Ann Arbor's Burns Park neighborhood. Nick Hutchinson, project engineer for the city of Ann Arbor, says the rebuilding of the 12-foot wide residential alley spanning between Lincoln Avenue and Martin Place is expected to commence this August and should take no longer than one-and-a-half months to complete.

The alley design isn't complete yet, but Hutchinson's cost estimate is around $165,000. The cost will be funded via a low-interest loan from Michigan's Dept of Natural Resources and Environment, which also has a 50% loan forgiveness offer through its State Revolving Fund. The remaining half will be covered by the city's storm water fund.

Permeable pavement is costlier than typical resurfacing projects mostly because of the need to build underground stone beds to hold water before it can filter into the ground. These installations work particularly well in areas with well-drained, sandy soils, Hutchinson explains. "They can be built in other places too, but in places where you've got clay you're probably not going to get the water to go into the ground. It's more of a temporary storage of the water before filtering and releasing into the storm system. We have very good soil conditions in this project and we're expecting to get all of the water going into the ground instead of going into the storm system."

Hutchinson cites the city of Chicago's Green Alleys as instances of successful porous alley projects. While the Burns Park neighborhood will be the site of the city's first porous alley, this is not the first time the city has experimented with permeable pavement. Porous pavers were installed on Easy Street, and Sylvan Avenue was reconstructed out of porous asphalt last summer. The city is monitoring the hardiness of these installations; it's still too early to tell how well they will hold up, although research has been encouraging, he adds.

"I think it's definitely the wave of the future. We're going to see more and more porous pavements, especially if the ones that we've put in so far perform well."

A public meeting to explain the Burns Park Porous Alley project is scheduled for tonight, Wed. Jan. 19 at 7PM, at the Burns Park Elementary School cafeteria, 1414 Wells St. For more information, email nhutchinson@a2gov.org.

Source: Nick Hutchinson, project engineer for the city of Ann Arbor
Writer: Tanya Muzumdar