MDOT goes sustainable with I-696 retaining wall

Thursday, April 8, 2010 | Source: metromode

The long, grey concrete walls along the expressway might not look like instruments of sustainability, but the Michigan Dept of Transportation will be changing more natural slopes into retaining walls in Metro Detroit's below-grade expressways.

MDOT is spending $9 million in federal stimulus funds to build a new retaining wall along I-696 between I-75 and Gratiot Avenue in Oakland and Macomb counties this spring. The idea is to prevent erosion, cut down on maintenance costs, and absorb more water runoff.

"We have erosion problems from mowing very steep slopes on the depressed freeways," says Nanette Alton, a registered landscape architect with MDOT. She adds that mowing these embankments creates deep ruts, not to mention even more carbon emissions from the mower.

Those ruts cause erosion during heavy rain storms. Topsoil washes into storm sewers, clogging them, and eventually making its way into the Great Lakes. That creates even more bad environmental spin-off effects.

"What we're trying to do is reforest the slope so we don't have to mow it anymore," Alton says. "That saves us a lot in maintenance costs."

After the walls are in, MDOT will fill the new, smaller green space with specially selected landscaping and organic compost. The compost absorbs several times its weight in water, preventing erosion and giving the 55,000 new plants time to take root.

The plants are a combination of native and invasive species. The best plants can not only survive the harsh conditions of living next to a freeway, but also block noise pollution.

"We need the most vigorous, hearty plants that we can find," Alton says.

Work is expect to wrap up in the fall of 2011.

Source: Nanette Alton, a registered landscape architect with Michigan Dept of Transportation
Writer: Jon Zemke