“A combination of waterlogged soils and the river eating into the shoreline was causing the road to collapse,” says Bob Grese, the Arb’s self-effacing fifty-three-year-old director. Letting Nichols Drive fall into the river was not an option: “It’s the emergency entrance into the Arb and access to a main sewer line,” explains Grese (“GRAY-see”). “The city couldn’t risk not being able to get to that sewer line if it were to fail, and the university couldn’t risk not being able to get someone out of the Arb in an emergency. That’s the only one of our roads that a fire truck can access.”
The U-M and the city partnered on a $370,000 project to save the road. They hired Marty Boote’s firm, Environmental Consulting, to design three “vanes”—tapered piles of limestone boulders that curve out from the south bank of the Huron River like rhinoceros horns. Don Gray, a U-M emeritus professor of civil and environmental engineering who’s helped Grese carry out a series of innovative “bioengineering” erosion control projects, served as a volunteer advisor.
When a September storm dumped four inches of rain on the area in four days, Gray went out to see for himself how the vanes were working in high water. He says that though the stones were completely submerged, subtle patterns on the water’s surface made it clear they were still deflecting the rain-swollen power of the water away from the fragile bank.