A little less than two years after it was installed, the temporary water control structure next to the Otsego Township dam is being disassembled.
Completed in March 2016, the structure was built adjacent to the concrete spillway of a former hydroelectric dam owned by the Michigan Department of Natural Resources. At more than 100 years old, DNR officials feared the dam, next to River Road near 106th Avenue, would fail soon, spilling PCB-contaminated sediment downriver.
The DNR’s dam manager, wildlife biologist Mark Mills, said, “By putting that structure in, we prevented the dam from failing all the way.
“And we allowed for the manipulation of the water level, which has been a great help to this project, to get water off the banks so they can restore it.
“And it allows for us to put the river back to its original channel,” which matches with the control structure’s current location on the east side of the river.
Because the temporary water control structure was only designed to last three to five years, the U.S. Environmental Protection Agency ordered a time-critical cleanup for approximately 1.7 miles of the Kalamazoo River, covering both the riverbanks up river to the M-89 bridge just west of Otsego.
The project was similar in scope to the Plainwell Dam project, which ran from 2007 to 2009. That project worked on an area from the former dam, which was removed, on the river north of 12th Street in Otsego Township to the Main Street bridge in Plainwell.
The current project in Otsego Township so far has removed 39,875 tons of sediment from the riverbed, banks and nearby flood plain that contain minimal amounts (less than 50 parts per million) of the carcinogen PCB. Another 103.91 tons of sediment with higher PCB levels has been removed to an EPA landfill for contaminated waste in Belleville.
The project, which began in summer 2016 is expected to wrap up this summer. The project is approximately 90 percent complete, having spent $1.3 million of its budgeted $1.4 millionm, a cost born by the companies EPA holds responsible for the pollution, Georgia-Pacific, Weyerhaeuser and International Paper.
Milbocker and Sons Inc. made quick work of removing the temporary water control structure. Work began the end of January; by last week, the catwalk across the structure and several H-beams that supported it had been removed. Last Thursday they were at work prying out the sheet pile strips of metal that formed the east cutoff wall.
That part of structure prevents water from eroding beneath the flanks of the structure. It also provides a base to support the portions above it.
The sheet pile is approximately 35 feet long, most of which is driven down through the riverbed into the clay sediment beneath.
See two photo albums on the Union Enterprise’s Facebook page that show how a clamp was attached to the top of a pair of the strips of submerged sheet pile.
The clamp vibrates—the concussive force of which is audible 100 feet away—the sheet pile while the crane to which it is attached pulls up. Over the course of 5 to 10 minutes, the sheet pile is tugged approximately 5 feet out of the water.
Next, the clamp is repositioned and some secondary supports are added, and the sheet pile is dragged gradually out of the muck and laid aside to be refurbished and reused.
Cam Baron, construction management with AMEC Foster Wheeler, now the Wood Group, said, “They’re on schedule, maybe even a coupe days ahead. After they get this done, they’re building the crane pads on the island so they can pull out the other side.”
There is ground between the former dam and where the temporary water control structure bypassed it.
Mills said the DNR expects to obtain funding to remove the former dam’s crumbling concrete spillway soon, hopefully coinciding with the end of the EPA cleanup.
“The DNR requested a grant through the EPA through the Great Lakes National Programs office,” Mills said. “We are expecting that grant to allow us to demolish that old concrete spillway. And as the project here finishes up, they’ll do the restoration work for that site.”
He said the former dam’s spillway will block water but will allow for the kinds of floodwater events expected to occur approximately every two years to spill over.
“There will be public access over there,” Mills said. “We expect it to be restored to kind of a backwater wetland and floodplain forest.”
Baron said the temporary water control structure will be removed and the EPA cleanup will be wrapped up this spring, hopefully in April.
Mills said, “All the work on restoring the area is scheduled to be completed by August. By the end of summer, I should be able to lift the restriction on entry.”
The DNR closed the river and all public access points when the EPA project began in summer 2016.
“So, they’ll be open by hunting season... which is very exciting,” Mills said. “Get the public back in there, enjoying the river. They’ll be able to float from downtown Otsego all the way to Trowbridge dam uninterrupted, along with the fish.”
He said it was satisfying to see long-term river cleanup and restoration efforts come to fruition.
“Anybody who’s worked on a project that’s been difficult like this for the past decade, to finally see some of these things to occur is just phenomenal,” Mills said. “But it’s the right thing for the river, it’s the right thing for the people, right thing for the land; it’s why we do it.”
Contact Ryan Lewis at rmlewis@allegannews.com or (269) 673-5534.
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