This photo from a drone looks southeast over the Trowbridge Township dam. The DNR intends to set its removal in motion this summer by temporarily shoring up the deteriorating structure in advance of a larger removal effort. (Photo courtesy DNR)

DNR targets Trowbridge dam for removal next

By: 
Ryan Lewis, Editor

A nearly $3 million state grant announced this week will begin the lengthy process of removing the Trowbridge Township dam.

“The dam is deteriorating at an increasing rate,” said Mark Mills, a wildlife biologist with Michigan Department of Natural Resources, the source of the grant. “We’re seeing it visually, with water moving through areas where it shouldn’t be and erosion on the embankments.”

Completed in 1898, Mills said it powered the first long-distance transmission line for electricity to feed Kalamazoo. It sits just east of 26th Street. He said it shut down in the early 1960s as sediment waste from paper mills gathered behind many hydroelectric dams, reducing their water capacity.

That sediment is the problem.

“We’re not worried about the dam failing and a tidal wave of water,” Mills said. “100 percent, our concern is the uncontrolled release of contaminated sediment in the impoundment.”

PCB, a carcinogenic byproduct of the paper manufacturing process, was dumped into the river for decades along with other manufacturing waste. As parts of the riverbank and dam erode, PCB-laden soil slips into the water, where it collects and concentrates in fish. Advisory signs posted throughout the Kalamazoo River warn against eating fish caught in the river.

The DNR’s Dam Management Grant Program announced Tuesday it was dedicating $2,940,775 for a project to stabilize the Trowbridge dam through its Wildlife Division; Mills applied for $350,000 last year and the project was also awarded supplemental funding set aside last year for projects like this.

A DNR press release said, “Trowbridge dam is the highest-priority dam removal project in the state due to public safety concerns related to its poor condition and high hazard rating.”

The project will be similar to another recent project, the removal of the Otsego Township dam. There, a temporary water control structure was built in 2016, and the U.S. Environmental Protection Agency stepped in afterward to remove contaminated sediment and remove the remaining dam structure. Then the temporary structure was removed and the river was returned to its natural course.

“It’s not going to look like the last one,” Mills said. “This is a much bigger impoundment. Easily twice the size. It had a wider flooded area; this dam backed water up from 26th street all the way to the (Otsego) township dam, basically.”

The plan will require the removal project to be done in more steps.

“We’re going to stabilize portions of the dam that aren’t stabile now, so it doesn’t fail,” he said. “We’ll demolish a portion of the powerhouse section. We’ll install some sheet pile that will stabilize the dam and also allow for dewatering the dam upstream.”

The final design is still being finalized. It’s set to go out for bids in June, with construction slated to begin in August.

DNR fisheries habitat analyst Joe Nohner said this was ecologically important.

“Fish need to pass up and down the river,” Nohner said. “This is part of a larger effort to remove other dams along the Kalamazoo River. We’re in discussions about the Allegan dam soon.

“The overarching goal is to reestablish fish passage throughout the system.”

“This is just Step 1,” Mills said. “The full removal has to take place as part of a remediation of dam impoundment. We’re still waiting for the EPA to initiate that action. We couldn’t wait for that any more.”

As in Otsego Township, the temporary structure has a limited lifespan—this one is rated to last approximately one to two years.

“EPA will have to mobilize the responsible parties to act,” he said. “We are talking to the EPA and do expect them to come on board. We just don’t know when yet.”

If the project is green-lit for a time-critical cleanup effort, EPA will likely remediate only soil from the riverbank and riverbed to prevent erosion. PCB in the flood plain poses little immediate risk as the substance tends to cling to soil particles instead of moving through groundwater.

Mills said, “With this, the river will be restored to its natural course and it will improve recreation, fishing, boating and improve the habitat for fish and wildlife.”

The grant comprised nearly a third of this year’s dam management awards, which totaled $8.3 million among five projects statewide.

Contact Ryan Lewis at rmlewis@allegannews.com or (269) 673-5534.

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