Black River Lake drained after dam failure in western U.P.; here’s what happened.

ERWIN TOWNSHIP, Mich. (WJMN) — A lake in the western U.P. has been drained after the discovery of a partial dam failure and extremely low water levels, according to the Department of Natural Resources.

“The river has been completely returned to its natural flow,” said DNR spokesperson Dave Caroffino.

The agency had been getting reports of seriously low water levels in Black Lake River since last Friday, June 28.

Just two years ago, the dam was rated in fair condition. You can survey dams around Michigan in the map below:

The Black River Lake Dam was a “low-risk” dam, with few nearby structures and little at risk if there was a sudden dam failure. Caroffino said dams in various risk environments have different constructions, featuring different strengths and safeguards.

In this case, the dam was made up of a culvert structure barricaded by stacked boards to stymy the flow of water north to lake Superior.

Caroffino said DNR staff found during an on-site investigation that the lower boards, also called stoplogs, of the dam had failed, and that the reservoir was slowly draining out as a result.

“I spoke with locals who described the impoundment as being 10-15 feet low over the course of three weeks. It is likely that the stoplog(s) completely failed around June 24 or 25, which coincided with a heavy rainstorm,” said DNR fisheries biologist Jennifer Johnson.

“Upon inspecting the dam, it appeared the lower stoplog(s) failed, and that was the cause of the drainage. Upon further investigation of the downstream area below the dam, sediment was not observed to have washed into the floodplain or caused erosion of the streambanks, indicating that this was not a quick flooding event,” said Johnson.

After the failure was discovered, DNR staff removed the remaining stoplogs to prevent an inadvertent refilling of the reservoir. This drained just about all of the remaining water, and led the DNR to close the boat launch formerly providing access to the lake as a result.

“It has happened before,” said Caroffino of the recent dam failure—a fact which contributed to the agency’s decision to remove the remaining stoplogs.

He told us that since the dam was originally built in the 1930s, and has had severe drainage events before. With this latest event, Caroffino said experts with the DNR and EGLE wanted to take the time to evaluate whether they should let the environment restore the stretch of river to its natural state, or reestablish the dam and lake.

Caroffino said the lake worked to warm the waters, affecting the fish population.

Without the dam, the Black River would cool down, potentially stretching favorable conditions for trout in the river. As a caveat, Caroffino said he had not yet looked at data for the river’s southern reaches, since it crosses the Wisconsin boarder less than a quarter mile from where the lake begins.

EGLE’s Dam Safety Unit has been alerted to the past week’s events. A timeline for when a final decision From the DNR and EGLE on the river’s future was not discussed.

You can learn more about dams around the state on the DNR’s website.

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