Friday, March 12, 2010

Shiawassee River Corunna Dam

(03/11/10) -- The Michigan DNR says the dam on the Shiawassee River is in poor condition.
According to the agency, if the dam should fail, two bridges downstream are at risk.
City officials admit the 150-year-old structure is in bad shape. Fast-moving water brought on by snow melt doesn't help.
"The dam's in poor condition. We've known that for 35-40 years now," Corunna City Manager Joe Sawyer said.The DNR recently sent a letter to Corunna City Hall, telling officials to draw down the water backed up behind the dam to relieve pressure on it.

"Their order was to do it immediately," Sawyer said.
The only way to lower water levels is to open the spillway, which Corunna officials believe would severely damage it and cause a large amount of erosion to nearby riverbanks.
This is the State Street bridge over the Shiawassee River. It's about 200 yards downstream from the dam. The DNR says if the dam should fail, the bridge would be at risk.
"We're confident downstream damage is not an issue," Sawyer said.
"That was rebuilt in 2005 and has deep pilings. That would outlast a pretty good storm," agreed Corunna Superintendent of Public Works Tim Crawford.
The DNR says even a foot bridge a half-mile away in McCurdy Park could be damaged if the dam was breached. This summer the DNR wants the city to punch a hole in the dam to lower water levels even further.
"A hole will break open at some point in time. It won't be a big deal. They don't want to let Mother Nature make that call," Sawyer explained.
If a portion of the dam is removed, the impoundment behind it would disappear, and with it, recreational boating.
"It's all going to be lost and I don't want to lose that either," Mayor Chuck Kerridge said.
Corunna officials will meet with the DNR soon to talk about their concerns and to see if the dam can be saved.

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