Janesville55.4°

River running rampant over dams in Rock County

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Frank Schultz
April 21, 2013

— The floodgates are open on the Rock River.

They’re open as wide as they can be at the Indianford Dam and at the Centerway and Monterey dams in Janesville.

That means if you’re experiencing flooding, you should not point a finger at the dam operators.

“The common understanding is that the dams control the river, and nothing could be further from the truth,” said Scott Purlee, the operator of the North American Hydro plant at the Centerway Dam in Janesville.

The state is monitoring conditions, and so far, there are no problems with the dams on the Rock, said Rob Davis, a DNR engineer who visited the Indianford Dam on Friday.

Davis’ boss, engineer Sue Josheff, who also specializes in river hydraulics, used the words “crazy” and “wow” to describe how the water levels kept rising last week.

“It’s amazing. Last year we couldn’t find the water in the ground, and now it’s creeping up again,” Josheff said.

Back to the dams. Here’s an update, starting upstream and working our way down:

-- Several hundred tons of rock and gravel shored up an area near the Indianford Dam’s powerhouse back in 2008, and more would be brought in if the water ever returns to that level, said Brian Christianson, chairman of Rock-Koshkonong Lake District, which owns the dam.

The Indianford Dam controls the level of Lake Koshkonong when the water is lower, but at this level, the gates are wide open, and any flooding around the lake is unavoidable, Christianson said.

-- The Centerway Dam’s spillway has slots in the concrete where boards are inserted, and those boards had deteriorated over the years. They were replaced after 2008, but Purlee doesn’t think that will make much difference, as the dam simply was brought back to its original condition.

City of Janesville officials, however, said the new boards, about 6 inches above the concrete, will mean higher water upstream, causing conditions similar to those in 2008.

Purlee says he can’t do anymore to ease flooding upstream. The dam’s gates are wide open, and there’s no way to let water through any faster than it’s going, Purlee said.

The city is keeping an eye on the west side of the dam, near the generating station, where there’s a low point and where the river escaped in 2008, flooding the nearby bike trail and eroding the riverbank, said Carl Weber, city public works director.

If that threatens to happen again, the city would consider sandbagging that spot, Weber said.

North American Hydro has added big stones to shore up the west-side bank since 2008 and also added a ramp for canoeists.

Purlee and his staff have pulled large tree trunks, timbers, sections of dock and an old utility pole from the river to keep the power station’s intake clear, but he said the water is much cleaner than in 2008.

“I think people up and down the river have learned to not have their stuff so low, so we don’t see it here,” Purlee said.

-- The Monterey Dam is owned by the city of Janesville, which also is monitoring for floating debris to make sure the floodgates are not clogged, Weber said.

In 2008, DNR and city officials were worried about the old millpond near the dam.

The water was getting close to the top of an earthen berm that held the pond in place. If it were breached, tons of water would have flowed into the river very quickly.

Since 2008, the city has built a wall that keeps the river from flowing into the pond.

The pond has some water and a lot of mud in it. The city is giving the pond time to see what happens to it. One possibility is that it will become a refuge for birds, frogs and the like, Weber said.

The city has fenced off most of the popular fishing areas along the river, for safety’s sake. That’s not sitting well with Shawn McCarten, who recently bought and enhanced the bait shop near the Monterey Dam.

McCarten of It’s a Keeper Bait and Tackle is looking forward to weather more conducive to fishing, as are his customers.

The Centerway Dam, by the way, is the only one of the three that generates electricity, but Purlee said at times of high water, there’s actually less electricity generated.

That’s because power generation depends on the difference in the height of the water from the top to the bottom of the dam, which is called “hydraulic head.” High water means less head, so less electricity.

There could come a point when the water is so high that the two generators in the North American Hydro station on the west side of the river would be shut down, but they were still making power Friday.



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