Dam fix requires Rock River drawdown
They also expect to find street barriers, boat cushions, trash barrels, children’s toys and several picnic tables on the exposed riverbed.
This Sunday, North American Hydro officials, in cooperation with the city of Janesville, will begin to draw down the Rock River.
Lower water levels will allow North American Hydro to make repairs on the Centerway Dam, which was damaged in last year’s flood.
It will also expose significant portions of the riverbed upstream and downstream of the dam.
For boat owners, that means it’s time to take boats out of the water or put them up on lifts.
For scavengers, litter-picker-uppers, and Janesville taxpayers who would like their picnic tables back, the drawdown might give them a chance to retrieve items from the exposed riverbed.
Here’s what you need to know:
Q: When will the drawdown begin and how long will it last?
A: It’s a three-week process.
The drawdown will begin Sunday and will continue for about a week. Expect water levels to go down about 6 inches a day.
After about a week, work will start on the dam.
Then, after about a week of work, water levels will be returned to normal—again, about 6 inches a day.
Q: What’s wrong with the dam?
A: The flashboards, the wooden boards on the top of the dam, will be repaired or replaced.
“If you look from the east river walkway, you can see some gaps in the water flow on the top of the dam,” said Tom Presny, city parks director.
The work will be done by North American Hydro, which owns the dam.
In addition, the city’s engineering department is considering using the drawdown to inspect the Monterey Dam, the river wall and the supports under the parking structure, said Larry Buetzer, assistant engineering manager.
Q: What parts of the river will be affected?
A: The river will be lowest upstream from the dam.
Don Bush, fishery biologist for the Department of Natural Resources, thinks the impact will be most significant 2 to 3 miles upstream.
Presny agreed, adding that the impact will be felt about halfway to the Indianford Dam.
Downstream, water levels will be extremely low throughout downtown and all the way to the Monterey Dam, Presny said.
Q: How much of the river bed will be exposed?
A: “The river is somewhat of a flat bowl,” said Tom Presny, city parks director. “If I had to guess, I’d say that the middle one-third of the river will have water, leaving one-third of the bank exposed on either side.”
Q: What about the city boat launches?
A: The city will close the launches as soon as they become unsafe to use, Presny said.
Other parts of the river will be closed to boats if it is determined to be unsafe or unusable for recreational users.
Q: Why now?
A: “The primary reason for this date is that it will have a minimal impact on the recreational use of the river,” Bush said. At the same time, it’s still warm enough for fish and aquatic creatures to survive the drawdown. Any later and they might freeze.
Q: What will happen to the fish?
A: Most will just travel down the river as the water lowers.
“There is a chance that small fish might get trapped in pockets of water that are formed,” Bush said. “The egrets and herons will probably get them—but they need to eat, too.”
Q: Will there be a river cleanup?
A: “At this point, the city doesn’t have anything officially planned,” Presny said.
During the last drawdown, which was sometime in the early- to mid-’80s, some cleanup was done by the city and citizens.
Q: Can people do cleanup themselves?
A: It depends on conditions.
Buetzer said he hopes to include police and fire officials in discussions about the drawdown because of potential safety issues.
The banks could be covered with several inches of mud and cluttered with debris.
Q: What kinds of things might turn up?
A: “Seems like every time there’s a drawdown, somebody finds the safe,” Bush said.
Presny predicts “a half-a-dozen” picnic tables—and a safe.
“It’s our expectation that there will be a lot of natural debris—that’s usually not to be removed,” Presny said. “We’ve lost a few picnic tables. I did once witness a safe being taken out of the river. I remember the police department had to deal with it.”
Last updated: 11:21 am Thursday, December 13, 2012