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Floodwater could conceal problems

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Flooding photos

Severe storms and flooding have caused problems locally and statewide. If you have been affected, we want your photos. Send us your photo.

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JANESVILLE — Officials have no urgent concerns as record amounts of water push against the bridges and dams on the Rock River in Rock County.

Two possible weak spots the land next to the Indianford Dam just south of Edgerton and the Monterey Dam in Janesville.

In both cases, workers have shored up the weak spots, and they’re keeping watch.

So far, so good.

The big question now is what kind of damage is happening out of sight, under the water.

The assumption is, there will be damage, Janesville City Manager Steve Sheiffer said.

“Until the water goes down, we won’t know accurately,” Sheiffer said at a recent press conference.

So, what kinds of damage?

Michael Oliva, a professor specializing in structural engineering at UW-Madison noted these areas of concern:

Bridge decks

Bridges in this part of the country are built to handle loads pressing down on top of them, not pressure from the sides.

Floods can push against the sides of bridge decks, shifting them on their supports, weakening them.

That’s a concern with the Rock River Parking Plaza in Janesville, officials said, but so far, the water is flowing inches below the deck.

If the water gets high enough, the plaza will be closed, said Jack Messer, director of public works.

“We are monitoring this and other structures 24/7,” Messer said.

Scouring

The water can gradually dig away parts of the riverbed around structures such as bridge piers.

Bridges with pilings going down 60 feet or more are safe from scouring, Oliva said, and that’s standard practice for all state-built bridges in Wisconsin.

Even so, the Monterey Bridge in Janesville, a state bridge, is a concern. City officials have noticed an unusual pattern to the water flowing near a pier that holds up the bridge, Public Works Director Jack Messer said the flow might indicate a scour.

The city has notified the state Department of Transportation, and the DOT plans to send divers into the water sometime next week. But for the moment, the bridge is considered safe.

Old bridges and those not built by the state could be resting on shallower footings, and those could present problems, Oliva said.

In Janesville, all but one bridge are known to be sitting on deep piles, Messer said.

Records were not available for the former railroad bridge that is now part of the bike trail upstream from Monterey Park, but Messer said it’s also probably sitting on deep piles, and no problem is anticipated.

River walls

If land becomes saturated behind walls such as the ones that line the river in downtown Janesville, and if the water level drops quickly, the heavy soil could tilt the walls inward.

That’s a concern in Janesville, although the river flow normally rises and falls slowly, which would help, Messer said.

“We will not be able to rest and will have to be on the lookout for structural issues for some time after the waters have receded,” Messer said. “We will continue to monitor structures for some time as the waters recede.”

SANDBAG WORRIES

Sandbag barriers several feet high are a concern for Ben Coopman, Rock County’s director of public works.

Water could topple those walls, inundating the areas they’re meant to protect, Coopman said.

And sandbags could begin to fall apart if they’re needed for too long.

“It’s like putting duct tape on something in your car,” Coopman said of sandbags. “It’s a short-term fix, but that’s not the ultimate solution.”

Coopman added: “How long the water stays high will be key.”