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Water levels, weather complicating Lake Koshkonong dredge plan

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Photo by Bill Olmsted

An excavator picks up chunks of ice and frigid water from Lake Koshkonong on Monday, using the slurry to build a ‘road’ across the north shore of the lake. The material refreezes into a firm base that will allow trucks carrying dredged materials from one spot to a dump site near the shore of nearby Mud Lake.

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Photo by Bill Olmsted

A new shoreline has grown up recently along the north side of Lake Koshkonong, left, near Mud Lake, hidden on the right. A dredging company will use material taken from Koshkonong’s bottom near the North Shore Drive boat launch to fill in the area on the right side of the road above to protect Mud Lake.

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Town of Sumner — Lake Koshkonong’s wild ups and downs have a history of muddling some of the best-laid plans.

True to form, rapid changes in water levels at the lake along with nearly constant freeze-thaw cycles this month have complicated a dredge project along the lake’s north shore.

Badgerland Excavating has spent parts of the last two weeks preparing and packing down a nearly mile-long, 3-foot-thick ice road along the north shoreline. Crews had planned to use the ice road to truck material dredged from a boat access along North Shore Road to a riprap breakwater crews built last week.

So far, the job’s been easier said than done.

Kevin Hahn, a project supervisor for the Madison-based excavator, said crews had a “stable” ice road compressed to the lake’s shallow shore bottoms and workers were poised to begin dredging Monday.

Then, over the weekend, runoff from recent rains reached its peak. Hahn said that caused lake levels to shoot up, the shore ice heaved and water got under the ice road, which is about as wide as a residential street.

“It lifted the ice off the ground and it was floating. So when we tried to drive on it, it wants to sink and break up,” Hahn said.

The dredge and breakwater is part of a pilot project by the Rock-Koshkonong Lake District and the state Department of Natural Resources. It’s aimed at improving boat access and reducing erosion and silting of a thin shoreline area that divides the lake and marshes just east at Mud Lake.

Last week, trucks weighing nearly 50,000 pounds each had no trouble hauling loads of rock south on the ice road to build the riprap. That work went on even as lake levels were climbing from heavy rains and temperatures were well above freezing. It took a while for runoff from rains early last week to work through Lake Koshkonong’s large watershed, which covers thousands of square miles.

“The recent rain sure didn’t help,” Hahn said.

Neither have the constantly flowing artesian wells, which drain year-round from small pipes that jut from shore all around the lake. The wells have worked to soften up the shore and further destabilize the crews’ ice road.

Temperatures crept up into the mid-40s Monday afternoon, and the shoreline ice continued to soften, crack and break up. Puddles were visible in spots along the shoreline as more rain moved in. Some people continued to ice fish on the lake Monday.

Hahn said he’d sent dredging crews home for the day. Instead, workers focused on breaking up new ice from the lake with a backhoes and trucking it with a quad-axle dump truck to fortify soft spots on the ice road, which is located just off shore at North Shore Road and continues south along Lamp Road.

Backhoe operators worked to smash the ice and pound it into soft spots. That work essentially squeezed water out from under the ice road.

Monday was a setback for the project, which the lake district had estimated earlier could cost around $200,000 to $250,000 if few complications hold up work. Lake District Chairman Brian Christianson told the Gazette. Badgerland won the job with a bid far lower than those earlier estimates, according to the lake district.

Hahn said a swift drop in temperatures expected today and Wednesday ought to help stabilize the ice, making it easier for crews to haul truckloads of dredge spoils that will weigh up to 60,000 pounds.

The cold weather is welcome. Lake district officials say the project timeline has a small window, and it’s nearing an end. Lake district Chairman Brian Christianson has said spring thaw and pre-flood conditions often kick in from early to mid-March.

The project would have to be completed by then or it could be delayed indefinitely until a winter season when lake levels fall low enough again, Christianson said.

Lake District officials, including Christianson, have trumpeted the project as a win-win for boaters and sportsmen. The plan came under fire late last year by lake residents who believed wildlife was at risk of being frozen out by the project because it included a winter drawdown.

The lake district has defended the drawdown, with Christianson saying it was tied to the project plan OK’d by the DNR and fell within current legal limits for water levels.