Posted on April 15, 2024
Property owners on Lake Mallalieu in Hudson, a scenic flowage at the end of the Willow River, formed by a dam where it enters the St. Croix, are seeking a permit to remove large amounts of sediment from about 100 acres of the lake. The project would be focused on areas where many tons of silt has settled in the past decade after a dam was removed upstream.
The Lake Mallalieu Association initiated the application process with the Wisconsin Department of Natural Resources in February. More information about the project will be presented and discussed at the group’s annual meeting on May 6. Some members are already speaking out against the plan, saying it could have drastic impacts on an important area for numerous types of waterfowl and other wildlife.
The current proposal calls for dredging as much as four feet down, removing about 220,000 cubic yards of sediment in total. Work would be concentrated on the northeast end of the lake, and continue about 400 yards up at least one channel of the river’s delta as it enters the lake.
Much of the work would take place in a part of the lake that the DNR designated in 2006 as a sensitive area. After a study by agency experts, they selected the area based on “its high quality fish and wildlife habitat, diverse aquatic vegetation, undisturbed and unique terrestrial vegetation, its importance for protecting water quality and its natural scenic beauty.”
Among several recommendations in the 2006 report, the DNR called for preserving the area’s habitat, and for no permits to dredge or otherwise modify the lake bed.
Then, in 2015, the DNR discovered the Little Falls Dam, 2.5 miles upriver, was failing. The agency was forced to breach it to relieve pressure and reduce the threat. Water flowed out relatively slowly at first, and most of the sediment stayed in the former lake bed in Willow River State Park. Then, late that year, an extreme rain storm dropped 3.5 inches of rain on the area and a flood carried large amounts of sediment downstream to where it entered Lake Mallalieu.
“When they breached the dam, we got a lake full of silt and there’s no getting around that,” Lake Mallalieu Association member Jim Thomas said in 2016, the Republican Eagle reported.
The sedimentation has meant that some lakefront property-owners no longer have deep enough water to dock a boat and navigate to the main body of the lake. That led to the lake association’s decision to apply for a dredging permit.
A preliminary proposal for the dredging developed by a contractor claims was completed on January 31.
“Soft sediment removal activities will likely be completed via hydraulic dredging equipment to prevent damage to the native lakebed,” the application says. “Floating silt curtain will be installed on the the perimeter of the excavation activities to contain temporary turbidity. Material will be removed from the lake bottom and pumped to a sediment dewatering location. Disposal location and methods are dependent on contamination and will be part of the dredging feasibility study findings.”
The document also says removing soft sediment will benefit the lake because it will remove nutrients that could otherwise feed noxious algae blooms.
But a vocal group of association members and other concerned people say the proposed dredging would be dangerous and destructive. A recent press release from longtime Lake Mallalieu homeowners John Gostovich and Celeste Koeberl raised several concerns. The announcement highlighted the “sensitive area” designation, as well as the impacts to trumpeter swans that overwinter in the open water where the river enters the lake, feeding on the shallow vegetation.
In addition, the group says the lake sediment contains high amounts of arsenic and other chemicals that have been applied to that part of the lake to control aquatic plants in the past — which dredging could release the back into the water.
The Lake Mallalieu Association annual meeting is May 6 at 7 p.m. at the White Eagle Golf Club. Membership is open to anyone who owns property or lives within one mile of the lake. New members can join in advance here or at the meeting. More information is available here:
