Ailing lake should soon be healthy
Millions of dollars were sunk into the 2,072-acre body of water between 1989 and 1992 to eliminate rough fish and phosphorus-induced algae that made the lake muddy and green.
The water is much clearer, but phosphorus continues to pour into the lake. Carp and bullhead are again causing trouble.
“It’s never going to be a bathtub of water,” said Don Holst of the Delavan Lake Improvement Association.
But the completion of three projects—the removal of 155,247 cubic yards of sediment from Brown’s Channel, the Mound Road sedimentation ponds and the Inlet—should change that, he said.
Dredging of Brown’s Channel
What is it? Brown’s Channel is a small tributary channel.
When was the project started? Fall 2006.
How much sediment was removed? About 3,000 cubic yards.
When was the project finished? Winter 2006.
Renovation of the Mound Road sedimentation area
What is it? The Mound Road sedimentation area is a 140-acre wetland that includes two sedimentation ponds and a gauging station, where the U.S. Geological Survey conducts water testing.
The 4- to 5-foot-deep ponds were constructed in 1992 to slow the flow of water to the lake and filter sediment from the water. By 2002, the ponds were more than 40 percent filled with sediment and no longer functional. To renew the ponds, they needed to be dredged and deepened to 10 feet.
The gauging station also needs to be dredged.
When was the project started? Fall 2006.
How much sediment has been removed? About 2,900 cubic yards from the North Pond and 5,250 from the East Pond. But below the sediment lay native clay and rock, which prevented hydraulic dredging from continuing. About 23,650 cubic yards of clay and rock need to be mechanically removed from the perimeter of each pond, creating a baffle to slow the water and more evenly distribute sediment.
The revised project began in February. Work on the North Pond is finished, but work on the East Pond was halted by mid-March because the site was too muddy for the heavy machinery.
When will the project be finished? Work on the East Pond is more than half done and should resume as soon as the site is dry enough. Removal of the remaining clay and rock should take about a week.
Work on the gauging station should begin at the end of June, when divers will use specialized vacuum-like equipment to remove 1,700 cubic yards of sediment.
The entire project, including the planting of native flowers and grasses at the disposal sites, should be finished by fall.
Dredging of the Inlet
What is it? The Inlet is a 210-acre wetland designed to filter sediment from the water that flows into the lake. It’s the “last line of defense” against sediment.
The Inlet was dredged in 1992 but has collected so much sediment that it no longer acts as a filter. To again be effective, the Inlet needs to be dredged.
When will the project start? Summer 2009.
How much sediment must be removed? About 74,000 cubic yards to create an area nine times larger than the Mound Road sedimentation ponds, according to a 2004 study.
When will the project be finished? Fall 2009.
Dan Lemanski, also of the Delavan Lake Improvement Association, said the projects will cost hundreds of thousands of dollars, but the money is well spent. The lake is inextricably linked to the local economy, he said, and as the health of the lake improves, property values and tax revenues increase.
“These investments produce distinct, compounded and identifiable dividends,” Lemanski said.
Holst said improving Delavan Lake has been “a long, hard battle,” but the end of this series of projects is in sight.
The next step is to focus attention on the 26,000-acre watershed, working to prevent erosion and pollution from farmland that drains into the lake, he said.
Lemanski said even small efforts, such as installing signs that identify the watershed, have the potential to improve Delavan Lake.
“The lake is right on the edge (of healthy and unhealthy),” he said. “Everything we’re doing hovers around that tipping point.”
Last updated: 9:41 pm Thursday, December 13, 2012