Lake Dredging Projects Bringing Lakes Back to Life

Lake dredging is becoming a more popular tool used to improve the overall health of a lake. In southern Wisconsin, School Section Lake in Waukesha County and Delavan Lake in Walworth County both went through lake dredging programs to remove sediment and deepen the lake. At School Section Lake, it not only made the lake more navigable, but also improved the biodiversity and fishing quality. School Section had become overly silted with muck and thus only navigable by canoe, kayak or paddle boat. Now, small motors are often used. They used a suction dredger with a long suction pipe to remove sediment, an affordable project for a small lake community looking to make a difference. It's the most common form of lake bottom dredging.

On Delavan Lake, an inlet had become so silted with muck, it was not navigable. The project had to be done simply to allow lakefront property owners in the inlet to get into the main body of water with their motorized boats. The Town spent $1.46 million to clean out the sediment. The dredging company dredged a 3,000-foot channel down to about 5 feet deep, enough for boats to get through the inlet easily. They removed about 45,000 cubic yards of sediment. The lake was dredged in 1989 but not as thoroughly as it was during the 2011 project. Money well spent on a popular lake and tourist attraction. Delavan Lake is an important part of Walworth County's economy, and the local officials understand the importance of access at all locations of the lake.

lake dredging projectSediment can build up for a variety of reasons. In the case of Delavan Lake, the size of the watershed greatly impacts the lake. The watershed is over 26,000 acres. Everything from farm and residential fertilizers to topsoil to construction site runoff finds its way into Delavan Lake. This builds up over time and affects the quality of the water. For the Delavan Lake inlet, it wasn't just about being navigable. The inlet is home to a 210-acre wetland preserve that serves as a buffer to the watershed. The degradation of that buffer could spell long-term trouble for the water quality of Delavan Lake and could cost the community considerably more to improve the lake down the road. Delavan Lake still has algae problems during the heat of the summer caused by excessive sediment and phosphorus, but the community has taken the preliminary steps to solving these problems. If they don't continue to work on sediment and phosphorus removal, the lake will see a greater build up of algae, which in turn will cause other plants in the lake to die and oxygen levels to decrease. If that happens, the lake is much less attractive to tourists and lake home buyers. Doing nothing will effect the local economy.

In the case of School Section Lake, the School Section Lake Management District fought long and hard back in 1989 to have the 120-acre lake dredged, and it really needed it. "There was a shortage of funds that was offset by grants," according to dredging project coordinator Kathi Brodbeck. Property owners were assessed in order to complete the project. School Section only had an average depth of 2.6 feet before the dredging project. It's maximum depth was just 8 feet. The lake was seeing fish kill almost every winter. The 2-year project which finished up around 1992 made the central basin of the lake greater than 20-feet deep.

 



What exactly is lake dredging and how does it work? Dredging a lake is excavation of the lakebed. It's not easy to get a permit to do such an activity, particularly in Wisconsin. If you own lake front property in Wisconsin, moving a large rock/boulder from the lakebed is considered dredging and requires a permit. You can actually getlake dredging photo fined for doing this without a permit. Just like any other excavation project, the spoils are removed from the site and carried away to a new location. A dredger, a machine used to perform dredging activities, removes the sediment or draws the sediment and other material from the bottom of the lake. It can possibly create a serious disturbance in an aquatic ecosystem, and that's why the process is very regulated and difficult to get approved. It can make the lake's water quite turbid for years if not handled appropriately.


In some lakes, phosphorus levels have gotten so high, that they too are affecting ecosystems. This is often times caused by farm runoff. The lake water becomes de-oxygenated or eutrophied and needs to be remediated. In cases such as these, it's usually very easy to get a dredging permit because dredging is the only way to bring the phosphorus levels down. Sediment must be removed to reclaim the waters.