Currently, water comes into the Yahara Lakes faster than it goes out. Therefore, after repetitive and heavy rainfall events, the lake levels increase and can lead to flooding. The efficient movement of water through each lake is undermined by sediment build-up in the Yahara River. While sediment movement is a naturally occurring process, the accumulation of sediment in the Yahara River and Lakes is greatly increased by human activity, including urban development and winter sand operations. Today, two inches of rain takes over two weeks to leave the Yahara Lakes system due to its sluggish nature.
Dane County’s sediment removal project in the Yahara Lakes system will take place in five phases, with each phase carried out as Dane County secures permitting - see Phase Map (PDF). The benefit to reduce flooding for all lakes is realized when sediment accumulation has been removed along the Yahara chain, thus it is critical that the phases are planned as timely as possible.
Several factors were considered for a five phase plan including:
The first phase, between Lakes Monona and Waubesa, is expected to be completed in 2020. The project will involve removal of approximately 40,000 cubic yards of sediment which equates to over 3,000 dump truck loads of sediment. The sediment will be removed hydraulically by suctioning the sediment from the river bottom and transferring through a pipeline to a dewatering basin. The sediment will be separated from the water at the dewatering basin and reused for other projects such as roadways.
January 28, 2021 - Sediment removal will continue in the spring/summer of 2021. In 2021, phase 1 will resume and be completed for the last section between Bridge Road and Broadway. In addition, phase 2 is anticipated to begin in 2021 and will include sediment removal between Lake Waubesa to Lower Mud Lake and Lake Kegonsa to Highway B.
October 12, 2020 - Sediment removal continues from Wicawak (Squaw) Bay to Bridge Road. It is anticipated that sediment removal will be completed in this section by the end of the week or early next week. Then removal will take place between Bridge Road and Broadway which is the final location to be completed.
September 8, 2020 - Another dredge has been deployed and will work from Wicawak (Squaw) Bay to Broadway. The dredge is smaller but may limit navigation in the river at times. If navigation is not necessary please consider to recreate in other areas to limit congestion. The pipeline has been extended from Broadway to Lake Monona and dredging is expected to start later this week.
August 27, 2020 - Sediment removal has been completed for about 2,500 feet of the Yahara River. Currently the dredge is located just upstream of Hwy 12/18 and staff are working towards the Broadway bridge. The goal is to be up to Broadway by Labor Day weekend.
August 5, 2020 - Sediment removal has progressed. Currently dredging has been completed for about 1,000 feet of the Yahara River. The dredging work is currently located just downstream of Hwy 12/18 (upstream of Gilligan's Island).
July 16, 2020 - Sediment removal has started upstream of Upper Mud Lake (near Gilligan's Island). The dredge is starting at the downstream end of the project and they will be working upstream.
June 29, 2020 - The installation of pipeline and construction of the dewatering basin is planned to be completed this week. Then the dredge will be connected to the pipeline and testing of sediment removal will commence. We anticipate dredging to start later this week or beginning of next week.
June 11, 2020 - Installation of approximately half of the pipeline (1.5 miles) has occurred. Currently, the dewatering basin where the dredged material will be piped to is being constructed. Depending on weather, sediment removal is expected to start in July.
Dane County Land & Water Resources Department