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Dane County Land & Water Resources Department

Yahara River Sediment Removal

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.

Our goal is to improve water flow so that the delivery of two inches of rain that normally takes two weeks to travel through the Yahara Lakes system will take half as long, or one week.

 

Project Phases

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:

  • Readily available sediment and bathymetry data for developing engineering plans
  • Presence of contaminated sediment that would impact permitting timelines
  • Proximity of dewatering locations to the river
  • Existence of culturally sensitive features


Phase 1

The first phase is located between Lakes Monona and Waubesa. Hydraulic dredging of approximately 35,000 cubic yards of sediment has been completed. The project encountered rock and debris between Broadway and Bridge Road. Mechanical dredging by the use of excavators and barges will remove approximately 5,000 cubic yards of sediment and debris. The project is expected to resume in the fall after the boating season.  

Phase 2

The second phase is located between Lake Waubesa to Lower Mud Lake and Lake Kegonsa to Highway B. The work between Lake Waubesa and Lower Mud Lake is expected to start in summer of 2021 which will be be performed by Dane County staff and equipment. Approximately 52,000 cubic yards of sediment will be removed. The work between Lake Kegonsa and Highway B is expected to start in fall of 2021 which will be performed by a contractor. Approximately 65,000 cubic yards of sediment will be removed.

Timeline

Updates

July 15, 2021 - The dewatering basin for sediment removal is complete. Sediment removal in the river has started.  Currently the dredge equipment is located just downstream of Exchange Street and working towards Lower Mud Lake.  After work is completed to Lower Mud Lake, equipment will be moved back to Exchange Street and work will continue upstream towards Babcock Dam.

June 7, 2021 - The dewatering basin for sediment removal is nearing completion. Pipeline for the hydraulic dredging has been installed in the Yahara River and secured along shore. Preparation work to launch the dredge in the water is occuring.  The dredge is expected to be in the water within 1 week and sediment removal to begin in 2 weeks. 

May 20, 2021 - Phase 2 construction between Waubesa and Lower Mud Lake has begun.  A dewatering basin  is under construction located east of Highway 51 by Babcock Dam.  

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.

Contact

Dane County Land & Water Resources Department
(608) 224-3730
lwrd@countyofdane.com

Projects