Station 4
Alternatives

Click the PowerPoint icon to the left to download the Design Alternatives Discussion presentation.

Two alternatives are being carried forward for consideration: Dam Replacement Downstream and Dam Decommissioning. The primary mission of this scoping effort is to gather public feedback on these alternatives to aid County leadership in making a decision. This page will review the preliminary design features and the economic benefits and costs of each alternative.

1. Dam Decommissioning

 

Click the PowerPoint icon to the left to download the Dam Decommissioning presentation

Dam decommissioning includes a notch in the dam to pass the 100-year storm. Breach cuts in the 5 failed dams already provide this notch. Complete removal of the dam embankment is not required by the Wisconsin Department of Natural Resources (DNR) or the NRCS. Furthermore, neither agency requires the removal of accumulated sediment behind each dam.

  • Excavate notch in the dam to pass 100-year storm

  • Shape notch with 2:1 slopes

  • Embankment not removed completely

  • Remove concrete riser, fill the principal spillway pipe with grout, fill the plunge pool with soil

  • Seed and mulch all disturbances

  • Remaining embankment not removed

  • Accumulated sediment not removed

    • ​Annual sediment produced in West Fork Kickapoo watershed = 91K tons

    • Annual sediment produced in Coon Creek watershed = 98K tons

    • ​Sediment accumulated behind Jersey Valley = 122K tons 

    • Total sediment accumulated behind Mlsna = 15K tons

    • Sediment accumulated behind CC 21, 23, and 29 = 12K tons each

To view the difference in the 100-year floodplain with and without the dams, click on the button below for the Online Mapping Viewer. Note: this mapping tool is not intended to be used for design purposes, but rather to give an estimation of floodplain difference without dams. As water modeling and GIS data is refined, the GIS layer will be updated for better accuracy.

Directions for Online Mapping Viewer:

  • Map is interactive. Use the + and tools to zoom in and out, parcel outlines and map labels will appear when zoomed in.

  • Use the mouse to click map and drag the positioning.

  • Click on individual parcels or features to display detailed information.

  • Map will automatically load with the Legend Tab in place.

  • To turn map layers on and off, click on the tab titled.

  • Show Contents of Map (the box symbol next to the small blue 🛈 in the upper left above the legend. If you hover the mouse over these tabs, it will show their contents).

  • Click on blue check boxes to add or remove map layers to view differences in floodplain scenarios.

Example of breached dam, CC - 29 - Korn

CC29_DJI_0197 (1).JPG

June 2021

DSC_5216.JPG

September 2020

Example of breached dam, WFK - Mlsna

DJI_0006.JPG

June 2021

DJI_0003.JPG

June 2021

2. Dam Replacement

Failed structures will be replaced immediately downstream and be designed to meet the low hazard classification. The dams would be earthen with a concrete auxiliary spillway through middle of embankment. To reduce the risk of future, concrete cutoff walls will be installed.

 

The dams would have similar features as shown in these pictures.

replacement1.png
replacement2.jpg