Why is the current Engineered Plan the best solution for Lake Mitchell?
01
Both Lake and Watershed are Addressed in Engineered Plan
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This is the most cost-effective engineered plan.
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Approved by two separate engineering firms, the Department of Ag and Natural Resources, and the Game Fish and Parks.
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Phosphorous is physically removed through strategic mechanical dredging in the lake, and through sediment-catching ponds and wetlands that will start at the west end of Lake Mitchell and continue to the Kelly Property.
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This work will significantly reduce the food source for toxic blue-green algae to feed and grow upon.
03
The Only Way to Remove Phosphorous from the Lake Bottom without Creating Toxic Algae Blooms in the Process
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Though it is challenging to imagine the lake being mostly drained for up to two years, the process of mechanical dredging (Using excavators and dump trucks) ensures the most accurate and cost-efficient removal of phosphorous-laden sediment without releasing high levels of phosphorous into the water column.
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Any option that stirs up the sediment at the bottom of the lake will release a significant quantity of phosphorous into the water column possibly causing toxic algae blooms far greater than anything seen to date.
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Additionally, mechanical dredging can target areas of the lake bottom that have higher concentrations of Phosphorous requiring less dredging to remove up to 85% of the phosphorous load.
02
Taxes Won't be Raised for the Proposed Project
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Through careful budgeting and saving, the City of Mitchell can take on this project without raising taxes and still have reserves and bonding capacity for other city priorities.
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Major bonding debt from past projects such as the pool, corn palace renovation, library renovation, and the second sheet of ice, all come off in 2029 and 2030.
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The State of South Dakota is currently stating that the City's reserves are too high and they need to be used on the project they were budgeted for.
04
The Near Lake Sediment Ponds and Wetlands Catch Phosphorous Coming in
From the Watershed
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38 acres of sediment ponds and wetlands at Kelley Property.
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Works starts August 2024
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Complete in November 2024
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17 acres of sediment ponds and wetlands planned between Kelley Property and the west end of Lake Mitchell.
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Sediment Ponds force phosphorous to drop out of the water column where wetland vegetation can consume it.
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During dry seasons, this vegetation can be mowed, physically removing the phosphorous.
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When water levels are lower, the draw down can minimally lower the lake level, allowing the sediment in ponds to be cleaned out with an excavator and replanted.
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The draw down gives the city a way to eliminate this phosphorous without draining the lake to the levels proposed in the current dredge plan.
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Resource Links
Photo by SD Dept. of Tourism