It was drained down to dredge and improve habitat. This has been done on other lakes in South Dakota, probably most notably - Canyon Lake in West Rapid City. Yes, the lake can be drained, but water will remain in the original creek channel. This put a new light on draining Lake Mitchell and doing the mechanical dredge. The city also purchased land West of Lake Mitchell to create a wetland ahead of the lake, and the drawdown is needed to maintain that wetland and associated sediment traps. When the drawdown is complete, the city will have the ability to draw the lake down by opening the valve.
This also gives any contractors bidding the project a better opportunity to physically see where the work will be done and the conditions under which they will be working. As design progressed, Barr determined the most cost-effective way for the project to be completed would be to draw down the Lake and mechanically dredge it. As we began working with Barr Engineering, we anticipated doing the dredge work hydraulically. Fyra estimated the mechanical dredging to be less costly, $10 million versus $13 million to dredge with water remaining in the lake. The original work by Fyra looked at two methods to remove in-lake sediment: Hydraulic dredging, with water in the lake, and mechanical dredging draining the lake. Why are we draining the lake to remove the sediment? Wasn’t the intent to leave the lake with water in it and remove the sediment and can a lake be drained? Hopefully, this will address some of these Frequently Asked Questions. Several questions have recently been asked about the Lake Mitchell project.
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