Flow Re-routing
Status: Sediment Basin Tidegate Removal (Package 1), was awarded to and completed in May 2018 by De Moya/Continental Joint Venture for $21.3 million; McCoy's Cut Diversion Structure and Cut Closure contract (Package 2) was awarded to and completed in May 2020 by the Continental Heavy Civil Corporation for $21.9 million.
Summary: The 47-foot plan includes several modifications to the freshwater flows in the Middle and Back River. The first project of the Flow Re-Routing work was the removal of the old Corps Tidegate structure and widening of the Back River at that location. This was completed in May 2018. The second project was the construction of the freshwater diversion structure at McCoy’s Cut and the closure of two (2) cuts (McCoombs and Rifle) to prevent saltwater from getting into the Back and Middle Rivers and protect the freshwater wetlands.
The third project is the construction of a submerged rock weir and a Broadberm of sediment upstream of the weir to assist with re-direction of the saltwater in the deepened channel up the main channel (Front River). This project is currently in design and tentatively scheduled for award in FY23.
As art of the comprehensive mitigation plan for the SHEP, these changes will re-direct the flow of saltwater to significantly reduce the amount of impacts to freshwater wetlands, which was determined the highest priority wetland natural resource in the Savannah River Basin. The flow re-routing plan will direct more freshwater into the Back and Middle River area on the South Carolina side of the river.
Flow re-routing would reduce salinity in 740 acres of salt marsh, converting it to brackish marsh (making it less salty, but not exceeding four parts per thousand of salinity). Studies show the wetlands will retain the same functional value, thus constituting “no net loss” of wetlands.
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