ArticleCS - Article View


Published July 6, 2021
Expiration date: 7/20/2021

The proposed work consists of the installation of a new raw water intake structure with associated bank stabilization and stream crossing for an access road.  In detail the project would include temporary fill of 1.04 acres of stream bottom within the Congaree River for a coffer dam which would temporarily dewater 0.27 acre of the Congaree River during project construction.  Proposed permanent impacts include 0.18 acre of fill associated with the water intake structure, screening, and submersible pumping electrical supply and controls, as well as 0.41 acre of riprap stabilization adjacent to the proposed intake structure.  Construction of a laydown area would include culvert impacts to 18 linear feet of an unnamed tributary and fill of 0.01 acre of wetlands.  The water supply intake would have an initial capacity of 60 million gallons per day and would be capable of being expanded to 80 million gallons per day.  This raw water intake would replace the water intake at the canal which was affected by the canal embankment failure resulting from flooding in 2015.  The proposed raw water intake would be designed to survive an embankment breach if one were to occur, and the intake would be founded on rock in the riverbed of the Congaree River.  The housing for the proposed intake structure would be 110 feet long, 60 feet wide, and 77 feet high, 62 feet of which would be exposed above the water surface of the Congaree River.  The intake structure would include four submersible pumps which would access water via a wet well at the base of the intake structure.  The applicant proposes a screening facility at the base of the intake facility on the western face.  The screen would consist of a bank of half-round barrel screens based on a submerged slab approximately 7 to 13 feet below normal water surface elevation.  The screening facility would include compressed air lines for periodically bursting air back through the screens for debris removal.  Raw water piping would be comprised of dual 48-inch ductile iron pipes which would extend from the submersible pumps through the raw water pump station structure, across the canal, and would connect to the existing raw water piping before discharging into the existing Canal Water Treatment Plant Reservoir.  Proposed road access to the intake would include installation of a 42 ft wide, 157.5 ft long permanent bridge over the Columbia Canal.  The bridge would include 21 feet of width for traffic and 21 feet of width for the dual 48-inch ductile iron pipe to connect the water intake to the Canal Water Treatment Plant.  The applicant has not proposed compensatory mitigation for this project. The project purpose as stated by the applicant is to provide the City of Columbia with a resilient water supply intake for the Canal Water Treatment Plant, while maintaining the Canal’s compliance with the Federal Energy Regulatory Commission (FERC) current safety standards and meeting long-term water quantity demands for the City.