Blue Ridge Dam Lake Tap Blue Ridge, Georgia | 2003 Tennessee Valley Water Authority
This raw water bypass project consists of a hard rock tunnel mined to a Lake Tap positioned in the bottom of the reservoir. The unique design requires the excavation of the shaft and installation of the liner elbow cap and trashrack being performed from inside a dewatered cofferdam. The cofferdam is designed to withstand pressures of up to 80 feet of water and is installed on a 30 degree slope. The schedule is driven by a water draw down of 80 feet which presents challenges for marine equipment placement. Associated Underwater Services was contracted to supply all marine intervention for the project. The work included assembly of barges and marine equipment, dock building, loading of cranes, anchorage positions, platform construction and cofferdam fabrication and installation. The barges were positioned and completely enclosed by a silt curtain. A down hole hammer was utilized to drill 36 inch diameter sockets for the platform legs. The legs were installed and grouted and 3 whalers were assembled and installed. Due to weight requirements large carrier beams and winches were used to handle the loads. Once the whalers were placed, templates were installed to pre drill for the sheet pile installation. The sheet piles were installed and driven and welded back to the whalers using 3 different pile hammers. Once the lake tap was completed, the cofferdam was removed.