Shoshone Canyon Conduit Modification, USBR Cody, WY

Demolition included removal of concrete-embedded 10 ft diameter cylinder gate valve and 500 CY reinforced concrete from within a gate chamber located 200 ft underground. Also removed two 48" needle valves. Excavated, through controlled blasting technique, a 30' x 30' x 40' valve chamber in downstream face of existing concrete dam. Constructed energy dissipation / hydroelectric power plant structure (3400 CY structural concrete) requiring removal of 18,000 CY of shot granite and sandstone. Drilled, shot, and concrete-lined one 12' horseshoe x 800 LF free flow tunnel in sandstone to connect power plant structure with existing tunnel network. Drilled and shot 70 LF tunnel in granite for 126" penstock to within 10 ft of existing high-pressure gate. Drilled and shot 8' x 8' tunnel in granite. Constructed 12' x 12' x 48' high access shaft and adits in granite. Constructed gantry crane. Extensive dewatering required throughout project. Several river bottom excavations required diverting and pumping the Shoshone River (approximately 20-40 c.f.s.) away from the work area  

The Homestake Tunnel is a 5-mile long horseshoe-shaped tunnel located at 10,200 ft. elevation that transports water from Homestake Reservoir to the East Slope of Colorado. A September 2012 inspection revealed an area ¼ mile from the upstream portal where the concrete ceiling of the tunnel had collapsed. It required the construction of a ¼ mile long walkway to span rails and tunnel flows of 6-8 cfs. A concrete pump was modified to fit into the tunnel. Curved steel formwork was specially fabricated to allow the overhead concrete pours. Crews placed 24 CY overhead. Placed 18CY grout. Also made welding and grouting repairs to the outlet works at downstream portal. Required careful air quality monitoring and ventilation. Work occurred during mid-October through November while racing against the threat of high-altitude snowstorms. 

Sandstone tunnel rehabilitation included the following quantities: 26,000 SF reinforced shotcrete using a robotic spray arm; 85,852 SF of sandstone excavation & shaping; and 90,500 SF of spray grouting to stabilize the tunnel profile. Portal rehabilitation including retaining walls & security gates. Overall total tunnel rehabilitation was 5,280 feet.

Demolition and removal of acid deteriorated concrete and subsequent concrete repair of the 140 ft. long flume located 1000 feet underground in the Cedar Mountain Irrigation water tunnel. Also, construction of a fiberglass reinforced cover over portions of the flume. Caulked & sealed construction joints. Coated major portions of the flume with two part epoxy sealant.

Designed and constructed a 700' long tunnel and intake structure through an existing rock fill and earthen dam to be used as a low outlet works. The 6' wide x 7.5' high tunnel was excavated through rock using an Alpine continuous mining machine. This tunnel excavation proceeded upstream through a rock outcropping within the earthen dam and terminated inside a sheet pile cofferdam located in the lake. Timing and coordination were critical items due to rising lake levels. The intake structure was cast in place. Welded bell and spigot pipe was installed in the tunnel and backfill concrete was placed. New concrete and rock interface was pressure grouted, using 1274 bags.  Other work included installation of a downstream valve vault, cathodic protection, grouting, and piezometers