Project Tag: dam repair

Spillway Repairs at Wanapum Dam

Global was contracted by Grant County Public Utility District to perform extensive spillway repairs at Wanapum Dam. The concrete on the apron, ogee and end sill on four of the spillway monoliths had become badly eroded over time. The Dive Supervisor, crane operator and 6 man dive team worked from a barge in the river in front …

Willow Creek Dam Rehabilitation

Global was selected as a subcontractor to provide diving and marine construction services for the Willow Creek Dam rehabilitation in 2017. The rehabilitation of the dam involves lining the existing intake tunnel with steel liner sections and installing three new hydraulic control gates. The majority of work was designed to take place in a dewatered …

Balch Camp Dam Low Level Outlet Gate Repair

Our California region was contracted to assist with repairs to a 30” low level dam outlet gate. Phase 1 of the project included silt relocation efforts and a ROV inspection to monitor the progress. During phase 2,divers removed and replaced the existing cylinder after repairs to the gate.

Diving depths were in the range of 100 ffw at an elevation of 3000 ft. Due to this elevation and water depth combination surface decompression was utilized.

Cheesman Dam Upstream Control Project – Phase 1

Cheesman Dam,located at 6,842 feet of elevation,is a primary reservoir for Denver Water who provides the potable water to Denver,CO and surrounding areas. Completed in 1905,it was built by Italian Master Masons using finely set and mortared granite blocks. Cheesman was a technological masterpiece and landmark of civil engineering for decades to come.

The Upstream Control Project,Phase 1,encompassed the replacement of three internal gate valves with new hydraulic slide gates located on the upstream face of the dam. The first step was to upgrade the existing Auxiliary,Mid and Low Level outlets,located at 60′,150′,and 200′ deep respectively.

Diver’s worked off of 80-foot by 80-foot sectional barge platform on the reservoir. Due to the depth and the amount of work required a combination of surface and saturation diving was utilized. The Auxiliary level work was done using surface supplied air while the mid and low level outlet work was done using saturation diving.

The original bypass outlets,tunneled through the canyon wall,were enlarged to accept new stainless steel spool pieces,one weighing 29,000 pounds and other two weighing 14,000 pounds each. Divers drilled holes at predetermined location and used underwater explosives to enlarge the openings to accept the new spool pieces. The spools were installed just inside the canyon wall,secured in place with epoxy anchors drilled into the native material,and securely grouted to provide a leak free seal. The new stainless steel slide gates were then mounted to the face of the spool pieces and protected by trash racks to prevent rubble from entering the intake system.

The new valves are operated from a new control structure built on the crest of the dam. This structure houses the hydraulic pump unit and controls which operate the valves. To connect the hydraulic tubing to the valves,holes were drilled from the crest of the dam,exiting into the reservoir next to the gate locations. Hydraulic tubing was installed into the holes and secured in place with grout,connecting the controls on the surface to the individual valves.

Eleven Mile Canyon Dam Gate Repair

Located approximately 70 miles southwest of Denver,Colorado at an elevation of 8,602 feet,Eleven Mile Canyon Dam is owned and operated by Denver Water. The gates were located at a water depth of approximately 104 feet. Converting for the elevation,divers were exposed to an equivalent water depth of 140 feet.

Divers performed work using a combination of standard air and Nitrox. Tasks included the removal of the stems and guides from the face of the dam. Once the stems were removed,the gates were brought to the surface where the existing hardware was removed and the gate pressure washed. New stainless steel stems,guides and couplings were then installed.