The U.S. Bureau of Reclamation reports a 50-feet high by 30-feet wide by 4-feet thick slab of Navajo Sandstone weighing an estimated 250 tons (500,000 pounds) is beginning to separate from the Glen Canyon wall. The slab is a direct threat to the 1,312-MW Glen Canyon hydroelectric project powerhouse at the foot of the Glen Canyon Dam on the Colorado River.
The power plant houses eight units.
Scalers, who are specialized Reclamation workers, employed the facility’s response plan to the threat on Tuesday, Sept. 8 by installing 6- to 8-foot long by 1-inch diameter bolts through the slab and into the canyon wall.
Prior to deploying the scalers, Reclamation discovered the massive fracture on Aug. 28 and installed six rock bolts to temporarily stabilize the area before deploying scalers.
Reclamation plans to gradually remove small slab portions and securely stabilize the remaining rock to the canyon wall, completing the stabilization by Oct. 2.
The Glen Canyon hydroelectric project includes a concrete arch dam that impounds Lake Powell, the second-largest manmade catchment area in the U.S. The scheme was built to provide hydroelectricity and flow regulation from the upper Colorado River Basin to the lower.