Rock Bolts and High Scaling

Navajo sandstone splits along vertical seams, and a dam wedged into it must be held together. Rock bolts do that work, driven forty-five to seventy-five feet into the canyon walls to lock slabs of stone against falling into the gorge. The crews who install and inspect them once called themselves high scalers, dangling on ropes against the cliff face; their successors are trained rope-access technicians who still hang above the river to check the bolts, mesh the walls, and inspect the dam's abutments.

What the plaque says

Rock Bolts, also, High Scaling. Reclamation : Managing Water in the West., Rock Bolts, Since Navajo sandstone tends to fracture vertically, rock bolts lock rock slabs together, thereby minimizing rock falls into the canyon. These bolts extend from 45 to 75 feet (14-23 meters) into the canyon wall. They are assembled in 10 foot (3 meter) sections. An expansion device on the end ties the bolt solidly to the wall. The plate is 14 inches (36 centimeters) square and 2 inches (5 centimeters) thick. The bolts are cement grouted into the wall., High Scaling, High scalers of the past are now highly trained rope access technicians. Some of the work is similar, installing chain mesh and installing and checking rock bolts. Other work is more technical, including performing inspections of the dam and abutments, spillway tunnels, penstocks, and outlet pipes.

Where it stands

Worth the stop nearby

• Antelope Canyon — 6.1 mi
  Tsé bighánílíní — where the water runs through the rock

More markers nearby

• Navajo Generating Station — steps away
• Major John Wesley Powell — steps away
• Native Americans — steps away
• Rainbow Bridge National Monument — steps away