Construction of Morrow Point Power Plant and Dam

Construction of the Morrow Point double-curvature thin-arch concrete dam and underground power plant is in progress in the rugged Black Canyon of the Gunnison River. Rock excavations, open cut and underground, require extensive stabilization. Periphery smooth wall blasting techniques result in more uniform and stable open cut rock slopes and reduce overbreak. Alinement symmetry and configuration of underground excavations are greatly improved. There was teamwork between the engineer and the geologist employed to analyze and prescribe drilling and blasting patterns in alternating lenticular and irregular beds of rock of varying hardness and strength. Rock bolts were used extensively in open cuts and as a means of roof supports in underground excavations. In the crown of the power plant chamber, no rock was left unsupported longer than 12 hr after blasting. Proper instrumentation provides essential information concerning movement and reactions in the rock in the underground excavations. Gain in tension of rock bolts is recorded by strain-meters. Borehole extensometers are monitoring rock movements. The dam concrete was designed for a compressive strain of 4,500 psi at the end of 1 yr.