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Geology--Geological conditions at the damsite are favorable for the construction of a concrete dam and an underground powerplant. The Colorado River has formed a narrow, steep-sided inner gorge in hard, resistant formations. Explorations consisted of 35 drill holes ranging in depth from 53 feet to 435 feet, for a combined total of 5,480 feet, and two test drifts, 100 feet and 75 feet long, were excavated into the left and right abutments, respectively. Drawing Nos. 788-300-39 and 40 show geological sections of the lower gorge at the damsite. The dam would be embedded in three geologic formations. The upper part of the abutments would be in massive Redwall limestone and the middle portions in hard Cambrian dolomite and dolomitic limestone. The lower part of the abutments and the dam foundation would be in the silty limestone Mauv formation. Over 400 feet of the Mauv formation would lie between the base of the dam and the top of the soft and incompetent Bright Angel shale. The powerplant and penstock tunnel excavation would be in the dolomitic limestone and in the Mauv formations. The diversion tunnel would be in only the Mauv formation. Access facilities--The isolated location of the project and the deep canyon in which the dam would be located present a difficult access situation that would require solution before any but token activity could proceed at the damsite. The damsite is located about 86 airline miles north of Flagstaff, Arizona, and within the deep rugged gorge of the Colorado River. The river is approximately 3,000 feet below the surrounding plateau area. At present the plateau above the damsite is accessible from Flagstaff 19Epson Perfection 4870 Photo, 400 dpi, 8 bit, 14,176,256 byte