Replacing East Canyon Dam While Operations Continue

Replacing the 50-yr-old East Canyon Dam northeast of Salt Lake City, Utah, by constructing a new, double-curvature, thin-arch dam 240 ft high immediately downstream–without interrupting irrigation storage–posed unusual design and construction problems. Geology of the canyon dictated a site immediately downstream of the existing thin-arch dam; at one point the dams are only 7 ft apart. Keyway excavation for the new dam partially undercut abutments of the old dam. The new dam varies in thickness from 7 ft at the crest to 20 ft at the base of the crown section, and has an axis radius of 200 ft and central angle of 97° at the crest. Presplitting rock foundations, controlled blasting, and monitoring the behavior of old dam were combined to remove successfully 15,000 cu yd of rock for keyway excavation. Concrete was placed promptly in keyways to reinforce undercut abutments of old dam. By winterizing batch plant operations and protecting freshly placed concrete, construction of the dam continued through both winters of the construction period.