Littlerock Dam Rehabilitation: Another RCC Innovation

Littlerock Dam is a multiple-arch dam located in the Angeles National Forest, in southern California. It has a maximum height of 175 feet and a crest length of 720 feet and consists of 28 arches. The dam was designed by John S. Eastwood who pioneered the
design and construction of multiple-arch dams. When it was completed in 1924, Littlerock Dam was the highest multiple-arch dam in the U.S. The dam provides vital water supply for both the Palmdale Water District and the Littlerock Creek Irrigation District.
Throughout the life of Littlerock Dam, there has been concern and controversy about the adequacy of its design and overall stability and safety. The dam is located 1.5 miles south of the San Andreas fault. The Maximum Credible Earthquake (MCE) originating on this fault is a moment magnitude 8 event resulting in a peak horizontal site acceleration of 0.7g. The results of stability and stress analyses completed by the California State Division of Safety of Dams and Woociward-Clyde Consultants showed that the dam does not meet required seismic safety criteria, principally because of its lack of lateral stability, a deficiency which is inherent in multiple-arch dams. This paper describes the design for strengthening the dam to prevent it from catastrophic failure during a major earthquake. 12 pp.