Morris Dam

Groundbreaking for the Samuel B. Morris Dam was in April, 1932, with completion in May 1934. The dam is named after civil engineer Samuel B. Morris, Chief Engineer and General Manager of the Pasadena Water Department (PWD). The City of Pasadena was facing a critical water shortage because of an alarming drop in the ground water levels in the Pasadena Basin, the primary source for the City’s water. Chief Engineer Morris needed a solution that would provide a reliable long-term supply. The Morris Dam project would help solve the shortage by storing the flood waters of the San Gabriel River.

 Morris Dam was the first major dam approved for construction under California’s new dam safety review procedures adopted after the 1928 St. Francis Dam failure. The legislation passed in 1931 was the first in the United States. The extensive foundation investigations resulted in what was probably the most thorough exploration of a proposed dam site up to that time.

 Morris Dam was the first dam designed for pseudostatic seismic loads. It was an imaginative design solution to accommodate the known foundation weakness for a physical fault offset, which was the first in the U.S., and set significant precedents for future dam designs. The dam design incorporated a unique “baffle slip joint” over an existing inactive fault that allows for movement of up to 3 feet either way along the joint without the loss of water-holding capacity or structural integrity. Since 1934, about 2.5 inches of vertical offset has been accommodated by the fault joint with no significant leakage along the joints.

 The design also included the first specified use of low-heat-of-hydration Portland cement in concrete dam construction to minimize shrinkage and reduce internal stresses.

The dam was the first to have its dynamic properties evaluated, using extensive instrumentation to monitor the performance of the dam’s structure. A dynamic exciter was built for the dam and used to determine its fundamental periods of vibration and its deflection characteristics.

The Morris Reservoir was used from the 1940s as an underwater ordinance test site by the California Institute of Technology under contract with the Office of Scientific Research and Development. The early tests included the development of a reliable air-launched torpedo and were expanded to Cold War tests of underwater missile launch systems.