Informed decisions create resiliency

Seismic and Hydraulic Rehabilitation of Big Tujunga Dam

The 244-foot-tall Big Tujunga Dam, nestled in the San Gabriel Mountains northeast of Los Angeles, California, was originally completed in 1931. When the Los Angeles County Department of Public Works (LACDPW) wanted to perform a rehabilitation and spillway modification, we worked with them to meet the updated standards for maximum credible earthquake (MCE) and probable maximum flood (PMF) scenarios.

LACDPW commissioned us to conduct studies to reanalyze both the seismic and hydraulic issues related to the dam, which had been operating at 25 percent storage capacity due to seismic safety concerns for more than 30 years. The studies confirmed the dam’s inability to handle MCE and PMF and proposed a number of alternatives for both the seismic and hydraulic rehabilitation.

LACDPW selected an alternative design recommended by our team that wouldo strengthen the dam by adding concrete against the downstream side to create a thick arch—in combination with construction of a new ogee crest spillway with flip-bucket.

We provided optimized and efficient design solutions for the rehabilitation of both the dam and spillway and provided engineering services during construction.