Big Tujunga - The Seismic and Hydraulic Rehabilitation of Big Tujunga Dam

The Big Tujunga Dam is located just north of Los Angeles in the San Gabriel Mountains. It stands at 244-feet-tall and has a crest length of 830 feet, including an earthen embankment on the right side. The reservoir impounds approximately 6,000 acre-feet of water, with a maximum surface area of 83 acres collected from 82 square miles of drainage. The project is owned by the Los Angeles County Department of Public Works (LACDPW) and regulated by the California Division of Safety of Dams (DSOD).

The seismic and hydraulic rehabilitation of Big Tujunga Dam was awarded the 2011 National Rehabilitation Project of the Year Award by the Association of State Dam Safety Officials, recognizing a unique remedial design that advances the state-of-the-art in the field of dam safety and exemplifies the high professional engineering standards that dam safety requires. In this article, we will explore the history of the project and the innovative technical solutions implemented to successfully address the inability of the dam to withstand the updated Probable Maximum Flood (PMF) and Maximum Credible Earthquake (MCE) after several decades of maximum reservoir level restriction. Bringing the dam up to modern standards enabled necessary additional water conservation, and was also critical for public safety. Without the necessary improvements, estimated damages from an extreme seismic or flooding event could include injury or loss of life; $175 million in damage to homes, buildings, facilities and roads; disruption of utilities services and commerce to more than 100,000 people; and loss of a source of water storage and supply for about 9,000 of Los Angeles’ residents. 12 pp., 1 reference.