As part of a statewide effort to reduce seismic and hydrologic risk to State Water Project facilities, the California Department of Water Resources (DWR)’s Castaic Dam Modernization Program has begun with an assessment of a concrete release structure at the dam. DWR officials will assess the integrity of a 60-foot-wide rectangular concrete chute used to pass natural flows from Castaic Lake into Castaic Lagoon.

“The primary objective for the Castaic Dam Modernization Program is to identify and make improvements that will ensure public safety and a reliable water supply,” said Ted Craddock, DWR Acting State Water Project Deputy Director. “DWR continues to move forward in the modernization of SWP facilities and will be assessing possible improvements to Castaic Dam to mitigate impacts due to an extreme weather event or earthquake.”

The Castaic Dam Modernization Program also includes: seismic retrofits to the inlet tower access bridge; evaluation of the spillway to identify and implement necessary improvements; and earthquake analyses on various dam components. The planned assessment work will be completed by 2022, after which DWR will develop and implement projects to modernize the structures at Castaic Dam. The Modernization Program is expected to take approximately 10 years to complete.

In 2018, the CA DWR Division of Safety of Dams released a report on the safety status of the 1,249 dams under its jurisdiction, including “downstream hazard classification, condition assessment, and reservoir restriction status” for each dam. The information was compiled to support the state’s ongoing efforts to be proactive in dam safety following the 2017 Lake Oroville “spillways incident” triggered by heavy rains in Northern California.

Located 45 miles northwest of downtown Los Angeles, Castaic Dam is an earthfill embankment structure (the same as the Oroville Dam) built in 1973. Castaic Lake reservoir has a capacity of 324,000 acre-feet and stores drinking water for the western portion of the Greater Los Angeles Area. The safety report gave Castaic Dam a condition rating of only “fair” — meaning that, while the dam can satisfactorily hold the amount of water it was designed for, it might have problems dealing with extra water or stresses such as those occurring during an earthquake or weather event. And, based upon the size of the reservoir and the number of people who live downstream of it, the dam received a “downstream hazard” classification of “extremely high.”

Source: Various