Castaic Dam Modernization Program

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The dam was constructed by the California Department of Water Resources’ State Water Project (SWP) from 1965 to 1974. In 2021, Castaic Lake served as a water source for over 4.8 million residents of California. Situated 45 miles northwest of Los Angeles, Castaic Dam, Lake, and Lagoon cater to the water needs of the greater LA region.

The DWR has initiated the Castaic Dam Modernization Program in the fall to ensure the safe functioning of the dam. Over the next several years, the DWR will undertake construction activities and conduct assessments of the associated structures and the dam. They will also address any potential issues that could impact the safety of the surrounding communities or the delivery of water. Additionally, the DWR is proactively addressing any issues that could affect the delivery of water and modernizing its SWP facilities across the state.

Castaic Dam Modernization Components

Castaic Dam and Lake Statistics

Dam Lake.

Elevation: 425 feet Storage Capacity: 323,700 acre-feet or 105.5 billion gallons.

Length: 4,900 feet Surface Area: 2,240 acres.

Spillway Condition and Extreme Weather Assessments

  • The DWR is currently investigating the impacts and causes of the spillway to ensure it functions appropriately and works towards the rehabilitation target, as the release of water could potentially lead to erosion, resulting in the shifting of certain concrete wall and floor panels. Dam safety engineers have identified this issue.
  • DWR is ensuring that the spillway functions appropriately, in order to release water in the future if needed. This is to account for potentially larger inflows and uncertainties in the weather pattern. Climate models show that increased temperatures in California will result in more precipitation falling as rain rather than snow, which could alter river flows throughout the state, even during extreme weather events. Recent studies indicate that the spillway is still expected to function as intended if activated during extreme weather events. However, due to the concrete panels shifting, the spillway would not be activated as a result of these shifts. Therefore, the DWR has consistently and carefully managed the water levels in the reservoir over the years.

    • Safety Assessment

    The Safety Evaluation will achieve this goal by creating and assessing programmatic methods to tackle potential dam safety and risk concerns. The objective of the Safety Evaluation is to conduct a comprehensive evaluation of the entire Castaic Dam facility, commencing in early 2022.

  • Discover potential measures to reduce the likelihood of safety concerns related to the dam and improve the reliability and robustness of the dam infrastructure.
  • Assess these therapeutic approaches.
  • Establish programmatic strategies (PA).
  • Suggest a chosen PA for execution.

    • The safety evaluation conducted within the State Water Project, along with the related projects, will guide DWR in prioritizing initiatives that aim to minimize risks during the implementation of the Castaic Dam Modernization Program.

    Earthquake Resiliency Assessments

  • In 2018, DWR conducted a stability analysis, which revealed that the dam structure would remain secure, even in the occurrence of a significant earthquake.
  • Other studies indicate, however, that the large towers (known as outlet structures) which allow DWR to release water from the reservoir are vulnerable to collapsing in a major earthquake. Therefore, reducing DWR’s ability to reliably release water would not be the cause of the dam failing and slowing water delivery to customers.
  • In the event of a significant earthquake, DWR successfully carried out seismic upgrades to the access bridge leading to the outlet structures in order to guarantee the accessibility of personnel.

    • What to Expect

  • DWR closely collaborates with local organizations and state partners to minimize the extent of impacts on recreation. These slightly lower water levels will not affect the water supply. Temporary reduction in water levels may be necessary to conduct various repair efforts on the bridge access and outlet towers. To provide a larger capacity for winter run-off buffer and reduce the likelihood of needing to employ the spillway, the water level of Lake Castaic will be slightly lowered during the winter months. This is a precautionary measure during the modernization process.
  • Throughout all stages of equipment construction, DWR will implement program updates. It is anticipated that there may be heightened activity and localized noise during the efforts to rehabilitate the construction process.
  • DWR expects that it will take approximately 10 years to fully modernize the Program.