NID owns and operates 15 dams under the jurisdiction of the California Department of Water Resources Division of Safety of Dams (DSOD). All of these dams, with the exception of Loma Rica Airport and Deer Creek, are also under the jurisdiction of the Federal Energy Regulatory Commission (FERC).
NID performs weekly visual dam safety inspections, detailed dam safety inspections, and monthly dam instrumentation readings. During the winter months, when some of the higher elevation dams are not accessible, aerial inspections are performed by helicopter about once a month. Horizontal and vertical displacements of the dams are surveyed by NID according to survey intervals set for each dam, with the exception of Loma Rica Airport, Jackson Lake, and Milton Diversion dams.
Both DSOD and FERC perform their own annual dam safety inspections of these dams. In addition, FERC requires dam owners to hire an independent consultant to inspect the dams and perform a Potential Failure Mode Analysis every 5 years. Other supporting documents and reports are often updated during the 5 year independent consultant inspection and evaluation.
The regulatory inspections and evaluations often result in the need for the District to perform additional studies or work to maintain the safety of the dams. Inundation maps are required to be updated every ten years, or when significant changes are made to the dam, appurtenances or downstream conditions. Emergency action plans are updated annually and a tabletop exercise is performed with local public safety agencies. The District maintains a Dam Safety Surveillance and Monitoring Plan that details the surveillance and monitoring procedures for each jurisdictional dam and submits revisions to both regulatory agencies when updates are required. The District prepares and annual Dam Safety Surveillance and Monitoring Report which documents and discusses the annual performance of monitoring equipment and findings from surveillance for the jurisdictional dams and submits it to both DSOD and FERC. The District provides internal dam safety training to staff annually.
Additional information on the supervision and regulation of District dams can be obtained from the California Department of Water Resources, Division of Safety of Dams or the Federal Energy Regulatory Commission, Division of Dam Safety and Inspections, at the following links:
Annual Dam Safety Updates
The following files provide a summary of the dam safety related activities undertaken by the District in a given year. New annual summaries will be added in April of the following year.