THIS JUST IN … California Division of Safety of Dams releases updated information on state’s dams

Data Will Further Guide Efforts to Strengthen Critical Infrastructure

From the Department of Water Resources:

The California Division of Safety of Dams (DSOD) today released updated information on 1,249 dams under its jurisdiction, including downstream hazard classification, condition assessment, and reservoir restriction status for each dam.

The information reflects the most recent physical inspections and comprehensive re-evaluations by DSOD engineers and engineering geologists, as well as technical analyses performed by dam owners.

“In light of lessons learned from the Lake Oroville spillways incident, we know there is work to do to expand and strengthen our dam safety program,” DSOD Chief Sharon Tapia said. “Aging infrastructure is a serious concern, with half the dams in our jurisdiction at least 50 years old. This information will help prioritize where investments in dam safety need to be made.”

Today’s action is part of the state’s ongoing efforts as a dam safety leader and furthers Governor Edmund G. Brown Jr.’s four-point plan to bolster dam safety by making information readily accessible. It also helps carry out legislation signed by the governor earlier this year requiring dam owners to update emergency action plans and inundation maps to incorporate new information.

DSOD works closely with dam owners to identify and correct potential issues on an ongoing basis. Dam owners are responsible for the proper operation, maintenance, and repair of their dams, and for any associated cost.

Downstream Hazard Classification

The downstream hazard classification identified for each dam is based solely on the size of the dam’s reservoir and population that would be impacted by a dam failure; it does not reflect the condition of the dam or its structures.

The hazard classification is used in part to prioritize development of inundation maps and emergency action plans. Dams are classified as high or extremely high hazard if at least one person is at risk downstream in the event of a dam failure. By that definition, 670 dams (54 percent) of those under DSOD’s jurisdiction are classified as high or extremely high hazard.

Condition Assessments and Reservoir Restrictions

DSOD dam condition assessments are based on five condition ratings from the U.S. Army Corps of Engineers National Inventory of Dams, with some minor modifications. The ratings include satisfactory, fair, poor, unsatisfactory, and not rated. Dams rated as satisfactory have no identified deficiencies. Dams rated as fair, poor or unsatisfactory have at least one identified deficiency.

  • Currently 1,151 dams (92 percent) within DSOD’s jurisdiction are rated satisfactory, meaning they have no identified deficiencies. Ninety-seven dams (less than 8 percent) within DSOD’s jurisdiction have a deficiency with a current condition assessment of fair, poor, or unsatisfactory.  Forty-four of those dams have a seismic deficiency.
  • Of the 97 dams with deficiencies, DSOD records show repairs are underway by the owners on 63 dams. Records show repairs are delayed or progress unsatisfactory on the remaining 34 dams.
  • Dam condition assessments may change from year to year as repair work is completed or new deficiencies are identified.
  • DSOD may require that reservoir storage be reduced (restricted) to a specific level if unsafe conditions exist.

 Additional Dam Safety Information

In the wake of the Lake Oroville spillways incident, DSOD initially prioritized spillway re-evaluations for 93 dams with spillways similar to Lake Oroville’s. Owners of those 93 dams were notified this spring of requirements to submit a work plan to investigate the condition of their spillways. DSOD’s re-evaluations of those spillways are now underway.

Over the past 20 years, DSOD has focused its attention on conducting in-depth re-evaluations of dams located near active faults and in densely populated areas. Re-evaluations are more comprehensive than physical inspections and typically require many years and millions of dollars to complete. DSOD re-evaluations in the last two decades have resulted in dam owners investing over $1.5 billion in repairs to reduce the risk of dam failures due to earthquakes.

“Dam safety is a collective effort,” Tapia said. “While owners are responsible for the safety of their dams, we need public and policymaker support to advance strong dam safety regulations and secure funding for this critical work.”

Statement from DWR about California Dams Rating Information

The California Department of Water Resources (DWR) released this statement from Director Grant Davis in response to the rating information released today by the California Division of Safety of Dams (DSOD):

“We are in an era of aging infrastructure in California, which requires a stronger approach to evaluating and investing in the facilities that residents and the economy depend on. Public safety is not negotiable, and the integrity of our dams and levees must be among the highest priorities for California.

“We cannot live in a risk-free world, so it’s imperative that we use the most effective technology and information to avoid problems wherever possible.

“Based on what we’ve learned in Oroville and what we will learn soon from the Forensic Team’s report, DWR will strengthen the re-evaluation and maintenance of the dams that we own. This approach requires additional commitment and prioritization of personnel and fiscal resources, which – though expensive – will be a fraction of the cost of recovery should another crisis occur. These include:

  • Evaluating the spillways at all dams owned by DWR to identify where potential causes of the Lake Oroville spillways failure may also be present, and make necessary repairs. Many of these evaluations are already underway due to the new spillway evaluation requirement from the Division of Safety of Dams.
  • Prioritizing our personnel resources to expedite critical repairs on dams owned by DWR.
  • Active contribution to the development of information and protocols for the next century of dam safety. As the innovation and technology hub of the world, California must take advantage of the best minds in science, engineering, and technology to set new standards for dam construction, management and safety. DWR will expand on our current partnerships with academia, dam safety organizations, Federal and State regulators, and other dam owners to establish a best-in-class program.

“DWR encourages all dam owners in California to take a similarly aggressive approach to dam safety, and we look forward to working with them as we learn and share information.”

 

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