The California Division of Safety of Dams is requesting that dam owners in the state assess dam appurtenant structures, including spillways, to confirm they meet minimum safety standards.

This is part of the Spillway Re-Evaluation Program, which was established in 2017. This “on-going screening process and re-evaluation of spillways at dams” starts with those that potentially pose the highest hazard, DSOD says. The evaluation includes the assessment of:

The spillway’s design and construction and geologic attributes while concurrently reviewing the dam owner’s maintenance and inspection program

The spillway’s historical performance

Any previous spillway repairs

DSOD says it is “working closely with dam owners to expedite the development of the required assessments and restore any known areas of disrepair.”

Dam owners have received a spillway notification letter as part of DSOD’s first phase condition assessment request:

“As a result of the recent major incidents at Oroville Dam, which led to significant damage and erosion of the Service and Emergency Spillways, Governor Brown issued a plan to bolster the State’s dam safety program. To strengthen the State’s inspection program, the Governor has ordered detailed evaluations of dam appurtenant structures, such as spillways. This new review is being expedited for dams that have large spillways and structures similar to Oroville Dam. Based on this directive, the Division of Safety of Dams is immediately conducting detailed re-evaluations of large spillways at high-hazard dams.”

DSOD came into existence as a result of the St. Francis Dam failure in southern California in 1028. The division operates under the California Department of Water Resources, and its engineers and engineering geologists review and approve plans and specifications for the design of dams and oversee their construction to ensure compliance, as well as inspect more than 1,200 dams on a yearly schedule to ensure they are performing and being maintained in a safe manner.

On June 7, California DWR provided an update on the status of rehabilitation work at Oroville Dam. The agency said prime contractor Kiewit Infrastructure West has been focusing on removing the lower 2,000 feet of the main spillway and removing the last 600 feet of the upper chute, leaving in place the 1,000 feed that leads to the radial gates. In addition, the Board of Consultants has approved DWR’s final design of the reconstruction and repair to the main and emergency spillways.

Hydro Group Associate Editor Gregory B. Poindexter spoke with William A. Croyle, acting director of California DWR, in April to get an update on the situation at Oroville Dam. Below is an audio clip from that interview.