The Ventura County Grand Jury is calling for tightened oversight of area dams and community education on how to respond to a dam failure after investigating the safety of the critical structures.
The civilian panel examined the condition of more than 20 dams in and adjoining Ventura County and found that 14 could cause significant loss of life and property if they failed.
Four were identified with existing or potential deficiencies by the California Division of Safety of Dams in a review of close to 100 dams that was spawned by the failure of the Oroville Dam spillway last year, jurors said.
Those dams were identified as the Matilija and Santa Felicia dams in Ventura County and Castaic and Bouquet Canyon dams in Los Angeles County.
State officials have deemed Matilija Dam to be in “poor” condition and the other three dams in “fair” condition, the report said.
The rating for 71-year-old Matilija Dam is based on concerns about the structure’s ability to tolerate a 7.5-magnitude earthquake, jurors said in the nine-page report.
“While the analysis did not appear to indicate complete failure, it indicated a likelihood of significant weakening,” the report stated.
State officials’ concerns center on the damage that could be done by multiple earthquakes, said Glenn Shephard, director of the Ventura County Watershed Protection District, which owns the dam.
Public officials have called for removal of the dam for both environmental and safety reasons, but the cost could exceed $100 million.
Shephard said a large chunk of the funding could be forthcoming. A bond measure headed to California voters in November says $80 million may be spent for the removal of the dam and related projects.
In the meantime, the district plans to apply for a $2 million federal grant to do work that will help stabilize the structure. The job involves removing large pieces of concrete on the sides of the dam that remained after a previous construction project.
Jurors also noted problems with the Santa Felicia Dam, an earthen structure on Lake Piru that dates from the mid-1950s.
The dam received a “fair” rating primarily because of deficiencies that make the dam vulnerable if the largest plausible earthquake struck before upgrades are made, the report stated.
Engineers are concerned about what would happen if a quake damaged the conduit that runs under the dam, said Anthony Emmert, assistant general manager of the United Water Conservation District, which owns the structure.
“It is not a concrete dam,” he said. “It could be eroded by flowing water.”
About 300,000 people live downstream of the dam in an area stretching from Piru to the Oxnard Plain, he said.
District officials plan to replace the conduit with one built around the dam and designed for modern earthquake standards, he said.
Jurors noted the district’s efforts to replace the conduit and enlarge a spillway to handle more water in the case of a major flood.
Emmert said it would cost an estimated $100 million to do the work on the spillway and the conduit. The district has perhaps $20 million set aside, he said, and is looking for low-interest loans and federal and state money for the rest.
Jurors also commented on the “fair” ratings for two Los Angeles County dams near Ventura County.
They said the Castaic Dam had three areas that contributed to the “fair” rating and potential weaknesses. All three areas are being analyzed.
The Bouquet Canyon Dam’s rating was reportedly based on an outdated seismic evaluation, jurors said. It is owned by the Los Angeles Department of Water and Power, which has improved the monitoring system and is doing more seismic studies, jurors said.
Besides examining the dams, the grand jury reviewed how a dam failure would be handled by the Ventura County government. They were critical on several scores.
Jurors concluded that plans for responding to dam disasters follow the state’s guidance but provide little or no direction beyond spelling out the process for notifying dam owners and the Ventura County Sheriff’s Office of Emergency Services.
The grand jury also found that methods for notifying people of pending dam disasters relied largely on telephone alert systems that would likely fail in a major earthquake. That was strongly disputed by emergency services officials, who said they use a multimodal system that includes social and traditional media, telephone alerts and contact by officers in person or on public address systems.
Jurors found that public education efforts including information on evacuation routes were lacking. While state officials require inspections, no local monitoring of the status of dams is done, the report stated.
Most of the grand jury’s recommendations were directed toward the sheriff’s emergency services office, which is responsible for countywide disaster response and preparation.
Jurors called for the office to track the progress of remedial actions taken at the Matilija, Santa Felicia, Castaic and Bouquet Canyon dams and make annual progress reports to the Ventura County Board of Supervisors.
Jurors said the emergency services office should consider working with dam owners and cities to pursue placement of signs and sirens within inundation areas and work more closely with state officials to monitor dam safety. Finally, the grand jury recommended that the Ventura County Board of Supervisors direct county public works officials to provide technical assistance to the office.
Assistant Emergency Services Director Kevin McGowan said the office has a history of collaborating with operators of dams and other interests. The agency remains committed to keeping communities informed of dam hazards and is prepared to support and coordinate response and recovery efforts, he said.
Dam operators and the state Division of Safety of Dams have the responsibility and technical capability to monitor and evaluate dam safety, he said. The office partners with these entities to enhance preparedness, he said.
McGowan said sirens may be used for notifications in Piru primarily because of the community’s proximity to the Santa Felicia Dam. Expanding siren notifications and installing signs in areas downstream that would be subject to flooding in a dam failure would need to be studied, he said.
The grand jury required a response from county supervisors and requested them from the Office of Emergency Services and operators of the dams.
July 12, 2018
Ventura County Star
By Kathleen Wilson
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