Thursday, July 12, 2018

Grand Jury on Dam Safety

New information has been released on dam safety in Ventura County.  A report compiled by the Ventura County Grand Jury finds that there does not appear to be any effort by the dam owners or the OES to educate the public as to the potential inundation areas, evacuation routes, or what to do in the event of a dam failure.

The report summary states:

In light of the 2017 failure of the spillway at Oroville Dam, the 2017-2018 Ventura County Grand
Jury (Grand Jury) investigated the condition of more than 20 dams in or adjoining Ventura County. The Grand Jury found that 14 of these dams could cause significant loss of life and property if they failed. Four of these dams, all under the jurisdiction of the State of California Division of Safety of Dams (DSOD), are identified as having existing or potential deficiencies. The Grand Jury investigated the reasons for the deficiencies and what efforts are being made to correct them.

On Matilija Dam, the Grand Jury discovered that:

FA-07. The Ventura County Watershed Protection District (VCWPD) owns and operates the Matilija Dam [capacity 3,800 acre-feet], which received a “Poor” rating by the DSOD. The DSOD rating was based on concerns as to the ability of the dam, specifically issues related to the wing walls, to withstand a 7.5 magnitude earthquake. While the analysis did not appear to indicate complete failure, it indicated a likelihood of significant weakening. VCWPD’s subsequent analysis did not indicate the same level of damage. Even so, the VCWPD, with concurrence from DSOD, agrees that removing the upper wing walls could significantly stabilize the dam. For that reason, VCWPD has applied for a $2-million hazard mitigation grant from FEMA to remove the wing walls. The district is continuing its quarterly monitoring program of the dam and will be taking core samples later this year to ensure that it has up-to-date information as to the dam’s integrity.

FA-08. The VCWPD is working on a plan to remove Matilija Dam. The plan faces technical and environmental challenges and has yet to be finalized or approved by regulatory agencies. The VCWPD would use property tax money and is seeking additional funding to complete the demolition. Depending on the method used to dismantle the dam and dispose of the sediment, the costs could range from $111 million to $208 million. Funding has not been obtained, and the removal has not been environmentally cleared. (Ref-07, Ref-08)

FA-09. There are roughly 8 million cubic yards of debris behind Matilija Dam. There is a concern that a big storm will push huge amounts of mud and water over the top, overwhelming bridges, culverts and roads below. (Ref-09)

C-02. The Grand Jury concluded that the VCWPD has identified structural issues regarding the Matilija Dam. The district is working to remove the dam. Pending obtaining funding and final approval of required environmental clearances, the dam may continue to be a threat. (FA-07, FA-08, FA-09)


R-01. The Grand Jury recommends that the OES track the progress of remedial action taken at Matilija Dam, Santa Felicia Dam, Castaic Dam, and Bouquet Canyon Dam. Reports of progress should be made to the BOS annually. (C-01, C02, C-03, C-04, C-05)
R-02. The Grand Jury recommends that the OES consider working with dam owners and cities to develop and widely distribute dam failure inundation maps and other information to assist residents in planning for responses to dam failures. (C-06, C-07, C-08)
R-03. The Grand Jury recommends that the OES consider working with dam owners and cities to pursue placement of signage and sirens within the inundation areas. (C-07, C-08, C-09)
R-04. The Grand Jury recommends that the OES work more closely with DSOD to monitor and evaluate safety for dams in or affecting Ventura County. (C-10)
R-05. The Grand Jury recommends the BOS direct the Public Works Department to provide technical assistance, as appropriate, to the OES, augmenting its expertise in dam safety and operation. (C-10)

In the news: 

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.


Select references from this report listed here for convenience:

Ref-03. Ventura County OES Web page on Dam Failure

Ref-04. Flood Mitigation Plan for Ventura County, California, Ventura County Watershed Protection District. March 1, 2005.

Ref-08. Matilija Dam Removal and Ecosystem Restoration Project Funding Plan, April 2017. Matilija Dam Design Oversight Group. Matilija Dam Removal and Ecosystem Restoration Funding Plan April 2017

Ref-09. Ojai residents take stock of their blessings and vulnerability after surviving the Thomas fire. Louis Sahagun, Los Angeles Times, January 8, 2018. fire-20180108-story.html