Oroville Dam, in California in the U.S., has been in the news a lot recently, as further details are uncovered about the dam itself and lawsuits are filed in reaction to the spillway failure last February.
Most recently, news group NBC Bay Area reported it has obtained a memo, sent by DWR to the California Division of Safety of Dams and copied to the Federal Energy Regulatory Commission, that questions whether seven other dams owned and operated by DWR may have “potential geologic, structural or performance issues that could jeopardize their ability to safely pass a flood event.” NBC Bay Area says the memo was written in June 2017 and lists the Del Valle, Castaic, Pyramid, Antelope, Frenchman, Grizzly Valley and Cedar Springs dams. These are earthen or earth and rock dams and are considered high or extremely high hazard. The memo requested a work plan for each dam be submitted for review by September 2017.
On Jan. 17, the law firm of Cotchett Pitre & McCarthy LLP announced that the City of Oroville had filed a lawsuit against the California Department of Water Resources for “decades of mismanagement and notice of potential and actual defects causing the Oroville Dam overflow.” The complaint alleges that “independent, expert reports and accounts of DWR insiders confirmed that the failure was caused by decades of mismanagement and intentional lack of maintenance by DWR.” As of Jan. 31, the firm said more than 40 farmers, businesses and property owners had filed a lawsuit against DWR.
In addition, in late January The Sacramento Bee reported that workers building the dam raised alarms “about the eroded, crumbling rock on which they were directed to lay concrete for the 3,000-foot-long main flood control spillway.” The website reported that “The contractor told the California Department of Water Resources it needed to dig deeper to find stronger rock” but that DWR limited the additional excavation work. In addition, The Sacramento Bee reported that environmental groups urged DWR to reinforce the hillside below the emergency spillway in 2005 but that DWR dismissed the need to complete this work.
On Jan. 26, FERC sent a letter to its licensees in reaction to the final report released earlier that month by the Independent Forensic Team. In that letter, FERC said: “We request that you and your Chief Dam Safety Engineer/Coordinator read this report, share it with your senior executives as well as your dam safety staff and discuss how the findings may apply to your own facilities and overall dam safety program.” Acknowledging the part of the report that indicates flaws missed by the dam owner, regulators and consultants, FERC said, “It is very clear that just because a project has operated successfully for a long period of time does not guarantee that it will continue to do so.”
Also on Jan. 26, California DWR provided a cost update that indicated emergency response and recovery effort costs of $870 million. This covers completion of the project through January 2019 and includes $710 million for emergency recovery and $160 million for emergency response. Recovery work includes $500 million for work on the main and emergency spillways and $210 million for debris and sediment removal, power line replacement, permitting and development of access roads, staff time, technical consultants and inter-agency support. However, DWR says, “Cost estimates are based on projected work and may evolve as work continues.”
DWR reports Phase Two construction on the main spillway is expected to start in May and includes removing the original 730 feet of the upper chute leading to the radial gates and replacing it with structural concrete, placing a 2.5-foot layer of structural concrete over the roller-compacted concrete middle chute and removing the RCC walls in the middle chute and replacing them with structural concrete walls, and hydro-blasting and resurfacing the energy dissipaters at the base of the main spillway.