Oroville Dam spillway failure (2017)
February 2017: the main spillway of the tallest dam in the United States erodes, the emergency spillway scours, nearly 190,000 people are evacuated. Repairs: 1.1 billion dollars.
On February 7, 2017, with the Feather River in flood, a slab of the main spillway at California's Oroville Dam lifts and a crater opens in the chute. The operator, the Department of Water Resources (DWR), cuts releases; the lake rises and, on February 11, water flows for the first time since the dam opened over the emergency spillway, a weir followed by an unlined hillside. Erosion works its way back toward the weir. On February 12, the evacuation order: nearly 190,000 residents downstream, in Oroville, Marysville and Yuba City. The weir holds. The independent forensic team, in January 2018, found no single cause. The chute had design and construction weaknesses dating from the 1960s, the foundation rock was poor, water entering through cracks and joints lifted the slabs, and the report speaks of a "long-term systemic failure" of DWR, its regulators and industry practice. The bill, put at 1.1 billion dollars by DWR in September 2018 for both spillways, was fought out between the State of California and Washington. In March 2019, FEMA, which reimburses up to 75% of the costs of a declared disaster, denied 306 million of work on the upper part of the main spillway, on the grounds that the damage predated the flood. California appealed. The reasoning is that of a property adjuster separating a sudden event from wear and design defect, and it weighs on every aging water structure: the flood exposed a defect older than itself. The hydroelectric plant at the foot of the dam had to shut down, as debris piled up in the river raised the tailwater level: a textbook case of lost generation caused by damage to a neighboring structure.
Textbook case, in numbers. A public operator repairs a spillway for 1,100 million dollars. Federal aid reimburses 75% of eligible costs, but the reviewer finds that 40% of the work corrects defects that predated the flood. Eligible costs: 1,100 x 0.6 = 660 million. Reimbursement: 660 x 0.75 = 495 million. Left with the operator: 1,100 - 495 = 605 million. Add the shutdown of the powerhouse at the foot of the dam, 60 days at 4,000 MWh a day sold at 40 dollars: 60 x 4,000 x 40 = 9.6 million, which federal aid does not cover.
Oroville Dam crisis, Oroville spillway incident, Oroville 2017, Lake Oroville spillway failure
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