Water & Drought

Can California repair damaged Delta reservoir within 45 days?

A look at repair efforts at the Lake Oroville dam spillway

Images from the state Department of Water Resources show round-the-clock work the week of March 11-17, 2017 at Oroville Dam. A giant fracture developed in Oroville Dam’s main spillway during a heavy storm earlier this year. Five days later, water
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Images from the state Department of Water Resources show round-the-clock work the week of March 11-17, 2017 at Oroville Dam. A giant fracture developed in Oroville Dam’s main spillway during a heavy storm earlier this year. Five days later, water

State officials said Wednesday that Californians reliant on water pumped out of the Sacramento-San Joaquin Delta won’t face supply shortages, even as crews shut down a massive pumping station that serves much of Southern California for at least a month to make repairs to its intake reservoir.

The repair effort involves Clifton Court Forebay, a shallow reservoir that serves as an entryway for a Delta pumping station critical to the State Water Project, the state-run water delivery network that moves water north to south through California. Doug Carlson, a spokesman for the California Department of Water Resources, which operates the pumping plant near Tracy, said that crews discovered damage within the last two weeks on the intake gates at the reservoir. Erosion was scouring the base of a 175-foot-wide concrete “apron” on the intake that sits below the water’s surface.

The apron is attached to radial gates that open when the station’s house-sized pumps are operating, sucking Delta water into the forebay. Given the unusually wet winter, those gates in recent months were opened wider and for longer periods than at any time since at least 2000, according to federal data.

During California’s five-year drought, the state pumps were regularly throttled back by federal regulators to protect endangered fish species. If the river flows in the south Delta aren’t high enough, the powerful pumps can draw endangered fish into the forebay, where they face death from predatory fish or from the pumps themselves.

The powerful river flows this winter allowed for heavy pumping, which in turn caused the intake structure to erode, Carlson said. But he stressed that the shutdown and repairs can be completed without harming south state water deliveries. The prolonged pumping in recent months helped fill San Luis Reservoir in Merced County. That’s a marked contrast to last summer, when the reservoir – which is almost twice the size of Folsom Lake and supplied entirely with pumped-in Delta water – fell to its lowest levels in 27 years.

Carlson said San Luis now has so much water, it can sustain deliveries to the millions of Southern Californians and hundreds of thousands of acres of farmland reliant on water the pumps normally would ship down the California Aqueduct. The state also could ask the federal government to help pipe water to Southern California using the nearby U.S. Bureau of Reclamation’s pumping facility.

Though it’s only about half as powerful as the state pumping facility and has its own set of demands, the federal pumping system can connect to the California Aqueduct through a connector canal.

Demand from farms and cities is relatively low this time of year, and there’s so much water in the system that both state and federal water users say that they don’t expect shortages, as long as the state can meet its promise to have the repairs completed within the next 30 to 45 days.

Carlson said the cost of repairing the facility using concrete injections will be a “few million dollars.” State Water Project contractors will be responsible for picking up the tab.

Ryan Sabalow: 916-321-1264, @ryansabalow

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