On the day the massive hole in the Oroville Dam spillway was discovered, the California Department of Water Resources issued a report detailing a separate and very real threat to the state’s vital water delivery system.
Because of overpumping to irrigate crops during the drought, large swaths of the Central Valley in and around Chowchilla, Corcoran and the Fresno County town of Tranquility subsided rapidly in 2015 and 2016.
Land subsidence in the Central Valley and the gaping hole that appeared in the spillway at Oroville Dam are not connected in any direct way. But they are of a piece. California’s plumbing system, largely built five decades ago, is outdated and in distress. We will face a reckoning sooner rather than later.
The causes of the damage to the spillway at Oroville Dam and the repair costs are to be determined. But today, and for the rest of the rainy season, operators of the nation’s tallest dam and the state’s second largest reservoir will be earning their pay and then some.
Although residents downstream along the Feather River and beyond can be forgiven if they are getting nervous, experts say there is no significant chance that the dam itself will fail, as happened earlier this week when the earthen 21 Mile Dam failed outside Elko, Nev.
They say the Oroville Dam and concrete spillway have been inspected regularly and that there were no particular warning signs before the concrete began falling away in chunks.
At least initially, they say, the incredible power of water cascading down the spillway opened the crevice. But the dam was commissioned in 1968. Since then, materials have improved. And the materials in use have become stressed by nearly 50 years of operation.
As anyone who has bounced over our rutted roads knows, California has not adequately maintained and replaced its aging infrastructure. Thirst for water exceeds the supply, as became painfully clear during the five years of drought, when farmers pulled water from ever-deeper wells.
As aquifers are depleted, the land slumps, including the land beneath the California Aqueduct, which warps it. The Department of Water Resources is studying the impact of subsidence along the 444-mile-long aqueduct, which supplies water to 25 million people and a million acres of farmland. Clearly, subsidence isn’t helpful.
What hydrologists call “subsidence bowls” now span hundreds of square miles. Some land has sunk 20 inches. Subsidence has damaged the aqueduct to the point where the amount of water that can be conveyed by one section has been reduced by 20 percent.
Along the Delta-Mendota Canal, which is part of the federally operated Central Valley Project, the ground has sunk by as many as 22 inches. Subsidence also threatens the Eastside Bypass, a flood control feature on the San Joaquin River in Fresno County. The department estimates the cost of acquiring easements and reinforcing levees to counter the effects of subsidence could total $250 million.
As if to place an exclamation point on it all, Jerry Brown’s administration submitted a wish list of 51 road, water and other projects to the National Governors Association, taking President Donald Trump up on his pledge to fund public works projects.
The projects include raising Folsom Dam and buttressing Sacramento-area levees. Altogether, the 51 projects would cost $100 billion, not counting the cost of repairing the Oroville Dam spillway. Whatever that sum turns out to be, this we know: The bill has come due.