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Delta Flows: Shutting down Anderson Dam

by Tim Stroshane, Policy Analyst, Restore the Delta

It was alarming, hardball news to hear yesterday that Leroy Anderson Dam—which holds back Silicon Valley’s Anderson Reservoir—is considered by the Federal Energy Regulatory Commission (FERC, a federal dam regulatory) so seismically unsafe that its owner, the Santa Clara Valley Water District , must drain it to the last drop by October 1 this year.

FERC viewed the District (“Valley Water”) as having slow-walked its response to seismic safety concerns, according to the San Jose Mercury News. Anderson Dam is underlain by channel sediments that could liquefy and undermine the dam’s foundation in good-sized (say, magnitude 6.6) earthquake nearby. 

The Calaveras Fault is very close by. In 1984, I felt a 6.2 magnitude quake from that fault where I worked in Mountain View. The usually solid outdoor parking lot asphalt on which I took refuge rippled before my eyes.

Water made available from Anderson Reservoir from now until October 1 will be used in Silicon Valley, to be sure, as it flows down the Coyote River. Valley Water’s Executive Officer Norma Camacho stated that fish, other wildlife, wetlands, and riparian corridors along the river could die without controlled flows released by the dam, unfortunately. 

But until the 235-foot-high dam is reconstructed or retrofitted (at present carrying a $550 million price tag), Valley Water will reach out for other sources of water, especially since California may be heading into a drought: February ends this Saturday with little or no rain statewide, the worst dry February in state history.

In fact, the state Division of Safety of Dams (DSOD) reports that Valley Water has four dams, including Anderson, that have reservoir restrictions placed on them. Almaden (built 1936), Calero (1935), Guadalupe (1935), and Anderson (1950) dams are all assessed as “fair”; Almaden’s restrictions are for hydraulic reasons, while the other three are restricted for seismic reasons. DSOD criteria in its “Dams Within Jurisdiction of the State of California” report for “fair” state that such a dam “has a longstanding deficiency that is not being addressed in a timely manner, is not certified and its safety is under evaluation,” and “is restricted and operation of the reservoir the lower level does not mitigate the deficiency.” Were all four to be ordered drained by FERC or DSOD, Valley Water would be in a world of water supply hurt. 

Safety First

Probably aware of Valley Water’s other problem dams, FERC director of dam safety David Capka wrote, “It is unacceptable to maintain the reservoir at an elevation higher than necessary when it can be reduced, thereby decreasing the risk to public safety and the large population downstream of Anderson Dam.” 

Restore the Delta applauds FERC’s prioritization of public safety of this dam over the District’s continued operation of such a hazardous facility. Flood inundation from Anderson Dam failure immediately threatens Morgan Hill with a wall of water whose sudden release might trap and drown many residents. Downstream along Coyote Creek live disadvantaged communities. These same communities all the way to south San Jose were hit hard by surprise flooding in the winter of 2017, causing many residents to relocate and face emotional and economic hardship—at least some of which could have been prevented with better preparation by Valley Water.

The agency no doubt feels the sting of changing regulatory fortunes before a Trump Administration FERC. Valley Water’s web site, as of Monday February 24, explained the accommodation it had with FERC prior to today’s action: 

“A storage restriction of about 55 feet below the dam crest has been put in place to protect the public, reducing the allowed storage capacity to 52,553 acre-feet. This voluntary restriction exceeds the 45-foot restriction approved by the regulatory agencies (California Division of Safety of Dams and the Federal Energy Regulatory Commission) and was instituted by Valley Water in response to additional findings during the design phase of the Anderson Dam Seismic Retrofit Project (ADSRP). The water district and regulatory agencies believe that this restriction will prevent the uncontrolled release of water in case the dam is structurally damaged after a major earthquake.”

Now FERC is no longer okay with even the 45 foot restriction. The reservoir is to be drained instead.

FERC’s action also raises important questions about seismic stability of the rest of local, state, and federal dams and other facilities. Water agencies at all levels of government have irresponsibly pushed expansion of state and federal water supplies while falling behind on maintaining their own existing facilities, according to the state Division of Safety of Dams. Californians and the rest of the nation learned of this bias toward new facilities at the expense of the old during the Oroville spillway crisis in February 2017. While catastrophic flooding did not occur then, reports made clear that state water contractors prefer to build the tunnels and new dams and reservoirs while ignoring the serious maintenance, seismic retrofit, and repair tasks that must constantly be done to protect the system California has built since the 20th century. 

California State Auditor Elaine Howle found in January 2020 that 102 dams in California have ratings of less than satisfactory when it comes to hazard risk. (See Figure 4 at this link.) “Of those,” Howle wrote, “84 had hazard classifications of significant or above, indicating risk to life or property should the dams fail.” While state law requires dam owners to fix their damned dams when they fall into such disrepair, “funding such repairs is challenging,” acknowledged Howle.

She also found that 650 California dams, over half of the total, still do not have approved “emergency action plans.” Dam owners are also required to submit such plans, which also must include inundation maps. DWR and other local and state water agencies prefer to build new projects like Shasta raise, Sites reservoir, and the Delta “mega-tunnel,” rather than shoulder the fiscal discipline it takes to maintain systems they already rely on. 

You don’t miss your water ’til your well runs dry, goes the old song. It is also true of dams and their reservoirs.

While Howle suggests that the state of California should create funding programs for seismic retrofit, we think the state should make sure that local agencies owning dams pay at least a fair share of the cost of retrofit in order to qualify for retrofit funds. They need to show their stake in protecting the public. These agencies have known all along that California is earthquake country, and that bad dams kill people. In case they forget, the failure in 1928 of the St. Francis Dam in southern California killed over 430 people downstream almost immediately and led the state to establish a division of safety of dams. Some victims’ bodies were recovered later in Mexico, others never. Unfortunately, the collective memory of this catastrophe has atrophied with time.

What’s Next?

Valley Water has long had a diverse water supply portfolio to quench Silicon Valley’s water demand. It relies on groundwater, recycled water, runoff from local creeks to its ten reservoirs (including until today, Anderson), and imported supplies from both the State Water Project and the federal Central Valley Project. For its imports, Valley Water taps the Delta twice: once via the South Bay Aqueduct near Livermore and then again from San Luis Reservoir near Los Banos (whose water comes from the Delta too). 

It also banks water in the Semitropic Water Storage District near Bakersfield. Its banked supplies can be exchanged from Semitropic to users like Kern County Water Agency or Metropolitan Water District of Southern California, and then a like amount of water that would have gone to Kern or Met could then be delivered to Valley Water via the South Bay Aqueduct. Valley Water can make similar arrangements using federal supplies stored at San Luis Reservoir as well.

Currently, Anderson Reservoir has only 29,000 acre-feet at this time, about a third of its capacity. But we fear that the draining of Anderson Reservoir could become an excuse for Valley Water to become more committed to Governor Newsom’s Voluntary Agreements process, the Delta Mega-Tunnel project, and the Trump Administration’s fish-killing biological opinions, rather than cause for self-assessment of their own project priorities over the last ten years. Pursuit of Delta tunnels has been a major distraction among water agencies throughout the state, and including Valley Water, while maintaining and improving local water infrastructure has been a secondary. The result statewide is shown by sinking canals, delays in major water recycling projects, upstream reservoirs filling with sediment. Climate change bodes larger empty reservoir spaces to prevent catastrophic flooding from atmospheric rivers. Yet, we hope Valley Water looks to its tech-innovative community, and its first-rate staff, to outdo Silicon Valley’s impressive record of water conservation and recycling burnished during the 2012-2017 drought. That would give Valley Water a truly resilient water portfolio for a drying 21st century California, an even stronger position once its languishing dams are returned to safe status.