Feds order South Bay reservoir drained amid fears of catastrophic dam failure
By Bob Egelko and Michael Cabanatuan
SF CHRONICLE
Video by ABC 7 San Francisco
Federal water officials have ordered Silicon Valley’s chief water supplier to start draining its largest reservoir by Oct. 1 because a major earthquake could collapse the dam and send floodwaters into communities from Monterey Bay to the southern shore of San Francisco Bay.
But Valley Water, the agency that manages the Anderson Dam and Reservoir, says it has already lowered the reservoir’s water below the level initially sought by federal officials — and that the total drainage the federal government now demands would actually make the dam more vulnerable to earthquake damage, while also reducing water supplies and causing environmental harm.
The reservoir, in a gorge 3 miles east of U.S. 101 between Morgan Hill and San Jose, is one of 10 storing water for the Santa Clara Valley Water District, now known as Valley Water. Built in 1950, it can hold 89,073 acre-feet of water, more than half of the 170,000 acre-feet stored in all of the district’s reservoirs.
Valley Water officials have known since 2008 that a 6.6 magnitude earthquake on the Calaveras Fault at the 240-foot earthen dam could cause it to collapse. Over the years, the agency has lowered water levels and reported its progress to the Federal Energy Regulatory Commission.
The reservoir, at current levels, “provides a buttressing effect” for the dam’s intake structure, Christopher Hakes, a Valley Water dam safety official, said in a Dec. 31 letter to FERC. “Lowering reservoir levels beyond the current level would decrease the structural reliability of the intake structure” and its protection against earthquakes.
FERC’s dam safety director, David Capka, was unconvinced. He ordered Hakes in a letter Thursday to drain the reservoir “as quickly as you can,” starting the process by Oct. 1 and completing it before the winter of 2021-22. In the meantime, Capka said, Valley Water can look for emergency water supplies and work with federal, state and local agencies to “minimize environmental impacts.”
“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,” Capka wrote. “Your actions to date do not demonstrate an appropriate sense of urgency.”
Video by ABC 7 San Francisco
Federal water officials have ordered Silicon Valley’s chief water supplier to start draining its largest reservoir by Oct. 1 because a major earthquake could collapse the dam and send floodwaters into communities from Monterey Bay to the southern shore of San Francisco Bay.
But Valley Water, the agency that manages the Anderson Dam and Reservoir, says it has already lowered the reservoir’s water below the level initially sought by federal officials — and that the total drainage the federal government now demands would actually make the dam more vulnerable to earthquake damage, while also reducing water supplies and causing environmental harm.
The reservoir, in a gorge 3 miles east of U.S. 101 between Morgan Hill and San Jose, is one of 10 storing water for the Santa Clara Valley Water District, now known as Valley Water. Built in 1950, it can hold 89,073 acre-feet of water, more than half of the 170,000 acre-feet stored in all of the district’s reservoirs.
Valley Water officials have known since 2008 that a 6.6 magnitude earthquake on the Calaveras Fault at the 240-foot earthen dam could cause it to collapse. Over the years, the agency has lowered water levels and reported its progress to the Federal Energy Regulatory Commission.
The reservoir, at current levels, “provides a buttressing effect” for the dam’s intake structure, Christopher Hakes, a Valley Water dam safety official, said in a Dec. 31 letter to FERC. “Lowering reservoir levels beyond the current level would decrease the structural reliability of the intake structure” and its protection against earthquakes.
FERC’s dam safety director, David Capka, was unconvinced. He ordered Hakes in a letter Thursday to drain the reservoir “as quickly as you can,” starting the process by Oct. 1 and completing it before the winter of 2021-22. In the meantime, Capka said, Valley Water can look for emergency water supplies and work with federal, state and local agencies to “minimize environmental impacts.”
“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,” Capka wrote. “Your actions to date do not demonstrate an appropriate sense of urgency.”
© Tom Stienstra, Tom Stienstra / The Chronicle
Coyote Creek downstream of the outlet from Anderson Dam near Morgan Hill west of U.S. 101.
In response, Valley Water’s chief executive, Norma Camacho, said in a statement Monday that “the demand to empty Anderson Reservoir could result in unsafe consequences.”
But the local district lacks authority to defy federal regulators. Valley Water spokesman Matt Keller said the district’s Board of Directors would address the issue shortly.
The district is due to start work in 2022 on a five-year earthquake retrofit for the dam. Camacho said legislation has been introduced in Sacramento to speed up the regulatory process for the retrofit.
The district reduced the storage level of the reservoir to 68% of capacity in 2008, then to 58%. It says it has now lowered the level to 45 feet above drainage, 10 feet below the level demanded by Capka in December.
Still, a spillover from the dam during heavy rains three years ago sent water pouring down Coyote Creek and into San Jose, inundating neighborhoods in one of the region’s worst floods in decades.
The district has alternate sources of water, including the State Water Project and the federal Central Valley Project, which combined furnish more than half its supply, along with groundwater.
But Camacho, the chief executive, said draining the reservoir would not only be unsafe but also environmentally destructive.
“The inability to keep a consistent flow in Coyote Creek downstream of the dam year-round would significantly impact sensitive native fish, amphibians, reptiles, wetlands, and riparian habitats,” she said. “Water quality could also be significantly impacted downstream of the dam.”
The dispute coincided with, but was apparently unrelated to, the latest round of water wars between the Trump administration and California.
On Thursday, the state sued the federal government over new rules that supply more water to Central Valley farmers by increasing pumping from the Sacramento-San Joaquin River Delta. The suit said the diversion violates environmental laws and would harm salmon and other endangered fish in the delta estuary.
Coyote Creek downstream of the outlet from Anderson Dam near Morgan Hill west of U.S. 101.
In response, Valley Water’s chief executive, Norma Camacho, said in a statement Monday that “the demand to empty Anderson Reservoir could result in unsafe consequences.”
But the local district lacks authority to defy federal regulators. Valley Water spokesman Matt Keller said the district’s Board of Directors would address the issue shortly.
The district is due to start work in 2022 on a five-year earthquake retrofit for the dam. Camacho said legislation has been introduced in Sacramento to speed up the regulatory process for the retrofit.
The district reduced the storage level of the reservoir to 68% of capacity in 2008, then to 58%. It says it has now lowered the level to 45 feet above drainage, 10 feet below the level demanded by Capka in December.
Still, a spillover from the dam during heavy rains three years ago sent water pouring down Coyote Creek and into San Jose, inundating neighborhoods in one of the region’s worst floods in decades.
The district has alternate sources of water, including the State Water Project and the federal Central Valley Project, which combined furnish more than half its supply, along with groundwater.
But Camacho, the chief executive, said draining the reservoir would not only be unsafe but also environmentally destructive.
“The inability to keep a consistent flow in Coyote Creek downstream of the dam year-round would significantly impact sensitive native fish, amphibians, reptiles, wetlands, and riparian habitats,” she said. “Water quality could also be significantly impacted downstream of the dam.”
The dispute coincided with, but was apparently unrelated to, the latest round of water wars between the Trump administration and California.
On Thursday, the state sued the federal government over new rules that supply more water to Central Valley farmers by increasing pumping from the Sacramento-San Joaquin River Delta. The suit said the diversion violates environmental laws and would harm salmon and other endangered fish in the delta estuary.
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