The problem at Rollins Dam in Nevada County
When it comes to inspecting dams, California is second to none. A panel of national experts examined the state’s Division of Safety of Dams last year and declared it tops in the field, citing inspectors’ knack for flagging small problems before they turn serious.
Getting dam owners to fix those flaws quickly is another matter.
A Sacramento Bee investigation prompted by the nearly catastrophic failure of Oroville Dam’s flood-control spillway in February found that owners of some of California’s most important dams – those whose failure could cause residents downstream to lose their lives – often allow deficiencies to linger for years – even though these shortcomings get cited repeatedly in annual inspection reports.
Cracked concrete goes unpatched. Rusted equipment goes unrepaired. Sensors that measure pressure inside dams stay broken. Valves and gates that release water from reservoirs remain frozen in place.
Operators sometimes fail to clear out clogged drainage systems critical to maintaining the structural integrity of spillways and dams. They’re also slow to remove trees, brush and other vegetation whose roots can clog drains, weaken earthen dams or undermine slabs of concrete.
State officials said the problems cited by inspectors are almost always insignificant, and don’t require immediate attention. But experts say the consequences from seemingly innocuous shortcomings can be considerable. A team of investigators looking into what caused the devastating fracture of Oroville’s spillway pointed to a drainage system clogged with tree roots as a probable contributing factor.
“These little things add up,” said Jeffrey Mount, an expert on flood management at the Public Policy Institute of California. “Every one of them increases the likelihood of an accident.”
Mount pointed to a nearly forgotten incident at Folsom Dam, where bird droppings helped corrode the support arm of one of the spillway gates. The gate buckled on July 17, 1995, releasing nearly half of the reservoir’s water over the next week or so – a failure that could have proven disastrous for downstream residents in Sacramento if it had happened during the rainy season. While bird droppings weren’t the main reason the gate failed, U.S. Bureau of Reclamation officials said they may have been a contributing factor.
The Bee based its findings on five years of inspection reports by the Department of Water Resources’ Division of Safety of Dams at 93 facilities. Those are the dams where the state directed owners to conduct a “comprehensive review” of their spillways in the aftermath of the Oroville crisis, which forced the evacuation of 188,000 people and is expected to cost $600 million. The reviews are ongoing.
The state singled out those dams, out of 1,249 under its authority, in part because construction records and blueprints suggested problems could be lurking there. No federal dams, such as Shasta or Folsom, are covered; they aren’t under the state’s jurisdiction. Federal inspectors have said they’re conducting reviews of the spillways at federal dams after the Oroville emergency. The reviews are supposed to be completed by Dec. 31.
The state inspection reports, beginning in 2012, revealed a troubling pattern of delay and deferral of maintenance issues.
At Hernandez Dam in San Benito County, a dam employee apologized to a state inspector in July 2013 for not repairing damaged concrete on the spillway, but the problem still hadn’t been fixed when inspectors returned a year later. At Rollins Dam in Nevada County, an outlet valve got stuck when an employee was demonstrating it for inspectors in 2014; it wouldn’t open all the way for at least the next two years. At Iron Canyon Dam in Shasta County, inspectors found standing water in the spillway chute for four straight years, a sign of a blocked culvert.
All but two of the 93 dams on the state’s list are considered “high hazard” facilities, meaning a failure could kill people downstream. Every inspection report reviewed by The Bee pronounced the dams “safe for continued use,” even if the same shortcomings were cited year after year.
Dam owners and state officials insisted that the problems cited by inspectors were minor and didn’t constitute a threat to the integrity or safety of the structures.
Eric Van Deuren, a dam safety official at Pacific Gas and Electric Co., said the utility addresses problems flagged by inspectors in order of seriousness. Inspectors found repeated problems at six different PG&E hydroelectric dams.
“If any of those inspections had revealed dam-safety issues that posed an immediate threat to the stability of the dam or public safety, then PG&E would not have just sat on them,” he said.
In a non-emergency situation, dam owners say it’s appropriate to plan repairs methodically. For instance, it took four years to pinpoint the cause and repair a small leak in a concrete structure adjacent to the spillway at Lopez Dam near San Luis Obispo; the project required remote cameras and specialized concrete mixes.
“Patching a spillway is not like patching a sidewalk in front of your house,” said Mark Hutchinson, the county’s deputy public works director.
Spokeswoman Erin Mellon of the Department of Water Resources said the Division of Safety of Dams allows owners to postpone repairs if they aren’t considered serious or urgent.
“Issues that do not present an immediate dam safety concern, and are related to routine maintenance, are given lower priority and may appear in subsequent inspection reports,” Mellon said in an email.
‘Teeth in the system’
The Bee’s review of inspection reports, obtained through the California Public Records Act, found some problems went unaddressed for years. They ranged in scope from multimillion-dollar repairs to small jobs that could have been dealt with quickly by workers with hand tools.
▪ At least 10 dam owners were told repeatedly to remove vegetation growing in or near spillways or other vital structures.
▪ At least 15 dam owners were told repeatedly about problems with valves, gates and other mechanisms needed to release or take in water. In some cases, dam owners took years to repair or replace busted valves. In others, dam owners failed to comply with a requirement that they open and close the gates and valves at least once every three years in the inspectors’ presence.
▪ At least seven dam owners were told repeatedly to repair damaged concrete, either on spillway chutes, the face of the dams or other major structures.
▪ At least three dam owners were told repeatedly to fix broken or aging sensors that monitor water pressure changes, movements within the dam due to seismic activity, and other important data. At least eight dam owners were told repeatedly to submit overdue data from those instruments.
▪ At least eight dam owners were told repeatedly to address unusually high dam seepage, unwanted sediment buildup or persistently plugged drains.
▪ At least three dam owners were repeatedly told to replace or repair old or corroded equipment.
The documents could contain evidence of even more serious problems. It’s impossible to know, because before giving them to The Sacramento Bee the state blacked out large portions of inspectors’ findings, citing terrorist concerns.
Dam experts say the repeat offenses show the state has to do a better job of cracking down on dam owners whose facilities don’t measure up.
“You’ve obviously got an enforcement problem,” said J. David Rogers, a dam-safety expert at Missouri University of Science and Technology. “The inspections are taking place, but the mitigation measures, the upkeep and maintenance – there must not be a very severe penalty for not doing the things. … There’s got to be teeth in the system.”
Two state legislators who questioned state officials at an Oroville Dam oversight hearing in the spring said they plan to take action in response to The Bee’s findings.
State Sen. Jim Nielsen, R-Tehama, has co-authored a pending bill that would require more frequent and thorough dam inspections. He said he now plans to amend the legislation to force dam owners to deal more quickly with issues cited by inspectors.
“There’s got to be at least more strict oversight of the yearly inspection reports and the followup,” said Nielsen, whose district includes Oroville.
Assemblyman Jim Frazier, D-Discovery Bay, also called for legislative changes. Frazier, a former home builder and concrete contractor, said the sorts of problems inspectors pointed out at dams would have never been allowed to linger at a construction job site.
“In the private sector, if these were ignored, your job would get shut down or red tagged,” he said.
Shrubs and the spillway
Mellon, the DWR spokeswoman, said the Division of Safety of Dams does have an enforcement system – and uses it. Of the 1,249 dams it oversees, 39 are under reservoir restrictions that force dam owners to reduce the amount of water they can store. Legislation enacted this year, following the Oroville emergency, enables DSOD to slap property liens on dam owners or fine them up to $1,000 a day “if unsafe conditions are not corrected in a reasonable manner,” she said.
Last year the 70-employee dam-safety division was given top marks by a team of independent engineers. A review, performed by the Association of State Dam Safety Officials, concluded that California operates “the leading dam safety program in the nation.”
When told of The Bee’s findings, William Bingham, who led the review, said he wasn’t surprised. Even strong dam-safety agencies like California’s have trouble getting dam owners to correct problems quickly.
“California is probably getting more done than most other states,” said Bingham, a dam consultant in Pennsylvania.
Even so, the frantic crisis last winter at Oroville suggests the state’s efforts don’t go far enough.
A decade’s worth of inspection reports at Oroville showed that dam workers removed vegetation cited in state inspection reports, only to allow it to grow back.
Inspectors found trees and brush growing alongside the spillway in 2011 and 2013. A photo accompanying the February 2015 inspection report shows tree limbs dangling over the spillway, in the vicinity of where it cracked two years later. Inspectors noted that the tree was removed by the time a midyear inspection was done a few months later. A January 2017 photo by the Chico Enterprise-Record shows vegetation starting to grow back in roughly the same place, a month before the Oroville crisis.
A deep chasm opened up in the spillway Feb. 7. A team of forensic investigators has said tree roots likely clogged the spillway’s drainage system, causing water to collect underneath the spillway chute. The water may have created upward pressure on one of the concrete slabs, ultimately causing it to fail, the forensic team has said.
Robert Bea, a dam-safety expert at UC Berkeley, said he thinks the state took far too long to remove trees and brush. By the time they were chopped down, the roots were already growing underneath the concrete chute and clogging the drains, he said.
Mount, of the Public Policy Institute of California, said Oroville’s lesson is clear.
“It might be a rusted facility,” Mount said. “It might be a valve which is not operable....It’s not like one big thing, one glaring thing, that causes the problems. It’s the accumulative little things, which increases the probability that one of those little things will be the weak link and then the system fails.”
Dams with repeated inspection problems
Of the 93 dams analyzed by The Bee, these facilities were cited for the same problems multiple times by state inspectors in the past five years:
- Vegetation growing in or near spillways or other vital structures
- Problems with valves, gates and other mechanisms that release or take in water, such as broken valves or failure to open and close gates every three years for the inspectors
- Damaged concrete on spillway chutes, the face of the dam or other major structures
- Broken or aging monitoring sensors or overdue sensor data
- High dam seepage, sediment buildup, or persistently plugged drains
- Old or corroded equipment that should be replaced or repaired