Department of Water Resources personnel, left, inspects a hole was torn in the spillway of the Oroville Dam while releasing approximately 60,000 cubic-feet-second of water in advance of more rain on February 7, 2017 in Oroville, California. (Photo: Max Whittaker/Prime, Special To The Chronicle)

By Joaquin Palomino and Cynthia Dizikes, San Francisco Chronicle
February 19, 2017
Updated: February 19, 2017 – 12:05pm

The dam burst on a warm afternoon, unleashing nearly 300 million gallons of muddy water on a Los Angeles neighborhood. Five people died and dozens of homes were swept off their foundations and destroyed.

In the aftermath of the 1963 Baldwin Hills Dam catastrophe, the state strengthened inspection regulations, helping establish California as a modern leader in dam safety.

That reputation was called into question last week, however, as two spillways at the towering Oroville Dam north of Sacramento began to crumble in the wake of heavy rains and snowmelt, forcing tens of thousands of people to evacuate. Though the dam — the tallest in the nation at about 770 feet — had been regularly inspected and cleared as safe, both spillways eroded when carrying relatively small amounts of water.

The 50-year-old structure’s apparent fragility took many by surprise, prompting calls for more robust inspections, maintenance and emergency planning at all of California’s 1,585 dams — aging facilities that likely will be tested more severely in the coming years by global warming and anticipated periods of intense rain.

Despite those concerns, a Chronicle review of federal data found disturbing deficiencies in California’s dam-safety efforts.

As of October 2015, about a dozen state-monitored dams where failure could result in death or property destruction had gone more than two years between inspections, though checks are supposed to be done once a year. Home to some of the country’s biggest dams, California also lags behind the national average in emergency preparedness for dam failure, with hundreds of high-risk sites lacking plans to handle a potential crisis.

“It is reason for alarm,” said Robert Bea, a professor emeritus and engineering expert at UC Berkeley. “If systems are in the very old, geriatric phase, inspections need to be annual.”

Officials with the Department of Water Resources, which inspects most dams in California, defended their safety program as well-funded and robust. In recent years, they said, they have worked with more than 100 dams to prepare emergency plans and currently have about $2 billion worth of repair projects under way.

“In California, detailed reviews of dams is based on highest priority and greatest need, with public safety as the first priority,” department officials wrote in an email.

A 2016 peer review conducted by the Association of State Dam Safety Officials at the request of the Department of Water Resources concluded that California had the leading dam safety program in the country, noting that most high-risk dams were monitored by a “very well-documented and rigorous” state inspection program.

One in 3 dams in California was built in the 1950s and 1960s, when the bulk of the state’s sprawling water system was put in place. Since then, entire towns have popped up downstream from the aging facilities, making inspections and maintenance increasingly important, experts say.

California routinely monitors most of its dams, including Oroville, which is designated as “high-hazard” — meaning failure or misoperation would likely result in people dying.

State-regulated dams that could pose safety risks to people or property are supposed to be inspected at least once a year, but can go essentially 24 months between reviews if inspected at the beginning of one year and the end of the next. Those examinations often include visual checks to see if anything obvious is amiss and measurements of issues like seepage and water pressure.

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