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. 

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.

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