Water agency warned them half-decade ago

warnings via reverse 911 calls to residents. But local officials say the state hasn’t tackled other steps that could improve residents’ response, such as providing routine community briefings and improving escape routes.

The catastrophic scenario of a sudden breach at California’s second-largest water reservoir, outlined between 2010 and 2012 in online archives of federal dam regulators, is a different and far graver situation than the concern that prompted sudden evacuation orders Sunday for 188,000 downstream residents.

Operators of the nearly half-century-old dam in California’s Sierra Nevada foothills became worried that the water cascading from the reservoir after a series of winter storms could roar uncontrolled

OROVILLE, Calif. — California officials further slowed the release of water Friday from a lake behind the nation’s tallest dam so crews can remove debris from the bottom of the structure’s damaged spillway.

Officials had been releasing 100,000 cubic feet of water, or enough to fill an Olympic-size swimming pool, each second from the lake since Sunday, when the sheriff ordered an immediate evacuation for towns downstream from the dam.

The amount being released was reduced to 80,000 cubic feet of water per second late Thursday, and further reduced on Friday. By Saturday, dam managers expect to be releasing 60,000 cubic feet per second, said Bill Croyle, acting director of the Department of Water Resources.

With less water careening down the crippled spillway, construction crews can move in to remove debris that is causing water to pool at the base of the dam. down a rapidly eroding emergency spillway toward towns downstream.