Lake Oroville overflows into emergency spillway

Lake Oroville Dam's spillway a massive crater

If the department can't keep using the eroded concrete spillway, Lake Oroville would naturally flow over an ungated concrete crest into the mostly unlined emergency spillway once the reservoir reaches 901 feet elevation.

State officials say water could pour over an emergency spillway at Lake Oroville for the first time ever, a last-ditch alternative that they had been hoping to avoid.

"Basically it's going to be a triage situation".

California workers are scrambling for a second day to rescue millions of baby native salmon from a hatchery that has being buried in mud from a crumbling spillway upstream. Yet flows had to continue as the reservoir continued to rise.

A never-before-used emergency spillway, located down an adjacent hillside, is one possible solution if the reservoir overflows, but Carlson said this option isn't ideal.

The cost could approach $100 million, though department spokesman Doug Carlson said the estimate by a department engineer is an early, ballpark figure.

Crews had cleared the path Friday, so debris wouldn't flow into the Feather River.

State engineers repeated that Oroville's earthen dam - a separate structure from the spillway - was not in any danger.

Croyle said there was no imminent or expected threat to public safety or the integrity of the dam.

As storm runoff into Lake Oroville slowed Thursday evening, operators increased water releases from 40,000 cubic feet per second (cfs) to 65,000 cfs. Engineers don't know what caused cave-in that is expected to keep growing until it reaches bedrock. Its reservoir provides fresh water to much of Central California's farmlands and homes, and businesses in Southern California. The state shut down releases from the spillway for a time but then restarted them to counter inflows to Oroville Lake from the week's storms.

Although inflows decreased Friday and into Saturday morning to 89,000 cubic feet per second, water officials have also decreased outflows to 55,100 cfs, according to KCRA chief meteorologist Mark Finan.

Such a move could have untold ecological consequences for the Feather River below, which is home to the state's largest salmon hatchery.

Workers also are evacuating 1 million eggs of steelhead trout.

An aerial view Friday shows Oroville Dam to the right and the damaged spillway to the left.

"We are in full rescue mode", Hughan said.

Associated Press writers Kristin J. Bender and Ellen Knickmeyer contributed to this story from San Francisco.