California dam blows; thousands evacuated

In a “very unusual event,” the dam on Lake Oroville fractured, sending some 100,000 people fleeing from the mounting flood. 

More than 100,000 people were told to evacuate their homes after water started flowing over an emergency spillway at the nation’s tallest dam on Lake Oroville. The water began to gush for the first time on Saturday after erosion damaged the Northern California dam’s main spillway.

At one point, the National Weather Service warned that the auxiliary spillway was expected to fail and could send an “uncontrolled release of flood waters from Lake Oroville.” However, by late Sunday night, officials said the immediate threat had passed because water had stopped washing over the emergency spillway, the Los Angeles Times reported.

Officials hoped to avoid using Oroville Dam’s emergency spillway, fearing it could cause trees to fall and leave debris cascading into water that rushes through the Feather River, into the Sacramento River, and on to the San Francisco Bay. Crews prepared for several days, clearing trees and brush.

This was the first time the emergency spillway has been used in the reservoir’s nearly 50-year history. In addition to the emergency spillway, water is also flowing through the main spillway that was significantly damaged from erosion, he said.

“This is a very unusual event for us here in Oroville,” agency spokesman Eric See said on Saturday.

‘Mother Nature Kicking Us a Few Times’

Unexpected erosion chewed through the main spillway earlier this week, sending chunks of concrete flying and creating a 200-foot-long, 30-foot-deep hole that continues growing. Engineers don’t know what caused the cave-in that is expected to keep getting bigger until it reaches bedrock.

Bill Croyle, the Department of Water Resources’ acting director, said officials are continuously monitoring the erosion both on site and through cameras. “This is mother nature kind of kicking us a few times here,” he said.

Croyle said the main spillway will need a “complete replacement” from the damage. Officials noted earlier this week that the cost of repairing the dam could approach $100 million, but they noted the estimate was an early, ballpark figure.

State officials also had been attempting to rescue millions of hatchery-raised fish imperiled by muddy water flowing downstream alongside the damaged spillway after sections of its concrete walls collapsed earlier this week

About 150 miles northeast of San Francisco, Lake Oroville is one of California’s largest man-made lakes, and the 770-foot-tall Oroville Dam is the nation’s tallest. The lake is a central piece of California’s government-run water delivery network, supplying water for agriculture in the Central Valley and residents and businesses in Southern California.

By: AP and World Israel News

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