State faces a race on spillway fix

Water officials update lawmakers on repairs at Oroville Dam, discuss hill’s erosion.

SACRAMENTO — California will be racing to finish $275 million in repairs to the Oroville Dam spillways to prepare for the next rainy season, top water officials told lawmakers on Tuesday.

Bill Croyle, acting director of the Department of Water Resources, said the deadline is Nov. 1.

Damage to the spillways in February forced thousands to evacuate downstream from the country’s tallest earthen dam.

Croyle surprised some lawmakers by saying the emergency spillway, a hillside adjacent to the dam, worked as intended by releasing water from the reservoir when it overflowed after heavy rains.

Erosion in the hillside could have caused a concrete wall along the rim of the reservoir to collapse, sending torrents of water into the rivers and towns below.

“Erosion was expected,” Croyle said. “The erosion of the rock,” which helped fortify the hillside and the concrete wall, “was not expected.”

The emergency spillway, which had never been used before, handled far less water than expected before failing.

“That’s a design flaw. Right?” said Assemblyman James Gallagher (R-Yuba City), whose district’s border runs along the dam.

The crisis was averted when officials decided to risk more damage to the concrete spillway, which had also suffered from erosion as tens of thousands of cubic feet of water per second were being released.

Marcus Yam Los Angeles Times WATER FLOWS down the Oroville Dam’s damaged main spillway Feb. 21. The earthen emergency spillway, seen to the left, also failed due to erosion. The spillways will require $275 million in repairs before Nov. 1.

Rich Pedroncelli Associated Press A S S E M B LY M A N James Gallagher, left, confers with Sen. Jim Nielsen in a briefing on the dam. Gallagher called the earthen spillway’s failure “a design f law.”