Oroville Dam: Evacuation warnings lifted for Butte County

More than a month after a near-catastrophe at Oroville Dam sparked mass evacuations, Butte County’s sheriff Wednesday lifted the evacuation warning that had remained in place for thousands of downstream residents.

Seriff Kory Honea lifted the warning, saying the situation had stabilized at Lake Oroville in the weeks following the evacuation.

“I feel satisfied with the progress made in reinforcing the primary spillway, emergency spillway and returning the Hyatt powerhouse to an operational state, as well as the successful efforts by the California Department of Water Resources to lower the lake level enough to buffer for future storms,” Honea said in a prepared statement.

An estimated 188,000 residents of Butte, Yuba and Sutter counties were evacuated Feb. 12 amid fears that the dam’s emergency spillway was about to crumble, unleashing a wall of water on communities below. Residents were allowed to return home two days later when the immediate crisis passed, but the sheriff kept the evacuation warning in place until Wednesday.

The problem began when the dam’s main spillway fractured Feb. 7, prompting a temporary shutdown of the structure as a big storm rolled in. The lake rose so high that water began flowing over the emergency spillway for the first time ever. When it appeared the emergency spillway would fail, DWR engineers ramped up outflows from the main spillway enough to reduce lake levels. Since then, crews have fortified both spillways and restarted the dam’s hydro power plant, which was releasing water at about 5,000 cubic feet per second Wednesday. The main spillway was releasing water at 40,000 cfs, for a total outflow of 45,000 cfs. That was slightly higher than lake inflows, keeping water levels well below the top of the emergency spillway.

This story was originally published March 22, 2017 at 12:30 PM with the headline "Oroville Dam: Evacuation warnings lifted for Butte County."