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Northern California Dam Emergency Prompts Widespread Downriver Evacuations

Water flows over the auxiliary spillway at the Oroville Dam in Northern California on Saturday.

Water flows over the auxiliary spillway at the Oroville Dam in Northern California on Saturday. Dale Kolke / California Department of Water Resources


Connecting state and local government leaders

Authorities ordered more than 160,000 residents in three counties to flee on Sunday amid fears of a major disaster; a state agency successfully saves millions of endangered fish.

Upwards of 160,000 residents living downriver from the Oroville Dam in Northern California were ordered to leave Sunday after officials warned that an auxiliary spillway was quickly eroding and could suffer a complete failure, potentially leading to an uncontrolled release of water from the second-largest reservoir in the Golden State.

Officials in California have been carefully watching rising reservoir levels in Lake Oroville over many days and have been subsequently releasing water from the reservoir through the main concrete spillway, which had been damaged in earlier storms, in order to reduce the amount of water flowing over the deteriorating auxiliary spillway.

The California Department of Water Resources is dropping rock-filled containers to “strengthen the potential failure point” in the auxiliary spillway.

The 770-foot-high Oroville Dam is the nation’s tallest dam and its auxiliary spillway has never been used since it opened 48 years ago.

More than 162,000 people in Butte, Sutter and Yuba counties were impacted by the evacuation order, The Sacramento Bee reported on Sunday evening.

In Butte County, where the dam is located, residents in Oroville and nearby areas were told to evacuate northward toward Chico. Other communities impacted along the evacuation order included Biggs, Gridley, Loma Rica and Yuba City.

“This in NOT A Drill. This in NOT A Drill. This in NOT A Drill,” the Butte County Sheriff’s Office wrote in a Facebook post on Sunday. The county’s jail was being evacuated “out of an abundance of caution.”

The California Office of Emergency Services activated its State Operations Center in Sacramento to coordinate the state’s response to the situation at the Oroville Dam.

As of 8 p.m. local time on Sunday, water levels in Lake Oroville dropped to 901 feet, meaning that little to no water was flowing over the auxiliary spillway.

Water pours through the main spillway of the Oroville Dam on Sunday. (Photo by Kelly M. Grow/ California Department of Water Resources)

But the risk of a disastrous failure of the auxiliary spillway is not over, The Sacramento Bee reported:

A large section of concrete at the bottom of the spillway had already collapsed by Sunday, the initial cause of the emergency. As more of the main spillway collapses, it could threaten the spillway’s gates and force officials to stop releasing water into the main spillway, [Central Valley Flood Protection Board member Joe] Countryman said. That would likely be catastrophic.

The cost of repairs for the dam’s main spillway could reach $200 million, according to the state’s preliminary estimates.

Millions of Endangered Fish Rescued From Hatchery

Last week, California Fish And Wildlife officials started to organize an operation to evacuate millions of fish from the Feather River Fish Hatchery as murky, debris-laden water from the spillway threatened the survival of the fish at the hatchery.

As the Chico Enterprise-Record reported on Saturday:

The first step was to move about 5 million tiny fish to a hatchery at Thermalito. This involved scooping up the fish with nets and transportation by truck. Help came from hatcheries throughout the state and the work lasted “morning till night” explained Andrew Hughan, public information officer for California Fish and Wildlife.

Among those moved were millions of spring-run chinook salmon, which are listed as threatened on the Endangered Species List.

The evacuation involved the quick construction of a system of 6-foot tall cylinders with high-capacity charcoal filters, pipes and pumps to run water through the filters and into egg trays.

“Engineers are really smart people. They thought ‘what can we do to save millions of fish. It’s just an amazing engineering feat,” Hughan told the Enterprise-Record.

In all, 9 million fish were saved in the operation, the newspaper reported.

Cloudy waters from the damage spillway at Lake Oroville and Oroville Dam forced the California Department of Fish and Wildlife to truck millions of baby salmon from the Feather River Fish Hatchery in Oroville, Calif. to the nearby fish ponds at the Thermalito Afterbay Complex in Butte County. (Photo by Kelly M. Grow/ California Department of Water Resources)

Michael Grass is Executive Editor of Government Executive’s Route Fifty and is based in Seattle.

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