Signs Of Hope At Oroville Dam, After Overflow Sparked Large Evacuation Sunday

Enlarge this image toggle caption William Croyle/California Department of Water Resources via AP William Croyle/California Department of Water Resources via AP

The area around a huge dam at California's second-largest reservoir is in a state of emergency, with some 180,000 residents ordered to evacuate the area Sunday out of fears that part of Oroville Dam could fail. A glimmer of hope arrived late Sunday night, when officials said water had finally stopped pouring over the dam's emergency spillway.

The secondary spillway was in use because the main spillway had developed a huge hole, stressed by the need to release water accumulated from California's wet winter — and brought to a new crisis point by last week's heavy rains.

"So the lake rose 50 feet in just a few days," Dan Brekke of member station KQED tells Morning Edition, "and got up to this emergency spillway which had never been used since the dam went into service in 1968. And on Saturday morning, it began pouring over there."

Signs Of Hope At Oroville Dam, After Overflow Sparked Large Evacuation Sunday Listen · 4:04 4:04

Residents of the area some 70 miles north of Sacramento were placed under evacuation orders around 4:30 p.m. Sunday, after the reservoir rose to a record level — more than a foot above what's considered "full" — and its main spillway struggled to provide relief and its auxiliary spillway was seen at risk of failing. At the time, officials said that dangerous flooding could be just hours away.

Even as the evacuation orders were issued, officials had reason to hope that Lake Oroville would soon begin to recede, due to a drop in the amount of runoff water entering the lake and a dry weather forecast. But the reservoir's infrastructure was struggling to cope.

"The lake is considered full at 901 feet [above sea level], and it's at that level that it began pouring over an emergency spillway early Saturday," KQED reports.

The lake kept rising, surpassing its "full" level by more than a foot. Last night, Lake Oroville's water level finally dropped below 900 feet around midnight, in a trend that has continued into Monday morning.

Enlarge this image toggle caption Florence Low/Florence Low / California Department of Water Resources Florence Low/Florence Low / California Department of Water Resources

As for the residents and evacuees, Brekke says he has seen many confused, scared people — one woman's son, he says, compared the evacuation to a zombie apocalypse. And another woman said she's still worrying over the family members who weren't able to leave.

That resident, Marilyn McKinney, told Brekke:

"My daughter-in-law is still there with her sister, who is bedridden, but we've got her in a wheelchair. They were supposed to be sending an ambulance or someone to help transport her out. And nobody has shown up for her yet. She called 911, and 911 said they weren't sending anybody else out."

Overnight, evacuation centers and shelters were still being outfitted with beds and blankets. Gov. Jerry Brown issued an emergency order last night to help with the process, which saw shelters erected at fairgrounds to handle the thousands of people leaving Oroville and other downstream areas.

While the waters are receding and dry weather is expected for Monday and Tuesday, the region in Northern California could get another round of rain later this week, when forecasts are calling for several days of rain.

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The Oroville Dam incident has sparked questions about how to repair the dam's spillways — and whether other structures in California and beyond are similarly vulnerable. After the main spillway developed a 200-foot hole, the auxiliary spillway also began to erode, sparking Sunday's evacuation.

Flood control expert Jeffrey Mount, of the Public Policy Institute of California and the University of California Davis, says the auxiliary spillway at Oroville had never been tested — always a challenge with emergency equipment — and that it will be very expensive to repair.

"The weaknesses were revealed immediately in the design, and it threatened to collapse," Mount tells Morning Edition.

"I can tell you that this event will cause us to do some soul-searching about the amount of money we're spending on infrastructure — maintenance, particularly — here in California," Mount says.