Evacuations urged in Northern California amid flood fears

A series of powerful storms last week sent runoff rushing into the lake just as a gaping hole developed in the main spillway.

OROVILLE, Calif. — As California water officials rushed Monday to stabilize conditions at the Oroville Dam, the acting director of the state Department of Water Resources brushed aside questions about recommendations made a dozen years ago to upgrade the emergency spillway that nearly failed Sunday.

In a Monday afternoon news conference near Oroville Dam, acting DWR Director Bill Croyle was asked whether the spillway should have been reinforced years ago as advocacy groups insisted in 2005 filings with the federal government.

Croyle said he wasn’t familiar with the reports, but once the crisis subsided, engineers would do a thorough analysis of what went wrong.

“That’s part of our vetting process,” he said.

The recommendations to strengthen the spillway came as state officials were seeking approval from the Federal Energy Regulatory Commission to relicense Oroville Dam for another 50 years.

Advocacy groups including Sacramento-based Friends of the River said at the time that the emergency spillway would actually pose a danger if the reservoir were hit with heavy storm runoff from the Sierra Nevada and filled to the brim.

The groups said the emergency spillway needed to be strengthened to avoid almost precisely the events that occurred this weekend, when the spillway activated and the forested hillside below began eroding dangerously close to the lip of structure.

“As I recall, effectively (the official) response was ‘Well, you know, it doesn’t seem likely we’d ever have to use the emergency spillway,’” Ron Stork, a senior policy advocate at Friends of the River, told The Sacramento Bee.

Stork’s group advocated for the changes along with officials in Yuba and Sutter counties downstream from the dam. At the time, state officials objected to upgrading the spillway, saying it wasn’t necessary.

“Our facilities, including the spillway, are safe during any conceivable flood event,” Raphael Torres, acting deputy director of the State Water Project, said in 2005.

The spillway issue dates to 1970, when the operational manual for the dam was updated with the expectation that Marysville dam would be built on the Yuba River, a tributary of the Feather. This new dam was authorized by Congress in 1966, but never was built.

Nevertheless, Oroville operations were designed to work in concert with the Marysville dam to ensure Feather River flows would not exceed the holding capacity of downstream levees.

Croyle said Monday that second-guessing decisions of his predecessors may come later.

“We’re going to get into recommendations or concerns that were voiced in the past,” he told reporters Monday. “But right now, we’re focused on maintaining public safety — not strictly during this event, but also this spring runoff period.”

More than 100,000 people in communities downstream of Lake Oroville were told to evacuate Sunday evening after authorities grew concerned that dangerous flood waters would start surging out of the huge reservoir.

The flood threat emerged suddenly Sunday afternoon when a hole developed in the auxiliary spillway that was being used for an emergency spill to lower levels of the full-to-the brim reservoir, the second largest in California.

If the erosion advanced quickly uphill, it could undermine the concrete top of the spillway, allowing torrents of water to wash downhill into the Feather River and flood nearby Oroville and other downstream towns.

On Sunday night, officials said the threat had diminished. The erosion had lessened and water stopped spilling over the emergency spillway at about 9 p.m. .

But the situation at the reservoir remained precarious. The two main avenues for getting water out of the lake — the unpaved emergency spillway and the main concrete spillway — were both damaged.

Both spillways are separate from Oroville Dam itself, which state officials continued to say was not in danger. The main spillway, a long concrete chute off to the side of the dam, has a gaping gash in it that forced officials to reduce releases last week.

That caused the lake to quickly rise with heavy storm runoff, triggering emergency releases down the auxiliary spillway, which consists of a concrete weir at the reservoir’s edge that sends flows down a hillside into the Feather River.

Although the emergency spill was small, it started to erode the hillside Sunday afternoon.

“There was significant concern that (the erosion) would compromise the integrity of the spillway, resulting in a substantial release of water,” Butte County Sheriff Kory Honea said at a Sunday evening news briefing.

“We had to make a very critical and difficult decision to initiate the evacuation of the Oroville area,” he added.

“Immediate evacuation from the low levels of Oroville and areas downstream is ordered,” proclaimed a sheriff’s department statement posted on social media. “This is NOT A Drill.”

The order affected rural communities located along the Feather River and included the counties of Butte, Yuba and Sutter. Oroville residents were told to make their way north of the lake to Chico, where an impromptu evacuation shelter had been set up at the fairgrounds.

The Yuba County Office of Emergency Services urged evacuees to travel only to the east, south or west. “DO NOT TRAVEL NORTH TOWARD OROVILLE,” the department said on Twitter.

As traffic slowed to a crawl, travelers reported encountering road blocks heading north on California Highways 70 and 99. For those headed south, the driving was no easier as thousands poured onto the highways in an attempt to evacuate.

By Sunday night, experts were planning to plug the crevice in the emergency spillway with bags of rocks dropped from helicopters.

They had also doubled discharges down the main spillway to help lower the lake level and reduce the overflow.

Lake Oroville is the keystone of the State Water Project that sends Northern California water hundreds of miles south to the southern San Joaquin Valley and Southern California.

In addition to flooding concerns, if operators can’t easily get water out of the lake that could interfere with deliveries to contractors, including the Metropolitan Water District of Southern California.

A series of powerful storms in Northern California sent runoff rushing into the lake just as a gaping hole developed in the main spillway Tuesday, forcing managers to reduce releases.

That pushed the reservoir to overflow Saturday, marking the first time the emergency spillway was used since the dam was finished in 1968. Until Sunday afternoon, it seemed to be going smoothly.