County rolls out new evacuation plan for area south of Oroville Dam
Leading up to the crisis at Oroville Dam, authorities responsible for the safety of communities downstream of California’s second largest reservoir had become complacent, said Butte County Sheriff Kory Honea. The dam had never posed a threat, and “over the course of time, you begin to take it for granted.”
Honea was speaking during a press conference held in Oroville on March 9 where he revealed a new evacuation plan for the area south of Oroville Dam, which is still under an evacuation warning. Such a plan did not exist on Feb. 12, when a catastrophic failure of the dam’s emergency spillway appeared imminent and Honea gave the order to evacuate Oroville—and chaos ensued. As the CN&R previously reported, fleeing residents gridlocked Highway 70 headed north toward Chico, including the section crossing the Feather River, leaving some motorists in the potential flood path.
The California Department of Water Resources had a decades-old emergency plan for the failure of the dam itself, Honea said, but no procedures were in place for the emergency spillway situation.
Cindi Dunsmoor is the only staffer in the county’s Office of Emergency Management. Her role in developing evacuation plans is facilitating collaboration between the county, municipalities, fire officials and law enforcement agencies. None of the stakeholders sounded the alarm prior to Feb. 12, she said.
“I wish I could tell you we were working on it,” she said. “The honest truth is, we had never anticipated an uncontrolled spill over the emergency spillway.”
Honea told the CN&R the same story.
“From all the information I have, from what I’ve been told by DWR, no one contemplated a failure of the emergency spillway,” he said. “When it was built, it was probably considered highly unlikely that we would ever use it. … When it actually started happening, that was an opportunity to learn some incredible lessons.”
Now the county has a plan should another crisis arise in the future, Honea said during the press conference. “Since the evacuation, we have a much, much better understanding of what can go wrong.”
To identify safe evacuation routes, officials used 3-D computer modeling to determine which areas would be inundated with water if the emergency spillway collapsed, said Joe Tapia, a battalion chief for Cal Fire-Butte County. Previously, the only available inundation map showed the broader area that would be affected by a complete failure of Oroville Dam. The new map is more nuanced. It breaks the cities of Oroville, Gridley, Biggs and surrounding unincorporated communities into 11 zones, each with individual evacuation routes, public assembly points and evacuation centers.
To ease traffic congestion, the evacuation would be staggered, with the residents living nearest the dam in Zone 1 leaving first and the other zones following sequentially.
Residents who were left behind during the first evacuation—i.e., homeless people—would be directed to public assembly points, where buses would pick them up and take them to strategically located evacuation centers on both sides of the Feather River.
Ideally, the evacuation would start 12 to 24 hours before water begins flowing over the emergency spillway, Honea said. (On Feb. 12, residents were given about an hour to pack up their belongings and leave town.) To that end, local and state officials have produced a more sophisticated trigger-warning system based on the amount of precipitation forecast in the watershed above Lake Oroville.
“Depending on how much water is flowing in, and how fast the water is rising, that gives us a timeline of when the overflow would go over the spillway,” Tapia said.
The evacuation plan could change during a dynamic emergency situation. “We may have to adjust it depending on what we’re facing,” Honea said. Moreover, all of it depends on residents knowing which zone they’re in and where to go in the event of another crisis (see infobox).
“Have a plan,” Honea said. “If you’re prepared, you’re in a much better position than if you hadn’t thought about these things.”