Graphic showing the auxiliary spillway failure on the Oroville Dam, at 6:08pm on 12 February 2017. The dam itself was not compromised. Graphic: NWS Sacramento

By Anna M. Phillips, Matt Hamilton, Paige St. John, and Chris Megerian
12 February 2017 (Los Angeles Times) – Residents of Oroville and nearby towns were ordered to immediately evacuate on Sunday afternoon after a “hazardous situation” developed involving an emergency spillway at the Oroville Dam. The National Weather Service said the auxiliary spillway at the Oroville Dam was expected to fail by 5:45 p.m., which could send an “uncontrolled release of flood waters from Lake Oroville.” Those in Oroville were asked to flee northward toward Chico. In Yuba County, those in the valley areas were urged to take routes to the east, south, or west. “This is not a drill. This is not a drill. Repeat this is not a drill,” the National Weather Service said. Authorities urged residents to contact neighbors and family members and reach out to the elderly and assist them in evacuating. The Butte County Sheriff’s Department and the state Department of Water Resources said the failure of the auxiliary spillway — a 1,700-foot-long hillside route — was caused by “severe erosion.”  The evacuations marked a dramatic turn of events at the nation’s tallest dam. For several days, officials have been trying to figure out how to get water out of Lake Oroville after the main spillway was damaged. The emergency spillway had never been used before — and until the last few hours it seemed to be working well. Video from television helicopters showed water flowing into a parking lot next to the dam, with large flows going down both the damaged main spillway and the emergency spillway. [more]

Evacuations ordered below Oroville Dam; failure of emergency spillway ‘expected’

OROVILLE, California, 12 February 2017 (Associated Press)  Officials have ordered residents near one of the nation’s biggest dams to evacuate the area, saying a “hazardous situation is developing” after an emergency spillway severely eroded. The emergency spillway of the Oroville Dam in Northern California could fail within an hour unleashing uncontrolled flood waters from Lake Oroville, the California Department of Water Resources said on Sunday afternoon. People in downstream areas need to leave the area immediately, the department said. Residents of Oroville, a town of 16,000 people, should head north toward Chico, and other cities should follow orders from their local law enforcement agencies, the Butte County Sheriff’s office said. Water began flowing over the emergency spillway at dam on Saturday for the first time in its nearly 50-year history after heavy rainfall. Water will continue to flow over an emergency spillway at the nation’s tallest dam for another day or so, officials said earlier Sunday. Water began flowing over the emergency spillway at the Oroville Dam in Northern California on Saturday for the first time in its nearly 50-year history after heavy rainfall. In addition to the emergency spillway, water also flowed through the main spillway that was significantly damaged from erosion. Officials said they’ll assess the damage starting Monday. [more]

Officials order evacuation of residents near California dam

OROVILLE, Butte County, 12 February 2017 (San Francisco Chronicle) – Butte County residents near Lake Oroville, including the entire town of Oroville and nearby regions, were ordered to evacuate Sunday evening after the emergency spillway next to the reservoir’s dam suffered a possible structural failure, officials said. “There has been severe erosion of the emergency spillway and a possible structural breach that could send uncontrolled water down the stream,” said Chris Orrock, a spokesman with the California Department of Water Resources. Residents downstream from Lake Oroville to the Sutter County line were under mandatory evacuation order. Counties around the reservoir, the second largest in the state, down to Sacramento were warned about the possibility of flooding. Department of Water Resources officials issued a statement just before 4:45 p.m. that the “auxiliary spillway at the dam was predicted to fail within the hour.” [more]

Evacuation ordered for Oroville as dam spillway expected to fail