Oroville Dam scare prompts evacuation of 180,000 people
February 13, 2017
Oroville Dam emergency floodway (left) and main floodway (right). Photo: Gonzalo (Peewee) Curiel
More than 180,000 Northern California residents received evacuation orders Sunday over fears that the emergency spillway at the Oroville Dam will fail and possibly cause massive flooding. [Oroville MR]
The Oroville Dam, which is 770 feet high, is the tallest dam in the United States. On the north side of the dam lies the emergency spillway structure, which is a concrete lip on a hill above a diversion pool.
A hole developed in the emergency spillway, and water cascaded down a dirt ravine, according to the State Department of Water Resources. Erosion appears to be spreading up toward the emergency spillway structure.
If the enlarging chasm undercuts the structure, the emergency spillway could fail resulting in the water behind the barrier coming down the hill uncontrollably into the diversion pool and down the Feather River. That would set the stage for the possibility of massive flooding into Oroville and communities farther south.
The main spillway, which lies to the side of the emergency spillway, is damaged as well. Still, workers increased the water flow through the main spillway to 100,000 cubic feet per second in attempt to more quickly lower the lake level. The lake level dropped one foot over a three-hour span Sunday evening, and water stopped flowing over the emergency spillway.
Evacuation orders affected Oroville and communities south of the city. Oroville is a city of about 16,000 people and the seat of Butte County.
Authorities evacuated the Butte County Jail and Juvenile Hall. On Monday, most Butte County schools are closed, as is Butte College.
Officials instructed residents to evacuate north to Chico, where hundreds of evacuees were welcomed at the Silver Dollar Fairgrounds. The Chico Elks Lodge, Neighborhood Church and other organizations also opened up to evacuees.
The evacuations caused gridlock on highways out of Oroville, Marysville and Yuba City. Several highways were eventually closed, and there were long lines at gas stations.
Authorities have not lifted evacuation orders, as of Monday morning.
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