The Oroville Dam will pose a "very significant risk" if repairs to its main spillway are not done by the fall rainy season.
That is the conclusion of a report from federal investigators, which was not specific about what the risk was.
200,000 people were evacuated in mid-February when the Oroville Dam's emergency spillway began to erode.
Water was allowed to pour over the emergency spillway for the first time ever after a huge hole opened up in the main spillway.