California's second-largest reservoir is now at total capacity, with the state's largest nearing capacity following this winter's monumental storms.
Last week, a nearly 200-foot long, 30-foot deep hole was created after chunks of concrete came off the main spillway.
Nearly 200,000 people who were ordered to leave their homes out of fear that a spillway could collapse may not be able to return until the barrier at the nation's tallest dam is repaired, a sheriff said Monday.
The department said that "failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville."