Officials were warned twelve years in advance about potential safety hazards at the Oroville Dam in Butte County, California, which now faces the risk of flooding nearby residential areas as a result of a broken spillway and increased rainfall.
Local outlet Mercury News reports:
“Three environmental groups — the Friends of the River, the Sierra Club and the South Yuba Citizens League — filed a motion with the federal government on Oct. 17, 2005, as part of Oroville Dam’s relicensing process, urging federal officials to require that the dam’s emergency spillway be armored with concrete, rather than remain as an earthen hillside.”
"That never happened. The aging Oroville dam, which exceeded capacity on Sunday, began to overflow and spill over the earthen emergency spillway after the main spillway was severely damaged. These developments prompted flood warnings and a declaration of a state of emergency from Governor Jerry Brown. The spillway is on the verge of collapse, a potential disaster that prompted mass evacuations. Over 188,000 residents have been displaced." . . .
"When authorities were forced to use Oroville Dam’s emergency spillway, as recent storms caused the adjacent reservoir to swell, they expected to let water flow for at least 32 hours, 58 at the most.
"But after just less than a day, the emergency spillway in California’s gold country was at risk of failing. A craterlike hole had surfaced Sunday. Officials feared the worst: That further erosion would cause the spillway to collapse, clearing the way for a 30-foot-wall of water from the overfull reservoir to engulf surrounding areas." . . .