In 2005, three environmental groups warned state and federal officials about what they believed was a problem with Oroville Dam’s emergency spillway, which was at risk of collapsing over the weekend as recent storms caused the adjacent massive reservoir to swell.
Their concern, which seemed to have fallen on deaf ears: The emergency spillway, which is meant to be used in urgent situations — is not really a spillway. Rather, it’s a 1,700-foot long concrete weir that empties onto a dirt hillside. That means, in the event of severe flooding, water would erode that hillside and flood nearby communities, the groups said then.
That nearly happened on Sunday, when a hole on the emergency spillway threatened to flood the surrounding area and prompted officials to evacuate thousands of residents who remain displaced as of Monday afternoon.