Flood of missteps in Oroville Dam crisis
size of a football field in the concrete chute. But now suddenly they realized that the dam’s emergency backup spillway – essentially an unpaved hillside – was falling apart, too, and could unleash a deadly torrent of water.
Honea reacted by ordering the immediate evacuation of nearly 200,000 people downstream.
In the end, after frantic action by the dam’s keepers, catastrophe was averted. But an Associated Press examination of state and federal documents, emails obtained under public records requests and numerous interviews reveal a sequence of questionable decisions and missteps, some of them made years ago, some of them in the middle of the crisis.
Among other things, the dam’s federal and state overseers overestimated the durability of the two spillways. And in public statements during the emergency, they failed to acknowledge – or perhaps recognize – that while they were busy dealing with one crisis, they were creating a possi-
the Army Corps of Engineers to bypass a rule that required it to release huge amounts of water from the rapidly filling lake behind the dam.
Operators vary water flows down the damaged chute to gauge its stability, at times stopping it completely. It’s a tricky calculation, as the lake rises toward the highest level on record. The flows are increased at times to minimize rising lake levels, according to agency emails.
Water managers announce an emergency spillway might be used within days – for the first time in the dam’s 50-year history – as lake waters continue to rise. “There is no imminent threat to the public,” they say. Alternating increases and decreases in water flows continue. If water begins flowing over the emergency spillway – essentially an unpaved hillside – operators cannot
In an email, the state tells local sheriffs that engineers from several organizations are working to determine the maximum amount of water that can be safely released down the eroding spillway. Operators announce it is less likely the emergency spillway will be needed, after they boost water releases from the lake. However, they later cut releases to prevent erosion near power-line towers. In an email to Butte County Sheriff Kory Honea, the state water agency says hydrology reports show the flow of water, even reduced, will keep the lake from spilling over the emergency spillway. In a public statement, dam managers say there is “no imminent threat to the public or the dam.”
The state announces water begins spilling into the emergency spillway at 8 a.m., after the lake reaches its highest level on record. State officials later say the second spill-
way is “operating as intended.” The state water agency’s acting director, William Croyle, says in a statement that the flow of water down the emergency spillway is well below what it was designed to handle, and “based on our current situation, there is no threat.” In an email to the state that evening, the city administrator of Biggs, about 25 miles downstream from the dam, complains that he has received scant information about the dam. The state agency “has earned a grade of ‘F’ on its ability to timely and completely communicate during this incident,” Administrator Mark Sorensen writes.
An 8 a.m. update from the state gives no sign of trouble. It says flow over the emergency spillway is decreasing, and erosion on the unpaved hillside has been “minimal.” Later that afternoon, Honea, the sheriff, learns the emergency spillway is breaking apart. He orders the immediate evacuation of nearly 200,000 people. The state estimates the second spillway could fail within 60 minutes.