A total failure of Oroville dam would prove catastrophic. The loss of life, likely tremendous. Repair costs unknown.
While much of the focus in Oroville has shifted to restarting the hydro-electric Hyatt Power Plant, the extent of the tragedy narrowly averted last month is coming into better focus.
Responding to a California Public Records Act request filed by NSPR, state officials released a 2006 map revised in June showing the extent of flooding if Oroville dam failed when full.
Flooding would cover parts of eight counties and submerge an area from several miles west of Chico in Butte County south nearly to Rio Vista in Solano County. With the exception of the Sutter Buttes, areas inundated would reach across the Sacramento Valley, leaving Interstate 5 underwater between Willows and Maxwell. Long stretches of state Highways 20, 45, 70, 99, 113 and 162 along with Interstate 80 would be flooded.
Entire cities — some far from Oroville — would be partly submerged. Floodwaters would lap the outskirts of Willows, Williams and Woodland, while flooding West Sacramento, Yuba City, Colusa and Knights Landing.
In Oroville itself, a disaster appears unsurvivable. Officials estimate that a dam failure would leave downtown Oroville under 87 feet of water. Peak floodwaters would leave Marysville beneath 26 feet of water and West Sacramento about 14. Officials anticipate people downstream would have more time to react. According to the simulation, residents of Biggs and Gridley would have about four hours before water started rising, Marysville and Yuba City about ten.
Repair and reconstruction costs would likely be staggering. Outside the flood zone Californians could face lengthy water shortages and disruption depending on damage to the levees and canals that help deliver water further south. The state would also have to survive for an undetermined period while the dam, which creates the state’s second largest reservoir, is rebuilt.