OROVILLE DAM CALAMITY WAS PREVENTABLE

Oroville Dam in northern California has come perilously close to at least a partial breach as the lake rapidly filled with water from its watershed inputs as a result of recent heavy warm rains on top of a huge snow pack.  Over 188,000 people were evacuated from the city of Oroville and points downstream Sunday afternoon as holes in the two spillways from the dam threatened to eat back toward the face of the dam structure.  

The earthen dam was completed in 1968 to contain waters from the frequently flooded Feather River and to generate electricity; at 700 feet, it is the tallest dam of its kind in the United States.  Both a primary and an emergency spillway were included in the dam construction.  The flow from primary spillway can be controlled, while the flow from the higher emergency spillway cannot; when the water reaches a certain depth, it automatically starts to flow over the concrete lip of the spillway.  The primary spillway was lined with concrete while the emergency spillway was not.  

The dam itself must meet regular inspections for safety.  Twelve years ago, three concerned environmental groups, (the Friends of the River, the Sierra Club and the South Yuba Citizens League ), filed a motion with the federal government 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.   The state Department of Water Resources, and the water agencies that would likely have had to pay the bill for the upgrades, said that contrary to fears, such upgrades were unnecessary and the dam was subsequently relicensed by the Federal Energy Regulatory Commission.

With water flowing into the dam at an alarming rate and much faster than what was being released through the electrical generation process, dam officials decided they should release some water through the primary spillway.  It is questionable as to whether that decision was reached soon enough.  Moreover, it readily became apparent that the concrete liner was deficient and damaged as a gaping hole appeared approximately one-third of the way down the spillway.  So, they shut the water release off while saying there was no reason for concern. 

Nevertheless, just a couple of days later and without any repairs or mitigation of the hole, they once again started releasing water, which signifies that they were in bigger troubles than they willing to admit.  The release was not enough to overcome the tremendous amount of water runoff coming into the dam, and the water level rose to the point of going over the emergency spillway.  That water quickly ate a hole of its own in the bare earth, close to the top of the spillway... close enough that the resulting erosion threatened to strip the concrete off the spillway lip and cause a huge rupture which could have released at least a 30 foot wall of water from the dam... and potentially much, much more.  

That's when the evacuations started. 

As for the dam officials, when questioned about the decision not to line the emergency spillway 12 years ago... well, you know the answer: "Don't blame us, we weren't here in those days and we're much too busy handling the current situation to stop and talk about it."