News Release Manager

Army Corps Reclassifies Whittier Narrows Dam Risk Characterization

Published June 6, 2016


LOS ANGELES – The U.S. Army Corps of Engineers has changed Whittier Narrows Dam’s risk characterization from high urgency to very high urgency. The anticipated performance of the San Gabriel River spillway gates drove this recent change based upon an ongoing dam safety analysis effort. During a rare flood, water could be released through the spillway and exceed the downstream channel capacity, overtopping the levees and flooding adjacent land.

"While the dam is typically dry, an intensive review of the dam, its spillway and outlet structures, and the potential for adverse impacts to the downstream population indicates we have some work to do," said Col. Kirk Gibbs, commander of the U.S. Army Corps of Engineers Los Angeles District. "Our message right now is that during major floods, the risk along the San Gabriel and Rio Hondo rivers is unacceptable and that we will do everything possible to reduce that risk expeditiously."

"I want to emphasize," Gibbs continued, "that this is a storm that is very unlikely to occur, but it is nonetheless a real possibility and one that we must be prepared for."

The analysis also determined two other potential failure modes for Whittier Narrows Dam: erosion resulting from water piping through the foundation of the earthen dam and erosion resulting from water overtopping the dam.

The Los Angeles District is currently working with a nationwide team of experts to develop a plan to reduce the risks associated with the spillway, foundation, and overtopping. The Corps anticipates that some interim measures will be in operation prior to this year’s winter rains; other measures will likely be installed before the end of 2017. Construction of final modifications is anticipated to begin in 2020.

"We're working closely with local governments and emergency responders downstream to establish and refine procedures in the event of an emergency," Gibbs said. "Our primary concern is to protect the lives and property of those who rely on our flood damage reduction projects."


Greg Fuderer
213-479-8698 (cell)

Release no. 16-015