MONTEBELLO, Calif. (AP) The Army Corps of Engineers has raised its estimation of flood risk from the Whittier Narrows Dam in eastern Los Angeles County.

The Corps said the risk characterization has been changed from high urgency to very high urgency.

The earthen dam constrains the San Gabriel River and the Rio Hondo. Both are normally dry but fill during storms.

Analysis found that during an unlikely but possible storm, water released through the spillway could exceed downstream channel capacity, flooding adjacent land.

Other failure modes involve erosion from water piping through the dam's foundation and from water overtopping the dam.

The Corps said interim measures will begin before next winter's rains and other measures are likely by the end of 2017. Construction of final modifications is expected to begin in 2020.

Today's top stories

SEPTA Builds Major Transportation Center

National Equipment League — Heavy Equipment Operation as a Professional Sport — Launches Season Two

Washington Bridge in Providence, R.I., Undergoes Demolition

Construction Industry Optimistically Preparing for New Year Ahead

Capital Express Central Project Ramps Up in Texas

Nevada DOT Awards $54M Contract for U.S. 50 Renovation in Ely

Construction Set for $37M Wildlife Crossing in Wyoming

PCL Construction's Special Projects Division Sets 2024 Record With Nearly 270 New Projects