The flood risk in the Sacramento metropolitan area is greatly improved now that a 12-year project to build a back-up spillway at Folsom Lake is complete.
Managers say the structure reduces the annual risk to a 1-in-200 chance, more than double the previous protection level.
The nearly $1 billion spillway was an unprecedented joint effort involving the U.S. Army Corps of Engineers and the U.S. Bureau of Reclamation.
Reclamation's Drew Lessard says it will help water managers control the lake level during heavy storms because it can kick into action sooner than the release outlets at the dam.
"So the new spillway, the gates ae actually 50 feet lower, which is where the water will be," Lessard says. "It allows us to match the downstream levee capacity instantaneously."
Despite it being an auxiliary spillway, the new structure will likely be used regularly during wet years.
It's one of the largest infrastructure projects in the West in recent years.