The Oroville Dam is an earth fill embankment dam on the Feather River east of Oroville, California and is known to be the tallest dam in the United States at 770 feet high. This dam was built between 1962 and 1968 and consist of more than 85 million cubic yards of earth. The dam serves mainly for water supply and flood control. The dam impounds Lake Oroville, the second largest man-made lake in the State of California.

On February 7, 2017 during ongoing flood control release due to heavy rains and snowmelt a hole appeared in the Oroville dam primary spillway. Due to continual high inflows to the lake, the dam operators had no other choice but to continue to use the damaged spillway. As water levels continued to rise attempts went underway to try and continue to use the never before used emergency spillway. Crews began working to cut trees and move vegetation within the emergency spillway which flowed down the hill side.

The initial cave-in of the spillway occurred on February 8, 2017 when chunks of concrete went flying from the water flowing down the nearly mile long spillway creating a 200 foot long, 30 foot deep hole. The hole has continued to grow. The water tumbles down the hill at up to 50 miles per hour and explodes into the air as it hits the fracture that has opened up in the spillway.

The engineers hoped that the use of the damaged spillway would drain the lake enough to allow the emergency spillway to not be used it didn’t last. On February 11, 2017 Lake Oroville hit the overflow mark on the emergency spillway, which until then had never been used since the dam’s construction in 1968.

Due to the damage to the main spillway it will need to be completely replaced, which officials hope to have done by the next wet season.