On December 23, 1964, the State Route 49 bridge over the North Fork American River just below Auburn was washed away. Hell Hole Dam, being built for Placer County Water Agency (PCWA) on the Rubicon River, failed during an extreme precipitation event now recognized as an atmospheric river. The failure of the partially built dam sent a wave of water and debris downstream into the Middle Fork American, where it eventually reached the Confluence and destroyed the bridge.
Just nine months later the Auburn Dam Project was passed by Congress and signed into law by President Johnson on September 2, 1965. The metal and concrete bridge debris deposited in the river channel and along its banks was left where it was because it was assumed the Auburn Reservoir would soon cover it under hundreds of feet of water.
Now 56 years later, Auburn Dam has not been built and no plans are being pursued to resume its construction. PARC believes the public safety hazard created by the metal debris in the river needs to be eliminated. PARC is now advancing a removal plan with the California Department of Transportation (Caltrans), which decided in 1965 to leave the bridge debris in the river. This was a reasonable decision at the time, but now it is time to remove the hazard to those who swim and boat this river segment in the heavily used Confluence area of the Auburn State Recreation Area.
PARC retained Advanced Marine Services to perform an underwater survey of the debris field. The survey was completed in October 2020. A video summary of the underwater survey is available. A short 4-minute video tells the story about the bridge being washed out and an introduction to the survey work. The short video is the beginning of a 30-minute summary of the underwater survey work.
Both videos are available on the PARC YouTube channel. You can also view the videos below.
PARC’s goal is to have all the metal and concrete debris removed as a single project. Our goal is having it removed in October 2022 when natural river flows are lowest and PCWA shuts down the Middle Fork Project for annual maintenance.
Advanced Marine Services
North Fork American River
State Route 49 Bridge Debris Assessment
CBS 13 News coverage of State Route 49 Bridge Debris Removal Project
Letters of Support for Bridge Debris Removal Project
City of Auburn
Placer County Board of Supervisors
El Dorado County Board of Supervisors
Placer County Water Agency
Auburn Recreation District
United Auburn Indian Community
Auburn State Recreation Area Canyon Keepers
Sierra Nevada Conservancy
Auburn Journal article
February 18, 2021:
The failure of the partially constructed Hell Hole Dam on December 23, 1964, caused by an atmospheric river, sent a wall of water downstream to the area now known as the Confluence of the American River below Auburn.
Water soon crested and destroyed the Georgetown Bridge (State Route 49) which was built in 1948. (Left & center photos courtesy of California Dept. of Transportation)
750 tons of steel and concrete were sent into the river. (Auburn Journal Photo)
PARC North Fork American River Bridge Debris Survey (Long Version 30 Minutes)