Board of Supervisors authorizes engineering services for seismic retrofit of Monte Rio bridge over Russian River

The Board of Supervisors today approved $1.8 million for engineering and environmental work in preparation of a seismic retrofit of the Bohemian Highway Bridge that spans the Russian River in Monte Rio. The bridge has been identified by Caltrans as structurally vulnerable to failure during a major earthquake. The state initially planned to replace the bridge until the Caltrans Office of Earthquake Engineering reassessed the project in 2023 and recommended a reduced-scope strategy focused solely on seismic vulnerability rather than full bridge replacement. 

“This bridge is a critical connection for West County, and I’m glad the seismic upgrade project is finally moving forward after eight years of planning and changes from the state,” said Supervisor Lynda Hopkins, chair of the Board of Supervisors. “While we were hoping for a replacement, this project will extend the life of the bridge and address key safety concerns.” 

In 2012, Caltrans identified multiple concerns with the bridge, including potential seismic vulnerability, degrading foundations, and inadequate bicycle and pedestrian access. An analysis at the time showed a replacement bridge would cost less than retrofitting the span, which was built in 1934. While discussions of the need for a retrofit have occurred for roughly 20 years, replacement efforts began in 2015, following community engagement by the County and securing of grant funding from state and federal agencies. After the County completed community engagement and finalized the Environmental Impact Report for the bridge replacement, project costs and designs changed and increased over the 10-year process, from approximately $25 million to $88 million, resulting in Caltrans re-evaluating the project. 

The Bohemian Highway Bridge seismic upgrade project is eligible for reimbursement through the Federal Highway Bridge Program, with the County match portion being funded by the state through the Local Bridge Seismic Retrofit Account. Of 925 engineering firms invited to respond to the project announcement, two proposals were received, with Fresno-based Cornerstone Structural Engineering Group, Inc. chosen for the project. 

Summary Report and Professional Services Agreement. 

For more information on the Bohemian Highway Bridge seismic retrofit project, please contact the Sonoma County Department of Public Infrastructure at (707) 565-2550 or email SPI@sonoma-county.org.  

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Media Contact: 
Dan Virkstis, communications specialist 
publicaffairs@sonoma-county.org 
707-565-3040