Wohler Road Bridge to undergo history-making $18 million seismic retrofit

Seismic upgrades coming to a landmark one-lane Russian River bridge is expected to be the most expensive bridge retrofit in Sonoma County history and disrupt traffic in the area through 2025.

Construction on the historic Wohler Road Bridge, which crosses the Russian River 10 miles northwest of Santa Rosa, is slated to begin this summer. However, work could start as early as April depending on the water level of the river, according to Janice Thompson, Sonoma Public Infrastructure’s deputy director of engineering and maintenance.

The 102-year-old span will receive new reinforcements to its steel truss and foundation along with other retrofitting that will help the bridge meet current seismic design standards.

Earlier this month, the Sonoma County Board of Supervisors awarded an $18 million contract to Ghilotti Construction Co. Inc. for the work.

“It is our biggest (bridge) job financially that we’ve taken on in our history,” Thompson said.

Previously, the most expensive bridge retrofit project was in the $10 million range, according to Thompson.

The project will be funded by the Federal Highway Bridge Program, following project approval by Caltrans in 2023, according to a Feb. 6 news release.

Construction on the bridge is expected to last through 2025.

Thompson said that intermittent traffic disruptions will occur during the first year of construction, with more substantial road closures expected in 2025. The county will give advance notice of those closures once construction begins, Thompson said.

In the release, officials said the project included extensive community engagement during its design phase, and will preserve the architectural appeal of the bridge.

"Countless stakeholders need to be recognized for getting this project to the construction phase — from the Wohler Bridge Neighborhood Association to the utility companies and partner agencies at the state level, to our dedicated team of engineers and officials at the Department of Public Infrastructure,” said 5th District Supervisor Lynda Hopkins in the release. “I applaud and thank you and look forward to the grand reopening of this iconic Sonoma County landmark.”