Thirty-Day Closure of State Route 12/121 in Schellville, Sonoma County, to Replace Railings on Arroyo Seco Bridge

Closure from Wednesday, October 1 to Friday, October 31

Sonoma County - Caltrans will fully close State Route 12/121 for thirty days in October in the Sonoma County community of Schellville to allow workers to replace bridge railings on the Arroyo Seco Bridge, a two-lane, shoulder-less bridge spanning Schellville Creek just east of Eighth Street.

The full closure will begin at 12:01 AM Wednesday, October 1 until 5:00 AM, Friday, October 31, 2025.

This section of state highway is a concurrent route, where State Route 12 and 121 share the same road, and where route numbers can be used interchangeably.

Westbound traffic will be detoured onto Napa Road to Eighth Street, then back to Route 12/121. Eastbound traffic would follow this detour route in reverse.

The Arroyo Seco Bridge was built in 1923. The bridge railings, which serve as guardrails to keep vehicles from veering off the bridge, are as old as the bridge and must be replaced to meet current safety standards.

After several meetings with first responders and considering the result of a traffic study comparing a full closure to one-way traffic control, Caltrans opted for a full closure.

The full closure provides more working room for workers and would require a 30-day closure, whereas the one-way traffic control alternative would necessitate an 80-day partial closure due to the lack of working room. First responders were unanimous in their preference for the closure with the shorter duration.

October was chosen as the best month for the project due to environmental requirements and weather concerns.

The replacement of bridge railing on the Arroyo Seco Bridge is half of a two-bridge project. Caltrans has tentatively scheduled bridge railing replacement on the nearby Yellow Creek Bridge on Route 121 in late 2025 or early 2026

For more information and update go to the project webpage: 121 Arroyo Seco and Yellow Creek Bridge Rail Replacement | Caltrans

For 24/7 traffic updates, please visit 511.org: https://x.com/511SFBay For real-time information, visit Caltrans QuickMap: https://quickmap.dot.ca.gov Follow us on X: https://x.com/CaltransD4 Or call 1-800-472-7623, 1-800-427-ROAD for state highway conditions statewide.