121 Arroyo Seco and Yellow Creek Bridge Rail Replacement

Closures on Arroyo Seco and Yellow Creek Bridges on Highway 121 in Schellville To Replace Bridge Railings 

 

Update:  November 3, 2025 

One-way Traffic Control begins on State Route 121 in Sonoma County to Replace Bridge Railings on the Yellow Creek Bridge

Caltrans will implement one-way traffic control on State Route 121 in the Schellville community of Sonoma County to replace bridge railings on the Yellow Creek Bridge, located several hundred feet south of the newly opened Route 116/121 Roundabout at Big Bend.

The closure begins just after midnight (12:01 AM) Monday, November 3, 2025, and last until 5:00 AM Saturday, February 28, 2026. During this period, the two-lane roadway will be reduced to one lane as northbound and southbound alternate passage through the work zone.

The project schedule is based on typical rainy season conditions in Sonoma County. The contractor will work under a permit that protects the creek from sedimentation and other construction impacts.

The Yellow Creek Bridge was built in 1922. The bridge railings are part of the original structure, serving as guardrails to keep vehicles from veering off the bridge. The weather-worn railings must be replaced to meet current safety standards.

A traffic study and multiple meetings with local first responders were conducted to evaluate construction options. The study compared a full closure with a long detour via Routes 101 and 37 to the proposed one-way traffic control. Based on traffic impacts and emergency access considerations, the one-way traffic control was determined to be the safest and least disruptive option.

This work represents the second phase of a two-bridge safety improvement project. Caltrans recently finished replacing the railings on the Arroyo Seco Bridge on SR-121 near 8th Street, reopening the bridge last night, October 27, around 10:00 PM.

Caltrans thanks motorists and the local community for their patience as we continue to improve bridge safety and infrastructure in Sonoma County.

 

Update:  October 27 

Caltrans Reopens Route 121 at the Arroyo Seco Bridge

 

Traffic Advisory -  Caltrans Reopens Route 121 at the Arroyo Seco Bridge

Caltrans reopened State Route 12/121 on October 27, at approximately 10:00 PM, in the Sonoma County community of Schellville, as Caltrans finishes replacing the weather-worn and outdated bridge railings on the Arroyo Seco Bridge spanning Schellville Creek.

Caltrans had scheduled a 30-day closure from October 1 to October 31; however, the construction team reopened the bridge three days early.

The reopening of the highway will be welcome news to motorists who have been detoured around the closure via 8th Street E and Napa Road.

 

 

Caltrans Closes Route 12/121 in Schellville east of Eighth Street for Thirty Days to Replace Bridge Railings on Arroyo Seco Bridge 

 

 

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

 

 

 

News Release regarding tree trimming at Arroyo Seco Bridge in August 2025