Sonoma County Bi-Monthly Caltrans Update
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Welcome to the October 2025 edition of the Caltrans Sonoma County Newsletter, where we discuss upcoming and ongoing Caltrans projects in Sonoma County. We aim to keep you informed!
Hwy 101 Marin-Sonoma Narrows Project Completed
Uninterrupted Carpool Lanes Extend 52 Miles
On October 3, Caltrans and its partners from Sonoma and Marin counties hosted a ribbon cutting ceremony to celebrate the conclusion of the US Highway 101 Marin Sonoma Narrows (MSN) Project.
The project was conceived in the early 2000s to reduce congestion and increase passenger throughput on the primary north-south corridor in Marin and Sonoma counties. But there wasn’t enough money to build the entire project at once, so the project was broken down into a dozen smaller projects that were completed over the last 15 years. Now Hwy 101 between Novato and northern Petaluma boasts a new carpool lane in each direction.
Read more at: The Marin-Sonoma Narrows Project | Caltrans
Route 116/121 Roundabout Project Completed in Schellville
On October 24, dignitaries gathered to celebrate the completion of the Route 116/121 Roundabout project in Schellville, which replaced four-way stop with a two-lane roundabout that will reduce congestion, improve traffic operations and lower the frequency and severity of collisions.
Indeed, the roundabout was already receiving kudos from motorists when it opened in its unfinished form last January, with drivers noticing improved traffic flow and fewer backups.
In addition to benefiting motorists, the roundabout also features new sidewalks and bicycle lanes for pedestrians and cyclists. For more information go to: 116-121 Intersection | Caltrans
Replacement of Bridge Railings on Route 116 and 121 in Schellville
Arroyo Seco Bridge
During the evening of Monday, October 27, 2025, Caltrans reopened Route 12/121 after a 27-day full closed that allowed work crews to replace the railing on the Arroyo Seco Bridge over Schellville Creek.
The railings had its original railing from the time of the bridge’s completion in 1923. The railing required replacement due to a century of weathering and simple obsolesce.
During the closure, traffic was detoured onto Napa Road to E. 8th Street and vice versa depending on direction of travel.
With the completion of the Arroyo Seco Bride railing replacement, Caltrans will begin work on the Yellow Creek railings. To learn more about this project, visit the webpage:
121 Arroyo Seco and Yellow Creek Bridge Rail Replacement | Caltrans
Yellow Creek Bridge
Less than a few miles from the Arroyo Seco Bridge, and closer still to the 116/121 Roundabout Project (see above) is the Yellow Creek Bridge Railing Replacement Project.
Like the Arroyo Seco Bridge the Yellow Creek Bridge was built in the early1920s and maintain its original railings.
Unlike the Arroyo Creek Bridge project, this project will not require a full closure of the roadway, rather traffic will be under one-way traffic control.
Allowing traffic to traverse the bridge during the project with add time to the schedule. As such, one-way traffic control will be in place for four months between November 3, and February 28.
While closing one lane of traffic for several months will inevitably cause traffic delays, replacing the bridge railings is necessary for the safety of motorists who traverse the the bridge.
Caltrans met with local leaders, and first responders when considering the best time to embarks on both projects, which was after summer but before winter rains.
To learn more about this project, visit the webpage:
121 Arroyo Seco and Yellow Creek Bridge Rail Replacement | Caltrans
Setting the PACE: Public Affairs Customer Engagement Site is Now Live!
District 4 is proud to announce the launch of our new Customer Service Request (CSR) platform. PACE, the Public Affairs Customer Engagement site, provides a regularly updated breakdown of services requested and rendered across the district.
- The CSR dashboard aims to provide an overview of the responsiveness to maintenance services requested across the nine Bay Area counties.
- The data represented as month-to-date falls within a rolling 30-day Service Level Agreement (SLA) and is updated weekly.
- We strive to close 60% (or more) of all monthly service requests received via the CSR website portal.
- For more information or to leave comments/suggestions, please contact D4CSLTEAM@dot.ca.gov.
- To report a highway issue/problem, please submit a CSR ticket through the Customer Service Request Form.
The Sonoma County newsletter will be distributed on a regular schedule.
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.
CONTACT:
Sonoma County Public Information Officers
Jeff Weiss
General Information
(510) 286-4444
Acting North Bay Branch Chief
Alejandro Lopez
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