Construction is in high-gear on the Marin-Sonoma Narrows project at the Marin-Sonoma county line. Motorists can see construction progressing on the future roadway alignment and the new bridge over San Antonio Creek. Southbound traffic will soon be shifted to the west and onto the new bridge that was completed in December. View a video of the concrete pour on November 29, 2017.

Southbound motorists are expected to be shifted to the new alignment in April 2018. After southbound traffic is moved onto the new alignment, crews will begin building the new northbound roadway right over the old southbound lanes.  Northbound traffic will be shifted to the new alignment in the fall and construction of the project is expected to be complete in winter 2018/2019.

The project spans approximately three miles at the Marin-Sonoma County line and over San Antonio Creek. The roadway is being widened to three lanes for the future carpool lane and is being realigned approximately 50 feet to the west, and out of the floodplain. The project also eliminates driveways and at-grade crossings, improves sightlines to for safety, and build a bicycle facility across San Antonio Creek to connect San Antonio Road with the Petaluma Boulevard South frontage road.

The current phase of construction is being designed and managed by TAM in coordination with Caltrans and the Sonoma County Transportation Authority (SCTA).

This page last edited: 2018-03-23