Highway 101 Widening in Petaluma

Caltrans is widening Highway 101 in Petaluma between Lakeville Highway (Route 116) and Corona Road by adding a carpool lane in each direction. Upon completion, Highway 101 will be three lanes in each direction, including the new northbound and southbound carpool lanes. Ghilotti Construction is the contractor on the $78 million project.


Proposed and Existing 101 Images

The project is part of the larger Marin-Sonoma Narrows project, a series of 13 projects to widen Highway 101 by adding a carpool lane in each direction. The Marin-Sonoma Narrows project extends 16-miles from State Route 37 in Marin County to Corona Road in Santa Rosa. 

The Petaluma project, known as C2, is the final project in Sonoma County and will be the eleventh project to be completed. The two remaining projects in Marin County will begin when funding becomes available.

In addition to the widening, soundwalls will be added in many locations. A new overpass is being constructed at Rainier Avenue, which will elevate the highway over the SMART railroad tracks. 


Caltrans Closes Bike/Ped Path in Petaluma

101 Petaluma Sonoma Narrows Map



May, 29, 2020 - Caltrans Begins Demolition of the Petaluma Overpass

As part of the project to widen Highway 101 through Petaluma, Caltrans closed the left southbound lane on Highway 101 at the Petaluma Overcrossing from 9:00 PM – 6:00 AM, Friday – Saturday, May 29-30, 2020, to demolish the left edge of the bridge. The Petaluma Overcrossing travels above the SMART railroad tracks between E. Washington Street and Petaluma North Boulevard.

The Petaluma Overcrossing will be demolished and rebuilt in stages until the new bridge is completed towards the end of 2020. Demolishing the leftmost part of the bridge will provide Caltrans room to build part of the new overpass.

Highway 101 Widening in Petaluma Construction Day 1 | Highway 101 Widening in Petaluma Construction Day 2