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.  The project is scheduled for completion in late December 2023. 


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 remaining widening projects in Marin County will begin is spring 2022. 
In addition to the widening, three soundwalls have been constructed to reduce traffic noise to the surrounding community.   
A new overpass is being constructed to accommodate the City of Petaluma's future project to build a new road, Rainier Boulevard.