Route 101 Widening And Flood Control

The Marin-Sonoma Narrow Project was commissioned by the California Department of Transportation to widen 16 miles of highway from State Route 37 in Marin County to Corona Road in Petaluma. Ghilotti Bros. realigned and widened Highway 101 from two lanes to three lanes in each direction with the intent to alleviate traffic congestion and enhance traffic safety by improving sight distances.

The project was comprised of five stages and sub-stages. There was over 620,000 CY of total excavated and demolished material. Heavy cut/fill earthwork with scrapers was required for the new highway alignment and profile. Extensive existing facilities were removed, including 11,000+ LF of storm drain. The scope also included substantial temporary facilities for drainage, stormwater pollution protection, and roadway surfacing for traffic detours.

The structures work included the demolition of the existing San Antonio Creek bridge, the stabilization of the ground for the new bridge abutments/approach, the placement of surcharges for the new abutments, the construction of a 500-foot long concrete bridge (cast-in-place girders, cast-in-drilled hole piling/driven concrete piling), and the construction of 1,600+ LF of concrete retaining walls.

The construction of the new highway, frontage road, and bike path required the installation of 32,000+ LF of drainage systems, 130,000+ CYs of base material (permeable base, AS4, AB2, LCB), and 100,000+ tons of HMA (dense/open grade). The project also required the installation of all new electrical facilities for traffic operations, sign structures, highway safety facilities, and final erosion control.

Ghilotti Bros. won the 2021 IPI Partnered Project of the Year Award for the partnering services they performed on this project.

Earthwork Means and Methods: Primarily used 623 scrapers and D-8 dozers to move dirt. The team also utilizes excavators and trucks for some components.

Contract Value: $45,745,515


California Department of Transportation


San Antonio Creek


Public Works


Earthwork, Paving & Concrete