Lucas Valley Road Project Receives Regional Award

Posted on June 23, 2022

For Immediate Release –

San Rafael, CA –

Softening of curve acknowledged by the American Public Works Association


An aerial view of completed Lucas Valley Road curve realignment project, with a car driving along the roadway.. - photo credit Gibson Outdoor Photography
One section of Lucas Valley Road (at milepost 5.08) now has a larger and less severe curve radius, helping improving public safety along the roadway. The project won an American Public Works Association award. (Photo by Gibson Outdoor Photography)

The completed Lucas Valley Road curve realignment project, which softened a sharp turn along the popular east-west connection from the highly populated Highway 101 corridor to the more rural West Marin, has received an award from the American Public Works Association (APWA).

The project was acknowledged for “Transportation Project of the Year under $5 Million” for APWA’s Northern California region, winning out over entries from Alameda, Contra Costa, Del Norte, Humboldt, Lake, Mendocino, Napa, San Francisco, Solano, and Sonoma counties. The Lucas Valley Road project was greenlit for $1.6 million and was completed on budget, funded by a $1.2 million Federal Highway Safety Improvement Program (HSIP) grant and the County’s Road and Bridge Rehabilitation Fund.

The work was overseen by the Marin County Department of Public Works (DPW) and provided a substantial public safety improvement by significantly softening the sharp turn at milepost 5.08 on Lucas Valley Road. The tight turn had been the site of several vehicle accidents, hazardous material spills requiring cleanup projects, and repeated incidences of unexpected road closures caused by oversized vehicles getting stuck.

The construction phase of the project began in June 2021 and was substantially completed and fully open to the public in November 2021. Removal of temporary guardrail components and the final guardrail installation was completed in March 2022, due to a delay in sourcing the materials, but no traffic impacts were associated with that remaining work.

To soften the sharp turn, a 135-foot-long retaining wall was installed on the downhill side of the turn. The wall allowed the road to be shifted east, resulting in a larger and less severe curve radius. The project also included modifications to storm drain infrastructure and the installation of a safety barrier and guardrail.

Two aspects of the project made it stand out among competition for the APWA award. First, the location of the work site was an unforgivingly cramped curve in the road with a hill to one side and a steep, downward slope on the other side. The unique geography and confined workspace made it challenging to deploy and maneuver equipment, supplies and crews, requiring special planning and skills to complete the complex project.

Second, there was a large, concrete drainage pipe (“culvert”) under the road that had deteriorated over the years. Instead of digging it out and fully replacing it, which would have required shutting down the roadway for at least several days for a more intensive and expensive effort, the project team chose to do a “spincasting” method for the culvert. The process entails fabricating a new pipe within the old pipe using partially recycled materials. By essentially rebuilding the large drainage pipe in place, the project team minimized impact to the surrounding area and avoided extensive use of new materials and trucking activities associated with a standard extraction and replacement process.

The construction work was accommodated with alternating single lane access, keeping wait times to under 7.5 minutes using temporary traffic light installations. The project team organized the work so that there were only two road closure days required during the entire endeavor.

It should be noted that there were several occasions during construction when “big-rig” trucks ignored the size restriction signs for the roadway, resulting in the large vehicles getting stuck and forcing the road to close for up to an hour each time. While the improvement project made the curve more navigable for larger vehicles and on par with other curves along Lucas Valley Road, the access restriction against trucks longer than 36 feet, such as big rigs, will remain in place. Signage stating the restriction is at key locations along the roadway.

Improving roadway conditions across unincorporated areas of Marin is an ongoing commitment of the County and is one of the top priorities for the Board of Supervisors. Information on DPW’s projects that are currently underway can be found online.


Berenice Davidson
Assistant Director
Public Works

3501 Civic Center Drive.
San Rafael, CA 94903

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