Nicasio Valley Road Bridge Replacement Project

Rosemarie Gaglione, Director, Public Works
Nicasio Valley Road Bridge

Project Description:

The County of Marin has received federal funding to replace local bridges that have been identified as structurally deficient and functionally obsolete. Nicasio Valley Road Bridge over Nicasio Creek is one of the bridges identified for replacement and a project has recently been initiated to conduct environmental studies and to begin design work. Maintaining traffic during construction and protecting the riparian habitat will be high priorities for the project.

A community workshop was held on June 28, 2017 at the Nicasio Elementary School and the following items were presented and discussed:

June 28, 2017, public meeting summary report

Slides from community workshop on June 28, 2017 

Exhibit - Existing and Proposed

Exhibit - Rail options and cross section of roadway

Nicasio Valley Road Bridge is located just south of the intersection of Lucas Valley Road and Nicasio Valley Road in West Marin. Nicasio Valley Road is a two-lane roadway that provides connectivity between Petaluma and San Rafael. The existing bridge was built in 1928 and is a three-span, reinforced concrete T-beam structure. The bridge needs to be replaced for the following reasons:

  • The structure has exceeded its design life and is showing signs of long-term deterioration.
  • The existing narrow bridge deck does not meet current safety standards for two lanes of traffic.
  • Bridge railings have sustained multiple impacts and do not meet current safety standards.

The project improvements are anticipated to extend from 600 feet along Nicasio Valley Road on either side of Nicasio Creek and east along Lucas Valley Road; the existing intersection will be reconstructed. To facilitate construction, the improvements will be installed in stages so that at least one lane of traffic is maintained along Nicasio Valley Road. Access to residential and agricultural properties will be maintained at all times.

The project is 88.5% federally funded through the Highway Bridge Program. The federal funds are being administered through the Caltrans Local Assistance Program. The remaining 11.5% is locally funded.

The anticipated project timeline is as follows:

Spring 2016
Begin Environmental Studies and Preliminary Engineering
Summer 2017 Community Workshops
Summer 2019
Initiate Detailed Design
Fall 2020
Conclude Environmental Review
Fall 2021 Final Design Plans
Summer 2022 Begin Construction


Community outreach and engagement are fundamental to developing the design of the new bridge. The project development process will integrate the community’s vision and resident needs so that they are reflected in the final design. Public meeting(s) will be scheduled and advertised at a later date.

Stay Informed:

For more information, contact Chris Good, Associate Civil Engineer.