San Antonio Bridge Replacement Project

Rosemarie Gaglione, Director, Public Works
San Antonio 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. San Antonio Road Bridge over San Antonio Creek is one of the bridges identified for replacement and the project is in the preliminary engineering phase.

A second public meeting was held on January 23, 2017 from 6pm-8pm at Novato City Hall:

Approved by Caltrans as part of the Marin Sonoma Narrows (MSN) HOV Widening Project Final Environmental Impact Report/ Environmental Impact Study (FEIR/EIS) which was adopted and cleared in October 2009. The San Antonio Road Bridge Replacement Project (Project) proposes to realign a portion of San Antonio Road including construction of a new bridge over San Antonio Creek. The project is needed to replace an existing aging and deficient bridge and provide safe bicycle accessibility along the shoulders to serve the local area. Sonoma County is a half owner of the bridge and a partner in the Project. County of Marin is the lead agency but has delegated the initial development responsibilities to the Transportation Authority of Marin (TAM). The Project is funded using Highway Bridge Program (HBP) funds which are administered through the Caltrans Local Assistance Program.

San Antonio Road Bridge is located at the border of Marin and Sonoma Counties where San Antonio Road crosses San Antonio Creek. San Antonio Road begins at Highway 101 at the Redwood Landfill interchange and proceeds north toward Petaluma. There is a tee-intersection on the north side of the existing bridge where the west leg continues toward the west side of Petaluma and the east leg currently extends toward a few private residences but formerly provided access to Highway 101.

The existing bridge was built in 1917 and is one of the earliest remaining standard reinforced concrete girder bridges to be designed by the California Highway Commission. As such, the bridge is eligible for listing on the National Register of Historic Places. The single span bridge is 100 feet long and has a 23 feet wide clear width for traffic with no shoulders. The bridge needs to be replaced for the following reasons:

  • The existing structure is classified as structurally deficient and functionally obsolete.
  • The existing structure contains areas of concrete cracking and corrosion to the reinforcing steel.
  • The elevation of the underside of the existing bridge is too low to accommodate flood events. San Antonio Creek frequently floods upstream of the bridge and roadway approaches frequently flood during extended periods of rainfall forcing the road to be closed to traffic. Current standards require the height of the bridge be raised to accommodate a 100-year flood event.
  • The existing bridge cannot be retrofitted due to its historical significance.
  • The existing narrow bridge deck does not have adequate width to accommodate vehicle, bicycle and pedestrian traffic.
  • Bridge railings do not meet current safety standards.

The Project would realign San Antonio Road to the west of the existing bridge on a curved alignment and construct a new two-lane bridge with shoulders across San Antonio Creek. The shoulders would accommodate Class II bicycle lanes. The shoulder on the west side of the bridge would be wider to improve sight distance for southbound traffic. A new intersection would be constructed on the north side of the new bridge to provide access to private properties to the east. The existing bridge would remain since it is deemed of historic importance and would be used for bicycle and pedestrian access. The new bridge would be elevated to accommodate the 100-year flood event.

The project improvements would extend approximately 200 feet south and 500 feet north of the new bridge on San Antonio Road. During construction, the existing bridge will remain open to traffic. Bridge construction is planned to be complete in a single season to minimize impacts to riparian areas of the creek. A future phase of the MSN project would construct bicycle lanes each side of the old bridge to create a continuous trail between Novato and Petaluma.

Environmental Planning Phase (Lead by Caltrans)

San Antonio Bridge Replacement is part of the MSN project and during the environmental planning phase extensive public outreach efforts were conducted by Caltrans beginning in 2001, see links below:

A summary of those efforts are provided below:

  • May 2, 2001: FHWA published a Notice of Intent (NOI) under NEPA to prepare an EIS in the Federal Register.
  • April 23, 2001: Caltrans submitted a Notice of Preparation (NOP) to prepare an EIR under CEQA to the California State Clearinghouse.
  • August 1 and August 22, 2001: Caltrans held public scoping meetings in Novato and Marin County, and in Petaluma and Sonoma County, following the NOI/NOP filings. These meetings were advertised in local newspapers and invitations were mailed to over 100 interested parties. They were attended by 103 people.
  • November 18 and 19, 2002: Caltrans held additional public meetings in Novato and in Petaluma once the Central Segment alignment was determined. These meetings were advertised in local newspapers and invitations were mailed to over 250 interested parties. They were attended by 63 people.
  • Multiple meetings with coalition of bicycle/ pedestrian interest groups and SMART to discuss replacement of bicycle access within Segment B.
  • Public outreach specifically targeted towards residents in Petaluma who were concerned about noise, including the Payran/ McKinley Neighborhood Action Committee.
  • Quarterly Policy Advisory Group (PAG) meetings alternating between the cities of San Rafael (Marin County) and Santa Rosa (Sonoma County) which consisted of the following elected officials from the cities and counties of Marin and Sonoma in 2006/ 2007:
    • PAG Chair: Supervisor Steve Kinsey – Marin County Board of Supervisors, District 4
    • PAG Vice Chair: Supervisor Mike Kerns – Sonoma County Board of Supervisors, District 2
    • Supervisor Judy Arnold – Marin County Board of Supervisors, District 5
    • The Honorable Bob Blanchard – Mayor, City of Santa Rosa
    • The Honorable Peter Breen, Mayor, Town of San Anselmo
    • Councilmember Carole Dillon-Knudson, City of Novato
    • The Honorable Jeanne MacLeamy – Mayor of Novato
    • Supervisor Paul Kelley – Sonoma County Board of Supervisors, District 4
    • The Honorable Pamela Torliatt – Mayor, City of Petaluma
    • Alternate: Petaluma Councilmember – Samantha Freitas
    • Alternate: Novato Councilmember – Jim Leland
  • Interchange and frontage road/ access configuration alternatives evaluation process reviewed by a team of Caltrans design, engineering, and environmental specialists, TAM, SCTA and the PAG. These included various combinations of interchanges and frontage road configurations. In total, 15 different packages were identified. In order to screen the wide array of options for the most viable candidates for further study, the team scored each of the options in terms of operational flexibility, access to private parcels, land acquisition, potential growth inducement, visual resource impacts, parkland impacts, biological resource impacts, cultural resource impacts, and costs. The combined scores were used to identify the four Access Options.
  • June 15 and 16, 2005: Caltrans held additional public meetings in Novato and in Petaluma to preview the four Access Options within Segment B. These meetings were advertised in local newspapers and invitations were mailed to over 250 interested parties. They were attended by 35 people. It was explained that each of the options would be considered at an equal level of detail in this DEIR/S, and that one Access Option would be combined with one of the Build Alternatives as the preferred alternative.
  • Multiple local constituency meetings throughout the process in Marin and Sonoma counties and with state, federal, and local agencies (see Table 6.1, Figure 6-9, 6-10, and 6-11 below).

The Draft EIR/EIS was released on October 16, 2007; distribution of the document and a public comment period of 60 days followed (ending December 14, 2007). The Draft EIR/EIS was available for viewing at TAM, Sonoma County Transportation Authority (SCTA), the Community Center at Lucchesi Park, and several city and regional libraries throughout the area. Caltrans received over 700 comments during the comment period.

  • Caltrans, TAM, and SCTA hosted two public meeting open houses to present the findings of the Draft EIR/EIS on the MSN Project. Pursuant to California Environmental Quality Act (CEQA) and National Environmental Policy Act (NEPA) guidelines, local residents, elected officials, interested property owners, local businesses, and other interested parties of the general public, were notified of the document release and the public meetings through local newspapers and letters of notification to people on the project mailing list. A Notice of Availability also appeared in the Federal Register on October 26, 2007. The two public meeting open houses were held on November 6, 2007 in Petaluma at the Beverly C. Wilson Hall located at the Sonoma-Marin Fairgrounds and November 14, 2007 in Novato at the Novato Unified School District Board Room. During the meetings, a presentation was given on the overview of the project and the project schedule information. Fifty five people signed in at the two meetings. A court reporter was also on hand to record comments and project staff was on hand to answer questions.

Public Outreach

Due to the passage of time, the counties of Marin and Sonoma initiated further public outreach efforts in Spring 2015 to present design refinements to the proposed bridge improvements prior to commencing detailed design. To better understand the community’s interests and concerns around the project, a public work shop meeting was held on September 9, 2015 at the Margaret Todd Senior Center. The public workshop meeting provided an opportunity for the public to learn about the bridge replacement project, ask questions, and provide input. A summary of the San Antonio Bridge Public Meeting is provided in the link below:

San Antonio Meeting Summary & FAQ

The project is 100% federally funded through the Highway Bridge Program. The federal funds are being administered through the Caltrans Local Assistance Program.

The anticipated project timeline is as follows:

Summer 2015
Preliminary Engineering
Fall 2015 / Spring 2017 Community Outreach
Spring 2018
Finalize Environmental Revalidation
Spring 2018
Initiate Detailed Design
Fall 2018
Right-of-Way and Permits
Winter 2019/20 Final Design Plans
Summer 2020 Begin Construction

All dates are subject to change.


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. A second public meeting will be held and advertised for this project. The schedule will be determined at a later date.