Sonoma’s historic Watmaugh Road Bridge to face demolition, rebuild

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The fate of the historic steel-truss bridge on Watmaugh Road over Sonoma Creek is all but settled, according to the county’s department of Transportation and Public Works.

And, despite a lingering hope that the 1929 bridge’s historic status might save it from the wrecking ball, the county expects to move forward with the bridge replacement project beginning in 2021.

Johannes J. Hoevertsz, director of public works, released a statement on March 6 which said a “memorandum of agreement” between a number of federal, state and local jurisdiction was reached “to move forward with the bridge replacement project.”

Among the agencies named in the memorandum of agreement were the Federal Highway Administration, the Advisory Council on Historical Preservation, California Department of Transportation, and the California State Historic Preservation Officer.

The bridge was built in 1929 – and safety studies as recent as last year have shown it has a sufficiency rating of 3 out of a possible 100. The county first proposed replacing it in 2010, and estimated the project could take 10-to-15 years to complete.

However some local residents continue to object to the removal of the bridge, expressing the philosophy of the Historic Bridge Foundation of Austin, Texas: “Somehow we must elevate the importance of our historic bridges in the stories that identify the communities of our nation and say ‘this bridge is part of who we are and it must be saved.’”

Johanna Patri, an area resident and representative of Friends of Watmaugh Bridge, said “This is a very unique bridge and is eligible for the National Register of Historic Places.”

The county acknowledges its potential for inclusion in a national register at the local level, due to its distinctive design characteristics (“of a polygonal top chord Warren pony truss bridge, one of only two that remain in Sonoma County and one of 24 statewide”). It is Sonoma County Landmark No. 103, designated in 1981.

But outweighing that are concerns about structural deficiencies including the bridge’s pier foundations suffering scour damage from Sonoma Creek, unsafe shoulder width and driver visibility, load limit to 71 percent of capacity and lack of pedestrian or bike pathways due to the narrow width of the span.

And what may be the most crucial: “Does not meet modern seismic standards and could be subject to collapse during an earthquake.”

In fact, when the Sonoma County Board of Supervisors certified the final environmental impact report (EIR) in 2012 for the removal of the bridge, it adopted a “Statement of Overriding Considerations for the Removal of a County-Designated Landmark” due to those safety concerns.

“The bridge has not fallen down, including Caltrans detouring over-load vehicles during flooding all these years,” counters Patri, referring to the high rainfall year of 2017 when Caltrans detoured Highway 121 traffic up between Arnold and Broadway across Watmaugh Road.

When, at a March 2017 public hearing on the bridge replacement project, Caltrans was made aware of the safety risk and road conditions of Watmaugh, they changed the detour route to Leveroni Road.

The bridge’s historical value was affirmed in a 2018 “Finding of Adverse Effect” by contract archaeologist Vicki R. Beard of Rohnert Park. That study followed the finding by Caltrans that an adjoining property at 240 W. Watmaugh Road, known as McElroy Ranch, was not eligible for listing in the National Register of Historic Places.

But seismic vulnerabilities and structural deficiencies, along with rust, foundation erosion and scour-related deterioration, has made the bridge’s replacement inevitable.

As outlined by the county, the project would demolish the existing truss bridge and replace it with a new concrete 32-foot wide box girder or concrete slab bridge, essentially along the alignment of the current bridge. In an effort to maintain the visual setting of the existing bridge, the trusses from the bridge will be retained, restored to the extent practicable, and added to the new bridge as a nonstructural element.

One of the terms of the county’s agreement with the state and regional historic bodies is that “stakeholders are invited to collaborate in the development of educational tools, materials, and exhibitions to memorialize the importance of Watmaugh Road Bridge to the historic development of Sonoma County.”

The county’s proposal is to “document the current bridge and its history through the preparation of large format photographs and a historical narrative produced to Historic American Engineering Record standards.”

“It is our hope that we can collaborate with your organization to develop educational tools, materials or exhibitions to memorialize the importance of the Watmaugh Road Bridge to the historic development of Sonoma County” reads the letter, signed by Rich Stabler, a senior environmental specialist at Permit Sonoma.

The letter inviting participation in developing the educational materials was sent to 10 organizations with an interest in historic bridges in general and the Watmaugh Road Bridge specifically, including the Sonoma Valley Historical Society, Sonoma County Landmarks Commission, Friends of Watmaugh Bridge, Sonoma County Historical Society, Sonoma League for Historic Preservation and others. The deadline for responding to the invitation was Feb. 5 of this year.

The Index-Tribune has not been able to verify that there have been any responses to the invitation.

Contact Christian at christian.kallen@sonomanews.com.

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