Sonoma’s historic Watmaugh Bridge’s years are numbered

To some longtime Sonoma residents, the Watmaugh Bridge is a historically unique treasure that provides a link to the city’s colorful past. To others it is a deteriorating, seemingly dangerous eyesore in dire need of replacement.

The steel-truss bridge, which is situated just outside Sonoma city limits on Watmaugh Road between Arnold Drive and Broadway, turns 94 this year, but its years are numbered.

Construction of a replacement bridge is scheduled to begin in 2024.

The county has planned to replace it since 2003, when road officials found that water had seeped through the concrete and rusted the rebar running along the underside of the bridge’s surface. This caused chunks of concrete to break off and fall into the creek bed.

“Bridge projects take a very long time to bring to construction,” said Janice Thompson, deputy director of Sonoma Public Infrastructure (formerly General Services). “Environmental concerns can take years to work through. This bridge is considered historic, and we have worked closely with the community, (Sonoma County) Supervisor (Susan) Gorin’s office, Sonoma Landmark Commission and the State Historic Preservation Office to ensure the proper process for removal of a historic bridge.”

Thompson said a video recordation of the bridge was performed as part of the process.

“Bridge projects also include the need for additional right-of-ways,” she said. “The new bridge will be constructed adjacent to the existing bridge. The new alignment includes relocation of existing utilities. All of these take time to coordinate.”

Thompson said the county has collaborated with the community and Gorin’s office on the design phase of the new bridge.

“The coordination will result in steel trusses from the existing bridge being preserved and placed on the new bridge as an architectural feature to commemorate the historic bridge,” she said.

She didn’t provide an estimated completion date for the project, but said it is federally funded and expected to cost about $7 million.

The bridge has numerous structural deficiencies — including foundational scour damage from Sonoma Creek, unsafe shoulder width and driver visibility, a load limit reduced to 71% of capacity and it lacks pedestrian and bike pathways because of its narrowness. Officials said It also does not meet seismic safety standards.

In 2018, Watmaugh Bridge underwent a federal inspection and received a sufficiency rating of 3 (very poor) out of a possible 100 (very good). The bridge’s current rating is 31. Thompson said she doesn’t know why the rating, while still low, rose so significantly.

The Index-Tribune previously reported that out of more than 100,000 heavily used bridges, which have received federal inspections, only about 4% score below 50.

Thompson said the Watmaugh Bridge is considered vulnerable to a seismic event, but is otherwise safe for all users.

The bridge was designated Sonoma County Landmark No. 103 in 1981 and the county has acknowledged it potentially could be included in a national register at the local level due to its distinctive design — “a polygonal top chord Warren pony truss bridge, one of only two that remain in Sonoma County and one of 24 statewide.”

In 2012, when the Sonoma County Board of Supervisors certified the final environmental impact report for removal of the bridge, however, it included a “Statement of Overriding Considerations for Removal of a County-Designated Landmark” due to safety concerns.

In response, a contingent of community members rejected any plans to remove the bridge. And as recently as 2019, they continued to call for the bridge to be preserved.

Sonoma Valley resident Johanna Patri, a representative of Friends of Watmaugh Bridge, told the Index-Tribune in 2019 that it is a “unique bridge and is eligible for the National Register of Historic Places.”

Thompson, though, said “rehabilitation of the existing bridge was considered in the preliminary design phase, but replacement was determined to be more cost efficient.”

Current Watmaugh construction

Meanwhile, just down the road from Watmaugh Bridge, a construction project that began in December continues on Fowler Creek Bridge, limiting the road to a single lane in one section. That requires vehicles in opposite lanes of traffic to take turns passing through the section of Watmaugh Road.

“There are scouring issues in which the creek flow has undermined the foundations of the road,” Thompson said. “The one-lane closure was done in an abundance of caution to keep everyone safe.

“We’re hoping that the work will be done by this summer.”

The Fowler Creek Bridge is so small and inconspicuous that many people probably don’t even realize they are passing over a bridge, she said.

Thompson said that Leveroni Road, which is less than 1 mile north of Watmaugh Road, can be used as a detour during the construction.

Funding for the Fowler Creek Bridge project is coming from Measure M Local Roads and State Senate Bill 1, the Road Repair and Accountability Act.

Reach the reporter, Dan Johnson, at daniel.johnson@sonomanews.com.