Historic Watmaugh Bridge’s years are numbered

To some longtime Sonoma Valley 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 ridge, situated just outside Sonoma city limits on Watmaugh Road, between Arnold Drive and Broadway, continues to live on at the ripe old age of 93, but apparently, its years are numbered. That’s because construction of a replacement bridge is scheduled to begin in 2024-25.

The bridge was built in 1929 and 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, 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 that a video recordation of the bridge was performed as part of the process.

“Bridge projects also include the need for additional right-of-way,” 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 that 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 estimated to cost $7 million.

The bridge has a host of reported structural deficiencies — including the foundations suffering scour damage from Sonoma Creek, unsafe shoulder width and driver visibility, load limit reduced to 71% of capacity and lack of pedestrian or bike pathways due to the narrow width of the span. It also does not meet seismic standards.

Caltrans performs biannual bridge inspections to help determine which bridges may need repair or replacement. The ratings don’t necessarily indicate which bridges could collapse or reflect their ability to carry heavy loads. In 2018, Watmaugh Bridge was given a federal inspection sufficiency rating of 3 out of a possible 100; it currently has a rating of 31. Thompson said she doesn’t know the reason why the rating, while still low, rose so significantly.

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

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

“Vehicles share the road and bridge with pedestrians and bicyclists, and drivers should use caution and lower their speed,” she added.

The bridge was designated Sonoma County Landmark No. 103 in 1981 and the county has acknowledged that 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.”

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

Some community members voiced their opposition, and as recently as 2019, a group of Sonoma residents called for preserving the bridge.

Sonoma Valley resident Johanna Patri, identified as 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 said that “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 says.

Thompson says 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.