Back in 2010, when the county proposed replacing the Watmaugh Bridge over Sonoma Creek, a senior engineer with the county's Transportation and Public Works Department estimated it could take 10-to-15 years to replace the bridge depending on the circumstances.
The estimated timeline six years ago is starting to look pretty good.
According to a department spokesperson, the earliest construction might start would be the summer of 2020.
'The Watmaugh Bridge is on Caltrans' mandatory seismic bridge replacement list,' said Jennifer Larocque, the department's Public Affairs Program Manager.
The county has long been talking about replacing the bridge. It was on a list at least 13 years ago of Valley bridges that were targeted for replacement.
The bridge, which was built in 1929, has a sufficiency rating of 4 out of a possible 100. The Interstate 35 bridge that collapsed in Minneapolis in 2007 killing 13 and injuring 145, as an example, had a sufficiency rating of 50.
In an I-T story in 2003, a county road official said that water had also seeped through the concrete and rusted the rebar running along the underside of the bridge's surface, causing chunks of concrete to break off and fall to the creek bed.
Back in 2011 and 2012, some Valley residents questioned why the bridge had to be replaced instead of a seismic retrofit. The county's Landmarks Commission held numerous hearings on the bridge. But since state and federal funds were going to be used for the project, the funds could only be used for a new structure, not a retrofit.
At that time, the county said it would use some of the elements from the aging bridge on the new bridge.
After first proposing a 40-foot-wide bridge, the county scaled it back – proposing a 32-foot-wide bridge that would have two 11-foot travel lanes and two 5-foot-wide shoulders for pedestrian and bicycle traffic. The current bridge is 22-feet wide with no pedestrian or bicycle lanes.
The county would also incorporate the trusses from the bridge, but as ornamental and not structural.
'While completing the necessary environmental studies earlier this year, Caltrans requested we re-evaluate the historical elements of the bridge,' Larocque said. 'Based on feedback from the community and permitting agencies, we're developing a proposal that preserves elements of the existing structure and minimizes environmental impacts.'
She said the department plans to have more information available early next year.
Another bridge that's still in the county's pipeline is the Boyes Boulevard bridge, also over Sonoma Creek.
In 2013, the Board of Supervisors approved a $620,278 engineering design contract with Moffatt & Nichol, a Walnut Creek engineering firm.
The project was estimated to cost about $6.5 million and take about a year, but at that time, the county estimated the construction would start in 2015 or 2016.
The bridge has been in the county's list of replacement bridges since 1997.
In a memo to the County Board of Supervisors, then Assistant Public Works Director Tom O'Kane said the project would replace the existing 'structurally deficient two-lane Boyes Boulevard Bridge with a new two-lane bridge designed to meet current design standards including improvements to roadway approaches.'
The new bridge will be built to accommodate 'the 100-year storm event.'
While the replacement bridge will not increase traffic capacity, it would include a 5-foot shoulder for bicycles and a 5-foot sidewalk for pedestrians.
Larocque said the department is currently working directly with property owners adjacent to the Boyes Boulevard Bridge to acquire permanent and temporary construction easements required for the project.
On Dec. 13, the Supervisors will vote on a proposal to buy a lot adjacent to the bridge for $285,000 as part of the project.
'After these acquisitions are made, we will provide an update to the community with information on the construction schedule,' Larocque said.
'We anticipate construction to start in 2018,' she added.
Email bill at bill.hoban@sonomanews.com.
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