The Interstate 5 bridge over the Nooksack River at Ferndale is similar in many ways to the bridge that crumpled into the Skagit River after it was hit by a truck on Thursday, May 23.
Both bridges were built in 1955 and were labeled "functionally obsolete" by the Federal Highway Administration, according to data made available on the Nationalbridges.com website.
That doesn't mean the bridges were considered at risk of collapse. It does mean that the height and width of the bridges are not up to modern standards.
"If we built that bridge today we would build it differently," Washington Department of Transportation spokesman Dave Chesson said.
The condition of the superstructure of both the Skagit and Nooksack bridges had been rated "fair" by the federal agency.
Both bridges also got identical comments for their overall structural evaluation: "Somewhat better than minimum adequacy to tolerate being left in place as is."
Chesson said there were no immediate plans for special inspections or precautions at the I-5 Nooksack River bridge or other older truss bridges in Whatcom County and around the state.
Chesson said that while an investigation of the collapse of the Skagit River bridge is still under way, it appeared to be the result of an impact from an unusually strong and heavy truck-mounted structure - not a routine collision.
"We've had bridge strikes before by truck," Chesson said. "This is an extraordinary event."
In Whatcom County, the replacement of the shakiest truss bridge is scheduled to begin this summer.
That structure, the Potter Road Bridge, is the most structurally deficient bridge under county management, county engineer Joe Rutan said. It crosses the South Fork of the Nooksack River just off Highway 9 between Deming and Acme and carries fewer than 1,000 vehicles a day. But it is the only access to the farms and homes on Hillside, Uluquance and Caron roads.
"I'm glad were redoing Potter," Rutan said. "If Potter got hit like (the Skagit River bridge), it would be down."
A two-lane concrete bridge with no side or overhead structure will be built to replace the single-lane truss bridge starting in August. The new bridge is scheduled to open in 2014.
Another county-managed truss bridge, on Slater Road over the Nooksack River, has been struck and damaged by vehicle loads three times in the past decade but has remained intact.
"Slater is a lot stronger. It has handled those hits actually pretty well," Rutan said.
A tractor-trailer carrying an excavator struck six overhead beams Dec. 1, 2012, on the Slater Road bridge. It was closed for repairs for 20 days.
County engineers are considering overheight detectors on the Slater bridge that would flash their lights when an excessively high load was approaching, Rutan said.
He was skeptical these would prevent future impacts with the bridge.
"I don't know how much those would actually be effective," Rutan said. "It still requires the driver of the vehicle to make some decisions and stop."
The third truss bridge in county jurisdiction is on Mosquito Lake Road over the middle fork of the Nooksack River. The county won an award for rehabilitation work it did on the bridge in 2010, Rutan said.
The three bridges are inspected every two years. The Slater and Mosquito Lake bridges are structurally sufficient, Rutan said.
"I hold our bridge program as one of the best things we do," Rutan said. "We are meeting all our requirements for inspection."