PORT ANGELES — The U.S. Highway 101 bridge over the Elwha River could need replacement or retrofitting now that two dams have been removed, allowing the now-wild river to erode the riverbed under the bridge, officials say.
When state Department of Transportation crews drilled bore samples earlier this month, they learned that the bridge’s two piers sit atop gravel — not bedrock, as they had hoped, the Peninsula Daily News reported.
“We’re keeping a very close eye on it and we have electronic monitoring on it,” said department spokeswoman Claudia Bingham Baker. “It is safe as long as it is open to the public.”
The bridge was built in 1926, after the Glines Canyon and Elwha dams were constructed. With the dams removed as part of a $325 million National Park Service project to restore the Elwha River to its wild state, the state has placed boulders at the base of the piers to stem erosion. But that’s just a short term fix.
The state installed meters that detect movement on each of the piers. Crews will also continue to monitor the condition of the rip-rap around the two piers.
Sediment from the former Lake Aldwell and high water have scoured the riverbed in which the piers sit, Bingham Baker said. Officials have said the riverbed has been washed out 14 feet down since the Elwha Dam downstream was removed in 2012.
Officials are concerned high flows in the Elwha River, above 8,000 cubic feet per second, could affect the piers. Bingham Baker said the storms last week didn’t appear to affect the bridge.
The DOT isn’t concerned about the other bridges that span the Elwha River, including the state Highway 112 bridge, because they were not built with piers anchored in the riverbed.