FERNDALE — Damage to the Nooksack River Bridge on Slater Road has closed of one of Whatcom’s busiest county roads for weeks, Whatcom County Public Works officials said.

The arm of an excavator being hauled on a tractor-trailer was positioned too high, causing it to strike six overhead support beams on the bridge about 9:25 a.m. Saturday, Dec. 1, said county engineer Joe Rutan.

In addition to visible damage to the overhead beams, the sides of the structure bent inward slightly upon impact, and stresses to the steel were discovered throughout the span, Rutan said.

Scott Jeffers, 53, of Bellingham was hauling the excavator on a 1997 Peterbilt tractor-trailer owned by Scrap-It, a recycling company on Slater Road just east of the bridge, Sheriff Bill Elfo said. Jeffers was eastbound when the excavator struck the bridge, the sheriff said.

Deputies have yet to file for charges with the county Prosecutor’s Office, Elfo said.

A call to Brian Parberry, owner of Scrap-It, was not returned.

County officials on Monday, Dec. 3, were finalizing a contract with Flame On Inc., of Monroe, to do the highly specialized heat straightening that will be required to fix the bridge.

The repairs will be more complicated and costly than those made to the same bridge six years ago after a similar collision.

In 2006, the county paid Flame On $133,000 after a truck carrying a large vessel struck the bridge’s overhead supports on its way to the Phillips 66 Ferndale Refinery, then known as the ConocoPhillips refinery, Rutan said. The bridge was closed for 34 days that time.

“The damage on this one isn’t as severe, but there’s more members damaged,” Rutan said. “We expect this is going to be more expensive.”

Saturday’s accident was the third time in a decade that the bridge has been damaged in a collision. The first, in 2002, also involved an excavator, Rutan said.

Repair work will be weather-dependent, and rain could further delay the reopening of Slater. The county road, a major route to Lummi Island, Lummi Nation and the tribe’s casino, averages 12,120 trips a day at the bridge, according to a count conducted in July.

“It is an inconvenience for everybody that either lives at Lummi Nation, and all of our players that come to Silver Reef,” said Aaron Thomas, the casino’s director of marketing.

Alternate routes are posted on the Silver Reef Hotel Casino Spa website, SilverReefCasino.com. Drivers can reach the casino and other destinations west of the Nooksack River on Slater Road from downtown Ferndale to the north and from Marine Drive to the south.

The same oversized load struck at least one power line Saturday before hitting the bridge, knocking out power to 495 customers of Puget Sound Energy, said utility spokeswoman Terri-Ann Betancourt. About 450 customers had power restored within an hour, but the power wasn’t back for all customers until 5:55 p.m. Saturday, she said.

The Lummi Nation Twitter account, @lummicomm, reported Saturday morning that power was out on 60 percent of the reservation.

Reach RALPH SCHWARTZ at ralph.schwartz@bellinghamherald.com or call 715-2298.