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Sellwood Bridge packs up and moves north

by: DAVID F. ASHTON - Workers watch as the Sellwood Bridge truss starts its journey, looking like a ship pulling away from its dock, in the thick morning fog.Through the night of January 18, the Sellwood Bridge’s movers, Omega Morgan Co., stood guard on the concrete deck, on the catwalk, and on the concrete piers below.

On Saturday, January 19th, “moving day”, it was early – about 8 am – but not bright. The historic 1,100-feet steel bridge’s main span, now lifted an inch higher than it had been any time in its 87 years, was enrobed in thick fog. The historic move of the bridge north onto the nearby new temporary piers that will hold it for the time it takes to build the new Sellwood Bridge was underway.

And, standing near the ragged, dismantled edge of the west end approach was Multnomah County’s project spokesman, Mike Pullen. The 3,400 ton steel truss looked as if it were drifting off into the clouds.

“It’s kind of eerie,” Pullen observed. “It’s so quiet – not hardly a sound.”

There was no vibration; no thumping of machinery; no screech of metal against metal. “I was surprised to learn that only 135 horsepower was required to move it!” Pullen remarked.

The ski-shaped steel skid beams under the bridge slid very slowly, and silently, over the Teflon pads installed in the track beams below, lubricated – Pullen revealed – by the contractor’s “secret sauce” – Dawn dishwashing liquid!

Choreographed by Omega Morgan’s chief project engineer, who was continuously monitoring a digital power controller, all of the pushing jacks were moving their respective loads proportionally. As planned, the west end of the bridge was moving 66 feet north – twice as far as the east end, pivoting without buckling the long aging truss.

John McCalla, President of Omega Morgan, talked on his cellular phone with lead staff members.

“This is a unique challenge to our team,” McCalla told THE BEE. “This is what they live for; it brings out the best in them.”

Instead of a continuous move for the bridge, McCalla said, it’s inched in increments, a little at time. After each increment, crews measure each of the bearing points within a tenth of an inch, to determine if the pressure on any of the pushing jacks needs to be adjusted. The concern was to avoid bending the Sellwood Bridge.

“We have very experienced professional engineers on staff, who have done jobs like this all over the country – and, for one of the engineers, all over the world,” McCalla added. “They know how to run the hydraulic calculations to get the right jacks moved the right distance at the right times.”

By noon that Saturday, the sun had burned off the fog, and observers on both sides of the Willamette River could see that the long steel truss was well on its way.

The journey ended about 9:30 pm. The west end had traveled north 66 feet, and the east end 33 feet, exactly as required. And crews set about finishing the new connecting ramps to route traffic onto the relocated span, which will serve as a “detour bridge” for the entire time the new, wider Sellwood Bridge is being built in the space the old bridge had been occupying.

The old bridge was scheduled to reopen to relieve the extreme traffic congestion that its closing had created at 7 am on Thursday, January 24. Things went so well, the bridge was reopened early – at 3:30 pm on Wednesday afternoon January 23. (See separate story.)