The

on Saturday provided daylong entertainment for a giddy crowd of hundreds of awestruck onlookers, as its 6.8 million-pound span moved -- in what seemed miraculous to many -- inches at a time onto new, temporary supports.

The move came off flawlessly, capping months of intense planning and detailed preparations.

Traveling about six feet per hour, the bridge's 1,100-foot-long steel truss slid so slowly along specially built tracks that actual movement was nearly impossible to discern.

The 87-year-old bridge snail's pace, however, did nothing to dampen enthusiasm among people of all ages who showed up to witness what many characterized as a once-in-a-lifetime spectacle.

"There's a smile on every face," said Blythe Nordbye, who walked from her Johns Landing home to see the move. "It's hard to describe exactly why, but this is all just incredibly exciting."

Allison Sliter and Michael Wolfe made the bridge's east end a stop of their weekly bike ride. Bundled against the cold morning air, both said the journey was worthwhile.

"I'm amazed at the immensity of moving a bridge," Sliter said.

Added Wolfe, "It's a festival here. Just very, very cool."

Asked by a crowd member to describe the monitoring system, Multnomah County engineer Chuck Maggio said, "We've got five survey laser targets, 10 GPS sensors, 30 stress-strain gauges, 10 sets of smart levels and about 30 sets of eyeballs up there. We're definitely keeping track of what's happening."

The move was complicated by the fact that a new interchange at the west end must be considerably larger than the current one. To provide the extra space, the bridge had to move in a skewing motion like a windshield wiper, traveling 33 feet on the east end, but double that on the west.

"Figuring out that arcing motion was probably our biggest challenge," Omega Morgan's McCalla said. "We've moved things that are heavier before, but probably nothing quite as complicated as this."

Crews perched on each of the span's five concrete piers relied on timing provided by radio communications to trigger each new push of powerful hydraulic jacks. The bridge's weight-bearing points, already lifted by other jacks, slid horizontally along special beams coated with Teflon pads to ease resistance.

In an additional effort to make the pads even slicker, they were dabbed with a coating of Dawn liquid detergent.

"It's just something the guys have found that works," said McCalla, adding that he was unaware of anything longer than the Sellwood Bridge ever being moved in a single piece.

The bridge now sits on temporary steel supports, which will be removed after the new bridge is completed in the same spot as the old bridge, next to the temporary bridge.

Multnomah County Commissioner Deborah Kafoury, credited with helping assemble the financing package that made the $307.5 million project possible, ventured out onto the steel truss during the move.

"The way I could tell it was actually moving was that it felt like a minor, minor earthquake as it shook a little," she said.

The old bridge will now serve as a detour route until the new span is completed in the summer of 2015. The detour, known in engineering parlance as a "shoofly" bridge, is scheduled to open to cars, cyclists and pedestrians Thursday at 7 a.m.

With the old bridge safely out of the way, activity will now resume on a temporary work bridge just upstream that will serve as a platform for building the new span.

Other than a few celebratory high-fives to mark completion of the bridge's historic move, it's back to full speed ahead, said Ian Cannon, the county's bridge engineering services manager.

"After today," he said, "the work really starts."

--