As early as 7 a.m. on Saturday, people began to line the fence alongside Wasatch Boulevard, waiting for the big move.
Children were bundled in coats and gloves. One gray-haired man sat in a lawn chair, talking with another man. Dozens of others brought cameras and coffee cups.
At 8 a.m., it happened. Four big machines, stacked with a hodge-podge of support structures all chained together, began to lift and slide one half of the old 4500 South bridge deck from its place over the east-side belt of I-215.
"I was just wondering how they were going to move it," said Collin Tobari, 10, who watched the move with his dad from a vantage along Wasatch.
Cathy Tansimore, standing nearby, was also curious about how the bridge would be moved. The piece moved Saturday morning was nearly four traffic lanes wide and weighed hundreds of thousands of pounds.
"Once I learned the idea was to move the whole piece, I was like ' ... How do they do this without having it fall on the freeway?"' she said.
But it happened without a hitch.
Over about two hours on Saturday, workers hired by the Utah Department of Transportation moved one half of the old 4500 South bridge down a length of the freeway and then placed it atop a structure to be demolished.
The procedure was repeated five hours later with the remaining piece of the bridge. Beginning at 11 a.m. today, workers will move a new bridge in place using the same technique, which allows a structure to be replaced in hours instead of months.
The new bridge has been built alongside the freeway the past five months, in view of passing motorists.
"It's really about minimizing impacts to the public and this is a big step in doing that," said UDOT spokesman Nile Easton, said about the technique. "It's not every day you get to watch big chunks of bridge moved down the freeway."
UDOT contracted with a Dutch-based company, Mammoet, to replace the 4500 South bridge. The company used a machine known as a self-propelled modular transporter to move the bridge segments down the freeway and into the demolition zone.
The transporters have been used extensively in Europe and look similar to flat-bed trailers. They have 64 free-moving wheels that are maneuvered by a man holding a joystick of sorts.
Today, crews will lift the new bridge across I-215, and then set it into place. On Monday, the freeway will be opened to the public and 4500 South will be opened in about 10 days.
Jeff Margetts, who was watching Saturday's bridge move from along Wasatch Boulevard said his family would be looking for good seats today to watch the new bridge put into place.
"We've been waiting months for this," he said. "This is UEA weekend and we're not leaving town because of this. It was this or Yellowstone."