PROVO CANYON — Just as the future of U.S. 189 was starting to take shape, a concrete section designed to provide stability to the hillside came sliding down.

A 50-foot-wide, 80-foot-high chunk of concrete about a quarter-mile west of the Heber Valley Railroad trestle bridge failed early Monday, said Nile Easton, spokesman for the Utah Department of Transportation.

The concrete failure took place on the new highway alignment, part of UDOT's $55 million Provo Canyon highway reconstruction project, and did not pose any danger to motorists on U.S. 189 or create any traffic problems, Easton said.

The slippage likely was weather related, he said, a result of recent moisture and warming that caused the soil below the concrete section to destabilize.

"We had taken what we felt were steps to prevent that from happening," Easton said.

An assessment to determine exactly what caused the problem and to ascertain whether or not it was an isolated incident will take about two weeks, he said.

"We're very curious to find out what happened," Easton said. "A key part of this project was working on the stability of the geology there."

UDOT has experienced consistent problems with slippage occurring underneath U.S. 189 in Provo Canyon for years, he said.

The concrete section's failure isn't expected to add to the project's cost, though that could change if more stabilization areas are found to be faulty. The failed section had been in place since November, Easton said.

"What we want to do is figure out whether or not it's going to impact the other sections," he said.

The stabilization is just a small part of the U.S. 189 highway widening project, now in the third of four phases.

"Any motorist driving through Provo Canyon will see some of the changes that are taking place," said Geoff Dupaix, UDOT regional spokesman.

The most noticeable changes are the two bridges being constructed — one crossing over the Heber Valley Railroad and the other bridging the spillway at the base of Deer Creek Dam.

The project's current phase calls for the widening of U.S. 189 to a four-lane divided highway between the junction of U-92 and the dam, which UDOT officials say will accommodate projected traffic demands for the next 20 years.

"We currently have a four-lane section from 800 North all the way up to the turnoff to Sundance (U-92) in previous phases of the project, and this is the next phase of widening the highway to four lanes — two lanes in each direction," Dupaix said.

The four-mile segment has been under construction since this past summer and was scheduled to be completed in late 2006. That completion date was recently pushed back to early 2007, he said, but it had nothing to do with the concrete structure failure Monday.