Road crews discovered the separated wall Monday morning. UDOT geotechnical engineers have examined it, and UDOT will today bring in the design and contracting firm that built the wall for a look, agency spokesman Nile Easton said Tuesday.

The wall slipped at a point about a half-mile down the canyon from the Deer Creek Dam. There is no danger to motorists on the existing U.S. Highway 189, nor will the collapse lead to road closures, Easton said.

The 50-foot-by-40-foot section of wall was supposed to stabilize the walls near the dam, Easton said. It is possible UDOT engineers overlooked or didn't know about a problem with the soils under the wall, or the design may have been faulty, he said. Warm weather that led to increased moisture in the soils could have been part of the mix, too, though the wall had a drainage system built into it.

The contractor excavated the site in late spring and finished the wall in late November, Easton said.

The wall was part of a $55 million upgrade of a 4 1/2 mile section, the fourth and final phase of the Provo Canyon Highway reconstruction project that will widen U.S. 189 to four lanes from the Sundance turnoff to a half-mile east of the Deer Creek Dam. Traffic will pass by the dam instead of driving on top of it.

The highway overhaul is a cooperative effort of UDOT and the U.S. Bureau of Reclamation, which governs the dam. Federal crews have been replacing unstable soils from the dam's downstream base as part of a seismic upgrade.

A new bridge over the historic Heber Valley Railroad, extension of the Provo River trail system and restoration of Little Deer Creek area also are part of the project. UDOT expects that the segment of the highway would handle traffic demand for the next 20 years.

Delays have pushed the completion date to 2007.