PROVO CANYON - The first girders for a massive bridge that will rise on Provo Canyon's east side were dropped into place this week, giving drivers a better view of how traffic will eventually pass by - instead of on top of - Deer Creek Dam.

The steel is just the latest addition to the Provo Canyon Project, a $55 million upgrade for the fourth and final phase that will widen U.S. 189 to four lanes - from the Sundance turnoff to a point a half-mile past the dam.

The bridge undertaking is a complex part of a highway overhaul requiring cooperation from both the Utah Department of Transportation and the U.S. Bureau of Reclamation, which governs the dam.

When finished, the 500-foot-long bridge will run diagonally nearly 100 feet in the air across the dam's face, northwest to southeast. It will abut the dam at its south end.

Crews are constructing a berm alongside most of the west facade. That will facilitate the bridge's southeast end and better stabilize the dam.

While UDOT's contractor plunges ahead with the bridge structure, Bureau of Reclamation experts also are bringing the dam up to the latest seismic regulations and installing new filter systems to increase the efficiency of necessary drainage.

"It's an excellent example of the federal government and the state government working together," said Bureau of Reclamation spokesman Don Merrill.

Specifically, federal crews are replacing unstable "liquefiable" soils from the dam's downstream base with stronger soil types, while installing a chimney drain between the dam and the new berm.

The majority of the soil is near the dam's spillway. When finished, the upgrade will seismically stabilize the dam, says Bureau of Reclamation engineer Brandt Demars.

"Right now [the spillway] couldn't take that strong lateral shaking motion of a earthquake," Demars said.

The bridge buttressing the dam not only will solidify both structures, but allow traffic along the bridge to move more safely.

As it stands now, the highway requires 25 mph speeds at sharp curves on both ends of the dam.

"It improves the ability to take the turns in that area at a more-constant speed," said UDOT spokesman Geoff Dupaix. "It reduces the two sharp curves that are currently there."

Construction crews are also busy with excavation of the mountainside just east of the dam and with groundwork for the new stretch of U.S. 189 that will run north of the current highway - from Horseshoe Bend to the bridge.

The project includes other elements as well.

Just east of the Sundance turnoff, a wall up to 40 feet high will separate eastbound and westbound lanes.

"There's a lot of different types of work going in in just that 4 1/2 -mile area," said UDOT engineer Jim Golden. Added Dupaix, "This is a complex engineering project."

Delays have pushed the completion of this phase of the Provo Canyon Project back to at least 2007, Golden says.

thollingshead@sltrib.com