Dam gets shored up

PROVO CANYON — When "the big one" hits, Deer Creek Dam will be ready.

The U.S. Interior Department's Bureau of Reclamation since 2003 has been spearheading modification efforts for the 65-year-old dam to make sure it is able to withstand a large earthquake.

And that's good news for Utah County's 400,000-plus residents potentially at risk from such a seismic event.

"The dam is safe now, but we're just trying to make it safer," said Brent Rhees, deputy area manager in the Bureau of Reclamation's Provo office.

Deer Creek Dam in Utah County and Pineview Dam in Weber County were highlighted in the U.S. Geological Survey's 1976 loss-estimate study of the Utah region for earthquakes, said Walter Arabasz, director of the University of Utah Seismograph Stations.

"They pointed out at that time the particular problem of Pineview Dam and Deer Creek Dam as each having large downstream populations that would be severely impacted if there were an earthquake that compromised either of those two dams," Arabasz said.

That resulted in the Bureau of Reclamation undertaking "extensive seismological and geotechnical studies to characterize the earthquake threat to each of the structures and their respective vulnerabilities," he said.

A three-phase project to upgrade and renovate Pineview Dam was completed in December 2004, according to the Bureau of Reclamation.

The seismic upgrades to Deer Creek Dam were deemed necessary after exploratory drilling in the late 1990s found layers of soil downstream from the foundation of the dam that could liquefy if subjected to a significant earthquake, said Brandt Demars, resident engineer in the reclamation bureau's Provo office.

Under the Safety of Dams Act of 1978, the Bureau of Reclamation was able to receive federal funding for the two phases of modifications, Rhees said. Federal funds will cover 85 percent project, and the Provo River Water Users Association will cover the remaining 15 percent, he said.

Phase 1 of the project cost about $12 million, Demars said. Cost for the second phase is unknown.

A risk analysis was also required to receive the funding, Rhees said, but it was essentially a formality. The Safety of Dams Act defines unacceptable risk as "the possibility that one person may be harmed by a deficiency."