About 6 percent of the 1,788 bridges maintained by the state in Utah are considered structurally deficient by national ranking standards, according to a Utah Department of Transportation official.

Shana Lindsey, director of research and bridge operation for UDOT, said in an interview that 13 percent of the nation's nearly 600,000 bridges are structurally deficient under standards of the Federal Highway Administration.

"The average bridge (in Utah) has a 50-year life span, and most have lived that," John Njord, UDOT director, said during a meeting of the legislative interim transportation committee Wednesday. "Over 500 bridges need to be repaired in the next 10 years."

Njord assured committee members that UDOT is regularly checking and servicing bridges to ensure they are safe for the public to use and that if a bridge were ever a concern it would be closed. Most bridges in the state have been built with redundancy so that if a major part fails the structure won't collapse, Njord said.

All bridges that are maintained by the state are inspected every two years, Lindsey said. Those that are considered deficient are checked once a year or more frequently depending on the bridge's "criticality" or the volume of traffic it transports.

"As a bridge falls lower on the ranking they are inspected more and the planning process for construction and the search for funding begins," Lindsey said.

Lindsey said the bridges in Utah that are considered deficient typically have a lot of life left in them and can be maintained with preservation funds that are specifically earmarked for situations where immediate repairs are necessary.

In the 2009 building season UDOT will be constructing new structures or replacing components at sites around the state. There will be full bridge replacements at both Riverdale Road over I-15 at the interchange and U.S. 191 over the Colorado River. Four bridges on I-15 between Spanish Fork and Santaquin will have the decks replaced and partial depth panels installed.

The current rate of bridge construction for the department is 15 bridges a year, Carlos Braceras, deputy director for UDOT, told the interim committee Wednesday.

From now through August UDOT will be replacing bridges along I-80 between 1300 East and State Street with rapid bridge technologies that reduce traffic congestion and save time and money, officials say. The construction methods allow crews to develop the supporting structures at the base of the bridge before they launch the deck into place. John Montoya, project manager for the site, predicted that these methods shaved more than a year off the overall project had it been built using traditional techniques.

Other bridge replacements this summer at Lambs Canyon, Mountain Dell and I-215 and 3300 South this August will use rapid bridge building methods.

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E-mail: cnorlen@desnews.com