Engineering feat makes swapping out bridges on I-15 a snap Slide method — ‘kind of an art’ — makes its Nevada debut in Mesquite

Julie Duewel, NDOT photographer

New I-15 bridge slides into place KSNV coverage of a section of Interstate 15 in Mesquite getting replacement bridges through a new method of transportation engineering, Jan. 10, 2012.

Two bridges on Interstate 15 in Mesquite were replaced Tuesday night within a couple of hours using hydraulic jacks, metal beams and Dawn dish soap in a process called accelerated bridge construction.

Engineers from around the U.S. joined the Nevada Department of Transportation and its partners to see the bridge slide.

“This is the first one Nevada’s done,” said Marty Strganac, the department’s resident engineer.

The bridge slide is part of the I-15 West Mesquite Interchange Project, an undertaking that will cost more than $14 million to improve connectivity on the interstate.

Traditional bridge construction could take well over a year, said Dallas Hammit, deputy state engineer for Arizona, who was at the construction site Tuesday to see his first live bridge slide.

Accelerated bridge construction uses new technology to cut down the time it takes to replace an old bridge, Strganac said. In Mesquite, new bridges were built on temporary platforms right next to the old I-15 bridges that were demolished.

“It’s kind of a perfect situation,” said Strganac, adding that there was enough space next to each existing bridge to build replacements and the interstate wasn’t shut down during the project.

Traffic moving in both directions was rerouted through on- and offramps during the bridge replacement, said Strganac, adding that motorists are expected to be able to travel on the new bridges by Thursday morning.

Travelers aren’t expected to notice much of a difference, Strganac said, as the replacement bridges — each with two lanes — look similar to the old bridges.

There are no engineering guides to bridge slides, Strganac said. “It’s kind of an art at this point.”

Hydraulic jacks were used to lift the new bridges up and ease them on Teflon rails lubricated with dish soap, Strganac said.

Each bridge slides about 5 feet at a time, Strganac said. Construction personnel overseeing the project are trained to watch for any problems during the careful procedure.

W.W. Clyde and Horrocks Engineers worked with NDOT, the Southern Nevada Regional Transportation Commission and Mesquite to design and build the bridges.

The design company is based in Utah, where more than six bridge slides have been done, Strganac said.

Engineers like Hammit were there to watch and learn about the new method.

“It’s definitely going to help the local town,” said Hammit, who said that Arizona might use bridge slides in future transportation projects.

The impact on Mesquite will be beneficial, according to NDOT. The agency estimates that residents and commuters will save $12.7 million in time and fuel costs.

Along with the new bridges the project also calls for construction of roundabouts near the highway interchange, improvements to on- and offramps and the widening of Falcon Ridge Parkway to increase access, safety and traffic flow.