Because the Gilbertville Bridge is recognized as a national historic landmark, the new structural support had to be installed without harming the existing timber bridge. In order to do so, E.T.& L. Corp. jacked the covered bridge approximately seven feet off of the existing bridge abutment. A carrier beam was then installed under the bridge to slide the new 38" x 88' girders into place. Two 20-ton rollers were attached to the plate girders using beam clamps, which then rolled the girders under the bridge on the carrier beam. Finally, cranes lowered the girders off the trolley and into place. This process was completed six times.