Caltrans has halted work on a $25-million I-5 bridge-replacement project, north of Redding, as it looks for the cause of a 1.5-in. lateral movement of the unfinished structure’s 400-ft-long arch. Surveys late last year verified the arch’s movement, first reported by employees of Benicia, Calif.-based contractor Golden State Bridge, according to Caltrans. The agency also confirmed that the bridge, which was about 65% complete when work stopped on Jan. 5, had also settled vertically by 2 in., as expected. Gudmund Setberg, Caltrans supervising bridge engineer, says the agency is conducting a design review “to assess deflections measured during construction.” Setberg adds that the delay is not expected to significantly affect the project’s schedule, which calls for completion later this year. Known as the Sidehill Bridge, the new 810-ft-long bridge replaces a 1950s-era structure that spans a 140-ft-deep ravine and a railroad tunnel. Golden State Bridge will receive compensation for equipment and materials idled during the work stoppage.