This new pedestrian and bicycle underpass tunnel was jacked under the Union Pacific Railroad mainline tracks. Drill Tech built the concrete box for jack and bore operations, as well as multiple retaining walls. The team used ground freezing to stabilize the mixture of sand and boulders that had been used to backfill an old timber trestle. Drill Tech conducted continuous monitoring surveys during the tunneling and grouting operations.  There was no significant movement of the UPRR track at any point during construction. The rail line remained operational for the duration of the project. The team coordinated with UPRR staff and collaborated with Caltrans and the Federal Highway Administration, as the site required extensive traffic control measures with one lane of traffic always open during construction. Additional features included a bus turnout and transit shelter, new hiking trail, construction of an infiltration basin, and miscellaneous drainage improvements. The project also entailed the relocation of a traffic signal.