Lowering a 7,000-ton tunnel-boring machine piece by piece into an 80-ft-deep launch pit sloped 3° forced Barnhart Crane and Rigging to think outside the boom. The subcontractor working at the Alaskan Way Viaduct in Seattle opted to use a modular lift tower instead of a conventional crawler crane, saving millions of dollars and valuable site space.
The largest tunneling machine built for North America, Bertha—a 57.5-ft-dia unit—will this summer bore a 1.7-mile-long tunnel to replace the aging Alaskan Way Viaduct. Barnhart performed intricate engineering under its $6-million contract to deliver the TBM, says Matt Brennan, vice president of branch operations for the Memphis-based company.