4.2 km x 5.7 m-diameter hardrock TBM drive by Frontier-Kemper Constructors for Asarco to replace existing 25-year old drill/blast, circular concrete lined, horseshoe-shaped drive at its Ray Complex southeast of Phoenix. Will be lined at 5 m-diameter. Alignment is on 255 m radius curve at 1.4 % downgrade and rock cover varies from 43 m to 342 m. Sept 1999.
