The west tunnel was the most difficult of the three tunnels to excavate . It was excavated using a tunnel boring machine ( TBM ) that took over four years to bore its way through the mountain . The TBM was launched from the Waterman Portal and tunneled in a westerly direction toward the Devil Canyon portal at a slight uphill gradient of approximately 2 inches per 100 linear feet ( 0.17 % ) . Crews faced many challenges during the excavation , including the 2003 Old Fire that destroyed construction equipment at the Waterman Portal and halted tunneling for ten days . Later that year , a flash flood engulfed the Waterman Portal site and submerged the TBM . It took four months to restore operations in the aftermath of the flooding
Old Fire
Old Fire
Inland Feeder