The smoother, safer path afforded by the three-mile truck climbing lane and wider shoulders belies the unexpected challenges encountered during the three-year construction process. While crews drilled into the slope walls and cut them back to make room for improvements, they unknowingly exposed an embankment holding back an old slope failure caused by the Gillis Hill Fault, long thought to be inactive. The drilling caused a large piece of slope to crack and break off in the middle of the night, releasing more than 60,000 cu yd of rock and dirt onto the eastbound shoulder of I-80. 

The team flattened the slope in the fault zone area. To stabilize the cut slope and prevent future landslides, crews installed a 300-ft-long retaining wall that was subsequently replaced with a more durable structure. For a retaining wall at another location, the team used a cost-saving chain-link rock fence, reinforced with K-Rail and vertical steel tubing.