Abstract: Employee #1 was using a Caterpillar 6-wheel dump truck to haul excavated material to a dump site on the next level up a mountain. It appeared that the operator backed his vehicle into place, dumped his load, and was lowering his bed when the soft surface of previously dumped material gave way. His wheels sank, causing his truck to roll backward down the 125 ft long, approximately 60 degree slope. The truck struck range boulders that had been dumped near the bottom of the slope, rolled over three or four times, and continued another 20 to 25 ft into some trees. Employee #1 was thrown out of the cab and onto the boulders. He was killed. The articulated cab was turned 180 degrees and the bed and wheel jacks were in an upright, operating position.