Abstract: At about 8:30 on September 14, 1990, Employee #1, along with two coworkers, was resetting a steel ground support set in a 9 ft by 7 ft diversion tunnel. The set had been installed 3 1/2 in. too low. The crew had previously installed and blocked in a steel set in the open face. Then, according to plan, they loosened the misaligned set, barred down loose rocks, and lifted the set into position using the LDH Wagoner machine. They were then to insert 3 1/2 in. blocks under the set. They had set one block under the set and, while the crew's attention was on the job of placing the second block under the set, some rocks were either dislodged or came loose and struck Employee #1 on the back. He was dragged away from the danger area and given first aid for a gouge wound on his back. He was then removed to Mercy Hospital, where he was confined for 24 hours of observation. He reported back to work on September 18, 1990, for light duty restriction. Attention to the tunnel roof and rib could have provided Employee #1 with an additional margin of safety.