Abstract: On April 18, 1996, Employee #1, was replacing wooden ground support cribbing in the top left rib of a heading tunnel drive operation. On a previous excavation it had been noted that the cribbing, which had been installed behind the steel set ground support to help prevent rockfalls, was loose. When the crew re-entered the tunnel, the superintendent noticed a location in the left rib that was supporting a 250 to 300 lb rock at shoulder level, and which needed better support. He directed Employee #1 to replace or repair it, and then he and the rest of the crew turned away to continue toward the tunnel heading. As they moved away, they heard Employee #1 cry out, and on turning back they saw him down on the invert, with both the cribbing and the large rock down next to him. Employee #1 sustained blunt trauma to the head, neck, and right shoulder. The crew rendered first aid, and the medical technician employed at the site was immediately summoned. There were no witnesses to the accident. Employee #1 was a recent hire, with an undetermined amount of experience.