WHILE CENTER BOLTING IN 3 STRAIGHT OVERDRIVE JUST INBY 9 X-CUT IN E-10, EE WAS PREPARING TO PUT BOLT IN HOLE & IT JAMMED. HE PULLED IT OUT TO REINSERT AND WHEN IT CAME FREE HE SLIPPED & FELL STRIKING HIS LEFT HIP & TAILBONE. THE INJURY WAS DIAGNOSED AS A CONTUSION & AFTER SEEING A SURGEON THE DIAGNOSIS OF THE INJURY WAS CHANGED TO A HERNIATED DISC & 3 BULGING DISKS.