AT THE BUNKER TAIL SHAFT AREA, MECHANICS WERE GETTING READY TO TAKE SLACK OUT OF ""B"" CHAIN TO PULL SLACK WHEN A WELD THAT HELD THE TENSION ARM IN PLACE BROKE. THE RELEASED TENSION ARM CAME UP THROUGH THE STEPS WHERE THE VICTIM WAS STANDING CAUSING SEVERE LACERATION TO FEMORAL ARTERY IN HIS GROIN AREA.