EMPLOYEE HAD LOWERED ATRS ON SINGLE BOOM BOLTER IN PREPARATION TO MOVE IT. HE REALIZED HE HAD LEFT THE DRILL STEEL IN THE CHUCK OF THE DRILL. HE DUCKED UNDER LOWERED ATRS PAD TO REMOVE STEEL . AS HE STEPPED AWAY HE STOOD UP AND HIT HIS HEAD ON ATRS. THE MACHINE WAS NOT OPERATING. HE WORKED UNTIL 6-4-01 WHEN HE WENT OFF WORK.