THE EE WAS CARRYING A LARGE WRENCH TO THE DRILL WHEN HE STEPPED IN A DEPRESSION CAUSING HIM TO LOSE HIS BALANCE. HE TWISTED TO DROP THE WRENCH AND CLEAR HIS FEET CAUSING A STRAIN OF HIS GROIN AND CHEST WALL AREA. HE CONTINUED WORKING UNTIL ASKING TO GO TO THE DR ON 10-1-03. AT THIS TIME HE WAS PLACED ON RESTRICTIVE DUTY AND RETURNED TO WORK.