EMPLOYEE WAS USING A PIPE ATTACHED TO AN AIR HOSE TO BLOW LOOSE MATERIAL OFF AN AREA THAT HAD BEEN DRILLED, IT WAS ON A SLIGHT GRADE. AS HE TOOK A STEP FORWARD HIS FOOT CAME DOWN ON A PIECE OF STONE ABOUT THE SIZE OF A FOOT, HIS FOOT TWISTED AS HIS WEIGHT CAME DOWN ON IT, HE CONTINUED TO WORK UNTIL NOON THENM WENT TO THE DOCTOR, HE HAD SPRAINED AN ANKLE.