WHILE TIGHTENING A SCREEN PANEL IN THE PREP PLANT AND STEPPING OUT OVER DISCHARGE CHUTE, EE STEPPED INTO AN OPENING ALONG THE DISCHARGE CHUTE AND STUMBLED, TWISTING HIS LOWER LEG AND ANKLE. ACCIDENT WAS REPORTED BUT ONLY AS A FIRST AID CASE. PAIN AND SWELLING PERSISTED AND WAS DIAGNOSED AS A FRACTURE ON 7/29/04. EE IS CURRENTLY WORKING WITH RESTRICTIONS.