INJURED WAS DISMOUNTING FROM NW#2 BELT. HE HAD PLACED HIS LT. FOOT ON A TOP CONVEYOR RAIL WHILE HOLDING ONTO A STRUCTURE SUPPORT CHAIN. AS HE BEGAN TO STEP DOWN WITH HIS RT. FOOT, HIS LT. FOOT SLIPPED OFF THE RAIL & IN BETWEEN BELT & STRUCTURE, CAUSING HIM TO FALL. THE AREA WAS WET.