EE WAS REMOVING OVERSIZED CHUNKS OF CEMENT CLINKER FROM A GRIZZLY SCREEN OVER 708 HOPPER IN THE CLINKER STORAGE BLDG. REMOVING THEM INVOLVED LIFTIN AND TOSSING THEM TO THE GROUND BELOW. WHEN D OING THIS, HE FELT PAIN IN HIS BACK. HE WENT TO DR. LATER THAT DAY AND WAS PUT ON MEDS AND THERAPY, AFTER WHICH HE WAS RELEASED TO FULL DUTY ON 5-25-00.