EE STATED THAT HE WAS PICKING UP A 5 GALLON BUCKET CONTAINING ALUMINA USED IN THE DUSTINESS TESTING. HE TWISTED TO PUT IT UP AND FELT SOMETHING POP IN HIS LOWER BACK. HE DID NOT REPORT THIS IN CIDENT TO HIS SUPERVISOR UNTIL 8/8/03, WHEN HE LEFT A VOICE MESSAGE. SUPERVISOR RETURNED THE PHONE CALL AT 9:30 A.M., AND EE INFORMED HIM THAT HE WOKE UP SORE & IN PAIN. EE WAS EVALUATED BY H