EE SAID HE HURT HIS BACK LIFTING GRATES FOR HAZE MAG. DID NOT REPORT AT TIME OF INCIDENT. CALLED IN NEXT DAY ADVISED SUPERVISOR, DID NOT FEEL HE NEEDED MEDICAL TREATMENT. MONDAY 3/20 EE CALLED SUPERVISOR AND ADVISED MEDICAL TREATMENT WAS NEEDED. EE HAD PREVIOUS BACK INJURY 10/18/99. THIS WAS A RECURRANCE.