EE WAS CHANGING OUT A PUMP SHELL AT #2 MATRIX BOOSTER PUMP WHEN HE SLIPPED ON THE PUMP SHELL AND FELL. AT THAT TIME HE ONLY EXPERIENCED MINOR PAIN IN HIS LOWER BACK AND REFUSED MEDICAL TREATME NT. ON 9/30/02 HE REPORTED TO THE NURSE COMPLAINING OF SEVERE LOWER BACK PAIN AND WAS REFERED TO A DOCTOR.