A MAINTENANCE MECHANIC REPORTED ON 8-30-02 THAT WHILE ON SWING SHIFT HE HAD BEEN FREEING A POSITIVE DISPLACEMENT PUMP BY USING A 48"" PIPE WRENCH, THE EE STATED THAT HE HAD NOT NOTICED ANY BACK PAIN DURING SHIFT, HOWEVER THE FOLLOWING MORNING HE COMPLAINED OF LOWER BACK PAIN. THE EE WAS SEEN BY A PHYUSICIAN AND RELEASED, HE LATTER RECEIVED MEDICAL TREATMENT ON 10-2-02 BUT CONTINUED