EE WAS USING A 90LB JACKHAMMER TO REMOVE A CHUNK OF MATERIAL FROM THE #2 COOLER WHEN HE FELT PAIN IN HIS LOW BACK. HE WAS SENT TO THE DOCTOR AND CONTINUED TO WORK UNTIL 04/20/03 WHEN THE PAIN BECAME MORE SEVERE AND HE COULD NOT WORK. STARTED LOSING TIME ON 04/20/03.