EE STARTED HIS SHIFT ON AN L85 ROCK TRUCK AT 0600. LATER IN THE SHIFT HE STATED THAT HIS SEAT WAS LOOSE CAUSING HIS BACK TO HURT. A NEW SEAT WAS ORDERED. AT 1000HE PARKED THE ROCK TRUCK, STATE D HIS BACK WAS HURTING AND WENT HOME. HE HAD NOT RETURNED TO WORK.