EMPLOYEE WAS INSTALLING SPILL CONTAINMENT SKIRTSON 2 WEST DUMP. THE DRIVE 2ND BELT WAS TAGGED & LOCKED OUT. OTHER EMPLOYEES WERE WORKING ON THE OTHER END OF THE BELT & THEY RELEASED THE PRESSU RE ON THE BELT TAKEUP. THE INJURED EMPLOYEE WAS ON THE BELT WORKING ON THE SKIRT WHEN THE BELT TAKEUP WAS RELEASED. WHEN THE BELT MOVED A FEW FEET IT CAUSED HIM TO HURT HIS BACK.