Workers were breaking up concrete to install gas lines and were placing the concrete chunks on a flatbed truck. The injured employee was operating a backhoe. The flatbed operator tilted the bed of the flatbed truck slightly to make it easy to move concrete into the bucket of the backhoe. The injured employee then climbed up onto the tilted flatbed and began moving the smaller pieces of concrete into the bucket of the backhoe by hand when a large piece of concrete slid and pinned his ankle between the bucket of the backhoe and that large piece of concrete. His ankle was crushed.