EE WAS SPREADING GRAVEL AT THE APPROACHES OF THE SCALES. HE HAD DUMPED THE GRAVEL WITH THE END-LOADER. HE STATED THAT THE END-LOADER BUCKET WAS TO WIDE TO REACH INBETWEEN THE GUARD RAILS AND D RAG ALL THE EXCESS GRAVEL BACK. HE GOT OFF HIS END-LOADER & STARTED TO SHOVEL. HE STATED THAT HIS BACK POPPED WHILE SHOVELING AND NOW HE IS EXPERIENCING PAIN ON BOTH SIDES OF HIS LOWER BACK.