EE STATED HE WAS WORKING ON 1C PONY HEADER IN THE PROCESS OF TIGHTENING THE JACK PIPE. A PIECE OF ROCK FELL OUT OF THE TOP HITTING HIM ON THE BACK. HE SHOOK THE ROCK OFF HIS BACK & THAT CAUSED THE ROCK TO FALL HITTING HIS RIGHT FOOT AGAINST THE WATER LINE PIPE. IT WAS A ZINC WATER LINE. ROCK WAS 3 FT X 3 FT X 3 1/2 INCHES.