Abstract: On October 28, 1994, Employee #1 was rough grading an 18-acre site, when a cement slab was found. A ripper was brought over to remove the slab, which turned out to be the top of a 6 ft by 6 ft by 8 ft vault with dirt inside. While removing the concrete and dirt from the vault, the ripper forced a hidden/submerged 150 lb cylinder into another object, which punctured the cylinder, causing a release of its contents and a dust cloud. The employee immediately backed the ripper from the area and turned it off. The foreman called the office manager on the adjacent property to notify 911. Employee #1 was taken from the site for further medical evaluation. He was treated, kept in the hospital for observation, and released on October 29, 1994. The gas release was later identified as chlorine gas of an unknown concentration. There was no way to determine the level of exposure.