Abstract: At approximately 9:30 a.m. on June 25, 2009, Employee #1 and two coworkers were working at a site on a college campus in Los Angeles, CA. Employee #1 and a coworker were completing an assignment within an underground electrical vault at this site. Employee #1 and the coworker had clearance to enter the vault and splice a cable. Employee #1 came to the site and blocked off the work area with cones. After a tailboard meeting with the crew, Employee #1 had air forced into the vault and the inside atmosphere of the vault checked, which was found to be at acceptable levels. Employee #1 then donned on personal protective equipment and a fire suit. He and a coworker descended approximately 20 ft into the vault, where they cleaned and pumped water out of the vault. They used a Tic Tracer, which was an audio signaling sensor device, to examine the cable and recorded no sound. They also tested the cable with an amp meter and obtained a zero amp reading. Using the Tic Tracer on another cable, they obtained a good signal. While standing from a ladder, Employee #1 opened the cable's exterior lead shield, and obtained a faint response on the amp meter, but it was deemed too faint to be positive. However, when using the Tic Tracer, he received a no positive reading. He then cut into the cable more. When he did this, the line shorted to ground, causing a flash fire. Employee #1 fell off the ladder injuring his back. He sustained severe burns on face, neck and arms, and hearing loss. Employee #1 was transported to a medical center, where he underwent treatment and surgery, and was hospitalized.