Abstract: A power line crew was working on a project to convert an overhead power line running along a street to an underground power line. The 4000-volt conductors had recently been installed in underground vaults and had been energized two weeks earlier. Two of the crew members had been assigned the completion of the installation of a deenergized 12-kilovolt circuit. Although the employees' and foreman's post-incident versions of the assignment varied, the employees were apparently reminded that the 4000-volt circuit, which shared the same vaults as the 12-kilovolt circuit, was energized. When he entered a vault wearing Nomex coveralls, a hard hat, and work boots (but without wearing safety glasses or rubber insulating gloves), one of the power line workers noticed that the tap plug reducers on the 4000-volt conductors still had their shipping covers in place. The utility company's policy calls for safe-ended elbows to be installed on the conductors before the circuit is energized. Apparently, seeing the 4000-volt conductors in an incomplete state of installation made the employee, who had been a power line worker for 6 years (including a 3-year apprenticeship), forget that the circuit was energized. He then started to complete the installation properly. Cleaning out the reducer's female contact with a rag containing degreaser, the employee caused an electrical fault. As a result of the ensuing electric arc, the employee sustained first-, second-, and third-degree burns to his face and hands. He was hospitalized for his injuries for 8 days. (His coworker had been at street level, acting as an attendant, when the accident occurred.)