Abstract: An electrical instrument technician for the Weyerhaeuser Company in Longview, WA, was investigating an incident in which an employee of another company had received an electric shock while cleaning a large fuel oil storage tank at the Weyerhaeuser site. To facilitate the cleaning of the tank, the technician had installed a temporary power supply at the tank the day before the incident. This temporary power system utilized a 240/120-volt transformer and spider box fed from a 575-volt high-resistance ground system. The spider box was connected to the branch circuit wiring by a pigtail and a large metal cap welding plug. When the technician tested for voltage between the spider box and ground using a voltmeter, the reading indicated leakage in the system; the box was hot. Employee #1 then disconnected power to the box by unplugging the welding plug. When he broke the welding plug connection, he was electrocuted. An investigation determined that the temporary power system had been wired incorrectly, as one of the power conductors had been spliced directly to the ground conductor.