Abstract: Employee #1, a tunnel crew foreman, elected to install a float pin in the left arch of the concrete form used to place poured-in-place concrete in a full circle concrete lined tunnel bore. He was working from the projecting carrier beam (needle beam) of the concrete form carrier. In order to place the float pin, he was working with arms fully extended and leaning slightly forward. He was not wearing a safety belt, lanyard, or body harness. The tunnel lights failed for one to five minutes. During the period of darkness, Employee #1 lost his balance and fell 10 feet to the form carrier trackway rail and then another 2 feet to the invert below the rail. He was hospitalized with a broken leg. The rail is supported by cross beams and the configuration creates openings through to the form invert. The total fall distance was approximately 12 feet.