Abstract: On December 20, 2007, a two-person crew was assigned by the crew chief, Employer #1, to mark the final surface elevation on a luxury condominium building under construction. The building consists of four stories of condominiums erected over a two-story underground parking garage. The surface openings of approximately eight ventilation shafts for the below-ground parking garage are located around the perimeter of the building. The ventilation shafts are concrete-lined, 22 ft deep and have surface opening dimensions of 16 ft by 3 ft. On the day that the surveying crew was on site, the shaft opening grate covers had not been installed, and the openings were protected by 0.75-in. plywood cut to fit the opening and supported by braces laid across a metal L-bracket lining the shaft opening. The surveyor crew was marking the final planned grade on the side of the building when Employee #1 stepped onto the plywood cover of one of the ventilation shafts, apparently intending to walk to the west side of the shaft. The plywood shifted and Employee #1 fell 22 ft, with the plywood, to the bottom of the concrete shaft. Employee #1 suffered a broken left leg and broken right ankle and was taken by emergency medical personnel to a local hospital trauma unit, where he was admitted for his injuries.