Abstract: At 11:30 a.m. on December 19, 1994, Employee #1, of Western Summit Constructors, Inc., was cleaning the base of the vertical north wall (I-line wall) rebar mat on the ground floor in preparation for the installation of a wall panel form. The 3 ft by 3 ft opening in the ground floor was located at a junction of the west wall and north wall, and was covered with plywood sheeting approximately 7/8 in. by 4 ft by 4 ft 6 in. The cover was not secured in place to prevent accidental removal and displacement, and markings on the cover were of faded, weathered, unreadable reddish paint. The ground floor opening was located over a dry pit 37 ft below the ground floor. Block cut form for the 3 ft by 3 ft ground floor opening had been removed. The bottom portion of the ground floor form had also been removed. This in effect now resulted in a through opening. During cleaning, Employee #1 raised or moved the plywood cover, for unknown reasons. Assuming that the bottom portion of the floor form was still in place, or forgetting that the floor had been removed, Employee #1 apparently stepped forward into the 2 ft by 3 ft opening and fell through 37 ft to the floor of the dry pit. Employee #1 sustained severe trauma to his left arm and hip. He was removed to Valley Medical Center for treatment and admission.