Abstract: At approximately 3:59 p.m. on December 6, 2006, Employee #1 and a coworker were working on a demolition project. The lower street level floors were being demolished, while the top floor was still being used by the building occupants. The upper level was being accessed by temporary stairway built from the sidewalk. The existing stairway, built of slabs of concrete/stone aggregate, was supported by a wooden substructure, which was found to be rotted and unsafe. Those stairs were removed and put in storage to be replaced after the construction of a new substructure. The upper story landing was left in place, an approximately 4-ft by 5-ft by 3.5-in. concrete/terrazzo slab, which was supported by a framing which was also found to be rotted. The employee and the coworker climbed onto the platform to start work. Suddenly the slab slid free and came down, striking the coworker in the leg, gut, and pelvis. The employee was pinned. Emergency services were summoned, and after extricating Employee #1 from under the slab, the two employees were transported to the San Francisco General Hospital. Employee #1 was hospitalized in critical condition for many days, with major internal injuries and other serious trauma.