Abstract: Employees #1, #2, and #3 were standing on top of three 71 foot pre-stressed concrete double T roof slabs that had been installed over an auditorium area. As they were preparing to weld the fourth 71 foot to the first three, the L-shaped ledger beam on top of the columns at the south end rolled inward, due to off center loading. The original three double Ts fell 24 feet to ground level. All three employees rode the slab down. Employee #1 suffered lacerations of the knee and cartilage. Employee #2 suffered a puncture wound in the back from rebar. Employee #3 suffered severe lacerations of the arm. The installation of the fourth double T did not cause the first three to fall, as it rested on different ledgers and columns.