Abstract: At approximately 10:40 a.m. on June 20, 1991, Employees #1 through #3 were preparing to remove a fiberglass roof from the #T4-B tank at a refinery. Employees #1 and #2 were on the tank roof disconnecting the heavy metal catwalk, while Employee #3 was riding in a self-propelled aerial manbasket, using wooden wedges to break the outer tank roof seal. As they were working, the tank roof collapsed. The roof edge projected outward during the collapse and pinned Employee #3 in the manbasket. It then fell inward, causing Employees #1 and #2 to fall about 45 ft. Employee #1 suffered fatal head injuries, Employee #2 sustained a sprained back, and Employee #3 suffered a bruised abdomen. Ten out of the sixteen bolts on the lower support flange of the inner support compression ring of the fiberglass compression dome were badly corroded and had been cut out, which contributed to the roof collapse.