Abstract: At approximately 4:15 p.m. on May 5, 1991, Employees #1 and #2 were replacing a line at the steam well they were relining. They were working from a 16 ft long by 14 in. wide Simpson aluminum scaffold plank that was situated 6 ft over a cellar full of boiling water and mud produced by the well. The scaffold plank was bent and gave way, plunging Employees #1 and #2 into the boiling mud and water mixture. They suffered second- and third-degree burns on their backs, wrists, legs, and ankles. The scaffold plank had earlier been identified as defective by a supervisor, and it had been removed from use. The plank had not been marked as defective, and had been left in the work area leaning against the derrick leg. The previous crew had positioned the defective plank after they tried to straighten the bent section.