Abstract: During a plant shutdown, subcontractors were working on a pipeline that was beneath a 25 ft high work platform. The subcontractors worked all day, but when they left they did not replace a 2 ft by 4 ft section of floor grating on the platform because they thought a coworker would make a final inspection of the job. The coworker did make a visual close-out inspection, but no one climbed onto the section of the platform where the grate had been left open. It remained open for two days. At 2:00 a.m. on August 24, 1990, Employee #1 fell through the grate opening and severely tore the ligaments in his right knee.