Abstract: At 8:10 a.m. on June 29, 1994, Employee #1, a plumber's helper on his first day on the job, was constructing a work platform for the plumber he was assisting. He placed an aluminum walkboard (pickboard) measuring 12 1/2 inches wide by 20 feet long, onto three 4 inch angles. The supports were welded to the perimeter walls of an uncovered tertiary clarifier tank and to a filter trough in the tank's upper portion. The walkboard was 22 inches away from the tank's perimeter wall. The clarifier tank has a 25 foot sidewall depth: 12 1/2 feet above the ground, and 12 1/2 feet below the ground, and a diameter of 48 feet. When Employee #1 had finished placing the walkboard/scaffold, he stood on the east end and called to the plumber to come view his work. The plumber, who was approximately 75 feet from Employee #1, told him that the walkboard's position was O.K. Employee #1 then appeared to step back off the walkboard. He fell 60 inches to a steel baffle that protruded 70 inches into the tank from the perimeter wall and was sloped at a 45 degree angle. He then fell an additional 10 feet 8 inches, flipping over in the process and landing headfirst on the tank's concrete floor. He suffered a fractured skull and brain damage. Employee #1 was wearing an approved safety belt with a 4 foot lanyard attachment; however, the lanyard was not tied-off on the opposite end. This was Employee #1's first day with this employer; he had been working on this project for 7 months with another employer. Employee #1 had attended numerous safety meetings in which safety belts and their use were a topic. His safety belt had been inspected on April 22, 1994, by the on site safety officer and carpenter foreman of his former employer. A brief safety orientation had been performed by the superintendent of Employee #1's new employer on the morning of the accident, prior to Employee #1's beginning work.