Abstract: An employee was cleaning the concrete slabs used as sound barriers along the freeways. He was using a power sprayer. There were five concrete slabs, each were 12.5 ft long, 4 ft 10 in. high, 5 in. wide and weighed 4,000 lb each. The slabs were placed in row perpendicular to the concrete pad and were approximately 4.5 ft apart. Each slab was separated and supported by scheduled 40 iron pipe that was 2.5 in. in diameter. The slabs were supported by two pieces of pipe that were sunk 8 in. into the concrete base and extended 17 to 19 in. out of the concrete. It was not determined what caused the first slab to topple. As the first one fell, it fell into the second, and so on, in a domino effect until all five slabs had fallen over. The employee was struck in the head and face and died as a result of his injuries.