Abstract: On November 20, 1991, Employee #1 backed a loaded concrete mixer truck, containing 9 yards of concrete weighing about 62,000 lb, into a 15 ft wide access area between the edge of a 7 ft deep excavation and its 10 to 15 ft high spoil pile. He was preparing to pour concrete into the formwork of a house foundation that was installed in the excavation. The soil was type D (granular-gravel-sand). The sides around the perimeter of the formwork were almost vertical and were not supported in any manner. Employee #1 positioned the mixer about 3 to 4 ft from the edge of the excavation to allow for the concrete chute to reach the formwork. Before he had a chance to dismount from the mixer, the ground under the mixer caved in, causing the mixer to fall into the excavation and overturn. Employee #1 was hospitalized. The employer did not provide specific instructions in hazard recognition regarding the working environment for off-highway work sites.