Abstract: Employees #1 and #2 were using hand shovels to grade the bottom of a trench that was 10 to 11 ft deep and 42 in. wide at the bottom. The sides of the trench were straight to the 5 ft level and sloped 1:1 above the 5 ft level. The spoils pile was set back 4 to 5 ft. A 1 ft wide by 6 to 8 ft long section of the trench wall fell 1 ft 6 in. to 4 ft from the top. Employee #1's ankles were injured and required surgery. Employee #2 suffered no injuries. At 1:30 p.m. on March 1, 1988, before inspection, the trench was filled and the sewer line completed. According to management and employee interviews, the soil was average. After the accident, a layer of magnesium was found at the site of the cave-in.