Abstract: Employee #1, a journeyman plumber for JWP Mechanical Services, and two apprentice plumbers were installing a 4 in. drain line in a 7 1/2 ft deep trench. The employees had installed the shoring for the trench. The shoring included 3/4 in. plywood and 2 in. by 6 in. whalers and hydraulic aluminum shores. When the work was completed, Employee #1 and the two apprentices began to dismantle the shores and remove the plywood and whalers. They found, however, that they could not remove the whole system from above because the whalers were nailed to the plywood, and the plywood was now partially buried. Employee #1 entered the trench and started pulling nails out of the plywood and whalers. While he was in the trench, the east wall collapsed, partly because of the weight of another drain line (two 10 ft sections of cast iron 12 in. line were found in the hole). Employee #1 was pinned for more than an hour. He suffered a broken shoulder.