Abstract: At 1:30 p.m. on March 15, 1990, Employees #1 and #2 were laying pipe in a shallow trench. A coworker adjacent to the two men had marked a hole on the concrete floor for a baseplate for a 1/4 in. thick, 11 ft 4 in. tall, 4 by 4 in. square metal support column. The coworker slid back the baseplate so that he could drill the holes for mounting bolts. While the bolts were curing in the concrete, the column remained free-standing. After the coworker left the area the column fell, striking Employee #1 on the head and Employee #2 on his left wrist before it came to rest on a concrete retaining wall. Employee #1 suffered a concussion and was hospitalized; Employee #2 sustained multiple bruises and contusions to his wrist. Coworkers interviewed had different opinions on why the column fell. One employee said it was blown over by the wind and another indicated that it fell moments after a coworker passed by it.