An employee was working at a treatment facility construction site. A flatbed had transported a single platform about 1 mile to the site. The platform was strapped onto the flatbed and had wood blocks to keep it from moving. During the transport, one of the pieces of wood vibrated out of position. When the employee released the ratcheted straps, the tubular steel frame platform toppled over and off the flatbed. The platform struck and broke his left leg. He was hospitalized and had surgery.