track of the Tornado by a maintenance worker was responsible for injuring Mackenzie Jennings, an 11-year-old girl. The board hit the girl in the head and knocked her unconscious. She underwent surgery at Mercy Medical Center in Des Moines to remove a blood clot and reduce swelling in her head. State inspectors who later inspected the ride themselves discovered the board had not come from the Tornado itself and allowed the ride to re-open. Two others were also injured in this incident. References Roller coasters introduced in 1978 Roller coasters in Iowa