Abstract: Employees in Oshkosh, WI, mistakenly began the delivery of a truckload of liquid hydrochloric acid into a nitric acid bulk storage tank earlier in the day. The employees discovered the error at the beginning of the fill cycle and corrected the mistake, but had already delivered about 1000 gal. Approximately two hours later, noxious fumes became noticeable from the tank vent and scrubber. An emergency response from the in-plant HAZMAT team began shortly following this discovery. Soon after, the wall of the tank began to fail and the city of Oshkosh HAZMAT responded and evacuated a small area of Oshkosh. The area around the tank is protected by a dike. As a result, neutralization of the acid, together with dilution with water, eventually controlled the fuming problem. No injuries were reported.