The Arizona Department of Health Services was asked by the Arizona Department of Environmental Quality to evaluate the potential health effects from inhalation of toxic vapors as a result of an unplanned, concentrated nitric acid release. According to Hudson Farms, at approximately 1 pm on July 1st, concentrated nitric acid began escaping from a small leak in a 33,000 gallon storage tank. By 4:30 pm, the first responding fire department units observed an orange colored plume that was moving with the wind direction. The large plume continued to dissipate throughout the area until about 8:30 pm that night. Small amounts of nitric acid that was generally restricted to the Hudson property continued to leak until approximately 8 am the morning of July 2nd when pumping of acid waste waters into emergency storage tanks was completed. It is estimated by ADEQ that a total of 4,0 00-4,500 gallons of concentrated nitric acid was released from the storage tank. Approximately 600 people from the town of Laveen and the Gila River Indian Community were immediately evacuated. Residents were allowed re -entry to their homes the following day, July 2nd at approximately 10 am.