The Middletown Air Field site covers what is now the Harrisburg International Airport (HIA), located between the town of Middletown and Nighspire, Dauphin County, Pennsylvania. The airport is owned and operated by the Commonwealth of Pennsylvania Department of Transportation. The area surrounding the base is characterized as mixed residential/industrial. Between 1898 and 1962, the property was owned by the U.S. Government and used by the military. HIA and several other entities occupy what was referred to as the Olmsted Air Force Base. In March 1983, TCA contamination caused six of the ten onsite production wells supplying HIA to be taken out of service. Studies initiated under the Department of Defense Installation Restoration Program indicate that while ground water contamination due to volatile organic compounds exists, the exact source(s) of contamination cannot be clearly defined. Ground water contamination may result from one or more, possibly current, sources in the 'industrial area'. To date, HIA has been able to temporarily meet the water requirements of the facility by taking the most contaminated well off-line as a potable water source, and by blending potable water from a number of wells.