Trichloroethylene in the ground-water supply of Pease Air Force Base, Portsmouth, New Hampshire

Abstract

TCE (trichloroethylene) in concentrations that may be hazardous to health occurs in the water of an ice-contact largely sand and gravel aquifer (called the main aquifer) underlying much of the PAFB (Pease Air Force Base). In 1977 and 1978, the highest TCE concentration was found surrounding the most productive well, Haven well. Large quantities of TCE were used for degreasing between 1955 and 1965 and, so far as is known, TCE was used extensively up until 1973. Data on how, where, and when TCE got into the aquifer are lacking, but geochemical evidence and TCE analyses show a strong relation between the high TCE concentrations near Haven well and the extensive storm-drain system that underlies the parking apron and runway. The drains help recycle some of the TCE-contaminated ground water from the Haven well area. Sources of TCE-free ground water on PAFB may exist in the northern parts and do exist in the southern parts of the main aquifer; however, in the southern part, either the ground water is probably already being used nearly to capacity (Smith and Harrison production wells) or further development might adversely affect off-base ground-water use. In the northern part, available subsurface data indicate that only relatively small yields are likely at any one site; thus, to get sustained yields comparable to that of the Haven well would probably require an unreasonable number of wells. This study locates TCE contamination in the main PAFB aquifer and discusses three possible water-use alternatives: (I) Abandonment of Haven well, (2) treatment of Haven well water to remove TCE, and (3) treatment of a portion of Haven well water for domestic consumption and use of the remainder for nondomestic uses. Continued use of the Haven well, with treatment of all or part of its yield for TCE removal, is advantageous, both because the Haven well is a high-yield source of water and because cessation of pumping from it might allow TCE-contaminated ground water to move downgradient (southward), endangering the Smith and Harrison production wells. Continued study and monitoring of the TCE contamination would help in predicting when the contamination problem will no longer be threatening.