Installation Restoration Program. Phase II - Confirmation/Quantification. Stage 1 for American Lake Garden Tract, Washington

摘要

An IRP Phase II (Stage 1) Confirmation/Quantification Investigation was performed in the American Lake Garden Tract residential community as a consequence of previously confirmed groundwater contamination by like compounds both in the Garden Tract and on McChord AFB. A similar type of groundwater problem was believed to exist at the opposite end of the residential area, and may possibly be related to Army operations on Fort Lewis. The field study was designed to identify the type, quantity, and extent of groundwater contamination by expanding the study area to include all of the Garden tract, the entire west half of McChord AFB, and the northern one-third of the Fort Lewis Logistics Center. Field investigations consisted of 58,000 lineal feet of self-potential and 24,000 lineal feet of seismic refraction surveys. Forty electrical resistance stations were established. Twenty-six two-inch diameter monitoring wells were constructed. More than 225 water samples from more than 60 EPA, Army, and Air Force monitoring wells, plus domestic water supply wells were characterized for volatile organic chemicals. All wells were sounded at least weekly for static water levels, and in-situ hydrochemical properties were monitored. Study results confirm independent sources of chlorinated hydrocarbon contamination exist on each military facility, and that these contaminants are migrating into different parts of the American Lake Garden Tract.