SITE INFORMATION AND CORRESPONDENCE_1987-1992

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L� y J ` ly LEEDSNILL•HERKENMOFF, INC. c;L a 1 INTRODUCTION r, F<, In 1984, groundwater samples from two municipal supply'woll's'nAar Lincoln Village Center (LVC) were found to contain detectable levels of tetrachloroethene (PCE) and trichloroethene (TCE) . The Regional Water Quality Control Board (RWQCB) conducted an initial investigation and determined that the contamination source could possibly be leakage through joints in the sewer system at Lincoln Village Center. In 1987, Leedshill -Herkenhoff, Inc. (LH) was retained by Lincoln Properties, Ltd. to conduct a hydrogeologic investigation of the soil around the suspected sewer lines and the shallow groundwater. The Phase I investigation included installation and sample collection from four shallow groundwater monitoring wells, and collection and analysis of soil samples beneath suspected leaking sewer laterals. The results of the investigation indicated that the upper water bearing zone did contain dissolved PCE and TCE. Analysis of soil samples from beneath the the sewer laterals also indicated the presence of PCE, as did samples collected from beneath the three dry cleaning establishments at LVC. Water levels at the time of the investigation indicated that the direction of flow in the upper water bearing zone was generally toward the east. to northeast. EXAMINATION OF SUSPECTED SOIL CONTAMINATION Soil Vapor Investigation The soil contamination investigation will initially focus on soil surrounding the sewer laterals which extend from each of the three dry cleaning establish- ments. Sewer lines serving each dry cleaner and the lines containing the combined flows will be investigated. Each of these laterals within LVC will be investigated using soil vapor techniques, to provide insight as to the presence or absence of PCE soil contamination and its lateral extent, if any. This soil vapor survey will involve the collection of a series of air (soil vapor) samples from various locations (both horizontally and vertically) within LVC property. This technique involves driving a thin steel rod into the soil at the selected sampling location to a predetermined depth. A vacuum pump is then attached to the top of the rod and operated until the hole is purged and a sample is collected. The soil vapor sample is then run through a field-operated gas chromatograph to determine the PCE concentration in the collected vapor sample. Based on these field data, a contour map of detected PCE soil vapor concentra- tions will be prepared.