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• P*s Engineering Science, Inc. <br /> present in the subsurface due to possible past leakage from the sewer line. The cohesionless <br /> layers (e.g. sands and silts) appear to be somewhat discontinuous in the western half of the <br /> site. However, there is insufficient information on the soil stratigraphy to confirm continuity <br /> of such layers in the northeast corner of the site below a depth of about 65 feet and in the off- <br /> site area. <br /> Drilling logs for several borings (B-108) and wells (MW-4 and MW-5) extend only to the <br /> depth range of 56 to 64 feet. The instrumentation log from P-6 provides the only <br /> stratigraphic information below a depth of 65 feet in the northeast corner; it extends to a <br /> depth of 110 feet. A piezocone log was not obtained at P-7 and P-8. <br /> Contaminant Concentrations of Concern. State of California Maximum Contaminant Limits <br /> (MCLs) have been adopted as the contaminant concentrations of concern for the project. The <br /> MCLs for 1,1-DCE and TCE are 6 µg/L and 5 pg/L, respectively. Near the northeast <br /> property boundary, concentrations of 1,l-DCE range from ND to 2.5 µg/L and detections of <br /> TCE range from 9 to 12 µg/L. <br /> 0997\09072\wks2add 12-18-97 2-3 <br />