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The soil sampling and field screening procedures described above were conducted in <br /> accordance with accepted standards of care prevalent at this time and were performed <br /> to ensure the acquisition of accurate data. Soil samples selected for chemical <br /> analysis were transported to Zymax and BC Laboratories with the Chain-of-Custody <br /> for the specified analyses. <br /> 4.4 Chemical Analysis <br /> A total of ten cores from the assessmentborings drilled at the former diesel tank site <br /> were selected for chemical analysis for BTEX and TPH(diesel) by Zymax. At the <br /> request of the San Joaquin County PHS/EHD an additional sample was collected at a <br /> depth of 10 feet from below the former waste oil tank. This was submitted to BC <br /> Laboratories for a for Nickel (Ni) and Chromium (Cr) analysis by TTLC Digestion. This <br /> is an analysis for total recoverable metals. If the TTLC concentration was found to <br /> equal or exceed 10 mg/kg (ppm) for Nickel or 5 mgkg for Chromium, the lab was <br /> instructed to perform a Waste Extraction Test (WET). This is also known:as a STLC <br /> (Soluble Threshold Limit Extraction) Extraction, an analysis for total soluble metals. <br /> Prior to running the WET, a pH analysis was required. In the case where pH exceeded <br /> 6, deionized water was to be used to extract Ni and Cr. If the pH was .less..than 6, citric <br /> acid was to be used to perform the extraction. -Laboratory results are provided in <br /> ( Appendix A. <br /> 5.0 Site Characterization Findings <br /> The following sections present the findings of the site assessment phase of this <br /> project. <br /> 5.1 Site Geology and Hydrogeology <br /> Escalon is located along the eastern margin of the Great Valley of California. Recent <br /> alluvial sediments derived from the primarily granitic terrane of the Sierra Nevada f <br /> Range blanket the area in the shallow subsurface. The borings completed at <br /> Derickson Trucking penetrated to a maximum depth of 40 feet. The sedimentary <br /> section encountered was uniform and consisted of a sequence of silty sands and silts <br /> from the surface to approximately 25 feet. These.sands were yellow-brown to reddish <br /> brown in color, generally fine to very fine grained, with intervals of medium to coarse <br /> grained material. A high silt content was characteristic of this unit. At 30 feet, a very <br /> stiff clay and clayey sand was encountered which-was underlain by another silt <br /> interval. Between 37 and 40 feet, a loose, quartzose, medium to very coarse-grained <br /> sand with common pebbles was present. <br /> 6 <br />