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Earthgrains Bakery 02320 0106 2.2 SOIL SAMPLING February 3, 1992 Page 2 Soil samples were collected on November 25 and 26, 1991 along the bottom length of the drainage ditch and in a grid pattern in the field to the north of the ditch in areas of apparent surface staining (Figure 3, Appendix A). Soil samples were collected at depths varying from 6 inches to 4 feet. Samples were collected using an impact coring device lined with 1.5 -inch -diameter by 6 -inch -long brass tubes. After each sample was obtained the ends of the brass tubes were covered with foil and plastic end caps. The caps were then sealed with duct tape, labeled with the date and sampling location, and stored on Ice in an insulated container. Soil samples were analyzed for TPH immediately in an onsite, state -certified, mobile laboratory using U.S. Environmental Protection Agency (EPA) method 418.1. One sample (5F) was also analyzed for total oil & grease (TOG) by EPA method 413.2. The samples collected for background metals were placed on ice in an insulated container and transported under chain -of -custody manifest to GTEL Environmental Laboratories, a California -certified laboratory in Concord, California. These samples were analyzed for selected metals including cadmium, chromium, lead, nickel, and zinc using EPA method 6010. Laboratory analyses results for TPH and background metals are summarized in Tables 1 and 2 (Appendix B), respectively. Laboratory reports and chain -of -custody manifests are included in Appendix C. 2.3 RESULTS OF SOIL SAMPLING Laboratory analyses for the 30 soil samples collected as part of the preliminary TPN investigation indicated that only three samples contained TPH concentrations greater than 100 ppm. The total soil volume impacted by TPH concentrations greater than 100 ppm is minimal and appears to have been defined in the, areas investigated during the preliminary assessment. Ditch Area TPH was detected at three of the nine locations sampled along the bottom of the ditch. Sample 1 FX (Figure 3) collected from the surface layer of soil near the sump at the east end of the drainage ditch contained a TPH concentration of 75,000 mg/Kg or parts per million (ppm). Field observations confirmed this sampling location as the area of greatest surface discoloration. Analyses results for sample 1 FY, collected at a depth of 3.5 to 4 feet directly below sample 1 FX, had 280 ppm TPN, indicating that TPH concentrations decrease sharply within four feet below surface. Lower concentrations of TPH (<50 ppm) were found in two other samples collected in the shallow surface layer along the length of the ditch. Field observations confirm this area as being discolored. Sample 5F was analyzed for TOG concentrations for comparison to TPH values. 0105HI S.RFr 1� GROUNDWATER z _�.�j;TECHNOLOGY