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r 21 June 2002 • AGE-NC Project No 99-0624 IPage 5 of 6 as 49 gg/l,and from CPT-3 at depths of 68 feet and 100 feet bsg at concentrations of 37 µg/1 and 4 3 pg/l, respectively MTBE was not detected in water samples collected from CPT-4 (Table 1) No other petroleum constituents or fuel oxygenated compounds were detected from the laboratory analysis The laboratory reports (MAI Lab I D 83355 through 83366) and chain-of-custody forms are presented in Appendix B 4.0. SUMMARY AND CONCLUSIONS The implications of the November 2001 CPT investigation results are as follows The more permeable lithology encountered during the CPT Investigation consisted of a thick, laterally continuous silty to gravelly sand layer at a depth of between 7 and 20 feet bsg The remainder of the lithologic section to a depth of 100 feet bsg consists predominantly of CPT-defined stiff fine-grained sediment separated by generally thinner layers of clay, silt and sand The fine- grained sediments tend to have variable permeabilities,in general silts and clays appear to have low pore pressures relative to the stiff fine-grained sediments, which are generally characterized by wmoderate to high pore pressures Sand layers below 20 feet bsg tend to be thin(less than 2 feet thick)and laterally discontinuous,they appear to Increase in frequency vertically from approximately 85 feet bsg to 20 feet bsg, and tend to be concentrated towards the southern and eastern ends of the site Most of the thin sand layers were Interpreted on the CPT logs as cemented sands with high pore pressures AGE Interprets the CPT data to Identify seven hydrologic units(HUs)at the site The odd-numbered HUs are potentially high permeability flow units The even-numbered HUs are low-permeability flow units that may retard vertical migration of petroleum hydrocarbon compounds except MTBE TPH-g was not detected In any of the analyzed samples, of the BTEX compounds only benzene was detected in sample CPT-3-68 I MTBE was the only other analyte detected,at a maximum concentration of 88 gg/1 In HLT 1 at off-site CPT-1 MTBE was detected at all sampled depths in CPT- 2, and at all sampled depths except 80 feet bsg in CPT-3, however, at approximately 100 feet bsg (total depth) in both CPT locations, the MTBE concentrations had decreased to less than 10 gg/l, which is within California's Maximum Contamination Level for drinking water MTBE was not detected in water samples from CPT-4,nor detected in samples below HU1 in CPT-1 I • Advanced Geo Environmental,Inc