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Supplemental Preliminary Site Investigation for State Route 99/Hammer Lane Project No. H2O2 <br /> to Mark Thomas & Co., Inc. November 17, 1999 <br /> CONCLUSIONS <br /> The Auto Factory <br /> (Former Texaco Station) <br /> PID readings indicated relatively low concentrations of hydrocarbons in the cuttings screened in the <br /> field for borings EGC-1 and EGC-2 (11 to 21.5 feet) and the presence of substantially higher <br /> concentrations of hydrocarbons in boring EGC-3 (highest concentrations from 16 to 21.5 feet), which <br /> is located near the northern part of the former tank pit. <br /> Our laboratory analysis detected the presence of hydrocarbons in the soil samples acquired from boring <br /> EGC-3 from 6 to 26.5 feet. Laboratory analysis of soil samples from borings EGC-1 and EGC-2 did <br /> not indicate the presence of hydrocarbons above the detection limits. <br /> Based on field screening (PID) and laboratory analysis (EPA test methods 8015m and 8020) of <br /> acquired soil and ground water samples, it appears that: 1) significant soil contamination has occurred <br /> at the location of boring EGC-3 from approximately 5 to 21.5, and; 2) ground water contamination <br /> with low levels of unidentified diesel hydrocarbons(likely degraded diesel) in the CIO-C24 range has <br /> occurred at the site. The source and extent of contamination has not yet been determined. <br /> Abandoned Gas Station <br /> (Former Mobile Oil Station) <br /> PID readings did not indicate the presence of hydrocarbons in the cuttings screened for borings EGC-4 <br /> through EGC-6. Our laboratory analyses also did not indicate the presence of hydrocarbons above the <br /> detection limits. Our laboratory analysis of a ground water sample detected the presence of <br /> unidentified diesel hydrocarbons in the C 10 - C 14 range at a concentration of 0.126 ug/L. <br /> Based on field screening (PID) and laboratory analysis (EPA test methods 8015m and 8020) of <br /> acquired soil samples, contamination of the soil with petroleum hydrocarbons has not occurred in the <br /> areas and depths explored. Ground water contamination with low levels of unidentified diesel <br /> hydrocarbons in the CIO - C14 range (likely degraded diesel) was detected at this site; however the <br /> source and extent of contamination has not yet been determined. <br /> SUMMARY OF RECOMMENDATIONS <br /> The Auto FactoEy <br /> (Former Texaco Station) <br /> If this site is to be acquired for interchange modification, the level of soil and ground water <br /> contamination should be discussed with all parties involved with the project. it is likely that the <br /> County of San Joaquin and/or the Regional Water Quality Control Board will require that the origin <br /> and extent of soil and ground water contamination be determined. <br /> 7 <br /> `� ESPANA GEOTECHNICAL CONSULTING <br />