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4 SUMMARY AND RECOMMENDATIONS <br /> A summaryof site conditions and a recommendation for subsequent work are as <br /> q <br /> follows <br /> • A gasoline release occurred at the facility, apparently from one of two 6,000- <br /> gallon USTs that were removed in April 1987 <br />' • PSC's June 2004 subsurface investigation comprised seven borings that included <br /> a continuous electronic log, and collection of site soil and groundwater samples <br /> for laboratory analysis Two sets of groundwater samples were also collected <br /> from two private water wells at a private residence in relative close proximity to <br /> the site <br />' • Subsurface lithology at the site comprises primarily salt and clay with some <br /> interbedded fine-grained sand to a depth of 100 feet <br />' • Soil samples collected in June 2004 did not contain detectable levels of petroleum <br /> hydrocarbons Analytical data indicates that impacted soil was likely removed <br /> during the 1987 UST removals and also addressed by the soil vapor extraction <br /> system that was employed at the site Analytical data suggests that the mass of �— <br /> petroleum impacted soil within the vadose zone is negligable <br /> • Recent depths to groundwater average about 45 feet Groundwater flows <br /> northeasterly at a gradient of about 3 1 x 10-3 feet per linear foot <br /> • Historical decreases of petroleum impact to groundwater have been observed, <br /> which are likely a result of natural degradation and the use of air sparging as a <br /> remedial method <br />' • Petroleum hydrocarbon impact was not indicated at the two private off-site water <br /> wells <br /> • Relatively stable or decreases of TPH-G and BTEX levels continue to be <br />' observed at groundwater sampling locations near the former USTs, however, <br /> some increases were noted particularly at the PZ-i well <br /> • Lower than typical BTEX to TPH-G ratios suggest that the air sparging <br /> remediation system was having a desired affect on the more volatile, Iighter range <br /> petroleum fractions <br /> • Groundwater analytical data indicates that the vertical extent of total petroleum <br /> impact at the site is approximately 90 feet Relatively higher petroleum levels <br /> appear to occur in groundwater at depths shallower than 70 feet <br /> The oxygenate compound DIPE was detected most recently in only PIKO <br /> groundwater samples <br /> 15 <br /> June 2004 Site Investigation Report <br /> The Earthgrains Company Facility <br /> 2651 South Airport Way-Stockton,California <br /> Prepared for SARA LEE BAKIIVG GROUP Prepared by Philip Services Corp <br /> H lEIW1624001321121382EG\Stockton\]une 2004 Investigation R"rt doe August 9,2004 <br />