ARCHIVED REPORTS XR0001402 - Laserfiche WebLink

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1.2 Previous UST Related Work A 1,000-gallon gasoline UST located beneath the sidewalk along the eastern portion of the Site, an associated fuel dispenser located within the Site building, and a portion of product piping from the UST to the building were removed in December 1990 Remaining product piping, from the edge of the building to the former dispenser,was properly abandoned on April 17, 1998 On April 16, 1998, Philip drove two 1-inch diameter Geoprobe probeholes (PH-1 and PH-2) beneath the former UST to collect soil and groundwater samples for laboratory analysis Analytical results, summarized in Philip's June 2, 1998 Preliminary Subsurface Site Investigation Results and Product Piping Abandonment Completion report, indicated that benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds are present within subsurface soil and groundwater Soil and groundwater samples collected at that time did not contain detectable oxygenate compounds In July 1999, Ground Zero Analysis, Inc (GZA) of Escalon, California, performed a subsequent subsurface investigation GZA drilled three soil borings, completed them as groundwater monitoring wells (MW-1 through MW-3), and collected soil and groundwater samples for laboratory analysis GZA's investigation, summarized in their July 28, 1999 Groundwater Monitoring Well Installation Report, detected BTEX and total petroleum hydrocarbon as gasoline (TPHg) impact in soil and groundwater samples collected at the MW-2 location(see Figure 2) Samples collected from MW-1 and MW-3, placed in hydraulically upgradient positions relative to the former UST, did not contain detectable petroleum hydrocarbons EHD directed that several quarters of groundwater monitoring be performed to assess evolving conditions Results of these monitoring events indicated that relatively high petroleum concentrations were measured in samples collected at the MW-2 location and non-detectable or relatively low concentrations at the upgradient locations EHD requested that additional investigation be performed to assess the extent of petroleum impact Philip submitted a September 24, 2001 Subsurface Site Investigation Workplan to EHD, which proposed an investigation approach EHD approved this workplan in a letter dated October 16, 2001 Philip performed the latest investigation in March of 2002 During this investigation, Philip drove 6 Geoprobe borings (PH-3 through PH-8), installed one groundwater monitoring well (MW-4), constructed one air sparging well (SP-1), one soil vapor extraction well (VW-1), and collected soil and groundwater samples for laboratory analysis Investigation findings, submitted to EHD in the May 14, 2002 March 2002 Subsurface Site Investigation report, included the following s Pilot Testing Work Plan 1717 South Center Street-Stockton Cahfomla Prepared by Philip Services Corp H\ENW2400I32\121362EG1Projem\SwkC"tlpdmtestptmdo July 23 2002