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1 0 ' OEOMATRIX Measurable free phase petroleum is likely limited the area of the excavation backfill Given the ' limited extent,the sporadic occurrence of free product, and linuted volume of product available for removal, additional free product removal is not practicable at this site 2.4 CHENUSTRY OF TPH DETECTED IN GROUNDWATER ' Free product was collected from monitoring well MW-2 during the August 2004 sampling event and submitted to Friedman&Bruya, Inc (Friedman&Bruya)for forensic evaluation and characterization The product was characterized as a substantially degraded middle distillate such as diesel#2 or heating oil Friedman&Bruya indicated the product lacked the common water soluble, aromatic components such as BTEX,and would be considered insoluble in water Friedman & Bruya's forensic analysis is included in Appendix A The recent analytical data from the groundwater sample collected from MW-2 support this characterization The aromatic compounds such as BTEX are considered to be the more toxic components of petroleum fuel Because the residual petroleum at the site generally lacks the aromatic components,it ' is not considered to be highly toxic Further discussion of nsk posed to human health by the residual petroleum is presented in Section 2 6 2.5 POTENTIAL FOR MIGRATION,SURFACE WATER AND DRINKING WATER IMPACTS Petroleum constituents likely from a release from the former UST have been in direct contact with groundwater for a minimum of at least 16 years(UST removed in 1988) Groundwater analytical results Indicate that petroleum analytes and constituents are only detected in samples collected from ' monitoring wells installed within affected soil(Figure 3) Petroleum analytes or constituents generally are not detected in groundwater samples collected from monitoring wells located less than 100 feet downgradient of the affected soil(MW-5 and MW-6) A forensic analysis of the product present in MW-2 Indicates that the petroleum present at the site is not water soluble Therefore,the detections ' of TPHd in the three monitoring wells screened across petroleum affected soil likely represents either petroleum entrained on soil particulates in groundwater(turbidity)or globules of petroleum collected with the groundwater sample and are not representative of dissolved phase petroleum These data indicate the absence of a dissolved"plume"of petroleum hydrocarbons associated with the petroleum hydrocarbon affected soil Shallow groundwater within and downgradient of the petroleum affected soil is not currently used ' and is not anticipated to be used in the near future A well survey was conducted by ATC in 2000 that reportedly searched Department of Water Resources(DWR) files,performed a site and vicinity reconnaissance, and contacted the City of Stockton and California Water Service for wells within ' 1 Ooc_Safe19000s199631CAP1CAP txt doc 5