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F <br /> GEOMATR[X <br /> Mr.Robert ll ihalovich <br /> '*.,. Chevron Environmentat-:.Management Company . <br /> May 9,2002 <br /> Page 2,, <br /> 2. HERD adpises Site Mitigation Staff to assure that metals," riiculardy lead,are not also <br /> present:at the.site since a gasoline station was formerly at the site acid BTEX has been <br /> ''detected ingroundWater.; <br /> The objective of the additional investigations performedin May,and October 2000 was to <br /> assess the lateral extent of petroleum in soil at-off-site locations and to evaluate <br /> groundwater quality on site:and downgratlient of the site: The investigation focused on <br /> evaluating the potential impacts associated with the residual heavy petroleum <br /> hydrocarbon,specifically crude and/or fuel_oil, from ChevronTexaco's former Old Valley <br /> Pipeline(OVF)located along the rivrthern boundary of the site adjacent to,the railroad <br /> right>of=way. .Lead isnot a component of the historic crude and fuel.oil. <br /> 3. Additional soil axdgrourrdwater samples were collected,analyzed for tntat petroleum <br /> hydrocarbons(TPI PAfs,and BTL7X ,The additional data revealed BTEX ire <br /> groundwater. <br /> Five-groundwatergrabsamples were collected as part ofthe investigation and analyzed <br /> for TPH quantified as gasoline and diesel(TPHg and TPHd);benzene,toluene, <br /> ethylbenzene, and xylenes(R'E`EK); and pglynuclear.aromatic hydrocarbons(AARs). <br /> Toluene,ethylhenzene and xylenes were detected at concentrations:less than 2.6µg/1.. <br /> Benzene was detected in only one of five grab grou.11 er samples at a concentration of <br /> 0.6 micrograms per liter(4g/1),which is slightly above the laboratory reporting limit of <br /> 0.5.µg11: BTEX compounds were not detected above the laboratory reporting limits in. <br /> previous grab.groundwater,samples. <br /> SPECMC COAIM NTS <br /> L Previously,HE",commented that the vertical extent ofsoil contam,at on required <br /> clarification(7)TSC,2004}. The vertical extento <br /> f snit sampling was riataddressed in <br /> the,additional data collected. Soil sampling for the combined data set was limited.to 8ti S <br /> to lSft:belowground surface fts) <br /> As indicated above.Geomatrix provided a response to HERD's initial comment in a <br /> March 29; 2000 letter, a cagy Of which was attached in Appendix,A of the December <br /> 2000 Report of 4dditional Soil and Groundwater Investigation,prepared bar Geomatrix. <br /> As part of the overall technical approach for OVP sites,borings with petroleum <br /> hydrocarbon-affected soil are advanced until affected soil is no.longer observed in the <br /> recovered soil core. As a conservative estimate, soil samples submitteed.for chemical <br /> analysis are generally from the interval of the core with the most visibly affected soil. <br /> Thus,available analytical results for a particular soil boring do not necessarily reflect the <br /> vertical extent of observed.petroleurn at a site,but rather the depth of the most visually <br /> impacted depth interval. <br /> �- I <br />