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Off 01 0 <br /> Scott Mansholt <br /> - 2 - 23 May 2006 <br /> Chevron - 990 Beechnut <br /> Off-site Groundwater Investigation <br /> the laboratory documents, the chromatogram for the 180 pg/I TPHd detection notes that the <br /> pattern is atypical of diesel when compared to known groundwater samples containing TPHd. <br /> The report concludes that the TPHd detection is not related to crude oil/Bunker fuel typical of <br /> petroleum hydrocarbons found at other nearby Chevron OVP sites. <br /> Sample analysis for TPHg, TPHd, and BTEX were not detected above the laboratory reporting <br /> limit in the 990SB-2 sample; however, three PAHs were reported slightly over the laboratory <br /> detection limits, but were less than the U. S. EPA Region 9 Tap Water Preliminary <br /> Remediation Goals (PRGs) for the respective compounds, except for phenanthrene, which <br /> does not have a PRG. <br /> Based on the findings of the various investigations, we concur that the extent of impacted <br /> groundwater has been adequately delineated offsite - downgradient. <br /> Soil and groundwater has been extensively investigated both on and offsite and Geomatrix <br /> has recommended that a human health risk evaluation be completed for the onsite conditions. <br /> However, Regional Water Board staff cannot make a final decision until the Office of <br /> Environmental Human Health Assessment (OEHHA) or the Department of Toxic Substances <br /> Control (DISC) completes the human health risk assessment for the onsite property. Based <br /> on the OEHHA or DTSC assessment, additional borings and samples could be needed. <br /> If you have any questions, please call Dean Hubbard at (559) 445-5179. <br /> ��? `�� �. ) L dFA0 <br /> SHELTON R. GRAY C. DEAN HUBBARD <br /> Senior Engineering Geologist Professional Geologist <br /> P.G. No. 6357 <br /> cc: Michael Infurna, Jr., San Joaquin County EHD, Stockton <br /> Gary Foote, Geomatrix, Oakland <br /> Luis Mercado, SAIC, Sacramento <br />