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4 <br /> ATTACHMENT A <br /> RWQCB APPENDIX B CHECKLIST RESPONSES <br /> The following are responses to the ten checklist Mems contained in Appendix B of the "Tri- <br /> Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of <br /> Underground Tank Sites" <br /> 1 Distance to production wells for municipal,domestic,agriculture, industry and other uses within <br /> 2,000 feet of the site <br /> The Stockton Deep Water Channel runs under a portion of this site No well survey has been <br /> completed for this site However, the fuel hydrocarbons originating from the site have been <br /> remediated and no longer threaten any potential sensitive receptors in the vicinity The HVOCs <br /> detected in site monitoring wells appear to have originated offsite <br /> 2 Site maps, to scale, of area impacted showing locations of former and existing tank systems, <br /> excavation contours and sample locations, borings and monitoring well elevation contours, <br /> gradients and nearby surface waters, buildings, streets, and subsurface utilities <br /> A site vicinity map and site plan are included as Figures 1 and 2 Sample locations and a <br /> groundwater contour map are presented in Attachments B and C <br /> ® 3 High and low groundwater levels (below ground surface) <br /> Depth to groundwater under the site has ranged from 16 to 37 feet below ground surface (bgs) <br /> since 1992 Historical depth to groundwater and groundwater elevation data are presented in <br /> Attachment C <br /> 4 Tabulated results of all sampling and analysis <br /> Tabulated historical soil and groundwater analyttcal data are presented in Attachments B and C, <br /> respectively <br /> 5 Vertical and lateral concentration contours of contaminants found initially and those remaining <br /> in soil and groundwater, both on and off site <br /> Concentration contours showing initial hydrocarbon concentrations in soil and groundwater are <br /> provided in Attachments B and C, respectively Analytical data indicate that soil vapor extraction <br /> (SVE), groundwater oxygenation (GWO), and groundwater extraction (GWE) have effectively <br /> removed the original hydrocarbon mass from soil and groundwater beneath the site TPHg and <br /> BTEX concentrations in site monitoring wells have decreased to near or below detection limits <br /> Therefore, current concentrations have not been contoured <br /> 6 Mass balance calculation of the substance treated versus that remaining <br /> Mass balance calculations representing site conditions prior to remediation are attached <br /> Analytical data indicate that SVE, GWO, and GWE have effectively removed the original <br /> hydrocarbon mass from soil and groundwater beneath the site TPHg and BTEX concentrations in <br /> A-1 <br />