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James L. Tjosvold, P.E. <br /> August 7, 1996 <br /> Page 9 <br /> MW-23R is much closer to former MGP structures than the former service stations. <br /> Therefore, the former MGP structures would impact MW-231?sooner than the former service <br /> stations would. Furthermore, as in MW-22R, the boring log for MW-23R shows lampblack at <br /> 0.5-4 feet below ground surface. PG&E decided not to install MW-22R due to concerns that <br /> the upgradient former service stations could be impacting Area II. Following this line of <br /> reasoning, PG&E should not have installed MW-23R since it showed similar soil <br /> contamination and also is downgradient of the former service stations. PG&E should explain <br /> the discrepancy in the well installation protocol and why the potential impacts offormer <br /> service stations on MW-23R is not a concern. <br /> Response: <br /> 7. As stated in the workplan,the objective of this investigation was to find the extent of <br /> constituents in groundwater. Soil samples were not planned for this investigation. <br /> Investigation of soil in Area II has been discussed in the past and has been performed <br /> surficially,where possible. Although it is possible that there are other potential soil source <br /> areas in Area II,there are very few remaining places to drill in Area II and as discussed in our <br /> conference call on June 24, 1996. On page 16, the report notes that MW-23R may be <br /> downgradient of other former sources. <br /> Comment: <br /> 8. Page 20, Zone B Boreholes <br /> Instead of referring to the workplan protocol, the report should just succinctly explain why <br /> borings MW-22(a) and MW-23 were not suited for conversion to monitoring wells. <br /> Response: <br /> 8. The section titled 3.1.3 Modifications to the Workplan addressed the well installation <br /> process. <br /> Comment: <br /> 9. Page 21, Mud-Rotary Drilling <br /> The report should describe the fate of the drill cuttings and drilling mud. <br /> Response: <br /> 9. The drill cuttings and drilling mud were tested and found to have no detectable <br /> concentrations of chemicals of concern. They were disposed of off-site at a Class II landfill. <br /> Comment: <br /> 10. Page 63, Conclusions <br /> I have similar comments here regarding contamination in Zone B and the absence of a <br /> complete COPC pathway to ground water. <br />