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4 <br /> Final Remedial InvestigatioO -2- i 9 August 1994 <br /> Nestles Beverage Company <br /> The report states, 'Based on the nature and extent of impact, the chemical of concern appear <br /> to have migrated in ground water from the site towards the south and southwest." Another <br /> alternative to this south to southwest trend is that the sewer line acted as conduit for the TCE <br /> contamination. While the contamination originally leaked from the sewer line itself. Since <br /> the plume and sewer line location coincide, and the city sewer plant ponds are located to the <br /> south causing a constant high head and probably a northerly ground water gradient, rather <br /> than to the south, the leakage from the sewer line may have caused this southerly extension <br /> of this plume. This scenario should be considered when evaluating transport mechanism and <br /> TCE release points. <br /> V. Section 5.4 Chemical Migration; <br /> Though we general agree with the statements made in this section, the nature and extent of <br /> soil contamination has not been adequately investigated. Because of this, the inference made <br /> of minimal vadose zone impacts can not be substantiated. Also the statement, "... ongoing <br /> soil vapor extraction has greatly reduced organic vapor concentration." has little supporting <br /> data. The above conclusions need to be supported by data. <br /> VI. Section 5.4.1 Site Characterization, Paragraph 4; <br /> The statement, "The general northward gradient is apparently a relatively recent development <br /> (within the last ten years) due to extensive ground water pumping to the north, near Stockton. <br /> The historic gradient was to the southwest, roughly parallel to the Stanislaus River." is not <br /> supported. If this is supported by the literature or past data, please present the information. <br /> Also regional studies may not adequately describe local ground water gradients. <br /> VII. Section 7.0 Summary and Conclusions, Paragraph 3; <br /> The statement, ..... since prior to 1975, flow was towards the southwest." needs to be <br /> supported. Please refer to comment VI. <br /> VIII. Plume Definition; <br /> The majority of the plume has been defined but, some further definition is needed. For <br /> example, Unit B southern extent needs defined. If wells were installed in the southern area <br /> similar to Unit A, a larger plume in Unit B would likely be identified. Another area is south <br /> of monitoring well M-7 in Unit A. All units should be evaluated for data gaps. <br /> We appreciate the cooperation of Nestles Beverage Company in this investigation and we may want <br /> to meet to further discuss these comments. Should you have any questions, please contact me at <br /> (916) 255-3059. <br /> Victor J. Izzo, R.G. <br /> Associate Engineering Geologist <br /> cc: Department of Toxic Substances Control, Region 1, Sacramento <br /> Ms. Laurie Cotulla, Public Health Services of San Joaquin County Environmental Health <br /> Division, Stockton <br /> Dr. Walter Carey, Nestles USA, New Milford, Connecticut <br /> Ms. Sara Black, RUST Environment & Infrastructure, Englewood, Colorado <br />