SITE INFORMATION AND CORRESPONDENCE

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Mr. Victor Izzo August 28, 1994 Page 4 been extracted from the vadose zone, particularly in the area around the chemical storage shed. Comment W. Section. 5.4.1 Site Characterization, Paragraph 4; The statement, "77ie general northward gradient is apparently a. relatively recent development (within the last ten years) due to extensive ground water pumping to the north, near Stockton. 77te historic gradient was to the southwest, roughly parallel to the Stanislaus River. " is not supported. If this is supported by the literature or past data, please present the information. Also regional studies may not adequately describe local ground water gradients. Response: The statement is supported by the discussion on site hydrogeology in Section 3.3.1. As discussed above in the response to Comment IV, the previous submittals to RWQCB have included regional information which is incorporated in the RI by reference. Comment VII: Section 7.0, Summary and Conclusions, Paragraph 3; The statement, "...since prior to 1975, flow was towards the southwest. " needs to be supported. Please refer to comment VI. Response: Please see response to Comment VI. Comment VIII.- Plume Definition; The majority of the plume has been defined but, some further definition is needed. For example, Unit B southern extent needs to be defined. ?f wells were installed in the southern. area similar to Unit A, a larger plume in Unit B would likely be identified. Another area is south of monitoring well M-7 in Unit A. All units should be evaluated for data gaps. Response: We do not understand this comment, since the southern extent of the plume in the B unit is defined by non-detects or trace amounts of chemicals (below regulatory limits) in M14B, M17B, MI IB, and M713. Nestle does not believe that a data gap is present in the B unit. Well M7 and the area south is the Simpson Paper Company property, which is itself part of an ongoing RWQCB investigation. Currently Nestle is monitoring the Simpson production wells for chemical impacts. If these are not considered sufficient by the RWQCB, Simpson may be amenable to allowing sampling of selected shallow wells for additional monitoring. Three shallow wells are also located at the Ripon sewer ponds, which were sampled in August 1986, and at the time of sampling, these wells showed no impacts.