SITE INFORMATION AND CORRESPONDENCE 1995-2004

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• • James L. Tjosvold, P.E. August 19, 1996 Page 24 Attachment 3. PG&E should perform a water quality assessment using Dr. Jon Marshack's Designated Level Methodology or similar methods to determine if the contaminants in soil pose a threat to water quality. After our 30 November remedial project managers meeting, I handed Mr. Robert Doss a copy of the Draft Water Quality Site Assessment for Soils and Ground Water for their use. Response: 16. At the time the draft Soil OUFS was prepared, there had not been an agreement between PG&E, DTSC, and the RWQCB on groundwater objectives and goals. Therefore, the beneficial use limits for groundwater as listed in Attachment 3 were not included in an FS that was geared toward recommending a soil remedy. As stated in the response to comment#14 above, PG&E will include the beneficial use limits developed by Dr. Jon Marshack as one of the criteria in evaluating soil treatment alternatives. As stated above, instead of using Jon Marshack's Designated Level Methodology, the VLEACH model was used to demonstrate that, after soil source area treatment, on-site soils do not pose a threat to groundwater. Comment: 17. Page 5-2, Section 5.2.2.2, Protection of Ground Water The FS proposes to "remediate significant areas of soil or residue that could serve as potential sources of COPC". Areas are considered "significant" if they meet three of the following four criteria: 1) The presence of concentrated and extensive residue, such as tar or oil;2) Shallow ground water in the immediate vicinity of the contaminated soil or residue; 3) Hazardous materials were formerly stored or handled; and 4) Elevated levels of COPC. As stated in Item 14 above, the purpose of the remedial action should be to reduce contaminant concentrations to levels which are protective of water quality goals. The proposed remedial approach does not completely provide ground water quality protection because only areas which meet three of the four criteria will be remediated. Based on this approach, even areas with elevated levels of COPC will not be remediated if they do not meet two other criteria. This approach is unacceptable because it is not protective of ground water quality. Response: 17. As discussed in most of the responses above,work has been and will be performed to demonstrate that the selected remedies will be protective of groundwater. The conceptual model described earlier will be included in the FS along with modeling results. Comment: 18. Page 5-4, Section 53 2, Reduce Potential Migration to Ground Water At the time of writing the FS, the ground water quality goals for the site had not been established. As stated in Item 16, these goals are presented in table 3.