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Mr. Fernando Amador -6- 14 December 1995 <br /> Methodology or similar methods to determine if the contaminants in soil pose a threat to water <br /> quality. After our 30 November remedial project managers meeting, I handed Mr. Robert Doss a <br /> copy of the Draft Water Quality Site Assessment for Soils and Ground Water for their use. <br /> 17. Page 5-2, Section 5.2.2.2, Protection of Ground Water <br /> The FS proposes to "remediate significant areas of soil or residue that could serve as potential <br /> sources of COPC". Areas are considered"significant" if they meet three of the following four <br /> criteria: 1) The presence of concentrated and extensive residue, such as tar or oil; 2) Shallow <br /> ground water in the immediate vicinity of the contaminated soil or residue; 3) Hazardous' <br /> materials were formerly stored or handled; and 4) Elevated levels of COPC. As stated in Item 14 <br /> above, the purpose of the remedial action should be to reduce contaminant concentrations to <br /> levels which are protective of water quality goals. The proposed remedial approach does not <br /> completely provide ground water quality protection because only areas which meet three of the <br /> four criteria will be remediated. Based on this approach, even areas with elevated levels of <br /> COPC will not be remediated if they do not meet two other criteria. This approach is <br /> unacceptable because it is not protective of ground water quality. <br /> 18. Page 5-4, Section 5.3.2, Reduce Potential Migration to Ground Water <br /> At the time of writing the FS, the ground water quality goals for the site had not been <br /> established. As stated in Item 16, these goals are presented in Table 3. <br /> 19. Page 9-4, Section 9.2, Recommendations <br /> I concur with the recommendation to use Alternative 5 as the remedial measure. Alternative 5 <br /> consists of insitu solidification/stabilization of affected areas and removal of tar in S3. We <br /> voiced some of our concerns regarding the selected remedy during our conference call with <br /> PG&E and CHZM Hill on 7 December 1995. We will present additional concerns, if any, at <br /> another conference call on 18 December 1995 after reviewing the treatability study work plan. <br /> Assuming the treatability study demonstrates Alternative 5's effectiveness to our satisfaction, <br /> PG&E needs to show that this technology will be applicable in areas where there is concrete or <br /> timber which was used as foundation for former structure at the sites. <br /> Please transmit the above comments to PG&E. If you have any questions, you may call me at(916) <br /> 255-3049. <br /> 1g� <br /> HILS. ISORENA� ' <br /> Associate Engineer <br /> PSI:psi/lsb <br />