SITE INFORMATION AND CORRESPONDENCE 1995-2004

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0 0 James L. Tjosvold, P.E. August 19, 1996 Page 25 Response: 18. As stated in the response to comment #14, PG&E and the agencies have agreed to evaluate several groundwater limits in the FS for the Stockton former MGP site. As stated in our June 6, 1996 letter, the following is the range of groundwater limits and range of points of compliance for groundwater that will be evaluated against the screened alternatives. Range of limits for groundwater: • Background concentrations (non-detect) • The RWQCB's "Beneficial Use Protective Numerical Limits in Groundwater" • MCLs, or if no MCL exists, a 10-5 cancer risk based for carcinogens and a hazard index of less than 1 for noncarcinogens Range of points of compliance for groundwater: • Groundwater beneath the site • Groundwater at the perimeter of PG&E property Comment: 19. Page 9-4, Section 9.2, Recommendations I concur with the recommendation to use Alternative 5 as the remedial measure. Alternative 5 consists of insitu solidification/stabilization of affected areas and removal of tar in S3 We voiced some of our concerns regarding the selected remedy during our conference call with PG&E and CH2M Hill on 7 December 1995 We will present additional concerns, if any, at another conference call on 18 December 1995 after reviewing the treatability study work plan. Assuming the treatability study demonstrates Alternative 5's effectiveness to our satisfaction, PG&E needs to show that this technology will be applicable in areas where there is concrete or timber which was used as foundation for former structure at the sites. Response: 19. Because the FS for soil and groundwater is now recombined, there will be a recommended remedy for soil and groundwater. This remedial action may or may not include in-situ soil stabilization. If you have any questions or comments on the enclosed, please call me at (415) 973- 6254.