SITE INFORMATION AND CORRESPONDENCE 1995-2004

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James L. Tjosvold, P • October 5, 1999 Page 5 range) of the RAP remedy can reasonably be construed as undergoing a fundamental change as a result of PG&E's proposed modification. Rather,the increase in the volume of soils that would require treatment under the proposed modification would be termed more properly a"significant change", in accordance with the volume increase example from EPA guidance cited in the preceding section. Regulatory changes have made the use of a substitute treatment method preferable to that method specified in the RAP, but such substitution is clearly still reflective of the selected remedy overall. Performance The performance of the Stockton remedial measures in achieving the remedial goals set forth in the RAP depends on the removal of soils which contain constituents of concern at or above levels which could contribute to an exceedance of the beneficial use protective limits established for groundwater underlying the site. The proposed changes to the Stockton remedy do not affect the volume, location or nature of any soils to be removed at the site, and thus constitute no change to the performance of the remedy adopted in the RAP. Cost The proposed change to the Stockton remedial measure will add an incremental cost of operating the drying unit for approximately two weeks, at an estimated cost of$380,000. This cost increase will be offset by the savings in not conducting the asphalt batch process on site. The net effect on cost is substantially less than the potential effect on cost of not implementing the proposed change,which would require transport and disposal of approximately 1600-1700 cubic yards of material at a RCRA Subtitle C licensed facility, at an estimated cost of$1 million. Thus, PG&E's proposed modification to the remedy will have the effect of reducing any net change to the cost set forth in the RAP, as compared to the changes in overall cost which would be incurred by not implementing the modification. The public interest, and the interest of environmental protection, is best served by the implementation of the proposed change without undue delay. Setting aside for a moment the largely semantic issue of"significance"of the proposed modification to the remedy,there are several factors which argue for the imposition of the proposed changes without the attendant delay associated with the amendment proposal, public notice, comment period, public meeting,response to comments, and eventual re- issuance of a revised RAP. The thermal dryer/thermal oxidation process is a proven process designed to bring about the complete destruction of benzene in waste soils,without creating emissions of volatile compounds. The absence of chlorinated hydrocarbons in the soils to be treated eliminates