SITE INFORMATION AND CORRESPONDENCE 1995-2004

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James L. Tjosvold,P4 • October 5, 1999 Page 3 benzene above the RCRA hazardous waste threshold concentration remains to be excavated from the bottom of the former relief holder/crude oil storage tank northwest of Source Area 3. PG&E proposes to treat this soil on-site through the use of an indirect dryer. In this process, air is heated indirectly by a natural gas flame and is forced through ducts into a rotary drum chamber containing the soil to be treated. The hot air(approximately 300° F.)volatilizes benzene in the soil as the soil is conveyed through the rotary drum;the air containing benzene and water vapor is drawn out of the drum and into the heater flame (at approximately 1800° F.)where the benzene is thermally oxidized. Treated soil is discharged from the end of the rotary drum. Treated soil will be shipped to the Waste Management, Incorporated facility at McKittrick, California,to be blended into asphalt road base. A schematic of the proposed process is attached. The proposed dryer process would be operated by Sierra Process Systems, Inc. of Bakersfield, California, under both a DTSC Transportable Treatment Unit Permit-By- Rule and under an Authority to Construct Permit issued by the San Joaquin Valley Unified Air Pollution Control District. PG&E estimates that the soil drying process could be conducted over a period of approximately 2-3 weeks. Federal Regulations and Guidance on Evaluating Changes to Site Remedies DTSC's policies with regard to evaluating a proposed change to a remedial action plan are consistent with the regulations promulgated under the federal Comprehensive Environmental Response, Compensation and Liability Act("CERCLA") program concerning differences from a remedy established under a Record of Decision("ROD") (for purposes of this discussion, a state program RAP can be considered the equivalent of a ROD under the federal program). The regulations, set forth at 40 CFR §300.435(c)(2), provide in relevant part that: "...after the adoption of the ROD, if the remedial action ...taken ...differs significantly from the remedy selected in the ROD with respect to scope,performance, or cost,the lead agency ...shall either: (i) Publish an explanation of significant differences when the differences in the remedial or enforcement action ...significantly change but do not fundamentally alter the remedy selected in the ROD with respect to scope, performance,or cost ...; or, (ii) Propose an amendment to the ROD if the differences in the remedial or enforcement action ...fundamentally alter the basic features of the selected remedy with respect to scope, performance, or cost." (emphasis added.)