SITE INFORMATION AND CORRESPONDENCE

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5.0 RECOMMENDED,TNTERIM REMEDIAL ACTION Based on a comparison of`imedial alternatives utilizing the criLi listed above, RESNA proposes interim remediation of hydrocarbon-bearing soil and groundwater beneath the site by excavating contaminated soils both above and below the zone of saturation and extracting groundwater and floating free product, if present, from the open excavation. Quarterly groundwater monitoring and sampling activities will continue. This method of remediation, once implemented, should be the most timely, effective and cost- efficient alternative. Soil excavation in conjunction with groundwater extraction and treatment should substantially reduce levels of contaminants in the subsurface. Future remediation needs will be evaluated upon completion of soil excavation, remediation, and subsequent backfilling of the excavation. 6.0 INTERIM REMEDIATION WORKPLAN To prevent the remaining impacted soil from acting as a potential source of groundwater degradation, RESNA proposes the following scope of work. Field tasks proposed in this workplan will be performed according to the Quality Assurance/Quality Control Plan on file with PHS/EHD and the Site Safety and Health Plan (Appendix A). 6.1 Soil Excavation Suspected hydrocarbon impacted soil will be excavated by a licensed California contractor employing a backhoe tractor or tracked excavator. A front end loader will be used to stockpile the soil on site. It is estimated, based on data collected to date, that 1500 to 2400 cubic yards of soil (700 cubic yards of which may be impacted) will require excavation. Due to site space limitations for stockpiled soils and the need to maintain accessibility to the pumping plant, it may be necessary to complete the excavation in two separate phases. Excavated soils will be field screened by employing a photoionization detector (PID) calibrated to an isobutylene standard, as well as olfactory and visual observations. Clean soils will be stockpiled separately from the impacted soils based on field observations (odor, discoloration, PID readings). Following excavation, it is anticipated that one verification sample will be collected for every 20 linear feet along the sidewalls of the excavation and one for every 400 square feet of the excavation floor. The exact location of samples will be determined in the field under the regulatory guidance of PHS/EHD. All verification samples will be collected from the backhoe bucket from at least three inches below the surface of the soil. ' The samples will be collected into prewashed brass liners. Each liner will be sealed with Teflon sheets and plastic caps, sealed in air-tight bags, and preserved on ice pending shipment to a laboratory. Soil samples will be transported under chain-of- custody to a State-certified laboratory for analysis of BTEX and TPHd. Hydrocarbon impacted soils will be treated on site by either bioremediation or incineration and, subsequent to appropriate confirmation sampling, backfilled into the open excavation upon approval from PHS/EHD. 6.2 Groundwater Extraction and Treatment During the excavation process, the pit will be dewatered by pumping groundwater which flows into the pit. Depending upon the volume of groundwater extracted, the degree of contamination, and the volume of free product present, extracted groundwater will be treated by granular activated carbon and discharged to the sanitary sewer, discharged directly to the sanitary sewer l for treatment at the wastewater treatment plant, or transported to a licensed disposal facility. Upon completion of field activities and receipt of laboratory analyses, RESNA will summarize field methods and data collected during the remediation/excavation in a technical report to be submitted to PHS/EHD. t� ,