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Mr.Brian'ravlor--- <br /> JLnVM 3! 2008____ Deleced:Mr.ed,n raymry <br /> Deleted:January 31,20081 <br /> Groundwater . <br /> There are 36 groundwater monitoring wells at the site; 35 of these monitor shallow groundwater <br /> conditions(5 to 39 fbg)and one well(DW-2)monitors deeper groundwater between 55 and 60 fog. The <br /> wells have been gauged and sampled since 1990, and samples are routinely analyzed for petroleum <br /> constituents. A summary of historical groundwater analytical data are presented in Attachment C. <br /> The primary groundwater COCl for this site(TPHg,TPHd,benzene,MTBE,and TBA)have been fully i <br /> delineated already. Minor detections of TPHd,TBA, and DIPE in deep well DW-2 indicate insufficient <br /> mass to pose a risk to any potential down gradient receptors. - - <br /> INTERIM REMEDIAL ACTION PLAN <br /> Technical Rationale and Objectives <br /> CRA!s May 4, 2007 FS concluded that DPE in the three source areas is the most feasible and cost- <br /> effective remedial alternative for this site based on the cleanup goals,remedial objectives, assumptions, <br /> and limitations established in the FS. As previously discussed,the RWQCB and Shell agreed to conduct <br /> a DPE pilot test to validate the conclusions of the FS. The objectives of the proposed pilot test are as <br /> follows: <br /> • Determine the magnitude and potential sustainability of extracted hydrocarbon soil vapors.from - <br /> the three source areas. <br /> • Determine the air flow rate"that the vadose and dewatered soils can yield. <br /> • Determine if the aquifer yield will be enhanced under vacuum;determine sustainable yield. <br /> • Assess groundwater drawdown and hydraulic control. <br /> • Assess vacuum distribution and pneumatic radius of influence. <br /> • Collect technical information for potential full-scale remediation system design. <br /> The following sections describe the proposed scope of work and work tasks to meet the objectives <br /> described above. <br /> WELL INSTALLATIONS <br /> CRA proposes installing three extraction wells and two observation wells for DPE pilot testing. Figure 2 <br /> presents the locations of the proposed wells. <br /> 241729 _4 <br />