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0 <br /> O <br /> CONESTOGA-ROVERS <br /> &ASSOCIATES <br /> Previous investigation and remedial activities are discussed in the Site Background section which is <br /> presented in Attachment A. <br /> WORK PLAN <br /> As discussed with RWQCB staff during an April 18, 2007 meeting, a human health risk assessment <br /> (HRRA) is recommended to evaluate whether the soil and groundwater impacts beneath this site pose a <br /> potential threat to human health. To evaluate potential dermal and vapor threats to onsite commercial <br /> workers, soil sampling from the source areas and soil vapor sampling near the onsite commercial <br /> buildings is proposed. <br /> Technical Rationale for Proposed Scope of Work <br /> • Source area soil analytical data are limited and no soil data are available for shallow soils near the <br /> onsite commercial structures. <br /> • Historical data shows that elevated levels of petroleum hydrocarbons exist in groundwater beneath <br /> the site. <br /> • CRA proposes to collect shallow soil samples from two of the known source areas, and to install <br /> vapor probes around each of two onsite buildings. Soil and soil gas samples will be collected to <br /> evaluate potential dermal exposure to onsite workers, and to evaluate potential vapor migration <br /> through shallow soils into indoor air. <br /> Work Tasks <br /> Permits: A drilling permit will be obtained from SJCEHD. <br /> Health and Safety Plan: A site specific Health and Safety Plan will be prepared for fieldwork. <br /> Utility Clearance: The proposed drilling locations will be marked and the locations cleared through <br /> Underground Service Alert and a private utility locating service prior to drilling. <br /> Site Investigation: Two soil borings (SB-20 and SB-21) and ten soil vapor sample borings (V-1 through <br /> V-10) will be drilled at the approximate locations shown on Figure 2. The borings will be hand cleared <br /> prior to drilling according to CRA protocol. Borings SB-20 and SB-21 will be drilled using direct push <br /> Geoprobe equipment, and borings V-1 through V-10 will be drilled using a hand auger. <br /> 1729 2 <br /> Worldwide Engineering, Environmental,Canatruction, and IT Services <br />