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Stantec Further Assessment Work Plan Stockton Charter Way Commingled Plume February 15, 2011 Screen Well ID Zone Top Bottom Justification (ft bgs) (ft bgs) SMW-5 A & B 20 45 Cross-screened SMW-6 A & B 25 50 Cross-screened SMW-7 A& B 22 42 Cross-screened, located at proposed building SMW-9 A & B 29.5 49.5 Cross-screened SMW-10 A& B 29.5 49.5 Cross-screened SMW-11 A & B 29.5 49.5 Cross-screened SMW-13 A & B 28.5 48.5 Cross-screened SMW-17 A& B 29.5 49.5 Cross-screened SMW-18-80 C 70 80 Located at proposed building SMW-18-120 D 110 120 Located at proposed building 2.2 Well Installation Based on the SCM, the following areas need to be delineated: in the A zone downgradient (south to southeast) of the Chevron and Sara Lee properties; in the B zone upgradient (west) and downgradient (northeast) of the ARCO property and in the central area of the Shell property; and in the C zone on the Chevron, ARCO, and Shell properties and downgradient (southeast) of the Sara Lee and Shell properties. Additional data in the C zone at the ARCO property was identified as a data gap in the SCM, but due to obstructions in the current property configurations including car wash canopies, overhead electrical lines, and the street, an alternative location (SMW-25C) on the Shell property is proposed instead. Delineation in the D zone will depend on the data collected from the proposed C zone wells. Further assessment and delineation towards the south and southeast of the Site will depend on the closure request outcome of the neighboring former Dolly Madison site (1426 South Lincoln Street). Boreholes will be advanced and monitoring wells will be installed in these areas in accordance with SJCEHD Well Standards (SJCEHD, 2005) and as described in Section 4.0 of this Work Plan. The proposed wells will be assigned field point names based on the nearest property in the Stockton Charter Way Commingled Plume Site and the numbering will continue from the last well at the property. The following table summarizes the details of the proposed wells. Table 2.2: List of wells to be installed Boring Casing Screen Well ID Zone Depth 0 0 Top Bottom Justification (ft bgs) (inch) (inch) (ft bgs) (ft bgs) SMW-24B B 60 10 4 40 55 Fill identified data gap SMW-25B B 60 10 4 40 55 Fill identified data gap SMW-26B B 60 8 2 45 60 Delineation SLMW-10B B 60 10 4 45 60 Replace decommissioned well SMW-25C I C 85 10 4 65 85 Fill identified data gap Stockton Charter Way Commingled Plume Further Assessment Work Plan.doc 4