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I <br /> Stantec <br /> No Further Action Request Report <br /> Chevron and ARCO Commingled Plume No. CP0034 <br /> April 10, 2012 <br /> i <br /> 5. CONCLUSIONS <br /> The information presented in this report demonstrates that the subject site meets the no further <br /> action required criteria specified in the "Tri-Regional Recommendations" (CRWQCB-CVR, <br /> 2004). <br /> All constituents of concern are below me h detection limits or screening levels, with fae <br /> exception of concentrations in Chevron wells -2R and MW,-5R and ARCO well E- <br /> However, trend analysis shows that concentrations in these wells are ecreasing an will meet <br /> water quality objectives in MW-2R and MW-5R within a year and in E-10 within approximately <br /> twelve years. <br /> /lGroundwater depth at the site during the:last four sampling events has ranged between 5.85 <br /> and 11.92 ft bgs at gradients ranging between 0.003 to 0.005 ft/foot. Historically, groundwater <br /> flow has been dominantly to the northeast; however, during the last four sampling events the <br /> groundwater direction has been to the north and north-northwest. The closest water supply well <br /> is located approximately 2,300 ft east (cross-gradient) of the site. Minimal mass remains in <br /> groundwater and soil, and is unlikely to pose a threat to human health and safety or impact any <br /> of the sensitive receptors within a half-mile radius of the site. Stantec believes the <br /> contamination remaining in soil and groundwater will naturally degrade through monitored <br /> natural attenuation Based on this evaluation, Stantec, on behalf of Chevron, respectfully <br /> requests that the California Regional Water Quality Control Board issue a letter of no further <br /> action required for the subject site. <br /> I <br /> 94275 NFAR 2012.doc 18 <br />