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Stantec <br /> L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2010 SITE STATUS, <br /> REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT <br /> Soil Vapor Sampling <br /> January 31, 2011 <br /> 4.2.2 APSV Soil Vapor Concentrations <br /> Soil vapor sampling data collected during 4Q10 sampling event is provided in Table 25 and <br /> shown on Figure 35. None of the requested analytes were detected at or above the MRL in the <br /> APSV wells during 4Q10. <br /> 4.2.2.1 APSV Trends <br /> There were no detections of the requested analytes at or above the detection limits in the <br /> samples collected from the APSV wells. For all APSV wells, with the exception of APSV-1 and <br /> APSV-9, there were no detections of the requested analytes at or above the detection limits in <br /> the samples collected from the wells for the fifth consecutive quarter (4Q09 through 4Q10). <br /> Concentrations of TPHg typically exhibit a decreasing trend, with the exception of the slight <br /> detection in the two wells (APSV-1 and APSV-9) during the 3Q10 event (Table 25, Figure 36 <br /> through 38). <br /> 4.2.3 UPSV Soil Vapor Concentrations <br /> Soil vapor sampling data collected during 4Q10 sampling event is provided in Table 25 and <br /> shown on Figure 35. TPHg was detected in the soil vapor sample collected from UPSV-5 at a <br /> concentration of 831 ppmV. No other requested analytes were detected at or above the <br /> detection limits in the samples collected from the UPSV wells during 4Q10. There have been <br /> no fuel oxygenates detected in UPSV wells since their installation. <br /> 4.2.3.1 UPSV Trends <br /> UPSV-5 had a detection of TPHg (831 ppmV) during 4Q10 sampling event. For all other UPSV <br /> wells, with the exception of UPSV-3, there were no detections of the requested analytes at or <br /> above the detection limits in the samples collected from these wells for the fifth consecutive <br /> quarter (4Q09 through 4Q10). As shown in Table 25, TPHg has historically decreased in wells <br /> UPSV-1, UPSV-2, UPSV-3, and UPSV-6 base line sampling in July 2005 and since start up of <br /> the on-site remediation system on May 31, 2007. Additionally, benzene, ethylbenzene, and <br /> total xylenes have decreased to below detection limits which are complimentary to the <br /> decreasing trend of TPHg observed in well UPSV-6 (Figure 39). There have been no other <br /> apparent trends associated with reported concentrations in the UPSV wells. <br /> 4.2.4 Quality Assurance/Quality Control-Samples and General Laboratory Notes <br /> Duplicate samples APSV-10-D and UPSV-3D were collected from two soil vapor points <br /> (APSV-10 and UPSV-3, respectively) during 4Q10 sampling event. All analytes were below <br /> laboratory reporting limits. The trip blanks did not contain analytes at or above laboratory <br /> reporting limits. <br /> I:\Tidewater\TW Stockton(Parcel 2A-0415)\Reports\QMR\2010\4010-Annual\4Q10 and Annual OSSRQRSRQMR Stockton_FINAL.doc 4.2 <br />