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Stantec <br /> L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2012 SITE STATUS, <br /> REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT <br /> Soil Vapor Sampling <br /> February 1, 2013 <br /> 4.2.4 Quality Assurance/Quality Control-Samples and General Laboratory Notes <br /> Duplicate samples APSV-9-D and UPSV-3-D were collected from two soil vapor points (APSV-9 <br /> and UPSV-3, respectively) during 4Q12 sampling event. Comparison of TPHg and Methane are <br /> shown below. <br /> Analyte Sample # Sample # % Difference <br /> APSV-9 APSV-9-D <br /> TPHg (ppmV) 44.0 53.8 +/-20.0 % <br /> Methane (ppmV) 110,000 110,000 0 % <br /> Analyte Sample # Sample # % Difference <br /> UPSV-3 UPSV-3-D <br /> TPHg (ppmV) <2.4 <2.4 0 % <br /> Methane (ppmV) <1,000 <1,000 0 % <br /> The trip blank did not contain analytes at or above laboratory reporting limits. <br /> 4.2.5 Conclusions and Recommendations <br /> All reported TPHg concentrations were non-detect (less than 2.4 ppmV) in the APSV and UPSV <br /> wells during the reporting quarter with the exception of UPSV-5, APSV-9, and APSV-10. BTEX, <br /> naphthalene and the five fuel oxygenates (MtBE, DIPE, EtBE, TBA, and TAME) have not been <br /> detected at or above laboratory MRLs since fourth quarter 2008 in APSV and UPSV wells. <br /> Methane has been sporadic in both APSV and UPSV wells. <br /> Based on data presented in this report, Stantec recommends continuing with the soil vapor <br /> monitoring schedule as presented in the Work Plan prepared by SECOR and entitled Revised <br /> Work Plan for Soil Vapor Assessment and Response to RWQCB-CVR Letter Dated May 3, <br /> 2005. Results of future sampling will be provided in Stantec's corresponding quarterly Site <br /> monitoring and sampling reports. <br /> I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4012 and Annual QSSR QRSR QMR Stockton_FINAL.doc 4.3 <br />