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L & M OPERABLE UNIT- FIRST QUARTER 2012 SITE STATUS, REMEDIAL SUMMARY, <br />AND GROUNDWATER MONITORING REPORT <br />Soil Vapor Sampling <br />April 30, 2012 <br />I:\Tidewater\TW Stockton (P2A)\QMRs\2012\1Q12\1Q12 QSSR QRSR QMR Stockton_FINAL.doc 4.3 <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 1Q12 sampling event. Comparison of TPHg and <br />Methane are shown below. <br />Analyte Sample # <br />APSV-10 <br />Sample # <br />APSV-10D % Difference <br />TPHg (ppmV)12.0 11.0 +/-8.7 % <br />Methane (ppmV)<1,000 <1,000 0 % <br />Analyte Sample # <br />UPSV-3 <br />Sample # <br />UPSV-3D % Difference <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 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.