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L & M OPERABLE UNIT- FIRST QUARTER 2012 SITE STATUS, REMEDIAL SUMMARY, <br />AND GROUNDWATER MONITORING REPORT <br />Groundwater Monitoring and Sampling <br />April 30, 2012 <br />I:\Tidewater\TW Stockton (P2A)\QMRs\2012\1Q12\1Q12 QSSR QRSR QMR Stockton_FINAL.doc 2.3 <br />2.3.2 Shallow Zone Groundwater Quality Data <br />During 1Q12, groundwater samples were collected from 14 shallow zone wells between <br />January 17 and 20, 2012 (Table 1). Groundwater analytical results are presented in Tables 4 <br />through 7, and are summarized below. TPHg, TPHd, TPHo, benzene, MtBE, and TBA <br />isoconcentration contour maps are attached as Figures 3 through 8, respectively. Certified <br />laboratory analytical reports for the L&M OU samples are included in Appendix D. In addition, <br />Lab Validation Forms are attached for each individual report submitted by the laboratory, and <br />the laboratories sub contractors, which addresses issues and/or concerns with the validity of the <br />analytical data (Appendix D). <br />2.3.2.1 Separate Phase Hydrocarbons <br />During 1Q12, sheen was observed in 16 shallow wells; 13 of which were DPE wells. A figure <br />depicting historical depth to SPH versus time in comparison to depth to groundwater levels <br />measured in well 2AMW-14 is included as Figure 9; this well is singled out for trending purposes <br />because it is centrally located on the Site and has contained measurable SPH or observed SPH <br />sheen since its installation in 2Q02. SPH thicknesses were not measured for shallow zone <br />wells during 1Q12; “sheen” indicated a SPH thickness of less than 0.1 inch. <br />Well Identification SPH Thickness (feet) <br />2AMW-13 Sheen <br />2AMW-14 Sheen <br />MW-19 Sheen <br />DPE-1 Sheen <br />DPE-2 Sheen <br />DPE-3 Sheen <br />DPE-4 Sheen <br />DPE-5 Sheen <br />DPE-6 Sheen <br />DPE-7 Sheen <br />DPE-8 Sheen <br />DPE-9 Sheen <br />DPE-10 Sheen <br />DPE-11 Sheen <br />DPE-12 Sheen <br />DPE-13 Sheen