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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 2.13 <br />2.5.2 C-Zone Groundwater Quality Data <br />During 1Q12, groundwater samples were collected from eight C-Zone wells between January <br />17 and 20, 2012 (Table 1). Groundwater analytical results are presented in Tables 4 through 7, <br />and summarized below. TPHg, TPHd, TPHo, benzene, MtBE, and TBA isoconcentration <br />contour maps are included as Figures 18 through 23, respectively. The certified laboratory <br />analytical reports for the groundwater sampling event conducted for the L&M OU are included in <br />Appendix D. <br />2.5.2.1 Separate Phase Hydrocarbons <br />During 1Q12, measurable SPH or SPH-sheen was not observed in any C-Zone wells. <br />2.5.2.2 Petroleum Hydrocarbons and Fuel Oxygenates <br />TPHg, TPHd, TPHo, and fuel oxygenates with concentrations at or above the MRLs are <br />summarized below. <br />Constituents <br />Number of <br />Detections <br />above the MRL <br />Number of <br />C-Zone <br />Wells <br />Analyzed <br />Minimum Detected <br />Concentration in mg/L <br />(Well ID) <br />Maximum Detected <br />Concentration in mg/L <br />(Well ID) <br />TPHg 4 8 0.35 (MW-65) 2.0 (MW-64) <br />TPHd 6 8 0.15 (MW-67) 1.8 (MW-54) <br />TPHo 3 8 0.062 (MW-63) 0.15 (MW-62) <br />Benzene 4 8 0.00093 (MW-54 & <br />MW-63)0.0047 (MW-66) <br />Toluene 1 8 --- 0.0020 (MW-66) <br />Ethylbenzene 1 8 --- 0.00059 (MW-64) <br />Total Xylenes 4 8 0.00052 (MW-62) 0.0045 (MW-66) <br />MtBE 3 8 0.00061 (MW-63) 0.0097 (MW-64) <br />TBA 2 8 0.020 (MW-64) 0.058 (MW-54) <br />Definitions: <br />ID = Identification <br />mg/L = Milligrams per liter <br />MRL = Method reporting limit <br />MtBE= Methyl tertiary butyl ether <br />TBA = Tertiary butyl alcohol <br />TPHd = Total petroleum hydrocarbons as diesel <br />TPHg = Total petroleum hydrocarbons as gasoline <br />TPHo = Total petroleum hydrocarbons as motor oil <br />--- = Not applicable