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Stantec
<br /> L & M OPERABLE UNIT-THIRD QUARTER 2011 SITE STATUS, REMEDIAL SUMMARY,
<br /> AND GROUNDWATER MONITORING REPORT
<br /> Groundwater Monitoring and Sampling
<br /> October 28, 2011
<br /> Number
<br /> Wells With
<br /> Wells With Wells of Wells With
<br /> Number Number Stable or Non-
<br /> Constituent Zone Increased Concentrations Stable or Non-
<br /> of Wells of Wells Detectable
<br /> Concentration Decreased Detectable
<br /> Concentrations
<br /> Concentrations
<br /> MW-16, MW-24,
<br /> MW-26, MW-27,
<br /> MW-29, MW-32,
<br /> MW-35, MW-42,
<br /> B 0(0) 0(0) 15(15)
<br /> MW-44, MW-51,
<br /> MW-56, MW-57,
<br /> MW-58, MW-59,
<br /> TBA
<br /> MW-60
<br /> MW-61, MW-62,
<br /> c 0(2) MW-54, MW-64 2(0) MW-63, MW-65, 6(6)
<br /> MW-66, MW-67
<br /> MW-68, MW-69,
<br /> D MW-70 1 (3) MW-55, MW-71 2(0) MW-72, MW-73, 5(5)
<br /> MW-74
<br /> Notes:
<br /> TPHd quarterly comparison was indeterminable for well MW-71 due to the MRL being increased during 3Q11.
<br /> In general, reported TPHg, TPHd, TPHo, benzene, MtBE, and TBA concentrations in samples
<br /> from the deep zone wells were within historical ranges during 3Q11 (Figures 11 through 16 for
<br /> B-Zone, Figures 18 through 23 for C-Zone, and Figures 25 through 30 for D-Zone). TPHg
<br /> concentrations in groundwater samples collected from B- and D-Zone wells, during 3Q11,
<br /> slightly increased in some wells and remained stable or non-detect in the majority of wells.
<br /> TPHg concentrations in groundwater samples collected from C-Zone wells decreased, remained
<br /> stable, or non-detect, during 3Q11; there were no apparent trends. TPHd, TPHo, and MtBE
<br /> concentrations in groundwater samples collected from all deep zone wells (B-, C-, and D-Zone),
<br /> during 3Q11, generally increased, remained stable, or non-detect, and were consistent with
<br /> historical data. Benzene and TBA concentrations in groundwater samples collected from all
<br /> deep zone wells (B-, C-, and D-Zone), during 3Q11, generally remained stable or were
<br /> non-detect, and were consistent with historical data.
<br /> Dissolved TPHg in B-Zone groundwater was detected in three sections of the Site; northeast of
<br /> the Water Front Tower's parking lot in wells MW-42 and MW-58, east in well MW-59, and
<br /> southwest just south of the Mormon Slough in well MW-29. Dissolved TPHd in B-Zone
<br /> groundwater was delineated to the northwest and south, during 3Q11. Dissolved TPHo in
<br /> B-Zone groundwater was fully delineated, except for a detection west of the Site in well MW-26.
<br /> Dissolved benzene in B-Zone groundwater was not reported at concentrations at or above the
<br /> laboratory MRL, with the exception of one minor detection in well MW-58 located northeast of
<br /> I:\Tidewater\TW Stockton(P2A)\QMRs\2011\3Q11\3011 QSSR QRSR QMR Stockton_FINAL.doc 2.25
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