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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 2.26
<br />Constituent Zone
<br />Wells With
<br />Increased
<br />Concentration
<br />Number
<br />of Wells
<br />Wells
<br />Concentrations
<br />Decreased
<br />Number
<br />of Wells
<br />Wells With
<br />Stable or Non-
<br />Detectable
<br />Concentrations
<br />Number
<br />of Wells With
<br />Stable or Non-
<br />Detectable
<br />Concentrations
<br />TBA
<br />B -- 0 (0) -- 0 (0)
<br />MW-16, MW-24,
<br />MW-26, MW-27,
<br />MW-29, MW-32,
<br />MW-35, MW-42,
<br />MW-44, MW-51,
<br />MW-56, MW-57,
<br />MW-58, MW-59,
<br />MW-60
<br />15 (15)
<br />C -- 0 (2) MW-54, MW-64 2 (0)
<br />MW-61, MW-62,
<br />MW-63, MW-65,
<br />MW-66, MW-67
<br />6 (6)
<br />D -- 0 (0) MW-55, MW-70 2 (2)
<br />MW-68, MW-69,
<br />MW-71, MW-72,
<br />MW-73, MW-74
<br />6 (6)
<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 1Q12 (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 C-Zone wells, during 1Q12,
<br />slightly increased in some wells and remained stable or non-detect in the majority of wells in
<br />comparison to 4Q11. TPHg concentrations in groundwater samples collected from D-Zone
<br />wells decreased, remained stable, or non-detect, during 1Q12. TPHd concentrations in
<br />groundwater samples collected from B-Zone wells slightly increased in some wells but generally
<br />decreased in wells during 1Q12. TPHd concentrations in groundwater samples collected from
<br />C- and D-Zone wells decreased in the majority of wells in comparison to 4Q11. TPHo
<br />concentrations in groundwater samples collected from B-Zone wells had no apparent trend.
<br />TPHo concentrations in groundwater samples collected from C- and D-Zone wells decreased,
<br />remained stable, or non-detect during 1Q12. Benzene and TBA concentrations in groundwater
<br />samples collected from all deep zone wells (B-, C-, and D-Zone), during 1Q12, generally
<br />remained stable or were non-detect in comparison to 4Q11 data, and were consistent with
<br />historical data. MtBE concentrations in groundwater samples collected from B-Zone wells
<br />decreased, remained stable, or non-detect during 1Q12. MtBE concentrations in groundwater
<br />samples collected in C- and D-Zone wells, during 1Q12, generally remained stable or were
<br />non-detect, and were consistent with historical data.
<br />Dissolved TPHg and MtBE in B-Zone groundwater was delineated to the northwest, west,
<br />southwest, and south, except for a detection southwest of the Site in well MW-29 for TPHg and
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