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Stantec
<br /> L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2012 SITE STATUS,
<br /> REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT
<br /> Groundwater Monitoring and Sampling
<br /> February 1, 2013
<br /> 2.7.1.2 Fuel Oxygenates and Petroleum Hydrocarbon Concentrations
<br /> A summary of 4Q12 shallow zone concentration trends of TPHg, TPHd, TPHo, benzene, MtBE,
<br /> and TBA in comparison to results reported during the 3Q12 are presented in the table below.
<br /> Values in parentheses represent number of detections and non-detections that were reported in
<br /> the 3Q12.
<br /> Number Number Wells With Number
<br /> Wells Wells of Wells With
<br /> of Wells of Wells Stable or Non-
<br /> Constituent Concentrations Concentrations Stable or
<br /> Concentrations Concentrations Detectable
<br /> Increased Increased Decreased Decreased Concentrations Non-Detectable
<br /> Concentrations
<br /> TPHg 2AMW-12, 2(1) MW-9,MW-20 2(3) 0(8)
<br /> MW-18
<br /> TPHd MW-20 1 (1) MW-9,2AMW-12 2(5) MW-18 1 (5)
<br /> TPHo 0(i) MW-9 1 (2) 2AMW-12, 3(9)
<br /> MW-18,MW-20
<br /> Benzene 0(0) MW-9 1 (1) 2AMW-12, 3(11)
<br /> MW-18,MW-20
<br /> MtBE 0(0) MW-9 1 (1) 2AMW-12, 3(11)
<br /> MW-18,MW-20
<br /> TBA 0(0) MW-9 1 (1) 2AMW-12, 3(11)
<br /> MW-18,MW-20,
<br /> Notes:
<br /> Wells MW-21,MW-22,MW-23,MW-25,MW-28,MW-31,MW-34,and MW-45 were not sampled during 4Q12 per MRP No.R5-2012-0805.
<br /> In general, reported TPHg, TPHd, TPHo, benzene, MtBE, and TBA concentrations in samples
<br /> from the shallow zone wells were within historical ranges during 4Q12 (Figures 3 through 8).
<br /> TPHg concentrations decreased or increased in wells from the 3Q12 to 4Q12. TPHd
<br /> concentrations generally decreased in wells from the 3Q12 to 4Q12. TPHo, benzene, MtBE,
<br /> and TBA concentrations generally remained stable or non-detect from the 3Q12 to 4Q12. A
<br /> historical low was reported in well MW-9 for TPHg (0.82 mg/L) and benzene (0.0058 mg/L)
<br /> during 4Q12. A historical low was reported in well 2AMW-12 for TPHd at a concentration of
<br /> 1.3 mg/L during 4Q12.
<br /> The extent of shallow TPHg and TPHd are historically delineated except to the north where the
<br /> Stockton Deep Water Channel exists. During 4Q12, TPHg and TPHd were delineated to the
<br /> southwest only. TPHg and TPHd delineation to the east was not obtained due to the UOU and
<br /> MOU wells not sampled during 4Q12. During 4Q12, TPHo, benzene, MtBE, and TBA were
<br /> delineated to the north and northwest only. TPHo, benzene, MtBE, and TBA were not
<br /> delineated to the east where the UOU and MOU wells were not sampled during 4Q12. TPHg,
<br /> TPHd, TPHo, Benzene, MtBE, and TBA appear to be stable throughout the shallow zone wells.
<br /> I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 2.14
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