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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 /> Summary of 2012 Annual Monitoring and Sampling
<br /> February 1, 2013
<br /> Well MW-46 contained sheen during all four quarters of 2012. Wells MW-17, MW-47, and
<br /> MW-52 contained sheen during all four quarters, except during the 2Q12 (0.01 ft), 3Q12
<br /> (0.01 ft), and 2Q12 (0.02 ft), respectively. Wells MW-43, MW-48, MW-49, and MW-50
<br /> contained SPH during all four quarters of 2012, except in well MW-48 during 4Q12. Measurable
<br /> SPH in wells MW-17, MW-43, MW-47 through MW-50, and MW-52 ranged between 0.01 ft
<br /> (MW-17, 2Q12; MW-47, 3Q12; MW-48, 1Q12) and 30.70 ft (MW-50, 4Q12) during 2012. No
<br /> patterns of measurable SPH was observed during the 2012 in B-Zone wells.
<br /> Wells MW-17, MW-43, and MW-46 through MW-49 have had a decreasing trend since
<br /> monitoring began, in 2005, or since sheen has been observed, in 2008. Wells MW-50 and
<br /> MW-52 have had a stable trend. No measurable SPH has been observed in wells MW-17 and
<br /> MW-46 since sheen was first observed in 2005 and 2008, respectively, with the exception of an
<br /> isolated SPH detection during 2Q12 in well MW-17.
<br /> SPH removal activities were conducted on B-Zone wells MW-17, MW-43, MW-46 through
<br /> MW-50, and MW-52 during all four quarters 2012. Each of these wells is located in the
<br /> Waterfront Towers Parking facility north of the L&M OU.
<br /> 5.6 A-ZONE ISOCONCENTRATION TRENDS
<br /> Shallow zone isoconcentration trends are discussed below. Figures from 1Q12, 2Q12, and
<br /> 3Q12 are provided in Appendix K.
<br /> 5.6.1 TPHg
<br /> Concentrations of TPHg are generally detected on the northern section of the L&M OU and the
<br /> eastern side of the Water Front Towers' parking lot. Based on data collected historically and
<br /> during 2012 for the shallow zone wells, the TPHg plume is generally delineated to the south,
<br /> southwest, and west. The City of Stockton did not sample their wells on the UOU or MOU
<br /> during 2012; therefore, TPHg could not be delineated to the east. In addition, the Stockton
<br /> Deep Water Channel is present to the north of the Site; therefore, TPHg could not be delineated
<br /> to the north.
<br /> 5.6.2 TPHd
<br /> Concentrations of TPHd are generally detected on the L&M OU property and the Water Front
<br /> Towers' parking lot. Based on data collected historically and during 2012, the TPHd plume is
<br /> generally delineated to the west, south, and northwest, with the exception of two detections
<br /> southwest of the Mormon Sough (MW-30 and MW-33) during 1Q12 and 2Q12. During 4Q12,
<br /> the TPHd plume was delineated to the southwest only. The City of Stockton did not sample
<br /> their wells on the UOU or MOU during 2012; therefore, TPHd could not be delineated to the
<br /> east. In addition, the Stockton Deep Water Channel is present to the north of the Site;
<br /> therefore, TPHg could not be delineated to the north.
<br /> 5.6.3 TPHo
<br /> Concentrations of TPHo are generally detected on the L&M OU property, and very seldom
<br /> detected on the Delta View apartment property. The TPHo plume was fully delineated during
<br /> I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 5.3
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