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Stantec <br /> L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2010 SITE STATUS, <br /> REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT <br /> Groundwater Monitoring and Sampling <br /> January 31, 2011 <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 4Q10 (Figures 3 through 8). <br /> TPHd concentrations generally remained stable from the 3Q10 to 4Q10. TPHg, benzene, and <br /> TBA concentrations remained stable or non-detect from the 3Q10 to 4Q10. TPHo and MtBE <br /> concentrations generally decreased or remained stable from the third quarter to 4Q10. <br /> The extent of shallow TPHg and TPHd are historically delineated except to the north where the <br /> Stockton Deep Water Channel exists. In addition, UOU and MOU wells to the east were not <br /> sampled during 4Q10; thus no delineation was observed in these areas. TPHd was detected on <br /> the southwestern portion of the site just south of the Mormon Slough at MW-30. TPHo, <br /> Benzene, and TBA were delineated during 4Q10. MtBE was delineated except to the east were <br /> UOU and MOU wells were not sampled during 4Q10 in shallow groundwater. TPHg, TPHd, <br /> TPHo, Benzene, MtBE, and TBA appear to be fairly stable throughout the shallow zone wells. <br /> 2.7.2 Deep Zone <br /> The following sections summarize trends for detected petroleum hydrocarbons, fuel oxygenates, <br /> and observed SPH for deeper (B-, C-, and D-Zone) groundwater beneath the Site. <br /> 2.7.2.1 SPH <br /> A summary of 4Q10 SPH thickness and SPH sheen in comparison to the 3Q10 is provided in <br /> the following table. <br /> Well Identification SPH Thickness SPH Thickness Difference <br /> (Zone) 3Q10 (Feet)* 4Q10 (Feet)* (Feet) <br /> MW-17 B Sheen Sheen NA <br /> MW-43 (B) 0.31 0.30 - 0.01 <br /> MW-46 (B) Sheen Sheen NA <br /> MW-47 (B) 0.01 0.01 0.0 <br /> MW-48 B 0.03 0.03 0.0 <br /> MW-49 (B) 0.72 0.52 - 0.20 <br /> MW-50 (B) 30.03 30.05 + 0.02 <br /> MW-52 (B) 0.01 0.01 0.0 <br /> Definitions: <br /> B = B zone wells <br /> NA = Not applicable/not available <br /> SPH = Separate phase hydrocarbon <br /> * = SPH removal occurred prior to groundwater sampling. <br /> I:\Tidewater\TW Stockton(Parcel 2A-0415)\Reports\QMR\2010\4010-Annual\4Q10 and Annual OSSRQRSRQMR Stockton_FINAL.doc 2.20 <br />