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S E C O R <br /> • general, TPHg and TPHd concentrations decreased from the fourth quarter 2007 to first quarter <br /> 2008. The extent of shallow TPHg and TPHd are delineated except to the north where the <br /> Stockton Deep Water Channel exists. TPHo, benzene, MtBE, and TBA are delineated in <br /> shallow groundwater. Benzene, MtBE, and TBA appears to be fairly stable throughout the <br /> shallow zone wells. <br /> 4.5.2 Deep Zone <br /> The following sections summarize trends for detected petroleum hydrocarbons, fuel oxygenates, <br /> and observed SPH for deep (B-Zone)groundwater beneath the Site. <br /> 4.5.2.1 SPH <br /> A summary of first quarter 2008 SPH thickness and SPH sheen in comparison to the fourth <br /> quarter of 2007 is provided in the following table. <br /> Well Identification SPH Thickness SPH Thickness Difference <br /> 4Q07 (Feet) 1Q08 (Feet) (Feet) <br /> MW-17 Sheen Sheen NA <br /> MW-40 0.60 Sheen NA <br /> MW-43 NA 0.17 *NA <br /> MW-46 ND Sheen NA <br /> MW-47 NA Sheen *NA <br /> • MW-48 ND 0.19 *NA <br /> MW-50 NA 30.23 NA <br /> MW-52 0.02 Sheen NA <br /> Definitions: <br /> ND = SPH or sheen; not observed. <br /> NA = Not applicable/Not available <br /> * = SPH removal occurred prior to groundwater sampling. <br /> SPH removal activities are scheduled to be conducted quarterly (at a minimum) for on and off <br /> Site wells which repeatedly contain measurable thickness of SPH. It should be noted that these <br /> SPH removal activities are typically performed between quarterly monitoring events (as noted <br /> on the table), and are likely to influence reported SPH thickness. Wells MW-43, MW-47, and <br /> MW-50 could not be accessed for sampling during 4007 due to access agreement <br /> renegotiations with the current property owner; thus, no comparisons or differences could be <br /> made between 4Q07 and 1Q08. <br /> 4.5.2.2 Fuel Oxygenates and Hydrocarbon Concentrations <br /> A summary of first quarter 2008 deep zone concentration trends of TPHg, TPHd, TPHo, <br /> benzene, MtBE, and TBA in comparison to results reported during the previous quarter are <br /> presented in the table below. Deep zone wells MW-42 and MW-51 were not sampled during the <br /> third and fourth quarters 2007 due to renegotiations of the off site access agreements with the <br /> property owners and could not be compared to previous quarter data. Values in parentheses <br /> • represent number of detections and non-detects that were reported in the fourth quarter 2007. <br /> 1Q08QSSRQRSRQMR.Final.doc 24 April 30,2008 <br /> 77TW.26397.42.1307 <br />