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1 <br /> 4 MAY 1999 GROUNDWATER MONITORING <br /> Philip performed quarterly groundwater monitoring on May 28, 1999 Depth to <br /> groundwater and the presence or absence of phase separated hydrocarbons (PSH) <br /> i were evaluated in each monitoring well PSH was not observed in any of the <br /> 1 monitoring wells <br /> t� Groundwater samples were collected from monitoring wells MW-1 through MW-13 <br /> 1 Groundwater sampling procedures are described In Appendix 3 <br /> Groundwater samples were submitted under proper chain of custody control to <br /> Acculabs Samples were analyzed for TPH-G, BTEX, and oxygenate compounds <br /> Laboratory analytical reports are contained in Appendix 4, and monitoring results are <br /> summarized in the following sections <br /> 4.1 Groundwater Elevation Data <br /> Groundwater elevations measured in facility monitoring wells on May 28, <br /> 1999 (summarized in Table 1),ranged from minus (-)19 04 to---20 72 feet <br /> MSL Groundwater levels in the wells increased approximately 2 to 3 feet <br /> from the previous monitoring event in October 1998 As shown in Figure 3, <br /> the groundwater flow direction is northeasterly (approximately N77E) at a <br /> gradient of about 3 3x 10"3 foot per foot, which is consistent with historic <br /> trends <br /> 4.2 Groundwater Sample Analytical Data <br /> BTEX and TPH-G concentrations were only measured in samples collected <br /> from monitoring wells MW-1, MW-10, MW-12, and MW-13 Petroleum <br /> concentrations were not detected in samples collected from the other <br /> monitoring wells <br /> The benzene concentration in the well MW-1 sample was measured at 240 <br /> µg/L, which is slightly higher than 170 µg/L that was measured in October <br /> 1998, but significantly lower than the high of 6,800 µg/L measured in July <br /> 1987 Benzene was measured at 2 8 µg/L and 18 µg/L in the samples <br /> collected from wells MW-10 and MW-12, respectively <br /> The TPH-G concentration in the well MW-1 sample was measured at <br /> 17,000 pg/L, again higher than 16,000 µg/L measured in October 1998, but <br /> lower than 196,000 µg/L measured in April 1993 TPH-G concentrations in <br /> May 1999 Subsurface investigation and Groundwater Monitoring Report <br /> The Earthgrams Company Facility <br /> 2651 South Airport Way <br /> Stockton,CaliforniaPrepared for THEEARTHGRAINS COMPANY Prepared by Philip Services Corp <br /> E\121382u21382EGu25997W99REP DOC June 22, 1999 <br /> 9 <br />