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amecIO <br /> Groundwater samples were successfully collected from each well during the August 2010 <br /> groundwater monitoring event. The groundwater samples collected on August 25 and 26, <br /> 2010 were analyzed within the method holding times for each well. <br /> 5.0 SUMMARY <br /> This section presents a brief summary of the results from the groundwater monitoring activities <br /> conducted at the Facilities in August 2010. <br /> Lathrop Facility <br /> • Groundwater elevations measured in August 2010 ranged from 0.94 feet bmsl to <br /> 2.67 feet bmsl. The calculated groundwater elevations were within the range of <br /> historical elevations calculated for this Facility. The groundwater gradient at this <br /> Facility was calculated at 0.004 ft/ft with a flow direction to the north-northeast, <br /> similar to historical gradients and flow directions for this Facility. <br /> • Diesel-range total petroleum hydrocarbons were not detected above the laboratory <br /> reporting limit of 50 pg/L in the groundwater samples from all three monitoring wells <br /> (LPW-1, LPW-2, and LPW-3), which is consistent with the eight monitoring events <br /> conducted since November 2007 at this Facility. <br /> • Total Cr and dissolved Cr concentrations were detected below the respective <br /> CDPH MCL (50 pg/L) in groundwater samples from all three monitoring wells. <br /> Concentrations of total Cr were observed at 31 pg/L, 29 pg/L, and 3.2J pg/L <br /> (LPW-3 duplicate at 3.OJ pg/L) in wells LPW-1, LPW-2, and LPW-3, respectively. <br /> Concentrations of dissolved Cr were observed at 20 pg/L and 12 pg/L in wells <br /> LPW-1 and LPW-2, respectively. Dissolved Cr was not detected above the <br /> laboratory reporting limit of 10 pg/L in the groundwater sample from well LPW-3. <br /> Groundwater sample results for total and dissolved Cr were within the range of <br /> concentrations detected during previous events. <br /> • Dissolved Cr VI concentrations were detected below the CDPH MCL (50 pg/L) in <br /> groundwater samples from all three wells at concentrations between 4.9 pg/L <br /> (LPW-3 duplicate) and 19 pg/L. Groundwater sample results were within the range <br /> of historical Cr VI concentrations for these wells. <br /> • No metals were detected above the CDPH MCL of 50 pg/L for Cr during this <br /> monitoring event. <br /> AMEC Geomatrix, Inc. <br /> PA10626.000.00ocs\Semi-Annual Groundwater Monitoring&Sampling\Semi-Annual 1-10 11 <br />