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ameO <br /> • TPH-diesel using EPA Method 8015M; <br /> • total and dissolved Cr using EPA Method 601013; and <br /> • dissolved Cr VI using EPA Method 7199. <br /> Samples analyzed for dissolved metals were filtered by the analytical laboratory prior to <br /> analysis. <br /> Groundwater purged from the wells was stored in 55-gallon drums. The drums containing <br /> purge water and equipment decontamination fluids were labeled and stored at each Facility for <br /> handling by MonierLifetile. <br /> 3.2 FIELD QUALITY ASSURANCE/QUALITY CONTROL SAMPLES <br /> Quality assurance/quality control (QA/QC) procedures were implemented during the <br /> semi-annual sampling event with the collection of one blind duplicate groundwater sample <br /> at each Facility: one from well LPW-3 (sample identification LP-D-082510) and one from well <br /> FCW-2 (sample identification FC-D-082610). Each duplicate sample was collected and <br /> handled in the same manner as the other groundwater samples. The duplicate groundwater <br /> samples were analyzed for TPH-diesel, total and dissolved Cr, and dissolved Cr VI. <br /> Additional groundwater samples were collected from monitoring wells LPW-2 and FCW-2 for <br /> the laboratory preparation of matrix spike/matrix spike duplicate (MS/MSD) samples. <br /> 4.0 GROUNDWATER MONITORING RESULTS <br /> This section presents the results of groundwater monitoring activities conducted at the <br /> Facilities in August 2010. Groundwater analytical data are compared to historical data, the <br /> WQG for TPH-diesel of 100 pg/L (Marshack, 2001), and the CDPH MCL for Cr and Cr VI of <br /> 50 pg/L. <br /> 4.1 GROUNDWATER GRADIENT AND FLOW DIRECTION <br /> The following subsections present groundwater flow direction and gradient results from the <br /> groundwater monitoring activities for each Facility. Water level measurements and <br /> groundwater elevation data are presented in Table 1. <br /> 4.1.1 Lathrop Facility <br /> During the August 2010 monitoring event, groundwater was encountered at elevations of <br /> 2.13 feet below mean sea level (bmsl) in well LPW-1 (cross-gradient well), 2.67 feet bmsl in <br /> AMSC Geomatrix, Inc. <br /> PA10626.000.0\Docs\Semi-Annua1 Groundwater Monitoring&Sampling\Semi-Annual 1-10 6 <br />