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I v ATC A S S O C I A T E S I N C • indicated the predominant groundwater gradient direction is to the east with variation between northeast and south-southeast Figure 3 depicts groundwater elevation contours for October 22, 2003 The groundwater monitoring data are summarized in Table 1 Monitoring data and purge logs are provided in Attachment 1 LABORATORY ANALYSES The groundwater samples collected on October 22, 2003 were submitted to Excelchem Environmental Labs (ELAP #2119) in Roseville, California for analysis of hexavalent chromium using EPA Method 7199, total chromium using EPA Method 6010B, and total hardness as CaCO3 by method SM2340C Hexavalent chromium was not present above laboratory detection limits in the samples collected from well MWl or the facility well Hexavalent chromium was detected in the groundwater samples collected from monitoring wells MW-3 and MW-6 at concentrations above the California Primary Maximum Contaminant Level (MCL) for total chromium in drinking water of 0 05 milligrams per liter (mg/1) The reported hexavalent chromium concentration in the groundwater sample collected from MW-3 was 4 4 mg/l The reported hexavalent chromium concentration in the groundwater sample collected from MW-6 was 0 066 mg/l Hexavalent chromium was also detected in water samples collected from wells MW-2, MW-4, MW-5, MW- 7, MW-8, and MW-9, but at concentrations below the MCL for total chromium The distribution of hexavalent chromium in groundwater is shown on Figure 4 Total chromium was detected in the groundwater samples collected from MW-3 and MW-6 above the California Primary MCL for total chromium in drinking water of 0 05 mg/1 The reported total chromium concentration in the groundwater sample collected from MW-3 was 4 3 mg/1 The reported total chromium concentration in the groundwater sample collected from MW-6 was 0 077 mg/l Total chromium was also detected in water samples from wells MW-2, MW-4, MW-5, MW-7, MW-8, and MW-9 but at concentrations below the respective MCL for total chromium Total chromium was not present above laboratory detection limits in the water samples collected from MW-1 or the facility well Hardness as a measure of calcium carbonate in the groundwater samples collected from MW1 through MW9 and FW ranged from 350 to 820 mg/l with the highest concentration detected in the groundwater sample collected from MW-3 Dissolved oxygen concentrations ranged from 0 88 mg/1 to 8 89 mg/l with the highest concentration measured in MW-8 Analytical results are summarized in Tables 2 and 3 Laboratory data sheets and chain-of- custody documentation are provided in Attachment 2 5 Ienvironmental1625831quar[erlyl4gr-2003 doe 2