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CvvATC A S S 0 C I A T E S I N C northeast and south-southeast Figure 3 depicts groundwater elevation contours for January 21, 2004 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 January 21, 2004 were submitted to Excelchem Environmental Labs (FLAP 92119) in Roseville, California for analyses 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 MW1 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/I) The reported hexavalent chromium concentration in the groundwater sample collected from MW-3 was 2 8 mg/l The reported hexavalent chromium concentration in the groundwater sample collected from MW-6 was 0 066 mg/1 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 chronuurn 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 3 0 mg/l The reported total chromium concentration in the groundwater sample collected from MW-6 was 0 080 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 MWI through MW9 and FW ranged from 410 to 760 mg/l with the highest concentration detected in the groundwater sample collected from MW-2 Dissolved oxygen concentrations ranged from 0 93 mg/1 to 8 22 mg/l with the lughest concentration measured in MW-3 Analytical results are summarized in Tables 2 and 3 Laboratory data sheets and chain-of- custody documentation are provided in Attachment 2 • s lenvironmentall625831quarterly"gr-2004 doc 2