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CVYA TC A S S O C I A T E S I N C f with an average magnitude of 0.001 fl/ft. This appears to be within historicalP arameters which have indicated the predominant groundwater gradient direction is to the east with variation between northeast and south-southeast. Figure 3 depicts groundwater elevation contours for April 22, 2003. The groundwater monitoring data are summarized in Table 1. Monitoring data and purge logs are provided in Attachment 1. LABORATORY ANALYSIS The groundwater samples collected on April 22, 2003 were submitted to Excelchem Environmental Labs (FLAP #2119) in Roseville, California for analysis of: hexavalent chromium using EPA method 7199; total chromium using EPA method 200.7; and total hardness as CaCO3 by method SM2340C. Hexavalent chromium was not present above laboratory detection limits in the sample collected from the facility well. Hexavalent chromium was detected in monitoring well MW-3 and MW-6 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 well MW-3 was 3.8 mg/l. The reported hexavalent chromium concentration in well MW-6 was 0.075 mg/l. Hexavalent chromium was also detected in water samples from wells MW-1, MW-2, MW4, MW-5, MW-7, and MW8 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 monitoring well MW3 and MW6 above the California Primary MCL for total chromium in drinking water of 0.05. mg/l. The reported total chromium concentration in well MW3 was 3.7 mg/l. The reported total chromium concentration in well MW6 was 0.082 mg/l. Total chromium was also detected in water samples from wells MW1, MW2, MW4, MW5, MW7, and MW8 but at concentrations below the respective MCL for total chromium. Total chromium was not present above laboratory detection limits in the water sample collected from the facility well. Hardness as a measure of calcium carbonate in wells MWl through MW8 and the former facility well ranged from 340 to 880 mg/1 with the highest concentration detected in well MW3. Dissolved oxygen concentrations ranged from 1.43 to 7.89 with the highest concentration measured in well MW3. Analytical results are summarized in Tables 2 and 3. Laboratory data sheets and chain-of-custody documentation are provided in Attachment 2. I DISCUSSION AND CONCLUSIONS Based on a review of previous work performed at this site and the data presented in this report, it can be concluded that groundwater gradient direction have been generally consistent with historical data. The groundwater samples collected from monitoring wells MW 1 MW2, MW4, MW5, MW7, and MW8 contained concentrations of hexavalent chromium at levels above the laboratory method detection limit but below the California Primary MCL for total chromium. Only the samples collected from MW3 and MW6 contained hexavalent chromium in excess of the w:1625831quart1yl2gr-2003.doc 2 Is