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Arcady ,0il Company . -3- • 30 August 1989 <br /> Sulfate concentrations were inconsistent between samples. The highest sulfate <br /> concentrations was found in samples from an upgradient and a downgradient monitoring <br /> well . M-4 and M-8 each had 197 mg/L of sulfate. The reported sulfate concentration <br /> in the sample from M-3 was 2.1 mg/L. This result seems erroneous. Tony Nurse, <br /> owner of Sierra Foothill Laboratory, suggested that there may be something in the <br /> sample which interferes with the analysis. He said that the sample was analyzed a <br /> second time at a different dilution with similar results. Mr. Nurse still feels <br /> that the reported concentration of sulfate is not the true concentration in the <br /> sample. <br /> The results of the minerals analyses for all the analyses in Table 1 are plotted on <br /> a Piper diagram, labeled figure 3. The plot indicates that the mineral origin of <br /> water in the supply wells is similar to the water in the monitoring wells. This may <br /> indicate that the ground water near the drilling mud disposal site is affected only <br /> slightly by the presence of the waste. <br /> Table 2 and 3 summarize the results of trace metals analyses on filtered and <br /> unfiltered water samples. <br /> In the past chromium and arsenic were constituents of concern at this site. Metals <br /> analyses of filtered ground water samples did not show any arsenic in the samples <br /> greater than the detection limit of 0.005 mg/L. Chromium was found in M-4, an <br /> upgradient well and M-5, a downgradient well at a concentration of 0. 12 mg/L. The <br /> chromium concentration in M-3 and M-8 was less than 0.05 mg/L. <br /> Lead and copper were found at hazardous levels in some waste samples from the site. <br /> Lead was found in both the filtered and unfiltered samples from the upgradient <br /> wells, but not in either set of samples from the downgradient wells. The <br /> concentration of lead in filtered samples from M-3 and M-4 was 0.01 mg/L. The <br /> concentration of lead in all samples from M-5 and M-8 was less than 0.005 mg/L. <br /> Central Coast Analytical Services reported higher concentrations of copper, iron, <br /> manganese, and zinc in samples than Sierra Foothill Laboratory. Samples sent to <br /> Central Coast were preserved with nitric acid while samples sent to Sierra Foothill <br /> were not. The acidified samples, however, contained roughly similar concentrations <br /> of calcium, magnesium, potassium, and sodium to the non-preserved samples. <br /> CONCLUSION <br /> In general samples from the downgradient monitoring wells, M-5 and M-8, did not <br /> contain significantly higher levels of minerals or trace metals than samples from <br /> the upgradient monitoring wells, M-3 and M-4. Lead and copper were found at <br /> hazardous levels in solid samples from the site, and chroq* and arsenic were <br /> identified as constituents of concern while the site was fOO" eration. The levels <br /> of arsenic, chromium, lead, and copper in samples from monitoring wells, however, do <br /> not exceed the drinking water standards in the samples collected during this <br /> inspection. <br /> Water in all the wells is of fair to poor quality with regard to human consumption. <br /> Water ceeda grj ary,,Oxjaking water standards for aluminum. <br /> The wa er exceeds secondary drinking water standards for iron and manganese. Water <br /> in nearby supply wells is also of fair to poor quality, and is similar in chemistry <br /> to the water in the monitoring wells as shown by figure 3. <br /> The upgradient wells, M-3 and M-4, are within twenty feet of the drilling mud, and <br /> may be affected by leachate from the waste due to their proximity to the waste. <br />