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16 <br /> Previous investigations have identified low concentrations of Title 22 metals in ground water <br /> samples from wens on either portion of the sire. however, the resaim from those <br /> investigations have been quite variable. Only two constituents exhibited concentrations <br /> above primary MCLS during each of the previous sampling investigations: arsenic, in well <br /> MW4, and selenium, in well MW1 (WaterWork, January 1990; RESNA, May and <br /> September 1992). Comparison of the concentrations of these and other metals in ground <br /> water to additional sites in the Stockton area, and to ground-water data available from <br /> federal, state and local agency date bases, suggests that elevated concentrations of selected <br /> metals in shallow ground water occur regionally and may not be the result of historic site <br /> activities (RESNA, September 1992). The concentrations of arsenic and selenium in the site <br /> soil samples are within the range of typical soil metal concentrations (Kabata-Pendias and <br /> Pendias, 1984). This suggests that the elevated levels of these two metals in ground water <br /> beneath the site did not result from historic site activities. <br />