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General chemistry parameters do not have primary health based standards. Fluoride, <br />chloride, and sulfate have secondary or agricultural standards. The sulfate <br />' concentrations in all of the wells sampled exceed the secondary domestic drinking water <br />standard of 250 mg/L. Excess sulfate in drinking water may have negative aesthetic <br />impacts such as laxative effects. <br />Well MWO04 stands out with the highest sulfate, TDS, and nitrate concentrations. <br />MWO04 is located in the most extensive flood plain setting of the three alluvial wells, and <br />may be subject to more saturated geochemical conditions, relative to the other two <br />alluvial wells. <br />Radiochemistry <br />Results of the radiochemistry analyses show that gross alpha activities exceed the <br />Colorado groundwater standard of 15 picoCuries/Liter (pCi/L) in wells MW002, <br />MW003, MW004, and Dup-01 (MW002 duplicate sample). The 15 pCi/L standard <br />excludes activities due to radon and uranium. Radon and uranium activities were not <br />measured, and the gross alpha contribution from these two sources cannot be evaluated at <br />this time. The November 2008 sampling event also had gross alpha activities exceeding <br />the 15 pCi/L standard in all three shallow groundwater wells. <br />The combined radium 226 and 228 activity exceeded the 5 <br />ty pCi/L Colorado groundwater <br />standard in MW004, as it has in the previous two monitoring events. ? <br />There is no indication that any plant activities are responsible for elevated radiochemistry <br />activities at the GCC Facility. Elevated radionuclide activities in Colorado aquifers are <br />generally associated with leaching from granitic bedrock masse that underlay many <br />aquifers in the state. The Dakota formation in the Denver basin, which extends from` <br />pueblo to Wyoming, is also host to minor Uranium roll front deposits. These deposits <br />form when groundwater containing dissolved uranium comes into contact with reducing <br />conditions, causing precipitation of the Uranium. Such naturally occurring conditions are <br />/ <br />the likely cause of the elevated gross alpha activities in the Dakota aquifer beneath the <br />GCC facility. <br />3