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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 equal or exceed <br />the Colorado groundwater standard of 15 picoCuries/Liter (pCi/L) in wells MW004, <br />MW002, and Dup-01 (MW002 duplicate sample). The 15 pCi/L standard excludes <br />activities due to radon and uranium. Radon and uranium activities were not measured, <br />and the gross alpha contribution from these two sources cannot be evaluated at this time. <br />Gross alpha activities were lower in well MWO04 (72 versus 37 pCi/L) and higher in well <br />MWO02 (7.1 versus 15 pCi/L) in the second quarter, relative to the first quarter. <br />The combined radium 226 and 228 activities did not exceed the 5 pCi/L Colorado <br />groundwater standard in any wells. This standard was exceeded for well MWO04 in the <br />in the first quarter 2008 event. <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 masses 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 />the likely cause of the elevated gross alpha activities in the Dakota aquifer beneath the <br />GCC facility. <br />Field Parameters <br />Field parameters including temperature, pH, and conductivity were collected during the <br />July, 2008 sampling. The data collected indicate that pH at the site is very close to <br />neutral. Conductivity is highest in the alluvial wells where some turbidity was noted. <br />3