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' 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 well MW004 and in the <br />two production supply wells DW001 and DW002. 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 />Similar to gross alpha, combined radium 226 and 228 activities exceed the 5 pCi/L <br />Colorado groundwater standard in well MW004 and in both production wells. <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 />i GCC facility. <br />Field Parameters <br />' Field parameters including temperature, pH, and conductivity were collected during the <br />March 25, 2008 sampling. These instruments were not available on the April 15, 2008 <br />' sampling. The data collected indicate that pH at the site is very close to neutral. <br />Conductivity is highest in the alluvial wells where some turbidity was noted. <br />Conductivity is considerably lower in the production wells, where turbidity was absent. <br />' The water temperature in the production well was more than twice that of the shallow <br />alluvial wells indicating cool runoff conditions in the shallow wells compared to those in <br />the deep aquifer. <br />Quality Control <br />One set of field duplicate samples was collected during the monitoring event. Sample <br />Dup-01 was submitted as a blind field duplicate of primary production well sample <br />DW002. Precision between the results of the primary and duplicate samples was very <br />' good for all parameters tested. <br />All laboratory data packages were reviewed to ensure that quality control elements <br />' (holding times, blanks, control samples, and matrix spikes), impacting precision and <br />accuracy of the groundwater results presented were within appropriate control limits. <br />5