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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 alluvial well sample MW002. <br />Precision between the results of the primary and duplicate samples was very good for all <br />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 />Data from the contract laboratories was found to be acceptable in terms of data quality <br />and industry standard presentation. <br />CONCLUSIONS <br />Results of the Second Quarter 2008 groundwater sampling performed at the GCC Rio <br />Grande site during July 2008 are presented herein. All analyses required were performed <br />as requested. <br />Results for several dissolved metals were found to be non-detect for all wells. These <br />metals were also reported as non-detect in the first quarterly event. If these constituents <br />continue to be non-detected in future samplings events, or if these have not been <br />historically detected, GCC Rio Grande may petition to have these constituents removed <br />from the routine monitoring program. <br />Selenium was the only metal to exceed a primary drinking water standard. This occurred <br />at well MW004. This result appeared to be anomalous and will be further evaluated in <br />future monitoring events. <br />Secondary water quality standards were exceeded for dissolved manganese and for <br />sulfate. These constituents may have negative aesthetic impacts on water used for <br />domestic purposes. <br />Elevated radiochemical activities are likely associated with naturally occurring conditions <br />in the Dakota aquifer. <br />4