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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> samples exceed concentrations at well MW-SUN3 for the radiological parameters, where data <br /> are available. <br /> Time-concentration plots of 14 selected groundwater constituents are plotted and presented in <br /> Appendix C for the monitoring wells and the sampled underground locations. Minimum and <br /> maximum concentrations for selected analytes at the various sample locations are also <br /> presented in Appendix C. Trends in concentrations with time are evident for some constituents. <br /> These trends and other perturbations in concentrations in a given well may be associated with <br /> residual well drilling and well development influences as well as natural chemical stratification in <br /> the well over time. Well sampling procedures have been consistent. Some deviations in <br /> constituent concentrations may have occurred due to laboratory errors or how detection limits <br /> were set for some data, but the bulk of the data is considered viable and of good quality. <br /> For some constituents, a trend may be implied because of the time gap in sampling events <br /> between September 2014 and February 2020. Continued monitoring will provide insight as to <br /> actual concentration behavior with time. Results for some constituents show relatively small <br /> variations in concentration with time, e.g., TDS, sodium, sulfate, and uranium. Several of the <br /> plots show distinct patterns in concentration trends over time including total alkalinity, boron, <br /> fluoride and potassium. For boron and fluoride, early sampling events showed concentrations <br /> that were relatively low and then increased and perhaps stabilized. Total alkalinity and <br /> potassium may be showing an opposite trend. <br /> There are a number of physicochemical conditions that may explain variations in constituent <br /> concentrations from one sampling event to another. It is possible that sample results during <br /> early events may not truly represent constituent background because of drilling impacts to the <br /> formation and the low permeability of the Top Rim unit prevents rapid flushing of the well bore. <br /> Because of the confined condition and overall depth and low permeability of the Salt Wash <br /> Member, it is unlikely that seasonable fluctuations in aquifer flux occur that would affect <br /> constituent concentrations. Continued sampling would provide more insight as to natural <br /> chemical fluctuations in the monitoring wells. <br /> Groundwater Classified Use <br /> Groundwater in the Top Rim unit potentially downgradient of the SMC and underlying <br /> Disappointment Valley has not historically been used for domestic or agricultural use. Under <br /> regulation 5 CCR 1002-41.4(B), groundwater in the Salt Wash Member in this area would likely <br /> Western Water& Land, Inc. 49 <br />