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• alluvial, overburden coal and underburden monitoring wells, respectively. Water level fluctuations <br />Mining impacts on ground water quality will be compared against the multiple year baseline <br />monitoring ranges established for each chemical parameter monitored at each site. Because a <br />number of variables can affect water chemistry, only significant increases or consistent trends will <br />be considered as possible impacts from mining. Trilinear and Schoeller diagram plots of well water <br />chemistry will also be evaluated to identify water qualify changes or degradation Vends. <br />as a result of irrigation, natural and water quality sampling stresses have been reasonably defined. <br />Significant water level drops outside these multiple year ranges will be considered to be possible <br />effects from pit pumpage. Water level drops in monitoring wells outside the projected zones of pit <br />pumpage drawdown will be considered suspect unless a consistent deepening Vend develops. <br />boring Flows and Quality. Spring flows and quality changes at spring monitoring sites will be <br />compared to ranges developed from multiple-year baseline monitoring data. Significant flow or <br />quality deviations from the multiple-yeaz ranges not explainable by climatic fluctuations will be <br />considered to suggest impacts from mining. <br />Introducfion. Determinations of the probable hydrologic consequences (PHC) of mining have been <br />• made by including detailed analyses of historical surface water quality data (see Tab 17, Probable <br />Hydrologic Consequences). Table 18-1 presents the surface water sites used to substantiate the <br />significance findings presented in the PHC analysis and for measuring potential future mining <br />impacts. The following section summarizes how future mining impacts on both surface water quality <br />and quantity will be evaluated using monitoring data collected at sites established in the Nucla Mine <br />mining areas. <br />Surface Water Quality. Future impacts on surface water quality will be evaluated by using Vending <br />analyses. Mining activities at the Nucla Mine began prior to the onset of collecting surface water <br />quality data (1979), hence, no Vue baseline data exists for comparison purposes. Regardless, the <br />significance of impacts will be evaluated by analyzing for prominent trends of changing chemical <br />concentrations over time. Consistently increasing concenVations of chemical parameters will be <br />considered to suggest mining impacts. Data collected at sites located above mining (most upstream) <br />along Tuttle (SW-N1) and Calamity Draws (proposed surface water monitoring site, see Tab 15, <br />Hydrologic Monitoring Program) will be used for investigating whether any future observed trends <br />are natural or result from mining. <br />• <br />18-4 <br />