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W. Prevention of <br />material damage <br />to the hydrologic <br />balance outside <br />the permit area <br />CDRMS <br />regulation <br />4.05.1(1) <br />Comment <br />Probable Hydrologic Consequences (PHC) predictions in <br />section 4.8.3 of Trapper's permit appear to be accurate. <br />Overall, PHC predictions appear to be accurate, as illustrated <br />by the following examples. <br />Per the PHC, TSS values in the surface water runoff are <br />expected to increase a few years after mining and then <br />decline. Data for NPDES sites 001 and 002 illustrate this <br />trend. <br />Per the PHC, elevated TDS levels will be detected in base <br />flows derived from backfill aquifers. During 2012, relatively <br />high TDS concentrations were reported for NPDES sites in <br />several gulches: Johnson, No Name, East Pyeatt, and Flume. <br />All four of these sites are downgradient of potential spoil <br />springs from the A Pit and East A Pit. In general, the data <br />reflect the inverse relationship between TDS and flow. <br />Per the PHC, post -mine values of pH in surface water runoff <br />are not expected to be significantly lower or higher than <br />present or pre -mine levels. Field pH values for all sites in <br />X. Agreement of <br />2012 were similar to previous data collected. <br />observed <br />CDRMS <br />hydrologic <br />io <br />regulatn <br />io <br />Comment <br />Per the PHC, Trapper does not anticipate recharge to the <br />impacts with <br />2.05. 6 <br />shallow aquifer systems to be adversely affected by mining <br />PHC projected in <br />operations in the Third White Sandstone. Water levels in <br />permit <br />wells GC -2, GP -9, and P -8 (used to monitor the Third White <br />Sandstone) did not rise or fall considerably between 2011 <br />and 2012. Previous analysis has indicated good recharge <br />with above average precipitation over the last few years. <br />Per the PHC, constituent concentrations in backfill aquifers, <br />namely TDS and sulfate, are expected to be higher than pre - <br />mining concentrations for an extended period of time after <br />mining. The data for TDS concentrations in wells in backfill <br />aquifers have shown apparent impacts from mining. TDS <br />concentrations in GD -3 and GF -5 are somewhat higher to <br />those of native aquifers in these areas. TDS values for wells <br />GF -7 and GF -11 were higher than the naturally observed <br />concentrations in the 1990s and 2000s, but have begun to <br />decline recent years. These trends have continued in 2012. <br />Sulfate concentrations exhibited similar trends as TDS for <br />wells GF -7 and GF -11. Sulfate concentrations increased in <br />GD -3 and GD -2 in 2011 and 2012, and should be watched <br />closely in future years. <br />Y. Adequacy of <br />CDRMS <br />groundwater <br />regulation <br />Yes <br />monitoring <br />4.05.13(1) <br />program <br />Page 8 <br />