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development of impacts, if any should develop. Well GP -09 has been designated <br />the groundwater point of compliance for the Third White Sandstone aquifer, and <br />the Coy well is the point of compliance for the Flume Gulch alluvium. <br />No new or revised water monitoring is being proposed under RN7. <br />E. Probable Hydrologic Consequences <br />The model for leachate formation and migration at the Trapper Mine is based on <br />a study conducted by the U.S. Geological Survey at the Seneca II Mine in Routt <br />County, approximately 14 miles east of the Trapper Mine (U.S. Geological <br />Survey Water Resources Investigations Report 92-4187). The model is described <br />in the probable hydrologic consequences of the permit application (Section 4.8). <br />No drawdowns have been detected in aquifer wells within one mile from the <br />permit boundary. Observed draw -downs have been temporary and are limited to <br />the immediate vicinity of the pits. The operator expects such limited draw -downs <br />to continue with future mining. <br />The proposed mining operation will have little if any effects on the post -mining <br />recharge capacity. The applicant's studies concluded that the recharge capacity of <br />the reclaimed spoils will actually be slightly higher than the pre -mine condition. <br />The mine activities should not impact any regional aquifers except the Third <br />White Sandstone. Mined strata dip far beneath the Yampa River alluvial aquifer <br />and communication between these strata and the alluvial aquifer is negligible. <br />Permit section 4.8.2.2 discusses potential drawdown impacts to adjacent wells. A <br />groundwater monitoring program is discussed in section 4.8.3.2 of the permit. <br />Point of compliance wells are in place. <br />Surface Water Impacts <br />The most noticeable change in surface water quality resulting from mining <br />activities constitutes increased levels of total dissolved solids (TDS). TMI expects <br />higher TDS in some surface water runoff for a few years after reclamation in <br />an area. The higher TDS levels will occur periodically when the contribution <br />from precipitation and snowmelt is at a minimum (base flow conditions). <br />Conductivity, TDS and major constituents tend to increase as the ground water <br />contribution comprises a larger portion of flow. For a detailed analysis of surface <br />water impacts, the 2016 Annual Hydrology Report, Section 2.5 of the permit <br />presents the most current information. <br />Leachate that may discharge from the toe of the Horse Gulch Fill probably will <br />cause an increase in the dissolved solids content of natural stream flows in <br />Horse Gulch. Rain or snowmelt provides most natural surface water flows in <br />Page 18 <br />Trapper RN7 Prepared by: R. Reilley <br />Nov 2017 <br />