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E. Probable Hydrologic Consequences <br /> The model for leachate formation and migration at the Trapper Mine is based on a <br /> study conducted by the U.S. Geological Survey at the Seneca II Mine in Routt County, <br /> approximately 14 miles east of the Trapper Mine (U.S. Geological Survey Water <br /> Resources Investigations Report 92-4187). The model is described in the probable <br /> hydrologic consequences of the permit application (Section 4.8). <br /> No drawdowns have been detected in aquifer wells within one mile from the permit <br /> boundary. Observed drawdowns have been temporary and are limited to the <br /> immediate vicinity of the pits. The operator expects such limited drawdowns to <br /> 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 the <br /> reclaimed spoils will actually be slightly higher than the pre-mine condition. The <br /> mine activities should not impact any regional aquifers except the Third White <br /> Sandstone. Mined strata dip far beneath the Yampa River alluvial aquifer and <br /> 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. Point <br /> of compliance wells are in place. <br /> Surface Water Impacts <br /> Surface water flow and quality are monitored in the Flume System, Johnson Gulch, <br /> No Name Gulch, Ute Gulch, Pyeatt System, Oak, Gulch, Horse Gulch and Deal <br /> Gulch. Generally, Johnson, No Name East Pyeatt and Middle Flume gulches exhibit <br /> flow over the course of the year. The most noticeable change in surface water quality <br /> resulting from mining activities constitutes increased levels of total dissolved solids <br /> (TDS). TMI expects higher TDS in some surface water runoff for a few years after <br /> reclamation in an area. Increased TDS levels 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 2021 Annual Hydrology Report, Section 2.5 of the permit presents <br /> the most current information. <br /> Leachate that may discharge from the toe of the Horse Gulch Fill probably will cause <br /> an increase in the dissolved solids content of natural stream flows in Horse Gulch. <br /> Rain or snowmelt provides most natural surface water flows in Horse Gulch. <br /> Although loading of Horse Gulch surface flows with dissolved solids from the fill <br /> would be a local impact, it does not rise to the level of material damage because use or <br /> potential use is not likely to be impaired. An exceedance of an instream standard in <br /> Horse Gulch is unlikely because leachate from the fill will probably be alkaline (like <br /> all other Trapper leachates) and is not likely to contain high concentrations of the <br /> 16 <br />