2012-06-20_PERMIT FILE - C2010089 (85)

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Probable Hydrologic consequences Ground Water (Cont.) 5. Impact of spoil water quality on ground and surface water quality. Surface Water 1. Effects of mining on the local geomorphology. 2. Effects of sediment ponds on channel characteristics and downstream users. TABLE 2.05.6(3) -2a (cont.) CONSEQUENCES OF THE LIFE -OF -MINE MINING PLAN FOR THE NEW HORIZON MINING AREA Analysis Results Geochemical controls on water quality suggest that the water chemistry and concentrations of most elements of concern are controlled by mineralogic reactions that will resist changes in water chemistry. Irrigation water will enter the spoil and will increase in TDS and will discharge from spoil springs but the quality will be essentially the same as the current overburden water quality. This will occur for at least hundreds of years and the spoil water quality will gradually improve to the quality of the irrigation water as pyrite is oxidized and dissolved solids are flushed out. Meehan Draw and Glasier Draw will not be disturbed. The lengths and gradients of the streams will not be affected. Watershed areas will remain the same, elevations and slopes will be reduced, and slope lengths and time of concentration will increase. Channel reaches below the frequently discharging ponds, may become more incised with active meandering channels and vegetation will encroach along the channel edges. AVF study indicates that the channels in Tuttle and Coal Canyon (and tributaries) are incised into bedrock, hence neither drainage is determined to have an AVF. Surface water and pumped pit water impounded by the sediment ponds and discharged will replace the irrigations return water flows to the drainages. Significance No indication of significant long or short term impacts to the local ground water quality. Impact to San Miguel water quality is of little significance. Impacts to Tuttle Draw water quality are measurable, but are of little significance in terms of water use. See detailed discussion in Probable Hydrologic Consequences under Item 5) Potential impacts of replaced spoil on groundwater quality Watershed impacts will be mitigated by contour ripping, mulching and prompt revegetation. The watershed impacts are expected to be very minimal. Once full reclamation is done on the NHN area by 2019, the site will have no impact on the local geomorphology. Long term channel impacts until bond release followed by short term channel readjustment period when ponds are removed. Impacts are of minimal significance and increased vegetation should help control sediment during channel readjustment period. No mitigation is necessary for AVF's (negative determination). WFC has water rights to more water than required for mining related uses. An augmentation plan has been developed for mitigating any impacts proven on downstream users.