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Table 2.05.6.(3)-1 <br />Summary of Consequences of the Life -of -Mine Mining Plan for the New Horizon Mining Area <br />July 2016 (TR -74) 2.05.6(3)-13 <br />Probable Hydrologic Consequences <br />Analysis Results <br />Significance <br />Surface <br />Water <br />1 <br />Effects of mining on the local <br />A stream channel course has been altered, the length has been <br />Adequate reclamation and channel design has resulted in a stable <br />geomorphology <br />reduced, and the overall gradient will be slightly increased after <br />channel. Monitoring conducted in the channel since 1980 indicates <br />the removal of the 001 pond. Watershed areas will increase, <br />no additional contributions of suspended sediment. Watershed <br />elevations and slopes will be reduced, and slope lengths and time of <br />impacts will be mitigated by contour ripping, mulching and <br />concentration will increase. <br />prompt revegetation. The watershed impacts are expected to be <br />very minimal. Once full reclamation is done on the property by <br />2014, the site will have no impact on the local geomorphology. <br />2 <br />Effects of sediment ponds on channel <br />Channel reaches below the frequently discharging ponds, will <br />Long term channel impacts until bond release followed by short <br />characteristics and downstream users. <br />become incised with active meandering channels and vegetation <br />term channel readjustment period when ponds are removed. <br />will encroach along the channel edges. AVF study indicates that <br />Impacts are of minimal significance and increased vegetation <br />the channels in Tuttle and Calamity Draws are too incised for flood <br />should help control sediment during channel readjustment <br />irrigation hence neither Draw is determined to be an AVF. <br />period. No mitigation is necessary for AVF's (negative <br />Surface water impounded by the sediment ponds may affect water <br />determination). WFC has water rights to more water than <br />rights downstream. <br />required for mining related uses. An augmentation plan has <br />been developed for mitigating any impacts proven on <br />downstream users. <br />3 <br />Effects of sediment pond <br />Sediment ponds designed for 10 -year, 24-hour events. Historic <br />Sediment pond discharge impacts will be negligible because <br />discharges, diversions and culverts at <br />NPDES monitoring have only resulted in one exceedences of TSS. <br />discharges will meet NPDES permit limits. Diversions and <br />road crossings on surface water <br />No exceedences of any other required parameter has been <br />culvert impacts will be negligible because they have been <br />quality. <br />observed. Diversions and culverts are designed to adequately <br />designed to minimize erosion and to protect the hydrologic <br />convey runoff through and around disturbed areas without <br />balance. <br />contributing additional suspended sediment. <br />4 <br />Effects of runoff from reclaimed areas <br />Reduced runoff rates and volumes, and lower sediment <br />Impacts due to reduced runoff will be negligible due to the <br />on the quality of streamflow. <br />concentrations and yields. Possible large reductions in runoff due to <br />relatively small reclaimed basin sizes. Flow in the vicinity of <br />lower slopes and longer hydraulic lengths. Lower slopes and <br />both mining areas is dominated by irrigation return water, not <br />reclamation practices will result in reduced sediment loads. <br />runoff. <br />5 <br />Effects of runoff from reclaimed areas <br />Reclaimed area runoff water will be suitable for livestock <br />No short or long term significant impacts. <br />on the quality of streamflow. <br />drinking water. Runoff from reclaimed areas as measured at <br />NPDES 001 has not degraded the quality of water of receiving <br />streams. <br />July 2016 (TR -74) 2.05.6(3)-13 <br />