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RULE 2 PERMITS <br />2.05.6 (3)(b)(i & ii) Hydrologic Controls <br />Rule 2.05.6(3)(b)(iii) requires determination of probable hydrologic consequences for the proposed <br />mining operations. This rule indicates that these consequences must be defined for both the permit area <br />and adjacent areas, for quantity and quality of surface water and groundwater. Baseline conditions must <br />be established, and possible impacts from the proposed activities must be anticipated. <br />Summary of Probable Hydrologic Consequences <br />An evaluation was made of potential hydrologic impacts of the proposed Collom mine to determine if the <br />potential impacts are likely to occur and if they would be significant. Based on the assessment of potential <br />impacts, the probable hydrologic consequences of the Collom Project as proposed in this application are: <br />Two springs mapped within the pit footprint and facilities area will be eliminated by mining. <br />Springs near the Collom pit might experience decreased flows during mining. Three additional <br />springs located in Little Collom Gulch north of the mine and spoil footprint area may have <br />reduced flows as a result of the mine dewatering activities. Significant impacts to other springs <br />are not anticipated. <br />Dewatering of the Collom pit is needed to achieve stable pit slopes for safe operating conditions <br />and will cause a drawdown in bedrock groundwater levels in the vicinity of the pit. Groundwater <br />levels are expected to recover after mining but may be at different levels than the pre -mining <br />groundwater. It is unlikely that the groundwater level in the pit backfill will reach a high enough <br />elevation to cause the discharge of spoil backfill groundwater at ground surface in Little Collom <br />Gulch. If this were to occur, it would not have a significant impact on the quantity or quality of <br />surface and subsurface flow in Little Collom Gulch. <br />The hydraulic conductivity within the backfilled pit is anticipated to be more uniform and higher <br />than the hydraulic conductivity of the individual geologic units in the adjacent unmined areas. <br />This will result in alternation of the bedrock groundwater flow gradient in the mine footprint area <br />and the immediate area surrounding the footprint. In general, the higher permeability of the spoil <br />backfill will result in a flatter groundwater gradient. Groundwater flow conditions in the areas <br />north of the pit are expected to be similar to the pre -mining groundwater flow conditions after re - <br />saturation of the spoil backfill. <br />No other statistically significant changes to surface water and groundwater quality or quantity are <br />anticipated. <br />The potential impacts that were evaluated and the resulting hydrologic consequences are discussed in the <br />following subsections. <br />Potential Impacts to Springs and Seeps <br />Springs in the Colowyo Mine area result from three general sources: 1) typified by a relatively deep soil <br />accumulation immediately upslope and shallow bedrock downslope of the point of discharge, 2) discharge <br />within valley bottom deposits, and 3) from sheer bedrock faces on hillsides (CDM 1985b). The first two <br />of these sources may mask or contribute to bedrock sources of the springs. The seeps and low volume <br />springs flow generally in response to snowpack accumulation and subsequent melting resulting in <br />seasonal flows. <br />Collom —Rule 2, Page 110 Revision Date: 11/16/16 <br />Revision No.: MR -166 <br />