2013-04-10_PERMIT FILE - C1981019 (82)

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RULE 2 PERMITS The West Fork of Jubb Creek is intermittent, and is only affected by a potential reduction in spring/seep source area by construction of the Collom Lite pit. Water infiltrating into reclaimed pit and spoil areas may later enter the West Fork of Jubb Creek via springs, if the elevation of the springs is below the final pit outflow elevation, and if the spring is connected to a stratigraphic interval that is exposed along the downgradient highwall of the reclaimed pit. The reclaimed pit outflow elevation is 7275 amsl, while the potentially affected springs are either located above this elevation, or have a source stratum which falls above this elevation where it intersects the highwall. Springs V 10 and V32 are located above the pit outflow, at elevations 7295 and 7600, respectively (based on 25 foot contours). Spring/seep V 1 is located at approximate elevation 7170, below the pit outflow, but is roughly 3200 feet from the pit disturbance boundary, not accounting for the highwall side slope. VI is generally down -dip from the pit, and the bedrock dips at roughly 8 percent. The spring's source layer must therefore intersect the highwall approximately 256 feet (3200 x 0.08) above the spring elevation, or roughly 7426 ft amsl. This is well above the pit outflow elevation. Therefore, water in contact with the overburden fill will not impact water quality in the West Fork of Jubb Creek, and will instead discharge to groundwater, generally within Little Collom Gulch. Potential for Spoil Spring Water Discharge Impacting Downstream Areas For Collom Lite, there are two separate ground water conditions in the mining area — the saturated groundwater zone and the unconfined perched aquifers above the deeper zone. The saturated ground water conditions exist below a depth of 7150feet (based on the 2005 WMC report). Any pitwall seepage from the 7150 feet level and below is to be expected since the ground water at this depth will be coming to equilibrium with the surrounding ground water levels (water table /piezometric surface) once dewatering ceases. The water beneath this piezometric /water table surface will flow in a northern direction at the rate of normal ground water flow for the area. Based on numerous previous studies in the area, this saturated water table level is at or below the bottom elevations of the creeks and gulches in the area of Collom Lite. This creates an outflow from the creeks to the ground water. With respect to spoil water quality, current water, rock, and soil quality analyses predominantly show a basic (a.k.a. base) environment, i.e., a pH above 7.0. This chemical environment has been present in this area since quality testing was initiated (and therefore, for some time in the past). Some adverse chemical conditions have been identified in the soils and overburden analyses; however, these have been discussed in the application and have been adequately handled by Colowyo in the past. After the water begins to accumulate and if any water starts to be discharged from the pit spoils, it will be in contact with spoil that is not geologically or chemically different from the surrounding in situ material. Thus, no significant change to water quality should occur while in this basic environment beyond a moderate potential increase in total dissolved solids. Given the long time frame involved, the small expected contributory volume that could conceivably contribute to springs /seeps /bedrock groundwater resources and dilution of potential moderate increases in total dissolved solids concentrations observed at other locations from water originating from spoil backfill areas, no significant change to local or regional water quality is expected. After the water is discharged (and based on current conditions) any water flow from the pit spoils will either evaporate or recharge the permeable materials in Little Collom Gulch. Little or no surface flow is expected in Little Collom Gulch, since no recorded surface flows have been detected in Little Collom Gulch indicating that any surface water is readily absorbed into the permeable material of Little Cullom Gulch. In addition, ground water levels in Little Collom Gulch are in excess of 10 feet below ground surface based on geotechnical and hydrologic studies in the area. Thus, this discharge water will i°itermix with the in situ ground water, which will further dilute the discharge water. Collom — Rule 2, Page 141 Revision Date: 9/28/11 Revision No.: PR -03