2011-08-09_REVISION - C1981019 (10)

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• • • Other Potential Impacts Collom — Rule 2, Page 140 RULE 2 PERMITS 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 Collom 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 intermix with the in situ ground water, which will further dilute the discharge water. Flooding and stream flow regime do not appear to have been affected by past mining operations or reclamation, nor are they anticipated to be affected by Collom Lite and Little Collom X mining. Groundwater availability in the area may potentially be enhanced with the storage of water in the reclaimed pits. , Colowyo owns significant water rights within the affected drainages. Any potential diminishment of flow will be compensated for by reduced use by Colowyo. There is sufficient capacity for Colowyo to reduce their use of adjudicated water to compensate for potential diminishment of flow, allowing downstream users full access to their water rights. With respect to alluvial valley floors (AVFs), lower portions of Collom Gulch have been studied before and since the release of the 1985 OSM Alluvial Valley Floor (AVF) Reconnaissance map. The reconnaissance by OSM was compiled on 1:100,000 -scale maps and was meant to represent a reconnaissance level effort to identify areas which are likely to meet the AVF definition (from Introduction to OSM report accompanying this study). Thus, any area identified on the OSM maps are potential AVFs. It was recognized in this study that future studies may more conclusively prove or disprove the AVF findings in the report. Colowyo and other companies in this area performed AVF studies to more conclusively prove or disprove the existence of AVFs in this potential coal mining area of the Danforth Hills. For the Collom area, there has been significant studies to date examining the Collom Gulch and the potential for an AVF in the area possibly affected by mining activities in the Collom light area. Revision Date: 8/5/11 Revision No.: PR -03