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Alluvial Valley Floors (AVF) • The AVF's identified in the vicinity of the Trapper Mines are the Yampa River, the Williams Fork River, and Fiume Gulch. The potential. for each of these to be impacted by the proposed mining operations is discuse:ed below. The potential for the Yampa River AVF to be impacted by the proposed mining operations is probably negligible. Generally, the Yampa River Ai'F receives very little of its water supply (both ground water and surface water) from the proposed mine area. The majority of the flow in [he river and the alluvial aquifer comes from the headwater portions of the drainage. The applicant states [ha[ the contributions of surface water from the T. rapper Ptine is insignificant and is estimated a[ 0.07 cfs/miz. Further, the ground water contribution to the base flow of the Yampa River is undetectable. This is substantiated by seepage, run, and potentiometric studies which basically show the following: 1) the Yampa River loses surface water flow to the alluvial aquifer as it flows past the mine area, and 2) the Yampa alluvial aquifer is hydraulically isolated from the bedrock aquifer of [he Williams Fork Formation. In addition, all disturbance related to the proposed mine is located at least one mile from the southern boundary of :he Yampa River AVF. Therefore, it is very unlikely that the Yampa River AVF will be Impacted by the proposed mining operations. The potential for the Williams Fork River AVF to be impacted by the proposed mining operation is also negligible. The Williams Fork diver is located on the opposite side of a major drainage divide from the Trsipper Mine. All drainage, both surface water and ground water, flows away from the Yilliams Fork and towards the Yampa P.iver. Furthermore, the stra[:a to be affected by the proposed mining operations outcrop on the Yampa River side of the drainage • divide. In addition, no mining-related disturbance is proposed in the Williams Fork River drainage area. Therefore, the Williams Fork River AVF should not be impacted by the proposed mining operations. The other AVF within the mine plan boundary is about 50 acres along Flume Gulch. This is the upstream end of the drainage and is only used for grazing. No mining disturbance covered under the proposed 5-year permit term is located within the Flume Gulch drainage area. Mining activities will not disturb any portion of the drainage area until the next 5-year permit term. In addition, because of the dip of the strata, all ground water flow from the mine area is directed deep beneath all the small drainages in the vicinity of the mine. Therefore, the proposed mining operations in this 5-year permit term should not impact the Flume Gulch AVF. However, because of the potential for impacts due to mining exists for Flume Gulch during the life of the mine, the applicant has committed to hydrologic monitoring of Flume Gulch. The monitoring plan contained in section 4.8.5.1 of the MF.P wall be adequate in detecting any mining-related impacts upon Flume Gulch. The MRP does not include any information as to the nature of disturbance in this area during the next 5-year permit term. -14- •