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floor (AVF) if the valleys had water availability sufficient for flood -irrigated agricultural <br />activities [Section 1.04(10)], or availability of water sufficient for sub -irrigated <br />agricultural activities [Section 1.04(10)]. Flood irrigation is practiced on the valley floors of the <br />Yampa River in the Big Bottom area and the Williams Fork River near its confluence with the <br />Yampa. Based on the presence of unconsolidated stream -laid holding streams with water <br />availability sufficient for flood -irrigated agricultural activities, the following two alluvial valleys <br />have been determined to be alluvial valley floors: <br />1. the Yampa River in the Big Bottom area <br />2. the Williams Fork River near its confluence with the Yampa River. <br />Map 35 A and Map 52 indicate the location of AVF well sites. The Coy well drilled into the <br />alluvium of Flume drainage functions as a point of compliance well. Four wells are drilled into <br />the Pyeatt alluvium, well J1 is located in the Johnson drainage alluvium and one of the three <br />GLEV wells in the Deacon drainage reached the alluvium at the very north east corner of the <br />permit. This GLEV well is located downgradient of any mining to the east that may occur in the <br />future. These wells constitute an environmental monitoring system during surface coal mining <br />and reclamation operations continuing until release of all bonds in accordance with Rule 3 (4. <br />24.4). <br />Four gulches (No Name, Johnson, Pyeatt, and Flume) are determined not to be alluvial valley <br />floors based on their absence of water availability sufficient for flood -irrigation or sub -irrigation <br />agricultural activities. <br />Potential impacts to the Yampa River AVF resulting from the proposed mining operation are <br />negligible. Generally, the Yampa River AVF receives very little of its water supply (surface and <br />ground water) from the proposed mine area. The majority of the flow in the river and subsequent <br />recharge to the alluvial aquifer derive from the headwaters portions of the drainage, far upstream <br />from Trapper. The applicant states that the contribution of surface water from the Trapper mine is <br />insignificant as per page 2-533 of the permit application. <br />This is substantiated by seepage, runoff, and potentiometric studies in Appendix H of the permit <br />application. Based on the information presented by the applicant, the Division finds that <br />proposed surface coal mining operations will not interrupt, discontinue, or preclude farming on <br />the Yampa River AVF, nor materially damage surface or ground water quantity or quality in <br />systems supplying the Yampa River AVF (4.24.3(l)),(4.24.3(3), and 2.06.8(5)(a)(ii)). <br />The potential for impacts from mining to the Williams Fork AVF is also negligible. The <br />Williams Fork River is located south of the proposed mining area. Almost exclusively, spring <br />snowmelt comprises the only surface discharge from sediment ponds in the drainages flowing <br />towards the Williams Fork River. It is likely that much of the discharge from these ponds <br />infiltrate into the permeable Twentymile Sandstone outcrop prior to reaching the Williams Fork <br />River. Therefore, the Division finds that the proposed surface coal mining operations will not <br />Page 22 <br />Trapper RN7 Prepared by: R. Reilley <br />Nov 2017 <br />