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undertaken pursuan[ to HR 13950 which subsequently became the Surface <br />Mining Control and Reclamation Act. Their analysis of the AVF identified <br />by Hardaway at Utah International`s Craig Mine says "...the mine would <br />likely have negligible impact on any alluvial valley floors. The mine <br />is to be located on a steep hillside, a couple of miles (or more) from <br />the river. Further, permit analysis by the U.S.G.S. has indicated no <br />ptoblems with alluvial valley floors. Hence it was considered unlikely <br />that HR 13950's alluvial valley floor provisions would impact this site <br />under reasonable interpretations." <br />In support of the above conclusions, a subsequent study (Settergren, 1979) <br />has defined that the vertical flow within the Upper Williams Fork aquifer <br />and the Yampa alluvium is small, A seepage study (Machin, 1978) of the <br />Yampa River has shown that the river loses more water than it gains in <br />the area of the Big Bottom. <br />A summary of the justifications for these conclusions are as follows: <br />1. The Yampa River gets its surface flow mainly from headwater <br />portions of the drainage. Mean annual flows are 1.9 and 0.42 <br />cfs/mil for Walton Creek near Steamboat Springs and the Yampa <br />River near Maybell. Contribution of surface water from the <br />Trapper Mine area is insignificant and estimated at 0.07 cfs/m i2 <br />2. The ground water contribution to the base flow of the Yampa <br />River from the mine plan area is undetectable. <br />3. Potentiometric studies show that the alluvial aquifer in the <br />Big Bottom area is hydraulically isolated from the bedrock <br />aquifers of the Williams Fork Formation. <br />2-533 <br />