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-2- <br />The permeabilities obtained from this testing ranged from 11 to 15 gpd/ft2 <br />• and averaged 13 gpd/ft2. The calculated transmissivities ranged from 64 to <br />80 gpd/ft and averaged 74 gpd/ft. These results are similar to those <br />obtained from the limited test pumping performed in 1979 (blatec, Inc., 1980). <br />In that testing a transmissivity of 139 gpd/ft and a permeability of <br />approximately 20 gpd/ft2 were obtained. These permeabilities seem reasonable <br />fora heterogenous, poorly sorted material like the Williams Fork Alluvium. <br />Summary <br />The Williams Fork Alluvium in the vicinity of the Empire Energy Company <br />Eagle Mine No. 5 is 10 to 15 feet thick consisting of poorly sorted clay to <br />cobble sized materials. The saturated thickness was approximately 5 to 6 <br />feet in March 1982. The permeability and transmissivity calculated from <br />slug test data averaged 13 gpd/ft2 and 74 gpd/ft respectively. The <br />permeability and transmissivity was previously estimated from a short pumping <br />test to be approximately 20 gpd/f t2 and l40 gpd/ft respectively. <br />HYDROLOGIC ANALYSIS <br />Yampa River Alluvium, Big Bottom Area <br />Local Geology <br />• Empire Energy plans to extend their Eagle Mine No. 9 under the valley floor <br />of the Yampa River in the Big Bottom Area. In the Big Bottom area, the <br />i valley floor is up to 9000 feet wide and averages approximately 5000 feet <br />' wide. The valley floor is underlain by approximately 10 to 18 feet of <br />alluvium. The alluvium consists of sandy silts overlying poorly sorted <br />silty sand to cobble size material with occasional thin layers of clean <br />sands and gravels. The material generally becomes coarser with depth and <br />is sometimes mantled with 2 to 4 feet of fine sandy .to loamy soil. Bedrock <br />is sandstones, siltsones and shales of the Williams Fork Formation and <br />Lewis Shale. <br />Well Construction <br />On 13 through 19 March 1982, 7 wells were completed in the Yampa River <br />alluvium. Four of the wells were completed in a pumping test array in the <br />central portion of the Big Bottom area (YAW-4, YAW-5, YAW-6 and YAW-7). <br />Two wells were completed upriver of the pumping test array (YAW-1 and <br />YAW-2). An additional well was completed at the edge of the valley floor <br />opposite the pumping test array. The well locations are shown on Map <br />III-11, summary loads are presented on Figure 3 and a cross-section is <br />presented on Figure 5. Typical well construction is presented on Figure 4. <br />Well YAW-1 was drilled with air rotary drilling methods. The rest of the <br />wells were drilled with mud rotary drilling methods with UOP Johnson Revert <br />used as the drilling fluid. Following completion of each hole, the drilling <br />fluid was treated with chlorine to break down the Revert. Well YAW-5 was <br />drilled with an 11-3/4 inch bit and completed with 6-5/8 inch O.D. PVC <br />casing and continuous slat screen (.030 inch slot size). The remaining <br />