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underlying Trout Creek Sandstone has a yield of approximately 5 gpm and occurs under confined <br /> conditions with an artesian head of 30 feet above the ground surface. <br /> Alluvial aquifers in the proposed permit area include the Sage Creek alluvium, Annand Draw <br /> alluvium and Grassy Creek alluvium. The Sage Creek Alluvium has a saturated thickness of <br /> between 7.5 and 56 feet. Annand Draw alluvium and Grassy Creek alluvium have saturated <br /> thicknesses of 12 and I 1-28 feet, respectively. Groundwater occurs under unconfined conditions in <br /> the alluvial aquifers. <br /> Movement of groundwater in the alluvial aquifers is controlled by the characteristics of the stream <br /> drainages within which they occur, including the stream gradient as well as the width, thickness and <br /> hydraulic conductivity of the alluvial deposits. Recharge to alluvial aquifers occurs as infiltration <br /> from snowmelt and precipitation and as seepage losses from streams. <br /> Baseline groundwater quality studies for the Yoast mine included the alluvial aquifers, the Middle <br /> Coal Group, and the Trout Creek Sandstone. The following table summarizes baseline data for pH, <br /> SO4, and total dissolved solids (TDS) for the units mentioned above. <br /> Aquifer pH SOa m 1 TDS (m2/b <br /> Annand Draw Alluvium 7.5 632 (avg.) 816-1802 <br /> Grassy Creek Alluvium 7.02-7.42 167-2517 546-4030 <br /> Sage Creek Alluvium 6.7-8.3 <539 344-1146 <br /> Lennox Coal 6.7-7 303-480 920-1200 <br /> Lennox Overburden 6.8-6.9 1790-4157 2030-6432 <br /> Wadge Overburden 6.5-8.8 99-1737 549-3052 <br /> Wadge Coal**** >12 <500 234-1232 <br /> Wadge Underburden 6.9-7.0 14-696 996-1550 <br /> Wolf Creek Coal 6.9-8.5 346-416 904-988 <br /> Trout Creek Sandstone 7.2-8.25 —412 —871 <br /> Climate <br /> The average annual precipitation for the town of Hayden, 8.5 miles northwest of the mine site, is <br /> approximately 15.9 inches. Precipitation for Hayden is relatively uniform throughout the year. The <br /> mean annual temperature is 42' F, with average maximum and minimum temperatures of 66' F and <br /> 17' F, respectively. The predominant wind direction at the Seneca 11-W mine, located west of the <br /> Yoast Mine, is from the east-southeast. This direction is in conformance with the topography at that <br /> site, and therefore may not be indicative of expected wind directions at the Yoast Mine. The average <br /> wind speed at Seneca 11-W is 3.5 knots, with an average maximum of 15.4 knots, and an average <br /> minimum of.17 knots. <br /> Yoast Mine 12 October 19, 1999 <br />