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In general, the Williams Fork Formation, which includes the Twentymile Sandstone and the <br />Middle Coal Group, has yields of up to 100 gpm but the average yield is approximately 10 gpm. <br />The underlying Trout Creek Sandstone has a yield of approximately 5 gpm and occurs under <br />confined conditions with an artesian head of 30 feet above the ground surface. <br />Alluvial aquifers in the permit area include the Sage Creek alluvium, Armand Draw alluvium and <br />Grassy Creek alluvium. The Sage Creek Alluvium has a saturated thickness of between 7.5 and <br />56 feet. Annand Draw alluvium and Grassy Creek alluvium have saturated thicknesses of 12 and <br />11-28 feet, respectively. Groundwater occurs under unconfined conditions in the alluvial <br />aquifers. <br />Movement of groundwater in the alluvial aquifers is controlled by the characteristics of the <br />stream drainages within which they occur, including the stream gradient as well as the width, <br />thickness and hydraulic conductivity of the alluvial deposits. Recharge to alluvial aquifers <br />occurs as infiltration from snowmelt and precipitation and as seepage losses from streams. <br />Baseline groundwater quality studies for the Yoast mine included the alluvial aquifers, the <br />Middle Coal Group, and the Trout Creek Sandstone. The following table summarizes baseline <br />data for pH, 5O4, and total dissolved solids (TDS) for the units mentioned above. <br />A uifer pH S04 (Ma TDS (myJ0 <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. <br />The mean annual temperature is 42° F, with average maximum and minimum temperatures of <br />66° F and 17° F, respectively. The predominant wind direction at the Seneca II-W mine, located <br />west of the Yoast Mine, is from the east-southeast. This direction is in conformance with the <br />topography at that site, and therefore may not be indicative of expected wind directions at the <br />Yoast Mine. The average wind speed at Seneca II-W is 3.5 knots, with an average maximum of <br />15.4 knots, and an average minimum of. 17 knots. <br />Yoast Mine 13 December 15, 2010