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Ground Water <br />Aquifers of particular interest in the proposed permit area include the coals and interbedded units of <br />the Williams Fork Formation Middle Coal Group as well as the overlying Twentymile Sandstone and <br />the underlying Trout Creek Sandstone. Rechazge to the bedrock aquifers occurs as infiltration at the <br />outcrops, which are parallel to the axis of the Fish Creek Anticline. Discharge is through bedrock <br />springs, which aze tributary to Sage Creek and one in the upper reach of Armand Draw. Bedrock <br />groundwater is confined except in outcrop areas. <br />Baseline studies showed that the Lennox Overburden and Coal units are artesian flowing aquifers. <br />The Wadge Overburden occurs under confined and unconfined conditions. The unconfined <br />conditions aze encountered near the outcrops. The saturated aquifer thickness of these units ranges <br />between four and 200 feet. <br />The Wadge Coal aquifers appeaz to be largely confined, whereas the Wadge Underburden aquifer <br />occurs under both confined and unconfined conditions. The Wolf Creek Coal occurs under confined <br />conditions, however the Wolf Creek Underburden is both unsaturated and unconfined. <br />Movement of groundwater in bedrock aquifers is controlled by structural folding and faulting and <br />stratigraphy. Confined conditions occur at synclinal axes, and unconfined conditions occur near the <br />outcrops. No significant faulting is known to occur within the proposed permit area. <br />Two recharge boundaries aze known to exist in the permit area. An erosional face along the <br />northerly-plunging axis of the Fish Creek anticline provides a localized recharge boundary for the <br />Wadge Coal and Wadge Overburden. Additionally, the Wolf Creek Coal outcrop, parallel to the axis <br />of the Fish Creek Anticline, is a recharge boundary for the Wolf Creek Coal. <br />In general, the Williams Fork Formation, which includes the Twentymile Sandstone and the Middle <br />Coal Group, has yields of up to 100 gpm but the average yield is approximately 10 gpm. The <br />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, Armand Draw <br />alluvium and Grassy Creek alluvium. The Sage Creek Alluvium has a saturated thickness of <br />between 7.5 and 56 feet. Armand Draw alluvium and Grassy Creek alluvium have saturated <br />thicknesses of 12 and 11-28 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 />Yoast Mine 13 February 28, 2006 <br />