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<br />The Sage Creek anticline is a local structure within the regional Sand Wash <br />Basin. The Sand Wash is a large ground water basin located in northwestern <br />Colorado and southern Wyoming. <br />Coal removal will be by an up-dip strip method. As a general rule, more water <br />will be encountered at the first cut than when the operation proceeds up-dip. <br />During mining, inflows may be expected to develop from perched aquifers within <br />the Williams Fork overburden, from a limited Williams Fork overburden aquifer, <br />and from the Wadge coal aquifer. Inflows from units underlying the Wadge are <br />not expected, as mining methods should not cause fracturing of the relatively <br />impermeable underlying materials. <br />Regional aquifers located in or near the permit area include the Tow Creek <br />Sandstone, Trout Creek Sandstone and Twenty Mile Sandstone. <br />The Twenty Mile Sandstone lies stratigraphically above the Wadge coal (the <br />principle seam to be mined) by about 525 feet. The Twenty Mile Sandstone <br />which has been eroded over much of the Seneca II-W area, will not be disturbed <br />by mining operations, so it's water quality and quantity will not be effected. <br />The Tow Creek Sandstone lies more than 1300 feet below the Wadge coal. Due to <br />the thickness of the interburden between the Tow Creek and Wadge, it is not <br />likely that hydraulic pressures capable of effecting this aquifer will <br />develop. Therefore, mining activities will not disturb this regional aquifer. <br />About 200 feet below the Wadge coal lies the Trout Creek Sandstone. The Trout <br />Creek is thought to be an aquifer of regional significance, but is not <br />monitored at this site. The applicant is planning on completing a water <br />supply well in the Trout Creek from which they hope to sustain an average <br />pooping rate of 35 gallons per minute. <br />The relatively impermeable interburden between the Wadge coal and the Trout <br />Creek Sandstone (which includes the Wolf Creek coal) and the stratigraphic <br />distance between them will preclude impacts to the Trout Creek sandstone from <br />mining. <br />The Wolf Creek coal seam, which lies 150 to 170 feet below the Wadge coal <br />seam, is the first significant aquifer below the mined seam. This seam, which <br />is up to 12 feet thick, appears to be saturated in this area. Due to the dip <br />of the unit and the confining nature of the over and underburden, the Wolf <br />Creek has as much as 770 feet of artesian head in a well. It should be noted <br />that the amount of head is aerially variable as the aquifers conditions change <br />from water table (unconfined) near outcrops to confined conditions at depth. <br />Due to mining methods and the thickness and type of interburden between the <br />Wolf Creek and Wadge, pit inflows from upward movement of the Wolf Creek are <br />not expected. If fracturing of the interburden and/or the Wolf Creek coal, <br />due to blasting or unloading of materials (overburden and Wadge coal seam), <br />were to occur, it is estimated that 80% of the Wolf Creek head would be lost <br />to friction, leaving a maximum total head of about 155 feet, which could <br />potentially result in minor inflow. <br />-34- <br />