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1) the drawdown of ground water, due to pit dewatering, for a few hundred to <br />perhaps 1,000 feet from the pit; <br />2) possibly diminished quantity and quality of water in the Temple Well no. 1; and <br />3) the probable dewatering and degradation of quality in three to five springs in <br />the permit area, two of which are used for stock watering purposes; <br />4) the possible increase in water quantity and decrease in quality of alluvial water <br />in Hubberson Gulch and its unnamed tributary along the access road, due to <br />infiltration of spoils discharge; <br />5) the establishment of a relatively unconfined aquifer of poor quality in the <br />backfilled pits. A discussion of the potential impacts follows. <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. Coal removal is by an updip strip method. As <br />a general rule, more water will be encountered at the first cut than when the <br />operation proceeds updip. Inflows from units underlying the Wadge are not <br />expected, as mining methods should not cause fracturing of the relatively <br />impermeable underlying materials. Regional aquifers located in or near the permit <br />area include the Tow Creek Sandstone, Trout Creek Sandstone and Twenty Mile <br />Sandstone. <br />The Twenty Mile Sandstone lies stratigraphically above the Wadge coal (the seam <br />being mined) by about 525 feet. The Twenty Mile Sandstone which has been eroded <br />over much of the Seneca II-W Mine area. will not be disturbed by mining <br />operations, so its water quality and quantity will not be affected. <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 likely <br />that hydraulic pressures capable of affecting this aquifer will develop. Therefore, <br />mining activities are not expected to disturb this regional aquifer. <br />About 200 feet below the Wadge coal lies the Trout Creek Sandstone. The <br />Trout Creek is thought to be an aquifer of regional significance, but is not monitored <br />at this site. The applicant completed a water supply well in the Trout Creek from <br />which they sustain an average pumping rate of 35 gallons per minute. The relatively <br />impermeable interburden between the Wadge coal and the Trout Creek Sandstone <br />(which includes the Wolf Creek coal) and the stratigraphic distance between them <br />will preclude impacts to the Trout Creek sandstone from mining. <br />Seneca 11-W Findings Document 27 June I5, 2001 <br />Permit Renewal No. 3 <br />