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100 mg/l. The total suspended solids increase to Hubberson Gulch that can be <br />attributed to mining is expected to be minimal. Once vegetation is successfully <br />reestablished, the erosion rates are expected to return to the pre-mining level of <br />approximately 140 tons/mi'/yr. <br />Sediment ponds will act to control flood flows from the disturbed area. The ponds <br />will regulate flood discharges, minimizing the impact of the floods. The ponds are <br />not expected to significantly reduce the quantity of runoff water available in Dry <br />Creek. The mine area makes up only a small portion of the Dry Creek watershed <br />(0.9%). <br />The major impact of mining will be the development and subsequent discharge to <br />the surface system of spoils aquifer waters. As each successive pit is reclaimed in <br />the Wadge and Wolf Creek/Sage Creek mining areas, a spoils aquifer will begin <br />to develop. The water necessary to recharge these aquifers will be derived from <br />precipitation, overland flow, and discharge from the Williams Fork formation <br />overburden and the coal seams being mined. <br />The backfilled pits in and of themselves will display unconf"med conditions, <br />however the pits will be surrounded on the sides and be underlain by relatively <br />confming units. The underlying material will be even more confming than the <br />sides. <br />As water enters the reclaimed areas it will tend to migrate through the spoils <br />toward the lowest point in the pit. While some of this water may be lost to the <br />walls, the major portion of it will stay in the pit, as the permeability of this <br />material is greater than that of either the walls or the floor. It is projected that the <br />water quality of spoil aquifers at the Seneca II-W Mine site will approximate that at <br />the nearby Seneca II Mine. The Seneca II Mine spoil aquifers exhibit elevated <br />levels of, total dissolved solids, magnesium, manganese, molybdenum, and sulfate. <br />Complete water quality analyses of two spoils aquifer wells are published in the <br />Seneca II Mine 1984 Annual Hydrology Report, Appendix B. <br />As the aquifer is developing, the water will be of slightly poorer quality than the <br />above assumptions, but as the more easily leached constituents are lost, the quality <br />should approximate that at Seneca II Mine. Analysis of spoils water from the <br />Seneca II Mine indicates that this magnesium-calcium sulfate water has elevated <br />levels of sulfate and magnesium. TDS values vary between 2,200 and 4,000 mg/l. <br />Eventually, water at Seneca II-W Mine will begin to discharge to the surface as the <br />water elevation exceeds the ground level or when sufficient head is developed. <br />Seneca n-W Findings Document 44 November 17, 2004 <br />Permit Revision No. 4 <br />