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Inflows into underground mine workings from faults and fractures <br /> located outside stream valleys generally dry up with time or flow <br /> intermittently at discrete points along the fault or fracture. Those which <br /> continue to flow have flow rates which diminish to a trickle. Such mine <br /> inflows from faults and fractures may represent the dewatering of <br /> lenticular sandstone units with limited recharge areas, or may represent <br /> flows through fracture zones extending to the surface which have narrow <br /> recharge zones on steep slopes. The large initial flow rates are much <br /> larger than what would be expected from intergranular porosity in low- <br /> permeability sandstone (Darcy-type flow), indicating flow probably is <br /> from fractures or faults. <br /> Discharge of groundwater occurs through numerous seeps and springs <br /> identified in the life-of-mine area. The locations of these springs are <br /> shown on Map 37 and 37A, Springs and Stock Ponds. <br /> C. Surface Water <br /> The North Fork of the Gunnison River is the principal drainage in the <br /> mine area. Smaller streams in or adjacent to the life-of-mine areas are <br /> tributary to the North Fork. The North Fork has an average annual <br /> streamflow at Somerset of approximately 487.8 cfs per year (1980-2017). <br /> Flows in the North Fork usually peak in May or June at around 2,000 to <br /> 3,000 cfs, and generally range between 50 and 200 cfs during the rest of <br /> the year. The flow is regulated by the Paonia Reservoir on Muddy Creek <br /> five miles upstream of the town of Somerset. The reservoir became <br /> operational in 1962. Water yields during that period have ranged from a <br /> high of 601,800 acre feet per year in water year 1984, to a low of 82,270 <br /> acre feet in water year 1977. Water in the North Fork has a neutral to <br /> alkaline pH, and is a sodium-bicarbonate type with total dissolved solids <br /> generally less than 100 mg/l. <br /> Streams in the northern part of the West Elk Mine permit area are <br /> Sylvester Gulch, Lone Pine Gulch, and Gribble Gulch. These three <br /> streams flow directly to the North Fork. Lone Pine and Gribble Gulches <br /> have ephemeral flows. No flow has been observed in Lone Pine Gulch <br /> for several years. Sylvester Gulch is ephemeral in its upper section, but <br /> has perennial flow in its lower section due to a spring. Sylvester Gulch <br /> has a drainage area of 4.25 square miles. The hydrologic yield of <br /> Sylvester Gulch is small for its size compared to other area watersheds <br /> due to its lower elevation and gentler slopes. <br /> Raven Creek crosses the northeastern corner of the permit area over a <br /> distance of approximately 2,000 feet. This perennial stream and its <br /> riparian zone are protected from undermining and subsidence by a buffer <br /> zone of 660 feet (1/8 mile) on either side of the stream, as stipulated in <br /> Lease COC-67011. Mining approved by PR-11 terminated to the south <br /> 40 <br />