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streamflow at Somerset of approximately 313,500 acre-feet per year <br />(1962-1979). Flows in the North Fork usually peak in May or June at <br />around 2,000 to 3,000 cfs, and generally range between 50 and 200 cfs <br />during the rest of the year. The flow is regulated by the Paonia Reservoir <br />on Muddy Creek five miles upstream of the town of Somerset. The <br />reservoir became operational in 1962. Water yields during that period <br />have ranged from a high of 601,800 acre feet per year in water year 1984, <br />to a low of 82,270 acre feet in water year 1977. Water in the North Fork <br />has a neutral to alkaline pH, and is a sodium-bicarbonate type with total <br />dissolved solids generally less than 100 mg/1. <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 will terminate to the <br />south of Raven Creek because of that buffer zone. <br />A major contributor to flow in Raven Gulch is Deep Creek, a perennial <br />stream that drains the southeastern part of the permit area. Flows in Deep <br />Creek historically have been in the 0.1 to 0.5 cfs range during most of the <br />year, as indicated by MCC's monitoring data from 2000 through 2005. <br />Springtime flows exceed 30 cfs. Alluvium in the Deep Creek watershed <br />is too thin to serve as a ground water supply source. <br />Most of the southern part of the permit area is in the Minnesota Creek <br />watershed that was approved for mining in PR-10. This major watershed <br />covers approximately 53.5 square miles. Tributaries to the mainstem of <br />Minnesota Creek include Horse Creek, South Prong, Lick Creek, Dry <br />Fork, and East Fork. The mainstem of Minnesota Creek enters the North <br />Fork of the Gunnison near the town of Paonia. Based on streamflows <br />measured in water year 1978, the water yields from these drainages are <br />nearly an order of magnitude greater than the yield from Sylvester Gulch. <br />The evaluation of flow within the Minnesota Creek drainage is <br />considered only an approximation due to infiltration and seepage losses, <br />seasonal variations in precipitation and potential evaporation and <br />31