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Underground workings extend from the portal areas, which are in <br /> Coal Basin, beneath Huntsman Ridge, and underlie the west and south <br /> slopes beyond Huntsman Ridge. Huntsman Ridge is the dividing line <br /> between Pitkin and Gunnison Counties, and the White River and <br /> Gunnison National Forests. <br /> Geology <br /> The structure of the Coal Basin is thought to have been formed <br /> by the doming of sedimentary strata over an igneous intrusion. <br /> Faulting is common, and is a significant determinant of the <br /> drainage pattern in Coal Basin, having directly or indirectly <br /> controlled Bear Creek, all forks of Dutch Creek, both forks of <br /> Oilwell Creek, Porcupine Creek and Coal Creek. <br /> Topography <br /> Coal Basin is characterized by steep, erratic, deeply eroded <br /> terrain. Elevations range from 7,180' at the confluence of <br /> Coal Creek with the Crystal River, to 8,000 at the central <br /> complex yard area, to 11,8501 along Huntsman Ridge. Areas of <br /> moderate terrain are rare. <br /> The erosion cycle of Coal Basin is estimated at 36,000,000 <br /> years, to the Eocene era. The outcropping strata in Coal <br /> Basin are, for the most part, highly erosive, particularly the <br /> Mancos Shale, which floors most of the basin and is the most <br /> common unit. As a result, Coal Basin is characterized by a <br /> highly eroded topography. <br /> Drainage <br /> The primary stream in Coal Basin is Coal Creek, a perennial <br /> stream, tributary to the Crystal River. This stream drains an <br /> area of 26 square miles. Streams and stream segments <br /> tributary to Coal Creek include Bear Creek, the South Fork of <br /> Dutch Creek, the North Fork of Dutch Creek, Oilwell Creek, <br /> Porcupine Creek, Spring Creek and Braderich Creek. Mine <br /> facilities are situated in the drainages of Coal Creek, North <br /> and South Dutch Creek. <br /> climatic Conditions <br /> Precipitation averages approximately 29 inches per year, of <br /> which 70% falls in the form of snow. Snowfall begins in <br /> October, and snowpack continues through May. <br /> Surface Use In Addition to Mining <br /> Livestock have grazed Coal Basin since 1946, under permit from <br /> the U.S. Forest Service, and the use continues during the <br /> summer months. <br /> VI. MINING OPERATIONS AT THE SITE <br /> A. Historic Use <br /> Crystal Springs Coal, Inc. 9 Coal Basin Mine <br />