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' 2.04.7(2) <br />' The Bear DIine is adjacent to the North Fork of the Gunnison <br />River. A discussion of possible flooding at the mine site was <br />' obtained with information provided from a study entitled Flood <br />Hazard Information, North Fork Gunnison River, Hotchkiss to <br />' Somerset, Colorado, published by the Department of the Army, <br />Corps of Engineers in February, 1980. Additional cross-sections <br />' were obtained from the AP,CO Permit Application. <br />The North Fork Gunnison River is formed by the confluence of the <br />N,uddy and Anthracite Creeks near Paonia Dam. From its source <br />to its mouth near Lazear, the stream flows about 30 miles on a <br />' southwesterly course. Its tributary drainage area (a part of: the <br />Colorado River basin) is situated in west-central Colorado on the <br />' western slope of the Rocky Mountains. At Hotchkiss and Somerset, <br />the stream drains 940 and 530 square miles respectively. Elevation <br />' ranges from 5400 feet at Hotchkiss to around 13,000 feet in t:he <br />highest headwater regions, and stream gradients vary from about <br />30 feet per mile at Hotchkiss to 60 feet per mile at Somerset:. <br />Terrain of the basin is mostly mountainous with some mesa an~i <br />' tableland in the lower portion. <br />Predominant vegetation consists of pine, fir, and spruce in the <br />high portions of the drainage area, while sagebrush and other- <br />' low-growing shrubs are characteristic in the lower portions. <br />Thick stands of cottonwood occur alont the river. Drawing <br />' 2.04.7(2)(b)(i)-1 illustrates the North Fork Gunnison River <br />Drainage Basin and its tributaries within the study limits. <br />' General frontal-type rainstorms approaching from the southwe:>t <br />' can occur over the North Fork Gunnison River basin from mid-~1une <br />through December, but records show that they occur most often <br />during September and October. Convective-type cloudburst storms <br />' occur frequently during the summer in west-central Colorado. <br />Most of the annual precipitation in this region, however, occurs <br />as snow and a deep snowpack usually accumulates in the high areas. <br />Studies show that rapidly melting snow in the spring and ear:Ly <br />summer constitutes the principal source of flooding along th~a <br />REVISED 19ay 15, 1981 47-2a <br />