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3.4.2 Description of Regional Surface Water <br />3.4.2.1 Mine <br />The mine lies within the North Thompson Creek drainage basin which is <br />a tributary to the Crystal River 5 miles east of the mine. The <br />Crystal River joins the Roaring Fork River 2 miles below Carbondale. <br />The Roaring fork is a tributary to the Colorado River at Glenwood <br />Springs which is about 15 miles north of the mine, <br />Elevations within the drainage basin, which is located within the <br />White River National Forest, range from approximately 11,000 feet down <br />to 7,600 feet at the mine, Vegetation within the watershed is mainly <br />ponderosa pine with some stands of aspen scattered throughout the <br />area. Annual precipitation at the mine is approximately 22 inches <br />with higher portions of the watershed receiving up to 35 inches. <br />Approximately 65 percent of the annual precipitation in the higher <br />• elevation is snowfall. <br />Most of the runoff from North Thompson Creek is derived from snowmelt. <br />This is typical of Crystal River drainages. The peak runoff occurs in <br />May and June with low flows occurring in the fall and winter, <br />Annual peak flows normally result from snowmelt. However, moist Gulf <br />of Mexico summer air masses coupled with the orographic effects of the <br />mountainous terrain give rise to periodic thunderstorms during the <br />summer, The narrow stream valleys and steep slopes cause rapid runoff <br />from thunderstorms on small drainages. Evidence of thunderstorm <br />flooding is found in the Coal Creek drainage basin 10 miles south of <br />the mine which flooded in July, 1977 from an intense thunderstorm. <br />L <br />3-14 <br />