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<br />IIA. DESCRIPTION OF THE EXISTING ENVIRONMENT <br />Jackson County occupies a topographic depression defined on <br />the east , south, and west by the Medicine Bow Range , the Rabbi t <br />Ears Range, and the Park Range, respectively. Elevations vary <br />from fewer than 8,000 feet in North Park to over 12,000 feet in <br />the surrounding peaks. Regional and local topographic features <br />yreatly affect climatic conditions, creating highly variable pre- <br />cipitation and temperature values thou9hout the county and a gen- <br />erally semi-arid climate in the vicinity of the permit area. <br />The monthly average temperatures observed at Walden varied <br />from 15.6°F in January to 58.7°F in July. Monthly mean maximum <br />and mean minimum temperatures should vary from 27.9°F in January <br />and 77.9°F in July (mean maximums) to 3.3°F and 39.5°F in January <br />and July, respectively (mean minimums). <br />Average annual precipitation measured at Walden over a 34- <br />month period is 9.6 inches. Most precipitation occurs in the <br />interior of Jackson County during the spring and summer months, <br />although this is highly variable; precipitation measured during <br />June may vary from 0.03 inches to 3.04 inches. Precipitation at <br />the mine site, which is at a higher elevation than Walden, is <br />estimated to be 11 or 12 inches. (Information supplied to <br />Wyoming Fuel Company by Assistant State Climatologist, Colorado <br />State University). <br />Average annual snowfall at Walden is 51 inches, however, <br />other parts of Jackson County receive over 100 inches of snowfall <br />per year. The average annual frost-free period is 40 days. <br />Prevailing winds are of moderate velocity and from the <br />west. Inversions are not uncommon in North Park, and may be <br />expected to occur eighty percent of the time. (BLM Environmental <br />Analysis No. CO-010-0-183, Appendix D, Volume II of the permit <br />application). <br />_19_ <br />