2010-09-29_REVISION - M1981185 (11)

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0 R21NCORPORATED ENVIRONMENTAL AND ENGINEERING SERVICES STRATEGICALLY POSITIONED-TECHNICALLY PREPARED GEORGE M.L. ROBINSON,P.G. j. ER CH RAUBERY.E. ANDREW HARLEY,PH.D GINNY KING MAY DAY IDAHO MINE COMPLEX WILDCAT MINING CORPORATION ORIGINAL 112(d) PERMIT EXHIBIT K Climate Rule 6.4.11 • • The May Day Idaho Mine Complex is located in the Little Deadwood Gulch drainage of San Juan National Forest (subbasin 14680105). The climate in this portion of the central Rocky Mountains in southwestern Colorado can be variable with notable differences in microclimate due to slope, aspect, and elevation. Elevations on the site range from 8,600' (AMSL) along the La Plata River floodplain to approximately 9,600' at the Lamb Portal (May Day No. 3). Typical mid-summer afternoon temperatures are in the upper 70 degrees Fahrenheit, with night- time around 40°F1. Conversely, the wintertime high temperatures are around 40T, with night- time in the low 10T (Figure K-1). In general, since temperatures decrease with elevation with mountainous terrain, the lower portion of the site may be cooler than the higher locations. Sum- mer afternoon temperatures can decrease about 4 to 5°F per thousand feet. The average annual precipitation for this area is 18.0". This tends to be received throughout the year with most months receiving at or greater than 1" of rain or water equivalent as snow (Figure K-2). Late summer through early fall receives the most moisture with July and August typically getting over 2". On average, rainfall is lightest in midsummer, with June being the driest month. Deviations from these averages are high both within months and between years. In summer, Baldy Peak and the surrounding ranges are effective thunderstorm generators when- ever the regional air masses are sufficiently moist. The last half of July and much of August are particularly prone to mountain thunderstorms. Snow and soft hail are possible from mountain storms even in July and August. Winter precipitation generally falls as snow from October through April. The mean annual snowfall for this area over the last 50 years has been 80" with over 15" per month falling be- tween December and February' (Figure K-3). A portion of this snow melts during the warmer days; however, some snow accumulates without melting during midwinter, particularly in north- facing, shaded and level areas. This accumulation and melt results in an average on ground snow t All climate data is from the Fort Lewis weather station as reported by the High Plains Regional Climate Center: http://www.hprcc.unl.edu/cgi-bin/cli per] lib/cliMAIN.pl?co3016 available July 16, 2010. May Day Idaho Mine Complex 112(d) Permit Application September 21, 2010 "Strategically Positioned - Technically Prepared" 5555 DTC Parkway Suite A-4000, Greenwood Village, Colorado 80111 Phone: (303)832-7664, Fax: (303)832-7469