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<br />Daub & Associates, Inc. Page 3-11 2015 NS Mine Plan Modification <br />1/5/2016 Section 3 General Site Conditions <br />facing slopes may be totally snow free while their north facing counterparts maintain <br />significant snowpack. <br />Differential heating effects can have a dominant influence on the micro-scale wind <br />fields in the complex terrain of the Basin. In the steep-walled valleys of the region, <br />an intricate system of upslope and drainage flow is established, controlled almost <br />entirely by the changes in surface heating. The result is that each location within the <br />region has its own unique surface wind pattern. <br />The net effect of the mixture of these two climate types is that temperatures across <br />the Basin vary most readily with elevation. Average summer temperatures range <br />from a low of 45°F to 85°F, with maximums reaching 100°F. Contrastingly, average <br />winter temperatures range between 5°F to 35°F with extremes of -40°F being <br />recorded on occasion. Depending on local terrain and wind patterns, frost-free <br />periods range between 60 and 150 days. Likewise, the growing season is highly <br />variable. Data for the vicinity of Grand Junction show that the growing season runs <br />about 190 days plus or minus 2 to 3 weeks depending on location. Precipitation is <br />relatively uniform throughout the year with slightly more than half occurring during <br />late spring through early fall. Total annual precipitation is highly variable and ranges <br />between 8 and 24 inches. Winter snowpack ranges from 25 to 150 inches. Little <br />data are available on regional evaporation rates; however, data collected in 1976 for <br />the six month period running from May through October revealed total evaporation of <br />59.01 and 34.49 inches for Grand Junction and the nearby Federal Lease Tract C-a, <br />respectively. <br />The wind fields of the Basin can be divided into two groups; upper level synoptic flow <br />and low-level micro-scale. The synoptic flow, which is predominant throughout the <br />year, is southwesterly, with an average annual speed of 13.18 mph, measured from <br />8,000 to 13,000 ft. Seasonally, speeds vary from a low of 4.59 mph during the <br />summer to a high of 25.15 mph in winter near Tract C-a located southwest of the NS <br />Plant. Micro-scale patterns are more irregular and controlled by local terrain. These <br />micro-scale winds have been shown to have a classic diurnal pattern. This pattern