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West Elk Mine <br /> <br /> <br />2.04-115 Rev. 08/94- TR71, 06/95- PR06, 03/06- PR10;05/22- MR462 <br />2.04.8 Climatological Information <br /> The West Elk Mine site lies within the North Fork Valley near Somerset, Colorado. At the mine <br />site, the valley is quite narrow and steep-sided and follows a general east-west orientation. A map <br />of west central Colorado showing the mine site and the general vicinity is shown on Figure 1 in <br />Section 2.01. Considerable topographic variation across the mine site, and west central Colorado in <br />general, results in marked fluctuation in seasonal and average precipitation and temperature values <br />for the entire area. <br /> <br />The mountains of the Continental Divide provide an effective barrier to the movement of moisture- <br />laden air that reaches the Eastern Slope of the Rocky Mountains from the Gulf of Mexico. Thus, <br />under this influence, two basic types of climate, semi-arid and undifferentiated highlands are <br />characteristic of the general area where the mine is situated. Temperatures can range below freezing <br />in the winter and yet in the summer, with the exception of higher elevations, can be extremely <br />warm. The precipitation that does fall originates from the Pacific Ocean weather systems and most <br />frequently occurs in the winter. <br /> <br />An on-site weather station was established at the West Elk Mine site in 1997. MCC contracted <br />with IML Air Science of Pace Analytical (Pace) to conduct continuous recording of temperature, <br />wind speed, wind gusts, wind direction, relative humidity, precipitation, barometric pressure and <br />solar radiation. Pace provides annual reports of recorded data to MCC. <br /> Regional <br /> <br />The West Elk Mine baseline climate study area was found to be subject to a synoptic pattern from a <br />westerly direction. This is greatly modified by daily up-canyon (diurnal) and evening down-canyon <br />(nocturnal) wind flows typical of mountainous terrain. Stable air conditions are known to occur in <br />the North Fork, primarily during the winter. From fall to spring, considerable snowfall occasionally <br />accompanies the low-pressure storms. Occurrences of severe weather are infrequent. <br /> <br />Figure 12 shows the West Elk Mine site and the stations that were used for the original permit <br />temperature data collection (Paonia and Paonia 3 SE climatic stations) and precipitation data <br />collection (Paonia, Paonia 3 SE and Wilcox Ranch climatic stations). <br /> Temperature <br /> <br />The closest station to Somerset where temperature data were gathered was Paonia. The monthly <br />temperature summary was recorded for highest maximum temperature observed, lowest maximum <br />temperature observed, and mean monthly temperature. The Paonia 3 SE climatic station was also a <br />source of temperature information. Graphs of the highest and lowest maximum temperatures <br />observed and mean monthly temperatures for each station's period of record are included in Exhibit <br />22. <br /> According to the data from 1957 and before, the temperature at Paonia 3 SE station has ranged <br />from -28 oF in January 1913 to 100oF in June, 1927, July and August, 1934. Typically, January has <br />the lowest minimum temperature. July is consistently the hottest month (Colorado Climatologist,