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Environmental Scientists and Engineers, LLC <br />Table 2 Temperature Monthly Normals (1941 -1970) <br />Monthly Mean Temperature (' F)`. <br />Jan Feb Mar Apr May . Jun Jul Aug Sep Oct Nov Dec <br />Location <br />64.7 <br />56.1 <br />45.4 <br />31.8 <br />21.7 <br />Yearly <br />Normals <br />42.4 <br />Craig' 17.3 22.4 29.7 42.1 51.5 59.0 66.6 44.2 <br />Meeker' 8 21 6 26 2 32 43.3 52.3 60.0 66.9 64.8 56.7 46.8 34.1 25.0 <br />Data from Climatography of the United States No. 81 (Colorado): Monthly Normals of Temperature, Precipitation, and Heating and <br />Cooling Degree Days 1941 -70, U.S. Department of Commerce National Oceanic and Atmospheric Administration <br />. T Craig, Colorado weather station, Lat. N4031, Long. W10733, Elev. 6,285 ft. <br />' Meeker, Colorado weather station, Lat. N4002, Long. W10754, Elev. 6,242 ft. <br />Wind <br />The synoptic flow in the area is characterized by prevailing westerly winds, which <br />influence regional air quality. The direction and speed of the winds are greatly affected <br />by local topography. The general area contains two large drainage basins: the Yampa <br />River Basin and the Williams Fork River Basin. The Yampa Valley forms a broad <br />canyon, which channels the airflow into an east -west orientation reflecting upslope and <br />downslope motion. A similar upslope - downslope wind flow exists in the Williams Fork <br />Valley. The flow draining this Valley is dire northwardly along the high ground west <br />of Craig prior to joining the main stream flowing up and down the Yampa Valley at the <br />east end of Danforth Hills. <br />The high frequency of near -calm conditions exists because of the protection afforded by <br />the local terrain in most of the valleys. These conditions generally occur at night and in <br />the early morning. The strongest winds in the area can be expected during the winter and <br />early spring, especially in March, and briefly during summer thunderstorms. <br />The prevailing winds over most of the permit area will be from the southwest at an <br />average speed of approximately 8 to 9 miles per hour; some 10 to 15 percent of the time <br />the wind will blow out of the northeast. Strong winds will occur due to cold fronts and <br />thunderstorms moving through the area, but fair weather winds will rarely exceed 20 to <br />25 miles per hour. <br />3.2.2 Air Quality <br />The EPA has six criteria pollutants for assessing air quality. These are: 1) sulfur dioxide, <br />2) nitrogen dioxide, 3) ozone, 4) particulates of 10 microns or less, 5) lead, and 6) carbon <br />monoxide. In order to assess the air pollution sources, Colorado has divided the state into <br />five regions. The proposed Collom lease area lies in the Western Slope Region, which is <br />composed of the counties lying west of the Continental Divide, and several counties just <br />east of the Divide. The largest emissions, in tons per year, are carbon monoxide, due <br />primarily to woodstoves, open burning, and motor vehicles exhausts. The next largest <br />emissions are volatile organic compounds which are primarily vegetation emissions. The <br />third largest emissions are PM10 which primarily originate from woodstoves, unpaved <br />roads, street sanding and motor vehicle emissions. Nitrogen oxides are the fourth largest <br />emissions in the area and come primarily from motor vehicles and other combustion <br />P: PROJECTS ColOw.p RR E4 Final' BI.N1 -..E:a Collom OR it 41 dnc <br />17 <br />