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<br />O~"')3" <br />LJ.l... <br /> <br />CHAPTER II--SETTING <br /> <br />GENERAL DESCRIPTION AND LOCATION <br /> <br />The Coal Creek study area is located north of the Oenver metro area and <br />just southeast of the ci ty of Boul der, as shown on the fronti spi ece <br />map. The 81-square-mile Coal Creek Basin drains portions of Adams, <br />Boulder, Gilpin, Jefferson, and Weld Counties. Streams in the area are <br />Coal Creek and South Boulder Creek, both tributaries to Boulder Creek, <br />which in turn is tributary to St. Vrain Creek which flows into the <br />South Pl atte Ri ver. Water for the potenti a 1 Coal Creek Project woul d <br />be furnished from South Boulder Creek. Communities along Coal Creek to <br />be served by the proposed project are Superi or, Loui svi 11 e, Lafayette, <br />and Erie. <br /> <br />ENVIRONMENTAL CHARACTERISTICS <br /> <br />Climate <br /> <br />The project area can generally be described as having abundant sunshine <br />and generally low precipitation and low relative humidity. Throughout <br />thi s part of the Front Range, temperatures can vary wi dely, both on a <br />daily and a seasonal basis. <br /> <br />The climate at the Coal Creek site, which is located in the foothills, <br />is a transition between that of the plains and the mountains. <br />Precipitation ranges between 12 and 18 inches annually. Annual mean <br />temperatures range from 500 to 550 F. Temperatures reach extremes of <br />1000 F in the summer with winter temperatures dropping to _250 F. <br /> <br />The average growi ng season is about 160 days. May 7 is the average <br />date for the last spring killing frost, wi th September 29 the average <br />date for the first fall killing frost, <br /> <br />Prevail ing winds and storms are from the west. "Chinooks" or warm dry <br />winter winds, are common over this area, and displace the cool air that <br />settl es in the vall eys. These wi nds cause temperatures to be more <br />variable and moderate during the winter. <br /> <br />The climate at the Crescent site, elevation 8200 feet, is relatively <br />more severe than in the pl ai ns. At thi s el evati on, heavy wi nter snow- <br />falls are common and the summer growing season is short. Summer <br />temperatures seldom exceed 900 F, and killing frosts are likely to occur <br />throughout the summer. <br /> <br />Physiography and Geology <br /> <br />There are two distinct physiographic provinces present in the Coal Creek <br />study area, the Southern Rocky Mountains and the Great Plains. West of <br /> <br />5 <br />