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<br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />CHAPTER I I <br />BASIN DESCRIPTION <br /> <br />A. Introduction <br /> <br />This chapter presents a general description of the St. Vrain Basin <br />characteristics and conditions. The description summarizes the physical, <br />environmental and social characteristics as well as information pertaining to <br />the governing entities in the St. Vrain Basin. <br /> <br />B. Physical Characteristics <br />1. Boundaries <br /> <br />'The physical boundaries of the Siting and Study Areas are defined <br />in Chapter I. These areas are shown in Fig. 1-1. <br /> <br />2. Topography <br /> <br />The Siting Area (which includes the Study Area) can be divided into <br />three separate topographic provinces. These provinces are the Front Range or <br />the mountainous western portion of the area, the Hogback or foothi II ridges <br />rising up from the plains, and the plains area or piedmont composing the <br />eastern portion of the area. Elevations within the Siting Area range from a <br />high of 14251 feet at Longs Peak in the Front Range province to a low of <br />4740 feet at the confluence of the St. Vrain and South Platte rivers in the <br />Plains province. <br /> <br />3. CI imate <br /> <br />The rapid variance of topography in the St. Vrain Basin in conjunc- <br />tion with the Basin's mid-latitude location results in localized climatic <br />extremes. The cl imate of the lowest portions of the Basin consisting of the <br />Plains region, is classi fied as semi-arid and receives an average of about <br />13 inches of precipitation per year with the maximum and minimum precipitation <br />generally occurring during the spring and winter months, respectively. Mean <br />annual temperature for the City of Longmont, which is representative of the <br />Plains region, is 48.60F. The mountainous western area of the St. Vrain <br />Basin can receive over 40 inches of precipitation per year with the majority <br />of the precipitation coming from fall and winter snow storms. Mean annual <br />temperature for the high mountain areas as represented by AI lenspark (EI 8500) <br />is 40.50F. <br /> <br />4. Geology <br /> <br />Regional features which are present within the Siting Area boundary <br />are the Front Range, the Denver Basin and the Foothi lis Belt. The Front Range <br />