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<br />SECTION III <br />FEASIBILITY STUDY <br /> <br />1. PROBLEM DESCRIPTION <br /> <br />{&mmunity Description <br /> <br />The City of Sterling is the county seat for Logan COlillty. TIle City is located approximately 125 miles <br />northeast of Denver, and 126 miles southeast of Cheyenne, Wyoming. Sterling is the largest <br />community in Logan County, having a population of about 11,000 (1995 estimate). The total <br />population within Logan County i~: about 19,000 (1995 estimate). The climate of Sterling is primarily <br />affected by northwestern winds. The average annual precipitation is 19 inches and thle average annual <br />snowfall is 39.4 inches. The mean annual temperature is 48.60 F., and the average annual number of <br />clear days is 299. The coldest month is January with a mean temperature of 38.80 F. and the warmest <br />month is July with an average temperature of 89.0" F. The topography of the City consists of high <br />rolling plains, with the predominate feature being the South Platte Rivl:r which flows through the City <br />and County from the south to the north. The South Platte River floodplain is broad and relatively flat. <br />Sterling is bisected from southwest to northeast by State Highway 6 and a parallel railroad track <br />operated jointly by BNRRlUPRR. <br /> <br />Pawnee Creek is a left bank tributary to the South Platte River and drains an area of about 645 square <br />miles. The upper portions of the basin are located in Wdd County, and the lower portion, along with <br />the confluence with the South Platte River are located in Logan County. The mouth of the creek is <br />located about 5 miles southwest of Sterling and about I mile northeast of Town of Atwood in Logan <br />County. The watershed elevation ranges from about 3,980 feet to 5,400 feet. The soils in the basin are <br />mostly loams and clay loams, with sandstone, shale, and siltstone outc:roppings. Land use consists of <br />open range land and a significant amount of irrigated cropland in the lower part of the basin. Several <br />major and many minor irrigation canals and ditches cross the study area, generally flowing parallel to <br />the South Platte River. Significant among the canals are the Pawnee Ditch, Springdale Ditch, and the <br />Sterling No. I Ditch. <br /> <br />HWY 6 and the BNRRlUPRR em'bankments are major obstructions which divert Pa"mee Creek flood <br />flows from the main channel towards the City of Sterling. The Town of Town of Atwood is located <br />near the natural floodplain of Pa"mee Creek, however, the City of Sterling is not. TIle flood flows <br />from Pawnee Creek into Sterling are mainly due to the manmade embankments which act as diversion <br />structures since flood flows on Pavmee Creek are not entirely able to pass directly to the South Platte <br />River through the existing bridges or over the embankment5. When flows are high enough, a portion <br />of the flow is diverted to Sterling along the northwest side of the highway and railroad embankments. <br />This situation is known as the "Pawnee Overflow". Reference is made to Figure 2 which presents a <br />vicinity map of the area. <br /> <br />III-l <br />