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<br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />3.2 <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />areas along major streets. <br /> <br />Soi ls in the higher elevations consist mainly of sandy loams <br />with occasional granite outcroppIngs. The lower elevations are <br />less permeable and are classified as clayey loams. <br />lIydrologically, the upper basins consist mainly of "B" type <br />soils, the lower basIns "C" type soils, and the intermediate <br />basins "B/C" type soils. <br /> <br />As run()ff comes down off the western most subbasins, it <br />concentrates i,n two more or less parallel natural channels <br />(east of Cheyenne Mountain lIigh School) that exist for <br />approximately 2,500 feet and 1,800 feet, respectively, before <br />reachIng Vista Place. At this point, the channels disappear <br />and flow travels down Mercury Drive and Skyway Boulevard to <br />meet at the intersection of these two streets. The combined <br />flow then follows Skyway Boulevard until it reaches Saturn <br />Drive, continues eastward on Saturn Drive and is joined by flow <br />from the northern subbasIns C-l, C-2, and C-3 (as seen in <br />Figure 3.1). <br /> <br />Crossing under 8th Street, the stream enters a 96 inch CMP <br />culvert for 1,000 feet, before resurfacing in a well- <br />established channel at Laclede Street. This 4,500 foot channel <br />with a slope of approximately 2% conveys the streamflow the <br />remaining distatlce to the confl\lenCe of Cheyenne Creek. <br />Assuming the longest of the upstream parallel channels, the <br />full length of Cheyenne Run below Cheyenne Mountain lIigh School <br />is 2.0 miles, with an average slope of 3%. <br /> <br /> <br />Storm sewers within the watershed are not well developed. <br />Rainfall runoff reaches the main channel prImarily by means of <br />overland flow along streets and gutters. <br /> <br />The EngIneerlng Studv 2..f the Southwest Area praInage BasIn <br />(ESSW) {Reference 12), is the only detailed study of the basin <br />available for review. <br /> <br />PrevIous Studies <br /> <br />The hydrology conducted for the ESSW utilIzed significantly <br />dI fferent parameters than outlined under the current DCM. The <br />desIgn storm was a 6-hour event occurring under AMC II <br />conditions. The total raInfall depth of 3.5 inches under a <br />Type IIA distribution was used. Peak discharge results at the <br />confluence with Cheyenne Creek are shown in Table 3.1. <br /> <br />15 <br /> <br />R€~OURC€ CON~UlTI\NT~ INC <br />