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1 <br />1 <br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br />1 <br />1 <br /> <br />1 <br />1 <br /> <br /> <br /> <br /> <br />1 <br />SOILS AND VEGETATION (cont) <br />45-Flatirons very cobbly sandy loam, 0 to 3 <br />percent slopes. This is a deep, well drained soil on high <br />terraces and piedmonts. It formed in noncalcareous, <br />stony to gravelly, and loamy material of the Rocky Flats <br />Alluvium. The average annual precipitation is 15 to 17 <br />inches, the average annual air temperature is 47° F, and <br />the average frost-free season is 126 to 142 days. <br />Elevation is 6,000 to 6,600 feet. <br />Typically, the surface layer is neutral and slightly acid, <br />very dark grayish brown very cobbly sandy loam about <br />13 inches thick. The subsoil in the upper 8 inches is <br />medium acid, reddish brown very gravelly clay; in the <br />next 26 inches it is slightly acid and neutral, strong <br />brown very gravelly sandy clay; and below that to a <br />depth of 60 inches it is neutral, strong brown very <br />gravelly sandy clay loam. <br />Included in mapping are small areas of calcareous <br />soils near the edge of terraces, Veldkamp soils in <br />positions similar to those of the Flatirons soil, soils near <br />the mouth of Coal Creek Canyon that have a very stony <br />surface layer, and soils that have a dark surface layer <br />more than 20 inches thick and are on mounds. Also <br />included are small areas of Urban land. The included <br />soils and Urban land make up about 15 percent of the <br />total acreage. <br />Permeability of this Flatirons soil is slow. The available <br />water capacity is low. The effective rooting depth is 60 <br />inches or more. Runoff is slow, and water erosion and <br />soil blowing are slight hazards. The shrink-swell potential <br />is moderate. Rock fragments make up 35 to 80 percent <br />of the volume. <br />This soil is used mainly for grazing and as habitat for <br />wildlife and recreation areas. In a few areas it is used for <br />community development. <br />The native vegetation is mainly big bluestem, little <br />bluestem, needleandthread, and mountain muhly. The <br />average annual production of air-dry vegetation ranges <br />from 1,000 to 2,300 pounds per acre. Proper grazing use <br />and a planned grazing system are needed to maintain <br />the quality and quantity of desirable plants and to <br />prevent erosion. Periodic deferment of grazing during the <br />growing season helps maintain or improve the range <br />condition. This soil is difficult to revegetate; therefore, <br />proper grazing use is needed to prevent depletion. <br />Mechanical treatment is not practical because the <br />surface is stony. Small pastures commonly are severely <br />overgrazed and eroded. Livestock in small pastures <br />should be kept in pens. The rest of the pasture can be <br />used as exercise areas and for very limited grazing. <br />Grasses, shrubs, trees, and garden plants are difficult <br />to establish and maintain on this sail because of the <br />large stones. Applications of manure and commercial <br />fertilizers that contain nitrogen and phosphorus are <br />needed to maintain fertility. Selecting adapted plants is <br />22 <br />EXHIBIT I/J <br />essential in establishing plantings. Pebbles and cobbles <br />in disturbed areas should be removed from the surface <br />for best results in landscaping, particularly for lawns. <br />Supplemental irrigation is needed at planting time and <br />during dry periods. <br />The areas of Urban land are covered by streets, <br />parking lots, sidewalks, buildings, and other impervious <br />manmade structures. Because runoff is rapid, storm <br />drains, natural drainageways, and land grading must <br />accommodate heavy flows to prevent flooding <br />downslope in areas that normally would not be subject to <br />flooding. <br />This Flatirons soil is limited for homesite development <br />by the large stones, the shrink-swell potential, and the <br />slow permeability. Excavating this soil for buildings and <br />roads is difficult because of the large stones, and large <br />equipment may be needed. The effects of shrinking and <br />swelling can be minimized by proper engineering design <br />and by backfilling with material that has a low shrink- <br />swell potential and installing surface and subsurface <br />drains near foundations. Properly installed the drains <br />below the foundation and minimal surface watering near <br />the foundation help prevent seepage into basements and <br />minimize the effects of shrinking and swelling. Special <br />sewage systems must be installed because of the slow <br />permeability. Erosion and sedimentation can be <br />controlled by maintaining an adequate plant cover. <br />This soil is in capability subclass Vlls, in the cobbly <br />Foothill range site, and in plant adaptability group F-5. <br />