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1 <br /> <br /> <br /> <br />1 <br /> <br />LJ <br />1 <br /> <br />1 <br /> <br /> <br />1 <br />1 <br /> <br />1 <br />1 <br /> <br /> <br />SOILS AND VEGETATION (cont) <br />46-Flatlrons very stony sandy loam, 0 to 5 <br />percent slopes. This is a deep, well drained soil on <br />undulating, dissected fan piedmonts. It formed in <br />noncalcareous, cobbly, stony, gravelly, and loamy <br />material of the Rocky Flats Alluvium. The average <br />annual precipitation is 15 to 17 inches, the average <br />annual air temperature is 47' F, and the average frost- <br />free season is 126 to 142 days. Elevation is 6,000 to <br />6,600 feet. <br />Typically, the surface Layer is neutral and slightly acid, <br />very dark grayish brown very stony sandy loam about 13 <br />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, and soils <br />that have a very cobbly surface layer and are near the <br />eastern limit of the map unit. Also included are small <br />areas of Urban land. The included soils and Urban land <br />make up about 15 percent of the 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 />In most places this soil is used for grazing and as <br />wildlife habitat and recreation areas. In a few places it is <br />used for 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 prevent <br />erosion. Periodic deferment of grazing during the growing <br />season helps maintain or improve the range condition. <br />This soil is difficult to revegetate; therefore, proper <br />grazing use is needed to prevent depletion. Mechanical <br />treatment is not practical because the surface is stony. <br />Small pastures commonly are severely overgrazed and <br />eroded. Livestock in small pastures should be kept in <br />pens. The rest of the pasture can be used as exercise <br />areas and for very limited grazing. <br />Grasses, shrubs, trees, and garden plants are difficult <br />to establish and maintain on this soil 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 />essential in establishing plantings. Pebbles and cobbles <br />23 <br />EXHIBIT I/J <br />on the surface should be removed for best results in <br />landscaping, particularly for lawns. Supplemental <br />irrigation is needed at planting time and during dry <br />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 use as homesites by <br />the large stones, the shrink-swell potential, and the slow <br />permeability. Excavating this soil for buildings and roads <br />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 file 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. Erasion 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 />