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1 1 1 1 1 SOILS AND VEGETATION (cont) 100-Nederland very cobbly sandy loam, 15 to 50 percent slopes, This is a deep, well drained soil on shoulders and back slopes of terrace escarpments. This spl formed in cobbly, gravelly, and loamy alluvium derived from mixed sources. The average annual precipitation is 15 to 17 inches, the average annual air temperature is 47° F, and the average frost-free season ~s 126 to 142 days. Elevation is 5,600 to 6,500 feet. Typically, the surface layer is mildly alkaline, dark Gown and brown very cobbly sandy loam about 10 inches thick. The subsoil is neutral, dark brown and strong brown very cobbly sandy clay loam about 50 inches thick. Included in mapping are small areas of Willowman soils on terrace escarpments, Flatirons and Veldkamp soils on terraces, Primen and Leyden soils on hill slopes at the lower edge of the mapped areas, and wet areas bebw springs. Also included are small areas of Urban land. The included soils and Urban land make up about 15 percent of the total acreage. Permeability of this Nederland soil is moderate. The available water Capacity is moderate. The effective rooting depth is 60 inches or more. Runoff is rapid, and water erosion is a severe hazard. Soil blowing is a slight hazard. The shrink-swell potential is low. Rock fragments make up 35 to 75 percent of the volume. In most areas this soil is used for grazing, as pasture, and as habitat for wildlife. In a few areas it is used for community development. The native vegetation is mainly big bluestem, little bluestem, blue grams, mountain muhly, and, on north- lacing slopes, mountainmahogany. The average annual production of air-dry vegetation ranges from 1,000 to 2,300 pounds per acre. Proper grazing use and a planned grazing system are needed to maintain the quality and quantity of the desirable plants and to prevent erosion. Proper grazing use is needed to prevent depletion because this soil is difficult to revegetate. Periodic deferment of grazing during the growing season helps maintain or improve the range condition. The steepness of the slopes limits access by livestock and promotes overgrazing of the less sloping areas. The use of machinery is not practical because the surface is stony and the slopes are steep. Small pastures 24 1 EXHIBIT I/J commonly are severely overgrazed and eroded. Livestock in small pastures should be kept in pens. The rest of the pasture can be used as exercise areas and for very limited grazing. Grasses, shrubs, trees, and garden plants are difficult to establish and maintain because of the slope and large stones. A mulch of plant residue helps reduce runoff, improve filth, and conserve moisture. Applications of manure and of nitrogen and phosphate fertilizers are needed to maintain fertility. Selecting adapted plants is essential in establishing plantings. Planting on the contour helps conserve moisture and reduce erosion. Pebbles and cobbles on the surface should be removed for best results in landscaping, particularly for lawns. Supplemental irrigation is needed at the time of planting and during dry periods. The small areas of Urban land are covered by streets, parking lots, sidewalks, buildings, and other impervious manmade structures. Because runoff is rapid, storm drains, natural drainageways, and land grading must accommodate heavy flows to prevent flooding downstope in areas that normally would not he subject to flooding. The main limitations to use of the soil for homesite development are the slope and large stones. The hazard of erosion increases if the soil is left exposed during site development. Structures to divert runoff from buildings and roads are needed. The steepness of the slope is a limitation for septic tank absorption fields. Absorption lines should be installed on the contour. Effluent from an absorption field can surface downslope and create a health hazard. Cuts and fills should be seeded or mulched. Erosion and sedimentation can be controlled by maintaining an adequate plant cover. This soil is in capability subclass Vlle, in the cobbly Foothill range site, and in plant adaptability group F-5.