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I I i i EXHIBIT D-3 Page 8 Soil Mapping Unit 7: Dark-colored soils with light=colored subsurfac! horizons of the cold mountain 's lopes Most of this unit is in national forests at elevations about 7,500 feet.. it is all in Colorado except for one area in Utah bordering the La Sal Mountains. This unit is extensive, comprising 22.5 percent of the basin. Precipitation is plentiful and the water yield is high. T'he short growing season limits crop production to hay and pasture. The landscape consists of rolling to steep mountainous terrain with intervening canyons, valleys, and outwash fans. There are many springs and perennial streams. The vegetative cover consists of spruce-fir, ponderosa pine, aspen, oakbrush, and some open grassland areas. About 69 percent of the soils in this unit have dark-colored surface layers, high in organic matter, 7 to 20 inches thick. Underlying this is a light-colored, gray, subsurface layer that is 4 to 16 inches thick. Textures are moderately fine to moderately coarse. Below the gray sub- surface layer is a blocky subsoil that is more clayey than the overlying layers. These horizons are neutral to slightly acid. Gravel and stones are often present. The underlying parent material is sometimes calcareous and is usually at depths of 30 inches or more. About 18 percent of this unit has soils that are less than 20 inches deep over parent materials. included with these soils are rock outcrops. Another 15 percent of the soils have dark-colored surface layers less than 6 inches thick overlying a gray subsurface layer and blocky subsoils. The soils are slightly acid to acid. Poorly drained alluvial soils compose the remaining 3 percent of the unit. Soil Mapping Unit 8: ored soils and rock outcrop of the aline There are seven small delineations of this unit. They encompass high mountain peaks and ridges at elevations above 11,000 feet. This unit is the least extensive in the basin but precipitation and water yield are high. Sediment yield is less than 0.2 acre-feet per square mile per year. The landscape is characterized by rugged mountain peaks with intervening ridges and valleys, all above timberline. Slopes are steep to very steep. This is a windswept area of alpine meadows and rock. 't'his unit is mainly composed of three components. All of the soils have dark-colored surface layers and are acid. About 50 percent of the unit is rock outcrop and talus slopes. About 25 percent is shallow well- drained soils high in organic matter. Surface layers and subsoils are usually rocky or stony with moderately sandy textures overlying bedrock at 20 inches or less. Another 20 percent consists of moderately deep, loamy textured, well-drained turf soils containing stone and gravel. Underlying parent material is at depths of 20 to 90 inches. The remaining 5 percent of the unit consist of poorly drained peat and bog soils in low depressions and drainages. . ~ ~ ~ ~ 1 Q ' ..J ~ J 1. `