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BILLINGS SILTY CLAY, 0 to 2 percent slopes, C].sas IIIa band (Ba) This soil is on alluvial materials - 4 to about 40 feet thick - that largely came from Mancos shale. The 8- or 10-inch surface Boil consists of light brownish-gray, j gray, or olive-gray silty clay. The layer is similar to the surface i layer of $illinga silty clay loam soils but it is harder and, in many places, darker. The subsoil consists of similarly colored layers of silty clay loam, silt loam, and silty clay. In places the soil is silty clay to depths exceeding 4 feet. I The entire profile is firm when moist and has a massive structure. The subsoil has many small irregularly shaped light-gray specks or indistinct mottles. Poorly defined light-colored streaks indicate i the presence of lime, gypsum, or salts. The surface soil and subsoil ~ are calcareous, the lime being well distributed. The fine texture o8: the soil greatly retards penetration of roots, moisture, and air. Siu~face runoff is very slow to slow where the slope is leas than 1 percent. Internal drainage is very slow because the subsoil_ie massive and very slowly permeable, Eben with ample drainage ditches, the discharge of irrigation water is slow. I • Tilth and workability are not good, because the soil has a fine texture and a low content of organic matter. Moreover, some fields contain areas 20 to 60 feet across that have excessive amounts of salts. Slick spots also occur. These salty areas and slick spots produce low or negligible yields of moat crops and are extremely difficult to eliminate. Soil limitations are classified as severe for local roads and streets (poor traffic-supporting capacity, moderate to high water tables common), dwellings with basements (high shrink-swell potential, slow internal drainage, subject to water table build up), sanitary land fill (poor drainage, clayey textures),and septic tank absorption fields (slow permeability, poor internal drainage, seasonal high water table}.