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Mountain Coal Company Exhibit 27 West Elk Mine Characteristics of West Elk Mine Soil Mapping Units Physical Progenies -The soils of mapping unit number ~ are young soils and lack well- developed soil structure. They contain a high proportion of silt and clay which. in conjunction with their lack of good soil structure, makes careful soil management a requisite in any operation requiring good permeabili[y and aeration after disturbance. They are very susceptible to packing if traversed by heavy machinery and are easily irreversibly puddled if handled when too wet. These soils have high shrink/swell potentials with coefficients of linear extensibility ranging from 0.0? to 0.19 and a ~0-inch section ranging froth about one to four inches. When wet they are very slippery and sticky. These soils are considered to have poor workability (where workability is the ability to be disturbed or transported without serious physical change). They can be worked over only a narrow range of soil moisture conditions. Without good natural soil structure to assist in maintenance of desirable physical characteristics they tend to form large and extremely hazd irregular clods that are difficult to work in[o good seedbeds with conventional machinery and practices. • In their native condition these soils are subject to moderate overflow due to runoff and are moderately susceptible to water erosion, especially gullying and Tilling. Under native cover they are not susceptible to accelerated wind erosion unless badly overgrazed. When disturbed or cleared, their susceptibility to both wind and water erosion increases, although their natural coarse cloudiness tends to moderate wind erosion. Some tendency toward mass movement is seen in the soils of this mapping unit, particularly in the southwestern part of the mine plan area. The potential for such movement is considered moderate under normal conditions and could become greater if additional moisture is incurred, particularly if natural vegetative cover is destroyed or reduced. Chemical Properties and Natural Fertility -These soils are only moderately weathered and. with the exception of a few places, they are calcareous throughout. Accumulation of secondary carbonate in definite genetic horizons has not occurred except under a few of the more strongly developed soils having weak B horizons. .-llthough they have free carbonate throughout the root zone, excess calcium or magnesium carbonates are not a problem to soil fertility. Sodium or other soluble salts were not observed to have concentrated in detrimental amounts except where these soils were associated with seepage. (See ranges of soil • properties used in mappingl. The occurrence of some evidence of detrimental salinity in areas of these soils does occur and makes them somewhat suspect. Exhibit 27-6