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• Any practice involving the addition of large amounts of water to areas of mapping unit number X32 will <br />enhance this potential for mass movement. <br />Chemical Properties and Natural Fertility -The soils of mapping unit number X32 have for the most <br />part the same chemical properties and natural fertility az the soils of mapping unit numbers X31 and 31, <br />with the exception of heavy, dense, expanding, and contracting materials which have an effect on plant <br />nutrient availability. laboratory analysis may vary, however. <br />Manning Unit Number 33 -Moderately deep (20 to 40 inches to bedrock) and deep (more than 40 <br />inches to bedrock), dark colored, well drained, maturely developed, very gravelly, and cobbly clayey soils <br />(more than 35 percent clay in the fine earth), having an Al, B2t, C soil horizon sequence with well <br />developed horizons of silicate clay accumulation (B2t horizons) occurring in parts of the mine area where <br />the mean summer soil temperature (June, July, and August mean temperature meazured at 20 inches) is <br />59'F or warmer. <br />Classification of Major Com~nents -The components listed below comprise the major part of the <br />mapping unit: <br />A. Aridic Argiustoll (Chesnut Soils). <br />1. Clayey-skeletal, montmorillonitic, mesic family. <br />(Series unidentified) <br />B. Aridic Argiboroll (Chernozem). <br />1. Clayey-skeletal, montmorillonitic family. <br />(Radersburg Series) <br />• Extent and Major Areas of Occurrence -Mapping unit number 33 haz a small total acreage and occurs in <br />the western part of the mine area at elevations less than 7,800 feet. <br />Characteristic Tooogranhv -The soils of this unit occur on moderately to steeply sloping hills and ridges. <br />Slopes range from about 4 to 60 percent. <br />Physical Properties -The soils of mapping unit number 33 are mature soils having strong, stable, blocky, <br />and granular structure. They are also fine textured and contain at least 35 percent gravel, cobble, and <br />stone by volume. Although with careful management these soils could be used as seedbed material <br />without loss of the structural properties essential to water, air, and plant root movement, their steep slopes <br />and content of coarse fragments make them poor choices for seedbed materials. <br />Thc fine earth portion of these soils has a wide shrink/swell ratio but this is partially offset by the content <br />of coarse fragments. Total potential extensibility of a 40-inch section with 50 percent gravel and cobble is <br />about 0.8 to 1.6 inches. <br />No tendenry toward mass movement is seen in this unit in the mine area; however, the potential for such <br />movement is moderate because of the character of the landforms on which the unit occurs. Practices <br />involving large amounts of water on these soils or on adjacent soils will enhance this potential for mass <br />movement. <br />In their native state the soils of this unit are moderately susceptible to water erosion, particularly where <br />the natural vegetation has been destroyed or depleted, but they are not very susceptible to wind erosion. <br />If cleared or disturbed they are very susceptible to water erosion and moderately susceptible to wind <br />erosion. <br />• Chemical Properties and Natural Fertility -These soils are moderately weathered and mature, with distinct <br />genetic horizonation including horizons of silicate clay accumulation and wnsistent horizons of secondary <br />