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Chemical Properties and Natural Fertilin -The soils of mapping unit number X30 have for the most <br />• part the same natural fertility as the soils in mapping unit number 30, but the chemical analyses differ. <br />i\1annine Unit Number 31 - Moderately deep (20 to 40 inches to bedrock) and deep (more than 40 <br />inches to bedrock), dark colored, well drained, fine textured (more than 35 percent clay), maturely <br />developed soils having an Al, B2t, C horizon sequence with well developed horizons of silicate clay <br />accumulation (B2t horizon), occurring in parts of the mine area where the mean summer soil temperature <br />(June, July, and August mean temperature measured at 20 inches) is 59°F or warmer. <br />Classification of Maior Components -The components listed below comprise the major part of the <br />mapping unit: <br />A. Acidic Argiustolls (Chesnut Soils). <br />1. Fine, montmorillonitic, mesic Camily. <br />(Ryas Series) <br />(Emigrant Series) <br />(Dag0at Series) <br />B. Pachic Argiustolls (Chesnut Soils). <br />1. Fine, montmorillonitic, mesic family. <br />(Series unidentified) <br />C. Acidic Argiborolls (Chernozems). <br />1. Fine, montmorillonitic family. <br />(Holdcrness Series) <br />(Morop Series) <br />• (Absarokee Series) <br />D. Typic Argiborolls (Chernozems). <br />1. Fine, montmorillonitic famil}•. <br />(Work Scrics) <br />E. Pachic Argiborolls (Chernozems). <br />1. Fine, montmorillonitic family. <br />(Hughes Series) <br />Extent and Maior Areas of Occurrence -Mapping unit number 31 has a large to[o] acreage and occurs <br />throughout the mine area at elevations less than 7,800 feet. The largess areas occur in the western, <br />central, and northern parts of the mine area. <br />Characteristic Tonoeranhv -These soils occur on moderately to steeply sloping hill and valley topoera- <br />pM. Ty~picalh~ they occupy side hill locations, but unless bedrock is close to the surface, they occur on hill <br />and ridge crests as well. Slopes range from about 3 to 60 percent. <br />Pht~sical Properties - The soils of mapping unit number 31 are mature sails having distinct genetic <br />horizonatton and well developed stable soil structure. This structure is essential to the tree movement of <br />air, water, and plant roots through the soil. IF these soils are to be used for new seedbeds, it is important <br />that this natural structure be preserved. <br />The soils of this unit are tine textured (more than 35 percent clay) and are subject to packing if traversed <br />by heavy machinery and are irreversibly paddled into dense impermeable masses if handled wet. They can <br />. be successfully worked over only a narrow range of soil moisture w~thou[ loss of desirable physical <br />properties. Consequently, an}• operations involving the revegetation of disturbed, transported, and <br />relocated materials from these soils will need to be very carefully managed. Because of their rather severe <br />