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Mountain Coal Company Exhibi['_7 <br />West Elk Mine Characteristics of West Elk Mine Soil lvlapping units <br />The soils of this uni[ also have wide shrink/swell ratios. Coefficients or linzar <br />extensibility (ratio of volume of dry to moist soil) ranges from 0.0~ to O.l~ uith an <br />average of about 0.1. Total potential extensibility of a 40 inch section ranges from 2.0 <br />to 6.0 inches. In addition. the soils of this unit are very sticky and slippery when •x•et. <br />Normally, the soils of this unit are not subject to serious Flood hazards although a few <br />of the lower footslopes may flood occasionally. Soil erosion is not usually acczlerated <br />unless native veeetation is destroyed or depleted. 'hen disturbed they bzcome <br />moderately susceptible to wind and water erosion and control measures should be uszd. <br />No tendency towards mass movement within areas mapped was noted but the potential <br />is moderate. Any changes in supplemental water on sloping areas will increase <br />movement possibilities. <br />Chemical Properties and Natural Fertility -The soils of mapping unit number 17 have <br />the same chemical properties and natural fertility description as the soils of mapping unit <br />number 16. However, laboratory values may vary slightly. <br />Mappine Unit Number 18 - Moderately deep (20 to 40 inches to bedrock) and deep <br />• (more than 40 inches to bedrock), light colored, gravelly and cobbly, fine textured (more <br />than 35 percent clay), maturely developed soils having horizons of secondary silicate clay <br />accumulation (B2t horizons) and occurring in parts of the study area where the meant <br />summer soil temperature (June. July, and August temperature measured at 20 inches) is <br />59° or warmer. <br />Classification of Major Components <br />The components listed below comprise the major part of the mapping unit: <br />A. Ustollic Haplargids (Brown Soils). <br />1. Clayey-skeletal, montmorillonitic, mesic. <br />(Nehar Series) <br />Extent and Major Areas of Occurrence <br />Soils of mapping unit number l8 occur in small acreage in the study area and is found <br />principally on the steeply sloping edges of mesas and hills in the southwestern pan of the <br />study area west of Minnesota Creek. <br />• <br />Exhibit 27-13 <br />