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III IIIIIIIIIIIIIIII <br />999 _ <br />/j/~ Doc Date:12111/2001 <br />il,I~2.6 SOILS <br />J~ The soil descriptions, identifications, and locations as shown on Map M29 were <br />determined by an~Order 1 Soil Survey of the proposed mine plan area in the Summer <br />of 1979 by Western Ecological Services Company. <br />The principal geologic units that occur in the proposed mine plan area and that <br />have influenced soil development are [he three most common ones of the Mesaverde <br />group, i. e. the Lewis Shale, the Williams Fork Formation and the Iles Formation, <br />all of which are Cretaceous (refer to Section 2.7.1). <br />The Lewis shale is composed of dark gray homogeneous marine shale which lies <br />unconformably on [op of the Williams Fork Formation. I[ is located in the north- <br />- western portion of the proposed mine plan area. The Williams Fork Formation is <br />composed of light brown to white sandstone, gray shale and coal beds. It is the <br />upper bedrock unit of the Mesaverde Group and occurs in the southern and eastern <br />portion of [he proposed mine plan area. The Iles Formation is the older of the <br />two formations comprising the Mesaverde Group and is lithologically similar to <br />the Williams Fork Formation. It occurs in [he southwestern corner of the pro- <br />posed mine plan area. <br />Aeolian (wind-blown) material is a significant factor in terms of quaternary geo- <br />logy as it imparts a finer texture to [he soils in the study area. <br />. ~ <br />Areas of glacial erra[ics were also noted on knolls within the survey boundaries, <br />but their aerial distribution was too small to be mapped out. 1J <br /> <br />-~~ <br />2.6.1 Soil Features <br />Most of the soils developed in [he proposed permit area are deep (40 to 60 <br />~ I <br />inches) and develop from colluvium and some alluvium derived Erom interbedded <br />~~ eands[one. Effective soil rooting depths, in the western portion of [he proposed <br />2-182 <br />