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6. Five lithologic units were formulated for Mine Areas 2 and 3. <br />These include Unit 1 - Sandstone and shale overburden; Unit 2 - <br />Upper Dakota coal seam and encapsulating very dark gray, <br />carbonaceous shale; Unit 3 - Interburden sandstone; Unit 4 - Lower <br />interburden shale; and Unit 5 - Underburden. <br />7. Acidic and moderately saline overburden and interburden are the <br />primary concerns in Mine Areas 2 and 3. Secondary concerns include <br />the occasional, excessive levels of iron and saturation percentage <br />and the deficient levels of nitrogen and phosphorous. <br />8. Lithologic Units 2 and 4 are unsuitable due to low pH and ABP and <br />will not be replaced in the upper 3 feet of regraded spoil. <br />9. Lithologic Units 1 and 3 are the most desirable suitable <br />topdressing materials. <br />/• <br /> <br />6-54 Revised 04/11/88 <br />