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Unit 3: The upper five to eight feet of interburden cdnsistir~g <br />of brown to light brownish gray sandstone. <br />Unit 4: The lower two to three feet of interburden directly <br />above the lower Dakota Coal seam. This unit consists <br />of gray to very dark gray shale. <br />Unit 5: The upper six feet of underburden lying directly below <br />the lower Dakota Coal seam. This unit consists of <br />light gray sandstone ana light gray shale. <br />Overburden, Interburden and Underburden Suitability - Phase II. The <br />criteria for assessing the suitability of overburden or interburden for <br />a root growth medium or aquifer restoration material are as presented in <br />Table 6-9. The suitability limits for each parameter are documented by <br />current literature citings. <br /> The following techniques were used to analyze the Phase II overburden, <br />interburden and and underburden sample data. Initially, statistical <br /> analyses (mean and standard deviation) were completed to determine the <br /> variability between lithologic units and from core to core. Since <br /> sampling intervals varied with depth, weighted means were calculated for <br /> all physiochemical parameters for each lithologic unit, excluding <br /> topsoil. These means will likely be representative of the physiochemical <br /> concentrations that will be present in the scraper and dozer handled <br /> spoiled overburden and interburden sections. Second, the unsuitable <br /> composition for each lithologic unit was determined and utilized to <br /> implement effective and efficient overburden and interburden handling <br /> techniques. Mitigative measures and overburden and interburden handling <br /> techniques are discussed in Tab 21, Minesoil Reconstruction. <br />Mean physiochemical values for each parameter are listed by drill hole <br />number and lithologic unit in Tables 6-10 through 6-14. Approximately <br />85 percent of all mean values fall within the suitable and marginally <br />suitable ranges as outlined by the assessment criteria listed in Table <br /> <br />6-42 Revised 04/11/88 <br />