1988-04-11_PERMIT FILE - C1981008A (4)

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