Laserfiche WebLink
Unit 6: The upper ten feet of underburden lying directly below the lower Dakota coal <br /> seam. The unit consists of very hard to extremely hard, indurated light gray to <br /> light brownish gray sandstone. <br /> These lithologic unit designations are typical for the Dakota sandstone formation and are <br /> similar to those utilized in Mine Pit Areas 2, 3, and S at the Nucla Mine (see Tab 6, <br /> Volume 2, SMP C-008-81). The lithologic unit designations for the Nucla East study area <br /> are included with the lithologic descriptions in Appendix 6-1. <br /> Overburden, Interburden, and Underburden Suitability <br /> The criteria for assessing the suitability of overburden or interburden for a root growth <br /> medium or aquifer restoration material are as presented in Table 6-1-3. The suitability <br /> limits for each parameter are documented by current literature citings. <br /> The following techniques were used to analyze the Phase I and Phase II overburden, <br /> interburden, and underburden sample data. Initially, statistical analyses (mean and <br /> standard deviation) were completed to determine the variability between lithologic units <br /> and from core to core. Since sampling intervals varied with depth, weighted means were <br /> calculated for all physiochemical parameters for each lithologic unit, excluding topsoil . <br /> These means will likely be representative of the physiochemical concentrations that will <br /> be present in the scraper and dozer handled spoiled overburden and interburden sections. <br /> Second, the unsuitable composition for each lithologic unit was determined and utilized to <br /> implement effective and efficient overburden and interburden handling techniques. Lastly, <br /> other mitigative measures are discussed where necessary. <br /> Mean physiochemical values for each parameter are listed by drill hole number and <br /> lithologic unit in Tables 6-1-4 through 6-1-8. Approximately 93 percent of all mean <br /> values (239) fall within the suitable and marginally suitable ranges as outlined by the <br /> assessment criteria listed in Table 6-1-3. Exceptions include the unsuitable pH values <br /> for Unit 2 (Hole 871E) and Unit 4 (Holes 872E and 886E); the unsuitable SAR for Hole 882E <br /> (Units 2, 3, and 4); and the unsuitable acid base potential values for holes 870E, 871E, <br /> 881E, 882E (Units 2 and 4) and for Unit 4 (Holes 872E and 886E). An evaluation of these <br /> unsuitable parameters is contained in the Mitigative Measures section. <br /> Mean chemical values for seven additional parameters are listed in Table 6-1-9. No <br /> 6-1-26 Revised 04/11/88 <br />