PERMFILE68955 - Laserfiche WebLink

Home Browse Search

n LJ r~ ~J • Unit 6: The upper ten feet of underburden lying direct{y below the lower Dakota coal seam. The unit consists of very hard to extremely hard, indurated light gray to light brownish gray sandstone. These lithologic unit designations are typical for the Dakota Sandstone Formation and are similar to those utilized in Mine Pit Areas 2, 3, and 5 at the New Horizon 1 mine area. The lithologic unit designations for the New Horizon 2 study area are included with the lithologic descriptions in Peabody Appendix 6-1. Overburden, Interburden, and Underburden Suitability The criteria for assessing the suitability of overburden or interburden for a root growth medium or aquifer restoration material are as presented in Table 2.04.6-3. The suitability limits for each parameter are documented by current literature citings. The following techniques were used to analyze the Phase I and Phase II overburden, interburden, 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 physicochemical parameters for each lithologic unit, excluding topsoil. These means will likely be representative of the physicochemical 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. Lastly, other mitigative measures are discussed where necessary. Mean physicochemical values for each parameter are listed by drill hole number and lithologic unit in Tables 2.04.6-4 through 2.04.6-8. Approximately 93 percent of all mean values (239) fall within the suitable and marginally suitable ranges as outlined by the assessment criteria listed in Table 2.04.6-3. Exceptions include the unsuitable pH values for Unit 2 (Hole 871 E) and Unit 4 (Holes 872E and 886E), the unsuitable SAR for Hole 882E (Units 2, 3, and 4); and the unsuitable acid base potential values for holes 870E, 871 E, 881 E, 882E (Units 2 and 4) and for Unit 4 (Holes 872E and 886E). An evaluation of these unsuitable parameters is contained in the Mitigative Measures section. Revised 9/99 2.04.6-23