2012-01-06_PERMIT FILE - C1982057 (18)

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The following techniques were used to analyze the overburden and underburden sample data. Initially, statistical analyses Imean and standard deviation) were completed to determine the variability between overburden and underburden, and from core to core. Since sampling intervals varied with depth, weighted means were calculated for all physiochemical parameters across all lithology types, excluding topsoil. These means, calculated for each core site, will likely be representative of the physiochemical concentrations that will be present in the dragline, dozer, and scraper handled spoil overburden. Second, the unsuitable composition for each core was determined and utilized To implement effective and efficient overburden handling techniques. Lastly, other mitigative measures are discussed where necessary. Mean physiochemical values for each overburden and underburden parameter are listed by core hole number in Tables 6-4, 6-4A, 6-5, and 6-5A. Approximately 99 percent of all mean values (432) fall within the suitable and marginally suitable ranges as outlined by the assessment criteria listed in Table 6-3. Exceptions for the overburden include the unsuitable nitrate nitrogen for Hole 1128-E and the unsuitable clay for Hole 43-C. Exceptions for the underburden include the unsuitable paste pH for Hote 609-C, the unsuitable nitrate nitrogen for Hole 1728-E, and the unsuitable boron for Hole 43-C. An evaluation of these unsuitable parameters is contained in the Acid- and Toxic-Forming Materials section of Chapter 27. Mean physiochemical values for each overburden and underburden parameter are summarized in Tables 6-6 and 6-7 for the central and northern Seneca II-W study area. All mean values, except the underburden paste pH, fall within the suitable and marginally suitable ranges as outlined by the assessment criteria listed in Table 6-3. Mean physiochemical values for each overburden and underburden parameter are presented in Tables 6-4A and 6-5A for the Seneca 11-W South study area. All mean values fall within the suitable and marginally suitable ranges as outlined by the assessment criteria listed in Table 6- 3. As previously stated the Sage Creek/Wolf Creek chip samples were collected over continuous two-foot vertical intervals and composited into 10-foot intervals for laboratory analysis. The stratigraphic units are predominantly fine-grained, interbedded, sandstone and shales with lesser amounts of sandy shale, siltstone and coal. A lithologic log of drillhole WWCU-24 is included in Appendix 6-1, Lithologic Logs of Bore and Core Holes Used for Cross Section Preparation and Overburden Analysis. The laboratory analytic results for each 10-foot interval were further segregated into four distinct intervals: the Sage Creek overburden interval (50 feet); the upper 60 feet of the Wolf Creek overburden; the lower 50 feet of the Wolf Creek overburden; and 40 feet of the Wolf Creek seam, split and underburden. This segregation allows prediction of the regraded spoil suitability based on the proposed mine plan. The composite samples collected were divided into the following groups for analytical testing. PR03 26 Revised 01/02