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Mixing and Mitigation of Unsuitable Overburden Material. Zonas of unsuitable material were identified at thirteen sample locations and are documented by parameter and sample interval in Appendix 6-5. Effective mitigation measures will include avoidance, ameliorating reclamation techniques, and blending, dilution, and/or burial by normal overburden handling. These mitigative measures, also listed in Appendix 6-5, are discussed in further detail in Tab 21, Minesoil Reconstruction. Quality Control and Duplicate Samples. Quality control is an important part of the soil and spoil monitoring program. One aspect of this quality control program is to have the primary laboratory facility complete duplicate analyses on five to ten percent of the total samples and on field-split blind samples. IML completed duplicated analyses on 3 of the 25 samples from the southern mine block. IML also completed duplicate analyses on one field-split blind sample from the southern mine block. The duplicate analyses, presented on the enclosed laboratory reports in Appendix 6-3, were very comparable with the original samples. Variation between the original and duplicate analyses data was not significant enough to change the suitability classification of any sample. Conclusions. Overburden characteristics at the Seneca II-W Mine reflect the variable depositional environments of the coal-bearing strata of the Williams Fork Formation. Although lateral and vertical variability exist, certain distinct physiochemical differences are apparent • between some of the core holes, especially for the parameters pH, saturation percent, conductivity, sulfate, nitrate-nitrogen, sand content, clay content, and manganese. As discussed in the Mixing and Mitigation of Unsuitable Overburden section and Tab 27, Minesoil Reconstruction, none of these parameters will impact overall spoil suitability. In most instances, avoidance and typical overburden handling will effectively blend, dilute, bury, and mitigate potentially inimical zones as documented in Appendix 6-5. The major or significant concern within the Seneca 11-W study area is the excessive clay levels found in the 60 feet of shale strata which overlies the Lennon coal seam. A less significant or minor concern is the potential acidity associated with the Lennox coal seam and encapsulating strata. These strata will be encountered primarily between the Lennox coal outcrop and final highwall in the northwestern portion of the mine as shown on Exhibit 6-6, and in the southern mine block as shown on Exhibit 6-6A. Typical • 33 Revised 9/g8