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State Reg. overburden often contains greater volumes of sandstone, with associated higher concentrations of iron, manganese, arnj carbonates. The lowest acid-base poteni•ial and highest clay contents are associated with shale units immediately above coal beds in both overburden and underburden. Conductivities generally increase from ground surface down to the coal beds. Wadge coal underburden (Cores 2306, 1900) is more sodic than Wolf Creek underburden. A comparison of summary statistics between overburden and underburden material indicate that similar mean values exist for both sections. Slightly higher values of silt, calcium, magnesium, manganese, zinc, and phosphorus are found in overburden. Concentrations of sand, pH, sodium, SAR, iron, and potassium are slightly higher in underburden. Several inimical zones were identified for seven physiochemical parameters as set forth by overburden assessment criteria in Table 6-3. These zones are thoroughly documented by parameter in the following section. The section is provided in order to assess and correlate • overburden characteristics with acidity, alkalinity, nutrient toxicity, nutrient deficiency, and aquifer suitability and to recommend mitigation measures were necessary. Overburden Mixing and Mitigation of Inhibitory Material. Inhibitory material was identified in six cores and is documented by parameter and depth increment in Table 6-7. These zones comprise from 1.8 to 40.0 percent of the individual overburden core volume (Table 6-6). Effective mitigation measures include avoidance, chemical amendments, and spoil dilution by overburden mixing. Mitigation of zones with high sand concentrations and high SAR levels will be by avoidance. These inhibitory zones occur solely in the underburden. Therefore, they will not be disturbed during mining. • 6-26