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well the overburden is mixed when dumped from the dragline bucket, and if this mixing is sufficient to mitigate high pH and manganese concentrations. RESPONSE: At Seneca, overburden mixing occurs during three separate mining operations: cast blasting, normal dragline spoiling, and grading by dozers and/or scrapers. Initially, the overburden is drilled using a specific pattern which, when time blasted, will move a significant amount of overburden into the adjacent pit. Subsequently, the remaining fractured overburden is casted or spoiled into the adjacent pit. Lastly, spoil is redistributed by push dozers and/or scrapers until final contours are achieved. Mixing efficiency can be ascertained by comparing specific parameter concentrations in overburden and regraded spoil. Six tracer parameters (pH, ABP, EC, Ca, Mg, Mn) were selected following an intensive review of the baseline chemical and physical data presented in Appendix 6-3 for Wolf Creek mining area Core Hole Sites 2131E, 2149E, 2424E, and 243E3E. Each of tiie six parameters exhibits a unique concentration/depth relationship in undisturbed overburden. Consequently, the degree of variation from this relationship across the regraded spoil landscape will indicate the approximate degree of mixing or dilution which occurs during the mining and reclamation process. Spoil samples from the Wolf Creek mining area are currently collected on a 300-foot horizontal grid prior to topsoil replacement. At each sample site, the upper one to four feet of spoil is collected with a 3 1/4-inch bucket auger. Once the lithologic description is obtained, about three to four pounds of spoil is placed and sealed in 4-ml thick polyethylene storage bags and shipped to the laboratory for analysis. All sample locations are denoted on the enclosed Exhibit 9-4, Postmine Topsoil and Spoil Sample Locations. Laboratory data is presented in Table 1. • 2