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West Elk Mine Acid-Base Potential of Roof and Floor Samples from the B Seam, E Seam, and F Seam in the Permit Area The Acid-Base Potential (ABP) is a measure of how effectively the neutralization potential (alkalinity) present in solid samples will neutralize the acid producing potential of the sample resulting from sulfur present as sulfide (pyritic sulfur). Total sulfur may be used to represent the move conservative, maximum potential acidity. The ABP represents the amount of calcium carbonate (CaC03-equivalent that is present in excess of the amount needed to neutralize the acid potentially produced from oxidation of sulfur in the sample. The ABP (in tons of CaC03-equivalent per 1000 tons of material) is calculated from: ABP = (neutralization potential) - (31.25)(wt% pyritic sulfur or total sulfur). If the ABP is positive, leachate from the sample would be basic; if negative, leachate would be acidic. Any rock or earth material with an ABP of -5.0 tons of CaC03 equivalent per 1000 tons of material, representing a soil with a net potential deficiency of 5.0 tons of CaC03 equivalent per 1000 tons of material, is generally defined as a potentially toxic material (A.A. Sobek, W.A. Schuller, J.R. Freeman, and R.M. Smith, Field and Laboratory Methods Applicable to Overburdens and Minesoils, EPA=600/2-78-054). Table 64 summarizes some of the data in Exhibit 13. It shows weighted-average APB values calculated for samples taken from the strata enclosing the B, E, and F Seams. None of the overburden or floor strata for the B, E, or F Seams is potentially toxic, i.e., none has an ABP < -5.0 tons of CaC03 equivalent per 1000 tons of material. The weighted average of all strata has a positive ABP of +25.3, indicating that a substantial excess neutralizing potenfial exists in the enclosing strata. In addition, 109 other samples from strata adjacent to the B, E, and F Seams were analyzed for sulfur forms. Pyritic sulfur in these samples, ranged between 0.01 percent and 3.03 percent, with a mass-weighted average of 0.14 percent. These low values are consistent with those used in the acid-base accounting and similarly indicate no acid producing potential. For a composite of these samples, a neutralization potential of only 4.4 tons of CaC03 equivalent per 1000 tons of material would be required to obtain an ABP equal to zero. The weighted average of all measured neutralization potentials from similaz sample materials was 32.9 tons of CaC03 equivalent per 1000 tons of material, or about 7.5 times larger than necessary for complete neutralization of acid from pyritic sulfur. Using the value of 32.9 tons of CaC03 equivalent per 1000 tons of material, a calculated ABP for the 109 samples is +28.5, approximately the same as for the samples in Table 64. Therefore, the materials tested from the B, E, and F Seams show no potential for producing acid leachate. Assessment of Refuse Material Disposal ImQacts on Groundwater Mining generates refuse consisting largely of non-coal earth materials and low quality coal. The • refuse is separated from the coal at the screening plant and rotary breaker or in the mine by two- cycle development mining techniques. The refuse is presently treated as coal processing waste. 2.05-151 Revised November 2004 PRIO