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The analyses of leachate water, shown in Exhibit 27, Column Leach Study of Mine Waste Material, were compared to existing pit water chemistry shown in Table 50, Energy Mine No. 1 Pit Water Quality. The average concentrations of major cations and anions were convened to milli-equivalents per liter and plotted on a piper diagram, shown in Figure 10, Leachate Chemistry, Energy Mine No. 1. In addition, the average concentrations of major ions in ground water adjacent to the Energy Mine No. 1 pit were plotted. The piper diagram shows similaz water chemistry for leachate from underground mine waste and existing undisturbed overburden aquifer, although the leachate water has much higher concentrations initially. These waters show asodium-sulfate dominance. The water quality of the Mine 1 Pit shows acalcium-sulfate dominance, which indicates a large proportion of surface runoff. As previously stated, leachate water will percolate into the adjacent overburden aquifer under the influence of potentiometric head. An analysis of solute transport through the aquifer was performed, using flow equations to model a plume of saline water as it would be distributed in a confined aquifer with time. The equations which describe the travel of dissolved solids through an aquifer are the same as those used in tracer dye studies of porous media. The equations contain complex mathematical functions which can be solved by algebraic approximations. The basic components of the equations are: 1) Aquifer characteristics; 2) The rate of ground water flow; 3) Concentration of dissolved solids; 4) Values of longitudinal and transverse dispersivity; and 5) Retardation Factors to account for ion exchange, solute absorption, and radioactive decay. Aquifer characteristics aze determined from pump tests and drillhole data presented earlier. The rate of ground water flow is calculated from the average permeability and potentiometric gradient within the overburden aquifer in this area. Concentration of dissolved soils for these tests was measured through column leaching studies as shown in Figure 9, Predicted Leachate Concentration, Energy Mine No. 1. Dispersivity is a parameter which is difficult to measure in the field and must be assumed. Dispersivity is the ratio of solute dispersion to flow velocity. As the saline water leached from the spoils enters the aquifer, a "plume" of solute spreads through the aquifer in the direction of ground water flow. As the plume moves through the aquifer, the dissolved solids aze diluted, diffused, and absorbed by physical and chemical interaction with the natural ground water. The greatest effect on dispersion in aquifers associated with coal strata is the heterogeneous nature of the formation. The lithology of the Williams Fork Formation is variable, displaying many fades changes, pinch-outs, and thin sandstone lenses. Ground water movement in such an aquifer is non-laminar, thus absorption and diffusion of highly saline water is enhanced. Longitudinal dispersivity is measured in the direction of ground water flow; transverse dispersivity is measured in a lateral direction. The measurements, calculations and assumptions discussed above were used in a predictive analysis to model the distribution of a plume of saline water emanating from the Energy Mine No. 1 into the Twentymile Pazk ground water basin. The OSM Plume Management Model (1981) was used to estimate concentrations of total dissolved solids (TDS) in milligrams per liter above baseline concentration after 50 years of solute intrusion. The results in Figure 11, Predictive Analysis -TDS Concentrations after 50 Yeazs, show concentrations to be diluted to acceptable levels of TDS concentration. The disturbed area is tributary to Sedimentation Pond D, as shown on Map 24, Surface Facilities. Pond D serves as the treatment facility for dischazge point 005 (Site 84) under NPDES Permit CO-0027154. A system of diversion ditches delivers water to Pond D from the underground and surface mining operations. As stated previously, the Area 1 Pit receives water from surface runoff and infiltration from upgradient reclaimed spoils. In addition, backfilling operations necessary for reclamation and waste rock disposal displace water in the pit, causing an overflow at the final highwall. The overflow has been directed into Pond D through a designed channel. Sufficient freeboard has been provided to handle rates of flow higher than the design flow of 0.8 cfs. The drainage from the Area 1 Pit will be treated in Pond D to meet the effluent ]imitations applicable under the NPDES Permit issued to CYCC, before being released to Foidel Creek. The overflow channel has been constructed at the lowest topographic point on the highwall, and conforms to the requirements for temporary diversions set forth in Rule 4.05.3. Designs for the overflow channel are given in Table 51, Overflow Channel Specifications. TROS-49 2.05-94 Revised -May 2005