Laserfiche WebLink
Monitoring records are listed in Table 50, Energy Mine No. I Pit Water Quality. This data is graphically <br />• represented in Figure 8, Leachate Concentration, Energy Mine No. 1. As shown, actual concentrations of TDS <br />Fluctuate, due to seasonal variations in snowmelt and precipitation. Average yearly concentrations of leachate are <br />shown below: <br />1'ear• # Samples Min. TDS Max. TDS Ave. TDS <br />1979 21 2080 3850 2948.1 <br />1980 37 700 3320 2626.8 <br />1981 22 456 2920 2608.5 <br />1982 17 324 3320 2863.1 <br />1983 24 520 4400 2757.9 <br />Lcachatc Tcstinp <br />In 1979, a study of leaching potential of overburden at the Energy No. I Mine was conducted. Column leach tests <br />were devised to simulate the dissolution of soluble minerals in the mine spoils over time. Concentration of TDS <br />was related [o electrical conductivity by linear regression. Concentration of leachate produced was related to time <br />by computing the travel velocity of water through [he spoils. The results of these experiments are shown in Figure <br />9, Predicted Leachate Concentration, Energy Mine No. I. The average concentration of TDS in the adjacent <br />overburden aquifer is approximately 650 mg/I. Note that [he predicted TDS concentration decreases rapidly to <br />approximate baseline conditions after 75 years. <br />• In 1983, similar column leach tests were performed on underground development waste to demonstrate that <br />ground wa[cr quality will not be degraded by leaching of waste rock. The test procedures and results are presented <br />in Exhibit 27, Column Leach Study of Mine Waste Material. The trend of leachate production from roof, Floor and <br />coal waste +vas very similar to that of mixed overburden spoil described above. At the conclusion of the column <br />leaching procedure, the leachate water was analyzed for constituents listed for ground water in "Guidelines for the <br />Collection of Baseline Water Quality and Overburden Geochemistry Data" (CMLRD 1982). <br />The analyses of leachate water, shown in Exhibit 27, Column Leach Study of Mine Waste Material, were <br />compared to existing pit water chemistry shown in Table 50, Energy Mine No. 1 Pit Water Quality. The average <br />concentrations of major cations and anions were converted to milli-equivalents per liter and plotted on a piper <br />diagram, shown in Figure 10, Leachate Chemistry, Energy Mine No. L In addition, the average concentrations of <br />major ions in ground water adjacent to the Energy Mine No. 1 pit were plotted. The piper diagram shows similar <br />water chemistry for leachate from underground mine waste and existing undisturbed overburden aquifer, although <br />the leachate water has much higher concentrations initially. These waters show asodium-sulfate dominance. <br />The water quality of the Mine 1 Pit shows acalcium-sulfate dominance which indicates a large proportion of <br />surface runoff. <br />Solute Transport <br />As stated previously, leachate water will percolate into the adjacent overburden aquifer under the inFluence of <br />potentiometric head. An analysis of solute transport through the aquifer was performed, using Flow equations to <br />• model a plume of saline water as it would be distributed in a confined aquifer with time. <br />The equations which describe [he [ravel of dissoh~ed solids through an aquifer are the same as those used in tracer <br />dye studies of porous media. The equations contain complex mathematical functions which can be solved b+ <br />P4R 97-lid 2.0~-95 Revised 9/9/97 <br />