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5.3.3 Upgradient water quality <br />The low pH measured in well GW -N38 prior to mining is to be expected, considering that <br />overburden here is very shallow and the sampling of the overburden in this area showed low pH <br />values. See the hydrologic cross section on Map R -2. This low pH was most likely due to the <br />higher amount of pyrite in the strata immediately above the coal seam, which is where the ground <br />water level was in 1993 and 1994. The increase in pH in GW -N38 from pre -mine to post -mine is <br />likely due to the increased amount of water in the well when the sample was taken, as the water <br />sample was no longer being taken at a point in the strata with the highest pyrite concentration. <br />Table 6 shows that the water levels in the shallow well changed from 11 feet below the surface in <br />1993 to only 4.9 feet from the surface in 2008. <br />Table 7 shows the full parameter list for GW -N38 in the pre -mine condition of 1993. It is low in <br />pH but also low in TDS. An examination of the ions in Table 7 shows that this water is basically <br />a mild sulfuric acid water with very low iron dissolved. Sulfate accounts for 248 of the 348 <br />mg /liter dissolved solids. We believe that this is due to the shallow level of the water, which has <br />more dissolved oxygen, which allows the iron to precipitate out as oxides, explaining why iron is <br />so low in the lower pH water. This water in GW -N38 has attained neutral pH in the post -mine but <br />yet has seen a great increase in TDS. This is explained by the fact that, as the water level in the <br />well increased, more calcite was available to neutralize the mild acid. An examination of the full <br />parameter list in Table 8, shows that GW -N38 well has considerably more bicarbonate and <br />calcium, showing that the calcite has reacted with the mild acid and produced more TDS. Sulfate <br />is also higher showing that the precipitation of calcium sulfate as gypsum is not occurring to a <br />large extent. It is important to note that this well is entirely upgradient from the mine spoil and all <br />of these chemistry changes are solely the result of the water level changes in the well. Other wells <br />in the area that measure pre -mine overburden quality show relatively neutral pH's but TDS in the <br />ranges of 3000 to 4000 mg /liter are not uncommon. This is true of Well GW -N45, located <br />immediately west of the mine. <br />The data for the upgradient coal well, GW -N37, shows similar data to that of the overburden. <br />SL -14 03DEC12.wpd 67 <br />