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sulfate concentrations for the surficial alluvial aquifers in this area would be expected to be large and <br />the full range of historical natural values may have not been defined. <br />3.3 pH <br />Field pH is an important parameter to monitor because some coal spoils have the potential to <br />increase acidity of the ground water, which increases the mobility of most of the heavy metals. A <br />pH of less than 5 would generally be needed to greatly increase the mobility of heavy metals. <br />Available pH data is tabulated in Table B-1 of Appendix B. The field pH of water from the <br />GC wells has generally been slightly above 7.0 and has been at similar values since the initiation of <br />disturbance in this area. <br />Field pH from well GD -2 slightly decreased in 2005 and near neutral the last twelve years. <br />The upgradient mining in the QR seams has not significantly affected the pH in this area of the <br />aquifer. The pH values from backfill well GD -3 are near 6.7 for 2017, which is near the values in <br />the native aquifer at well GD -2. <br />Similar pH values were observed for the HI aquifer at well GF -4 in 2017 to those observed <br />in previous years. Backfill well GF -5 had field pH values above 7.0 in 2017, while the field pH for <br />backfill well GF -7 was near neutral. The field pH values in backfill well GF -11 for 2017 were also <br />near neutral and similar to previous years. The field pH in well GF -6 (QR) was also above neutral in <br />2017. <br />Well GP -2 (KLM) water was slightly above neutral in 2017. The field pH values for well <br />GP -3 were higher than neutral from the HI aquifer and from well GP -4 above neutral for the KLM <br />aquifer. <br />Well GP -5 is completed in the QR aquifer and its field pH values are generally above 8. <br />Trapper Mining Company 3-8 <br />2017 Annual Report <br />