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3.2 TDS <br />TDS is the measurement of the total dissolved minerals in water. It typically correlates <br />well with constituents which make up the majority of the dissolved solids and therefore, is a good <br />indicator of trends for these constituents. Conductivity is typically a good indicator of the TDS and <br />in turn a good indicator of some major constituents. The first series of pages in Table B-1 of <br />Appendix B presents the TDS, conductivity, and sum of major constituents (DSSUM) for each well <br />along with several other parameters. DSSLJM was calculated by adding the concentrations of major <br />cations and the major anions, except for one-half of the bicarbonate which is not added because this <br />concentration is evaporated during the measurement of TDS. This allows a comparison of TDS and <br />DSSLTM, which is a good check on the TDS and major constituent measurements. The first series <br />of parameters presented in Table B-1 also includes values of the charge balance (BALNC) of the <br />• major constituents. BALNC is calculated as the difference of cations to anions in meq/1 divided by <br />their sum times 100. BALNC is also a good indicator of accuracy of major constituents and values <br />between -10 and 10 are considered good. The TDS concentrations from the Trapper Mine ground- <br />water quality generally compazed favorably to the corresponding conductivity values. <br />3.3 pH <br />Field pH is an important parameter to monitor because some coal spoils have the potential <br />to increase acidity of the ground water which increases the mobility of most heavy metals. A pH <br />of less than 5 would generally be needed to greatly increase the mobility of most heavy metals. <br />Available pH data is tabulated in Table B-1 of Appendix B. Field pH has varied from 6.9 <br />to 7.3 in 1994 for water from well GA1. These variations aze well within the natural range of <br />• fluctuation. <br />3-7 <br />