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1 January ?000 Kerr Coa[ Companv " 7999 Annaa! Hvdro[o¢v Report ' CO Pernnt IVo. G80 C06 ~ Pa¢e J <br />3.0 MINE AREA CONFINED GROUNDWATER <br />Confined groundwater occurs in two water-bearing zones at the mine site: mine area coal <br />aquifer and mine area overburden. The mine area coal aquifer is monitored at well 79-61. This <br />' well is located just north of the historic Pit 1, along Bush Draw, in the undisturbed coal seam. <br />The mine area overburden wells are designated 79-1 and 79-2. These wells are located at the <br />north and south ends of the historic 720 Pit, adjacent to what was historically the east crest of <br />' the pic. See Map 1, Mine Area Monitoring Sca[ions, for general locations. <br />Groundwater levels were measured and analytical samples taken from these wells by Miller <br />' Water Monitor Sen~ice in October 1998, as designated in the Monitoring Plan. In May 1999, <br />momtormg consisted of water level measurements only, m accordance with the momtonng <br />reductions approved by the DMG. The field data Eor the confined ground water wells are <br />contained in Appendix A, 1999 Field Data. The individual analyses of samples collected are <br />presented in Appendix B, 1999 Coal Aquifer Water Qualicy Analyses and Appendix C, 1999 <br />Overburden Water Quality Analyses. The water quality data are shown on Table 1, 1999 <br />' Groundwater Quality Statistics. Figure 1, Mine Area Aquifer Water Level, shows the relative <br />groundwater levels for the coal and overburden aquifers over the past five years. <br />1 3.1 MINE AREA COAL AQUIFER <br />The final sample from the mine area coal aquifer well (79-61) was taken in October 1998. Table <br />' 1, 1999 Groundwater Quality Statistics, presents the water quality results for this sampling <br />event. For historical comparison purposes, the mean field and laboratory parameter values for <br />well 79-61 for each of the last five years are presented in Table 2, Historic Mine Area Coal <br />' Aquifer Water Quality Data. Figure 2, EC vs. TDS-Well 79-61, presents a comparison of <br />electrical conductance (EC) to TDS concentrations over the last Eive years. The values plotted <br />represent actual levels measured rather than mean values. Starting in April 1996, the samples <br />from the confined ground water wells were collected under recommended revised sampling <br />' methods, therefore, analysis results may be inconsistent with previous results. <br />3.2 MINE AREA COAL OVERBURDEN <br />' The final samples from the mine area overburden wells (79-1 and 79-2) were taken in October <br />1998. Table 1, 1999 Groundwater Qualicy Statistics, includes the field and lab data for this <br />' sampling event. In general, the coal aquifer remains lower in [oral dissolved solids (TDS) than <br />the overburden aquifer, suggesting little interaction between the aquifer systems. For historical <br />comparison purposes, the mean field and laboratory parameter values for each of the last five <br />' years are presented in Tables 3 and 4, Historic Mine Area Overburden Water Quality Data. <br />Figure 3, EC vs. TDS-Well 79-1, and Figure 4, EC vs. TDS-Well 79-2, show comparisons and <br />trends over the past five years. Starting in April 1996, the samples from the confined ground <br />' water wells were collected under recommended revised sampling methods, therefore, analysis <br />results may be inconsistent with previous results. <br /> <br />1 <br /> <br /> <br />Alontgomery Watson "P.O. Box 774018 "Steamboat Springs, Ca(orado 80477 "(970) 879-6260 <br />¢'\xV`Armwl fl~yu.tl Ifrrl prv {hYlr.Je~r R.9on <br />//dY:J~nJ <br />