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' /anus ry /999 Ken Coal Compune * 1998Annua! Hydro(o,¢v Report ' CO Permit /\`o. G80~006 ~ PaQe <br />3.0 MINE AREA CONFINED GROUNDWATER <br />' Confined groundwater occurs in two mater-bearing zones at the mine site: Mine Area Coal <br />Aquifer and Mine Area Overburden. The Mine Area Coal Aquifer is monitored ac well 79-61. <br />t This well is located just north of the historic Pit 1, along Bush Draw, in the undisturbed coal <br />seam. The Mine Area Overburden wells are designated 79-1 and 79-2. These wells are located at <br />the north and south ends of the historic 720 Pit, adjacent to what was historically the east crest <br />' of the pit. See Map 1, Mine Area Monitoring Stations, for general locations. <br />Groundwater levels were measured and samples taken from these wells during October 1997 <br />' and April 1998, as designated in the Monitoring Plan. The field data Erom the Confined <br />Groundwater Wells are contained in Appendix A, 1998 Field Data. The individual analyses of <br />samples collected are presented in Appendix B, 1998 Coal Aquifer Water Quality Analyses and <br />t Appendix C, 1998 Overburden Water Quality Analyses. The water quality data are <br />summarized on Table 1, 1998 Groundwater Quality Statistics. Figure 1, Mine Area Aquifer <br />Water Level, shows the relative groundwater levels for the coal and overburden aquifers over <br />the past five years. The sample analysis results from the Confined Groundwater wells collected <br />under recommended revised sampling methods starting in April 1996 may be inconsistent with <br />previous results. <br />' 3.1 MINE AREA COAL AQUIFER <br /> <br /> <br />1 <br />1 <br />lJ <br /> <br /> <br />1 <br /> <br />1 <br /> <br />The mine area coal aquifer well (79-61) was monitored and sampled in October 1997 and April <br />1998. Table 1, 1998 Groundwater Quality Statistics, presents the water quality summary for <br />these sampling events. In general, the coal aquifer, remains lower in total dissolved solids <br />(TDS) than the overburden aquifer, suggesting little interaction between the aquifer systems. <br />For historical comparison purposes, the mean field and laboratory parameter values for Well <br />79-61 over the last five years are presented in Table 2, Historic Mine Area Coal Aquifer Water <br />Quality Data. <br />Figure 2, EC vs. TDS-Well 79-61, presents a comparison of electrical conductance (EC) to TDS <br />concentrations over the last five years. The values plotted represent actual levels measured <br />rather than a mean value. <br />3.2 MINE AREA OVERBURDEN <br />Table 1, 1998 Groundwater Qualicy Statistics, also includes a summary of the field and lab <br />results for the water year from wells 79-1 and 79-2. <br />For historical comparison purposes, the mean field and laboratory parameter values for the last <br />five years are presented in Tables 3 and 4, Historic Mine Area Overburden Water Quality <br />Data. Figure 3, EC vs. TDS-Well 79-1, and Figure 4, EC vs. TDS-Well 79-2, show comparisons <br />and trends over the past five years. <br />Morstgomery Watsan * P.O. Box 774018 * Steamboat Springs, Colorado 80477 "(970J 879-6160 <br />'Y' ~Mf lUnnW flyu.~ 11YYn11YY~ HylrNgr Rryvn <br />1/1//YY ~I~ <br />