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Marr Mine - 2007 Annual Hydrology Report May 2007 <br />3.0 MINE AREA GROUNDWATER (WATER TABLE) <br />Deep groundwater occurs under water-table conditions in two primary water-bearing zones in the <br />mine area; the Sudduth Coal Seam, and the undifferentiated overlying overburden materials. The <br />Sudduth Coal Seam is monitored' at well 79-61. This well is located just north of the historic Pit 1, <br />along Bush Draw in the undisturbed coal seam. The mine area overburden wells are designated <br />79-1, 79-2, and 79-3. These wells are located at the south, middle and north sections of the <br />historic 720 Pit, respectively, adjacent to what was formerly the east crest of the pit. Spoil <br />monitoring well SP-01 was installed in the north end of the 720 Pit area in 2001 and monitoring <br />was initiated in 2002. The general locations of the monitoring points are presented on Map 1, <br />Mine Area Monitoring Stations. <br />Historical groundwater monitoring data for the coal seam and overburden wells have shown that <br />the characteristics of the water-table groundwater system, in terms of quality and quantity, have <br />been consistent and stable, such that monitoring at these locations was deferred until the last two <br />years preceding final bond release (2005 and 2006 water years). Monitoring in 2007 was in <br />excess of the plan due to the delay in bond release request submittal. The water levels measured <br />in 2007 were consistent with the previous water levels (1995-2001, 2005 and 2006). In this water <br />year, the spoil well SP-01 was monitored on a "quarterly" basis beginning in October 2006 and <br />then for three quarters in 2007. Note that the water levels in the spoil fluctuate almost 50 feet <br />throughout each year monitored and appear to be declining slowly with time. The well is usually at <br />its highest level during the spring and lowest during the late fall. Figures 1 and 1A, Mine Area <br />Water Levels, shows the relative groundwater levels for the coal, overburden and spoil since 1996. <br />Note that spoil monitoring was initiated during the 2002 water year and that the overburden Wells <br />at the mine (79-1, 79-2 and 79-3) and the coal water quality well (79-61) were monitored in 2005 - <br />2007 ending the deferment period. Well 79-3 has only been monitored for water levels historically. <br />The other wells were last monitored in October 1998. <br />Kerr has reviewed the water quality data from the 2007 water year and few anomalous data were <br />noted. Carbonate in SP-01, 79-1 and 79-61 were generally elevated. Note that the decreasing <br />conductivity observed in the data in 2005 was due to malfunction of field equipment. It was <br />replaced this year and the data is more consistent with previous readings. The field recorded <br />measurements are contained on the field data logs in Appendix A. The analytical data is provided <br />in Appendix B, 2007 Mine Spoil and Bedrock Water Quality Analyses. Tables 1 through 5 present <br />the historic water quality data through water year 2007 for the monitoring wells. <br />Page 3 <br />6371/2007/2007 hydrology rpt