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EFCI Southfield Mine -Year 2005 Annual Hydrology Report May 11, 2006 dewatering well in 1994. In 2003, it was converted to a monitoring well and will be referred to as the well MW-NW. In Technical Revision 35 (TR-35), the groundwater monitoring schedule was reduced from quarterly to semi-annually and is conducted in June and December. Field measurements and laboratory data for active monitoring wells aze summarized in the following discussions. Raw field and laboratory data for the 2005 water year are provided in Appendices A and B respectively. Measured water levels for all Mine Area monitoring wells aze summarized in Table 4, Monitor Well Water Levels, for the yeazs 2000-2005. Table 4 Historical, in Appendix A, presents ground water levels from 1980-1999. The historic water level data aze presented graphically for the five monitoring wells (including historical information for Wells MW-8 and MW-10) on Figures 3, 4, 5, 6, and 7. Water levels for well MW-16 have shown some cyclic/seasonal fluctuations. It was dry from December 2001 until December 2003 (except for June 2003), possibly associated with drought conditions and has silted up to approximately 110 feet below ground surface. Water levels for 2005 were between 100 and 110 feet. Well MW-23 has demonstrated steadily declining water levels since July of 1984. Water levels for Well MW-65 have generally remained stable with minor fluctuations oft 10 feet. MW-NW has been dry since monitoring was initiated in early 2003. Water quality data for monitoring wells MW-1Q MW-16, MW-23, MW-65 and MW-NW aze provided on Tables 5, 6, 7, 8, and 8A, respectively. These tables provide any analytical results for 2005 and the minimum, maximum and average values calculated using al] historical monitoring data. Consistent with the historic monitoring schedule, water quality samples were not obtained for Well MW-8. Review of historic water quality monitoring data indicates spike values for several pazameters and minor to moderate variances in ground water quality over time. The most discernable patterns of changing ground water quality over time are listed below. • MW-10 -General water quality has been fairly consistent over time - Increasing trends for Ortho Phosphorous (until 1988) and for calcium - Decreasing trends for conductivity, total dissolved solids, sodium and bicarbonate; • MW-16 -Generally water quality in this well is erratic - Increasing trends for conductivity - Erratic data for sodium, sulfate, bicazbonate, calcium and chloride • MW-23 -Generally consistent water quality - Slight increasing trends for conductivity, total dissolved solids, bicarbonate and sodium • MW-65 -Generally very consistent water quality over time - Slight decreasing trends for sodium and bicarbonate The historical averages in each monitoring well were compared to the Colorado Groundwater Standazds provided in Regulation no. 41 -Basic Standazds for Ground Water. The historical averages exceeded a standazd only for the following parameters and wells. • Iron, dissolved - MW-16 and MW-23 exceeded the Secondary Drinking Water Standard but not the Agricultural standazd; fi417/2005 annual hyd rpt.doc NWCC INC. Page 8