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Marr Mine - 2007 Annual Hydrology Report 4.0 MINE AREA ALLUVIAL GROUNDWATER May 2007 Field measurements of water quality parameters were taken at alluvial well AO-2A in October 2096 and on a monthly basis in 2007 from March through September. Field data are presented'' in Appendix A, 2007 Field Data. Water samples were collected and analyzed in October 2006 and in April and July of 2007. As of January 1999, the parameter list for alluvial well sample analysis was reduced to include only major elements and no trace metals. The individual analyses of samples collected are presented in Appendix C. Table 1, 2007 Groundwater Quality Statistics, includes a summary of the water quality data for well AO-2A for the 2007 water year including the minimum, maximum and mean values. The mean annual values for field parameters and the laboratory results for the last 10 monitoring years are presented in Table 7, Site AO-2A Historic Mine Area Alluvial Water Quality Data. The water levels recorded for AO-2A over the last 10 years are shown on Figure 1, Mine Area Water Levels. Figure 2, EC vs. TDS-Well AO-2A and 2A, shows the relationship between electrical conductance (EC) and total dissolved solids (TDS) levels since 1996. Note that the inaccurate EC readings in 2005 were not included on the figures. Wells AO-2 and AO-2A are located in Bush Draw, downstream (east) of the northern extent of the reclaimed Pit 1 area. In 1992, low water levels and the silted condition of well AO-2 resulted in the inability to collect samples from this location. Well AO-2A was installed to a depth of 14 feet' in January 1993 and was located adjacent to well AO-2, replacing the original monitoring well. See Map 1, Mine Area Monitoring Stations, for the general well location. The change in wells! is apparent on the EC and TDS data. Well AO-2A has less dissolved constituents than the original well. There was no obvious change in water quality in the 2007 water year. The calcium and sulfate concentrations the last few years are notably less than well AO-2A. Note that the field equipment utilized for measuring EC malfunctioned in 2005 and was replaced in 2006. TABLE 7 - SITE AO-2A HISTORIC MINE AREA ALLUVIAL WATER QUALITY DATA AO-2 AO-2A Anal to 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Temp °C 7.4 9.3 10.7 10.0 9.8 10.7 10.0 11.3 13.4 10.2 H su 7.6 7.6 7.6 7.4 7.6 7.7 7.6 7.7 7.8 7.8 EC mhos/cm 200C 871 1200 1300 1167 1063 633.3 333.3(-) 200(-) 648 862 TDS 817 1060 1233 1037 977 620.0 680.0 600 470 533 SAR in water 2.84 2.39 2.78 2.50 2.44 2.60 2.60 3.02 2.16 2.57 Calcium dissolved 91.9 127.3 137.0 116 108.2 64.7 74.5 59.7 52.1 60.2 Sodium dissolved 131 130 158 127 123 101.3 105.9 111.1 75.3 96.2 Magnesium dissolved 46.0 60.6 69.2 56.6 55.9 32.1 35.7. 28.7 24.7 29.3 Potassium dissolved 3.9 4.0 3.9 3.4 3.7 2.7 2.7 2.2 2.3 2.9 Sulfate 280 490 617 527 453 237 257 173.3 181.7 113.3 Chloride 11.7 16 18 14 13 9 11 3.7 5.3 3.7 Carbonate as CaC03 <2 5.3 <2 <2 <2 <2 <2 <2 <2 <2 Bicarbonate as CaC03 373 317 319 272 279 262 283 378.3 261.7 343.7 Fluoride 0.4 0.4 Nitrate-Nitrogen diss 0.28 0.14 0.18 0.10 0.09 0.06 0.04 0.58 0.12 0.12 Iron (dissolved) 1 0.12 0.10 0.07 0.20 0.24 0.33 0.27 0.17 0.30 0.18 Manganese (dissolved) 1 0.80 0.81 0.67 0.80 1.09 0.55 0.57 0.295 0.281 01.387 Note: All values represent water year mean concentrations in mg/I unless otherwise noted. * = Equipment malfunction 6371/2007/2007 hydrology rpt Page 9