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Marc Mine - 2005 Annual Hydrology Report February 2006 <br />4.0 MINE AREA ALLUVIAL GROUNDWATER <br />Field measurements were taken at alluvial well AO-2A in October 2004 and on a monthly basis In <br />2005 from March through September. Field data are presented in Appendix A, 2605 Field Data <br />Water samples were collected and analyzed in October 2004 and in April and July of 2005 As of <br />January 1999, the parameter list for alluvial well sample analysis was reduced to include only <br />major elements and no trace metals. The individual analyses of samples collected are presented <br />in Appendix C. Table 1. 2005 GrDUrxlwater Ouality Statistics, includes a summary of the water <br />quality data for well AO-2A for the 2005 water year inGuding the minimum, maximum and mean <br />values. The mean annual values for field parameters and the laboratory results for the last 8 <br />morntoring years are presented in Table 7, Site AO-2A Historic Mine Area Alluvial Water Quality <br />Data. The water levels recorded for AO-2A over the last 8 years are shown on Figure 1, Mine <br />Area Water Levels. Figure 2. EC vs TDS-Well AO-2A and 2A, shows the relationship between <br />electrical conductance (EC) and total dissolved solids (TDS) levels since 1998. <br />Wells AO.2 and AO-2A are located in Bush Draw, downstream (east) of the northern extent of the <br />reclaimed Flit 1 area. In 1992, low water levels and the silted condition of well AO-2 resulted in <br />the inability to collect samples from this location. Well AO-2A was installed to a depth of 14 feet <br />in January 1993 and was located adjacent to well AO-2, replacing the original monitoring well. <br />See Map 1, Mine Area Monitoring Stations, for the general well location. The change in wells Is <br />apparent on the EC and TDS data. Well AO-2A has less dissolved constituents than the original <br />well. There was no obvious change in water quality in the 2005 water year. Note that the field <br />equipment utilized for measuring EC may have malfunctroned. Accurate measurements will be <br />made in 2006. <br />FIGURE 2 <br />EC vs TDS -WELLS AO-2 and 2A <br />p <br />498 497 490 49B 40U tOlOt 492 6A2 8/02 1N02 403 HA7 8N3 1093 401 8A4 8.04 1001 4A6 <br />GATE <br />• TDS • EC <br />63iV2[1(d %3UU3 hpImLry~mt Page 8 <br />