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Groundwater Monitoring <br /> Monitoring Sites <br /> A total of nine groundwater monitoring sites are proposed for the Howardsville Mill. <br /> Two sites are located upgradient of the prevailing groundwater flow regime, three are <br /> located within the new tailings pond, two are located immediately downgradient of the <br /> new tailings pond, one is located in the old tailings, and one is located below both the <br /> old tailings and the new tailings. With this placement, information on the character of <br /> upgradient groundwater, water within the new tailings, and impacts to areas outside the <br /> new and old tailings will be collected. <br /> In order to characterize the "baseline" groundwater inflows, two groundwater <br /> monitoring sites (wells 13 and 17) are proposed. Well 13 is located adjacent to the <br /> Animas River, upgradient of groundwater flow from the new tailings. This site is also <br /> the location of high sulfate, zinc, TDS, and low pH readings from the monitoring done <br /> in 1985 and 1986. It is important to determine whether these values are connected to <br /> the new tailings or are related to upgradient conditions. The second upgradient well <br /> (well 17) is located immediately outside (east) the new tailings pond. This site should <br /> identify conditions immediately upgradient of the new tailings, and also indicate any <br /> hydrologic connection between the new tailings (at a higher topographic level) and the <br /> groundwater outside the new tailings pond. <br /> Three groundwater monitoring wells will be monitored within the new tailings pond <br /> (well 1, 3, and a new well to be constructed in the SE comer of the new tailings pond). <br /> The combination of these three wells will provide information on the chemical <br /> character of the subsurface water within the new tailings pond. This information can <br /> then be correlated to information provided by wells immediately adjacent but outside <br /> the new tailings pond. <br /> Two groundwater monitoring sites which will reveal groundwater movement or <br /> contributions attributable to the adjacent tailings will be located north and west of the <br /> new tailings pond (well 15 and a new well). These wells will monitor groundwater in <br /> close proximity to the new tailings and will provide information on contributions to <br /> groundwater from the new tailings pond. <br /> One groundwater monitoring well adjacent to and downgradient from the old tailings <br /> will be monitored (well 9). This well will characterize the groundwater in the vicinity <br /> of the old tailings. With the removal of the old tailings proposed for 1997, it will be <br /> important to obtain information from this well prior to, during, and after removal of <br /> the old tailings to document changes to groundwater quality. <br /> One downgradient groundwater monitoring site is proposed adjacent to the Animas <br /> River (well 10). This site will monitor downgradient water characteristics, and will <br /> allow comparison with the stations within and above the tailings. <br /> -3- <br />