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weathering (thus, acid) in 1985. The upper pond area is also an obvious source of metals, <br /> particularly Zn. These constituents - metals, sulfate and acid - are evidently discharging to the <br /> Animas River, causing an already degraded waterway to grow more so. <br /> You recalled some second or third-hand speculation that Well 9 is a high metal (particularly zinc) <br /> source because it transects "old" tailings whose zinc concentrations are high because Zn was not <br /> recovered due to its low price when those tails were milled. However, the increase in Zn <br /> concentrations in the Upper Pond area in 1986 does not completely support this notion. The <br /> tailings in the Old Pond and the Upper Pond areas both appear to contain high amounts of Zn. <br /> I would suggest that the Zn content is high in these areas not because the Zn prices were low, but <br /> because the Zn grades were too low to justify separate zinc recovery circuits. If my speculation is <br /> correct, and if the ores in each of the areas have a generally similar mineralogy, then all of the <br /> tailings will be high in Zn, and will remain a source of Zn for the foreseeable future. <br /> The appearance of elevated metals, higher TDS and SO„ and lower pH in the upper pond wells in <br /> 1986 can be interpreted to be either a leak in the pond liners, or an inefficient and significantly leaky <br /> substrate. As we observed on our field tour of 10-31-95, the pond liners apparently do not cover <br /> the floor of the tailings, but cover only the perimeter berms. <br /> Currently, there is no doubt that the tailings are reacting with surface and groundwater, particularly <br /> the latter. This can be expected to continue indefinitely unless the tailings are protected from water <br /> infiltration, both from above and below. <br /> RECOMMENDATIONS <br /> Monitoring_ groundwater. <br /> A map showing proposed ground and surface water monitoring points is attached. The proposed <br /> monitor well locations should be adjusted as much as possible to take advantage of wells already in <br /> existence. These recommendations do not assume that any more tails will be deposited, and assume <br /> further that no significant earthmoving activities will take place during the monitoring period. If <br /> this is not the case, the wells should be adjusted to account for any future earth moving activities. <br /> For groundwater monitoring, based on the information at hand, I would recommend that at least <br /> 9 wells be made available for regular sampling. These should be placed more or less in a series of <br /> three wells each covering the property. The well placement should allow monitoring of several <br /> potentially interfering influences, and allow you to distinguish, generally, between contaminants <br /> deriving from pre-law tailings and permitted tails. <br /> I would recommend that monitoring be conducted, monthly, for the first year, in order to first <br /> identify the tailings contaminants, and second to characterize seasonal variations. After that, <br /> sampling frequency may be cut back perhaps to quarterly monitoring such that the most <br /> representative months are sampled, and the analyte list may be reduced to a minimum number of <br /> parameters that best characterize the source and movement of contaminants. <br /> 4 <br />