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The trend of high values on the 1986 map forms a "Y" shape: the short leg of the Y begins in the <br /> Upper Pond and trends Northwest toward the Animas River, and tl ke longer leg of the Y begins at <br /> the Animas near the Eastern boundary of the map then curves throw h the center of the map where <br /> it meets the short leg at Well 9. This Y-shaped trend appears on nearly all of the 1986 maps. <br /> On nearly all of the maps, well 9, which is in the old tailings and area, contains the most <br /> anomalous measurements. <br /> TDS. <br /> The trend of elevated TDS in 1985 is similar to the 1985 sulfate tre id. Together, this correlation <br /> probably marks a zone of elevated pyrite concentrations, or a zonf where the products of pyrite <br /> weathering are flowing or concentrating. <br /> The trends of elevated TDS in 1986 are also similar to the 1986 sulfa a trends. As with the sulfate, <br /> well 1B appears to have become a source of TDS in 1986. <br /> Well 14, on the Animas River, increased significantly in TDS in 1 86. This behavior apparently <br /> appeared independently of any other parameter. <br /> pH- <br /> The pH trends are parallel to the trends of other parameters, but are displaced. A trend of low pH <br /> values in 1985 formed by wells 9, 15 and 13 connects to well 2A and surface water station 23. The <br /> 1986 trend connects only wells 9, 15 and 13. <br /> The pH of both wells in the upper pond dropped in 1986. <br /> Zn. <br /> The highest Zn concentrations in 1985 lie in a zone defined by wel s 9, 6, 3A, 15, and 13. These <br /> generally follow the trends of elevated SO, and TDS. <br /> With the exception of wells in the upper pond, Zn concentrations di opped in 1986. However, the <br /> zone or trend of elevated concentrations is generally the same as in 1985. <br /> Surface water observations. <br /> The 1985-86 data do not provide enough information to be very defi nitive, so nothing more about <br /> them will be discussed. <br /> The 1995 surface water data indicate that in general, water quality diminishes from upstream to <br /> downstream of the mill site. Metals and acid evidently are discharg ng from the mill site. <br /> DISCUSSION <br /> The drop in pH in the upper pond wells in 1986, coupled with t ie increase in TDS, SO„ and <br /> metals, is consistent with the interpretation that the upper pond a ea became a source of sulfide <br /> 3 <br />