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calculated 800-year duration is not meant to be a precise prediction of the duration <br />of elevated dissolved solids, but indicates the elevated solids can be expected to <br />last, possibly, several centuries. <br />The New Horizon Mine has two significant differences to the results observed at <br />Seneca II. First, the calcite present in the spoil at New Horizon seems to react with <br />acid produced by the oxidation of pyrite and take a substantial amount of sulfate <br />from solution into solid calcium sulfate. This keeps the dissolved solids content <br />somewhat constant no matter how high or low the inflow water quality is with <br />regard to TDS. Second, the Seneca II site is a dryland reclaimed area where the <br />only recharge into the spoil is a minor amount from precipitation and seepage from <br />the underburden aquifers. Total measured discharge from the spoil was only 3" per <br />year. The New Horizon Mine is principally irrigated with water of very good <br />quality over a large portion of the year. As descflueu IM UCI, this results in a total <br />movement through the spoil of approximately 16" per year. Since the amount of <br />water moving through the New Horizon spoil is so much greater, it should oxidize <br />the pyrite much more rapidly and also flush other salts which are contributing to <br />the increase in TDS at a much higher rate. For this reason, a ratio of the discharge <br />at both sites could be used to predict the time frame of slightly elevated spoil water <br />quality. This ratio, 3/16", as applied to 1500 years, results in a time frame of 280 <br />years until all the pyrite is oxidized. When considering all the variables involved, <br />this means that it could dissipate within a range of 100 to 500 years. The TDS <br />should begin to drop before this time. Once the pyrite is fully oxidized and other <br />salts are flushed out, the spoil water quality should approach the irrigation water <br />quality, possibly dropping to 300 ppm TDS. <br />Impacts To Receiving Waters <br />Since these spoil springs were never present in the pre-mine landscape, their <br />impact to the quality of the receiving waters must be addressed. The sample point <br />Spoil Spring 'I represents the spoil water discharge from the New Horizon #1 Mine <br />and has been monitored since 1987. Spoil Spring I discharges into Tuttle Draw a <br />short distance downstream. Tuttle Draw enters the San Miguel River <br />approximately 2 miles to the southwest. <br />Sample site SW-N1 is located in Tuttle Draw immediately upstream of any <br />influence from the mine. Sample data over the past 12 years from sites SW-N1 and <br />Spoil Spring 1 have shown that the TDS of the waters drops significantly when <br />irrigation is active in the area. Therefore, the impacts to the receiving waters will <br />be studied for both cases, with and without irrigation. The irrigation case <br />corresponds to the September/October time period when flows are fairly low in the <br />San Miguel ;River. The non-irrigation period corresponds to March/April when <br />flows in the San Miguel are usually at peak. <br />The spoil water inflows from both mine areas influence the quality of Tuttle Draw <br />to a minor degree. However, as these flows enter the San Miguel River (where the <br />35