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~ i <br />Sundance Coal/Animas Mine File - 3 - August 7, 1986 <br />Mine Inflow <br />The annual report of mine inflow data, as required by Stipulation No. 7 of the <br />Findings of Compliance document, was received and contained the following: <br />1. A map showing the location and nature of the mine inflows as well <br />as pump locations; <br />2. Monthly records of pump discharges from the various workings; and, <br />3. Quarterly determinations of the quality (field parameters) of the <br />. water being pumped from the various mines. <br />Missing were quality determinations for the Animas and Helen Mines for third <br />quarter 1985. <br />The quality of water pumped from the mines during the year did not <br />significantly differ from that reported in earlier years with the exception of <br />the October 1985 samples. The reported conductivities of samples from all <br />mines at this time were an order of magnitude lower than normal. An operator <br />error is suggested or possibly instrument malfunction. <br />The previously reported relationships of quantity of mine inflow to <br />precipitation was not apparent during 1985-86 with the possible exception of <br />the old mine. Pumpage from the Animas Mine was at its highest during some of <br />the drier months, i. e.: October through November. Pumpage from the Helen Mine <br />was relatively constant throughout the year. The reasons for this change are <br />obscure. Possibly now that the mines are inactive, pumping is more a function <br />of the work schedule of mine personnel than the quantity of accumulated water. <br />Summary and Recommendations <br />No significant long or short term effects of mining on the quality and <br />quantity of local ground water are apparent. The quality of surface water <br />discharged from the local sediment pond will be better maintained by the <br />reported installation of gabion dams behind existing silt fences in the <br />diversion ditches draining the disturbed areas. These fences did prove <br />vulnerable to wash out during periods of heavy rain during 198 86 and twice <br />let to discharges from the pond which temporarily exceeded NPDES limits for <br />settleable solids. <br />No problems exist as regards the hydrologic monitoring system, procedures, and <br />schedule in existence at this time. No changes are recommended. <br />JCS/ddt <br />0016E <br />