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COLORADO DEPARTMENT OF PUBalC HEALTHAND ENVIRONMENT, Water Quality Conhol Division <br />Rationale -Page 2, CO-OOZ7529 <br />3. Numeric Standards: The standards which have been assigned in accordance with the above classifications can <br />be found in the Classi~[cations and Numeric Standards for the San Juan River and Dolores River Basins, <br />Regulation No. 34 (S CCR 1002-34), which became effective December 30, 1998. <br />IV FACILITY DESCRIPTION <br />A. Industry Description <br />1. Type of Industry: The industry that created the discharge was ore mining (gold, silver, lead, copper, and zinc). <br />The mine shut down in ]991 and no active mining is currently occurring or planned. Reclamation work is in <br />the final stages. The American Tunnel is in the process of being plugged, with the intention of reducing and <br />ultimately eliminating flows. <br />2. Sources to the Treatment Plant.• The discharge being treated emanates from the portal of the American Tunnel, <br />which has historically been used to access extensive underground mine workings. The permittee has been <br />negotiating arrangements with the Colorado Division of Minerals and Geology (CDMG) related to the plugging <br />of this tunnel. The permittee and the Division entered into a consent decree in May 1996 that addressed the <br />discharges from she Sunnyside Mine complex. Under the consent decree, the permittee was to construct an <br />underground bulkhead at their property line 8000 feet from the surface to stop drainage from the Sunnyside <br />Mine through the American Tunnel. Until this bulkhead is constructed, flows entering the American Tunnel on <br />Gold King Mines Corporation property, downstream of the property line bulkhead, will continue to 6e treated. <br />A mandatary lime during which the permittee was also required to treat a portion of the flow of the receiving <br />stream, Cemem Creek, has elapsed (this treatment began in August 1996); however, the permittee has continued <br />to treat this flow. The permittee is currently working on obtaining approval from the CDMG for construction of <br />the bulkhead. <br />B. Wastewater Treatment Description <br />Outfall 004 is the sole discharge point from this facility. Sources included in outfall 004 are summarized in the [able <br />below: <br />Mine drainage pH adjustment, floc, sedimentation 1.1 1.2 <br />Cement Creek Flow pH adjustment, ,floc, sedimentation 0.7 1.4 <br />Groundwaterlnflow Mixed with treated water 0.03 0.07 <br />Reagent Mix Water Used for mixing with reagents 0.03 0.03 <br />Srormwater Inflow Mixed with treated water 0.06* 0.12** <br />* represents average annual precipitation for contributing area X runoff factor. <br />** represents 1.7" storm event for contributing area X runoff factor. <br />The treatment system consists of pH adjustment with quicklime, flocculent addition, and then settling to a series of <br />four unlined ponds with a combined volume of 2.101 MG. Plant capacity is estimated to be 3.0 MGD, primarily <br />limited by lime feed rate. <br />The chemicals used at the plant include quicklime, which is used for pH adjustment, and flocculant that is used to <br />aid settling. The latest information available to the Division indicates that the specific flocculent being used is Nalco <br />7877. This chemical is a polyacrylamide in a hydrocarbon solvent/water emulsion. Aquatic toxicity jest results <br />summarized on the MSDS for this chemical at 1 % solution indicate that it is slightly toxic to aquatic life. <br />