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COLORADO DEPARTMENT OF TIC HEALTH AND ENVIRONMENT Wate ality Control Division <br />Rationale - Page 3, CO- 0027529 <br />IV. FACILITY DESCRIPTION <br />A. Industry Description <br />1. Type of Industry - The industry which has resulted in creation of the discharge is gold mining. No active mining <br />is currently occurring or planned. The American Tunnel is in the process of being plugged , with the intention of <br />reducing and 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 State related to the plugging of this tunnel, resulting in a consent decree. Until <br />the plugging is complete, the permittee will continue to treat any American Tunnel discharge. For an interim <br />period of time , the permittee may also be treating a portion of the flow of the receiving stream (Cement Creek or <br />its tributaries), which will be diverted into the treatment plant. <br />3. Chemicals Used - The chemicals used at the plant include quicklime, which is used for pH adjustment, and <br />flocculent that is used to aid settling. The latest information available to the Division indicates that the specific <br />flocculent being used is Nalco 7877. <br />B. Wastewater Treatment Description <br />The treatment system consists of pH adjustment with quicklime, flocculent addition, and then settling in a series offour <br />ponds. Pursuant to the authority ofArticle 9, Title 25, Regulations for the Certification of Water Treatment Plant and <br />Wastewater Treatment Plant Operators, this facility may require a certified operator. The Operator Certification <br />Board is within the Colorado Department of Public Health and Environment and should be contacted relative to <br />specific requirements. <br />V. PERFORMANCE HISTORY <br />A. Monitoring Data <br />1. Table V -I summarizes the effluent data reported on the monthly Discharge Monitoring Reports (DMR's) for <br />the American Tunnel facility from 11/93 to 10/95. <br />Table V -1 — Self - Monitoring Results <br /># Samples or <br />Reporting <br />Parnmutar Pnrinds <br />Reported Concentrations <br />Avg Min Max Std D SOth % 85th% <br />Previous <br />Permit <br />Limit <br />Flow, MGD 24 2.4 2.0 4.8 0.51 2.3 2.4 n.a. <br />pH, su 24 9.2 10.0 7.0 -10.0 <br />TSS, mg /1 24 10.6 5.0 19.0 3.3 11 14 20 <br />Cadmium, mg /1 24 0.0012 0.000 0.006 0.0019 0.000 0.003 0.050 <br />Copper, mg /1 24 0.010 0.000 0.038 0.010 0.008 0.015 0.150 <br />Lead, mg /1 24 0.010 0.000 0.134 0.030 0.002 0.005 0.300 <br />Zinc, mg /l 24 0.250 0.100 0.470 0.100 0.250 0.360 0.750 <br />WET, Chronic, % Effect <br />Ceriodaphnia 7 71.3 100 100 100 <br />Pimephnln.c 7 25 inn inn inn <br />