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Longfellow Koehler Project <br /> Page 4 <br /> other structures intact including the buildings associated with the Longfellow Shaft. <br /> Mine Drainage Treatment Design <br /> Improvement in quality in the flows from the adits,natural seeps and the stormwater runoff <br /> poses a difficult problem due to the combination of low pH and high metals content. At this time it <br /> appears that the best solution is a passive bio treatment system. SGC will collect samples of waters <br /> from the underground sources to be treated. The water will be bench tested to provide data that will <br /> be used in the design of a passive bio treatment system to increase pH and reduce base metal <br /> concentrations. See attached paper on the passive bio treatment system. While SGC has agreed to <br /> complete this testing and project design, installation of an adit flow treatment project is not part of <br /> this Work Plan or SGC's agreement to do mitigation projects. <br /> Passive Bio Treatment Design Criteria <br /> Bench scale test results will provide design parameters for a passive treatment system that <br /> will utilize the space occupied by the current pond. The design will focus on establishing the longest <br /> practicable life for the installation. <br /> During the design stage SGC will collect additional background information monthly, <br /> when the site is accessible. Information collected will include flow, pH, temperature, dissolved <br /> metals,total sulfate and hardness. Dissolved metals will be limited to Zn, Fe, Al, Mn, Cd, and Cu. <br /> A field pH will be taken as well as flow measurements during sampling. These and any other results <br /> from parameters monitored for design of the system will be included in the design report given to <br /> WQCD. <br /> Part of the design will include a monitoring program that can be used to determine metals <br /> reduction. The following will be considered in the design of the passive bio treatment system: <br /> (1) Volume of water to be treated. High and low flow characteristics. <br /> (2) Water temperature, pH and hardness. <br /> (3) Metal loadings and precipitation characteristics. <br /> (4) Retention time for passive system to react and deposit metals. <br /> (5) Life of passive treatment cell. <br /> (6) A target removal of Seventy percent dissolved zinc reduction from the project site. <br />