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Letter to Ryan J. McHale 5 February 16, 2010 <br />Permit Application Adequacy Review File No. M-2009-076 <br />in an aquatic site; describe the analysis by Venture Resources to determine that such a permit is not required. <br />Provide a modified Exhibit F as necessary. <br />16. Waste stream characterization has been provided in Exhibit C, and from that characterization Venture <br />Resources concludes that the mill tailing will be inert with all acid forming minerals removed. The DRMS <br />has identified the following issues with the waste stream characterization: <br />a. The waste stream characterization indicates that high concentrations of lead, manganese, and zinc will be <br />dissolved and acidity generated in the process water during milling operations. The source for these <br />metals and the acid are likely acid salts present in the waste rock fed to the mill. Acid salts are readily <br />soluble and precipitate in waste rock dumps such as those in Hukiii Gulch as a result of wetting and <br />drying cycles. The metals concentrations and total dissolved solids in the process water will increase <br />cumulatively as the water is recycled and reused for milling as described in the permit application. <br />b. Venture Resources points to the relatively good quality of the SPLP leachate from the finished tailing as <br />proof that all toxic or acid forming materials had been removed by the milling process. What the SPLP <br />results demonstrate is that the majority of the readily soluble metals and acidity had been removed. It is <br />unlikely that all sulfide minerals and metals had been removed; in fact, the presence of relatively low <br />concentration of metal in the leachate demonstrates that metals remain. Moreover, it is likely that in <br />commercial production, opposed to the carefully scrutinized waste characterization test, recovery of <br />sulfide minerals and metals in the milling process will be less complete, partly because there are economic <br />disincentives to complete or one-hundred percent recovery. Therefore, once the tailing are impounded <br />and resume weathering, acidity and dissolution of metal will also resume. This might be at a lower rate <br />than in the historic waste piles due to the removal of the majority of the reactive minerals in the mill, but <br />the fine grain size of the tailing mitigates the improvement by increasing the surface area of minerals <br />exposed to weathering. The ongoing generation of acid would undoubtedly be demonstrated if the <br />representative final tailing were put to net acid generating tests, acid-base accountings, net acid producing <br />potential tests, humidity cell tests, etc. The DRMS has determined that such additional testing is <br />unnecessary based on the results of the testing Venture Resources has already done, the known and well <br />understood geochemistry and water quality of the district, and the history of tailing produced using the <br />milling and extraction methods proposed by Venture Resources. The tailing produced will not be inert, <br />and will generate a leachate high in dissolved solids. <br />17. The Environmental Protection Plan at section 6.4.20(7)(f) requires containment facilities shall be of <br />adequate size to provide sufficient reserve capacity to prevent release of toxic or acid forming materials. <br />Additional information required for the crusher feed pad was discussed in item 4 above. Information on the <br />isolation of the water holding pond from run-on is required in item l la. Additional fluid management <br />information for the tailing impoundment is required as follows. <br />a. Specify the volume for water storage to be provided in the impoundment at each stage and describe how the <br />deposition of tailing will be controlled to provide the specified volume. <br />b. Specify required minimum freeboard in the impoundment for each phase sufficient to accommodate inflows <br />from a 100-year storm and leave a safe reserve freeboard to prevent overtopping of the impoundment shell <br />and prevent the development of destabilizing pore pressures in the tailing mass. Analysis for development <br />of the freeboard specification must assume that pumping equipment will be unavailable for management of <br />inflows from the design storm.