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<br />concentrations) when used to project the quality of seepage expected from contact with the <br />Ironclad material. It was also agreed that there is mutual uncertainty as to what percentage <br />of a particular constituent that was rinsed out during the meteoric water mobility test <br />procedure would, in fact, leach due to contact with seepage under field conditions. As <br />another and perhaps more accurate estimate, it was agreed that we would assume that 25 <br />percent of the concentrations measured for the meteoric water mobility test could be found in <br />the seepage. <br />The fate and transport model we presented in the Application for Amendment Number 6 was <br />also based on extremely conservative assumptions regarding containment of the tailing and <br />the potential for contact with water. In order to employ a somewhat more realistic estimate <br />of the potential impacts to water quality, we have re-run the fate and transport model <br />assuming the following: <br />1. Ten percent of the geomembrane liner area is ineffective and, therefore, <br />Ironclad material may be contacted by underpad flows through that area; <br />2. The concentration of metals and other constituents in the pore water is equal to <br />25 percent of the concentrations measured in the meteoric water mobility test; <br />and <br />3. The Flow in Arequa Gulch is 7343 gpm and the water in contact with the <br />Ironclad material will mix with [his Flow. <br />The results of this re-assessment are shown in Table 1 (Attachment 1). The contributions of <br />the Ironclad Material, even under the very conservative assessments of dilution of all leakage <br />by only 14 gallons per minute, all become minute. The water quality, therefore, will be <br />dominated, and therefore dictated, by the existing water quality of Arequa Gulch. From <br />these results it should be concluded that there need be no concerns with respect to <br />exceedence of any of the water-quality parameters that have been used for comparison, even <br />if the additionally conservative drinking water parameters are assumed for ground water as <br />well as for Arequa Gulch. <br />Also, as we agreed, CC&V will, through Golder, proceed with another laboratory test <br />designed to estimate the quality of seepage after contact with the Ironclad Tailing Material. <br />This test will consist of compacting the Material in a six-inch mold, flooding the surface of <br />the specimen for 24 hours, and then collecting a water sample of the water for analyses. As <br />was agreed at last Thursday's meeting, the results of the test will be forwarded to your <br />Office for documentation. In the meantime, the Ironclad Material will be used as described <br />in the Office-approved Application and subsequent submissions. <br />2 <br />