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1 <br />,,•.- i ~ <br />_z . <br />;~ <br />3) The neutralizing capability of the mining area in contact <br />with the ARD is less than assumed. The diatreme is not <br />uniform down to the level of the Carlton Tunnel; the <br />unmineralized part of the diatreme considered to have acid - <br />neutralizing capability is only a layer of the diatreme and <br />comprises a greater percentage of rock at the surface than it <br />does at depth. <br />4) The HCI models do not predict the Zn (or other metals) <br />content of the discharge due to insufficent data. <br />As a result of the above, the Division considers that HCI has, thru <br />their calculations and modeling, failed to adequately support their <br />conclusion that there is no potential for a significant impact of <br />the mine on the Carlton Tunnel discharge. <br />The Division understands that CC&V intends, at this time, neither <br />to cover the Ironclad dump nor to introduce neutralizing agents <br />into the material to reduce the acid-generating potential. As <br />stated to you during the meeting on April 4, 1997, however, the <br />Division believes that the change made in the value used by the <br />mine to separate "high" sulfide rock from low for disposal <br />purposes, ie. from 1.8 °s to O.So sulfide, did not eliminate *_he <br />requirement for the use of neutralizing agents in the high sulfide <br />disposal site. Apparently that was not the mine's understanding <br />since neutralizing materials have not been employed during the <br />disposal. In the absence of such materials, there are few <br />alternatives remaining to relieve the Division's clear concern <br />regarding the potential impacts of ARD from the mine. If, however, <br />an agreement could be reached with CC&V to appropriately cover the <br />Ironclad dump and to bond for that cover and interim water <br />treatment until the cover was installed, the Division would be <br />satisfied that some acceptable effort had been made by CC&V to <br />address this issue. <br />If you have any questions on the above, please contact me. <br />Sincerely, 7 <br />l,~ .. <br />~J ~-~~- - <br />H. Bruce Humphries <br />Supervisor, Minerals Program <br />97NO30 <br />