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Memo to the BMRI File Long-Term Tailings DETOX page 2 Detoxification of Active Tailings The Division issued an NOPV on March 31, 1992, which was later upheld by the Board on April 23, 1992. On May 28, 1992 the Board issued an Order to BMRI, containing a list of 12 abatement requirements. Item (4) of the abatement requirements directed BMRI to detoxify the tailings within the ponds. In response to this order BMRI has implemented several tailings treatment processes, including CYTOX and Hydrogen Peroxide (H2O2). As a result, the cyanide content within the pooled liquids and the solid tailings dep sited since July, 1992 has been significantly reduced. Interim standards or cyanide level within the ponds has been imposed by Order of the Boar on June 24th and July 22nd, 1992. BMRI proposed, and the Division approved, the implementation of the INCO (S02/Air) tailings treatment process, as long-term remedy to the active tailings cyanide problem. Detoxification of pre-July, 1992 Tailings Item (8) of the May 28, 1992 abatement requirements required BMRI to analyze the implication of having exceeded the tailings cyanide levels for t e long-term characterization of the tailings embankment. BMRI is dire ted to analyze the implications and to revise its reclamation plan, as appr priate. BMRI is required to complete the investigation, to submit a comprehe sive report, and to complete any appropriate permit modifications, within 180 days following detoxification of the active tailings. Comments have been received by the Board and the Division regarding ~he Division's rationale in the development of abatement requirement Ite (8). Commentors have questioned whether the older tailings will ever be detoxified. They have also questioned whether the presence of these tailings represents an imminent hazard. Further, they have questioned the ti e frame placed upon BMRI's performance. Finally, they have suggested that t e tailings should be actively manipulated to enhance or accelerate detoxification. The remainder of this memorandum summarizes the Division's rationale in developing abatement requirement Item (8>, and provides responses to each of these inquiries. (1) Will the pre-July, 1992 tailings ever be tleto~ified? The tailings exit the ore processing plant spigot into the tail nqs ponds as a slurry, comprised of solids and liquids. The solids remai ing after the cyanide leaching process are inert to further solution. Th y are largely silica, with a minor assemblage of species insoluble inIcyanide or species precipitated by the detoxification process, which arQ stable within the environment of the tailings. The constituency of th s minor assemblage has not been modified significantly by the recent teQhnical