1992-06-10_REVISION - M1988112 (3)

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~ihJCILC15IES IN[, L ~ J I~J-?~2-~~JJ ~ i ~ll~ ~ TE 1Y~ UUL 1 reasonable approach might be to be sure the correct tests are pertjnrmed to show peroxide WILL meet the 4 ppm cyanide apeclfication with AL pond waters and solids and WITH L"Y"1'OX reagents added sImultaneousiy under a variety otconditions. With this data in hand, the confidence level w111 rise slgniQcantly. o Quantitation of the effectiveness of peroxide In getting to 4 ppm cyanide levels in the ponds cannot rely on the color of the pond waters and a regular suite of rnpper and total cyanide analyses are necessary As pointed out by your staff, these analyses need to Include enough sarhp)cs to be sure pond heterogeneity is accounted tor. In all of the discussion and guesswork surrounding the quality of cy nide analyses to date and the problems with sampling and analysis to this toxic, there seems to be a tendency to move toward dealing only with AD cyanides or to lump target cyanide levels into a RANGE ot, Por exam le, 4 to 40 ppm. In this regard, I would hope and expect that the original target of 4 fpm or less of total cyanide in the tailings pond will remain the Issue hvith respect to permit compliance. o It the peroxide process la as effective as put forth by BMG, then one might reasonably ask why trie INCO process is still expected to be used as }{et a third option to get rld of cyanides. o The issues of cyanide analysis, control, and permitted levels are cerla~nly the main ones addressed in the proposed technical revision, but the presence of copper in the tailings waters is also of concern from a toxi~ity standpoint and, to date, I have not seen any discussion of rlslcs from his metal. As the various cyanide control approaches are considered, the questlAns of Impact of these on copper levels end potential Por near term or fYrt(rre leaching otcopper into the surface or ground waters need to be addressed. The initial permitting data did not address copper since it was tkot anttclpated in the ore profiles but Its presence (In slgniflc~nt concentrations) is now verified and thus its control deserves attention. I appreciate the timely manner in which you and others in your office have transmitted information and replies in this matter to my attention and I shall look forward to skeing you again at the upcoming public hearings on the San Luis project. Sincerely, _~~ ~,~-- David E. Hyatt, Ph.D. Jun 09 92 LA60992DEH1