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Page 21-26. <br />The articulated comparisons between blast-hole NNP, humidity cell, and static test NNP <br />results are confusing and in cases are not accurately reflected in the accompanying diagrams. It <br />appeazs that the 38 humidity cell tests are interpreted to represent the AGP & ANP data provided <br />by the more than 100,000 samples from the currently mined azea, but as the average NNP's of <br />the two data sets differ, this presumption seems questionable. It is presumed for purposes of this <br />comment that blast hole test results would provide more representative information on C:S ratios <br />of the mined interval. The discussion in the top paragraph of page 25 does little to clarify the <br />explanations. <br />(a) The discussion on page 23 (3`d paragraph) refers mostly to Figures 4-2a and 4-2b and <br />indicates that, based on the final pH of the humidity cell tests, "the AGOSA can be expected to <br />generate circum-neutral leachates." The text indicates that the "average characteristics" would <br />indicate a neutral pH, even though only about I /3 of the samples have a pH greater than 5. <br />(b) The discussion on page 23 apparently projects the NNP for all of the waste rock, but the <br />figure does not distinguish between AGOSA waste rock and SGOSA waste rock. Evidently, <br />data in Figure 4-2a were meant to be repeated in 46, but about l5 of the sample results appear to <br />be missing from 4-26. <br />(a) Please clarify how it was concluded that the overbtu•den "catr be expected to getretate <br />circum-neutral leachates. " /jclarifications or correctiot:s of figures 4-2a and/or 4-26 <br />are necessarv to explain the cotrclusion, please include those. <br />(b) Please distinguish on figures 4-2a and 4-26 which samples represent ACOSA and which <br />represent SGOSA. Please indicate whether these are representative of the rock that will <br />be encowuered in future mining. <br />(c) Please explain the possible discrepancies between Figures 4-1a and 4-26 or submit <br />corrected figures. <br />Page 25-26; Figure 4-4; page 36-37. <br />The discussion about the relation between paste pH, NNP, depth, and sources of acidity is not <br />everywhere supported. <br />(a) Paste pH, which is dominantly a soil test, can provide information on hydrogen ion <br />activity that would result immediately by saturation of a previously unsaturated media. That a <br />paste pH measurement of unoxidized or slightly oxidized rock is an appropriate utility for <br />predictions oflong-term ARD potential is not unambiguous. <br />(b) The text indicates, last paragraph, page 25, that less than one third of the 578 samples <br />tested show signs of acidification from sulfide, and refers to figure 4-4, yet clear support for this <br />statement based on figure 4-4 is not apparent. (This discussion is re-visited on p 36-37.) The <br />figure depicts approximately 1 l3 samples, not 578 as stated. The figure shows that 70% of the <br />samples have a net negative NNP. <br />Please address the apparent disctepancies between fig:tre 4-4 acrd the text. <br />Please re-visit the presumptions about paste pH, lack of oxidatiot: at depth, evidence for lack <br />of acid production in the shallow sections, and the use of paste pH as a ptediclor of IVNP. <br />