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Review: "Ironclad Mill Tailings; Results of Cyanide Detox" Memo to B. Keffelew, June 27, 1994 Page 3 3. The MSDS for Ca-hypochlorite recommends evacuation within a 5000 foot radius if uncontrollable fire results. If Ca-hypochlorite is to be used on site, its handling, storage and emergency contingencies need to be incorporated by the Environmental Protection Plan. 4. Even though there seems to be less cyanide in the upper parts of the pile than deeper, and even though the plan is to remove material preferentially from the upper parts of the tailings pile, there appears to be no relationship between original cyanide concentration (in mg/kg) and the amount remaining after treatment (in mg/L). Thus, is it really useful to concentrate on the upper part of the pile? 5. WAD data for BGA-ICA-7, samples 5-10 and S-11 are not included. Why? 6. Well numbers BGA-ICA 1 through 5 were drilled prior to the Division's review of Amendment #6 and prior to the generation of the Commitments that resulted from the Divison's approval of the Amendment. Understandably, the data generated for that submittal do not meet many of the criteria needed for the present submittal. 'However, given the necessity of obtaining statistically significant information from wells BGA-ICA 6 and 7, which were drilled and tested specifically for the present submittal, there are several curious data gaps. In particular, many of the samples were not analyzed for cyanide under the MWMP testing program. It would be appropriate to explain why all of the samples were not analyzed for WAD and Total cyanide during the MWMP testing. 7. In section 5, page 12-I5, is a generous discussion demonstrating that cyanide concentrations are lower in the upper part of the tailings than the lower. The section pays a particular amount of attention to the cyanide concentrations in the tailings above 24 ft depth. In Section 6, it is stated that only the upper part of the Ironclad tailings will be put to use, and that the concentration of cyanide in the useable portion will be less than 2.0 mg/L WAD cyanide. The average depth of drill holes in the Ironclad tailings is about 80 feet, plus or minus a few feet; presumably, 80 ft is about the average thickness of the Ironclad tailings. The volume of Iron Clad tailings is about 576,000 yd3. The amount needed for liner material is 69 % of that, or 396,000 yd'. If 396,000 yd' of tailings is needed from a 576,000 yd', 80 ft thick, vertical-walled pile of tailings (i.e. 69%), then the pile would need to be excavated to a depth of 55 ft. Provided the pile has sloping sides, which it does, the depth of excavation would be deeper. Therefore, it is without merit to state that the concentration of cyanide in the useable portion of the tailings will be lower than 2 mg/L WAD cyanide.