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<br />Review: "Ironclad Mill Tailings; Results of Cyanide Detox" <br />Memo to B. Keffelew, June 27, 1994 <br />Page 2 <br /> <br />Cyanide analyses exceed water quality compliance criteria in the majority of the samples tested <br />and reported. Of the samples treated with 3 lbs calcium hypochlorite per ton of ore, 63 <br />exceeded the water quality criteria. Even though the report focuses on the upper 24 feet of the <br />tailings as being particularly low in cyanide, there is only one MWMP analysis of any sample <br />in the shallow levels. The following table shows the breakdown of the WAD cyanide analyses <br />by treatment scheme. <br />Sample type No. No. > 0.2 % Exceedine <br /> $DIS. me/L WAD CN Water Qual. <br /> Comte Crit. <br /> <br />Untreated 2 2 100 <br />Treated 1#/ton 0 - - <br />Treated 2#/ton 0 - - <br />Treated 3#/ton 8 5 63 <br />Treated 5#/ton 6 3 50 <br />Treated 10#lton 1 0 0 % <br />Untreated, 8 hr exposure 4 3 75 % <br />Overall, the report does not present enough information on the Iron Clad tailings, including the <br />information presented in the Amendment #6 submittals, with which to make informed <br />judgements regarding the potential for cyanide movement into the environment. <br />OBSERVATIONS <br />1. Although the text notes that the samples contain an average of 15 % moisture, it is not <br />possible from the data to determine whether there is a relationship between moisture <br />content and cyanide content, or between these parameters and other success criteria. <br />Only a few samples were tested for moisture content, and they are not representative of <br />the pile. <br />2. The text states that cyanide increases with depth. Moisture content data are scarce but <br />seem to indicate no relationships with depth. This relationship needs to be explained or <br />examined further. Moisture content in this case probably correlates with cyanide <br />concentration, but such needs to be shown. <br />