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, .f Page 14 -~ In addhkxt, the Impact of cyanide recovery on'the anticipated chemistry of the fallings seepage was Investigated through a series of laboratory decay experiments conducted by Stuart Miller and Associates, located In Sydney, Australia (10).. The expected chemistry of the Tapings liquor and seepage whh and without cyanide recovery is presented fn Table 11. The results of cyanide,decay and metals attenuation In entrained taiings liquor are presented In Tale 12. By reducing WAD cyanlde'In the tailings liquor, the Iree metals loaned quickly preclpltated Into the taiings mass. As a result, the poteMlal for elevated cyanide and metals levels In the seepage was signNlcantly reduced. The Improvement in seepage chemistry reduced long-term treatment requirements after mine closure and monftoring requirements, as well as other envlrorimental IlabllRles. Figure 8 presents the anticipated cyanide decay curves for the decant water and ent2lned fallings liquor at the Gdden Cross Mlne. By lowering the WAD cyanide levels entering the Impoundment, very low levels of residual metals and cyanide will result, minimizing the Impacts on wildlife and groundwater, while - significantly reducing downstream treatment requirements. The expected WAD cyanide levels will 6e more ~ . than an order of magnitude less than typical values found in decant and pore waters. TABLE 11 EJ(PECTED CHEMISTRY OF TAILINGS LIOUOR AND SEEPAGE A7 THE GOLDEN CROSS MINE i-; _. i.. -,. Tailing s Liauos Tailings Seeoaae Without Cyanide With Cyanide Without Cyanide With Cyanide Parametef'! Recovery Recovery Recovery Recovcr~ pH 10-11 9.5.10 9.5-70 B.0-9.i Hardness (CaCO) - 750 2000 - 2l>Ott Alkalinity (CaCO,; 1000 200 300-500 - Sodium 400 400 300400 30000 Calcium 200.300 800 300-000 800 Sulfate 1000 2500 1000-2000 2500 Total CN 150.220 25.30 50 25-3C WAD CN 150-220 5-10 20-30 <1.(I Cadmium <t.0 0.1 <0.005 <0.01 Chromium - - <0.02 <0.02 0.002-0,02 <0.02 . _ Cobalt 0.1 0.3 0.1-0.5 0.25 Copper --- - ~- 5.0-10.0 _ <0.5-1.0 Iron . - _ .:... - _ .. 7.0-5.0 -_... 5-10 :_:-_ _ . ..: 5 _ 8-10 Lead 0.001-0.1 <0.1 <0.001 ~~ ~ <0.1 Mangansese 0.05-0.1 <0.02 0.03-0.OS <0.1 Mercury 0.001-0.009 <0.0005 0.001-0.005 <0.00~)1 Nickel 0.01 0.05 -- - Selenlum 0.01-0.4 0.1 <0.05 -- Zinc 0.5-0.0 0.01-0.1 2.04.0 0.1 SCN 30-40 3040 --- -- "t All values In mg/I, unless otherwise stated.