MT MORGAN OPEN CUT PIT WATER QUALITY MODELLING stage 2 ● 19
4. RESULTS
4.1 RESULTS OF GEOCHEMICAL MODELING Geochemical modelling was conducted to assess the impact on OCP water quality following the addition of new tailings slurry. Results are presented in Table 4-1 to 4-6, covering mixing scenarios using new tailings at pH values of 7, 8, 9.6, 10, 11, and 12, combined with tailings-to-OCP water volume ratios of 0.3, 0.61, 1.0, and 2.0. Scenario 2 in Table 4-1 corresponds to Heritage Minerals’ proposed operating conditions: a new tailings pH of 9.6, EC of (up to) 4,000 µS/cm and sulfate (up to) 2,000 mg/L at a volume ratio of 0.61:1 (tailings to OCP water). This equates to approximately 2 MT of tailings processed per annum. Model predictions indicate a slight increase in pH across all scenarios following the addition of new tailings to OCP water. Concentrations of other parameters generally decreased, suggesting that the release of metals or other elements from the new tailings into the OCP water is unlikely. Figures 4-1 and 4-2 illustrate the predicted pH responses under varying pH and mixing ratios. OCP water pH remains relatively stable until the new tailings exceed pH 10, with a notable increase predicted beyond pH 11 (Figure 4-1). Additionally, OCP water pH rises incrementally with increasing tailings-to- water ratios (Figure 4-2).
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