9.1.5 Step 4: Predict mine drainage chemistry
Prediction of mine drainage chemistry is dependent on the acid-forming potential of the rocks, and is specific for different mine types. Based on the ABA results provided above, the proposed mine would be considered to fall into the potentially acid-forming category (Chapter 4). Mine drainage chemistry for the proposed mine can be predicted using Figure 11, which considers mine operations and hydrogeology (in particular the location of mine waste in relation to the water table). The proposed mine in this example is opencast, with the mine waste initially placed above the water table. The red line in Figure 37 shows the path followed to predict the generic water chemistry of mine drainage from the proposed mine.
Kinetic testing (Section 3.2.5) can provide more information on site-specific characteristics of mine drainage. For our hypothetical example, kinetic tests suggest that leachate from the mudstone will have the following characteristics: pH 3.2, Fe 15 mg/L, Al 32 mg/L, Acidity 249 mg/L, TSS 1000 mg/L.