A Cost Benefit Analysis (CBA) to Assess AMD Treatment Options

When a steelmaking coal mining operations commenced at the site, the inadequate expertise concerning acid and metalliferous drainage (AMD) management in the mining industry led to the operation’s placement of AMD-generating materials into historic mined rock stockpiles (MRSs) without consideration for their strategic use in AMD management during construction. With time, the site identified potential AMD issues that required immediate and long-term management.

Okane was involved in the design of active and passive treatment systems to treat AMD discharges at the site. The active treatment system incorporated an ultra-fine (<100 µm) limestone dosing system capable of treating flow rates of 400-500 l/s with annual acidity loads of 12,000 t/year. The passive treatment system used mussel shells to neutralize AMD discharge. The 300 t mussel shell bioreactor was the first such system built in the world and is designed to treat an acidity load of approximately 16 t of CaCO₃ per year at seepage flow rates of up to 6 l/s over a ten-year operational life. The decisions to implement active and passive treatment systems were supported by a cost-benefit analysis (CBA) and net present value (NPV) calculations based on limestone acidity neutralization efficiency.

The Okane led CBA and NPV calculations for assessed AMD treatment options provided the client with the financial information required to implement the best AMD treatment options for the site.