The Influence of Rainfall on the Characteristics of Historic Acid Mine

Drainage on the Denniston Plateau, NZ

Jewiss, C. S.1, Craw, D.1 & Pope, J.2

University of Otago1, CRL2

Denniston Plateau

Stream Flow Data

pH/Specific Conductance v Flow Rate

Specific conductance is the measure of the conductivity of the dissolved load, which can be correlated to the concentration sulphate and other ions in solution.

Precipitation and Neutralisation

Conclusions• Increased flow rate occurs during rainfall events, with a lag of

approximately one-two hours• Varied water chemistry occurs within the historic runoff at

Cascade Mine• pH and SPC have an overall dilution effect during rainfall, with

the exception of heavy rainfall events that propagate aflushing event, causing a sharp decrease in pH and increase inSPC

• Fe-oxyhydroxides ± schwertmannite + Al-mineral precipitatein mixing zones in Cascade Creek, consistent with geochemicalmodelling

• Partial acid load of Cascade Mine– Ca. 463 t CaCO3/yr

• Bathurst Resources Limited for providing access to Cascade Mine• WCRC for providing the pH/EC sonde• Education Endowment Trust, AusIMM NZ Branch – Postgraduate Scholarship• My field assistants, Hana Christensen and Aaron Dutton (CRL), Emma Scanlan, Jason Jewiss and Christine

McLachlan