CRC ORE have developed a range of tests to predetermine the probability and extent of Acid Rock Drainage on a mine site. Failure to accurately predict acid rock drainage (ARD) leads to substantial financial consequences and reputational damage to operators.
Predicting the impact of acid metalliferous/mine drainage and metal leaching potential of waste rocks and ore to the local and wider environment is critical for all mining operations. Acid rock drainage represents a substantial liability for both industry and government.
There is currently a range of chemical static and kinetic tests used to evaluate the acid producing nature of materials, from which risk assessments are prepared and waste classification schemes designed. However, these well-established tests and practices have inherent limitations including:
- Best-practice sampling is not pursued
- Risk assessments rely on limited static and kinetic test data, thus compromising the accuracy of resulting ARD block models
- Static tests are completed off-site and do not reflect actual field measurements
- Kinetic test data do not become available until later stages of mine development
- Waste classification schemes generally categorise materials as only three types (i.e., PAF, NAF and UC) with other drainage forms (e.g., neutral metalliferous or saline) not considered
- Conventional testing fails to consider that reactivity of waste is controlled by parameters other than chemistry (e.g., microbiology, type and occurrence of minerals, texture and hardness)
Thus, accurate prediction is challenging because of the multifaceted processes leading to ARD. Hence, risk assessments need to consider mineralogical, textural and geometallurgical rock properties in addition to predictive geochemical test data.
Enhanced prediction of ARD
A new architecture of integrative, staged ARD testing have been developed by CRC ORE. Better ARD prediction starts with improving the definition of geoenvironmental models and waste units. Then, a range of low-cost and rapid tests for the screening of samples should be conducted on site prior to the performance of established tests and advanced analyses using state-of-the-art laboratories. ARD prediction would support more accurate and cost-effective waste management during operation, and ultimately less costly mine closure outcomes.
- Enhanced laboratory tests
- Microwave assisted thermal energy (MATE) pH test
- Computed Acid Rock Drainage (CARD) risk grade assessment protocol
- Low-cost test to predict the bio accessible form of environmentally significant elements which could elute from mine waste materials
- Predictive waste classification
- Improved geochemical and mineralogical characterization of dust
- Characterisation of mineral dust properties
- Geometallurgical indicators for predicting ARD