Background
SGME was engaged to use our expertise to provide the optimal solution for designing a waste rock dump (WRD) cover system. This involved completing verification studies which included in-situ trials and large-scale column trials. The mine is an open cut copper mine located in northern Queensland. At the time of the project, the mine had ceased operations and had been placed under care and maintenance.
Objective
A cover system design was required for the WRD which consisted of potentially acid forming (PAF) waste rock placed under non-acid forming (NAF) waste rock. Based on the geochemical analysis of the waste and available resources, three cover options were trialled to select the design which would limit seepage.
Solution
Three columns (ie one for each cover option) were built to specifications provided by SGME. The columns were instrumented with volumetric water content and matric suction sensors to measure how rainfall infiltration is stored within the cover. Seepage was measured using rain gauge tipping buckets.
The column trials were subjected to thirteen artificial rainfall events over a five-month period in order to develop a maximum water balance. The experimental data was used to analyse capillary rise potential, infiltration and seepage through cover options. A numerical model was used to predict the long-term performance of the cover options under wet, average and dry conditions, and to verify the preferred cover.
During the second phase, the preferred cover was built on the WRD and was instrumented with in-situ volumetric water content and matric suction sensors. Monitoring is ongoing and is reviewed annually to examine how the preferred cover is performing against the column trial predictions.
SGME enhances cover and landform design through expertise in soil chemistry, physics, unsaturated soil mechanics and environmental engineering. Our innovative use of growth media amendments, revegetation strategies and engineering solutions improves cover and landform performance which reduces environmental risks and ensures long-term stability. We develop solutions that meet regulatory requirements and support sustainable practices by taking a holistic approach that considers safety, stability, sustainability, cost-effectiveness and capacity for post-mining land uses. SGME’s commitment to continuous improvement through ongoing learning about technological advancements, regulatory changes and industry best practices ensures our designs remain innovative and sustainable; thereby delivering effective solutions for mine waste management that contribute to having enduring environmental protection and achieving responsible post-mining land uses.
