Background
SGME was engaged to oversee the construction, monitoring and reporting of the cover column trials for a tailings storage facility (TSF). The mine includes multiple underground operations which produce copper, silver, gold, lead and zinc near Cobar, New South Wales. During operation, deposition of tailings from the central spine results in a concave landform.
Objective
A conceptual cover design had previously been prepared that incorporates a reduced permeability layer (RPL) overlain by a capillary break (CB) overlain by 0.2 metres of soil. The company wished to take a step back from the conceptual cover and explore the potential of installing a less complicated cover option based on regional experience at other mines. This proposed cover comprised a mono-layer cover of growth media without an RPL or CB.
Solution
The project consisted of a number of elements including the identification of alternative covers which would progress to cover column trials. Firstly, a literature review of the tailings and potential cover materials was carried out which examined geochemistry, groundwater, surface water, soil and cover requirements. Following this, an environmental risk assessment for the cover system was done to define the basis of design and to guide establishment of objectives. A preliminary (uncalibrated) model was subsequently developed in a numerical modelling package to determine alternative cover options to progress to cover column trials.
The cover column trials were instrumented with volumetric water content and matric suction sensors. Following construction, the cover column trials were subjected to several artificial rainfall events over seven months to develop a maximum water balance. A semi-calibrated numerical model was developed using the maximum water balance to predict how the cover options would perform if constructed on the TSF.
The outcome was the identification of an alternative cover option that effectively limits seepage and achieves comparable results to those documented in literature and below the maximum desirable seepage rate.
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, reduces environmental risks and ensures long-term stability. We take a holistic approach that considers safety, stability, sustainability, cost-effectiveness and post-mining land use capacity to develop solutions that meet regulatory requirements and support sustainable practices. 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, and ensures effective solutions for mine waste management are delivered that contribute to enduring environmental protection and responsible post-mining land uses.
