Mining and ore processing waste
Mining operations produce significant volumes of waste rock and tailings. Of particular importance is waste that is chemically reactive and poses risks due to acid rock drainage and other geochemical hazards. In addition, associated activities can create large volumes of waste, some of which is hazardous. Consequently, appropriate waste management is required to minimise environmental impacts and risks associated with waste disposal. At our Prominent Hill operation, waste is managed onsite in disposal facilities in accordance with the OZ Minerals Waste Rock Management and Tailings Management Standards. These standards define the requirements for the management of waste rock to prevent environmental impacts, promote beneficial post-mining land uses and reduce post-mining rehabilitation and closure liability. To prevent or minimise the potential environmental impacts associated with waste rock and tailings disposal, a range of strategies are implemented during project development and operations. These include:
- geochemical characterisation of acid-generating materials, resource modelling;
- selective handling and encapsulation of waste rock;
- disposal of tailings into specially designed and engineered facilities;
- linking operational planning to long-term closure management; and
- the containment and treatment of mine waters to meet regulatory discharge criteria.
Over the reporting period, Prominent Hill produced 35 million tonnes of waste rock and 6.5 million tonnes of tailings. Most of the waste rock generated was placed in rock dumps within the mining areas, with the remainder used for the construction of mine infrastructure. Of the total tonnage of waste rock produced in 2009, 17.8 million tonnes is considered to be potentially acid forming.
Hazardous and non-hazardous waste
All hazardous wastes, non-hazardous wastes and wastewater must be managed in compliance with applicable laws, regulations, as well as in accordance with OZ Minerals Sustainability Standards. Prominent Hill generated 234 tonnes of hazardous waste during 2009. Waste oil was the dominant component at 268,000 litres (equivalent to 228 tonnes) generated, all of which was recycled. Other waste streams consisted of vehicle batteries, grease and medical/biological waste that was disposed offsite through approved disposal facilities.
A total of 1,305 tonnes of non-hazardous waste was generated at Prominent Hill during the reporting period, comprising mainly sample ore and general rubbish. Of that, the majority was disposed onsite. A waste audit was conducted for the Prominent Hill site in December 2009 to identify improvements to the site waste management and recycling program.