Waste Rock and Tailings
Mining operations produce significant volumes of waste rock and tailings. At the Prominent Hill operation, waste is managed on site 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 and tailings 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 approximately 53 million tonnes of waste rock and approximately nine million tonnes of tailings. Of the total tonnage of waste rock produced in 2010, 30 percent is considered to be potentially acid forming all of which will be physically contained. Water sampling of bores surrounding the tailings storage facility is regularly monitored for acidity, as part of the acid rock drainage program. We routinely monitor radiation particles present in waste rock as well as regularly monitor downstream creeks for changes in acidity.
Most of the waste rock generated was placed in rock dumps within the mining areas with a proportion of non-acid forming rock used for the construction of mine infrastructure, such as the tailings storage facility and roads. All tailings are contained within the tailings storage facility.
Water sampling is conducted after heavy rainfall events at sites around the tailings storage facility and surrounding waste rock to ensure there is proper containment of heavy metals and acid generating tails.
Hazardous and Non-Hazardous Waste
All hazardous wastes, non-hazardous wastes and wastewater are managed in compliance with applicable laws and regulations, as well as in accordance with OZ Minerals Sustainability Standards. Prominent Hill generated 403 tonnes of hazardous waste during 2010, of which most is from waste oil.
In 2010, a vein of fibrous material was exposed in the open cut mine and was identified as antigorite, an asbestiform mineral. Discussions were held with the South Australian Environmental Protection Agency in regards to the disposal and management of the material. Any asbestiform material that is discovered is relocated, contained and encapsulated in the waste rock dump site. Any items that are associated with this material, for example clothing, gloves and respirators, are double bagged and encapsulated in the site waste dump. For information regarding the safety and health management of asbestos, please refer to the safety and health section of this report.
A total of 436 tonnes of non-hazardous waste was generated at Prominent Hill during the reporting period, comprising mainly general rubbish, which was disposed off site in approved waste management facilities.
The main types of non-hazardous waste produced at Prominent Hill includes general domestic rubbish, wood, cardboard and paper, steel, glass and aluminium. All are managed in accordance with the OZ Minerals Waste Management Standard and Prominent Hill Non-Hazardous Waste Management Plan. All glass and aluminium waste has been stored for future recycling and all scrap steel is recycled off site.
An external audit was conducted in 2010 on waste being sent to landfill from the Prominent Hill operation. The results of the audit has allowed OZ Minerals to gain a better understanding of overall processes of waste on site, identify initiatives to reduce waste to landfill, improve resource recovery and facilitate future cost analysis and policies.