The majority of water used at Olympic Dam is supplied from the Great Artesian Basin (GAB), a resource shared with Indigenous peoples, communities, agriculture and other industries. The GAB is the largest groundwater basin in Australia, covering more than 1.7 million square km across Queensland, New South Wales, South Australia and the Northern Territory. The GAB is unique because of its naturally occurring springs, which are environmentally and culturally important. They support unique ecosystems of flora and fauna, and are significant to local Indigenous peoples.
Effective and appropriate water stewardship at Olympic Dam is not only essential to BHP’s mine’s operation, but for its long-term sustainability and contribution to social value. Ineffective management of Olympic Dam’s interactions with the GAB is a recognised catchment risk.
Types of water usage
Different types of water are used at Olympic Dam, including:
- Drinking water: For showering, drinking and ablutions at the mine. Water from the GAB is desalinated onsite and is also supplied offsite to accommodation villages and the nearby towns of Roxby Downs and Andamooka. It is treated and monitored to ensure it meets the Australian Drinking Water Guidelines.
- Mining: Water is used in the mine’s drilling process and for dust suppression. It is not required to be of high quality, so we use local saline aquifer water, decreasing the use of GAB water. In FY2019, approximately 2,100 meglitres of locally source saline water was used, which proportionally decreased the use of GAB water.
- Ore processing and grinding: Water quality is important for ore processing and in most cases, water directly from the GAB is sufficient. In some cases, desalinated water must be used. About a third of GAB water used at Olympic Dam is for grinding (the process of turning large rocks into very fine particles). Once the ore has been ground, water is separated from the ore and reused. The amount recovered is monitored to ensure water reuse is maximised.
- Smelter: The smelter uses about 25 per cent of Olympic Dam’s water, mainly in the evaporative cooling towers. The towers regulate the temperature of the cooling water that controls the temperatures of the furnaces in the smelter.
- Acid plant: Olympic Dam produces 98 per cent sulphuric acid onsite from the sulphur dioxide produced in the smelting process. This requires high-quality water produced by treating GAB water onsite.
Managing our water impacts
We do this at Olympic Dam by:
- Regularly monitoring the drawdown and spring flows around our abstraction wells, and by water pressure monitoring of nearby users;
- Using modelling to predict the impact of all user activity on the GAB; and
- Capping, repairing and restoring uncontrolled bores to recover pressure across the GAB, in conjunction with the GAB Sustainability Initiative and separately with landowners.
An inability to obtain continuous water supply is as an operational risk at Olympic Dam. This is managed by routine maintenance on all critical equipment. We also monitor our water use daily to prevent an unplanned increase in water consumption.
We recover and reuse water by:
- reusing the rejected water from desalination in the processing plant;
- reusing water that accumulates in the underground mine for drilling;
- reusing liquor from tailings in the processing plant; and
- recovering and reusing water from the grinding process.