Alcoa mines bauxite in the sensitive jarrah forest environment and within water supply catchments. Water from these forested catchments is of excellent quality and requires minimal treatment before distribution to the Perth metropolitan region.
To ensure the continued supply of high quality water, the Water Corporation has placed strict conditions on access to, and activities within, water supply catchments. Alcoa's strong commitment to minimising adverse impacts from its operations has ensured that bauxite mining is one of the permitted land uses within these catchments.
Therefore pollution prevention measures are an essential component of the mining environmental management program and require careful management of waste water, dangerous goods, hydrocarbons, and other chemicals.
Runoff and Turbidity Control
Of particular concern to Alcoa is turbidity, which is a measure of the amount of mud and silt in water. While stream turbidity levels in the native forest are naturally low, high sediment levels in mine runoff can affect the quality of drinking water, cause siltation of stream swamp zones and even smother vegetation.
Runoff from bauxite mining areas and haul roads has high sediment loads due to the soil disturbance during the various pre-mining and mining operations. To prevent runoff and sediments from damaging forest and stream ecosystems, effective sediment control and erosion prevention programs are used.
Strategies to minimise and eliminate runoff include the use of:
- Drainage protection slots in mine pits;
- Infiltration sumps to retain runoff from mine pits and haul roads;
- Sedimentation sumps on haul roads to treat water before water is discharged to the environment; and
- Final landform designs of rehabilitated areas to prevent discharge of water to surrounding forest.
Alcoa ensures that all mine runoff is collected and channelled for release at or near to streamzones, so that no artificial wet areas are created in the jarrah forest that encourage the spread of Phytophthora Dieback. Mechanisms like blasting or ripping water slots at the base of mine pits help control other water drainage issues.
To reduce the risk of surface runoff damage Alcoa uses an alert system as part of its daily weather forecasting service to warn of impending heavy rain. This allows mine staff to identify vulnerable areas that may need extra protection and ensure that adequate drainage control measures are in place.
The effectiveness of mine runoff control and sediment control practices is verified by monitoring the turbidity of water in various streams around the mine and comparing the data to unmined catchments and pre-mine data.
Turbidity data from the majority of stream monitoring points, along with weather data, is transferred via telemetry to the mine computer network. This real time continuous monitoring system allows for a rapid response to elevated turbidity events. All incidents are investigated to determine the cause and appropriate corrective actions are implemented.
Waste Water Management
All vehicle washdown and workshop hose down water is treated using specialised wastewater plants to remove hydrocarbons and detergents.
Treated wastewater discharge is licensed by the DEC and all water is sampled and tested before release. At both mines, treated wastewater is recycled for haul road watering, vehicle washdown and workshop hosedown.
Sewage at both mines is treated using Biological Aeration treatment Units approved by the Western Australian Department of Health. The treatd effluent is sampled to ensure it meets the appropriate water quality guideline levels.
Alcoa is committed to minimising hydrocarbon (oil, diesel, grease) Loss of Containment (LOC) events associated with the use of heavy machinery. Systems are in place to ensure that operators are trained, and that equipment is well maintained and inspected regularly.
A Mining LOC Reduction Team was established in 2001 to investigate root causes and potential new preventative measures to reduce LOCs. A large number of improvements have been implemented by this team and is reflected in the significant reduction in hydrocarbon LOCs since 2002.
In 2006 a 43 per cent reduction in LOCs greater than 20 litres was achieved by the mines.
All LOCs in the environment are cleaned up immediately and the contaminated material is appropriately disposed of. This means that no hydrocarbons are left I the environment.
For further information about Alcoa's Hydrocarbon Management Plan, please see the pdf.manual at the foot of this page.
Dangerous Goods Storage
Hazardous materials are managed and stored in accordance with the Dangerous Goods Safety Act 2004 and Dangerous Goods Safety Regulations 2007.
Hazardous materials may only be brought on site if the material has been approved by the Industrial Hygienist and Cross Site Mine Environmental Scientist.
It is Alcoa’s policy to prohibit the installation of new underground storage tanks, to remove or decommission existing underground storage tanks, and remove any soil polluted by leaks. This minimises the risk of soil or groundwater contamination. All underground storage tanks have been removed at the mines.
The Contaminated Sites act 2003 and the associated regulations came into effect in December 2006. Under this Act, Alcoa is required to report any known or suspected contaminated sites to the Department of Environment and Conservation (DEC).
Some areas of hydrocarbon contamination were identified as part of the tank removal program. All known contaminated sites have since been cleaned up, in accordance with the Contaminated Sites Act 2003. As a result, WA Mining has no reportable contaminated sites.
Each site has Emergency Response Crews who respond to emergency situations at the mines. The sites have detailed emergency response plans that cover situations such as fires, major storm events, spills of hazardous materials, lost fieldworkers and evacuations.
The Emergency Response crews are regularly trained in the use of spill recovery equipment and mock spill trials are undertaken at each mine.
Alcoa Hydrocarbon Management LOC Manual
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