Earth and Environmental Science
Home > Earth and Environmental Science > Options > Mining and the Australian Environment > Mining and the Australian environment: 5. Consider and address environmental issues
9.7 Mining and the Australian Environment: 5. Consider and address environmental issues
Extract from Earth and Environmental
Science Stage 6 Syllabus (Amended October 2002). © Board of Studies,
NSW.
[Edit: 28 July 09]
Background: Several aspects of mining affect the immediate environment. Firstly, the waste materials which are produced from the mine may flow into waterways or leach into soil, heavily polluting the ecosystem. Secondly, the removal of both flora and fauna from the mine site leads to gaps in the food chain for those fauna remaining, as well as problems with succession of plants after the mining has ceased. To minimise the damage mining companies are now required to conduct Environmental Impact Statements and look towards rehabilitation of the site.
gather information from secondary sources, or field studies, to present information in terms of the environmental impact of the exploration, extraction and processing methods used for the mine site
The following is an example of what you could present as a case study.
Example: Porgera Gold Mine
- The Porgera gold mine is located 130 km northwest
of Mount Hagen, Papua New Guinea, and is operated by Placer Pacific and the
Papua New Guinea Government.
- The ore deposit is estimated to contain approximately
59 million tonnes of gold and silver ore, making it one of the largest gold
mines in the world.
- Most gold and silver ore can only be extracted through
subjection of the ground ore to froth flotation. The slurry which results
is oxidised and treated using sodium cyanide and electrolysis.
- This extraction and processing method serves to convert
free cyanide to stable ferric and ferro-cyanide complexes, precipitate any
dissolved metals as sulphides, as well as precipitate trace metals as hydroxides.
- Despite these measures, there are signs of environmental
damage:
- The heavy metal contaminants in the river sediments are sufficient for it to be declared a contaminated site.
- Mercury levels are at levels that are usually only found below a mercury mine.
- Sediments can cause physical damage to fish, crustaceans molluscs and insect larvae through abrasion.
- Sedimentation can smother eggs or prevent breeding, thus damaging spawning grounds.
- Sediments can restrict light and therefore prevent photosynthesis, affecting underwater plants and predator-prey relationships.
- Bioaccumulation of heavy metals can poison any aquatic organisms.
A news article speaking of the legal action linked to environmental damage caused by the Porgera gold mine Journal of Remote and Rural Envoronmental Health 1(1): 10-12 (2002)
assess the likely environmental effects of exploration, mining and processing methods for the deposit
Example: Uranium
Environmental impact of exploration and extraction
- All mining extraction obviously involves altering the natural environment
in some way. For this reason, rehabilitation (see information below) plays
a major role in the feasibility study of the potential mine site.
- Uranium mining is associated with more radioactive
elements such as radium and radon which may be present in the ore. Therefore,
especially if the ore is of high quality, it is treated with great care because,
although the uranium itself is not very radioactive, other radioactive elements
present make it dangerous.
- During extraction, uranium dust is controlled, as
it contains significant levels of radium and radon, and represents the main
potential exposure to radiation.
- Australia’s uranium mines are mostly open-cut
mines and are therefore well ventilated. Radon and radium levels in the air
may be controlled by adequate ventilation, both in open-cut and underground
uranium mines.
- The radon gas may emanate from the uranium ore or
tailings during processing as
radium or thorium decays. Although radon gas is present in very small amounts
in the air we breathe, high levels of this gas may be harmful to both humans
and animals.
- With in-situ mining of uranium, there is an effort to avoid the contamination of any adjacent groundwaters during the leaching process.
Environmental impact of processing
- During the concentration stage of processing
the uranium is recovered from the uranium-rich liquid using
one of a number of techniques. The process water remaining after the uranium
is recovered contains traces of radium and other metals that would have detrimental
effects on aquatic systems if discharged into a waterway. The water is therefore
evaporated and the metals are kept in a secure storage situation.
- The undissolved parts of the uranium ore (the ‘tailings’)
left after the leaching process contain high levels of radiation. Radiation
levels in the tailings dam are therefore significantly dangerous. For this
reason, the tailings are usually covered by water as they accumulate.
- A full report on the environmental effects of uranium
mining may be found on The Sustainable Energy and Anti-Uranium Service SEA-US
website.
evaluate the purpose of the Environmental Impact Statement for the deposit in terms of protection of unique and endangered species, protection of sacred sites, community consultation and local habitat management
- An Environmental Impact Statement is a report that
outlines the predicted environmental effects of planned action or project
in which the federal government is involved. Their main purpose is to inform
decision makers of potential effects of an action before the decision is made.
- In Australia, the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), in force from 16 July 2000 governs all environmental impact assessment.
Example: Uranium
Purpose of the Environmental Impact Statement in terms of protection of a unique and endangered species
- The purpose of an EIS is to prevent the development
of a mine site from causing the extinction or impeding the recovery of any
native species listed under the Environment Protection and Biodiversity
Conservation Act 1999 (EPBC Act).
- Any action which endangers the existence or would impede the recovery of a native species or community listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). is considered to be undesirable unless there is permission granted under the Act pertaining to the recovery plan.
Purpose of the Environmental Impact Statement in terms of protection of sacred sites and community consultation
- The most publicised account of the effects of mining uranium is the plight of the Aboriginal people (with the support of the Australian environmental movement) to oppose the development of a uranium mine at Jabiluka, within the boundaries of Kakadu National Park.
Purpose of the Environmental Impact Statement in terms of community consultation
- According to federal legislation, Environmental Impact
Statements must be made available to the public, federal, state and local
authorities, as well as being filed with the state Environment Protection Authority.
- In the US, The Council on Environmental Quality guidelines require companies conducting Environmental Impact Statements to hold public meetings when their actions spark strong debate or interest. These companies must also inform the public of how to participate in the development of the EIS and allow adequate time for public response before the final EIS is published.
Purpose of the Environmental Impact Statement in terms of local habitat management
- An EIS is conducted only if the action of a company
is of environmental significance. For uranium mining, there are many considerations
when extracting and refining the ore, and thus all uranium mines carry the
requirement of an EIS before mining commences.
- Ranger Uranium Mine is located in Kakadu National
Park so protection of the local habitat is extremely important. The EIS of
uranium mines discuss a number of environmental issues, including water quality,
especially in the Northern Territory where very heavy rainfall can occur in
the wet season, measures which control erosion, minimise vegetation disturbance
and prevent or minimise the creation of mosquito breeding sites. A
report from the Alligator Rivers Region Advisory Committee Department
of Environment and Heritage, will indicate the sorts of issues that are discussed
at a meeting of the wide community on environmental issues.
process information from secondary sources to describe in terms of rehabilitation practices employed at the mine site.
- Information about the rehabilitation
of the Bridge Hill Ridge titanium mine in northern NSW can be found at
the Mineral Information Institute, Golden, Colorado, USA.
- Reports on the rehabilitation of the Nabarlek
uranium mine is available on-line through the Department of Environment, Water, Heritage and the Arts,
Australia.
describe the methods used in the planned, and practised, rehabilitation of the mine site
Rehabilitation of the Bridge Hill Ridge
- BHP Titanium Minerals Pty Ltd began mining rutile
(titanium dioxide) from the dunes of Bridge Hill Ridge, on the mid-north
coast of NSW, in 1974. Mining in the area ceased in 1983.
- Rehabilitation involved a multistep process:
- Extensive research was conducted prior to mining to ensure excellent rehabilitation prospects and seeds were collected for replanting at a later stage.
- Vegetation regrowing after mining was removed and the dunes were mechanical reshaped to contours similar to those before mining.
- Topsoil, which had been stockpiled for 6-18 months, was respread and treated with an initial application of fertiliser.
- A cover crop of sterile Sorghum sp. was planted to promote top soil stability, along with seeds of endemic legumes.
- Once the topsoil was stable, dominant native
trees and shrubs were planted at densities related to pre-mining densities
of these plant species.
- According to the NSW Minerals Council, the area
now resembles an immature forest ecosystem, which will grow with time
to show little evidence that mining ever took place.
- However, a study done in February 2000 by Environmental Biology students at the University of Technology, Sydney, detected significant differences in the abundance and richness of plant species between mined sites and unmined sites, noting the loss of species such as Bracken fern (Pteridium esculentum) and concluding that much more natural development is required in the mined areas before they fully resemble the unmined areas.
evaluate the relationship between mining methods and mine site rehabilitation for the deposit
The contribution of mining to the rehabilitation of the Narbarlek uranium mine
- In the Environmental Impact Statement published in
1979, Queensland Mines Ltd proposed to mine the ore body for six months and
stockpile the ore before constructing a treatment plant on-site to process
the ore over the following eight to ten years.
- The eventual rehabilitation of the area was always
high on the agenda, and several measures were included for the protection
of the environment:
- containment of all contaminated waters
- treatment of tailings (the undissolved minerals remaining after uranium leaching) by neutralisation (to remove acidity or alkalinity) and barium chloride (to remove radioactive traces).
- minimisation of the land to be cleared and used
- return of tailings directly to the open pit, ensuring less pollutants are released and greater protection from residue radioactivity.
- backfilling of the pit with waste rock
- stockpiling of topsoil for the six month mining period, to be followed by the landscaping and revegetation of the mined area on completion
|