EMS Mining

Environmental best practice mining
Acid mine discharge Mining has been part of New Zealand’s history since the 1800s, producing gold, coal, aggregates, industrial minerals, limestone and iron sands. It is an important part of the economy, valued at approximately $1.5 billion per year (Crown Minerals 2007 – excludes petroleum). However, mining can have significant impacts on the environment, so it must be managed in a way to minimise those impacts and ensure environmental sustainability.

Acid mine drainage (AMD)
One of the biggest environmental problems with mining is a process known as acid mine drainage (AMD), also known as acid rock drainage (ARD). AMD is an environmental problem that has been an issue for centuries. In the United Kingdom, Roman mining sites continue to generate acid drainage some 2,000 years after mining operations ceased. The problem occurs when sulphide-bearing minerals in rock are exposed to air and water by mining activity. A breakdown of the sulphides releases acid and can mobilise trace elements such as arsenic, zinc and nickel from waste rock and tailings into ground and surface water. This can have a harmful effect on plants and aquatic animals.

New Zealand scientists tackle AMD
In New Zealand, a team of scientists from CRL Energy, Landcare Research, Canterbury University and the University of Otago is waging war on AMD and adapting successful remedies for a global problem. They have been studying the problem since July 2004, and in that time, they have mapped the extent, level and impact of AMD in the West Coast and Southland regions of New Zealand’s South Island. It is here that historically and presently most of New Zealand’s mining activities have concentrated.

The team has carried out research into rock geochemistry, aquatic chemistry, freshwater ecology, aquatic toxicity, and management and remediation techniques for mining.

CRL Energy’s Geology Group Manager Dr James Pope, who leads the project, says they are now in a position to help with the planning of future mining operations on the West Coast and in Southland. They can also help with the impact of existing mining operations and with fixing the impacts of historic mining operations.

“We’ve developed a framework that provides information on the collection of water, rock and biological information used to predict water quality prior to mining, monitor discharges from mines and identify mining impacts. The framework also provides information on methods and pitfalls in the interpretation of this information. In addition, the framework includes information on state-of-the-art techniques for prevention of poor water quality in mine drainages, optimal strategies for management of mine waste or overburden and remediation of mine drainages if necessary.”

Treating contaminated water
For example, the team developed a way of treating contaminated water by running it through a vertical limestone column. This was very effective, with the limestone reducing the acidity of the water (raising the pH) and cleaning it. Tests on animals known as water-dwelling macro invertebrates (such as freshwater crayfish) found that there was a significantly reduced death rate in the population when the water was treated with limestone in this manner.

Dr James Pope Dr Pope and Dave Trumm, CRL Energy’s Environmental Hydrogeologist, presented 4 papers about the research at the International Conference on Acid Rock Drainage (ICARD) in Sweden in June 2009.

“The material we presented was very well received, especially a paper by CRL Energy’s Environmental Geochemist Dr Rachel Rait on remediation of arsenic-contaminated water using waste products from mine drainage treatment. In general, the research generated considerable interest and opened options for international collaboration,” says Dr Pope.

Dr Rob Whitney, Chief Executive of CRL Energy, says the team’s research has been a catalyst in developing a special edition of the New Zealand Journal of Geology and Geophysics devoted to mine drainage issues. “The research team were also invited by FRST [Foundation for Research, Science and Technology] to submit a proposal into a new research portfolio where the skills developed here might be put to use on different research problems.”

Improved mining practice
Dr Pope says the end result will be better managed access to mineral resources, a raised profile of good mining practices and a more positive image of mining within the general community, all necessary outcomes if the government hopes to realise its goal of increasing New Zealand’s earnings from mineral wealth.

The New Zealand government’s science funding body – the Foundation for Research, Science and Technology – supports the team’s AMD research.

Activity idea
In relation to this news article, your students may like to try this activity in which they research the effect of common pollutants on our waterways and hold a trial to determine the worst pollutant in the country.
Water pollutants on trial
Useful links
Find out more about CRL’s AMD research.
www.crl.co.nz/research/mine_drainage.asp


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