What happens to the excavated waste rock at one of Australia’s significant mine sites when the mine closes? This topic isn’t being taken lightly by Newcrest Mining at Cadia Valley, 20 kilometres southwest of the city of Orange in NSW where PhD student in Charles Sturt University's (CSU) School of Agricultural and Wine Sciences, Mr Allan Adams is investigating a sustainable solution.

 

In the first year of his PhD, Mr Adams is researching sustainable options for Newcrest Mining to construct wetlands, planted with native grasses to capture and store the excess metals, copper, manganese and zinc leaching from the excavated waste rock dumps. The by-product or ‘leachate’ has the appearance of clear creek water.

 

“The metals naturally occur in any plant or animal and are essential for the health and development of every species at certain levels but there are excessive quantities within the leachate, which some plants can help dissipate,” Mr Adams says.

 

Mr Adams explains that, as part of the mining operations, mine waste rock generates leachate which the mine operators store using a leachate pond, designed to capture the leachate for re-use in the mining process. 

 

“It is thought that the mine will continue to be operational for the next twenty years but Newcrest Mining is looking ahead and is already preparing for mine closure as part of the long term management of the site.”

 

“When the mine closes there are alternative methods available for remediation of contaminated leachate that utilise chemical and engineering practices which are expensive and not sustainable,” Mr Adams says, “my mission is to present Newcrest Mining with a sustainable plant-based solution, known as ‘phytoremediation’, (phyto meaning plant), that can be put into place almost immediately.”

 

Mr Adams has spent the past twelve months researching native wetland plants with the potential to perform as leachate remediaters.

 

“I’ve looked at fifteen different plants and will trial four that have the potential to capture and store  the metals without becoming stressed,” says Mr Adams. “There are very strict water quality guidelines that must be adhered to when exiting a mining site and it’s important that every measure is taken to ensure the site is returned to a condition where plants can continue to grow”.

 

The next phase of research for Mr Adams will include planting and then monitoring the introduced species to assess their viability at the mine site.

 

According to Environmental Earth Sciences International, almost no mines in the modern era of mining in Australia have successfully completed closure to the point where the mining lease has been handed back. This is because authorities have not been reassured that the long term legacies of mine waste have been addressed.

 

Newcrest Mining Environmental Scientist in Operations, Mr John Ford believes that, if Mr Adams’ research is successful, a sustainable solution would be advantageous to the management of the Cadia Valley site.

 

 “Cadia Valley is quite unique because it is so close to a large city and Newcrest has always been mindful of the need to find sustainable options for mine closure,” Mr Ford says. “We believe that, through early investigation and development of sustainable mine closure solutions, Newcrest Mining could be one of the first to provide stable, productive and sustainable landscapes as part of our rehabilitation of the mine site.”