SERIOUS step change

Increasingly a mine's social licence to operate is being heralded as an intrinsic operational consideration. 

During the heights of the drought when water levels at Sydney's dams fell to record lows, GlencoreXstrata's Tahmoor was in 2006 labelled as one of the region's biggest water users. 

With tough water restrictions in place the mine was facing mounting pressure from government and the community to improve its water usage record. 

"In 2006 when company representatives read the Sydney Morning Herald article they acknowledged that water consumption which had been historically accepted could not go on, and so set out to establish a solution which met the needs of the mine, without compromising or impacting the local community or environment," the company said. 

Owned by Xstrata Coal at the time, internal targets to reduce potable water inputs were set, the miner aimed to achieve a 15 per cent reduction of fresh water use over five years from 2007 to 2012. 

The underground coal mine, located in the New South Wales Southern Highlands 75 kilometres south west of Sydney, operates on the Bulli coal seam primarily producing hard coking coal which is on sold to European and Asian markets. 

In the past to run its underground and many surface processes the operation had to purchase about 1.5 million litres of potable water per day from the Sydney Water main supply system. 
Cooling and dust suppression were billed as the most water intensive activities. 

The miner's initial proposal to recycle water outlined a reverse osmosis plant which would treat waste water. 

But a detailed review of the concept found the plan would see electricity consumption soar and heavy vehicle traffic within surrounding rural towns climb. 

"This [plan] would require eight B-double tanker return trips from Tahmoor to Port Kembla for disposal, daily via the township of Bargo, imposing heavy vehicle traffic on the previously quiet rural town," the company said in a statement. 

And so it was back to the drawing board for the miner. 

Xstrata Coal designed a treatment plant utilising groundwater from the base of a ventilation shaft on site. 

Previously the water source had been mixed with process water from Tahmoor's underground operations, pumped to the surface sedimentation ponds and discharged into the Bargo River in accordance with dewatering licences. 

The alternative idea was billed to be more sustainable, producing water with lower capital and operating costs as well as reduced energy requirements. 

Following several years of consolation and design reviews with government and environmental agencies GlencoreXstrata began constructing a 1 megalitre (ML) per day capacity Recycled Water Treatment Plant, and two 250 000 litre concrete water tanks to supply treated water to the underground mine.  

Capital costs equated to approximately $3.31 million, of which $2 million was funded by the NSW State Government as part of a Water Savings Funding Agreement through the Office of Environment and Heritage. 

In 2012, Tahmoor Colliery completed construction and commissioning of a sustainable recycled water management system to service the operation, conserving approximately one million litres of fresh drinking water per day, by treating and utilising waste mine water.  

Water savings equate to about $620 000 per annum in operational expenditure at the site. 
"The Recycled Water Treatment Plant has offset Tahmoor's daily potable water consumption by approximately 1 ML each day, utilising a simple and sustainable low energy water treatment process to produce fit for purpose water to the mine," the company said. 

"The operating cost of the treatment plant is less than the cost of purchasing water (approximately $150 000 per year)." 

The company said implementing the recycled water system required a change in the way process water is used underground. 

"Co-ordinated through our change management process, substantial consultation and communication with employees and contractors has taken place to explain the reasons for the change and to address any concerns," the company said.

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