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Water management at Capcoal

OPERATIONAL needs, societal demands and continuing dry weather had demanded Capcoal assess its water management strategy. On an operational and management level, what will the minesite do to minimise raw water consumption and maintain a balanced worked water inventory?

Angie Tomlinson
Water management at Capcoal

While Capcoal has paid much attention to its water strategy in the past an expanding operation had demanded the company reassess its strategy, Moranbah South and Grosvenor SHEC project manager John Merritt and Water Solutions director John Macintosh told delegates at this year’s AUSIMM Water in Mining conference.

At the Capcoal site the Aquila Colliery has been developed as a bord and pillar operation; the 4.5 million tonne per annum Grasstree mine commenced operation in late 2006. Plus, the new opencut Lake Lindsay operation was developed during 2006 with plans to ramp up to 5Mtpa by 2008.

Together the operations will produce 8.9Mtpa.

In their paper, Merritt and Macintosh said for Capcoal the greatest potential for reduction of raw water wastage was in its underground operations. Underground water uses include dust suppression, cooling of machinery, and clean-up of the coal conveyance system. Often water used for machinery cooling was then used for dust suppression.

“As the pipes delivering raw water underground are in 6m lengths, linked together by Victaulic couplings, the water distribution system is prone to high losses. The way forward lies in a ‘whole of operation’ review of water usage, led by key underground operational personnel and supported by targeted technical studies.”

The duo said studies should focus on the effectiveness of water use for dust suppression on development and longwall operational faces, and at transfer points along the conveyor belt. They said the use of water as a “hydraulic shovel” for cleaning needed to be reviewed.

“The challenge for underground operations, like the challenge for CHPPs [coal handling and preparation plants] in the 1990s to use worked water, will be as much about people management as finding technical solutions.”

In 2005, Capcoal purchased an additional allocation of 500 megalitres of medium priority water – a change from standard practice of owning high priority water – in the Nogoa Mackenzie Water Supply Scheme.

“Future management of Capcoal’s raw water needs could involve not just owning water, but actively participating in water trading schemes to obtain an allocation for the coming year,” Merritt and Macintosh said in their paper.

“The freeing up of trading schemes will move industry from the old way of owning sufficient high priority water, to a new way – of owning a combination of high and medium priority and actively trading to ensure an adequate supply.”

They said a critical factor to successfully moving to trading will be getting the right mix of industries drawing water from the water supply scheme.

“Are there risks with eliminating or significantly reducing Capcoal’s raw water consumption? Yes. The risk is that the salt levels in the site worked water inventory will increase to levels at which the water is not ‘fit for purpose’. Drawing raw water from external sources is integral to future water management at Capcoal, to maintain a targeted worked water quality.”

To maintain a worked water balance, the environment team has been put in charge to work with the mine’s senior management and implement a strategy, and monitor and review the success of the strategy against targets.

The strategy will follow the principles outlined in the Draft Framework for Strategic Water Management in the Minerals Industry released by the Ministerial Council on Mineral and Petroleum Resources, the Minerals Council of Australia and the Queensland Resources Council Water Policy.

The biggest risks for Capcoal looking ahead are increased mining in the Rangal measures leading to increased salinity of the worked water inventory, and the potential stakeholder demand for higher water quality standards for stream flows from site.

The duo said CHPP operators had concerns about the impact of increasing salinity levels in the worked water supply on the plant’s performance.

“Modelling using WaterMiner software, developed by the Centre for Water in the Minerals Industries (CWMI), indicates that salinity levels in Capcoal’s worked water inventory should not increase significantly beyond current levels with the increased production levels from the Rangal measures, assuming the management practices proposed.”

In response to the off lease impact risk, Merritt and Macintosh said Capcoal could increase the number of dams to be constructed within new opencut mining areas to achieve the dual outcome of increased availability of low salinity water for dust suppression on haul roads, and sediment management in run-off water from the lease area.

In the future the company saw opportunity in segregating worked water into two qualities, allowing substitution for raw water and/or discharge of worked water with higher water quality from the lease in high rainfall years, provided that regulatory and other stakeholder expectations were met.

Merritt and Macintosh said there was much to learn from Capcoal’s experience, as well as many other mines demonstrating leading practice.

For greenfield developments, the following lessons can be learned:

Ensure that a senior manager is allocated responsibility for water management with designated accountabilities for operational and strategy development.

Consult with stakeholders early and regularly.

Develop the water management strategy, objectives and targets early in the project life cycle in accordance with sustainability principles.

Maintain a site water balance model of both quantity and salt loads. Remember a nil discharge target may not be appropriate.

Assess the project against objectives, applying risk management techniques regularly as the project evolves through the life cycle to ensure appropriate controls are planned and implemented. In the feasibility stages, project design controls should be identified to allow the objectives to be met, eg worked water system in CHPP able to meet peak water demands; CHPP components designed to ameliorate the corrosive properties of a saline water supply.

Identify the critical components and parameters for the water balance model, together with the appropriate monitoring systems.

Monitor and report water management performance.

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