Going green from greenfields

Increasing environmental management concerns has seen a unique approach to coal mine planning in the Hunter region. Cole Latimer reports.

As the Hunter Valley continues to be one of the central coal districts for the nation, it is facing a number of dilemmas.

The employment that the mines bring has increased the population numbers of the region, which in turn has lead to a greater demand for resources and land.

As more people move into the area, greater scrutiny is being paid to how new mines are constructed in regards to achieving maximum output and maximum care for both the com munity and environment.

Added to this is the introduction of more stringent government legislations regarding environmental management.

With this in mind, the thermal coal company Wallarah Coal has undertaken a unique and ‘environ mentally sustainable’ venture for its coal project in the very lower fringes of the Hunter Region.

Originally a joint venture between BHP and Korean and Japanese parties, the site formerly known as the Wyong Area Coal Project and now as the Wallarah 2 Coal Project has taken a very distinct approach to longwall coal mining in the region.

Speaking to Australian Mining, Wallarah Coal director Peter Smith said that being a Greenfield mine site has allowed for some innovative and environmentally friendly approaches to mining that would typically be very costly for a currently operating mine.

While it is still in the last plan ning stages, Smith expects the mine to be a leader in green and low impact mining approaches.

Located on the Central Coast, the proposed mine is near residential areas as well as a large body of water.

One of the major problems that the mine faced was how to extract its JORC resource of 1.2 billion tonnes of thermal coal with out contaminat ing or adversely affecting the local water tables and ground water.

As it is mining under Tuggerah Lake, the Jilliby State forest as well as the Dooralong Valley, Wallarah chose to mine only a fraction of its resource.

What made this situation all the more difficult is the depth of the coal – the shallowest at 350 metres and the deepest at 650 metres.

In comparison, Centennial Coal’s nearby Mandalong coal mine has its deepest coal at around 350 metres.

To tackle the problem of the local water table and subsidence, Smith told Australian Mining the Wallarah Coal project was “designed for the water in the area”.

It approached this in a number of ways, firstly by narrowing the long wall and excavating only three metres on what has the potential for being a six metres seam.

The company decided to mine only 200 million tonnes at five million tonnes per annum from the longwall instead of its full resource.

Wallarah Coal “sacrificed quan tity for stream and water protection”, Smith said.

“The narrowing of the longwall also helped us to comply with the problem of subsidence in what is known as a serious mine subsidence area,” Smith said.

However, it was the fact that the mine itself will be so deep underground that lessened the effect on ground water and subsidence.

According to a recent Govern ment inquiry into the mine “while longwall mining is likely to cause subsidence-related impacts, because of the depth of the coal seams, this subsidence is unlikely to compromise in any significant way the water supply.”

However, Wallarah did not just approach these concerns from an underground perspective, it also took a number of unusual approaches to water conservation above ground.

Wallarah aimed to have a negligi ble impact by having a dedicated water treatment process for water brought up during mining, which it could then provide back to the community.

A major defining factor in this ap proach was the decision to not include a coal washery or tailings dam on site.

Instead the company will only crush the coal.

“While the company faces a penalty due to the fact that the ash will not be reduced, the project contains thermal coal which is already fairly low in ash and has only one third of the sulphur so it obviates the need for a coal wash ery while reducing water consump tion,” Smith told Australian Mining.

Ash from the site is predicted to be between 14% to 16%.

On the back of this, the project is also looking into the option of water recycling facilities onsite.

Any water generated by the mine will be used in the crushing and stock piling process and for controlling dust, with the surplus water being recycled into the community.

This reuse and recycling of water is a major factor in the Wyong region which recently saw water restrictions reach level four.

Wallarah is aiming to “have serious environmental credentials after respond ing to the stakeholder and commu nity concerns.”

The Wallarah Coal project is also looking to gain further environmen tal credentials through its innovative energy usage processes and physical impact on the local landscape.

The company has the majority of its surface facilities located some distance away from the mine itself.

In one instance the facilities are four kilometers away from the mine.

To lessen the impact upon the local landscape and reduce the need for miles of conveying systems, the mine was designed with an incline to the site just for handling and transport of its production, reducing the need to install many conveyors across the land.

Another green option, pioneered by AngloCoal’s Moranbah coal mine, is the capture and usage of gas released during coal mining.

Wallarah is looking at a number of options for gas that it will drain pri or to mining as well as during mining.

The gas will be captured princi pally underground as part of safe mining operations rather than via surface drilling and groundworks typical of commercial gas extraction operations, Smith told Australian Mining.

This captured gas can then be used to power operations at the site, reduc ing its carbon footprint.

The energy produced can then be sold back to the power stations as well, he added.

With the wide ranging and inno vative approach to environmental management in mine site planning, the expected Wallarah Coal Project looks set to be a fore runner for a new wave of greener mines.

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