Five longwalls approved for Dendrobium

THE New South Wales government has approved scaled back plans for five longwalls at BHP Billliton’s Dendrobium mine in New South Wales, after it gained mining approval for its Area 3B five years ago.
Five longwalls approved for Dendrobium Five longwalls approved for Dendrobium Five longwalls approved for Dendrobium Five longwalls approved for Dendrobium Five longwalls approved for Dendrobium

A stockpile of coal from South32's Illawarra Coal's Dendrobium mine

Lou Caruana

The Department of Planning and Infrastructure approved a subsidence management plan (SMP) for Area 3B, which it needs to manage potential impacts and define intended mining practices.

BHP Billiton had initially sought approval for a SMP to mine 10 longwall panels in October. It has completed mining across three areas within the Dendrobium complex – Areas 1, 2 and 3A – which included mining near Lake Cordeaux with negligible impacts on water supply.

The department said the approval would support 1000 jobs and the Port Kembla steelworks, while safeguarding the metropolitan area’s water supply.

The mine directly employs 400 workers, supports a further 600 indirect jobs and plays a critical role in supplying premium coking coal to the Port Kembla and Whyalla steelworks.

“In making the decision, the department was satisfied that impacts on Sydney’s water supply would be negligible,” the department said.

“It also balanced any of the mine’s impacts against the potential loss of hundreds of jobs and associated economic activity.”

The department has also stated that it would have preferred BHP Billiton had come to it with a draft SMP much earlier, to allow additional time for it to be discussed and resolved.

“The department will be raising this issue as a matter of industry practice with the Minerals Council of NSW,” it said.

Under its approval, BHP Billiton subsidiary Illawarra Coal can only mine the first five longwall panels (panels 9-13) and needs to gain a further approval to mine the second five-panel set (panels 14-18).

This second approval will only be given if mining in the five first panels leads to satisfactory environmental outcomes.

Extensive ongoing independent environmental audits of the impacts of mining in Area 3B would also be needed, the department said.

The company must submit a compensation package for possible swamp impacts, which could include protecting and conserving other nearby degraded or at-risk swamps.

The company must also fund a $3.5 million research program over five years to improve scientific understanding and industry practice in rehabilitating upland swamps affected by mining.

Illawarra Coal must also ensure via the conditions of approval that any impacts on the Avon Reservoir are not greater than negligible.

While there are expected to be impacts on the eight upland swamps situated above the first five longwalls, there are about 1000 similar swamps situated across the Woronora Plateau.

The longwalls in Area 3B are proposed to be extracted from the Wongawilli Seam, of the Illawarra Coal Measures.

The Wongawilli Seam underlies the Bulli Seam by approximately 20m.The Wongawilli Seam in Area 3B is nominally 10m thick and contains numerous bands of non-coal material.

The seam floor within the SMP area generally dips from the south to the

north, with an average dip of about 2 %, or 1 in 50.

The economic section of the Wongawilli Seam is the basal 3m to 5m.

The estimated total amount of longwall ROM coal designated for extraction from the Dendrobium Area 3B is 47 million tonnes, including 3.1Mt of associated development roadways.

Illawarra Coal president Troy McDonald said the approved SMP for mining Area 3B incorporates a rigorous environmental assessment, including groundwater studies, resulting in plans designed to manage impacts in the application area.

“Illawarra Coal has been successfully mining at Dendrobium without any significant environmental impacts since approval was granted by the New South Wales Government in 2001,” McDonald said.

“Extensive monitoring and reporting to government shows no reduction in water catchment yield and no water transfer from Lake Cordeaux to existing underground workings.”

The company’s mine plan for Dendrobium Area 3B was developed following a rigorous environmental assessment, including groundwater studies, resulting in management plans designed to address impacts. The plan also addresses specific actions to manage the environmental features in the area, based on robust science and ongoing monitoring.

McDonald said Illawarra Coal has designed the mine plan to avoid significant impacts to key environmental features in the area such as Avon Dam and Wongawilli Creek.

“We have developed a mine plan which positions our longwall blocks well away from the full supply level of Avon Dam and several kilometres away from the dam wall,” he said.

“Illawarra Coal has led the industry with mine planning decisions which protect the region’s unique environment, and recognises the value of the catchment area and its role in our region’s water supply network.

“We will continue to work with all stakeholders in the community and government agencies to ensure the continued safe and environmentally responsible management of our operations.”