Wyong's biggest challenge

ESTABLISHING an underground mining project can be difficult, particularly when there are 120,000 people living on the surface with little understanding of underground coal mining.

Staff Reporter

This is one of many challenges facing the massive Wyong project, situated between Sydney and Newcastle in New South Wales. The lease area covers some 260sq.km.

The major issue for the Wyong community is fear of subsidence, but at 400m the seams are relatively deep, which means subsidence is actually a minor risk. Other issues include sensitivity about mining under Lake Tuggerah and general fears about the impact of mining on the environment.

“By the time we get to the development consent we will have spent well in excess of $50 million on exploration, land and environmental feasibility,” said Wyong project manager, Beau Preston.

Exploration rights to the Wyong project are 78% owned by Billiton subsidiary, Coal Operations Australia Ltd (COAL), the project operator. Korean utility groups own 17%, while Nissho Iwai holds the remaining 5%.

Wyong’s two major exploration areas are 400m below Lake Tuggerah, covering about a quarter of the area, and a second area to the west beneath state forest and rural land. The steam coal resource under surface cover of 400-600m, measures over 1000 million tonnes, with the seam ranging in thickness from 1.9-8m. Geological structures include plugs, dykes, faults and split seams.

COAL began exploration in 1996 with four drilling rigs in the western area and a purpose built drilling platform on the lake. Some of the concerns COAL has had to contend with include the effect of drilling overshadowing seagrass beds, which provide fish feeding areas, and drilling materials entering the lake.

Preston said from the beginning of the project, communication with the community had been a major priority. During its first four years of operating, COAL representatives have had more than 200 meetings with community groups. The company’s Wyong-based offices are open to visits from the public and frequent newsletters are disseminated covering subjects such as local geology, mine planning, groundwater, and subsidence.

Four years of exploration have delivered over 65,000m of drill core with every piece of data — including geophysical logs, geotechnical testing and coal quality — stored on Maptek-developed Vulcan 3D modelling software. The stringent environmental constraints have to be taken into account during the mine planning process and Vulcan is capable of generating longwall panel layouts which maximise extraction and coal quality, while conforming to subsidence criteria. Varying the width of longwall blocks within a single panel is one of the options being examined.

To date, COAL has completed preliminary financial, environmental and conceptual mining studies in the lead up to pre-feasibility level. Preston said COAL hoped to have an Environmental Impact Statement (EIS) lodged by mid-2002. A development consent is expected to be granted six months to a year later, with construction potentially beginning in late 2003, or early 2004.

Preston said COAL was well advanced with conceptual mine planning which include 20-year schedules. Important issues under careful examination include placement of surface infrastructure, and ensuring no hydraulic connection between the 400m deep workings and the lake.

“Potentially we could have a dual longwall operation in the western area, producing in the order of 10Mtpa. In the eastern lake area there is potentially one longwall producing in the order of 5Mtpa. We’re talking about a very large operation,” said Preston.

Originally published in the March 2001 edition of Australia's Longwalls.