The Batu Hijau Project involves the development of 200 million tonnes per annum copper/gold mine in the coastal mountains of south west Sumbawa. The project will mine ore from a large open pit centred on the mountain of Batu Hijau. Ore from the mine will be transported to the 132,000 tonnes per day concentrator via a 5.5 km overland conveyor. The concentrate will be transported about 18 km to storage and port facilities at Benette Bay. The Benette Bay facilities are linked to the mine and township by a 25 km access road which traverses steep mountainous terrain. The mine waste dumps, which ultimately will contain about 3.5 billion tonnes of soil and rock, are to be constructed in three valleys close to the mine. The waste dump management facilities include a number of dams, water diversions and acid water treatment facilities.
Scope of our Involvement:
Golder involvement has been to provide geotechnical investigations, detailed geotechnical engineering design/documentation and construction supervision for all phases of the project from feasibility study through to construction and mine operations. Geotechnical investigations have been carried out both onshore in remote areas and offshore in Benette Bay. During the construction phase Golder established a permanent site engineering office and laboratory.
The project has presented many challenges which have been solved in timely, innovative and cost effective ways:
- The geotechnical investigations which have been carried out over a period of 4 years have mostly been in steep remote areas of the project and have been carried out in advance of construction of permanent access. In most cases small hand portable or helicopter transportable drill rigs were used.
- The steep natural terrain has required the construction of numerous very large cuts and fills for the infrastructure facilities. The deepest cut is in the order of 90 m and the highest fill about 70 m. The design of these has been approached from a risk management perspective.
- Three large retaining walls have been constructed for the infrastructure facilities. These walls, each in the order of 25 m high and up to 800 m long, have been designed and constructed using mechanically stabilised earth (MSE) structures.
- The project site is in an area of high wet season rainfall and high seismic activity. The average annual rainfall is in the order of 3500 mm and the design earthquake acceleration for the project is 0.32 g.
- The entire project has been designed to be constructed and operated to world best environmental practice which has been achieved during construction through a wet season of record rainfall.
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