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Environmental studies help minimise impact in Harmony’s Papua New Guinea project


Publication: Mining Weekly
Journalist: Guy Copans

Gold-mining company Harmony Gold has undertaken a number of environmental studies to ensure that the environmental impact of its Hidden Valley project, in the Morobe province of Papua New Guinea, is kept to a minimum.

The Hidden Valley project, with a capital expenditure of R2 684-million, entails the construction of a significant gold and silver mine. Once construction of the mine is completed in 2009, this mine will process 4,2-million tons of ore a year from the two openpit mines, namely Hamata and Hidden Valley-Kaveroi. Harmony’s 2007 annual report indicates that the engineering progress is 54% complete.

The baseline environmental data collected for the Hidden Valley project span several years. Much of this data has been submitted to the Papa New Guinea government Department of Environment and Conservation (DEC) as part of the environmental-impact statement (EIS). The environmental permit for the Hidden Valley project was granted by the DEC on the basis of this EIS. The environmental management plan for the project was then prepared in consultation with the DEC, using information from the EIS.

Harmony CEO for South-East Asia Johannes Van Heerden notes that environmental monitoring will be completed during construction, operation and postclosure. He says that data collected during each phase of mine development will be compared with baseline data, and submitted to the DEC in the form of quarterly and annual monitoring reports.

Van Heerden says that waste rock characterisation, which entails classification of material into various rock types, based on the rock’s potential to generate acid when exposed to air and water, is the key to effective environmental management. The main rock types at Hidden Valley, he notes, are granodiorite and metasediment. The granodiorite is nonacid forming (NAF), containing carbonates which are alkaline, which have the capacity to neutralise acid generated by other rock types.

The metasediment, however, has the capacity to generate acid and is classified as potentially acid forming (PAF), Van Heerden says. He adds that test work carried out over the last four years indicates that when the PAF metasediment is placed with the NAF granodiorite in the waste dump, the neutralising capacity of the granodiorite will prevent any acid being formed and released to the environment. As such, he notes, the characterisation and careful blending of waste rock combined with the management of water inflows form the basis of a strategy to prevent acid rock drainage from waste dumps.

He says that a document outlining this strategy has been submitted to the DEC, and water samples will be collected at the edge of waste dumps to ensure the strategy is effectively protecting the surrounding environment.

Harmony is efficiently making use of natural resources during the project. Water is recycled back to the process plant whenever possible and used in accordance with the environment permit. Power use will be hooked into the national government grid, which is generated through hydropower, and diesel generators will only be used as backup.

Van Heerden says that the Hidden Valley supply department records all other use of fuel and energy, and information for 2007 has been made available to the carbon disclosure projet (CDP). All the mining equipment deployed at Hidden Valley has been bought as new, and incorporates the latest technology to ensure optimum fuel efficiency, he notes.

Harmony has provided a report on its green- house emissions to the CPD. Van Heerden says that this will quantify use at the onset of production, and provide a benchmark against which the impact of energy efficiency initiatives will be measured. Hidden Valley, he adds, will strive to constantly improve its performance and reduce greenhouse-gas emissions over the life of the mine.

Annual report

Integrated annual report 2016
Integrated annual report 2016

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Investor brief

Harmony Investor brief, Sep 2017
September 2017 -
Harmony Investor brief

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