Integrated
Annual Report
2018
2018
Currently viewing: Waste and tailings / Next: Mine closure
The most significant waste materials produced by our operations are tailings, waste rock, chemical waste and hydrocarbon waste. By managing these wastes responsibly, we minimise the environmental and potential social impact, so as to maintain our licence to operate.
All of our operations have tailings management plans in place, including closure and post-closure management plans. In total, as at end-2018, our ten operations (including three JV sites) contained 33 tailings dams, of which 14 were active and one under construction. With regards to active TSFs, Gold Fields currently has two in-pit tailings dams operating at Agnew and St Ives, five downstreams/centreline tailings dams and seven upstream tailings dams. Gold Fields operations with active downstreams/centreline tailings dams are Cerro Corona, Damang and Tarkwa.
The new Gruyere TSF, currently in construction, is also a downstream TSF. Gold Fields has only three operations where upstream tailings are being used, being South Deep, Tarkwa and Granny Smith.
As two of our sites, South Deep and Granny Smith, are located in relatively dry regions, limited amounts of water need to be stored on the facilities, significantly reducing the risk of saturation on the dams. Tarkwa’s upstream tailings dams in Ghana have been constructed from imported fill materials, and are designed assuming worst-case scenario conditions, to ensure the embankments remain stable throughout both the wet and dry seasons, and also for the life of the facility.
The mining industry’s TSFs are in the spotlight following the catastrophic tailings failure at Vale’s Feijão iron ore mine in Brumadinho, Brazil, in January 2019, which resulted in over 300 deaths. This follows the 19 fatalities during the Samarco TSF failure in 2015, and significant environmental damage after the Mt Polley tailings dam collapse in 2014.
After the Samarco accident, the ICMM members developed a Tailings Position Statement in 2016 and approved a tailings aspirational goals roadmap in late 2018. Gold Fields’ Group Tailings Management Guidelines are aligned to the ICMM Tailings Position Statement. The guidelines were strengthened during 2017 with the inclusion of additional performance guidance and minimum assessment criteria. Subsequent to the Brumadinho tragedy, the ICMM agreed to establish an independent panel of experts to develop an international standard for tailings facilities for its member companies.
All Gold Fields’ TSFs, as well as associated pipeline and pumping infrastructure, are subject to an independent, external audit every three years – or more frequently where required by local circumstances or regulations – as well as regular inspections and formal annual Engineer of Record reviews.
A number of improvement areas were recommended, including:
In addition to closing out these identified gaps during 2018, Gold Fields also embarked on a programme to further improve operational safety of its TSFs, including moving away from the construction of upstream facilities to centre-line or downstream designs, consideration of filtered and dry stacked tailings, as well as in-pit tailings disposal.
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Source: Jon Engels www.tailings.info/disposal/conventional.htm |
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The two most common designs for a raised tailings embankments are upstream and downstream TSFs. A downstream tailings facility is one where the new embankment raise is constructed and supported beyond the downstream slope. Downstream TSFs may have supernatant water ponded against the embankment, as shown in the diagram, or they may have a tailings beach. In upstream tailings dams, each new embankment raise is constructed partially on the embankment immediately below and partially on the consolidated tailings beach adjacent to the embankment. |
These are in line with the main areas of work under the ICMM's aspirational goals: improving critical controls and reducing tailings water content.
The following actions have been implemented or are currently in process at our operations:
In February 2019, the Gold Fields Board also requested strengthened governance of the Group's TSFs through among others, quarterly TSF update reports, continuous environmental monitoring, including satellite monitoring scans, and increased external and independent verification. These are currently being investigated by management with a view to rapid implementation.
Gold Fields is also working with Lepanto Mining, its majority partner in the Far Southeast project in the Philippines, on enhancing risk mitigating measures for the TSF used by Lepanto for tailings disposal from its nearby gold mine. Gold Fields and Lepanto have commissioned external consultants to undertake detailed hydrological, seismic and geotechnical reviews and make recommendations on strengthening the TSF. The TSF is located in a region with high seismic activity and frequent typhoons.
Our technical teams are also working with Asanko Gold to further strengthen risk assessment and governance of the lined and downstream-designed TSF at the Asanko gold mine (AGM) JV in Ghana.
During 2018, two new TSFs were commissioned at our West African operations: the FETSF at the Damang mine and TSF 5 at Tarkwa.
Total Group waste rock volumes mined decreased to 149Mt in 2018 from 171Mt in 2017, due to lower volumes moved at our Tarkwa and St Ives mines. Tailings depositions were at 41Mt in 2018, unchanged from 2017 and despite a sharp fall in depositions at South Deep, due to lower production.
Gold Fields has set a target to maintain the general landfill waste mass (non-hazardous waste other than tailings and waste rock) at 2015 levels of 11.2Mt, by ensuring a reduction in the waste that reaches landfill through greater use of on-site waste separation and recycling. During 2018 the Group reduced landfill waste by 19% to 9Mt as a result of lower waste volumes at Damang, Cerro Corona and St Ives.
The Far East Tailings Storage Facility (TSF) at our Damang mine in Ghana