Cyanide and waste management
Located 55km south of Laverton, the Sunrise Dam Gold Mine has two waste dumps, Cleo and Sunrise, both constructed out of waste rock generated from open pit mining operations.
See case study: Australasia – Cleo and Sunrise rock!
The management of cyanide and waste generated during the gold production process remains an important consideration for AngloGold Ashanti. It is also a critical issue for NGOs and other stakeholders.
Cyanide is used to efficiently and cost-effectively extract gold from its host ore. It is estimated that, of the approximately 1.1 Mt of hydrogen cyanide produced annually worldwide, only 6% is used to produce cyanide reagents for gold processing.
The responsible use of cyanide is as integral a part of our ‘licence to operate’ as the systems and processes associated with the planning, management and monitoring of our environmental performance. Compliance with the International Cyanide Management Code (Cyanide Code), along with rigorous reporting, is central to this.
Our Chemical and Waste Management Standards address the management of risks arising from the use of hazardous materials, including the waste mitigation hierarchy of avoiding, reducing, reusing, recycling, treating and disposing of waste.
Like other mining companies, we generate waste rock and tailings* as a result of our mining and processing operations. During open-pit mining, large volumes of soil and/or rock (called overburden) are generated to expose the orebody.
Similarly, waste rock is generated during drilling and developing access to underground orebodies. Overburden and waste rock typically contain sub-economic levels of gold and are deposited as large waste rock dumps.
The impact of failure of a tailings storage facility (TSF) can be significant. We, therefore, monitor these facilities closely and ensure their management is in accordance with our permits, national regulating requirements, our internal tailings management framework and agreements we may have with communities.
- * Tailings are the fine process effluents that are deposited in the form of a slurry in tailings storage facilities (TSFs), that have been specifically designed for this purpose.
What we said we would do
In 2011 we committed to:
- maintaining our certification of compliance to the cyanide code of the 16 operations that were certified by the end of 2011; and
- the registration of four additional sites (Iduapriem and Obuasi in Ghana, Córrego do Sítio Sulphide plant in Brazil; and Geita in Tanzania) with the International Cyanide Management Institute (ICMI), confirming their intention to seek certification within a three-year window period.
Our performance in 2012
At the end of 2012, 16 of our plants had achieved and/or retained Cyanide Code certification. A further three plants are in the process of seeking certification and the remaining two plants, newly acquired in 2012, will be embarking on the certification process in 2013. The following operations were re-certified for three years during the year: Serra Grande; Queiroz Gold Plant; Córrego do Sítio Oxide Plant; Yatela (recertification announced in early 2013) and Sadiola (recertification announcement pending at time of printing).
Good progress was made by all four as-yet-unaudited operations in the implementation of the Code, although they were unfortunately not registered with the ICMI during 2012. However they, and the newly acquired Mine Waste Solutions, were registered in early 2013 and it is expected that these five operations will achieve compliance and certification by 2016.
In total, the group used 26.324t of cyanide in 2012 (2011: 23.918t). There were no reportable incidents relating to cyanide during the year.
Cyanide destruction technology is being installed at the Iduapriem mine in Ghana to reduce the weak-acid dissociable (WAD) cyanide on the tailings facility, and will be commissioned in 2013. The construction of replacement cyanide handling facilities at the Obuasi mine in Ghana was completed in late 2012, with commissioning planned for in early 2013. Both installations will facilitate compliance by these operations with the Cyanide Code.
Key performance indicators
- (1) Represents the group’s attributable share
About the Cyanide Code
The Cyanide Code is a voluntary initiative for the gold mining industry and the producers and transporters of the cyanide used in gold mining. The Code was developed for gold mining operations, and addresses production, transport, storage, and use of cyanide and the decommissioning of cyanide facilities. It includes requirements related to financial assurance, accident prevention, emergency response, training, public reporting, stakeholder involvement and verification procedures. See www.cyanidecode.org.
Materials used by volume (EN1)
|Ore processed (000t)||2012||2011|
|Mine Waste Solutions||7,184||–|
|Non-renewable process materials||Liquid fossil fuels
|Lubricants (Million litres)|
|Mine Waste Solutions||–||–||16||–|
|Renewable process materials (t)||Cyanide||Explosives||Total acid consumption||Total alkali consumption|
|Mine Waste Solutions||2,152||–||–||–||633||–||4,843||–|
NOx, SOx, and other significant air emissions by type and weight (EN20)
|Oxides of nitrogen (t)||Oxides of sulphur (t)|
|Mine Waste Solutions||0||0||0||0|
Water discharges by quality and destination (EN21) RA
|Sunrise Dam||A volume of 1,196,882kl of the excess open pit and underground water was discharged to Lake Carey discharge at an average pH of 7.60 and a conductivity of 210mS/cm.|
|AGA Brazil||A volume of 12,996,000kl of excess effluent water was released from the Queiroz metallurgical facility to the Velhas River following arsenic precipitation and pH correction, at an average pH of 7.3 and an average conductivity of 0.19mS/cm.|
|AGA Brazil||A volume of 457,035kl of excess mine water was released from the Cuiabá Mine to the Sabará river after pH adjustment with an average pH of 7.8 and an average conductivity of 0.11mS/cm.|
|A volume of 362,049kl of excess mine water was released from the Lamego mine to the Papa Farinha creek after flocculation for solids precipitation, with an average pH of 7.8 and an average conductivity of 0.07mS/cm.|
|A volume of 619,160kl of excess mine water was released from the Córrego do Sítio mine to the Conceição River after flocculation for solids precipitation, with an average pH of 7.8 and an average conductivity of 0.05mS/cm.|
|A volume of 1,900,800kl of excess water effluent was released from the Córrego do Sítio II mine via the effluent canal to the Conceição River after arsenic precipitation and pH adjustment with an average pH of 7.8 and an average conductivity of 0.43mS/cm.|
|Serra Grande||A volume of 708,480kl was released from the Serra Grande effluent treatment plant after arsenic precipitation and CN destruction Almas stream tributary of the Rio Vermelho with a pH of 7.5 and a conductivity of 0.816mS/cm.|
|A volume of 578,800kl of the New Mine effluent was pumped to the Rio Vermelho after solids precipitation, with an average pH of 7.7 and a conductivity of 0.64mS/cm.|
|A volume of 492,480kl of the Palmeiras Mine effluent was pumped to the Gerais Stream tributary of the Rio Vermelho after solids precipitation, with an average pH of 7.8 and a conductivity of 0.455mS/cm.|
|Iduapriem||A volume of 1,451,657kl of excess process water was discharged to the environment after salinity reduction by reverse osmosis, with an average pH of 7.9 and an average conductivity of 1.11mS/cm.|
|Obuasi||A volume of 433,284kl of process water was discharged to the Nyam Stream after heavy metals removal by reverse osmosis, with an average pH of 7.20 and an average conductivity of 0.04mS/cm.|
|A volume of 373,723kl of process water was discharged to the Kwabrafo Stream after heavy metals removal by reverse osmosis, with an average pH of 7.50 and an average conductivity of 1.28mS/cm.|
|Vaal River||A volume of 3,207kl of seepage water was discharged to the Vaal River with an average pH of 7.66 and an average conductivity of 2.99mS/cm.|
|West Wits||A volume of 632,157kl of purified sewage effluent was released from the aquatic system to the Elanfonteinspruit with an average pH of 7.78 and an average conductivity of 0.55mS/cm.|
|A volume of 207,727kl of purified sewage effluent was released to the Wonderfonteinspruit via the Blyvooruitzicht canal with an average pH of 8.00 and an average conductivity of 0.66mS/cm.|
Hazardous and non-hazardous waste (EN22) RA
Hazardous waste disposed of by the company primarily includes battery waste, chemical and solvent waste, fluorescent lighting waste, and hydrocarbon waste.
|Total hazardous waste by type||Battery Waste
|Total in 2012||10||69||8||1,200||8,600|
|Total in 2011 *||36||23||13||1,400||21,000|
- *West Wits is not reported in 2011
Non-hazardous waste disposed of by the company includes ferrous metal waste, non-ferrous metals waste and general waste.
|Total non-hazardous waste by type (t)||Ferrous metal waste||Non-ferrous metal waste||General waste|
|Total in 2012||19,400||320||45,000|
|Total in 2011||19,900||880||41,000|
Total amounts of overburden, rock, tailings, and sludges and their associated risks (MM3)
Waste materials are produced during the mining cycle. Internal Tailings and Heap Leach Management Frameworks set the standard as well as provide guidance to which tailings and heap leach facilities must be constructed and operated. Internal geotechnical engineers are responsible for ensuring the structural stability of tailings, heap leach facilities and waste rock dumps.
During the design phase, appropriate handling and placement considerations have to be factored into the project design to ensure satisfactory protection of the environment and the safety of neighbouring communities. Risk assessments, environmental impact assessments, stakeholder engagement processes and other studies are used to identify appropriate mitigation measures and controls. During the operational phase, monitoring and audit processes are used to establish trends, identify emerging issues and to ensure conformance to the defined standard operating procedures and operating licence requirements for these various facilities, for example stability assessments, water quality and dust monitoring, hydrogeological and geochemical modelling etc., are carried out to monitor the effectiveness of the design and controls.
Closure considerations are generally broad at the design phase, continually revised throughout and finalised during the operational phase. These activities are then implemented during the closure phase (with appropriate post-closure monitoring).
IR See more information on closure planning and rehabilitation liabilities and provisions.
The following data is presented for the first time for the 2012 financial year. LA
waste rock placed
- *0.025 Mt sludge containing precipitated arsenic was disposed of to a fully lined landfill by our Brazilian operations.
Significant environmental incidents (EN23)
|Operation||Date||Incident description||Corrective actions undertaken|
|Sunrise Dam||11 January||A total power outage in the process plant during inclement weather caused slurry in the circuit to over-top in two places with the existing bunding inadequate to contain a total slurry spill >5,000 m³. This was a breach in a licence condition and the 24 hour notification requirement to regulator was not met.||
|Iduapriem||14 June||High rainfall resulted in runoff from the Block 1 TSF and the Greenfields TSF (2 incidents) that had total suspended solids and turbidity above the Ghana water discharge limits. Geofabric material of 44 microns at Block 1 TSF could not clarify storm water runoff to the discharge standard.||Block 1 TSF:
|Obuasi||22 December||The pipeline transferring tailings slurry from the processing plant to the TSF was vandalised by unknown parties. It was estimated that about 260m³ of the tailings material spilled to the environment resulting in two monitoring points on the Nyam river system temporarily recording elevated levels of cyanide.||
|Sadiola||27 November||Untreated sewage water was found flowing from a collector located inside the mine village. The flow was circulated into a seasonal stream that joined the communal water course. Following the investigation, it was found that kitchen waste and tree roots were blocking the sewage system.||Additional collectors were built up on the sewage water reticulation and trees and solid debris were removed along the piping network. A sensitisation campaign was scheduled to enhance domestic workers’ knowledge of the sewage system.|
|Geita||1 January||A vegetation clearance permit was issued to clear an area of 13,249m² at Nyamonge-Tango. Although the survey department marked the boundary of the area to be cleared, a reconciliation at the end of the exercise revealed that there had been over-clearance of vegetation of about 7,660m² by the contractor.||
|Mine Waste Solutions (MWS)||29 October||The stormwater system at Harties 1 and 2 Tailings Reclamation Site overflowed and spilled onto the adjacent farmland. The incident resulted in a complaint from the landowner.||Work commenced on the containment constraints soon after acquisition in July 2012:
|30 October||Overflow of storm water at Kareerand TSF storm water containment facility after a significant rainfall event.||Clean and dirty water separation mechanisms are being reviewed. Most of the water that flowed into the return water dam originated from areas adjacent to the TSF. Additional stormwater diversion and containment is being reviewed as part of phase 2 of the project.|
|15 November||A National Nuclear Regulator (NNR) inspector noted during a routine compliance inspection that MWS had commenced with reclamation of the Hartebeestfontein TSF, and associated deposition on the Kareerand TSF, despite two previous directives not to commence with operations pending approval of a number of regulatory submissions. The MWS management team was not aware of either of the directives as these had not been disclosed to AngloGold Ashanti by the previous management team.||A task team was appointed to reconcile any previous and current outstanding issues and actions pertaining to the MWS Certificate of Registration. A proper issue trail was established and necessary documentation was reviewed and resubmitted for approval to the NNR within days of the stoppage. The NNR approved all submissions and lifted the directive on 23 November. Major changes have been made to the operational and environmental staffing structures at MWS.|
|3 December||The stormwater system at Harties 1 and 2 Tailings Reclamation Site overflowed and spilled onto adjacent farmland. The incident resulted in a complaint from the landowner. The incident was aggravated by a power failure owing to inclement weather.||See actions stated above under the incident of 29 October.|
|3 December||Midway Process Water Balancing Dam overflowed and spilled onto adjacent farmland. The incident resulted in a complaint from the landowner. The incident occurred due to a power failure and associated water level control instrumentation malfunction.||An investigation was undertaken regarding the level control instrumentation at Midway Dam. Plans were initiated to upgrade the instrumentation system.|
|11 December||Midway Process Water Balancing Dam overflowed and spilled onto adjacent farmland. The incident resulted in a complaint from the land owner. The incident occurred due to a power failure and associated water level control instrumentation malfunction.||In addition to the planned instrumentation upgrade identified during the incident on 3 December, additional physical operator inspection and communication protocols were established.|
|25 December||The stormwater system at MWS Harties 1 and 2 Tailings Reclamation Site overflowed and spilled onto adjacent farmland. The incident resulted in a complaint from the landowner. The incident followed a rainfall event of approximately 50mm in less than an hour, breaching and damaging existing bund walls around the Harties TSF pump station.||In addition to the corrective actions stated above under the incident of 29 October, the damaged containment walls were immediately repaired, the sumps were cleaned and damaged pumps replaced.|
|Vaal River||6 August||A pipeline failure occurred on the return water penstock line of West Extension TSF. An estimated 3,000m³ of return water from the TSF was spilled into the environment.||The original polyvinyl chloride pipe was replaced with a steel pipeline. The maintenance plan for gravitationally fed pipelines was reviewed.|
|2 September||A pipeline failure occurred on the residue line from East Gold Plant to Compartment 4. Due to a delay in shutting down the pipeline, the resultant spillage covered an area just exceeding 1ha. The spill occurred in a previously impacted area directly adjacent to the TSF.||Independent thickness testing was immediately conducted on Compartment 4 line. Potentially high risk pipes were identified and will be replaced as matter of priority. This also includes the replacement of 16 Bar valves with 25 Bar valves. Metallurgy to review its overall pipeline management strategy.|
|29 October||After several rainstorm events, the Mispah TSF overflowed.||The maximum volume of process water possible was diverted to other containment facilities to minimise the overflow. An adequate stormwater dam is planned to be constructed in 2017. Interim measures to contain more stormwater on Mispah TSF are also being investigated.|