Environmental & natural resource management
The information below provides disclosure under the Global Reporting Initiative (GRI) indicator EN23: Total number and volume of significant spills
Refer to the discussion of reportable environmental incidents in this section for all reportable environmental incidents in AngloGold Ashanti during 2011, including significant spills.
EN28: Monetary value of significant fines and total number of non-monetary sanctions for non-compliance with environmental laws and regulations
No fines or non-monetary sanctions for non-compliance with environmental laws and regulations were reported that were material (above the stipulated threshold).
The following table gives details of reportable environmental incidents occurring during 2011.
|Date||Incident Description||Corrective Action|
|Ghana: Obuasi mine|
|Late Q4 2010 to mid Q1 2011.||Release of Adansi shaft water to the environment after closure of the Tailings Treatment Plant (TTP) in November 2010 at a relatively consistent basis with water quality parameters in excess of Ghana EPA thresholds.||The water balance was submitted to EPA, as part of the Environmental Management Plan, in January 2011 and a process was put in place to permanently redirect this water to the South Treatment Plant by June 2011 with an interim contingency plan of directing the water for treatment in the Actiflo units installed at the PTP sump, ahead of release to the environment.|
|February – May (10 discrete events)||
On detailed review of analysis results over Q1 and Q2, the backfill sent underground for support was found to contain levels of cyanide above the Ghana EPA guideline value of 0.2 ppm.
The causes were found to be occasional leakage of cyanide-containing tailings directly to the non-cyanide tailings stream used for backfill preparation and inadequate operation of ferrous sulphate dosing system, used to destroy residual cyanide.
Piping changes were undertaken to ensure mixing of different tailings streams is avoided and additional operating controls and checks were put in place, including daily reporting of backfill preparation parameters.
|26 May to 21 June||Intermittent exceedances of the EPA’s effluent water guidelines from the excess process water treatment circuit installed at the Pompora water treatment circuit to batch treat the excess Adansi shaft water whilst a permanent redirect water to the operating circuit at the South Treatment plant.||A 2km pipeline to re-route the Adansi shaft water to the South Processing Plant commenced commissioning on 28 June.|
|14 June 2011||An articulated truck carrying hydrogen peroxide from Obuasi mine to Iduapriem mine was involved in an accident at Assin Bireku. About 8 drums (8,250 litres) out of 34 drums (34,000 litres) of peroxide were spilled. The emergency response time was 4 hours.||
The truck was retrieved and the hydrogen peroxide neutralized. Environmental monitoring was conducted to determine the extent of impact.
Results showed values below Ghana EPA guideline for mine effluent. 3rd party monitoring of water and soil was also undertaken by the Council for Scientific and Industrial Research to confirm the mine’s analyses.
|29 December 2011||Discharge of inadequately treated process waster effluent from the rotating biological contactors (RBCs) and Actiflo water treatment plants into Pond 3 (a large process water storage pond) resulted in elevated cyanide concentrations, killing about numerous amount of fish that inhabit the process water pond.||
Regular calibration of the Cyanoprobe online analyser.
Regular monitoring (online and manually) of cyanide levels of inflow and outflow water in the water treatment plants.
Volume of water treated in dry seasons should be reduced significantly to ensure steady running of the water treatment plants.
|South Africa: (West Wits and Vaal River)|
|24 December 2010 (reported during Q1)||The Vaal River Mispah storm water dam overflowed on 24 December 2010 after 34mm of overnight rain fell in the catchment area. Approximately 3 000 m3 of process water spilled into the surrounding area.||
Removal of operational restrictions in the pipeline. Target date April 2011.
Optimise use of return water from Mispah RWD to displace river and potable water use (ongoing).
Commission construction of additional storm water capacity. Target date December 2013.
|3 January 2011||Owing to excessive rainfall in the West Wits area over the December 2010 period and the dam already being full, there was an overflow from the North Boundary Dam into the Wonderfonteinspruit on the morning of the 3 January 2011.||
North Boundary Dam under construction (>90% complete).
Delays resulted from heavy rainfall events.
|25 January 2011||The process water line from Bokkamp to Central Spillage at Vaal River sprung a leak spilling approximately 6 000m3 of process water into the veldt.||
The pipeline immediately repaired upon discovery of leakage.
An investigation was undertaken to identify weakened sections of the pipeline for replacement during in 2012.
|24 January, 19 February, 16 April, 8 June, 13 July, 27 July, 29 July and 1 August (8 events).||The Vaal River Mispah Water Dam overflowed on 8 separate occasions between January and August 2011. This was predominantly owing to rainfall events in excess of 30mm. From late July an additional contribution to the overflows in additional to some unseasonal rainfall, was the wage negotiation strike which necessitated the shutdown of the metallurgical plants. During this time water could not be returned to the processing circuit.||
Detailed mitigation actions on Mispah Dam are specified in the incident dated 24 December 2011 above and in addition;
Maximise the use of return water from Mispah RWD to displace river and potable water use (ongoing).
Feasibility of additional storm water capacity to be concluded in 2012, with envisaged construction in 2013.
Reconsidered the tailings deposition strategy – deposition onto West TSF to reduce the pressure on Mispah TSF.
Review water handling capacity and operational flexibility during extended work stoppages.
|28 August 2011||The residue pipeline from the West Wits Mponeng Gold Plant to the Mponeng TSF failed, resulting in a spillage into the veld and into the Aquatic dam.||
Immediate actions included construction of earth berms below the failure point to minimise the flow to the Aquatic dam.
Daily water samples were taken in the two weeks following the incident during clean-up activities to verify downstream compliance.
The Department of Water Affairs was notified. The affected section of the tailings pipeline was replaced within 24 hours of the incident.
A broader re-evaluation of tailings pipelines was initiated.
|Australia: Sunrise Dam GM|
|22 February 2011||Following excessive rainfall runoff from the upstream catchment the tailings containment bund was washed away and the tailings line was breached as a result of excessive pressure on the poly welds. The estimated released tails slurry volume of 866m3 inundated a previously undisturbed area of approximately 2.5 Ha.||
The plant was shut down immediately and the line was repaired after the rain abated. The incident was reported to the Government agency.