Commonwealth of Australia 2010
Release via sewerage plant effluent
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- 22.3Release as a result of unintentional incidents
- 22.3.1Manufacturing facilities
- 22.3.3Use and disposal at gold or other mineral processing facilities
- Romania/Baia Mare Mine incident
- Incidents occurring during use at ore processing sites
- Tailings storage facilities (TSFs)
- Breach of tailings cyanide discharge limits
- Inappropriate disposal of sodium cyanide
22.2Release via sewerage plant effluentAs noted earlier (Section 14.1.1), electroplating and heat treatment facilities account for the majority of influent containing residues from sodium cyanide into WWTPs in the USA. Uses of various other forms of cyanide (i.e. inorganic salts and complexes other than sodium cyanide) may also lead to some release of cyanide to the sewer and may be more significant contributors than sodium cyanide uses, given the requirements for destruction and/or disposal of residues from the use of sodium cyanide for purposes such as electroplating (Section 19.1.2). Data from Sydney Water (2005) where cyanide concentrations in sewerage discharge effluent were measured over a number of years are available for 17 locations around the Sydney Metropolitan area, including 15 discharge points to rivers and streams, and 2 ocean discharge points. Changes in the form of cyanide present and/or removal presumably occurred during sewerage treatment. All the discharges occurred after tertiary sewerage treatment, with the exception of one of the inland discharges and the Warriewood ocean discharge (both secondary treatment). A number of exceedences of the 10 times detection limit threshold (i.e. 10 X 1 µg CN/L) for total inorganic cyanide were detected in 2001-02, but these were attributed to inter-laboratory problems with the analytical method then in use (Independent Pricing and Regulatory Tribunal, 2003). Due to this unreliability, NSW Water Corporation reverted from a micro-distillation method to standard APHA (1998) methods (APHA 20th ed. 4500 CN- – C & N) for total CN in water and wastewater. In both 2002-03 and 2003-04, median total CN concentrations for all the measured discharge points were <5 µg total CN/L, with median values at river/stream discharge sites generally 1 µg total CN/L (4 sites had median values of 1.5-5 µg total CN/L in 2002-03). At inland sites, individual maximum values recorded in those two years were generally <5 µg total CN/L, though they sometimes reached 5-10 µg total CN/L. Peak concentrations at Cronulla and Warriewood were 20 µg total CN/L and 108 µg total CN/L, respectively, in 2002-2003, and <5 µg total CN/L and 19 µg total CN/L in 2003-2004. These data indicate that controls on use for various forms of cyanide together with removal in the sewerage treatment process (Section 26.3) are adequately limiting total cyanide concentrations in water at the point of release, where further dilution can be expected to ensure concentrations in receiving waters are below ANZECC Guideline trigger values of 7 µg CN/L for inland waters and 4 µg CN/L for marine waters (Sections 55.1.2).
22.3.2TransportationThere are potentially serious consequences of accidents occurring during the transport of sodium cyanide, as evident in the following reports. Information of the causes of such accidents and the adequacy of measures taken to clean up spills and minimise environmental harm after an accident has occurred is useful to guide the future management of risks associated with cyanide transport. Cyanide transportation incidents which have been reported by Mudder and Botz (2001), newspapers or various websites are summarised in Table 5. (claimed human impacts have not been presented). No reports of incidents occurring during storage or handling prior to delivery to minesites were encountered, with the exception of the incident listed for New Zealand in 2004, which was very minor from an environmental perspective. Several transport incidents which have occurred in Australia are listed in Table 5.2. The number of incidents is small compared to the large number of journeys in that period over long distances by road and rail. Significant release of NaCN only occurred in three of the incidents listed: a truck accident in the NT in 2007, release of NaCN in solution in an incident in the Tanami Desert in 2002, and a train derailment near Condobolin in 1992. Only in the Tanami Desert incident were wildlife or aquatic life reported to have been affected by the release to the environment, due to prompt emergency response measures on the other occasions to contain and recover the spilt material and remove contaminated soil or water. In the 2007 truck accident and 1992 train derailment the NaCN was packed in CIBCs in a shipping container and release occurred after upheaval of the containers in high energy incidents. In the Tanami Desert incident liquid was released from a StoL container en route. Further details of the Northern Territory truck accident and Tanami Desert incident are given below. Also listed are various transport incidents which have occurred overseas, some of which have involved significant release of NaCN, downstream environmental contamination and harm to aquatic organisms. Details for one of the major overseas incidents (in Kyrgyzstan) are also discussed further below. Northern Territory truck accident On 7 February 2007, two shipping containers of a three-container load of solid NaCN (pellets) tipped over in a road traffic accident, spilling their contents onto the side of the road and into a pond in a non-flowing watercourse (sources: various news reports; NRETA, 2007; NT Government, 2007; NT PFES, 2007). The NaCN was loaded in 1 tonne CIBCs in shipping containers each holding 20 CIBCs, which were carried on a road train with 3 trailers. NaCN was in direct contact with the ground and an amount had also gone into the watercourse. The product was en route from the Orica manufacturing plant in Gladstone to a Northern Territory mine, and the manufacturer was promptly involved to assist local agencies with the emergency response. An earthen bund was placed on the upstream side of the spill to prevent water flowing into the spill as a result of rain, and sandbagging and earthen bunds were used to prevent any spread of liquid from the containment area. This minimised the risk of further environmental contamination over the period of 9 days before the recovery and clean-up operation was completed and the highway was re-opened to traffic. The contents of the 3 containers were fully salvaged without loss of product except for approximately half the contents of one container. Small amounts of sodium hydroxide solution were added to minimise HCN fuming from the pond during the recovery by keeping the water pH alkaline. The area was constantly monitored during the recovery period to prevent access by animals or humans. Equipment was washed down to decontaminate it before being taken away from the scene. Contaminated water (120 000 L) and soil (1000 m3) were collected and disposed of at operating and closed mine sites. After testing had been conducted to confirm that the area had been decontaminated, it was indicated that the area would be remediated to restore it to a condition similar to its original condition. An investigation conducted by NT Worksafe concluded that the transport, packaging, placarding (signage) and licensing of both the transport and driver complied with the legislation at the time of the accident (NT DEET, 2007). In response to this incident, the NT Government initiated a review of regulatory regimes governing the transport of dangerous goods in the Northern Territory (NT Government, 2007). Specific objectives were to identify ‘weaknesses in the regulatory regimes which may increase the risks associated with the transport of dangerous goods in the NT, and strategies which would help address any identified weaknesses and thereby reduce the risks.’ The scope of the review included various categories of dangerous goods, the nature of transport activity, classes of dangerous goods transported, quantity transported and transport modes used, considering both road and rail transport. Consideration of the regulatory regime encompassed elements of Federal, NT and other State legislation ranging from current and proposed Acts, Regulations and Codes, to compliance monitoring, enforcement, accident response, and training. Thus the review extended well beyond environmental safety issues with the transport of sodium cyanide. The review report is not yet a public document, but NT WorkSafe advise that the key recommendations from that review were being actioned, including the adoption of the 7th Edition of the Australian Dangerous Goods Code (ADG7) and improvements to coordination across Government agencies, both for compliance monitoring arrangements and for emergency response procedures. All jurisdictions, including the NT, have either legislated already for the adoption of ADG7 or aim to legislate by the end of 2009. By 1 January 2010 all transport of dangerous goods across state borders, and within most states, will be required to fully comply with ADG7. NT WorkSafe also indicate that the principal transporters of sodium cyanide in Australia no longer use triple road-trains for the transport of solid sodium cyanide in containers. The mode of road transport used currently is either double road-trains with end-loading containers or road-trains with tank containers on drop decks. Tank containers are transported as triples. They note that both of these configurations would be considered lower risk than the configuration used at the time of the 2007 accident. Tanami Desert incident Cyanide poisoning resulting in mortality to wildlife (birds, kangaroos, dingo) followed a leakage incident during road transportation of liquefied sodium cyanide in the Northern Territory in February 2002 (DEET, 2002). An estimated 3000-6000 L of water containing free CN was discharged along the Tanami Highway, forming a pool confined to the spoon drain alongside the highway from which the animals drank. Tests found that the concentration of cyanide in the puddle contained 863 mg/L of cyanide, but sampling and analytical details were not available to confirm these results or the concentration variability. It was suspected that this occurred from a delivery truck returning from The Granites site to Alice Springs, and that due to a hose, pump or procedural failure, the cyanide in the isotainer had not been completely removed during the StoL (solid to liquid) process at the mine. The incident caused a number of fauna deaths (reports vary, but the most detailed seen indicated ~800 Zebra Finches, 30 pigeons/doves, 2 Black Kites, 10 Singing Honeyeaters, 10 Fairy Martins, 1 Spotted Nightjar, 15 Budgerigars and 1 dingo died). However, there was no apparent effect on local vegetation. An extensive clean-up & remediation operation was conducted by the mine’s emergency response team. Initial detoxification was undertaken by spreading calcium hypochlorite, and the water and top 0.5 m of soil were removed and sent back to the gold mine for disposal onto the tailings storage facility, with further hypochlorite neutralisation. The reporting and investigation of the cyanide incident was delayed due to the lack of clear procedures and strategies to deal with a major release of dangerous goods in the Northern Territory. Recommendations arising from the incident investigation were directed towards product inventory management at the mine, improvements to the StoL emptying process, locking of input and outlet valves on isotainers, driver training in dangerous good management and better government departmental co-ordination of chemical spill incidents. Barskoon River incident in Kyrgyzstan In 1998, approximately 1700-1800 kg NaCN was lost into the pristine Barskoon River in Kyrgyzstan as a result of a truck accident while en route to a nearby gold mine. Several domestic animals and some river trout were stated to have died as a result. There were serious impacts on the local community (local concerns reaching such an extent that the area was evacuated ~2 weeks after the incident occurred, well after the cyanide in the river had dissipated to safe levels), as discussed by Hynes et al. (1998) and Cleven and van Bruggen (2000). On the day of the incident, efforts were made to assist decomposition of the spilt cyanide using an unidentified substance, thought to be either hydrochloric acid or sodium hypochlorite. It is not clear whether or not these measures had any beneficial effects. Worst case calculations indicated that the spilt NaCN would all have dissolved within at most 17 minutes of the spill and that the contamination front would have taken at least 7-8 h to reach the lake 14 km downstream. While initial CN concentrations in the river water must have been very high, degradation, loss as HCN, movement downstream and dilution meant that there were no long-lasting effects in the river and concentrations in the lake remained below potentially harmful levels. Recommendations from Cleven and van Bruggen (2000) included guidance on safe concentrations of free cyanide for human, animal and plant life in soil (1 mg/kg), surface water (0.1 mg/L), and improved information and risk communication regarding cyanide. Table 5.. Environmental incidents that have occurred with cyanide during transport
22.3.3Use and disposal at gold or other mineral processing facilitiesInternational reports Table 5. lists brief details of environmental incidents involving cyanide that have occurred at mining operations around the world in recent decades (claimed human impacts have not been presented). Detailed, authenticated reports of incidents are often not readily obtainable, hence the table has been compiled from lists recorded by ICOLD/UNEP (2001), Mudder and Botz (2001), augmented by various other sources, including the press and internet websites. Many of the overseas incidents listed were major environmental incidents involving the release of several thousand cubic metres or more of tailings slurry or solution, with resultant impacts on humans or ecological systems, in particular aquatic life. Some relatively minor incidents have been listed for Australia. NICNAS has not investigated the regulatory control measures that were in place in the various overseas jurisdictions at the time of these overseas incidents. The dam failure incident involving the greatest release of cyanide-containing waste was at a gold mine in Guyana in 1995, which released an estimated 3.2 - 4 million cubic metres of waste. The greatest release listed for cyanide-containing waste from dam overtopping was 39 000 cubic metres in the US in 1991. Pipe failures have resulted in estimated environmental releases of up to 700 000 tonnes of cyanide-containing waste, in an incident in the Philippines in 1999 (ICOLD/UNEP, 2001; Mudder and Botz, 2001). In particular, information on ecotoxicity effects is often minimal and/or unreliable, presumably because it is difficult to judge the extent of damage caused by the specific incident in a quantitative fashion, and because where effects are not independently assessed they may be either understated or exaggerated (e.g. note the discrepancy in reports for the 1995 incident in Guyana or that at Tarkwa [Ghana]) in 2001.) Details of incidents are generally lacking or differ between reports, and a confounding factor may be confusion between different incidents. It should also be recognised that cyanide contamination may be just one of many harmful factors arising from accidental releases to the environment from ore processing sites and tailings storage facilities. Ecological damage can be expected from sudden large releases due to physical impacts, destroying and covering or washing away vegetation and streams and killing or injuring terrestrial and aquatic wildlife in the path of the release. Ecotoxicity effects may be caused in aquatic areas reached by slurry and liquid releases, through turbidity as well as various toxic components, including cyanide. Depending on the form and concentration of cyanide present, serious effects may be anticipated through acute toxicity to fish and other organisms as a contaminated front moves downstream, and these effects may be exacerbated and prolonged by the presence of other, more persistent toxins, such as heavy metals. Measures taken to destroy cyanide also have potential to have other harmful effects. Thus some care is needed in interpreting the damage reported for various incidents in Table 5.3, but it appears clear that there have been incidents of sudden or ongoing releases of material containing cyanide to streams and other aquatic areas where cyanide has contributed to serious harmful effects on fish and other aquatic organisms, and sometimes also to animals drinking the affected water. Romania/Baia Mare Mine incidentOne of the most serious incidents, for which the cause and impacts have been described in detail in BMTF (2000); Lucas (2001) and ICOLD/UNEP (2001), is the dam failure at Baia Mare in Romania. This incident involved an Australian company. Water from heavy rain and melting ice and snow caused a breach 20 to 25 m wide in a dam encircling a tailings pond, resulting in a spill of about 100 000 m3 of mud and wastewater effluent containing ~120 tonnes of CN to flow through different tributaries (minor tributaries into the Sasar, then Lapus and Somes Rivers) into the Tisza River and then into the Danube River, finally reaching the Black Sea. After several hours, the continuing discharge was treated with sodium hypochlorite to destroy the cyanide. Both this and an incident the same year at Baia Borsa, Romania not involving CN resulted from inappropriate design and construction of tailings waste storage facilities for the climatic (water balance) regime, and permitting and operational faults. A 30-40 km long contaminated wave destroyed the flora and fauna along and in the central Tisza River. Acute environmental effects occurred along long stretches of the river system, down to its confluence with the Danube. Phyto- and zooplankton levels were at zero when the CN plume passed, and fish were killed in the plume or immediately afterward. Hungarian authorities estimated >1000 tonnes of fish were killed, with dead fish reported as far as the Yugoslavian part of the Tisza, but no major fish kills reported in the Danube. Due to unaffected water flowing from upstream, plankton and aquatic organisms recovered within a few days, but long term impacts were a possibility due to heavy metal contamination also resulting from the spill. Table 5.. Environmental incidents involving cyanide at gold ore processing facilities or heap leach operations
Further US data USEPA (1997) summarised mining and mineral processing damage cases in a variety of mineral commodity sectors and states in the USA during 1990-1996 and discussed their causes and effects and the corrective or other action taken in each case. These included spills and leaks at gold beneficiation/heap leach operations using cyanide (most were relatively small scale and none have been included in Table 5.3). Most releases involving cyanide occurred through spills resulting from equipment failure or damage, failure of containment tanks or storage units, or through failure of transport devices such as pipelines, with contributing factors including operator error and freezing weather. Most such releases were in the range 100-25 000 L per event, but there were a few much larger individual spillage events (~200 000-500 000 L). Other releases were caused by unusually heavy rains and high stormwater volumes, poor infiltration into a heap leach pile, and by seepage and groundwater movement. In most cases, these spills and leaks resulted in surface soil contamination and were not reported to have caused harm to fish or other wildlife, whereas there were a few cases from other mining/mineral processing sites industries where biotic impacts such as fish kills occurred due to causes not associated with cyanide. Further Australian data A survey of all Australian state and territory mining and/or environment protection agencies (except ACT) was conducted during this assessment. Agencies were asked to provide information on cyanide-related incidents reported in the previous 3 years. Incidents occurring during use at ore processing sitesIn Western Australia in the 10 year period 1994-2003, there were ~75 incidents involving cyanide reported to the Department of Industry and Resources (WA DoIR, 2004). Most (~75%) were occupational incidents occurring at the gold ore processing (mill) area during unloading, handling, tank mixing, process operations, cleaning and maintenance or result from equipment failure (e.g. tank or pipe failure). Although many incidents involved release of cyanide solutions or vapours, these were typically only of occupational concern. Of the 75 incidents reported, ~19 (~25%) involved release or potential environmental release of cyanide solutions. Seven of the 14 incidents where environmental release did occur were at gold mill sites and included spills, leaks or tank overflows of process solutions (e.g. 20 tonne of 500 ppm), detoxified tailings or tailings slurry (e.g. 20 m3). Releases were typically contained on hard stands or in bunded areas; however, in some instances released quantities exceeded bund capacity. Five of the 14 incidents involved the rupture of tailings pipelines and subsequent environmental release of tailings (up to 90 tonnes), typically in the vicinity of TSFs. The Queensland Department of Natural Resources, Mines and Energy (DNRME, 2000) reported a gold ore processing incident involving a 200 m3 CIP leach tank failure which resulted in discharge of its contents and those of interconnected tanks to their discharge level (another 200 m3) into a bunded enclosure. Bunding could not contain the spillage, resulting in about 50 m3 of cyanide-containing (70 ppm free CN) tailings breaching the enclosure. Tailings entered an adjacent bunded elution column area where HCl acid washes occur. While most of the spillage flowed into the tailings dam, additional earth bunding was constructed to contain the spill, which was neutralised with calcium hypochlorite. The incident was caused by chemical corrosion that had weakened the tank base, allowing tailings, under a significant hydraulic head, to be forced out through the concrete pedestal. Slurry agitation with an air spear may have accelerated the erosion. Inadequacy of the bunded enclosure meant that the discharge could not be contained. The situation was made worse by beaching of the solids around the ruptured tank and within the enclosure. The landform around the plant was such that not all discharge automatically went to the tailings dam. Inadequate capacity of the bund was not identified during plant design and construction. It is possible that no consideration was made for the 'footprint' of the leach tanks in the bunded area or for the interconnection of tanks allowing contents to gravitate freely from one tank to the other. The DNRME (2000) provided recommendations to minimise the risk of future incidents occurring. Some further data were also available from individual mines, showing brief records of incidents that had occurred in the previous 3 years, usually involving tailings or solution leaks and spills. With a few exceptions, the reported incidents were generally minor in extent and/or were in areas designed to contain such spills (e.g. bunded areas and drains on site). In many cases, the risk was more to worker safety and wildlife were not actually or potentially affected. In most cases, the environment outside the facility was not exposed and the spill was collected and returned to storage or the process stream, or disposed of in the TSF. The incident reports provided indicate the nature of procedures in place for documenting incidents, identifying their cause, and where appropriate, taking action to reduce the likelihood of their recurring.
NT DBIRD indicated that there have been 2 TSF wall breakages in the history of mining in the NT, both years ago to old-fashioned, poorly constructed dams (they did not state whether CN release resulted or had any consequences). NT DBIRD also mentioned that more recently, an instance of groundwater contamination occurred in a confined aquifer when a pit was being used as a temporary TSF during a period when the operator was having trouble settling tailings out of process water. Levels of total CN were 9 mg/L, but WAD CN was only ~0.2 mg/L. The leak occurred through fractured ground and had limited movement. The then Tasmanian Department of Primary Industries and Environment (Tas DPIWE) referred to two incidents of migration of CN in groundwater and surface water in recent years. A former gold tailings re-treatment project in the North East of the state had the contents of its TSF seep to groundwater, and through the dam wall to a downstream river, due to inadequately detoxified CN and poor dam construction standards. A recent report from one gold mine indicated that monitoring had shown some movement of cyanide species and metals beyond the confines of the dam, but confined within the mining lease. However, the site’s two artificial wetland areas appeared to be reducing the concentrations of both thiocyanate and WAD CN as well as a range of other metals as surface water moves through them.
The Environment Protection Authority, Victoria (EPAV), reported an illegal disposal of a 50 L drum of NaCN dumped amongst roadside rubbish at Dandenong, Victoria, in May 2000. EPAV indicated that the cyanide had been stolen from a factory. Directory: data -> assets -> word doc -> 0017 0017 -> National Industrial Chemicals Notification and Assessment Scheme word doc -> Priority Existing Chemical word doc -> Rail safety news issue 6 – October 2011 word doc -> Review of Multiple Chemical Sensitivity: Identifying 0017 -> Rail Safety News Edition 8, December 2012 0017 -> Real-Time License Plate Localisation on fpga 0017 -> Careers network bulletin issue 6 July 16 2012 0017 -> Wiser science: Finding References inspec for Physics and Engineering 0017 -> Part A: Depth Study: The globalising world Popular culture and public policy Download 2.29 Mb. Share with your friends:
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