Cyanide Spill at Baia Mare - Assessment Mission Report UNEP/OCHA



On 30 January 2000, following a breach in the tailing dam of the Aurul SA Baia Mare Company, a major spill of cyanide-rich tailings waste was released into the river system near Baia Mare in north west Romania. The contaminant travelled via tributaries into the river Somes, Tisza and finally into the Danube before reaching the Black Sea.

A team of international experts was sent to the affected area to carry out a scientific analysis of the environmental damage caused by the spill. The mission, which lasted from 23 February – 6 March 2000, combined sampling, analysis, interviews with relevant national and local experts, discussions with national authorities, affected populations and local Non Governmental Organisations (NGOs).

Below your can read the main conclusions and recommendations from the report. The results of the assessment mission should be seen in this context,
as a starting point rather than the final conclusion. The data and conclusions will have to be refined as further study continues.


1. The uncontrolled spill of some 100,000 m³ of liquid and suspended waste occurred on 30 January 2000 at the Aurul S.A. gold and silver producing plant in Baia Mare (Romania). This spill released an estimated amount of 50-100 tonnes of cyanide, as well as heavy metals, particularly copper, into the Lapus/Somes/Tisza/Danube river catchment system.

2. The breach in the retention dam was probably caused by a combination of inherent design deficiencies in the process, unforeseen operating conditions and bad weather:- tailings dams at operating mines are under continuous construction, as solid material and effluent (plus natural inflow due to precipitation) are added. Besides safe control of pond water volume under storm runoff conditions, the safety of the dam is mainly due to a sound balance between dam height and pond water level. In the case of the new Aurul pond at Baia Mare, the flows of solids and waters were out of balance with the increase of the storage capacity of the pond, as the process of dam construction could not keep up with the rise in the reservoir water level. The climatic conditions of the winter season aggravated the situation and led to an uncontrolled rise of pond level resulting in an overflow of the dam. The company responded by repairing the breach using borrow material from nearby, and by adding sodium hypochlorite to the overflow (and to the area flooded by the spill). A large volume of heavily contaminated effluent evertheless escaped before the breach could be closed.  There were no provisions for coping with situations of a rise of pond water level due to uncontrollable input into the reservoir system.

3. The company was operating in line with Government permits. The plant was assessed as being of 'regular' risk. This was based on the description of the plant as being 'closed-loop', however the loop was open at two points – the Meda pond, and the new tailings pond – which allowed unspecified and unmonitored amounts of cyanide to be routinely lost there to air and/or groundwater.

4. No special monitoring or contingency planning at the premises of the company were required. Formal emergency preparedness and response procedures by the company and local authorities were rudimentarily considering the large quantities of hazardous materials (cyanide, hypochlorite) being used close to human populations and the river system. There appeared to be no monitoring system to detect the onset of dangerous situations. On and off site contingency plans existed but proved insufficient.

5. The company took reasonable steps to respond to the emergency. It could not be determined how often the plant had been inspected by the government authorities before the spill occurred. However, the early warning system established under the Danube River Protection Convention responded adequately to alert neighboring countries.

6. Through several small rivers in Romania, the spill entered the Tisza river which flows through Hungary and into the Federal Republic of Yugoslavia. The pollution then flowed into the river Danube upstream of Belgrade and finally entered the Black Sea. The cyanide plume was measurable at the Danube delta, four weeks later and 2000 km from the spill source.

7. The acute transboundary pollution had the potential of having a severe negative impact on biodiversity, the rivers’ ecosystems, drinking water supply and socio-economic conditions of the local population.

8. Timely information exchange and measures taken by the Romanian, Hungarian and Yugoslavian authorities, including a temporary closure of the Tisza lake dam, mitigated and reduced the risk and impact of the spill.

9. Romania, Hungary and the Federal Republic of Yugoslavia were performing sampling and analyses of samples. The countries have professional and reliable laboratories which in principle generate internationally comparable data. Discrepancies in measurement findings of concentrations of the pollution between Romanian and Hungarian scientists can not be fully explained but might have occurred because of differences in locations and time intervals of the sampling.

10. Acute effects, typical for cyanide, occurred for long stretches of the river system down to the confluence of the Tisza with the Danube: phyto- and zooplankton were down to zero when the cyanide plume passed and fish were killed in the plume or immediately after. The Hungarian authorities provided estimates of the total amount of fish killed in excess of one thousand tons, whereas the Romanian authorities informed that the amount of dead fish reported was very small. According to the Yugoslavian authorities a large amount of dead fish appeared in the Yugoslavian part of the Tisza river. No major fish kills were reported from the Danube. Soon after the cyanide plume passed, the aquatic micro-organisms recovered rapidly. Long-term effects on biodiversity will have to be shown from further analysis.

11. Chronic effects due to the heavy metals could not be assessed during the UN mission and should be subject to future assessments. Especially the sediments have the potential to influence the aquatic ecosystem; however, negative effects may already have occurred due to past inputs of heavy metals from a variety of sources especially in the Baia Mare area but also further downstream in Hungary. The spill of heavy metals had a local impact on the sediments close to the dam by drastically increasing the existing contamination with heavy metals. Allexisting heavy metal contamination exceeds quality criteria levels used by/in many other countries.

12. Villages close to the accident site were provided with alternative water sources, but were allegedly not informed about the spill sufficiently early. Downstream drinking water was not affected because of the use of alternative supplies and deep wells. Consequently, immediate human health risk seems to be minimal from this spill alone, but chronic health impacts due to long-term pollution by heavy metals are possible.

13. The amount of suspended solids and the grain size distribution of the tailings emerging from the dam has never been determined. This makes it difficult to estimate if any heavy metals could have been distributed in other forms than as soluble cyanide complexes.

14. The spill occurred in an area already contaminated with heavy metals from a long history of mining and metal processing. Upstream locations unaffected by this particular spill also contained high levels of some heavy metals. This illustrates the fact that the accident occurred in a region with a number of poorly maintained and operated plants and flotation ponds containing cyanide and/or heavy metals, many of which are leaking continuously. Pollution of surface and groundwater as well as soils due to this leaking or acute accidents is likely to occur and re-occur.

15. The recent accidents in Baia Mare and Baia Borsa have dramatically increased public awareness of the environmental and safety hazards of the mining industry. The Baia Mare accident showed that the level of public knowledge and understanding of risks inherent in mining and related industrial processes is very low. It also showed that there is insufficient communication between the various levels of authorities and between the authorities, the NGOs and the public concerning emergency preparedness, emergency response and damage prevention options and possibilities.

16. The Maramures region, being an area of mining and related industries is of economic importance to Romania and has the potential to create environmental problems downstream the Tisza River, which is dependent on the environment for its growing fishing and tourism industries and other economic activities. The importance of broader cross-border catchment-area cooperation to the rehabilitation and further development of the region is apparent.

17. The UN mission was unique and represented a useful model for inter-agency, multi-disciplinary rapid assessment missions. It was limited in size, scope and time and meant to assist in clarifying the facts around the Baia Mare accident. As such, it may help the Governments concerned and international partners in their further investigation and assessment of the spill and its impact, with a view to addressing longer-term rehabilitation needs of the area. It may also help clarify points of concern amongst NGOs and the local population.


1. A re-assessment should be made of the relationship between environmental 'benefits and risks' of the mining scheme of the Aurul S.A. company. In particular, a risk assessment study should be carried out of the entire system of remining the old tailings. This study should complement the Environmental Impact Assessment and the data contained therein.

2. In this connection, special emphasis should be given to the following aspects: - whether and how hydromonitoring of the material to be remined using cyanide – containing effluent can be avoided and replaced by an environmentally less risky process (like dry excavation and transport to the processing plant); whether processing of the materials in the plant can be done with less toxic materials;  how a sound emergency plan for the improved redesigned system (see above) can be attained in collaboration with all partners and stakeholders involved.

3. An inventory and risk assessment study should be made of all mining and related industries in the Maramures region, including abandoned sites, as a basis for better accident prevention and improved emergency preparedness and response measures.

4. In order to ensure prompt early warning and response, the existing on and off-site contingency plans should be revised with the relevant partners in line with Article 8 and Annex VII of the UN/ECE Convention on the Transboundary Effects of Industrial Accidents. Special attention should be paid to the possibility of a dam failure. The organizational roles and responsibilities off-site for dealing with a dam breach and the ensuing water pollution should be clarified. The plans should be practical, targeted to the site and fully accessible by workers and local stakeholders. The APELL process (Awareness and Preparedness for Emergencies at Local Level) as developed by UNEP can be a useful model on which to base such a review.

5. Romania should acceed to the UN/ECE Convention on Transboundary Effects of Industrial Accidents.

6. The sampling and analyses work was limited in time and scope. There is a need for: further analysis of the composition of the sediments in the new pond at Aurul to determine the amount and types of cyanide present;  monitoring of water quality in the wells to identify any delayed contamination; multinational monitoring of the long-term ecological effects of the spill on birds, mammals and water vegetation. NGOs from all countries concerned should also be involved in these activities; further analysis of the chemistry and toxic effects of cyanide, in particular the formation and stability of heavy metal cyanide complexes in the aquatic system, in order to better evaluate the fate and toxicity of cyanide and cyanide complexes in rivers under normal conditions;  further analysis of the heavy metals in the sediments, in order to enable a reliable assessment of the long-term risks of the spill; agreement by all countries in the Tisza catchment area on a set of common baseline indicators for water and sediment quality monitoring, and improvement and harmonization of their monitoring systems; an intercalibration study of chemical analyses of water and sediment samples, and information exchange on a regular basis between the authorities in all the countries involved.

7. In the light of a number of earlier accidents with tailing dams, it is advisable to review construction concepts and operation procedures related to enterprises using such dams, including concepts of secondary security or retention of spills at dams containing toxic effluents or other liquids. Also, more attention should be paid to better integrating the construction and operational aspects of the design.

8. With respect to enterprises using cyanide, special attention is needed for emergency preparedness, emergency response and public communication measures (the APELL process), as well as special monitoring and inspection by the authorities.

9. Process water ponds should, wherever possible, be reduced in quantity and to sizes which can be handled in emergencies. They should have retention systems for overflow or for accidents resulting from a break of the dam.

10. In the Maramures area, consideration should be given to changing drinking water supply systems for private households to public / collective systems.

11. Urgent immediate action, as a basis for long-term drinking water improvements, should include:  hydrogeological surveys as a basis for new water resources planning and development (Baia Mare area and along Somes river); the installation of groundwater monitoring by the local authorities with private wells being included; an inventory of existing private wells (Romania, Hungary, Yugoslavia);  an inventory of polluted areas, which endanger groundwater, surface and drinking water (entire river basin); the preparation of emergency water supplies (entire river basin); a health survey of the population in affected areas and proper monitoring of diseases caused by water pollution.

12. Both in the case of acute emergency and with respect to longer term impact, much can and should be done to raise awareness and inform the local population along the Somes, Tisza, Danube rivers and in the catchment area as a whole, concerning the characteristics and potential risks involved at the mining and other industrial activities upstream. Unnecessary concerns and potential economic losses can be avoided with well informed local communities. Communications channels between the respective central government, the district and local authorities, should be optimized and NGOs and other interest groups, especially at the local level, should be mobilized and assist in informing the population and in providing replies to their concerns. The APELL process (Awareness and Preparedness for Emergencies at Local Level) would be an appropriate process on which to base such a programme.

13. There is a strong need for a broad, longer term environmental management plan and sustainable development strategy for both the Maramures region in Romania and the entire catchment area of the Tisza river; a strategy which would address, inter alia, the mining and related industries, other economic activities (such as tourism and fishing), biological diversity requirements, and social needs and imperatives.

14. The UN mission did not address the question of liability and compensation related to the spill and its consequences. The issue of liability and compensation would be easier settled if there were an international regime. Support should be given to the proposal to develop a protocol on liability and compensation on accidents with transboundary impact, to the UN/ECE Convention on the Protection and Use of  transboundary Watercourses and International Lakes and the UN/ECE Convention on the Transboundary Effects of Industrial Accidents.

15. UNEP and other relevant international organizations should pay special attention to promoting: emergency preparedness and response (APELL) in communities close to hazardous installations and mine sites; revised design and operating codes for cyanide processes at mines; development of new international standards for fail-safe concepts in tailings dams; publication of a ‘best practices water management at mines’ guide and case studies; a review of permitting and inspection procedures of hazardous mining installations;  training workshops for national inspectorates in risk assessment and enforcement.

16. UNEP and its partners should also continue the dialogue with the mining industry to review design and operation codes, and promote a review and consultations on governmental approval permits and inspection procedures related to mining operations.

17. The Disaster Response Branch of OCHA and its Joint UNEP/OCHA Environment Unit should take appropriate steps to further develop the application of the concept of the UN Disaster Assessment and Coordination (UNDAC) to various environmental emergencies, including large-scale spills of mining tailings. The establishment of a small team of associated environmental experts should also be considered.

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