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Water effluent management of Balmer Lake tailings management system

University of British Columbia

In recent years, environmental concerns have increased awareness in the mining industry resulting in more resources being devoted to minimizing the environmental impact of mining and its effluents. This study was carried out to assess the effectivenss of Baimer Lake tailing managment system in improving effluent and to generate data for the mine closure plan of the A.W. White Mine of Goldcorp Inc. located in Red Lake, Northwestern Ontario. At this mine, gold ore is treated using a cyanidation-Merrill-Crowe process and the fine tailings are discharged to a 3-pond tailings system. A review of the main legislation affecting tailings management in Ontario revealed that the Mining Act, Fisheries Act, Environment Protection Act and the Ontario Water Resources Act (OWRA) are most relevant. Under the authority of OWRA, site-specific enforceable water quality parameters are specified in the Certificate of Approval. The main objective of this work was to establish the effectiveness of Baimer Lake tailings management system in improving effluent quality. In order to achieve this, the study involved a hydrological assessment, water quality assessment and an evaluation of the effectiveness of the tailings ponds in improving effluent. A water and mass balance model for the system was also developed. The results can be used to improve or validate the existing water management system with quantifiable data. The study was able to establish that catchment hydrology plays a very significant role in the Balmer Lake tailings system, with natural inflow accounting for 84% of the total inflow into Balmer Lake. The impact of hydrology on Pond 1 is that it reduces the retention time in the pond and does not allow, therefore, sufficient time for pond mechanisms such as volatilization, precipitation and sedimentation to effectively improve the effluent quality. In Pond 2, hydrology is not significant due to the fact that the catchment area is small. In Pond 3, the excess runoff during late spring and early summer does not allow sufficient time for effluent improvement. This can possibly result in the discharge of non-compliant effluents relative to the Certificate of Approval, enforced by the Ontario Ministry of Environment under the legislative authority of the OWRA. To avoid this, the Certificate of Approval specifies that from May 1 to July 1 no discharge should be allowed from Balmer Lake without permission from the Ministry of Environment. The excess runoff, however, often forces discharge to protect the impoundment from being overtaxed. The evaluation of the effectiveness of the tailings management system was carried out using total efficiency, mass removal efficiency and effluent improvement efficiency due to dilution. Pond 1 was found to be ineffective in improving effluent quality. Over the years, the accumulation of tailings in the pond has reduced its effectiveness by reducing the retention time. A decline in overall effluent improvement efficiency was observed over a 7 year period. Although the overall efficiency for all parameters was positive, it was found that it was mainly due to dilution for cyanide and totally due to dilution for copper and nickel. Unlike Pond 1, the mass removal efficiency for Pond 2 was positive for all the water quality parameters. Mass removal of cyanide was attributed to volatilization with pH at 7.8, while for copper and nickel, precipitation and sedimentation is the most likely removal mechanism. In Pond 3, both mass removal and dilution were significant in improving effluent quality. The water and mass balance model was used to evaluate the effect of changing some of the water input parameters on the overall tailings management system. Using the model it was found that by diverting 20% of the catchment area, an extra 2 month retention period in Balmer Lake would result. This would significantly reduce the problem caused by the excess spring runoff into Balmer Lake and could be achieved by diverting Natural Drainage River 3 (NDR3) just before it enters Pond 1, hence reducing the Pond 1 catchment area as well. Diverting NDR3 would also result in a better performance for Ponds 1 and 2 due to increased retention times. This would ensure better water and waste water management for the Balmer Lake tailings system.

Thesis/Dissertation

application/pdf

2009-02-06

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http://hdl.handle.net/2429/4202

Mining Engineering

University of British Columbia

UBCV

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