Persistence cleanses Wabush Lake
In 1999, the Iron Ore Company of Canada (IOC) embarked on a detailed options identification and assessment programme to recommend a tailings management system that would ensure compliance with new Canadian federal legislation relating to tailings management and disposal. At the same time IOC made a commitment to the local community to restore the ecological and recreational values of Wabush Lake by eliminating red water. This is solely a social obligation made by IOC to the community, as there is no regulatory requirement on red water.
Red water is the colloquial name for the reddish discolouration of lake water that results from the presence of fine (colloidal) iron stained quartz particles present in tailings. Since operations began in the early 1960s, IOC had deposited tailings into a designated portion of Wabush Lake in accordance with Newfoundland and Labrador provincial lease lot authorisations. This practice has increased the turbidity of the downstream waters, affecting the benthic ecology and reducing the social and recreational value of the lake.
Approximately 70 on land and in water options for tailings and red water management were evaluated over a six month period during 1999. An external advisory group provided guidance during this process, several public consultations were held with stakeholders and third party technical reviews were conducted to ensure the preferred option met all requirements under the law and also complied with IOC’s goals to improve the ecological and recreational values of Wabush Lake.
The preferred solution, agreed to by all stakeholders, was to consolidate tailings effluent to a single point discharge within a confined tailings impoundment area within the lake. The impoundment would be defined through construction of a fit for purpose 15 kilometre long rockfill dike to isolate the tailings impoundment from the rest of the lake. The dike would act like a large horizontal clarifier and provide the appropriate time and flow conditions to allow the fine tailings to settle within the dike thus reducing the lake turbidity.
Under the agreement negotiated with Environment Canada and the Department of Fisheries and Oceans, the proposed rockfill dike would be constructed immediately to the north of the current tailings beach area and provide sufficient storage capacity for 50 years of mine life.
Flocculation was identified as a possible option in 1999 but was rejected due to technical limitations. However, IOC recognised the potential of flocculation to further minimise the ecological footprint and provide a more environmentally friendly and long term sustainable solution than the approved rockfill dike project.
In 2002, IOC initiated a research and development project to optimise its tailings management programme. The intent of the project was to further reduce the ecological footprint of the tailings deposition area and to provide rapid clean up of the lake through elimination of red water. The resulting project, completed in 2005, and conducted with the support of Rio Tinto Technical Services (TS), has made significant progress towards solving the industry wide environmental problem of "red water".
IOC contracted flocculation experts within TS to identify the cause of the red water and further investigate whether in-line flocculation was feasible. TS and IOC conducted a staged programme from laboratory to pilot to full scale. The result was that a four month full scale flocculation trial in 2004 clearly demonstrated significant improvements to lake water quality, removing the suspended colloidal material that produced the red hue.
IOC is currently negotiating with the Government of Canada for approval of the revised tailings management programme, which will provide a better environmental outcome than the original dike based project and ensure the long term sustainability of the Wabush lake ecosystem.
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