Les Mines Selbaie
Les Mines Selbaie is a 7600 tonnes per day copper-zinc mill and mine which involves both underground and open pit workings. Copper and zinc flotation concentrates are shipped off-site for further processing. Other components of the mine site include overburden piles, mine rock piles, tailings impoundment and a clarification pond. The mine rock has been segregated into highly acid generating, acid generating and non-acid generating piles. The initial tailings disposal system was based on the Robynski method of thickened tailings placed from a central discharge to form a cone. This system has been replaced by a conventional spigotted discharge and system of surrounding dykes. The clarification pond is used to settle fines from water draining from the tailings disposal system. Selbaie has been experiencing increasing acidic drainage from the mine rock piles, mine rock berms and tailings deposits. The acidity is controlled using a water treatment plant utilizing lime.
Dr. Robertson was the Project Principal and Senior Technical Leader of the SRK team that was retained by Billiton to carry out a preliminary environmental liability evaluation followed by a more detailed environmental audit for the mine site as part of their pre-acquisition due diligence.
Environmental Liability Evaluation
A pre-acquisition site reconnaissance was conducted to assess current and potential issues of environmental liability. Inspections were made of the major mine and mill components, the property compliance data was reviewed and site personnel interviewed. These were non-sampling assessments, based on field observations and technical review of the main components at the site. Consequently, the liability assessments and cost estimates relied, to a large extent, on our experience and engineering judgement. Closure plan options were developed to address the major issues, with an estimate of the costs for implementation of the recommended options.
The objective of this phase was to complete the detailed site environmental audit. Where possible, this phase of data gathering and evaluation followed work previously done on site. There were components of the audit pertaining to acid rock drainage and mine environmental liability and costs that had not been identified previously. In assessing financial liability, compliance under current permit or regulatory requirements was assessed and also the additional environmental liability considered likely in the near future (less than 10 years) under the prevailing regulatory trends.
- Preliminary environmental liability evaluation
- Detailed environmental audit
BHP Billiton Ltd.
Risk & Liability Assessments