Abstract

Temporary and long-term storage of reactive mine waste (waste rock and tailings containing sulfide) is a confronting problem with no clear path to a beneficial outcome. While it is well understood that avoiding mine waste management may be associated with reduced costs in the short term but significant costs for treatment in the long term, it is less understood that pro-active waste management is rewarded with reduced costs during operations (reduced capex and opex), increased net present value, and most importantly, significantly reduced closure bonding.

Here, we review a project located near Powell River BC, where appropriate information was available early in the project, and how one miner chose pro-active waste management.

A multiple redundancy approach to reactive waste management that is founded in best practice was used to build a robust life-of-mine waste management plan which is associated with reduced obligations for water management, and reduced costs for treatment.

Geochemical characterisation of mine waste was performed early in the planning stages which allowed a small, private owner-operator, to make informed decisions about waste management.

Waste materials were categorized as potentially acid generating, but with relatively low capacity. Instead of employing the traditional approach of isolation of the waste and treatment of acidic seepage, an alternative design specification was employed: add an appropriate quantity of neutralisation agents through blending and reclassify the material as non-acid generating. Secondary mitigation or contingency measures were employed such as monitoring and full contract water capture prior to discharge. 

The following mitigation measures were considered for this project:

• Distribute limestone/marble or calcium containing carbonates to help maintain low reactivity state (primary)
• Grading and construction of surface features for water shedding (peripheral)
• Collection of surface water and seepage for routing from a designated release facility where ongoing water quality monitoring will provide adequate forewarning if there is deviation from the expected response (contingency)
• Bituminous or geomembrane liner for the waste (excluded)
• Water treatment or polishing (contingency)

The purpose of the waste management plan is to promote geochemical stabilization by addition of calcite and avoid excess water flow through the facility. This approach derisks operations from an environmental impact perspective, reduces costs associated with waste management and water management and has the general effect of increasing net present value and significantly reducing closure bond obligations.