The following is an article by Rebecca Getty, Sarah McConnell, BHP which was published in the Mine Closure 2024 supplement.
Leveraging legacies to deliver a better future
BHP’s purpose is to bring people and resources together to build a better world
From exploration, through every stage of an asset’s life cycle, to post-closure and achieving optimised closure outcomes, closure is connected, either directly or indirectly, to our global risks. It helps support our commitment to social value and our aspiration to help build a better world, and requires many disciplines to help imagine and plan the future and the legacy we want to leave.
To learn from our past legacies and reimagine what closure means for BHP, we undertook a review of our closure processes in 2023 with the objectives of:
- strengthening the focus on early and progressive closure and integration with the many disciplines and functions closure is interconnected with.
- developing a companywide standard that is informed by international good practice and the business. BHP is a
member of the ICMM and is committed to integrate closure into planning and decisionmaking. - being transparent and meaningfully engaging with a broad range of stakeholders to incorporate as much feedback and learnings as possible.
- emphasising the interconnectedness of closure to raise awareness and support early, integrated closure planning and to help improve collaboration.
As a result of that review, we updated our companywide Closure and Legacy Management Global Standard (Global Standard) which applies to everyone in BHP.
This defines our performance requirements for managing closure risk and is in line with our values and public commitments.
Good closure planning is key to doing business the right way, from beginning to end
Because closure planning is multi-disciplinary and a process, not just an event, we have defined three closure culture goals:
- risk driven with a focus on mitigating risks and controlling closure liabilities
- integrated contributions because we all have a role to play in achieving closure objectives
- early and progressive closure management implemented throughout the entire life cycle of the asset to achieve our long-term objectives.
Embedding these culture goals within our Global Standard and how we work supports fully informed and transparent decision-making, empowering decision-makers to consider the long-term impacts when making business decisions, including the impacts on social value. This helps us achieve our goal to leave a positive legacy.
BHP’s global closure context
BHP operates sites across Australia and Chile, with a site in Canada (Jansen) due to commence mining soon. However, an often-overlooked asset in our portfolio is Legacy Assets, which stewards 23 non-producing sites in various stages of closure across Canada and the US. These sites mined and processed copper, zinc, uranium, tin, and gold and have tailings facilities, open pits, overburdens storage areas, and remediation requirements.
Sites may have multiple first nations and rights holders and, in some cases, are near communities. The aim is to progress these sites towards relinquishment, divestment, or long-term management in the most effective manner.
Opportunities for repurposing are considered as appropriate to improve social value. For many of these sites, there is no
formal mechanism to relinquish the liabilities and they are expected to be held in longterm management.
We also have three nonproducing sites in Western Australia (part of the Western Australia Iron Ore asset), with two in the Pilbara and Beenup in the South West.
Legacy sites at BHP
BHP’s legacy sites provide important learnings for planning and executing closure at our operating sites.
The term ‘legacy site’ has different meanings across companies and jurisdictions.
In general, the term is used to indicate sites that still need some remediation or final closure activities and are not yet considered ‘closed’.
Learning from closure shortfalls: choosing the cheapest solution and not testing assumptions
Selbaie, located in northwestern Quebec, Canada, is 130 km from the nearest community and is situated in a relatively cold, semi-humid climate with a mean annual temperature of 0°C and precipitation of 850 mm.
Selbaie was a surface and underground copper-zinc mine, which operated between 1981 and 2004 and includes an open pit, potentially acid-forming tailings, and overburden rock stored in unlined aboveground facilities. The site was reclaimed between 2004 and 2006 and both facilities were covered with one metre of silty-sand glacial till seeded with native plant species. The chosen closure plan for the overburden emplacement was one of the lowest cost options and was approved
by provincial regulatory authorities. However, it did not appropriately account for long-term acid mine drainage as the cover was too permeable in a wetter climate to act as an effective hydraulic barrier on the waste rock pile.
As a result, BHP currently spends double on annual management than was planned and this isn’t a forever solution. Water treatment costs are high and the site is remote, requiring year-round access on sometimes icy roads. If the money had been spent upfront relocating the material to the open pit and submerging it, it would have been two-to-three times the cost of covering, however, it would have been more cost effective long-term. Different management options are currently being assessed to improve outcomes at Selbaie.
Innovative water treatment: looking for novel opportunities
One of our most innovative water treatment facilities is at Island Copper, located on the northern coast of Vancouver Island, British Columbia, Canada. The former Island Copper open pit mine operated between 1971 and 1995, producing copper and molybdenum concentrates, as well as gold and silver byproducts. After 24 years of ore extraction, the site was closed and reclaimed, and now has a large volume of contact water requiring long-term collection and treatment.
Upon closure, the open pit was flooded with seawater and then capped with a layer of freshwater from a nearby river, resulting in the formation of three layers of water of different salinities within the pit, which are maintained due to their unique densities. This layered structure is used to manage and remove metals from acid and metalliferous drainage that occurs when rainwater drains through the nearby waste rock piles into the pit lake.
Treatment of water in the pit lake is achieved through the biological process of phytoremediation. A low-cost liquid fertiliser is added to the top water layer of the lake yearround.
The fertiliser promotes growth of phytoplankton cells, which bond to the metals and then sink to the bottom.
The phytoplankton cells also provide a carbon source for oxidation in the middle sea water level which creates low-oxygen conditions in this layer to further reduce metal concentrations. Treated water that complies with regulatory standards then flows from the top layer to the adjacent marine environment. Divergent thinking here led to an innovative, cost-effective water treatment solution.
Lessns learned from our legacy sites
- Adopt a risk-based approach to closure design and execution. Regulatory compliance is a good start but may not
be enough in the long term. Always consider the ‘what-ifs’ and the ‘forever’ case - Don’t assume everything will go to plan
- Spend time in planning (it’s cheaper than fixing mistakes)
- Test assumptions such as cover designs
- Monitor for closure (not compliance) and consider the time lag!
- Long-term water management is a reality for many sites
- Manage data. Knowledge is critical and must be retained for the closure and post-closure phases to avoid the requirement for rework and costly and time-consuming additional studies
Finally, there are opportunities!
Cost-effective treatments don’t have to be innovative and we should always collaborate with key stakeholders. There may be opportunities out there we haven’t realised yet, and our legacy is what we leave them.
