The world is demanding greater awareness and environment preservation action from large-scale industries. For the mining sector, this means paying attention to one of its largest environmental exposures and liabilities: mine waste. Golder Associates examines the greatest challenges, emerging trends and best practice applications for mine waste – tailings in particular. Laura Cornish reports.
Golder’s environmental consultation, engineering design and construction expertise, coupled with its vast global mining engineering- focused business, facilitates a specialised focus on all tailings facility aspects – from design and facility development through to construction, operational management, closure and rehabilitation.
Thanks to the onset of more stringent mining environmental legislation and the implementation of global best practices, this business area is seeing considerable growth, not only in South Africa, but throughout the African continent.
“We are not a general civil engineering company; we concentrate and specialise in key market sector areas, which for the mining sector include water supply, wastewater, mining infrastructure, geotechnical engineering and project management for large-scale projects,” highlights Golder’s head of engineering services, Charles Naidoo.
The company’s Ground Engineering Division incorporates tailings and mine waste management. Principal and strategic advisor to engineering, Francois Marais, outlines Golder‘s three ground engineering sub disciplines: tailings delivery schemes such as pumps and pipeline systems, surveillance, which involves tailings facility monitoring – the on-going monitoring of tailings facilities in terms of structural integrity, Golder‘s performance against design intent and environmental exposure, and tailings facility designs.
Tailings – an increasingly significant role
“The viability of a new mine is influenced by the feasibility and cost-effectiveness of the tailings stream management, which ultimately boils down to implementing the correct and appropriate technology for the application in question,” Marais acknowledges. “Our ultimate aim is to demonstrate that we can add value to unlocking the un-mined prosperities and resources in Africa by ensuring mine waste and tailings management is conducted in a responsible and environmental sustainable manner,” Naidoo adds.
Mining companies are looking to consulting experts who understand and offer the full suite of tailings technologies and methodologies, and are clearly showing a preference for companies capable of offering the full ‘cradle to grave’ service, from characterisation of the tailings for new facilities, including feasible designs, through to tailings closure planning. Companies with comprehensive knowledge and understanding of all tailings aspects are benefiting in today’s new, environment-conscious world.
“Golder tailings experts don’t only have a thorough knowledge of all current tailings technologies and practices, but further acknowledge that technology ranges are directly linked to how tailings/slimes/slurries are ‘densified’ through physical and chemical treatment, for example dewatered or thickened, before being pumped and disposed onto a tailings facility. Knowledge of all deposition methodologies, including cycloning and paste depositioning, dewatered and solid mine waste disposal is an asset,” Marais says. And, while the construction and management of tailings facilities have always presented environmental challenges, there are several major challenges and concerns the industry is currently facing and addressing, which Marais outlines.
Meeting international best practices
“Ensuring that the design process for a new tailings facility meets international best practice is one of the industry’s greatest challenges. Investment companies in mining developments nowadays expect only the most viable, sustainable and environmental defensible standards. Because we recognise that the development and operation of a tailings facility has the potential to have the largest environmental impact, we are sensitive in our design approach and apply only the most viable design technologies e.g. engineering barrier systems that would pose minimum risk to the receiving environment,” Marais notes.
Golder’s tactical method is to apply a quantified modelling approach, which simulates the tailings source, the seepage pathway and receptors within the zone of influence of the tailings facility. “This enables us to quantify the impact of the tailings facility in terms of acceptable risk levels.”
Understanding in-country standards
From an African perspective, the interpretation and comprehension of specific in-country standards is another great challenge. Fortunately, thanks to specialised input from its vast array of international colleagues, such challenges are easily overcome, “especially if we are involved in the full design process for a typical tailings facility, which includes feasibility studies, detailed designs and over-seeing implementation of the facility in terms of quality control, contract administration, site supervision and project management”.
Golder also has teams in place that conduct quarterly and annual inspections and audits on existing tailings operations. Marais says that this surveillance service must be in compliance with in-country legislation and international best practices.
“Regardless of country or client, we want them to know that together we can find solutions to operate in a sustainable, environment-respecting manner,” Naidoo reiterates.
Reducing closure liabilities
Marias identifies that “using defunct opencast operations for tailings disposal has become an attractive option for viable tailings disposal and at the same time reducing closure liabilities. The challenge, however, is to do so in an environmentally acceptable manner.” Golder personnel are often involved during closure and post-closure design activities where tailings engineering, specialised technology and scientific knowledge is required.
New engineering generations
“Growing and nurturing young and upcoming engineers into these specialised areas requires dedication. The fundamental discipline and feed source for tailings engineers is geotechnical engineering; however, we believe the success of the nurturing process of young engineers is through project exposure – experience is key,” says Marais.
Marias acknowledges that some of Golder’s clients are forming joint venture consortiums for large-scale reclamation projects, particularly in the gold and uranium-focused sectors. “The focus has also shifted from the East Rand to the far West Rand in Gauteng. Companies are driven by improved processing and beneficiation technologies, an attractive gold price and the anticipated shortage of uranium in the nearby future. “The long-term environmental benefit of large-scale tailings reclamation projects is footprint clean-ups of current tailings facilities.” The technology challenges are to reclaim, reprocess and transport large tailings tonnages and to develop new mega tailings storage facilities to ensure that these projects are viable”.
The coal industry also has much to gain from the correct handling and management of its slurry and coal discards. “When slurry and coal discards are handled properly within well-planned and designed facilities, opportunities could open up to reclaim these waste sources as future products. This has substantial environmental and financial benefits, as lower grade coal waste material is now being considered for coal-fired power station applications.
Power plant technology is being upgraded specifically to take on lower grade coal materials.” Marais says up to 30% of run of mine is currently classified as coal mine waste materials.
In Africa, particularly the emergence of new coal mines in Mozambique, coal waste rock volumes are extremely high due to high overburden stripping ratios, to expose thicker coal seams. This is leading to the establishment of large-scale waste rock dumps, which can be equally as hazardous to the environment as tailings facilities if not designed, built and managed properly. “Water and seepage management is essential to minimise potential environmental impacts from coal waste rock dumps.”
Golder’s presence in Africa
Golder’s presence in Africa is already well established in certain regions, but is likely to continue growing as mining development expands and environmental legislation escalates, resulting in a greater need for environmental engineering consultants. According to Naidoo, the company’s exposure in West Africa is vast, particularly for its tailings, geotechnical engineering and mining infrastructure services. “We are also active in Mozambique’s Tete and Maputo areas as well as in Botswana – again, providing various tailings and mine waste activity services. Outside of these two coal regions, we also have a strong project presence in the Democratic Republic of the Congo, Ethiopia and Zambia.”
A case study: New South Deep Doornpoort tailings storage facility
- Golder was leading design and implementation consultant.
- Golder completed this 20-month R387 million project on time and within budget, meeting all the client deadlines.
- Excellent safety record with working over 1.6 million man hours lost-time injury free.
- Over 4 million cubic metres of earthworks, 35 km of steel HDPE pipelines, four motorised control centres, three pump stations and 14 ha of HDPE lining for 1 million cubic metres of return water dam.
- Golder manages 10 sub-consultants and two main contractors.
- Project manager: André Richardt – head of integrated project management at Golder.