One of the longest-running opencast mining contracts in recent Concor Opencast Mining history has now been completed. The Impala open-pit project, located on the Western Limb of the Bushveld Complex near Rustenburg, South Africa, was awarded in 2002 by Impala Platinum and mining commenced in the vicinity of Impala # 6 shaft, with the Concor team tackling the Merenksy orebody first. In 2005 the team began mining the UG2 orebody.
The two Merensky faces were relatively small scale, while the UG2 was present on a much larger scale, with seven faces mined. These reefs ranged over a 9 km area and were mined to a depth of 35 m. Below, the Impala Platinum underground operation mined ore from its shaft systems. The open-pit contract included crushing the material to <300 mm and its delivery to the mine’s stockpile, as well as rehabilitation of mined areas.
Since 2002 the contact was renewed on an annual basis until all surface resources were depleted. Between November 2009 and December 2013 Concor mined 49,340,574 bank m3 of blasted overburden, 6,576,454 bank m3 of topsoil and 8,871,767 t of reef.
“This project was tightly controlled throughout its duration to mitigate the associated challenges,” Roger Hearne, Acting General Manager of Concor Opencast Mining, says. “For example, mining took place in close proximity to both mine infrastructure and housing occupied by members of the local community. Great care had to be taken not to impact these structures and we achieved this by keeping the vibration from blasting to a minimum. In addition, blasting was only carried out twice a week out of consideration for the local communities.
“At all times we also had to be careful not to hole through to the mine’s underground workings. For this, we depended on existing surveys and worked closely with the mine surveyor to ensure that highwall positions were correct.”
At the end of the project, the team had achieved more than 5 million fatality free hours — 1,196 LTI-free days, earning several Impala Platinum and Concor safety awards along the way. Weekly safety audits were carried out by Concor, while Impala Platinum undertook 40 day safety audits. Visible felt leadership (VFL) was also part of the safety environment, aimed at influencing and transforming behaviour.
A total of 240 people worked on the project. Equipment comprised five bulk excavators for overburden removal; six smaller excavators for cleaning the orebody and extraction; five dozers for moving overburden and top soil; 25 trucks on site; three water carts and various ancillary support plant. A static jaw crusher serviced the southern pits during the project, while a mobile jaw crusher serviced the northern pits.
Concor applied the strip mining method, with average advances of 30 m wide. The team was also responsible for drilling and blasting operations in all pits. The orebody was exposed, extracted and transported to a rail siding 5 km away, where it was crushed and then transported by rail to the plant for further processing. Haul road maintenance was critical to minimise wear and tear on vehicles and ensure safety.
The company employed a local emerging sub-contracting company, which it mentored to successfully undertake the required top soil rehabilitation. Personnel were trained in production methodology, on how to achieve targets, on costing and on safety issues.