Diamond-mining company Koidu Holdings reports that development on the Koidu kimberlite expansion project, in Sierra Leone, is on schedule and within budget, promising to ramp up mining production to 100 000 t/m by the second quarter of 2012.
Some six months into the project to grow the mine’s output, the operation is employing over 1 500 people on mining operations and the four components of the expansion. Owner Koidu Holdings is working with South Africa-based lump-sum turnkey contractor Consulmet and a host of local and global subcontractors to meet a tight project timeline.
On the mining side, the expansion will see the total mining rate ramped up from 300 000 t/m to 1.5-million tons a month. To process these tonnages, a new 180 t/h run-of-mine treatment plant is being erected, with associated waste disposal facilities; and an entirely new mine infrastructure is also under development to cater for the fivefold increase in the scale of operations.
Koidu Holdings CEO Jan Joubert reports the magnitude of each of these subprojects is considerable. “Finding ways to successfully implement these in Sierra Leone involved substantial resources during the project planning phases,” says Joubert. He adds that, in the project area, 330 km east of the nation’s capital, Freetown, the local systems of administration and infrastructure are weak.

“The company’s nine years of operating in Sierra Leone have given it the insight to pre-empt potential shortcomings and bottlenecks, and to draw on strong relationships developed within the country. Technically, these projects are relatively straightforward but the real challenge for the team is to overcome the capacity shortages in terms of skills availability and infrastructure,” says Joubert. He emphasises the choice of contracting strategy as a key element of the project. “Securing lump-sum turnkey contracts for the new processing plant and the required infrastructure development projects with Consulmet are, perhaps, the company’s most valuable safety net, or insurance policy, in this project,” says Joubert.
He adds that the detailed studies across all disciplines during the initial planning phases provided a clear understanding of what was required. “This type of contract transfers much of the risk and responsibility to the contractor, allowing us to focus on the other equally important aspects of the operation and avoid loading the project with heavy contract management costs,” says Joubert.
The new plant site is located 500 m to the west of the existing plant, allowing production to continue uninterrupted during the erection of the new processing facility. The design of the new plant follows a traditional kimberlite treatment process, using technologies appropriate to the operating conditions in Sierra Leone, with high rainfall, high humidity and fairly limited engineering and electrical skills.
The planning took into consideration the logistics challenges and long lead times related to procurement and shipping – it takes six to eight weeks for a container to arrive from South Africa, for instance.
Consulmet director Gavin Boyle reports Koidu’s approach to the design was to develop a processing plant that is user-friendly and easy to operate in a challenging environment. “This was achieved by keeping the flow sheet simple and incorporating relatively high levels of redundancy and flexibility into the circuit to cater for the known variability in kimberlite characteristics from the various orebodies,” says Boyle. He adds that extensive testwork on all kimberlite types was carried out during the feasibility study and these results guided the plant design process.
Because of the remoteness of the Koidu site, the various plant modules are being fabricated and trial-erected by Consulmet in South Africa to ensure that all components are correctly engineered and that each module is functioning prior to being sandblasted, painted and then dismantled and packed in containers for shipment to Sierra Leone. This approach was adopted to detect problems that could cause delays in construction and commissioning on site.
The mine infrastructure development project was also awarded to Consulmet. This contract called for a new access control system, a change house, mess facilities, a workshop, central stores, a fuel depot, an emulsion storage facility and training facilities. Also included were a generator house, electrical and water distribution systems, accommodation facilities, entertainment areas, waste management systems, drainage systems and the extension of the office complex.

Joubert is pleased with the progress on the pro- ject to date, with half the plant project and nearly 40% of the infrastructure project complete.

“Koidu has passed some of the most difficult phases of the project execution,” he says, “When one considers the project timelines of other recently developed kimberlite operations, this is certainly exceptional performance.”
Mining is currently focused on the K2 openpit; the expansions will bring the K1 openpit complex on line with an aggressive waste stripping programme to remove the remnants of the K1 vertical pit. The K1 complex includes the main kimberlite pipe and two dyke zones flanking the northern and southern margins of the pipe, as well as two enlargements on the dyke zones developed about 200 m on either side of K1.
The new mining fleet is now moving about 750 000 t/m from K1, a rate that will increase to over one-million tons a month; the targeted K2 production rate of 500 000 t/m will bring the total mining rate to 1.5-million tons a month from September 2011. This will ensure the required output by the time the new treatment plant is commissioned next year.