Against all odds - mine construction in a remote location

Materials World magazine
,
3 Jan 2011
Preparing the mine site at Twangiza

Michael Forrest talks to Richard Levack, CEO & Managing Director of Banlaw Africa, about his company’s experience of constructing the Twangiza mine in the Democratic Republic of Congo.  

Mining companies are increasingly employing contractors to provide essential services for their operations. Usually the first contractors are those operating the exploration drill rigs but once the feasibility study is completed and the reserves known, the next stage is to build the mine. Even in a modest mine, the scale of the construction and the machinery is comparable to large civil engineering projects in developed countries. The most visible aspect is the open pit and associated earthworks, but before that can happen large machinery has to be transported to site, which is usually in remote locations with no infrastructure.

Mining equipment and processing plants are often sourced from around the globe and, consequently, the first logistical point in mine building is the nearest port. In the case of the construction of Canadian Banro Corp’s Twangiza mine in the Democratic Republic of Congo (DRC), that port is Mombassa in Kenya, some 1,800km to the mine site location in the eastern highlands at an elevation of 7,000ft (2,133m) above sea level. The mine is being built by Banlaw Africa Ltd.

Access first

The Twangiza area is underlain by sediments of Proterozoic age that have been intruded by porphyry sills, folded into a series of broad anticlines and synclines and subjected to very low-grade metamorphism. The gold mineralisation at the Main Twangiza deposit is hosted within mudstones, siltstones, greywackes and porphyries along the crest of a major anticlinal structure.

‘In the case of Twangiza,’ states founding Director and CEO Richard Levack, ‘the challenge was compounded by the distance from the Indian ocean port to the mine site in the South Kivu province of the DRC and the time-scale set by the client.’

Banlaw Africa was invited in mid 2009 to meet with Banro Corporation of Canada to discuss the construction of the Twangiza Mine. The project was to be fast-tracked as Banro had completed the purchase of a complete gold plant in Australia and arrangements had been made to ship it to Twangiza by the end of June 2010.

Banro’s mine is scheduled for production in late 2011 and is based on a measured and indicated resource of 6.72Moz of gold with a further inferred resource of 4.46Moz. Production is slated for an initial 100,000oz that translates into 1.4M cubic metres of ore and waste per year.

Banlaw’s first remit was to construct 40km of access road from a recently constructed national feeder road south of Bukavu to the mine exploration camp at 5,000ft in the mountains of South Kivu. Client Banro requested Banlaw to widen an existing track to form a road capable of carrying the 118-container truck convoy, including a 60t mill to a laydown area within the mine property. As part of the fast-track approach, the road was to be designed as construction progressed and this method was both cost effective and practical.

The worst of the rain season in this part of the DRC is from November till March, leaving a three-month weather window to open the 40kms of road. Earthmoving equipment was sourced from different parts of the world, shipped from South Africa, Dubai, Europe and the UK in December 2009 to Mombassa where it was transported overland through Kenya, Uganda, Rwanda and finally DRC. Six bridges between Bukavu and Twangiza were inadequate for crossing the heavy machinery, and fords had to be formed at each of these to permit access.

The equipment arrived at the start of the new road works in mid-February and work commenced during intermittent dry days. By the end of March, the infrastructure was substantially completed to the mine’s tented exploration camp which had been tripled in size to accommodate the development phase of the mine site. The lay-down operation was prepared in this area and this was completed ahead of schedule for the arrival of the processing plant.

The task now was to form an access road up to the plant site at 7,000ft (2,133m) above sea level and commence the 680,000m3 excavation for the mine plant. The fleet of equipment was deployed on the ‘western bypass’ road, which produced the least steep access to the proposed processing area. The main fleet, comprising two Hitachi EX670 large tracked excavators and six Bell B40 Articulated 40t trucks with all-wheel drive, travelled up the steep Spine access road, and commenced the plant site excavations that were on a critical path timeline for the completion of the concrete foundation works for the plant. Banlaw’s civil engineering staff had just completed a mine construction in Burkina Faso and were transferred to Twangiza to repeat the construction in the DRC.

The work involved bases for the usual gold plant structures, carbon in pulp tanks, mill foundations and up stands, crusher base and ROM retaining wall, as well as a multitude of minor bases and slabs for conveyors and process areas. It progressed well despite the logistical issues of getting supplies and spare parts through three countries from the port to the DRC. Airfreight, which is always a way of getting emergency supplies to any developing mine site, was not an option, since Eastern DRC is not serviced well with international airports or airstrips. Kigali in Rwanda or Nairobi in Kenya, were the two options and involved further transit through countries, which adds to the lead time for vital lifeline items.

Major setback

During the construction period, the western bypass access road to the plant site suffered a major setback in the form of a landslip, rendering it impassable. There was no option other than to upgrade the steep Spine direct access road from the exploration camp to the plant site.

‘Our construction equipment was able to upgrade this road to allow the container trucks, the mill and other very heavy loads to reach the construction area, although the incline proved very challenging,’ states, Levack. ‘For the heaviest loads, traction was required at both ends of the trailers and our drivers rose to the task, but not without referring to some sections as “heart attack hill”. All construction material had to be hauled up this steep road – cement, steel reinforcement, sand aggregate, management and workers’. Banlaw employs 600 out of a total workforce of 1,900 on the construction site.

‘The construction of roads and bridges was the major trial of the project. African roads in general, and Kivu province in particular, are made for light vehicles and not heavy mining kit so considerable earthworks were required’, explains Levack. ‘The other major task was to resettle over 1,000 artisanal miners working around Twangiza. We have a responsibility to assist these people to come to terms with the mining project that has an estimated life of 20 years. With Banro, we have employed many locals in construction and road building and have embarked on building new houses, schools and a church at the nearby village of Cinjra. The great majority were successfully tempted from artisanal mining activities into casual labour supply for the mine. Outstanding works at this time are mechanical, pipe and electrical works, alongside the building of the tailings dam, which has just commenced,’ he added.

Further information

Banlaw Africa Group Richard Levack, CEO & Managing Director, Banlaw Africa Ltd. PO Box 766, Tarkwa, Western Ghana. Tel: +233 (0)244 334 245/ +226 70 42 42 96.