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Send  Share  RSS  Twitter  26 Jul 2011

MINING: Redpath Awarded First Incline Sand Tunnel Contract in Africa


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Redpath South Africa has been awarded a first-of-its-kind incline tunnelling contract in Africa, thanks to the company’s innovative and cost-effective approach to the project.

International diamond producer, Gem Diamonds has awarded a R67-million contract to leading contract mining firm, Redpath South Africa for the development of a sand tunnel at the re-commissioned Ghaghoo Diamond Mine in Botswana.

A Gem Diamonds technical representative notes that Redpath South Africa’s unique and innovative sand tunnel construction proposal resulted in the company being awarded the contract in May 2011, following a successful tender submission in February 2011.

“During the tender process, Gem Diamonds provided each contractor with a specific design for the segmented tunnel; however, the process of clearing the excavated sand was left open. Redpath South Africa was the only contractor that recommended the cost-effective use of conveyor belts for the removal of the sand, as opposed to articulated dump trucks. Although the initial set-up costs of the conveyor belts are high, the long-term running costs are significantly-lower than using trucks, which will ultimately improve the overall efficiency of the project,” he explains.

Redpath South Africa mine manager Olaf Iversen points out that the company’s scope of the project involves the development of the tunnel to 112 m vertically below the surface at and inclination of 8 degrees. The site, which is located approximately 200 km north of Gaborone, falls within in the Central Kalahari Game Reserve.

“The first phase of the project is due to begin in July 2011 with the establishment of a box cut 25 m deep and 171 m long into the Kalahari sand, which will provide safe and secure access to the underground mine,” he explains. “The box cut and portal support is expected to be completed in November2011, by which time we will begin excavation work for the concrete-lined segmented sand tunnel, 403 m in pure sand and 121 m in transition from sand to basalt, which acts as a cylindrical shield to protect workers and equipment located underground.”

Iversen explains that labourers will work within the 50-ton shield in order to move the tunnel forward segment-by-segment, by loading the sand onto the conveyor belt before it is fed out of the mine. “The width of each segment for this particular project is 0,61 m, and we are aiming to move forward six segments or 3,6-m-per-day,” he continues.

The sand tunnel is due for completion at the end of June 2012; however, Iversen admits that Redpath South Africa faces numerous challenges in the upcoming months. “The Ghaghoo Diamond Mine is extremely remote and isolated, and the majority of the 93 Redpath staff members working on the project will be located on site. In order to maximise productivity and reduce logistical challenges, staff members will be working 14-days-on and seven-days-off,” he continues.

Iversen points out that they expect to be faced with an additional challenge in constructing the inclined sand tunnel at the sand and basalt interface – where water could possibly be intersected. What’s more, he notes that the Redpath South Africa’s entire scope of the project will have to be undertaken using diesel-powered generators in a region with no electricity.

As part of its commitment to social and economic development, Iversen notes that Redpath South Africa will employ 78 staff members from communities surrounding the project. “The Client, Gem Diamonds held numerous discussions and road shows for the local communities, in order to ensure that we are able to get the population directly involved in the project, while creating sustainable skills development in the area. What’s more, all segments for the sand tunnel will be manufactured in Gaborone, in order to ensure that investment in the project remains in Botswana.”

Iversen believes that Redpath South Africa will sustain its excellent safety record during the project through a dedicated training programme designed for the local workforce. “Once the construction of the shield has been completed, we will undertake a full risk assessment before putting in place the necessary operating and training procedures,” he explains. “All training will be done onsite, in order to equip the workforce with the most practical and hands-on safety skills and knowledge.”

Gem Diamonds purchased the Gope Exploration Company Pty (Ltd), which owns the rights to the Gope Deposit, in 2007. It has since been renamed Ghaghoo Diamond Mine, and a mining licence was awarded to the company in January 2011. The Gope 25 kimberlite pipe was first discovered in 1981, with drill shafts to date reaching 1 000 m into the volcanic rock. Gem Diamonds states that once the sand tunnel is complete, the decline will be extended to the kimberlite pipe, and phase 1 of the mining will commence at 45 ktpm. In parallel with this, a bankable feasibility study will be done for phase 2 of the project.

Looking to the future, Iversen believes that Redpath South Africa will complete the first phase of the sand tunnel on time and within budget, and he is optimistic that the company could be well-positioned to be awarded the contract for the decline development of the project towards the end of 2012.

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