TUNNELLING: Redpath tackles inclined excavation in sand

BOTSWANA - Redpath South Africa has been awarded a first-of-its-kind inclined tunnelling contract in Africa. The approximately C$9.4- for the development of a sand tunnel at the re-commissioned Ghaghoo diamond mine in Botswana. The site, which is located approximately 200 km north of Gaborone, falls within in the Central Kalahari Game Reserve.

The project involves the development of the tunnel to 112 metres vertically below the surface at an inclination of 8°. The segmented, concrete-lined tunnel is to be completed in November 2011. About 403 metres will pass through pure sand and another 121 metres will pass through the transition from sand to basalt. Workers will be protected from sand collapse by a 50-tonne shield.

The sand tunnel is due for completion at the end of June 2012. However, Iversen expects that Redpath 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.

Redpath South Africa mine manager Olaf Iversen points out that the company expects several additional challenges will be encountered in constructing the inclined sand tunnel at the sand and basalt interface because water could possibly be intersected. What's more, he notes that the Redpath'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 says 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."

Gem Diamonds purchased the Gope Exploration Company, 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 45,000 per month. In parallel with this, a bankable feasibility study will be done for phase 2 of the project.

Contact information for Gope Exploration is posted at www.GemDiamonds.com.