Desert heat, inhospitable terrain, and newly discovered plants have all served to make life difficult for the Alstom/ABB joint venture currently building a transmission line across the remote hinterland of Namibia in southern Africa. The R160 million (21million Euros) project entails building a 251km 400kV single circuit transmission line across one of the region’s remotest areas, the largely unexplored 1500m high Huib-Hoch plateau.
Namibian parastatal utility NamPower awarded the design and build contract in March for the supply of power from NamPower’s Kokerboom substation near Keetmanshoop to a new 400/66 kV substation at Obib, eight km from the new Anglo American Skorpion zinc refinery near Rosh Pinah in southern Namibia. The project is due for completion in April next year.
The Skorpion line has been designed with future southern African power infrastructure requirements in mind. The transmission line will also carry an optical fibre ground wire (OPGW) link, which will enable NamPower to enter the telecommunications infrastructure market once it becomes licensed to do so.
The contract comes hard on the heels of the R370million (49million Euros) Rand interconnector project undertaken jointly by Alstom and ABB and completed ahead of schedule late last year. The interconnection contract, covering the 710km between Kokerboom substation near Keetmanshoop to Auas substation near Windhoek, was the biggest transmission line contract executed in southern Africa to date. The interconnector will feed the Skorpion line.
Pooling resources
The sheer magnitude of the transmission lines contract necessitated pooling the resources of the two companies in a consortium, according to Alstom South Africa group managing director, Mark Wilson. “By virtue of the size of the project and the need to pursue a fast-track programme, it made sense to approach the contract as a joint venture. It also gives NamPower the confidence that it is relying on two global players in the electric power transmission and distribution infrastructure market, with proven capabilities in southern Africa, to deliver state of the art technology on time and to provide long-term technical support in the future”, he said.
The Alstom and ABB teams are working from either end of the line respectively – one from the Kokerboom substation and the other from the yet-to-be-built 400/66 kV Obib substation that will feed the new Anglo American Corporation zinc refinery situated about 40 km north of the existing Rosh Pinah mine. The line will be erected on compact cross-rope towers – the same method of construction used on the interconnector line.
The line is crossing the rugged Huib-Hoch plateau, which contains a variety of unique, uncatalogued and vulnerable flora, for which special precautions and protective measures are being taken. As part of the contract conditions as determined by the environmental management plan drawn up by NamPower’s environmental consultants, a suitably qualified botanist has to accompany the Alstom team. The botanist spent several weeks marking out the vegetation and agreeing routes. When a rare species of plant lay directly in the path of the new line, the route was altered.
There are no habitable areas near the route of the transmission line and therefore no electricity and no water. Everything to support the hundreds of men working out in the desert has had to be brought in by tanker and lorry. The men are housed at tented camps, spaced some 50km apart, in the desert. ‘Dinner’, ie livestock, mainly comes into the camps ‘on the hoof’.
Teams of men carrying out everything from route clearing, concreting, the pre-assembly of towers, pulling the line into place and commissioning, move between the camps. Every two weeks, the men are shipped back to civilisation for a break from desert austerity.
The terrain across which the line is to be established varies between about 1500m above sea level at the highest parts of the Huib-Hoch plateau to about 600m altitude in the open plains. The climate is severe, and workers have already had to put up with sleet and snow on the plateau while at the other extreme temperatures are expected to exceed 40°C at times, with rain extremely scarce.
Helicopters
Most of the Huib-Hoch is inaccessible, except on foot. To overcome such problems and to comply with environmental constraints, the team used a helicopter. Everything used in the mountainous region was flown in. With the helicopter costing some £2500 per hour, a dedicated engineer was involved in planning every working minute of the helicopter’s use.
The combined labour force engaged on the contract, which is scheduled for completion by end-January 2002, will peak at about 480 people. Several workers employed for the interconnector contract previously will be re-engaged. Others will be drawn from southern Namibian communities in the areas where the power lines are being erected. In addition, at the peak of construction activity, some 1500 people will be employed at the Skorpion site. Anglo American’s investment in the mine and refinery amounts to some N$3.5 billion.
