The Lesotho Highlands Development Authority (LHDA) has advertised a tender for the construction of a 38-km-long water-carrying tunnel – the Polihali Transfer Tunnel – and will shortly issue the tender for construction of the associated Polihali Dam as it continues its ambitious Lesotho Highlands Water Project.
The Polihali pair of projects anchors phase two of this complex infrastructure scheme designed to send mountainous Lesotho’s abundant water into neighbouring South Africa, but not before generating electricity with it as it departs.
"Our objective is to attract firms with experience in the construction of major underground works under complex geological and geotechnical conditions, diverseÂ environmental conditions, in remote areas and at high altitude," said Tente Tente, chief executive of the LHDA, in a press notice sent to GCR.
"Equally important is to attract firms that have impeccable records in delivering projects of this magnitude within budget and the set timeframes."
Construction companies have until 30 August 2021 to submit tenders, with information available on the LHDA website.
LHDA expects that tunnel boring and drill and blast methods will be needed to excavate the 5-metre-bore Polihali tunnel, which will transfer water by gravity from the to-be-constructed Polihali Dam reservoir to the Katse reservoir (pictured).
Water from the Katse reservoir, built in phase one of the Lesotho Highlands Water Project, travels through its own transfer tunnel to generate electricity at the ‘Muela hydropower plant before entering the Gauteng region of South Africa.
The new Polihali dam and tunnel are intended to boost the flow of water from Katse to Gauteng from 780 million cubic metres a year to 1.27 billion cubic metres a year, and to increase electricity generation at the ‘Muela plant.
A contract for the design and construction supervision of the Polihali Transfer Tunnel and its secondary structures has been awarded to a joint venture of Lesotho-based FM Associates and South African firms Zutari, Hatch Africa, Knight Piesold and SMEC South Africa.
LHDA said work on supporting infrastructure for the Polihali projects is progressing steadily.
Image: The new tunnel will feed the Katse reservoir, pictured here, which sends water to a hydropower plant before it enters the Gauteng region of South Africa (SkyPixels/CC BY-SA 4.0)Â