Mott MacDonald was appointed by Lesotho Highlands Development
Authority, in joint venture with Lahmeyer International, to provide
consultancy services for the 'Muela hydropower station which forms
the power generation component of the £1.5 billion Lesotho
Highlands Water Project. The £70 million hydropower station is the
first electric power generator in the Kingdom of Lesotho, making
the country self-sufficient in electricity. The project –
commissioned in 1998 – was financed by the Government of Lesotho,
African Development Bank and the European Development Fund.
The joint venture's remit included all civil, mechanical and
electrical engineering associated with the power station. The first
step was a thorough review of the tender design which resulted in
extensive changes reducing the cost of the works by 10%, while
improving the speed of response of the power station to load
changes. This was followed by detailed design, preparation of
working drawings and construction supervision.
World’s longest headrace tunnel
Water will reach the underground power station via a 45km
headrace tunnel which is the longest of its kind in the world. The
maximum 300m hydrostatic head is used to drive three 24MW machines
located in a cavern 60m long by 15m wide by 30m high, excavated in
the Clarens sandstone. The water then discharges along a 1.4km
tailrace tunnel to ’Muela tailpond, formed by a 55m high double
curvature arch dam across the Nqoe River.