The Lesotho Highlands Development Authority (LHDA) says the Polihali dam construction tender process marks the start of the final construction phase of the water transfer component under the second phase of the Lesotho Highlands Water Project and follows on the tender, issued in May, for the construction of the Polihali Transfer Tunnel.

LHDA announced the launch of the tender on August 6 and tender documents were made available for download or collection from the LHDA from August 9. Interested and suitably qualified tenderers have until November 12 to submit their proposals. A virtual pre-tender meeting will be held on August 23, with a site visit scheduled on August 31.

“The launch of the construction of the main works open tender is the culmination of years of planning and hard work of dedicated design and procurement teams.

"Our objective with this final procurement stage is to attract suitably qualified companies with the capability, experience and resources to undertake the construction of the Polihali Dam within the set timeframes and to the required quality,” said LHDA CE Tente Tente.

The flow from Polihali will increase the volume of water to be transferred from the Katse dam, the centre point of the Lesotho Highlands Water Project Phase I. The current water transfer volumes to the Gauteng region of South Africa will incrementally increase from 780-million cubic metres a year to 1 270-million cubic metres a year.

This will also simultaneously increase the energy generated by the ‘Muela hydropower plant from about 500 GWh/y to 800 GWh/y - a further step in the process of securing an independent power supply to meet Lesotho’s domestic needs.

The Polihali dam construction procurement is launched as construction activity on ten advance infrastructure contracts progresses steadily, with some contracts expected to be completed this year.

Construction of the 33 kV transmission line, which will provide a temporary power supply to the Polihali village, was completed in 2020.

Work on the 132 kV line has advanced with the construction of access roads, 91 tower foundations and the erection of 84 towers out of a total of 93. The Polihali and Katse civil works, access roads, pipe laying for potable water and sewerage lines, have been completed and construction on the main access roads is underway. Excavation on the Polihali diversion tunnels is close to completion with breakthrough on both tunnels expected in the second half of August.

More than 14-million cubic metres of rock which will be quarried locally within the dam basin will be compacted to form the embankment. The Polihali Dam infrastructure also includes a 43-m-high, 600 m crest-length CFRD saddle dam, a spillway and a compensation outlet.

According to the current master programme, water delivery is scheduled for 2027/28. Timeous construction of the dam and transfer tunnel is critical to meeting the water delivery deadline of the project.