IMIESA talks to Tente Tente, divisional manager: Phase II, Lesotho Highlands Development Authority, about the roll-out of one of the region’s most significant water projects, vital for South Africa’s Gauteng province.

Please comment on the preparation works for Phase II.

As is the case with major infrastructure projects of this nature and magnitude, a significant amount of planning and preparation has to be completed before there is evidence of the physical project activities on the ground. This planning and design phase has now been completed. The next stage is groundfield infrastructure: for example, the roads, power lines, and construction village. That all comes beforehand, and we call it advanced infrastructure.

The main works, which entail the construction of the dam and the transfer tunnel, are the next stages. We are looking at starting construction of the main works towards the end of 2019 or early 2020.

What are the main milestones so far?

From the end of 2014 and through 2016, we have mainly been concentrating on the appointment and mobilisation of the consultants responsible for the design of all the advanced infrastructure elements. These consultants will in turn prepare the tender documents for the various construction programmes.

By mid-2017, we expect to start advertising the first tenders for the construction of the advanced infrastructure works.

The critical elements are clearly the dam and the tunnel. The dam tender closed in December 2016, and we’re currently busy with the evaluation process. The same methodology applies to the tunnel tender, which closed in January 2017. Once these are concluded, we can finalise the consultant appointments.

How will Phase II connect with Phase I? Do they join up at some point?

Phase I, completed in 2003 and inaugurated in 2004, was split into phases 1A and 1B. The main physical features of Phase 1A are the 185 m high Katse Dam, the 45 km transfer tunnel from Katse to the 72 MW Muela hydropower station, the Muela hydropower station and appurtenances, and the 37 km delivery tunnel across the border into South Africa, where the outfall is the Ash River near Clarens, Free State.

The key components of Phase 1B included the construction of the 145 m high Mohale Dam, and the 32 km transfer tunnel to the Katse Dam. Both phases also involved the construction of infrastructure such as tarred roads, bridges, camps, health
facilities, as well as environmental and social programmes.

On completion of Phase II, the new Polihali Dam will connect to Katse via a
new 38 km tunnel. From there onwards,
the water will pass through the existing Phase I system, generating hydroelectric power in the process.

What form will the Polihali Dam take?

Polihali will be a concrete-faced rockfill dam. The design will be similar to Mohale Dam, which has a 145 m high wall. However, the new dam will be higher by approximately 20 m.

Polihali will have a crest length of 915 m with a width of 10 m. The live storage capacity will be around 2 322 million cubic metres, with a reservoir surface area at FSL of 50.4 km².

When will full commissioning of the Polihali Dam take place?

We are looking at a five- to six-year programme. So, by 2025, we should be able to fully commission the water transfer component. According to the 2009 Phase II feasibility report, the full yield is expected to be utilised by approximately 2030.

What will be the combined capacity once Phase II is completed?

The current capacity for Phase I is around 25 m³/s. Phase II at full capacity will add an additional 15 m³/s, so we are talking around 40 m³/s in terms of annual yield. Phase I currently delivers around 780 million cubic metres per annum to South Africa. Phase II will increase the yield to 1 270 million cubic metres annually.

What plans are in place for the proposed Kobong 1 200 MW pump storage scheme in Phase II?

This is a solution that was identified during the feasibility study. However, the findings were not conclusive. Technically, the potential is definitely there, but Lesotho needs to carry out further studies to confirm its viability. Further hydropower feasibility studies are in progress. These include geotechnical investigation at the site, a market study to confirm who the buyer of surplus power would be, an integration/transmission study for the powerline that will evacuate and deliver the power to its intended destination, and the conclusion of a power purchase agreement and power sales agreement to ensure that the project
is bankable.

After commissioning of Phase I, Lesotho was self-sufficient. However, due to positive macroeconomic growth, current demand has outstripped supply regarding the existing hydroelectric plant. That’s why it’s important that Phase II augments what Lesotho already has, so that electricity imports from South Africa can be reduced. So, aside from the proposed pump storage, we are investigating where the existing Lesotho Highlands infrastructure can be used to generate more power for Lesotho.

How will Phase II impact positively on Lesotho’s GDP?

Phase I had a very positive impact on Lesotho’s economy, and we are excited about the further potential both during construction and after the completion of Phase II. Further improvements in infrastructure will enhance ease of travel in the mountains, promoting commerce and especially tourism, which is one of our major GDP contributors.

Will there be a Phase III?

That will be informed by the Planning Department within South Africa’s Department of Water and Sanitation and an agreement between the parties (Lesotho and South Africa). Once Phase II is fully operational, the future water demands and requirements will become clearer. This will be strongly influenced by the water demand projections in South Africa, and more specially, the growth projections anticipated by the Gauteng province, the primary water user of the scheme and currently Africa’s largest economy in terms of GDP.

In the meantime, we believe that during the course of 2017, we will see earthmoving machines breaking ground on one of the first construction projects in Phase II. Everyone has been waiting for this and we are confident that Phase II will be a huge success for both Lesotho and South Africa.