Concor-Nthane Brothers Joint Venture (CNBJV) overcomes high-altitude challenges on Polihali Bridges in Lesotho

Practical completion of the Mabunyaneng and Khubelu bridges on 31 July 2026 marks an important milestone in the development of resilient transport infrastructure in Lesotho’s mountainous Mokhotlong district. Constructed by the Concor–Nthane Brothers M&K Joint Venture for the Lesotho Highlands Development Authority (LHDA), the bridges provide permanent access along the national A1 highway, replacing the existing low-level river crossings that will be inundated by the future Polihali Dam reservoir. The contract encompasses the construction of the 270-meter long Khubelu Bridge (comprising nine 30-meter spans) and the 120-meter long Mabunyaneng Bridge (four 30-meter spans), alongside approximately two kilometers of A1 Road realignment. Both structures stand more than 2,100 meters above sea level in steep, highly variable mountain terrain.

According to CNBJV’s Contracts Director Jaco Verreynne, delivering infrastructure of this scale in an extreme alpine environment required embedding agility into the project’s strategic planning from day one.

“Executing major civil works at this altitude demands complete technical flexibility,” says Verreynne. “By adapting our engineering approach and logistics to match site conditions and severe weather, we have maintained continuous progress while keeping safety at the forefront.”

Early geotechnical site investigations during piling operations revealed that competent founding material lay deeper than originally anticipated. Engineers promptly adapted the foundation design to incorporate deep friction pulse piles, ensuring structural load transfer through surrounding rock and soil layers. Additionally, ground instability along the road approaches led to the original design of the Mechanically Stabilized Earth retaining wall (MSEW) being changed.

Operational execution on site required overcoming significant river-channel and heavy-lifting constraints. To construct piers within active waterways safely, temporary cofferdams and causeways with culverts were installed to divert river flow without disturbing local ecosystems.

CNBJV’s Project Manager Lebo Matlala highlights that one of the most demanding phases involved the fabrication, transport, and installation of the project’s 91 precast concrete beams, each measuring 30 meters in length and weighing 51 tons.

“Transporting 51-ton beams along steep, narrow mountain roads required meticulous logistical planning,” says Matlala. “Because single-crane maneuvers were impossible in this terrain, we designed tandem lifting operations using two 275-tonne truck-mounted cranes in partnership with Johnson Cranes and Jacob’s Transport.”

Specialist partner FB Cranes set up and maintained a dedicated gantry crane system at the on-site Precast Yard to handle precast beam fabrication and loading. To maintain concrete curing standards during sub-zero winter temperatures, batching water was pre-heated in storage tanks, and enclosed curing environments with industrial space heaters were established around fresh pours.

Further safety innovations included suspending bridge deck formwork directly from the installed precast beams of the bridge structures, drastically reducing high-risk work within active riverbeds.

Environmental controls were integrated across all operations. Dedicated on-site wastewater treatment facilities treated construction water for reuse in dust suppression, while natural bioremediation techniques were deployed on site to treat hydrocarbon-impacted soils. To overcome the 200 km supply distance from commercial suppliers, the joint venture partnered with National Asphalt to establish a dedicated asphalt plant directly on site.

The project has also delivered substantial economic benefits to the Mokhotlong District. At peak construction, the workforce comprised approximately 330 hourly paid workers and 45 supervisory staff, predominantly Basotho nationals. Local procurement significantly exceeded contractual targets across subcontracts for earthworks, security, and site services.

Furthermore, the joint venture provided hands-on training for 12 graduate engineers (10 from Lesotho and two from Concor’s Graduate Mentorship Programme), building lasting technical capability for the region.

“Infrastructure projects create opportunities that extend far beyond the physical structures,” concludes Matlala. “Equipping young engineers and local subcontractors with experience on a mega-project of this complexity builds sustainable capability that benefits the industry long after construction ends.”