Challenge

The Ha Mpiti to Sehlabathebe road upgrade will traverse Lesotho from east to west and forms part of a future ring-road that will link the southern town of Qachas Nek with Thaba Tseka. Lesotho is a mountainous, landlocked enclave in Southern Africa. Ha Mpiti to Sehlabathebe road will provide much improved connectivity for local communities whilst boosting tourism investment in Sehlabathebe National park – the only world heritage site in Lesotho.

The mountainous environment is characterised by steep river valleys which cross an ever-changing geology of sedimentary rock layers until it climbs into the basaltic rocks. The road starts at approximately 1,700m and climbs to 2,400 m above sea level.

Depending on the altitude, the climate in the highlands includes a temperature range from an average minimum of 5°C (July) to an average high of 28°C (January/December).  The minimum temperatures often fall to below 0°C in the winter months in the higher altitudes.

Solution

The project is to upgrade a 91 km rural road from a gravel standard to a surfaced (asphalt) standard.  The project scope of work has included the economic feasibility study, environmental and social impact assessment, preliminary and detail design, tender documentation and supervision of the building contractor. SMEC was initially appointed to undertake feasibility studies and design in 2012.  The design was completed in 2014 with the contractor (Qinjian Group. Co. Ltd) eventually appointed in 2018.  Construction commenced on 23 January 2019 and completed in March 2024.

The pavement design is adapted to resist the effect of freeze-thaw cycles and frost heave. Using the Lesotho pavement design guidelines, the depth of frost penetration was estimated and frost resistant materials were specified for layers anticipated to be affected by frost penetration.  The base layer was specified as a bitumen stabilised crushed stone material where the presence of bitumen makes the layer more resistant to water ingress.

The subbase was specified as a crushed stone material containing less than 3% of material finer than 0,02 mm.  This specification is to reduce capillary action in the material from “sucking” moisture into the subbase from the supporting subgrade. Both specifications minimise the presence of excess moisture entering these upper pavement layers during the pavement design life, which, during repeated cold cycles falling below 0 °C, would freeze, expand and cause these layers to heave and lose shear strength when the temperatures increase again.

Through the project, the main contractor created employment opportunities for Lesotho nationals which increased up to 793 people (686 men and 107 women) in February 2023.  These included 350 unskilled labour positions and the balance were skilled labour, operators/drivers and supervisors/management personnel.

Impact

SMEC has provided value to the Lesotho Roads Directorate, from inception through to the construction phase of the project. The Ha Mpiti to Sehlabathebe road will provide all-weather surfaced road access for 12 villages to Qachas Nek, the main town in the district (with a hospital and commercial centre) and from there to the capital city of Maseru.  It will provide access to the Sehlabathebe National Park which will promote tourism and forms part of a strategic ring-road that runs along the south-eastern border of Lesotho with South Africa. Practical completion was achieved in March 2024.