Civil Engineering November 2022 | Vol 30 No 10

KwaZulu-Natal province in South Africa and Mokhotlong in Lesotho. Closures not only cut off the surrounding impoverished communities from essential services but also resulted in a loss of tourism revenue. In 2005, Lesotho and South Africa signed a cooperation agreement to im- prove commercial, social, and economic opportunities and accessibility between the SADC countries. Included in that agreement was the upgrade of Sani Pass to improve road drainage, prevent gravel loss, and limit erosion caused by high- intensity storms and flooding. As per the agreement, South Africa will surface the P318 up to Sani Top and Lesotho will surface the road to Mokhotlong, with the ultimate goal of having a surfaced road all the way to Maseru. The project comprises three phases: Q Q Phase 1 : From km 0.0 (junction with Main Road P126 from Himeville) to km 13.6 (Good Hope Trading Post) Q Q Phase 2: From km 13.6 to km 25.0 (SA Border Post) Q Q Phase 3 : From km 25.0 to km 33.0 (summit at Lesotho Border Post) Phase 1 was completed approximately 12 years ago, Phase 2 was recently completed (the roadworks portion is included here), and Phase 3 is yet to begin construction. The client, the KwaZulu-Natal Department of Transport, required a cost- effective, aesthetically pleasing upgrade of the mountain pass route that would im- prove accessibility in most weather condi- tions. Importantly, construction would have to take place without restricting the movement of people or traffic. What’s more, the route’s location within a World Heritage Site imposed environmental constraints that had to be considered and addressed. DESIGN CONSIDERATIONS The section of the P318 in question begins at km 13.6 at an elevation of 1 577 m. It generally follows the southern banks of the Mkhomazana River as it climbs the escarp- ment in a series of steps with relatively long sections of moderate gradients interspersed with short sections of steep gradients. Temperatures in the Drakensberg range from -20°C to 35°C. The area’s climate is defined by high annual rainfall of 1 800 mm and severe storms in the summer months. Winter brings cold temperatures and snowfall, and the upper sections of the pass are frequently covered in ice. The existing gravel narrow track and drainage system could not handle the high-intensity runoff of water on steep gradients, resulting in excessive scour and gravel loss. Gravel is a non-renewable resource, and good quality gravel is espe- cially hard to come by in the Drakensberg. The eroded gravel eventually settles in local streams and rivers, particularly the Mkhomazana River, causing sedimenta- tion and pollution in the lower reaches and negatively impacting aquatic biodi- versity. Furthermore, the dust created by passing vehicles negatively impacted the biodiversity of the adjacent vegetation. Because the Sani Pass is located within a World Heritage Site in an environmen- tally sensitive area, it could potentially impact the: Q Q Biophysical environment (botanical, fauna, and flora) Q Q Aquatic environment Q Q Socio-economic environment (tourism and aesthetics) Q Q Cultural heritage environment. This had several implications for the design and construction of the roadworks. Noteworthy aspects of the project include: Q Q The road was designed to look like it “fits in” with its surroundings to pre- serve the unique heritage of the area. Q Q Because of the rugged terrain and narrow width of the pass, the road had to be designed and built in half widths to ensure that the work activities stayed within the footprint of the already-built road. This was carefully monitored and strictly enforced by the site team to reduce the impact on the sensitive adjacent ground cover and the area’s Civil Engineering November 2022 13 The road follows the southern banks of the Mkhomazana River as it climbs the escarpment The Sani Pass is a critical trade artery connecting South Africa and Lesotho