Civil Engineering November 2022 | Vol 30 No 10

40 November 2022 Civil Engineering T he upgrading and rehabilitating of the Omaruru River Bridge formed part of the greater project to up- grade the salt road between Swakopmund and Henties Bay (MR44), and the gravel road from Henties Bay to Uis to Kamanjab (MR76) in the Erongo Region of Namibia, to a bituminous paved road. The route forms an important link from the inland communities to the coastal towns, span- ning a distance of more than 400 km across desert terrain. Henties Bay is the closest community to the Omaruru River Bridge. Swakopmund is around 75 km away from Henties Bay and Walvis Bay is a further 35 km away. The bridge is a key feature on the route and was first constructed in 1980. However, after a mere 12 years, the bridge required comprehensive concrete repairs due to severe concrete damage to the structure. A further 23 years later, in 2015, the bridge was found to have deteriorated again to an extent which greatly compro- mised its structural integrity. HARSH LOCATION CONDITIONS Located approximately 2 km from the Atlantic Ocean, the deterioration of the Omaruru River Bridge can be attributed to the extremely harsh environmental conditions to which the bridge is exposed. The climate in this area varies from very warm and dry (when the wind blows from the inland of Namibia) to wet, misty and very cold, virtually marine conditions (when the wind blows from the ocean). This results in temperatures ranging from minima of 0°C to maxima of 45°C – among the harshest ranges on the planet. In addition to these environmental conditions, the approach road was a salt road, which had been sprayed with concentrated salt water. The combina- tion of the harsh environment and salt ingress into the structure created ideal circumstances for the inevitable chloride corrosion of the steel reinforcement. PARTNERING WITH LOCAL EXPERTISE Zutari, in joint venture with consulting engineers Bicon Namibia, was appointed for the detailed design, tender documen- tation, contract management and site supervision services of this project. Bicon Namibia was responsible for the material and pavement related services. The consultancy services related to the bridge work were assigned to Zutari. The overriding question for the Omaruru River Bridge was whether it would be SANRAL SA I CE 2022 Nat i onal Awards Category: I nternat i onal Upgrade and rehabilitation of Omaruru River Bridge, No. 435, in Henties Bay, Namibia WINNER International category KEY PLAYERS Client: Roads Authority Namibia Consultant: Zutari The Omaruru River Bridge