The Roads Authority of Namibia appointed VKE Namibia as consulting engineers to design and oversee the implementation of the Windhoek – Hosea Kutako International Airport Freeway upgrade to dual carriageway standards. Phase 1 of this project commenced at the MR49 Mandume Ndemufayo Avenue / Kupferberg intersection which was substantially altered with a new bridge over the freeway linking Mandume Ndemufayo Avenue with the C26 / Kupferberg Road, together with accompanying on- and off-ramps.
At the “Mandume Interchange”, the new freeway and these on- and off-ramps were constructed over some of the City of Windhoek’s water supply pipelines to- and from their Pioneers Park Reservoir, which is an important storage reservoir and distribution hub in the context of Windhoek’s water supply system. This reservoir provides storage / supply for the Pioneers Park, Rocky Crest, Academia and Hochland Park residential areas.
VKE approached LCE for assistance with the specialist pipeline design, which was carried out by LCE, together with KCE. This project consisted mainly of the realignment of a 450 mm nominal diameter pump line to the reservoir and a 700 mm nominal diameter supply line from the reservoir, in parallel, over some ~400 m total length, including a total of some ~110 m through three separate culverts, with these two pipelines laid in parallel. Some ~130 m of 200 mm nominal diameter uPVC and HDPE and some ~250 m of 250 nominal diameter uPVC and HDPE pipes also needed to be realigned, including ancillary works such as scour valve and water meter manholes, etc. A particular challenge with the main portion of the works was the need to thread the 450 and 700 mm nominal diameter pipelines through misaligned culverts, needing several bends in both the horizontal and vertical planes, requiring large thrust blocks where working space was rather limited. A further feature of the pipelines was the incorporation of different pipe materials; purpose-made steel bends, DCI pipes (450 and 700 mm diameter) underground and lighter uPVC (450 mm nominal diameter) and GRP pipes (700 mm nominal diameter) inside the culverts. As far as we can ascertain, these are the first GRP pipes to be used in the potable water distribution network of Windhoek and therefore also the first “above ground installation” of GRP pipes (albeit inside a culvert) in Windhoek.
The sequencing of construction activities needed to be carefully planned and coordinated with the City of Windhoek and all the scheduled cut-ins and connections to their existing pipelines were completed without any interruption in water supply to residents. Construction of the thrust blocks, pipelines and their connections also needed to be executed to exacting tolerances.
LCE conducted the designs, together with KCE, and LCE oversaw the tendering of the pipeline supply and the pipeline construction works as two separate contracts and conducted the construction supervision and contract administration associated with these works, which were successfully tested and handed over to the City of Windhoek in early 2022.