Construction on the fifth phase of Durban’s Northern Aqueduct Augmentation project is set to begin in August, eThekwini Water and Sanitation (EWS) said earlier this month.
Phase 5 comprises a new 1 200-mm-diameter continuously welded steel high-pressure pipeline, stretching from the Durban Heights reservoir, in Reservoir Hills, to Duffs road and an incrementally launched reinforced concrete bridge over the Umgeni river.
EWS head Ednick Msweli explained that, although there was sufficient water to meet current needs, it could not be delivered efficiently to areas where it was needed most. This was exacerbated by ongoing development to the north of Durban.
Augmentation is necessary, as the existing Northern Aqueduct system – a network of potable bulk water supply pipelines that serve the north-eastern portion of eThekwini north of the Umgeni river, south of the Ohlanga river and east of Ntuzuma, and conveys potable water from Durban Heights Waterworks to terminal reservoirs that serve residents and businesses – has reached maximum flow capacity.
Phase 5 will benefit Newlands, KwaMashu, Phoenix, Cornubia, Waterloo, Umhlanga and Durban North and is expected to be completed by December 2019.
Project manager Martin Bright said pipeline route investigations were complete, with engineering consultancy Bosch Projects having also completed the detailed design stage.
The project is not without challenges, which include constructing the pipeline through densely populated built-up areas, traversing major roads and railway lines, dealing with existing buried municipal services and rehabilitating environmentally sensitive areas.
However, pipe jacking by inserting a large-diameter concrete pipe sleeve under roads and railway lines and then installing the steel water pipeline through the concrete sleeve will reduce disruptions.
Where this cannot be done, the contractor, which is still in the process of being appointed, will institute a traffic management plan to reduce traffic disruption and inconvenience to residents and road users.
In addition to the pipeline itself, a concrete pipe bridge will be built across the Umgeni river above the 1:100 year flood line. This will comprise a reinforced concrete box type bridge cross- section, which will be incrementally launched and supported on five solid concrete piers, and will cross the Umgeni river adjacent to the existing pipeline.
Bright said the Umgeni river pipe bridge crossing was undoubtedly the most interesting and challenging part of the project.
The new bridge will be built on a similar alignment to the previously collapsed steel suspension bridge and adjacent to the existing pipe bridge, about 9.6 km from the river mouth.
The level of the bridge deck was based on a detailed hydrological flood assessment of the Umgeni river at a height that is above the regional maximum flood level.
A spokesperson for Bosch Projects said a river diversion works would be needed to cater for the river flow during piling and construction of the bridge substructure.
Environmental rehabilitation would be required during and after construction, with EWS having appointed Gibb as the independent environmental consultancy and impact assessor for this segment of the project.