Construction World

Work on Durban’s Northern Aqueduct Augmentation (NAA) is gaining momentum with the fifth phase due to begin construction in August 2017.

Northern Aqueduct schematic pgPhase 5 comprises a new 1 200 mm diameter continuously welded steel high pressure pipeline stretching from Durban Heights Reservoir in Reservoir Hills to Duffs Road and an incrementally launched reinforced concrete bridge over the Umgeni river.

Ednick Msweli, head of eThekwini Water and Sanitation (EWS) 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 would be exacerbated by on-going development to the north of Durban which was essential to job creation and economic growth in the region.

Augmentation is necessary as the existing NA system, a network of potable bulk water supply pipelines that serves 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.

The entire NAA Phase 5 is expected to be completed by December 2019.

Martin Bright the project manager said that pipeline route investigations were complete and the Engineering Consultants, Bosch Projects have completed the detail design stage. Key challenges 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.

Bosch Projects, said that a thorough investigation had been conducted to identify various potential pipeline routes. Each one was carefully scrutinized and the preferred route that would promote ease of construction whilst reducing disruptions to members of the public and traffic, minimising road and environmental rehabilitation, and lessening the relocation of existing services, had been selected.

The design engineers located the pipeline to avoid rerouting as many existing services as possible and to minimise crossings of main high traffic roads and railway lines. However, several were unavoidable.

Fortunately, pipe jacking (i.e. tunnelling) by inserting a large diameter concrete pipe sleeve under roads and railway lines and then installing the steel water pipeline through the concrete sleeve would minimise disruptions.

Where this could not be done, the contractor (to be appointed shortly) would institute a traffic management plan to minimise traffic disruption and reduce inconvenience to residents and road users.

In addition to the pipeline itself, a concrete pipe bridge will be constructed 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 constructed on a similar alignment to the previously collapsed steel suspension bridge and adjacent to the existing pipe bridge, approximately 9,6 km from the river mouth. The level of the bridge deck has been 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 said that a river diversion works would be needed to cater for the river flow during piling and construction of the bridge sub-structure.

Bright said that environmental rehabilitation would be required during and after construction. EWS has appointed Gibb as the independent environmental consultants and impact assessors for this segment of the NAA.

Environmental challenges are expected to include wetland and riparian crossings, wooded-grassland crossings, biophysical impacts and social impacts, amongst others. Gibb has developed a comprehensive Environmental Management Programme which includes a Plant Rescue and Rehabilitation Plan (PRRP) to cater for these.

*The Northern Aqueduct project has been designed and is being monitored by Bosch Projects.

More information

The pipeline commences from the tie-in chamber at Pridley Road in Reservoir Hills and then traverses Mount Batten drive for approximately 100 m. It is anticipated that one lane may have to be closed in order to facilitate construction.

The pipeline then goes down to Battersea Avenue and proceeds along the back of the residential cadastral boundary located on Battersea Avenue/Middlemiss Crescent from where it descends into the Umgeni Valley.

After crossing the Umgeni River, it proceeds through the D’Moss open space area, crosses Newlands West Drive and then follows a valley line up to Sooklall Drive.
The pipeline then runs within Sooklall Drive for approximately 130 m before traversing another D’Moss area to reach the M21 (Inanda Road).

It then continues along Marbleray Drive where one lane may be affected by the necessary construction activities. From the end of Marbleray Drive, it runs parallel to the overhead power line servitude for roughly 2 km.

From there, it will move into John Dory Drive where one lane is expected to be affected. The pipeline deviates from the electrical servitude at Sweetpea Close to run along the back of Avoca Hills and then crosses the Transnet Railway Line twice before crossing Lark Road and the M25 (Curnick Ndlovu Highway) to reach the tie-in chamber on Duffs Road.

It will not be possible to indicate any specific dates as to when these areas will be affected until the detailed construction programme from the appointed contractor has been approved.

Contact Construction World

Title: Editor
Name: Wilhelm du Plessis
Email: constr@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

Title: Advertising Manager
Name: Erna Oosthuizen
Email: ernao@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

 
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