Due to increasing water demands, Umgeni Water has decided to augment the capacity of the ’61 pipeline system that feeds the greater Edendale area and the Outer West area of eThekwini Municipality.

The augmentation will also accommodate future supply to the Richmond and Thornville areas. It will be implemented by duplicating the existing single DN 800 pipeline in two stages – the first stage will be the construction of a DN 1300 steel pipeline between ED2 and ED4, and the second stage will be the construction of a DN 1100 steel pipeline between ED4 and Umlaas Road. Umgeni Water appointed SSI Engineers in 2008 to review the overall design of the ’61 pipeline system and to design and manage its augmentation.

Project description
The pipe supply for stage one between ED2 and ED4 was awarded to Group Five Pipe and the construction of the pipeline to Esorfranki Pipelines. This 4 km section of the pipeline traverses existing built up areas, and the working corridor which is severely constrained made handling and laying the new DN1300 pipes extremely difficult. The contractor has dealt with this and various other challenges during construction and the pipeline has been commissioned in February 2012.

Tenders for stage 2 of the pipeline closed in January this year, and Umgeni Water hopes to have a contractor on site by April 2012 at the latest. This 13 km section of the pipeline traverses private property and game farms, and although the working corridor itself is not too restricted, there is minimal access to and from the working front, which should present the contractor with some logistical challenges. The pipeline will be laid in a 120 m long DN 1800 jacked sleeve under the N2 at Umlaas Road, and will rise back to ground level in a 13 m deep vertical shaft, before discharging into a new inlet structure at the reservoir site.

In addition to the ’61 pipeline augmentation, Umgeni Water has provided for a future off-take to supply water to Richmond. The 30 km long DN 450 pipeline to Richmond and Thornville is being designed in-house by Umgeni Water, and the design of the booster pump station and reservoir has been done by SSI Engineers. The hydraulic conditions at the pump station are quite unique in that the suction head can vary by up to 60 m. To accommodate this, the pumps will be powered by variable speed drives and controlled via PLC with a complex operating philosophy programmed to protect the pumps from cavitation and the pipeline from transient pressures. Another feature of the pump station is the surge attenuation bladder tanks on both the downstream end of the very long suction main and at the head of the delivery pipeline. These are both accommodated within the pump station

Project status
The pipeline from ED2 to ED4 (stage 1) has been commissioned in February 2012 with the anticipated completion of the project in October 2013.

Project team
Client – Umgeni Water
Project Manager: Peterson Ndlovu
Contractors – Group Five Pipe
Esorfranki Pipelines
Consultant – SSI Engineers and Environmental Consultants
Project Manager: Darren van Rooyen