Final DN 1200 pipeline connecting the DN 1470 diameter pipes that were pipejacked crossing Macassar Road to the Macassar Waste Water Pump Station.
Laying a new sewer line comes with multiple challenges, more so when in the midst of a developed area: environmental concerns, traffic, and inconvenience to communities, and more. The Black-Mac project in Cape Town had a multitude of professional players to ensure that carrying out the necessary work considered all of these. The main contractor for the construction of the new Black-Mac Outfall Sewer was Afriline Civils.
Stephan Kleynhans, Aurecon technical director in the company’ s water unit and project manager for the Black-Mac Outfall Sewer project, explains the motivation behind installing the new pipeline.
Project motivation
The Black-Mac sewer runs for a few kilometres upstream of the Macassar pump station, says Kleynhans, and,“ It picks up some of Blackheath, Blue Downs, Croydon, and Macassar’ s sewerage. It was constructed in the 1980s and it discharges at the Macassar pump station.
“ Along the Black-Mac sewer, there was a screening station that was in a state of disrepair, so what happened was that the City diverted flow from the Black-Mac sewer to the Zandvliet Waste Water Treatment Works( ZWWTW).
But this resulted in the ZWWTW becoming overloaded, as the population increased,” Kleynhans explains.
When Aurecon was appointed for the upgrade of the overloaded ZWWTW, it was also tasked with recommissioning the Black-Mac screening station and to undertake a condition assessment of the existing outfall sewer.
From the screening station to the Macassar pump station comprises about 8km of pipeline. After conducting CCTV inspections of the entire length of the pipe, structural techniques were used to assess the remaining life of the existing sewer.
“ It’ s roughly 4km from the screening station to where we crossed the Eerste River with the siphon,” Kleynhans explains and adds,“ That length of pipe still had a reasonable remaining life, so it was agreed that we will just reline that section. The section from the Eerste River to the Macassar pump station, however, was problematic in terms of remaining life, as the wall thickness of the old asbestos cement pipes had eventually eroded or corroded. Along with this, future developments were planned in the area that would feed into that sewer, so increasing the hydraulic capacity was required.”
For this reason, the 4km section from the Eerste River to the Macassar
While the project started during the peak of the Cape drought, in November 2016, imposing water restrictions on the project that also required dust control in the Cape winds, Kleynhans believes that the drier conditions made it easier for pipe installation. contributor innovations industry debate environment infrastructure municipalities
Photos by John Reed, Afriline
DN 1200 diameter pipeline constructed nine metres deep between the‘ Big Rock’ along Macassar Road and the adjacent houses in Macassar. networking
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