An extensive project to refurbish both the Cape Flats 1 and Cape Flats 2 bulk sewer lines has commenced at an estimated cost of R539 million overall, with R133 million budgeted for this financial year alone. A total of 28 kms of pipeline is being rehabilitated, making this the largest project of its kind undertaken in South Africa.
Work is underway at various sections of the Cape Flats 1 (CF1) bulk sewer line to refurbish the 14 km pipeline, which ranges from 1050mm to 1450mm in diameter – one of Cape Town’s largest sewer systems.
Once the CF1 refurbishment has been completed, work will begin on the adjacent Cape Flats 2 (CF2) bulk sewer, which ranges from 1500mm to 1800mm in diameter. In total 28km of pipeline and approximately 331 manholes will be rehabilitated.
At the Pelican Park section a team, with the help of a 90kg robotic crawler, is currently inspecting the inside of the sewer to determine which sections should be prioritised for refurbishment. A robotic crawler is a remote controlled vehicle that profiles the inside of the pipeline by recording, among other things, the ovality at different points along the way. Ovality refers to deviations from perfectly circular measurements inside the shaft, which in turn tells the engineers the extent to which gases have corroded the inside surface of the pipe. This data is then used to determine the best – most affordable, effective, and efficient – method of refurbishing the different sections of the pipe.
At four meters below ground, and with a range of corrosive gases that are present in sewers, the work can be dangerous and requires careful and precise handling.
Once positioned by an intensively trained team member, the robotic crawler travels along the base of the pipeline, recording footage and measurements and transmitting diagnostic data by means of a laser beam to the processing system, visible on monitors in a specialised van above ground.
Before this aspect of the work could commence, the sewage flowing through the line had to be diverted to the larger adjacent CF 2 line, allowing the teams to clean the system of built up materials.
During four months of cleaning this section of about 2km, more than 600 tons of rags, silt, sand, grease, bricks, cutlery, animal carcasses and more were removed. All of these are illegal to dispose in sewers, and contribute to blockages and overflows that damage the health of our communities.
Once the inspections have been completed and the relative corrosion of different points of the line are known, structural rehabilitation of the now-clean pipe can begin.