Spearheaded by the City of Cape Town, the R796 million Cape Flats Bulk Sewer Rehabilitation Project kicked off in 2020. As a pioneer in pipeline construction with an international footprint, Mainline was chosen as a contractor on the project. Ingerop are the Employers Agent for the City of Cape Town as well as the consulting engineer for the project and their innovative, solutions focused approach was critical in the success of this project according to Mainline.

On completion of the various works packages awarded to date, Mainline will have fully rehabilitated over 10 km of bulk sewer pipeline utilising the Spirally Wound Pipe System. Mainline has so far cleaned, profiled, and CCTV inspected over 16 km of pipeline.

The project also includes rehabilitating more than 70 manholes, making it a thorough infrastructure renewal initiative. The company’s proven track record in delivering complex infrastructure solutions, while effectively problem-solving challenges that present themselves during intricate contracts stood the company in good stead during this massive undertaking.

Tackling a 60-year infrastructure crisis

Serving as the lifeline for nearly one million residents across 300 000 households, the Cape Flats twin bulk sewers have supported the region’s sanitation needs since their original construction in the 1960s. This massive network, spanning 8 000 hectares with pipes ranging from 1 000 mm to 1 800 mm in diameter, faced critical functional challenges, including extensive sediment accumulation, severe structural deterioration and hazardous groundwater exfiltration from decades of continuous use.

With population growth and housing density showing no signs of slowing down, the need for an overhaul was critical. A project of this scale has substantial design considerations and on commencement, this intensified when initial plans to utilise the adjacent sewer line as a bypass during rehabilitation were challenged due to the significant build-up of sediment, debris and unexpected blockages. Traditional cleaning methods such as high-pressure jetting was insufficient, necessitating brave teams to head underground and undertake hazardous confined-space operations spanning many months.

Despite these obstacles, Mainline’s engineering prowess and commitment to service delivery ensured uninterrupted service, managing an impressive flow rate of 84 000 litres per hour, 24-hours a day for the duration of the Works Packages.

Technology and skills transfer

Prior to the commencement of the contracts, Mainline engaged with other specialists in the field of trenchless rehabilitation, specifically in the disciplines of Spirally Wound Pipe (SWP) Liners, as the bulk of the pipeline rehabilitation would be undertaken utilising this technology.

Spirally wound pipe lining is a trenchless method of rehabilitating damaged or deteriorating pipelines, such as sewer or stormwater systems, using a spirally wound pipe liner. The Spiral Would Pipe SWP Lining consists of a single, continuous strip of PVC, which is spirally wound into the existing pipeline via a high-tech winding machine positioned in the base of an existing manhole or access chamber.

This process creates a single continuous PVC pipe in the existing host pipe. As the liner is inserted, it is unrolled and spirally wound into place, conforming to the shape of the existing pipeline.

When the flat profile is wound to the specified diameter and pipeline shape, it is simultaneously secured with a mechanical joint and a chemical weld, creating a durable liner that conforms to the existing pipeline. This results in a strong, smooth, and corrosion-resistant surface.

Spirally wound pipe lining offers a number of benefits over traditional pipeline repair methods, including reduced disruption to the surrounding area, faster installation times, and improved resistance to corrosion and wear. It is also a cost-effective solution for rehabilitating damaged or deteriorating pipelines, as it eliminates the need for costly excavation and replacement.

Additionally, spirally wound pipe liners can be customised to fit a wide range of pipeline sizes and shapes, making it a versatile solution for a variety of applications of the pipeline. This was the first time SWP Liners would be utilised at scale in the country. Therefore, Mainline partnered with the German SWP specialists, SWP Systems GmbH, who assisted them with the design and supply of the specific SWP system to be used on the Cape Flats projects, as well as providing technical support and training, both in Germany and South Africa.

Together with SWP Systems GmbH, Mainline procured and imported the specialist equipment and over 250 000m of SWP liner profile to be utilised on the Cape Flats Bulk Sewer Rehabilitation. Additionally, all staff were trained on the use of the Amphitec Vacuum Excavators as well as confined space training. Mainline also trained staff as safety, health and environment representatives, first aiders and flagmen.

Transforming communities: From crisis to award winning success

The impact of the Cape Flats Bulk Sewer Rehabilitation Project extends far beyond infrastructure. Between 2020 and 2024, this initiative generated over one million man-days of employment opportunities for local skilled and unskilled labour.

“The rehabilitation of the Cape Flats Bulk Sewer has had a huge impact on the surrounding communities, not only through the employment opportunities created, but with this comprehensive replacement of a severely deteriorated bulk sewer pipeline system – prior to the rehabilitation, blockages and dangerous overflows were a common occurrence,” notes Jared Smith, Mainline Contracts Manager for the project.

The transformation is remarkable – previously blocked lines operating at just 20% capacity have been restored to full functionality, promising decades of reliable service and full capacity operation. This flagship rehabilitation project, has also earned Mainline prestigious recognition, including the coveted Joop van Wamelen Award of Excellence, awarded by the Southern African Society of Trenchless Technology (SASTT).

Additionally, the City of Cape Town has further demonstrated its commitment to maintaining this revitalised infrastructure by investing in a fleet of 23 specialised jetting trucks, ensuring the longevity of this crucial urban system.

“Mainline is an undoubted dominant player in South African pipeline rehabilitation and the successful completion of these impressive SWP projects within budget and on time amplifies our capabilities and commitment to remaining a pioneering service provider,” concludes Smith.

Mainline is a specialist civil engineering contractor in the field of pipeline construction, the trenchless installation of underground pipelines and utilities, and trenchless pipeline rehabilitation and tunnelling in both the public and private sectors.