Integrated infrastructure delivery company AECOM was a winner in the category projects with a value greater than R250 million for the Cape Flats 3 Bulk Sewer – Phase 2 (CF3-2) project at the 2018 CESA Aon Engineering Excellence Awards on 15 August.

Designed by AECOM and constructed by CSV Construction, the project is the final link in the City of Cape Town’s strategic Cape Flats bulk sewerage system. CF3-2 is a 1 000-mm-diameter ductile iron rising main, with a design capacity of 1.3 m3/s. This project stands out because of its innovative design aspects, such as the inclusion of a barometric loop with vortex drop structure, and state-of-the-art construction methods, including micro-tunnelling.

The 5 km route traverses a densely-populated area, where sections of the pipeline needed to be constructed through busy roadways and in close proximity to existing buildings and services. Micro-tunnelling was used to install 1 200 m of pipeline, using a Herrenknecht tunnel boring machine (TBM) – the first of its kind to be owned and operated by a Southern African company.

The recent innovation of ductile iron jacking pipes meant that the pressurised product pipe could be installed using the TBM without the need for a sleeve. This was a cost-effective and technically-efficient solution that was employed for the first time in South Africa for this project.

Going into construction, Tim Pollard was appointed as the Engineer. Project Engineer Timothy Hotchkiss conducted all the day-to-day contract administration and, as the engineer’s representative, was responsible for the quality control on-site, assisted by Sibusiso Mahlangeni and Franco Taljaard. AECOM’s technical team was supported by Nicole Bates, Environmental Control Officer, and Gillian du Plooy, Health and Safety Officer.

Cape Town’s existing twin Cape Flats Bulk Sewers (CF1 and CF2), constructed in the 1960s, serve an 8000 ha area of the Cape Flats, as well as providing a link for transfer of flow between two bulk wastewater catchment areas. However, these are currently severely dilapidated and silted up, and cannot perform their strategic function adequately.

Completion of CF3-2 greatly increased the system’s capacity to allow rehabilitation work to be undertaken on the old sewers, as well as providing sufficient capacity in the system for at least the next 50 years.

This year’s CESA Aon Engineering Excellence Awards attracted 50 submissions, and included a special Lifetime Achievement Award in celebration of Nelson Mandela’s centenary. “Engineers create legacies. Each time you change the landscape, you change history,” CESA CEO Chris Campbell stressed.

“The gravity and everlasting effect of an engineer’s work on a society should never be overlooked. As winners, you have been a part of making history, and sewing your craft into the fabric of the societies you serve,” Aon South Africa Business Unit Manager Meggyn Marot added.