Civil Engineering October 2021 | Vol 29 No 9

S tellenbosch has seen consider- able growth over the past few years, which has placed immense pressure on its services infrastructure, including the bulk sewer network. These capacity challenges meant that regularly overflowing manholes and leaking pipes connected to the existing bulk sewers were contributing to high levels of pollu- tion in the Plankenbrug River. Several studies on the river’s water quality revealed E. coli counts far in excess of the accepted maximum limit for river water. Besides being devastating to the environment, this poses a significant health risk to anybody that may come into contact with the river. Leading infrastructure consulting firm AECOM was appointed to provide full professional services to investigate, design and manage the construction of the urgent remedial actions required. The scope of work was to address the capacity and pollution problem, as well as upgrade the system for a future estimated sewage flow of over 900 ℓ/s in accordance with the city’s Sewer Master Plan. The project saw about 4 300 m of bulk sewers replaced and another 1 500 m of network sewers installed, with pipe sizes up to DN 1 000 mm. This has not only improved environmental and health con- ditions for those living along the river or downstream farmers using the water for irrigation, but the provision of additional capacity in the sewer network has un- locked upstream development opportuni- ties that will stimulate economic growth. Christian Jordaan Pr Eng Associate Engineer AECOM christian.jordaan@aecom.com Unpacking the Plankenbrug main outfall sewer and associated works – phases 2 & 3 An ageing and overloaded sewer network in Stellenbosch necessitated an urgent upgrade of the town’s main bulk outfall sewer. The upgrade needed to provide additional operational capacity and reduce the associated pollution of the Plankenbrug River caused by the strained system. 32 October 2021 Civil Engineering Pipeline material design was done according to manufacturer availability Due to the challenging terrain, a total of six route options were evaluated for Phase 2