Civil Engineering April 2022 | Vol 30 No 3

Civil Engineering April 2022 29 D oHS Farm694 – 2432m Bulk Sewer in Spine Road and Residential Area is a R300 mil- lion Department of Human Settlements project. Once completed, ownership of the line will be transferred to the City of Cape Town. The pipeline is being built in two sections. The first, which was completed in March, comprises a 1.05 km line using 1 200 mm diameter × 2 m long pipes. Starting from a manhole in Merrydale, it follows a servitude parallel to an existing bulk sewer line under residential proper- ties and a school in Merrydale, as well as under the neighbouring suburb of Rocklands to a point in Spine Road. The second section, which uses 1 350 mm diameter × 2.5 m long pipes, runs for 1.3 km along Spine Road and feeds into the Mitchells Plain Wastewater Treatment Works. The tender was put out as a conven- tional open cut installation, but several conditions rendered this option more expensive, disruptive, considerably more time consuming and very high risk. These included: a sandy and water-logged terrain; pipeline depths of up to 9 m; a first-section routing through built-up areas; and a routing along the centre of Spine Road. “Open trenching wasn’t a viable op- tion,” explains Hannes Coetzee of CSV Construction. “Various routes were con- sidered but in the end we opted to install Trenchless Technology Microtunnelling minimises disruption and ups safety in bulk sewer installation CSV Construction is installing a 2.35 km bulk sewer pipeline with state-of-the-art microtunnelling technology in Mitchells Plain, Cape Town. Acid-resistant HDPE-lined concrete pipes, manufactured by CMA member, Concrete Units, are being used to construct the line, due for completion in June 2022.