Progress continues on collapsed bulk sewer works in Retreat
11 April 2023
The City is maximising its working hours daily to
complete the repairs to the 990mm diameter bulk sewer main that collapsed in Prince
George Drive, Retreat, on Sunday, 19 March 2023. This is being done
despite the adverse conditions during this major repair project. However,
the safety of staff remains a concern due to the volatility of the area.
Excavation at the collapsed concrete sewer location is currently well under way and a portion of the collapsed sewer has been exposed and has since been removed. This work, a deep-trenching repair exercise, involves excavating more than five metres deep to enable the workmen to get beneath the old pipe as part of the overall assessment that needs to be done before the new pipe section(s) can be inserted.
Mechanical excavation is limited to the extent of the reach of the digger loader used due to the confined space in which the work is being done. Thereafter, manual excavation needs to be done. Double-shoring also had to be done to assist with the accessibility of the pipe section that needed to be repaired thereby speeding up the process.
The contractor has thus far successfully implemented measures to prevent the sewage from entering the excavation site and also ensuring the continuous conveyance of the sewage volumes with onsite mobile pumps. Additional pumps are on standby to assist with managing the flow variance.
The maintenance crew reports that a further extension of the excavation is required due to the poor condition of the pipe. The top internal section of the pipe was weakened by the gases formed during the conveyance of the sewage over time and this resulted in the structural collapse of the sewer. Additional assessments are being done as the work progresses to determine the integrity of the pipeline.
'This is quite a complex repair exercise, which has to take a number of very important factors into account to ensure the successful execution of the repairs of this large diameter sewer. Stabilising and protecting the site to enable the safety of the repair crew is of paramount importance during the entire project.
'One just has to look at the proximity of the vehicular movement, which has since been permitted to ease the traffic flow in the area, to the deep-trenching work and the high water table that the workmen have to contend with to successfully effect the repairs to the desired standard of acceptability, to realise that this requires skilful workmanship that cannot be rushed. This is no mean feat.
'The applied technology to prevent the sewage from entering and contaminating the repair site will considerably assist in reducing moist conditions encountered during excavation and will speed up excavation. Overall, I am pleased with the work done thus far. I would like to apologise for the inconvenience as well as express our gratitude on behalf of the City for the patience displayed by both motorists and residents,' said Councillor Zahid Badroodien, the City's Mayoral Committee Member for Water and Sanitation.
Regrettably, with the recent vandalisation of the pumps over the Easter weekend, the theft of shoring material as well as the increased scope of work based on findings when the pipe was fully exposed, means that the new envisaged date for completion on or near 30 April has been jeopardised. In the meantime, workers will continue to work towards this deadline provided no further challenges are experienced on site.
End
Published by:
City of Cape Town, Media Office
