According to Themba Mavimbela, the project manager for the reconstruction of the Coleraine Drive bridge, the initial plan on Coleraine Drive was to reconstruct the damaged culvert.
“This was estimated to be complete in four months,” he said.
During the process of reconstruction, Mavimbela said geotechnical (behaviour of earth materials) findings emerged. He explained that it was discovered that the culvert was founded on soft soil among others.
The estimated construction period was then extended from four months to nine months.
“The roads agency decided on an alternative design to expedite construction,” added Mavimbela.
“The conventional piling was too expensive, difficult and time consuming,” he explained. “The bridge was founded on caissons [a watertight retaining structure] instead of piling.”
Other challenges that emerged were the Telkom fibre optic cables which were obstructing excavation. Mavimbela said Telkom then took more than eight weeks to relocate the cables, slowing down progress.
“Also there was a 315mm sewer line which ran directly across the site,” he said. Apparently Joburg Water was unable to relocate the service due to budget constraints.
However, the roads agency then hired a specialist contractor to relocate the line at their own cost. “Relocation of the sewer line then took two months to complete,” said Mavimbela.
Further challenges was the damaged 400mm water line which was positioned under the existing culvert. Mavimbela said the roads agency hired a specialist contractor to relocate the line, again at their cost.
Even though the water line had been fixed, the roads agency said it still remained a challenge to consider the commencement of the bridge reconstruction.
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