A heavily used foul drain taking waste from the hospital office facilities was found to have dropped by 50mm approximately 1 metre upstream of the very deep manhole situated behind and under the steps at a depth of approximately 2 metres.
It was totally impractical to excavate so a platform was constructed in the manhole and access to the pipe made by breaking through the wall of the chamber and pulling the broken pipe out and pushing a new UPVC pipe back in. There was no way of reaching the far end of this to install a coupling and the remainder of the drain was poor with many cracks and fracture so the drain was lined with a high performance inverted “Brawoliner” that rectified the faults and formed an internal coupling.
This operation prevented major disruption to a very busy thoroughfare and avoided the engineering problems that an excavation would have caused. We managed to keep the steps open throughout the operation allowing staff to continue working without hinderance.
The drain was only out of action for a short period which prevented any disruption to the services. We calculated that the capacity of the system behind the break was sufficent to avoid the need for overpumping which would have blocked off the steps as it would have caused a trip hazard and we were correct.