Sewer Drainage. Excavation. Drain Inspection Cameras.
Issue
The sewer at 37 Woodmancote Road is reported blocked after the realignment of a lamppost on the berm in front of the property. The drain was inspected by camera and it was determined that the sewer was blocked in the vicinity of the lamppost and would need to be excavated. The appropriate permissions were sought, and work commenced on Monday February 1.
Excavation
Due to the presence of underground utilities, it was decided to hydro-vac the excavation using a sucker truck. The excavation revealed that the existing terracotta pipe had been crushed by the breastplates (Heavy concrete anchor blocks) that had been installed to correct the alignment of the power pole. These had been placed without the use of imported base-course (A kind of rock and soil mix that can be tightly compacted to support underground works). After placement, it appears that the existing packing was simply replaced without compaction, and it is probable that the unsupported weight of the 3 breastplates over time crushed the sewer drain.
Issues Encountered
During the excavation to access the broken section of Terracotta pipe, even before removal of the breastplates, the lamppost moved – most likely to the pre-straightening position – as a result of no compaction on the road side of the pole. Clearly a potential hazard and it needed to be strapped to the sucker truck to secure it from further movement. A truck mounted crane was brought onto the worksite to secure the pole in its correct orientation before further work.
Remedy
With the lamppost safe, we were able to safely access the broken pipe and replace the broken section with road rated PVC100 SN16 pipe which is extremely crush resistant. This completed, basecourse was emplaced around the pipe and compacted using a heavy compactor. The breastplates were returned, supervised by a Wellington Energy contractor certified to do this work, and more basecourse – again, compacted. Finally, a layer of soil for berm reinstatement. All excess material and the broken pipe was loaded onto our truck for landfill disposal.
