This project presented the most formidable challenges we have encountered to date. Our urgent scope involved the cleaning and CCTV inspection of a critical wastewater network, consisting of 1.6km across two parallel pipes that served a significant portion of a town’s population.
The target section of both lines extended 1.1km upstream of the Wastewater Treatment Plant and concluded 300m upstream of the plant. The pipes had diameters of 375mm and 675mm, with average continuous off-peak flows of approximately 45% and peak flows of 65%.
While we were prepared to handle the substantial flows, we were taken by surprise when we encountered a substantial amount of non-wastewater debris. This unexpected challenge emerged when the initial pass of our jetter in a 60m section caused a large gravel blockage around the downstream manhole. We swiftly mobilised our team to clear the blockage and restore normal flows without causing issues upstream.
Further investigation revealed that while the manholes were relatively clear, the pipes were up to 40% blocked with solid debris. This rendered conventional jetting ineffective, as the volume of debris would quickly block the lines.
Undeterred, we devised an innovative solution. By utilizing a smaller diameter overflow pipe between the parallel lines, we could partially reduce the flow in one line at a time, enabling short complete blockages upstream while we jetted 5m sections and removed debris with a suction truck. The client approved the approach, and we proceeded with determination.
Given the slow and meticulous nature of the process, we enlisted the support of a local sub-contractor to double our jetting and suction capacity. As we progressed, our CCTV cameras guided the jetting units to address the remaining areas that were inaccessible for visual inspection.
With all our resources and the valuable assistance of the sub-contractor, we devoted eight consecutive working days to the project. In total, we removed an astounding 24 tonnes of solid debris, which included gravel, rugby ball-sized rocks, chip seal fragments, bricks, garden tools, timber, a corroded car battery, and broken glass.
The challenges did not end there. We also contended with water supply issues, long distances between manholes (up to 140m in some sections), and limited manhole access, as two-thirds of the lines ran under private property and a school.
Despite these daunting obstacles, our dedication and unwavering commitment to excellence prevailed. The project was successfully completed, and the client was immensely pleased and impressed with our effort and the superior quality of the deliverables we provided. This achievement is a testament to our team’s expertise, problem-solving skills, and determination to deliver exceptional results even in the face of the most challenging projects.
