Three new wastewater pipelines, three challenging microtunnel drives and one particularly demanding 170m installation.
Kerry Drainage & Civil used specialist trenchless techniques to install more than 390m of new wastewater pipe, including a long-distance drive beneath a wetland.
Kerry Drainage & Civil was engaged by Pipeline & Civil as a specialist subcontractor for Package 3 of the Southern Redhills Gravity Pipelines project for Watercare. KDCivil’s scope involved installing three sections of new wastewater pipeline, all using microtunnelling to achieve the required grades of approximately 0.5%.
The three pipeline sections comprised 112m of 355mm OD HDPE, a further 112m of 355mm OD HDPE, and 170m of 560mm OD HDPE.
The 170m installation presented the greatest technical challenge. The length of the drive meant a conventional single pilot shot was not practical, so Kerry Drainage & Civil developed a solution using two pilot shots and an intermediate shaft. A second drill was established in the intermediate shaft, allowing the two pilot strings to be completed and then joined together. Once connected, the full pipe string was pulled into position in a single operation.
The receiving pit for the 170m section was approximately 5m deep and located close to a wetland, creating additional constraints around access and construction. Rather than disturbing the wetland to position the pipe string, KDCivil used HDD to drill a lead-in bore beneath the wetland, allowing the pipe to be brought into position from the receiving pit.
The remaining two pipeline sections were also installed by microtunnelling, providing the precise grade control required for the gravity wastewater network.
By combining microtunnelling, intermediate shaft construction and HDD techniques, Kerry Drainage & Civil successfully delivered the three pipeline installations while working within challenging site and environmental constraints.
