Scope of Works
The scope of works included the upgrade of 338 metres of existing 225mm Earthenware (VC) sewer main to a 355mm polyethylene (PE) PN8 main via pipe bursting methodology, as well as the rehabilitation of six manholes.
Council determined that pipe bursting was the optimal technology to use in this situation, particularly due to the ability to upgrade the pipe without the need to excavate three metres deep, remove the existing pipe and install the new pipe using conventional methods for the entire route. For this project, pipe bursting provided a less labour intensive solution, minimising disruption to the environment in a cost and time efficient manner.
The existing main was replaced one section at a time between two manholes, and pipe bursting crews excavated pits beside manholes to provide entry and exit pits along the alignment. Once the launch and exit pits were excavated, the pipe bursting machine was then lowered into the exit pit and rods were subsequently inserted through the existing pipeline through to the launch pit. The new 355m PE pipe was then attached to the rods with a bladed bursting head, which was then pulled back by pipe bursting rig. The old Earthenware pipe was cracked and displaced into the surrounding soil and new pipe was pulled into its place. Once the pipe bursting operation was completed, the manholes were rehabilitated to house the new larger pipe.
Some construction difficulties that UEA managed were:
- High flow of the raw sewer flowing through the existing main
- Deep excavations
- Confined spaces
- Sewer by-passing difficulties
- Higher than average rainfall
- Excavations located within private properties
- Close proximity of existing main to residential structures
With the use of pipe bursting techniques, UEA was able to:
- Avoid trenching to a depth of three metres
- Reduce the disruption to the community with trenchless methods
- Minimise the need for restoration of excavated areas
Planning, safe working procedures and good communication with the council ensured all risks were managed and overcome.