Hawthorn Main Sewer Rehabilitation

Scope of works

The scope of work involved: 

• Rehabilitation of 1.7km of ovoid brick sewer with an internal diameter of 1100mm.
• Installation of Glass Reinforced Plastic (GRP) slip lining using pipe jacking.
• Cured In Place Pipe (CIPP) relining.
• Rehabilitation of deep maintenance holes (12–18m).
• Development of complex bypass and flow management systems.
• Cleaning of silt and debris, including manual removal of blockages.
• Decommissioning of redundant assets and backfilling of ventilators.
• Testing, verification and traffic management.

Innovative solutions

The project presented a long list of challenges and constraints that demanded fresh thinking and bold engineering. To meet the project objectives, the team developed innovative solutions that delivered a series of firsts for rehabilitation works in Australia and internationally. Two of the most significant were the use of cured in place maintenance hole (CIPM) technology and a pioneering pipe jacking method. These approaches not only addressed the immediate technical challenges but also extended the asset’s life by up to 50 years. Each solution was carefully designed and executed to ensure safety, efficiency and long-term performance, setting new benchmarks in complex sewer rehabilitation.

Setting new benchmarks in CIPM technology

A key highlight was the rehabilitation of maintenance holes at depths of 12-18m using CIPM technology, setting a global record for the deepest works of its kind. The process combined precision laser scanning, custom GRP membrane fabrication, and steam curing to complete each structure within just two days, significantly reducing site occupation on Melbourne’s busy roads. This rapid execution significantly reduced disruption to Melbourne’s congested urban roads. The approach required fewer personnel and reduced traffic management, while maintaining uninterrupted essential services, delivering tangible benefits to both residents and commuters. Additionally, the project provided valuable insights to international suppliers, highlighting the future potential of this CIPM technology.

Pioneering a pipe jacking solution

To rehabilitate long sewer sections where conventional methods were unfeasible, the team adopted an innovative pipe jacking technique. GRP ovoid segments, each 700mm long, were lowered through existing maintenance hole access points and jacked into place, achieving the installation of continuous runs of up to 400m under live flows of 200L per second. Once in position, a specially formulated grout was injected between the liner and the brick host pipe, creating a fully structural conduit with a 100-year design life.

This approach set a new benchmark for pipeline rehabilitation, proving that extensive renewal could be achieved entirely from existing maintenance holes without major alterations. Refinements to the jacking rig, pipe handling and flow management further improved efficiency, reduced confined space entry and enhanced safety, while minimising disruption to the surrounding community.

Safe and sustainable delivery

The team’s commitment to safety and sustainability was central to the project’s success. By completing most works from the surface, the team significantly reduced the need for confined space entry and high-risk works were tightly controlled through detailed bypass and flow management. 

Equally important were the environmental outcomes, with rubber waste recycled into industrial flooring, surplus cement and grout donated to the community, and shade cloth repurposed into reusable shopping bags. These initiatives not only reduced waste but also created positive outcomes well beyond the project site.