The Epsom Main Sewer is part of Melbourne Water’s sewer network, transporting over 320,000 million litres of sewage a year. During routine CCTV monitoring, it was found that around 1.6km of the sewer required relining to ensure it will operate optimally for the next 50 years.

Access to the alignment was limited, with critical access points running under tram lines or were off-centre and didn’t provide the direct access needed to pull through a liner.

To reline the ovoid sewer and overcome access challenges, the team used an ultraviolet Cured in Place Pipe (CIPP). While CIPP is not a new technology, the way in which it was applied here was unique. The team had to pull through multiple maintenance holes at once, up to four hole lengths – a massive 600m.

The team also identified the opportunity to divert sewer flows to a larger sewer system upstream, which removed the need for the large pipeline to be installed in a busy public area impacting community and business access (including Flemington Racecourse and Royal Melbourne Showgrounds). This is not common practice and had not been undertaken on a Melbourne Water system before.

This was all supported through the design and implementation of a bespoke mechanical plug system, which controlled flows and kept confined space workers safe.

Around 1500m of sewer pipeline was rehabilitated with most of the works taking place inside a tight ovoid tunnel only 1200mm high. At a depth of up to 28m and with little straight-down access, liners needed to be winched over great lengths – up to 600m – to get them in place.

The challenge

The main project challenge was how to perform the works in a high traffic area with operating trams with minimal impact on the community – all while keeping workers safe below.

The use of CIPP was crucial for the project’s success as it avoided the need for deep shafts to be installed along tram and roadways. The catch is, dry conditions are needed to install and cure CIPP. In addition, a safe environment was essential for our confined space entry personnel people, traversing through deep sections for up to 300m at depths of up to 28m.

The project team needed an innovative way to control flows and facilitate the use of CIPP.

The solution

Needing a solution, a custom mechanical plug was designed which enabled flow diversion and safely sealed out flows and sewer gases. The team worked together for more than a year to identify risks, model flows, and conduct trials.

The plug ensured the safety of workers who were traversing confined spaces. It also played a key role in enabling a low-impact alternative bypass design that avoided the need to run pumps and pipes down the main road.

It also significantly reduced the risk of environmental impact by considering the risk of storm events or pump failures where flows would need to be released. The valve could be opened within an hour, eliminating the risk of sewer spill.

Conclusion

Working collaboratively with Melbourne Water and John Holland-KBR JV, the Epsom Road Main Sewer was successfully relined ensuring a 50 years design life.

By installing a bespoke mechanical plug and bypass network, diverting flows and enabling relining with CIPP, the project provided the safest conditions for our delivery team, reduced the project duration and minimised the impact on the community.