Ovoid Sewers – Double Bay

Project Summary Sheet

Customer: Sydney Water

Location: Double Bay NSW

Delivered: February 2014

The Challenge

Design loads on the ovoid sewer meant that standard CIPP liners had insufficient strength to meet design requirements. Also the location of the sewer and the access points made for logistical challenges.

The Solution

Interflow proposed a fibreglass liner, to be cured by UV light. Called Interline® UV, it is a much stronger form of CIPP liner.

The Project

Interline® UV liners are installed by first being winched into place from an existing maintenance hole. The liner is inflated and then cured by a UV light “train” which travels along inside it. The speed of the “train” and intensity of the UV light are computer controlled to ensure proper curing so that the required high strength liner is obtained.

The project was complicated by the locations of access points, including one in a basement car park. Liner winching of up to 450 metres in length was required inside the deteriorated host pipe. This was further than had previously been attempted for this liner anywhere in the world.

Complex flow bypass with polyethylene pipework laid in existing storm water channels and installed below roads was needed to maintain sewer services in the locality without compromising safety.


This project (which was completed as part of the Sewer Rehabilitation Term Contract) required development of new work methods to install a new type of liner under conditions more demanding than previously attempted worldwide. The location of the project provided challenges to meet Sydney Water’s strict community relations standards.

The project demonstrated Interflow’s capability to meet client needs with a unique solution, applying some 80 years of pipeline construction industry experience.

This project won a CCF Award for Construction Excellence.

Interflow is committed to offering its customers optimum solutions of the highest value for pipeline rehabilitation.