The BOOS (Bondi Ocean Outfall Sewer) was the first ocean outfall sewer of its type to be designed and built in Australia. The BOOS was built as an alternative means for disposing of the city’s sewage which was being drained into Sydney Harbour.

The structure of the brick oviform varies depending on the method of original construction. The tunnel section is an oviform sewer 2.49 m high and 2.18 m wide, constructed of bricks with a concrete base; while the trench section is an oviform sewer 2.58 m high and 2.28 m wide, internally constructed completely of brick.

The BOOS is considered a masterpiece of its time; however, after 120 years of continuous service, Sydney Water decided to rehabilitate the asset as part of its $560 million Sewer Fix Program. Given that there is no alternative to the BOOS for the collection and transportation of sewage from the inner western suburbs, Sydney city and eastern suburbs to the Bondi Sewage Treatment Plant, ensuring the service life of this asset for another 50 years was of critical importance.

Water Infrastructure Group started work on site in January 2010 and rehabilitated a 911 m section of the BOOS which runs from Bellevue Hill through to North Bondi. For the works, Water Infrastructure Group used a combination of two technologies — their own propriety PVC lining system, Panel Lok, which was installed for two-thirds of the total length; and Calcium Aluminate Cement (CAC) coating, which was used for the remaining third. Significantly, this was the first time CAC coating was used by Sydney Water on a large scale.

Water Infrastructure Group project manager, John Gillan, explained the use of the two relining technologies.

“We used a combination of two technologies — our own propriety Panel Lok uPVC lining system, and CAC coating.

“Water Infrastructure Group has a lot of experience in applying CAC products, and as part of this project we conducted a large scale trial of two commercially available CAC products. We worked in close cooperation with Sydney Water, their consultant KBR, the CAC product suppliers BASF and Kerneos, and a NATA accredited testing agency.

“A significant outcome of the trial was that the technique we developed was able to achieve consistent bond strength between CAC and brickwork. Previously, there was no data available on bond strengths but we now have a good understanding of the issues and a reliable technique to achieve the performance results we want,” Mr Gillan said.

Brian Mahon, Water Infrastructure Group Manager Construction, said that Water Infrastructure Group had developed its Panel Lok lining system into a highly refined, efficient and cost effective process.

“Our Panel Lok system is ideal for relining a wide range of pipes and we have focused on developing it for oviform pipes like the BOOS. This was quite a challenging project and it is pleasing that our systems performed so well.

“The BOOS project was also highly successful from a safety and community point of view, where we achieved fantastic outcomes in the third party audits. This is particularly significant given that the work was carried out at night, in live flows and at depths underground of up to 28 metres. All this work was carried out in busy residential areas at North Bondi and Bellevue Hill.”

The team from Water Infrastructure Group are justifiably proud of their efforts on this job, a sentiment clearly shared by the ASTT Awards judging panel. The BOOS relining project was officially named as the ASTT’s Rehabilitation Project of the Year at the ASTT’s Gala Dinner, held as part of No-Dig Down Under 2011 in October.

“It’s great to see this project win the Rehabilitation Project of the Year award. We had a great team and it is very rewarding to see their efforts recognised,” said Mr Mahon.