A pipe renewal project beneath one of Melbourne’s busiest roads has won an award for its successful delivery under demanding conditions, which included maintaining 24 hour water service to buildings, not disrupting high volumes of traffic or tram services, minimising risk to other major underground services, and engaging with numerous high-profile stakeholders.
South East Water and Interflow have won the Victorian Civil Contractors Earth Award, Category 2 (projects $1m to $5m) for the St Kilda Road Main Renewal Project which involved the replacement of a 1.4km section of a 135-year-old water main that runs under one of Melbourne’s major roads.
The project involved replacing a section of the old water main, from Armadale Street to Henry Street, with PE100 PN16 polyethylene pipe that had an outside diameter of 355mm.
This section of the main was approaching end-of-life, and replacing it was critical to ensure ongoing reliable water supply in such a busy and highly populated area.
The Earth Award recognised the innovative methods used by Interflow and South East Water to overcome the project’s many challenges and ensure there was minimal disruption to the area.
The location of the main meant the project had the potential to impact the Alfred Hospital, Bicycle Network, Federal Police, two Melbourne Fire Brigade districts (MFB), two local councils, two schools, two foreign consulates, Yarra Trams, 28 businesses including cafes and major company headquarters, as well as 6,500 residential apartments.
One of the main requirements of the project was that water services to surrounding buildings had to remain operational, including the 24 hour operation of fire service mains. St Kilda Road is also a high traffic and tram area, so construction works were not allowed to affect traffic during the day or tram services at any time.
To ensure an uninterrupted water supply, Interflow set up 200m sections of temporary above-ground pipework parallel to the water main and water supply was diverted to the temporary pipe and transported to all buildings along the pipeline’s route.
Interflow carried out all pipe laying work at night and was able to restore the road by morning to allow traffic to resume. This fast turnaround was achieved by removing only 20m of the old main each night, laying the new polyethylene pipe and connecting it to the previous section before backfilling.
Working on 20m each night complied with the City of Melbourne’s requirements that the maximum length of an open trench had to be less than 30 metres, and where possible, the trench was deepened so there was 1.2m of cover over the pipe to fit requirements from VicRoads.
The other major challenge in the pipe’s installation involved ensuring the safety of other major underground assets including other water mains, high-pressure gas mains, and electricity and communication cables, as these all crossed over the existing water main.
To minimise risk to other services, Interflow performed careful excavation and pipe handling, and for some parts a ‘dog leg’ of steel pipework was fabricated to allow the new main to clear other existing assets.
Since work was completed in early September 2015, the industry has taken note of the project’s delivery and, in particular, the collaborative way Interflow and South East Water worked together to not only complete the project but also manage all community and stakeholder engagement.
Of particular note was a survey of residents and businesses, which found that 84 per cent of respondents were satisfied or very satisfied about the project’s ability to minimise disruption.
The new water main is now expected to exceed the 130-year service life of the old main.
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