Refresh Woolloomooloo

Sydney Water

Sydney, New South Wales, Australia

Heritage protected infrastructure, confined spaces and thousands of stakeholders in one of Australia’s oldest and most culturally sensitive precincts. Diona undertook the technically complex and community stakeholder challenge of retrofitting 4.8 kilometres of waste water pipes in Woolloomooloo and Darlinghurst for Sydney Water.

The project was to separate the existing combined stormwater/wastewater system in the Woolloomooloo area in order to minimise pollution of the bay, preserve the ecological communities in the area, and maintain the health of surrounding residential properties and businesses on the Finger Wharf and foreshore.

The Woolloomooloo area consists of a stormwater/wastewater diversion system with seven interceptors, four of which divert flow to Woolloomooloo Bay. During wet weather events, the diversion system capacity would be exceeded, resulting in wastewater discharge to Woolloomooloo Bay.

Managing 30,000 community stakeholders and a newborn baby

Diona and Sydney Water worked closely with the local community to keep all stakeholders informed and disruption as minimal as possible within a highly dense residential and commercial region of Sydney. The project team’s response to technically challenging tasks and keen use of problem-solving skills resulted in project works being completed on time.

Communications and community relations with more than 30,000 stakeholders including local residents, businesses and schools were managed and delivered by both Sydney Water and Diona during the works.

Provisions put in place included specialist equipment and multiple acoustic barriers to reduce and contain the noise. For a local school, the project team staggered breaks so that they coincided with exams, and carried out maintenance and other inaudible works.

Diona responded to the needs of a Darlinghurst mother and her newborn baby. To give the baby a chance to nap, Diona stopped the heavy machinery, jack hammering and drilling and focused on low noise activities. Once the baby was awake, the mother would call the foreman and project works would continue. The team maintained this pattern on a daily basis for months.

A complex project requiring effective management of multiple challenges

Many challenges had to be overcome during the project given the layout of the existing combined storm/waste water system, the close proximity of works to heritage buildings and structures, and the depth of the pipeline trenches adjacent large buildings and other structures.

At the heart of the project was a convict-built brick pipe called an oviform. This six-foot-high, four-foot-wide oval brick pipe had served the inner-city precinct as a combined storm and waste water drain since the 1820s. Two centuries later, it continued to perform its task admirably. However, the advent of the modern sewerage system, and a greatly increased population, posed a complication. Many areas in Sydney had been separated, but given the complexities of the works required for this area, Sydney Water were determined to get it right.

The project team uncovered a lot of heritage items during the project. Archaeologists and the Heritage Council were consulted to ensure heritage items were protected and preserved before removal. Some of those items, included convict-made bricks and glass bottles, as well as dinner plates, bottles and even old privies (outdoor toilets).

The Diona project team also carefully managed the protection of built heritage, which in most cases was people’s homes and businesses. Old buildings are very prone to damage and cracks, so measures such as vibration monitors and alteration to construction methods were required to ensure there was no damage.

Interesting project stats

  • 5 kilometres of new wastewater & stormwater pipes laid
  • Over 226,796 personnel hours worked on the project
  • 500 properties inspected to see how they are connected
  • 95 new maintenance holes built
  • 30,000 stakeholders (dwellings, churches, schools, restaurants etc.) engaged with during the works
  • Over 150 updates/notifications issued to stakeholders
  • 50,000 tonnes of dirt excavated which equals 3,846 trucks worth
  • 11 metres: deepest depth of open excavation
  • Over 90 personnel working on the project at peak times
  • Over 500 metres of pipelines constructed by means of trenchless micro tunnelling


  • 2021 Wastewater Project of the Year at Global Water Awards
  • Runner-up Project Excellence in Sydney Water 2019 Delivery Management Excellence Awards


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