Refresh Vaucluse and Diamond Bay

UEA was engaged by Abergeldie to deliver the HDD component of the Refresh Vaucluse and Diamond Bay HDD Project for Sydney Water. This 1.84km section of the pipeline played a crucial role in providing critical new wastewater infrastructure to improve water quality, protect public health and safeguard iconic Sydney Harbour beaches. UEA’s scope on the project involved methodology development, design review, drilling, pipe supply and pipe welding. Practical completion was reached on the 26th of August 2025.

Scope of Works

In 2018 the state government announced its commitment to address the three ocean outfalls on the Vaucluse peninsula that remain as the only outfalls on the NSW coast that continue to discharge untreated wastewater into the ocean. Part of the proposed solution involved transferring wastewater flows to the Bondi Wastewater Treatment Plant (WWTP).  

As part of the overall solution a new 1.84km on grade wastewater pressure pipeline was required to be installed from Parsley Bay to Carlisle Street, Rose Bay at a depth of up to 60 metres. Said to be one of the most complex and intricate HDD projects ever undertaken by Sydney Water across their extensive network, planning for the project, its mobilisation and execution had been in consideration for nearly 20 years.  

UEA was engaged under an Engineering and Construction NEC4 contract, working in collaboration with Abergeldie and supported by Herrenknecht to deliver the horizontal directional drilling scope. As part of the engagement, UEA was responsible for design verification and confirming that the proposed pipe and equipment would be fit for purpose. 

Mobilisation into the incredibly constrained Parsley Bay Reserve was scheduled to follow the peak summer period and allow works to commence outside of school holidays. Significant consultation with local residents and businesses took place to allow the smooth and trouble-free delivery of 24 separate truckloads of equipment to the entry site including semi-trailers, tilt trays and the track mounted crawler HK250c drill rig. 

The HDD design allowed for the installation of up to 100m of 610mm steel conductor casing to support the borehole at its shallower depths as well as offering an effective means of containing the almost guaranteed groundwater flows as the bore traversed through several known Dykes and a number of other inclusions. Once installed, the casing was grouted and tested to ensure a watertight seal was present.  

Pilot boring on the design grade of +0.87% commenced utilising a mud motor and Australian made Hardmetals PDC bit along with the full suite of Vector Magnetics ParaTrack Gyro module and At-Bit Inclination Assembly. To ensure adherence to the tightest grade tolerances, survey shots were taken every two metres with steady progress still made. The pilot bore was successfully completed in under 30 working days, becoming UEA’s longest on grade bore to date.  

Following successful completion of the pilot hole, the borehole was reamed to size in a single 20”/508mm reaming pass. Based on information from the pilot bore, the decision was made to forward ream with PDC tooling as a means of ensuring full flow to the entry side. Once the two Dyke formations were successfully negotiated the forward reamer was tripped out for inspection and the decision was made to back ream the remaining 600 metres with InRock tooling.  

Pipe installation of the 355mm PN25 was successfully completed in an arduous weld and pull operation, one 24m length at a time over a 16 day period. 

Following the completion of the bore and successful hydrostatic pressure test, together with Herrenknecht and Abergeldie, the project was named a finalist in the New Installation Project of the Year category at the Australasian Society for Trenchless Technology Awards Gala, held as part of the No Dig Down Under Conference in Melbourne. 

Key Project Highlights

• Pipe installed in compliance with Sydney Water’s Civil Specification. 

• Project delivered ahead of program. 

• Innovative methodology developed in preparation for the unknown volumes of ground water. 

• Utilisation of multiple steering technologies including ParaTrack Gyro Module, ParaTack 2 and At Bit Inclination Assembly. 

• Finalist in the New Installation Project of the Year category at the Australasian Society for Trenchless Technology Awards Gala.