In a significant development for Sydney’s water infrastructure, the Ironbark Joint Venture of Bouygues Construction Australia and Rob Carr was awarded two key packages of work for Sydney Water last December.

The packages to be delivered by Ironbark JV are the Thornleigh Inlet/Outlet Main – water main duplication (TIOM) and the Metro North West – wastewater connection project (MNW). Both projects address the growing demand on the city’s water infrastructure as the Greater Sydney population reaches a predicted 8 million people in the next 40 years. This significant urban growth requires upgrades to water, wastewater, storm water and recycled water infrastructure to support the increased pressure on these systems.

In addition to the improvements to Sydney’s water infrastructure, the Ironbark JV has committed to implementing a range of sustainability initiatives and strategies on the project that will help deliver positive environmental, social and economic outcomes for the broader community.

Description of the packages

– The TIOM Project will duplicate the existing 1.4km drinking water pipeline between Thornleigh Reservoir and Thornleigh-Wahroonga Water Pumping Station. The additional water main will support population growth in this region by expanding the capacity of Thornleigh Reservoir, improving system reliability, and maintaining the supply of water to residents.

– The MNW Project is part of a suite of projects that will upgrade infrastructure and enhance the resilience of wastewater treatment in the region. The project will involve the construction of a new underground pipeline connecting the pumping station in Rouse Hill to the Rouse Hill Water Resource Recovery Facility. There will also be upgrades at the pumping station to increase capacity and provision for emergency power supply.

A fully integrated partnership

The Ironbark Joint Venture represents a fully integrated 50-50 partnership between Rob Carr and Bouygues Construction Australia, bringing together complementary expertise to tackle these challenging infrastructure projects. Considering the size and the complexity of the project, Bessac will intervene through an internal JV with sister company Rob Carr in support to deliver the microtunnelling works.

Construction is scheduled over a 26-month period from December 2024 to January 2027, with specialised teams already mobilising to meet the ambitious timeline.

Advanced microtunnelling solutions for Urban Infrastructure

The technical complexity of these projects requires specialised microtunnelling expertise, one that both Rob Carr and Bessac are well placed to deliver:

1. For TIOM, the works involve the installation of a DN 2100 RCJP enveloper pipe via microtunnelling, which will be performed as a single drive of 1,170m. Once complete, a DN 1800 steel carrier pipe will be fitted inside and grouted in place. A value-engineering solution with a single DN 1800 / OD 2400 RCCP pipe is under evaluation by the Client. A first in Australia!

2. For MNW, a DN 1500 RCJP enveloper pipe will be installed over two drives, the first 712m and the second 82m. At completion of both drives, a DN 1000 mild steel cement lined carrier pipe will be installed inside the enveloper and grouted in place.

To execute these technically demanding operations, three state-of-the-art Micro Tunnel Boring Machines (MTBMs) will be supplied by Rob Carr and Bessac, demonstrating the significant resource capability and capacity held within the group to cater for such projects.

Leveraging global expertise through Group Synergies

The project showcases the synergy within Soletanche Bachy and Soletanche Freyssinet, with both Rob Carr and Bessac providing specialised microtunnelling operations for major project works, and Sixense delivering advanced instrumentation and monitoring services.

For Rob Carr, this is also extension of a long-standing relationship with Sydney Water, and it demonstrates its growing capabilities in the Australia infrastructure market. For Bessac, this is its first contract in Australia, bringing its world-class expertise to the Sydney market.

Meeting Urban Infrastructure Challenges

The project team faces several significant challenges, including working in densely populated urban areas, maintaining a tight schedule to meet critical delivery timelines, minimal tolerance deviations for the installation of the steel carrier mains and significant drive lengths.