Western Harbour Tunnel Southern Tunnel Works – Environmental Outcomes
Describe WHAT you have done and HOW you have done it.
In 2018, the John Holland CPB Contractors Joint Venture (JHCPB) was contracted by Transport for New South Wales (TfNSW) to deliver the Rozelle Interchange (RI). The Project scope included construction of an underground tunnel motorway interchange, including enabling works for the future Western Harbour Tunnel (WHT).
In late 2021, TfNSW issued JHCPB a contract variation to construct WHT Stage 1. The new scope included tunnel excavation between Emily St, Rozelle and Cove Street, Birchgrove, connecting into the WHT Cut and Cover (C&C) previously constructed by JHCPB as enabling works for WHT.
JHCPB identified three design innovations to reduce the environmental and community impacts associated with WHT Stage 1:
- Eliminating the temporary construction site at the corner of Victoria Road/Darling Street by establishing a spoil load-out zone within the pre-existing WHT C&C.
- Optimising the driven tunnel alignment.
- Optimising the ventilation tunnel alignment.
The following benefits were realised:
• A substantial reduction of 170,255t of carbon (7.43%), and between 7-12% of various raw material use and waste generation during construction.
• Elimination of a substantial number of community impacts, including noise, dust, traffic congestion and loss of visual amenity at Iron Cove and Rozelle.
• Reduced construction program duration and de-risking of the overall works program.
• Reduced capital expenditure for the NSW State Government.
Further detail on the innovations developed by JHCPB:
- Elimination of the need for a temporary construction site
The WHT EIS identified a requirement for a temporary tunnel decline on the corner of Victoria Road/Darling Street (the site of the former Balmain Leagues Club) to provide access for spoil haulage during WHT excavation.
The 8,500m2 site is bounded by residential properties, Rozelle Public School and small retail businesses. With up to 420 heavy vehicle movements anticipated to enter the site daily, this proposal was likely to be highly impactful for the community.
As the contractor responsible for delivering both RI and WHT Stage 1, JHCPB proposed to establish the spoil load-out zone within the WHT C&C structure situated inside the existing RI boundary. This solution entirely omitted the need for the temporary tunnel decline under Rozelle Public School that had been already approved by the Minister for Planning.
- Driven tunnel alignment optimisation
JHCPB optimised the mainline tunnel horizontal alignment, reducing the driven tunnel length by 2.77%. This small refinement has compounding benefits; with 67,000 vehicles forecast to use the tunnel daily by 2027, the shorter distance means estimated vehicle emissions will be reduced by >800kg CO2e daily.
- Ventilation tunnel alignment optimisation
During detailed design the ventilation support tunnel alignment was optimised and overall length reduced. A 10% reduction in excavation volumes was achieved for these tunnels.
What were the OUTCOMES and how were those outcomes shared?
- Elimination of the need for a temporary construction site
By eliminating the need for a tunnel decline at the former Balmain Leagues Club site (https://www.transport.nsw.gov.au/news-and-events/media-releases/update-on-victoria-road-construction-site), the following benefits were realised:
• Forgoing establishment of a new site means the WHT delivery timeline was shortened and the Project de-risked as a whole. This has broader benefits; the earlier the Project is completed, the sooner WHT can deliver efficiencies for the economy by shortening cross-city journey times and reducing traffic congestion.
• No temporary construction site established in Rozelle’s busy residential/retail/commercial precinct. The alternative solution saw the new spoil load-out zone be established within the WHT C&C structure, which sits within an existing construction site and industrial area.
• No deterioration of visual amenity on Darling Street and Victoria Road.
• Elimination of shallow tunnelling under Rozelle Primary School avoids disruptive noise/vibration impacts on students.
• Heavy vehicles taken off Victoria Road minimises traffic congestion and enhances safety for children accessing nearby primary school.
• The site offices for Stage 1 WHT were also relocated to the WHT C&C structure alongside the spoil loadout zone. This was a superior outcome to the EIS-approved location (inside the future Rozelle Parklands). Thanks to this innovation, the Rozelle Parklands will be kept free of construction office buildings, leading to more open green space for the community, sooner (refer attachments).
• Large volumes of materials and waste were saved:
o No need to demolish existing structure at former Balmain Leagues Club.
o No need to establish new utilities connections, hardstand, an acoustic shed or signalised intersection.
o An estimated 28,343t steel and 48,031m3 spoil waste were not required (refer attached table).
• Reduction in noise pollution. All spoil load-out activities are instead undertaken within the WHT cut & cover, an acoustically insulated structure with no immediate neighbouring residential receivers.
• Emissions reductions. Direct heavy vehicle access to motorways/arterial roads (City West Link) from the WHT C&C has reduced journey lengths and associated emissions.
• Less potential for dust generating activities through forgoing the need to establish a new site.
• Reduced capital expenditure by the State Government as delivery costs are reduced.
- Driven tunnel alignment optimisation
By shortening the mainline tunnel length:
• Vehicle emissions will be reduced by an estimated >292,000kg CO2e during the first year of operations alone.
• >14,000m3 of spoil was saved through reduced excavation requirements, reducing waste generation and avoiding heavy vehicle emissions associated with spoil haulage.
• Less water, steel and concrete required to reinforce and fit-out the tunnel (refer attached table).
- Ventilation tunnel alignment redesign
The 10% reduction in excavation volume means:
• Reduced steel, concrete, shotcrete and water consumption.
• Reduced spoil excavation volumes.
• Ventilation fan power loads are reduced, as vitiated and clean air has a shorter distance to travel to circulate through the tunnel network.
These positive outcomes have been shared with the following stakeholders:
• The WHT C&C innovation was shared to the client prior to awarding the WHT Stage 1 variation. The innovative, agile contract negotiations that took place between TfNSW and JHCPB to enable such innovations to be realised demonstrated a capacity within TfNSW to fully maximise opportunities in infrastructure delivery, regardless of project stage. The development and approval of this solution required close cooperation and collaboration between the two parties.
Mainline and ventilation tunnel alignment enhancements were shared with the client during meetings and presentations in detailed design.
• The local community is one of the most important stakeholders in the delivery of the WHT Project. The benefits of the solution have been shared with the community via email and paper-based construction updates, as well as on Frequently Asked Questions pages and during face-to-face community town hall meetings.
Project staff and parent companies
• The WHT innovations developed have been converted into a 2-page summary document stored on the Project’s external-facing website
• This 2-pager has been shared with interested third parties, including members of the parent companies (JH and CPB Contractors), to provide an overview of the innovation and generate interest in further knowledge share across the businesses.
• The innovation has also featured in Project intranet articles and newsletters, spreading word of the innovation to the 1500 direct employees and subcontractors who attend the Project site daily.
Describe WHO benefited from your initiative, innovation, or approach?
• Reduced capital expenditure, as the delivery contractor was able to pass on financial savings from the more efficient solutions.
• No need to acquire the site of the former Balmain Leagues Club as a temporary construction site.
• Simplification of project delivery methodology allowed resources to be better focused on other areas of project delivery.
• De-risking the overall WHT program of works by reducing the forecasted delivery timeline.
• Reduction in carbon footprint aligns with TfNSW carbon reduction goals and enhances the reputation of the NSW government.
• Reduction of trucks on local and arterial roads reduces traffic congestion and enhances pedestrian safety, particularly for school children accessing the local primary school.
• Less potential for dust generation.
• Significant reduction in noise and visual amenity impacts to local business and sensitive receivers by forgoing use of the temporary construction site at the site of the former Balmain Leagues Club.
• Local businesses not impacted by disruptive temporary construction site in the centre of the commercial/retail district.
• The site of the former Balmain Leagues Club can be beneficially redeveloped for other pursuits earlier, as it is no longer required to support WHT construction.
• Earlier access to the full extent of the future Rozelle Parklands for the community, with the WHT Stage 1 site offices able to be relocated to the WHT C&C structure rather than the future Rozelle Parklands.
NSW state and global community
• Reduced materials (steel, concrete, water) usage reduces pressure on finite resources.
• Reduced waste generation reduces pressure on landfills and fuel emissions associated with heavy vehicle haulage.
• Reduction in project carbon footprint benefits the global community by limiting contribution to climate change.
• Contributing to on-time delivery of a major infrastructure project will benefit the state economy through increased efficiency of transportation and road travel.
• Project delivery is de-risked by avoiding the need to establish an entirely new site.
• The superior outcome delivered for the client and community enhances the reputation of JHCPB and the parent companies as trusted tier one contractors.
• Excavation of WHT Stage 1 was able to commence 3 weeks earlier than originally forecast.
• By shortening the length of the mainline tunnel alignment, commuters will consume less fuel and reach their destination sooner once in operation.
What LEGACY and UN SDG CONTRIBUTION was achieved?
The three successful innovations highlighted above have left a strong environmental legacy for WHT Stage 1. In implementing these changes, JHCPB and TfNSW have set a high benchmark for responsive and responsible urban construction that considers the needs of stakeholders and the environment in all aspects of project delivery.
The reduced carbon footprint achieved has contributed to the State’s net zero goals, and the decision to relocate spoil load-out activities has enhanced the local community’s experience with the Project. For most residents, the construction of WHT Stage 1 will go almost entirely unnoticed, with all works being conducted ‘out of sight and out of mind’; occurring entirely underground from within the WHT C&C structure.
The innovations presented align with the SDGs on a number of fronts:
Responsible consumption and production – By reducing spoil excavation volumes, better urban waste outcomes have been achieved, closely aligning with SDG Target 12.5, to ‘substantially reduce waste generation through prevention, reduction, recycling and reuse’. Reduced consumption of finite materials including steel, concrete and water to construct the Stage 1 WHT project also align with this SDG.
Sustainable cities and communities – By forgoing the use of a temporary construction site at the former Balmain Leagues Club, JHCPB has supported the maintenance of a safer road network, keeping construction vehicles separate from popular pedestrian areas and traffic to the greatest extent possible. This aligns with SDG Target 11.2, which highlights the importance of ‘improving road safety'.
Impacts to urban air quality have been mitigated by moving spoil load-out to the WHT C&C, where the potential for dust generation is reduced. Noise and vibration impacts have been lessened, with no shallow tunnelling to be undertaken underneath sensitive receivers such as Rozelle Primary School. The urban amenity of Iron Cove and Rozelle’s retail and commercial precinct has been maintained thanks to these innovations.
Industry, innovation and infrastructure – The Innovative, agile contract negotiations that took place between TfNSW and JHCPB to enable such innovations to be realised, demonstrated a capacity within TfNSW to fully maximise opportunities in infrastructure delivery, regardless of project stage. This fosters innovation by encouraging industry to bring new ideas to government in the knowledge there is the capacity to act quickly to benefit the State and community.