City Rail Link (CRL) is New Zealand's largest transport infrastructure project. A game-changer for Auckland's public transport system - it involves the construction and commissioning of a new double-track railway with surface and underground rail, including:
- A 3.45 km twin-tunnel underground rail link up to 42 m below the city centre
- Two major new underground stations (Aotea and Karangahape) and the redeveloped Mt Eden station for up to 9-car trains
- Grade-separated junctions, mined caverns and cut and cover tunnels across all routes
In late 2018, the Link Alliance, a consortium of seven companies of which AECOM is part, commenced work on the tender design for the major contract package involving the Stations and Tunnel component of the project (package C3). Upon successfully completing the tender design, Link Alliance was awarded the C3 package in July 2019. Subsequently, the design scope was expanded to include all major surface civil, rail and rail systems works (packages C7 and C5).
AECOM’s services within the alliance include all civil and structural design, station structures, façades and building engineering services, tunnel design, geotechnical analysis and reporting, utilities and interfacing with independent architectural and urban design teams, specialist fire and life safety and cultural heritage advisors. In addition, AECOM’s services include consenting (permits and approvals) to meet the Resource Management Act, traffic and constructible phase services, and sustainability.
Taking place within a brownfield city centre, many existing and future constraints influence the design of the project. Roads, buildings, underground structures, and services are some of the existing constraints and the C2 package, which interfaces directly with the C3 package. Future-proofing considerations include the future tunnel connections with the new station and futureproofing of the stations for the oversite developments.
Pushing new digital engineering boundaries
As design partners on the project, AECOM is pushing the boundaries of what is possible using BIM on linear infrastructure. The team has improved efficiency and reduced risk on the project and at the same time enabled greater visibility of the overall project design.
The digital engineering team uses a common data environment to ensure that all 200+ project designers and engineers work in a single online location with the latest updates. Across eight different teams, the geographically dispersed engineers can collaborate and live-share over 50 different models and simultaneously interrogate and review the current design via a web browser without additional software or hardware requirements.
As part of the tunnel design process, AECOM has introduced new design processes that combine traditional BIM processes with parametric design and generative design processes, reducing modelling time from weeks to hours.
Figure 1 – CRL model of station platform and connections
Driving innovative design
Construction of CRL is occurring in a highly constrained inner-city environment, with unique alignment and property challenges. Two major underground stations, Aotea and Karangahape, are located in a densely developed and complex Auckland city centre environment requiring careful consideration of the spatial constraints, construction methodology and interaction with the extensive network of the existing inground services. Using innovative precast, prestressed, and buildable solutions, we developed the required internal vertical spaces, which created more space for a better user experience. In close collaboration with the large multidisciplinary team across many disciplines and continuous collaboration with the construction team, our designs have been evaluated holistically from a constructability and cost perspective.
Sustainability in infrastructure projects
Designed and constructed to meet the highest sustainability standards, CRL aims to be the benchmark for sustainable infrastructure projects in New Zealand. Sustainable design was fundamental to our approach, and we identified opportunities to deliver efficient, effective, and safe infrastructure that will serve Auckland for years to come.
CRL aims to achieve an Infrastructure Sustainability Council of Australia (ISCA) rating of 15% reduction in embodied carbon, 25% reduction in energy CO2 emissions, and reduced waste to landfill and construction and operational water use. The team uses BIM 360 and Revit to add material information to the 3D model, and the monthly changes are communicated through Power BI dashboards. With the help of an ISCA calculator, BIM model, and dashboard, we can monitor the project’s performance against sustainability targets and explore more efficient methods at each stage of the design.
Mana whenua
The Link Alliance respects Te Tiriti o Waitangi and recognises the enduring presence of Ngā Mana Whenua o Tāmaki Makaurau and their position as Kaitiaki for Tāmaki Makaurau and this project. We are committed to the principle of Kaitiakitanga, managing and conserving the environment as part of a reciprocal relationship, based on the Māori world view that we as humans are part of the natural world, that all-natural and physical elements of the world are related through whakapapa; that all things have mauri, and that protection of mauri is essential.
We are committed to CRL’s aspiration that this project will be the exemplar in sustainability practice – encompassing the four well-beings – environmental, cultural, social and economic –which align and support kaitiakitanga. Our design approach integrates the seven Te Aranga principles, which define the information of the mana whenua matrix.
Awards
Autodesk Excellence Awards (AEC) Infrastructure Design – Large Project (over $500 Million) Winner 2020. City Rail Link is a first in many ways. It is the largest, most complicated transport infrastructure project ever attempted in New Zealand. It is also the country's first completely underground railway line. And it is the first major New Zealand infrastructure project to make an entirely new, comprehensive shift to a digital approach with BIM.
2018 Sustainable Business Network's Supreme Award - the NZI Transforming New Zealand Award. The judges said CRL has "proven the infrastructure industry can reduce greenhouse gas emissions and its environmental impact while developing Auckland's much-needed public transport infrastructure. This will result in an ongoing reduction in both congestion and carbon."
Large Energy User Initiative of the Year category of the Deloitte Energy Excellence Awards 2018, providing recognition for exciting energy-saving projects and the work undertaken to reduce greenhouse gas emissions for New Zealand. "From replacing diesel generators with grid-connected transformers to training haulage drivers in fuel-efficient techniques, CRL's initiatives are expected to reduce energy emissions by over 2,000 tonnes – a 29% reduction project is on target to achieve its goals while also reducing costs and saving time."