DATE OF PROJECT 2010 - Present

CLIENT Link Alliance


work completed


New Zealand’s largest ever construction project, the City Rail Link (CRL) connects external train stations and lines in Central Auckland with underground tunnels and station upgrades.

Kicking off in 2010, the project’s vision is to provide a more efficient and rapid transport system for commuters in and around the city centre.

Working for the Link Alliance, who is responsible for delivering the project, Sansom has been involved from the very start across all of our disciplines – tanking, roofing, façade, concrete and tunnelling.

Our Role

With a dedicated team of 30 professionals onsite, Sansom took on various responsibilities as the scope expanded and evolved over time.

At the Mount Eden site, our tanking team was responsible for cut and cover tunnels, ensuring optimal waterproofing and protection. In the Aotea section of the tunnel, we had a roofing team responsible for the trench-like top-down tunnels, focusing on the roof structures. Additionally, our mined tunnel team specialised in underground works and worked with PVC membrane installations in the deepest sections of the tunnel.

We appointed a dedicated project manager who oversaw the entire project, leveraging the expertise of our directors and team leaders to manage minor additional contract within the project. This centralised point of contact provided the Link Alliance with the reassurance that all aspects were being thoroughly supervised and the sub-jobs had the right expertise onsite.

Project Size

The primary challenge came down to the sheer size of the CRL project.

With its vast scale and multiple teams involved, it felt like managing ten separate projects within one – each with their own set of teams, goals, and risks. Unlike typical construction projects, the City Rail Link project involved coordination with multiple project engineers across various areas. It required a delicate balance to ensure we met project deadlines and maintained sustainable and collaborative relationships with onsite teams.

Unlike typical projects where project sequencing might normally take up to a couple of months, it rolled over into years for the CRL project.

While the mobilisation and remobilisation process posed a learning curve, we addressed the challenge by remaining flexible and adaptable. We leveraged the versatility of our team, allocating them where possible to support different disciplines. For example, tanking experts assisted with roofing, as well as assisting the concrete repair team in their surface preparation.

However, having worked on some of the other historically large projects in New Zealand, like Victoria Park Tunnel, Commercial Bay, Waterview Tunnel, and the iconic Pacifica Building, we were equipped with the necessary experience.

Sansom’s Value

One of our key strengths lies in our cross-discipline approach. With various specialised divisions involved in CRL, we could adapt and provide comprehensive solutions as the project progressed.

If one division is unsure about a particular area or aspect of the project, another division will have the necessary expertise. For example, if someone on the façade team needed to clarify what’s happening as we’re transitioning into the bottom of the building, then the tanking team could provide that information.

In addition, our involvement in the design-assist phase proved to be highly advantageous in steering the membrane specification away from a one-size-fits-all approach. This approach has significantly contributed to the overall quality of the infrastructure delivered.

Waterproofing is a complex field, and no single product is suitable for all areas. This was especially necessary for CRL, as each station had unique requirements.

In the design-assist role, Sansom could recommend the best system for each specific area and sequence of construction. By presenting a matrix to the designer, we outlined each option’s risks, benefits, and likely costs. The final selection of the waterproofing system was made collaboratively, with input from the designers, builders, and our team.