The Link Alliance consortium has signed an NZ$1.66bn ($1.12bn) design-construction alliance contract to deliver ‘Package 3’ of the City Rail Link project in New Zealand.

The signing of the agreement follows the selection of the consortium by the project promoter in April when Link Alliance also secured an NZ$75m ($50.7m) contract for early works.

Under the latest contract, the consortium will design and build the 3.45km train line extension, including a 3.2km-long tunnel to connect Britomart station with Mount Eden station.

An earth pressure tunnel boring machine with a diameter of 7.18m will be used to build the underground tunnel. Additionally, it will build three new stations along the route.

The Link Alliance consortium includes Vinci Construction Grands Projets (main contractor) and Soletanche Bachy International and Downer along with designers AECOM, WSP-Opus and Tonkin & Taylor.

The consortium and the City Rail Link are expected to create a single team to deliver the project works.

Once complete, the City Rail Link project is expected to facilitate connectivity with downtown Auckland. It will be developed to accommodate 54,000 passengers per hour at peak travel times.

New Zealand Transport Minister Phil Twyford said: “It will double the capacity of our rail network, reduce travel times into and through the central city, and help take cars off the roads, as well as driving investment in our region.

“The signing of this agreement will help ensure the delivery of the world-class transport system our city needs.”

In April, the total project cost was revised and increased by around NZD1bn ($670m) to NZ$4.419bn ($2.97bn).

The increase was due to the expansion of the scope, construction inflation costs and higher allocation towards the contingency risk allowance.

Construction of three smaller sections has already started, while the City Rail Link is expected to be completed in 2024.