Work on Auckland's City Rail Link project is a step closer to completion as a tunnel-boring machine is due to finish its first leg this week.

The machine dubbed Valerie - named after shot put Olympic gold medalist champ Valerie Adams - has been simultaneously excavating and installing a new stormwater pipe under Albert St since last November.

When it arrives at the Swanson St reception shaft this week, it will have travelled almost 300m.

Auckland Transport posted about the latest developments via its social media pages, Facebook and Twitter.

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Showing two photos of the underground pipe, a caption said: "The City Rail Link has achieved a new milestone with the breakthrough of the first section of the pipe jack shaft.

"Valerie - the 2m-wide tunnel boring machine simultaneously excavating and installing a new stormwater pipe under Albert Street - will finish the first leg of its journey in a few days and will be moved to Victoria Street to tunnel 200m to Wellesley Street.''

The Valerie tunnel-boring machine is due to be dismantled and then taken back to the Victoria St shaft, where it will start its second tunnelling journey to the Wellesley St shaft.

It will travel 200m once it arrives there.