Valerie is on the move.

The two-metre wide tunnel boring machine helping build the multi-billion City Rail Link is about to begin the next stage of an underground journey through downtown Auckland.

Auckland Transport said the machine, named Valerie in honour of the strength of double Olympic champion Valerie Adams, has completed the first 290m of tunnelling and pipe-jacking work between Victoria and Swanson streets.

Valerie is now being refurbished in preparation for the next part of the journey.

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It will soon be lowered down the shaft to begin the final 200m stretch towards Wellesley St, expected to be completed in April.

The stormwater diversion is needed before the rail link cut and cover tunnel construction of twin tunnels can be done by Connectus, a McConnell Dowell and Hawkins joint venture.

A smaller tunnel boring machine is also working under Victoria St, diverting the Orakei sewer main and enabling the existing sewer to be strengthened under the future mid-town Aotea Station.

Construction on the rail link, which will link Britomart and the city centre to the western line near Mt Eden began in December 2015.