Plans to expand the City Rail Link have been agreed by Auckland Council and the Government - a decision which will add several hundred million dollars to the $3.4 billion cost.
The decision comes after original projections for the Rail Link were found not to reflect rocketing growth in rail patronage across Auckland.
The new agreement means the tendering process can now consider widening tunnel sizes, lengthening platforms at new rail stations to cater for nine-carriage trains instead of six, a second Karangahape Rd station entrance and other station work.
The second Karangahape entrance would be built at Beresford Square, to complement the first on Mercury Lane.
A result of new estimates predicted that City Rail stations need to cope with the capacity of 54,000 passengers an hour at peak, rather than the original estimates of 36,000 by 2035.
Auckland Mayor Phil Goff said the growth in rail travel is a success story for Auckland.
"The growth in popularity of rail travel in Auckland required council to take the decision today to increase our investment in the CRL and expand new rail stations to cater for the huge number of people who will be commuting by rail in the next ten years," he said.
"Getting the work done now while CRL is still under construction will avoid retrofitting the system which would double the cost and require the tunnels to be closed for two years for widening within a decade of it being opened."
Transport Minister Phil Twyford said these changes would ensure that when CRL opens in 2024, Aucklanders will get a modern and efficient rail service that benefits the entire transport network for decades to come.
"A decade of under investment in transport infrastructure has bought Auckland to a near standstill," Twyford said.
"Today's decision has allowed us to avoid repeating the mistakes of the past when within 10 years of opening the Auckland Harbour Bridge it had to be expanded from four lanes to eight."
The council's Governing Body voted overwhelmingly to expand work on the City Rail Link.
Costs associated with expanding the scope of work for CRL are confidential while the tender process to procure the work is underway.
Exact costs will be known more precisely early next year once tenders are received but could run to the "low hundreds of millions".
City Rail Link costs are shared equally between Government and Auckland Council.
Goff said the extra work was not expected to delay the CRL's target opening date of 2024.
However, the project is already behind schedule. One of the consortiums on the tender shortlist to build the tunnels and stations withdrew last year – the Herald understands that consortium was led by Fletcher Construction. Then the CRL's chief executive, Chris Meale, retired suddenly in March.
The CRLL board has had to reinstate a competitive tender process, which required it to create a new shortlist of firms with local knowledge and international expertise, while also finding a new CEO. Both have now been done.
Goff told the Herald the tender process is now "back on track" and that "at least two" consortiums have been shortlisted. The new RFP, if approved, will go to them in September.
"I'm celebrating this," he said. "We can do the job properly now."