Northport at Marsden Pt has been ruled out as a replacement for the Ports of Auckland after a study deemed it will be unable to cope with the growth in Auckland freight together with its own demands.
Ports of Auckland could be moved to a new "super port" in the Manukau Harbour or the Firth of Thames at a cost of $4 billion to $5.5 billion.
That is one of the main findings of a Port Future Study report due to be released today and obtained by NZME.
The report concluded that in the long term Ports of Auckland will not be able to continue operating at its current downtown location and a new site needs to be found.
Northport and Tauranga ports will be unable to cope with the growth in Auckland freight together with their own demands, the report says. Therefore, they were discounted as feasible long-term options.
The Port Future Study - made up of representatives from business, Ports of Auckland, community groups and iwi - has narrowed down the possible new port locations to Manukau Harbour and the Firth of Thames, subject to more investigation.
In the short to medium term - between now and 2065 - the report recommends no further reclamation at the Fergusson container terminal but a need for extra berth length at Bledisloe Wharf for vehicle imports and other bulk cargo.
The report does not make specific recommendations, but discussions have taken place among the study's working group and wider reference group for an extension of about 25m at the end of Bledisloe Wharf. Ports of Auckland are understood to be seeking a 65m extension.
The report, commissioned by Auckland Council following last year's battle over wharf extensions into the Waitemata Harbour, has made a number of recommendations that will be considered by the council's Auckland development committee next week.
In the 2014-2105 year, Ports of Auckland handled 970,000 containers, three million tonnes of freight and 250,000 cars.
The number of containers is expected to grow to three million over 50 years, the report said.
It found three constraints to the port's volume growth: the footprint required to operate the port, berth lengths to accommodate more visits by larger cruise and cargo ships, and transport connections.