Northland has been rejected because of the difficulty transporting cargo across Auckland city to rail and road hubs in the south.
Both the Firth of Thames and Manukau Harbour were identified as potential options in a 1999 study by the Ports of Auckland.
It was amazing such a wide-range group of interests managed to reach consensus, Young said, though the shipping companies she represents favour an east coast port over one to the west.
Although a Manukau port, preferably at Puhinui, would be closer to road and rail links, it has major issues including weather, swells, dredging, managing and maintenance of the sand bar, and local iwi who have "spent a lot of time cleaning it up and may not want a 75 hectare island in the middle of the harbour," Young said.
The biggest problem from the point of view of the shipping operators is that their current shipping routes are mainly on the east coast rather than the west where weather and swell conditions could potentially close a new port at times.
Three years ago a group of Auckland businessmen sought funding for a full feasibility and economic study on an alternative port at Wiri after their early work suggested the South Auckland site on the Manukau Harbour had several potential advantages to the reclamation work on the Waitemata Harbour that POAL was seeking to do.
At the time POAL said it had concluded moving the port was too expensive and environmentally damaging. Its 1999 report on options had found Wiri would be the most expensive of seven options considered because of the significant dredging required on the bar at the entrance to the Manukau harbour.
The Firth of Thames has 15 metres of water depth almost to the shore by the preferred spot near Waimangu Point but dredging would still be required and local iwi landowners may not want a port situated in their midst due to environmental and cultural considerations, Young said. The big downside is that it would require a large infrastructure build of both heavy rail lines and roads.
The study recommends further technical work be done on both options.
One of the major questions posed is how soon a new port would be needed. The proposal is based on the Auckland container terminal potentially running out of capacity within the next 30 years though that's difficult to predict with any accuracy. Auckland's population is expected to almost double to 2.6 million in the next 50 years and the existing port doesn't have room to handle the likely increased trade on its existing site, especially following vigorous public opposition to planned wharf expansions.
Big cities need ports and the same with trucks - that's how the Marmite and the muesli get to the supermarket. Everyone wants to go to heaven but no one wants to die.
The study group reached consensus on allowing the existing port to have more room now to stay economically viable by adding a 25-metre extension to Bledisloe Wharf to let more ships berth. It would not involve any reclamation work as originally sought by POAL and the piles could be later removed. The proposal would need to go through the normal consenting processes, Young said.
Port opponents won a victory in the High Court last year after it ruled consents for a much bigger 96-metre extension to the wharf were invalid.
How much it would cost to establish a new port is still unclear.
A figure of around $5 billion has been suggested, though the Firth of Thames site would include additional infrastructure costs.
There have been suggestions local iwi might want to partner in the project and land is one of the most significant development costs, Young said.
Road Transport Forum spokesman Ken Shirley said the question is when planning needs to start for a new port as there was a cost to investing too early in an alternative. How the por maintains its effectiveness in the meantime, given it is the country's largest port by value and handles the largest volume of imports, is a huge challenge, he said.
"Big cities need ports and the same with trucks - that's how the Marmite and the muesli get to the supermarket. Everyone wants to go to heaven but no one wants to die," he said.
Shirley said it shouldn't be assumed the government would contribute towards the infrastructure cost of any new port and the port's owner, Auckland Council, would need to consider bringing in private equity and public-private partnerships rather than loading the cost onto the current generation of ratepayers or incurring large, new debts.