A proposal to shift Auckland's port to Manukau Harbour comes with major environmental and iwi concerns, coupled with cautious optimism over potential economic impacts.
The Government has released a major new report on options for relocating the Port of Auckland's freight operations.
It follows another report released in December, that recommended moving the port to Northport, just south of Whangārei.
This report, produced by Sapere, took a longer-term view at freight capacity, and concluded Manukau as the preferred option when looking at a minimum 60 year freight capacity.
It also found it the most cost-effective, given its proximity to freight hubs in South Auckland, and to produce the least carbon emissions.
It found the port's current downtown Auckland location had about 30 years' capacity and there was a 10-15 year window for making a final decision on relocation, which meant it was not as urgent as the previous finding.
Auckland Mayor Phil Goff welcomed the proposal, which he said showed neither Northport nor the Port of Tauranga were viable options for relocating the port in the long-term.
The current port land needed to be returned to the people of Auckland, but had to be done in a way that will not disadvantage residents or businesses, Goff said.
However, Wayne Brown, a Northland engineer who authored the first report - Upper North Island Supply Chain Study (UNISCS) - which recommended Northport, said Manukau was too shallow and dangerous.
His concerns were also backed by Infrastructure Minister and Northland MP Shane Jones, who said he was "absolutely unimpressed with the quality" of the report.
"This report wants to go to the most dangerous harbour in New Zealand, Manukau."
The 2017 Coalition Agreement between New Zealand First and Labour agreed to
"commission a feasibility study on the options for moving the Ports of Auckland,
including giving Northport serious consideration".
"That has been adherred to ... but there is no consensus," Jones said.
NZ Shipping Federation executive director Annabel Young said moving the port to Manukau Harbour would require large amounts of dredging to allow room for big ships to get in, which would likely raise environmental issues and be costly.
With most of New Zealand's ports on the eastern coastline, it would mean longer trips for the ships.
However, Transport Minister Phil Twyford said all major ports in the world needed to dredge, and that experts cited in the report had downplayed those issues.
The latest report showed even sharing capacity between them Northport and Tauranga only had about 60 years' growth capacity.
On top of this would be increased freight costs and carbon emissions, compared to having the port in Manukau.
"We don't want to lock in inefficiencies or greater carbon emissions. It is a huge decision, we have to get it right for the entire economy."
The previous report had predetermined Northport as the preferred option, Twyford said.
"This is too big a decision for New Zealand to take that kind of approach."
Due to Covid-19 there were delays in policy analysis being completed, meaning a final decision would be left until after the September election, he said.
Perspectives compiled through interviews with the Government's Treaty of Waitangi partners around the Manukau Harbour for the report also expressed a range of concerns over moving the port there.
The health of the Manukau Harbour was the subject of one of the first claims ever lodged in the Waitangi Tribunal (Wai 8), so it was "not surprising" iwi and hapū had "significant concern" about the environmental and cultural impacts of dredging and land reclamation, report authors said.
In particular, Ngāti te Ata said the re-establishment of a commercial port in the Manukau could be the "straw that breaks the camel's back".
However, those concerned also said a port could bring the spotlight onto the harbour for environmental and cultural restoration.
Iwi also recognised the work and business opportunities, ranging from constructing and operating the port, to service industries and even tourism.
Meanwhile Ngāti Whātua Ōrākei, which owns a vast area of land near the current port site, said it was "concerned to ensure there is no delay in moving the Auckland Port operations from the city".
Whatever decision was made, the report authors warned iwi needed to be closely involved in the decision-making process.
• New port on the Manukau Harbour, the preferred option, considered "technically feasible although difficult to consent". Has the most freight capacity options in a 60-year window, and also most cost-effective given proximity to freight hubs in South Auckland. Also lowest carbon emissions.
• New port on the Firth of Thames, the second most-preferred option, also having sufficient long-term capacity. However, seen as the most expensive option.
• Port of Tauranga expansion, found to be second most cost-effective, but only able to provide sufficient berth capacity until around 2060, which is not materially longer than the estimated 30-year capacity at Ports of Auckland.
• Northport expansion, seen as the third most cost-effective but only able to accommodate 30 years' growth. Also high carbon emissions due to transporting freight to Auckland.
• Shared capacity increase at both Northport and the Port of Tauranga could accommodate the freight task at 60 years, but raises transport costs and carbon emissions.