Critics such as Heart of the City, the central city business lobby group, ask how a rail network, currently being upgraded at huge expense to lure motorists on to public transport, is expected to cope with the resultant seven-fold increase in the number of containers carried by rail - from 106,000 to 700,000 in 30 years.
Whether a supporter or opponent - or just one of the bewildered - councillors next Tuesday should take Ports of Auckland publicist Matt Ball at his word when he told the Herald this week "there is no immediate need to make a decision on which port development option to pursue and indeed that plan will continue to evolve as demand, technology and shipping changes".
In other words, councillors will not be risking abuse from port expansion supporters if they call time out for a cup of tea and a think.
Instead of laying themselves open to being portrayed as wreckers of the economy, they will be able to take credit for initiating a long-needed assessment of port policy, not just for the upper North Island but ideally for the country as a whole.
What keeps getting overlooked is that Auckland councillors, on behalf of all Aucklanders, own the port company, all 100 per cent of it, not the other way round. It is for Aucklanders to say whether we want the throat of the Waitemata Harbour gradually choked with mudcrete, not the servants we hire to run our port.
The PricewaterhouseCoopers report last year into future North Island port demands looked at various options. Commissioned jointly by the ports of Auckland, Tauranga and Northland, it considered, among other things, the possibility of Auckland port activities plateauing at present levels and the other two ports expanding to handle future growth.
Side-effects of this would be double-tracking the Tauranga-to-Auckland railway line, improving rail links to Northport and improved roading between the three cities.
There was a warning in accompanying documentation that "any substantial changes to the configuration of the upper North Island port system would have significant costs that would likely outweigh the benefits". What we need is detailed modelling to back or rebut these and other assumptions.
After initially supporting a second-stage review of development options to examine these wider economic impacts, Auckland Council decided to break away and back Ports of Auckland's expansionary plans. It's a decision made without any in-depth consideration of the long-term effects on Auckland.
Like the "100% Pure" promotional whopper now embarrassing New Zealand in China, expanding the port at its existing downtown location promises a very different outcome for Auckland than the "most liveable city" vision Mayor Brown is pushing.
The Unitary Plan is to be the rulebook for Auckland's development for the next 30 years. On a chapter as important as this, what's needed is balanced, informed and considered input, not just the one-sided wishlist of port bosses who can't see past their own ingrained imperatives. Even they say there is no need for haste, so why the rush?
First we need some facts.
What will be the social and economic effects of long-term port expansion at the existing site? Would co-operation and some form of partnership between Northport, Tauranga and Auckland make more social and economic sense?
