Much of the increased import volume would previously have gone into Auckland, he said.
Shippers and trans-shippers had been quick to take advantage of the big ships' economy of scale and speed. The journey between Tauranga and north Asia takes the big ships just 11 days.
Log exports continued buoyant on strong demand from China and record prices for top quality logs, Cairns said.
Log volumes lifted 12.5 per cent to 3.3m tonnes in the six months. Meat volumes rose 17 per cent and steel exports by 50 per cent. Dairy exports increased 3 per cent.
Cars and other imported vehicles were a growing business for the port company, with numbers significantly up on the same period last year, Cairns said.
Ship visits increased by 15 per cent to 890.
The port company, which has more than 40ha of its 190ha territory still undeveloped, was advanced in its 15 year forward planning for growth, Cairns said.
It could handle up to three million TEUs annually without further reclamation.
A new ship-to-shore gantry crane, costing $13m-$15m, had been ordered and the company had applied for resource consent to extend the length of three berths for containers and log cargoes.
The second pleasant surprise apart from lifted earnings guidance from the Port of Tauranga was that its 2018 half year achieved good revenue growth out of strong volumes growth compared to the same period last year, said Craigs Investment Partners senior research analyst Mohandeep Singh.
In the first and second quarters of last year, cargo volumes growth were up 8.3 per cent and 12.4 per cent respectively, but revenue lifted 2 per cent and 6.5 per cent respectively.
"The market had been concerned about good volume growth and throughout the port not translating into revenue growth. Capital expenditure had some impact on that but this is the first sign in a couple of years, and also with Port of Tauranga being the port of favour, that volume has translated into decent revenue growth."
Singh said another pleasing signal from the result was that revenue growth had not been at the expense of margin growth - the port company had not had to add proportionally more costs to achieve the revenue growth. EBITDA has stayed relatively flat at 54.5 per cent compared to 54.4 per cent in the same period last year.