"None of these booms are effective in open seas conditions and every bit would have been required in the harbour in the event of the vessel [Rena] being floated off the reef and towed into port," Mr Cairns said.
He said oil spill preparedness was funded by an industry levy, paid by those sectors whose activities raise the risk of a marine oil spill.
"It will always be very difficult to demonstrate to the general public that adequate procedures are in place to handle low likelihood, high consequence risks such as this grounding," said Mr Cairns.
He told the shareholders he was woken by a phone call at 2.30am on October 5 with "the terrible news" that the Rena had run aground on the reef, 24km from Mount Maunganui.
Port of Tauranga's compulsory pilotage limit, set by Maritime NZ, was a seaward arc of 5.5km centred on North Rock at the Mount and including all the commercial area of Tauranga Harbour.
Mr Cairns said Maritime NZ and Port of Tauranga staff, and the Harbourmaster attended the Rena at 4am on October 5.
Initial hopes were to refloat the vessel at high tide by removing some cargo, which did not prove feasible given how far the Rena ended up on the reef. It was virtually impossible to get heavy-lift project cargo vessels close enough to remove some containers, Mr Cairns said.
The port provided Maritime NZ with staff, work boats, tugs, office and cargo shed space and exclusive use of Number 5 berth and the adjacent quay to lay out their materials and transport them to the reef. An area alongside Shed 22 was also being used to bring ashore salvaged containers.
Mr Cairns said daily helicopter reconnaissance of shipping channels out to Mayor Island had allowed the port to provide regular updates of any navigational hazards to shipping line customers.
He said there was no diminishing the fact that the Rena grounding would be New Zealand's worst maritime accident from an oil spill. However, the risk profile was improving each day.
"We take our hats off to the brave salvors who are working in the most unimaginable and risky conditions getting the oil off the vessel, and also to the 6700 volunteers in Tauranga."