Thousands of Ports of Auckland workers are exempt from compulsory Covid-19 border testing, because they are not considered high risk.
Of the up to 6000 workers, 1000 will be tested every fortnight under the new border regime that began this week.
Shipping pilots, those loading and unloading foreign vessels and people transporting crew all have to be tested every two weeks.
Ports of Auckland spokesman Matt Ball says it would be impossible to test thousands of workers in that timeframe and it was a nightmare when health officials asked for it to be done in a first round of surveillance testing last month.
He says only about 1000 people are high risk because they work on the ships.
Ball told Morning Report it was a simple system where people who go on ships are told to get tested and they now have two testing sites on the port. He said they notify employers of other people who come on to the port that they need to get their staff tested.
"We identified very early on that there are groups of people who go on to ships who are higher risk, so we've wanted this for a while. But we don't think it's necessary to test people like truck drivers or people who don't go anywhere near a ship - there's no point in that, they don't come into contact with anyone from overseas."
He said there was not much risk of those who go on to ships passing it on to other staff at the ports because they have been separated into bubbles.
"By creating these bubbles, we've already created systems whereby we're isolating the workforce that is higher risk and need to interact with ships. Even within that workforce, they are separated into smaller bubbles to try and isolate and minimise the risk of people getting Covid and transferring it amongst their workmates."
If there was to be an outbreak, he said the Ports have a finely detailed system of signing in with access cards that would allow for rapid contact tracing.
Ball said things would be a lot more efficient if they could move to saliva testing.
"It would be brilliant, it would be so much easier to persuade people to go and get the test done."