Dublin Port said that “one way or the other” an international border post will be needed at the facility by next year as a result of Brexit.
Eamonn O’Reilly, chief executive of the port, has confirmed it will press ahead with plans to build “necessary customs posts” at the capital’s busy shipping dock.
“If it is not needed in March 2019, we have reasonable certainty it will be needed 12 months after that,” he said.
“One way or the other it will be needed. It is an awful lot better to put it in sooner rather than later, or sooner rather than it being too late.”
Mr O’Reilly told the Irish Times in February that the port would seek planning permission to construct the new infrastructure it expects will be needed to deal with additional customs checks.
It followed discussions with the Office of Public Works and other State agencies about “what they require in Dublin Port”, he said at the time.
Speaking to RTÉ’s Morning Ireland on Friday, Mr O’Reilly said the construction phase was imminent.
“In Dublin Port we will build the necessary customs posts and the inspections facilities and have them ready for March 2019,” he said.
“There is such uncertainty we don’t have an option. If we don’t do it and the Brexit negotiations fall apart, no one will thank us for not being ready.
“It is that level of uncertainty.”
Cargo volumes at the port hit a new record of 36.4 million tonnes last year.
Some have suggested that additional checks after the UK pulls out of the EU customs union could lead to 9km tailbacks outside.
Mr O’Reilly said he was already starting to see businesses changing their shipping routes in anticipation of having to circumnavigate the UK from next year on.
Developments include the construction of larger cargo ships designed to connect Ireland directly with the continent, forgoing the usual land bridge connection over Britain.
Mr O’Reilly expects a “significant amount of freight” switching from the age-old Dublin to Holyhead route to Cherbourg, Zeebrugge and Rotterdam.
“The profile of trade is going to change, shipping routes are going to change,” he said.
“Shipping is enormously flexible and people will protect their businesses by making their decisions and I think we are starting to see that happen now.”