It's feared marine wildlife could be severely affected by all-night dredging in Dublin Bay to expand Dublin Port.
Dublin Port wants to build a new ferry terminal and expand its container docks -- and plans lots of dredging and piledriving.
Green Party councillor Donna Cooney says it's a serious threat to Dublin Bay's marine mammals.
On Friday she lodged a submission with An Bord Pleanála voicing her concerns.
"[Porpoises] need their sonar to be able to detect fish," she said. "Any sort piledriving or sounds can really damage their ears and they just basically starve after that."
The project's wildlife mitigation plan says a wildlife expert will be watching out for marine life on board vessels involved in piledriving and dredging.
It says contractors won't start dredging or dumping spoil if porpoises are within 500 metres -- or do piledriving if a pod comes closer within a kilometre.
But it says it won't stop if porpoises come closer once they've started.
Dublin Bay is a Special Area of Conservation because of the presence of the cetaceans.
Contractors working in these areas are required to have a marine observer on board and keep a full log of any sightings of wildlife.
But Councillor Cooney says if work is allowed to continue after dark they won't be able to tell if they're there.
"They're a very small little porpoise and they're very difficult to see and they're very curious -- and they will actually come up to any of the boats," she said.
"They have said that they'll contact the National Parks and Wildlife Service if they have any sightings, but I can't see how they can sight them in the evenings," she said.
A spokesman for Dublin Port said it would not comment further while the plan is being considered by An Bord Pleanála.