A planning application for a €500m waste water scheme is being lodged today with An Bord Pleanala.
If approved, the Greater Dublin Drainage Scheme will be able to treat waste water for up to 500,000 people in north county Dublin and parts of Kildare and Meath.
Irish Water says the project's needed to allow for the growth of the city up to 2050.
Project manager Jane Chambers from Irish Water says it's a huge scheme.
"It involves the construction of a new orbital sewer which will stretch from Blanchardstown across to Clonshaugh, where the new waste water treatment plant will be constructed.
"And then from Clonshaugh out into the Irish Sea there will be an outfall which will terminate six kilometres from the coast road of Baldoye Bay".