An Bord Pleanala has written to Irish Water instructing it to extend the deadline for submissions on its application to build a giant sewage plant in Fingal.

The appeals body, which will rule on the Greater Dublin Drainage Project, wants a five-week extension and has asked Irish Water to notify the Irish Aviation Authority of its plans.

An earlier proposal from Irish Water had considered a site in Lusk for the treatment plant which will take waste from all four Dublin local authorities as well as parts of Meath and Kildare, but it is now planning to locate it at Clonshaugh off the M1 close to Dublin Airport.

The revised plan is for a plant at Clonshaugh catering for a 500,000-person population, a sub-station at Abbotstown in Blanchardstown, and an outflow pipe into the Irish Sea off Portmarnock which will tunnel underneath the protected Baldoyle Estuary.

The deadline for submissions and observations closed two weeks ago and 147 were lodged – one with 8,000 signatures attached.

A number of protests have been held and concerns raised over odours and water quality at Portmarnock beach.

Engineers writing on the Board’s behalf sent a letter to Irish Water dated last Thursday stating it had been brought to its attention that information relating to the Environmental Impact Assessment Report had been “inadvertently omitted”.

It adds: “The Board is of the opinion that further public notice is required outlining the nature of these omissions and allowing a period of not less than five weeks for submissions/observations to be made.”

An Bord Pleanala wants new site notices erected advising that anyone who has already paid the €50 observer fee need not do so again but is free to make a further submission.

It advises that Irish Water should notify the Commission for Railway Regulation and Irish Rail “which have separately been notified by the Board” of its plans, adding: “Having reviewed the application documentation, the Board is also of the view that the Irish Aviation Authority should be notified of the planning application.”

Last month, it emerged that Failte Ireland had not been made aware of the proposed sewage plant, which many fear will adversely affect tourism at the Velvet Strand in Portmarnock – the only beach on the east coast to hold both Blue Flag and Green Flag status.

Philip Swan for Portmarnock Drainage Awareness said the extended deadline was good news.

He told Dublin Gazette: “This gives us more time to get our objections in. A lot of people feel very strongly about this.”