Campaigners opposing a giant sewage plant which was approved by An Bord Pleanala last week are set to legally challenge the decision before Christmas.

Objectors have already raised almost half of the €10,000 needed to launch a judicial review and papers will be lodged in the High Court within the next five weeks.

The Bord’s decision to grant Irish Water permission has met with harsh criticism from locals who fear the massive project will have a “catastrophic” effect on Dublin Bay.

The ‘Greater Dublin Drainage Project’ (GDD) includes a monster sewage plant in Clonshaugh, a biosolids storage facility in Kilshane, pumping station in Abbotstown and outfall pipe discharging off Ireland’s Eye into the Irish Sea.

Sabrina Joyce-Kemper, founder of ‘Solution not Pollution’, told Dublin Gazette: “The decision wasn’t really a surprise for us … once we read the conditions we were able to fine-tune our legal argument.

“There’s massive support out there; people are very worried. It will affect hospitals, hospices, schools nearby, they’re all concerned about it.

“We can’t put the two biggest waste water treatment plants pumping into the Irish Sea 20km apart – particularly into a marine environment that is protected.

“It’s essentially like someone pouring buckets of poo into the bath while you’re in it.”

Among the “compelling arguments” objectors will bring to the High Court are those of marine experts and microbiologists who warn that the GDD project will kill sea life.

Sabrina said: “It’s not just our back yard – this is the Irish Sea we are talking about, it’s everyone’s back yard.

“The sea is a finite resource and deliberate pollution not only impacts habitats and marine life, but tourism, fishing and human health.”

Fingal County Council last week welcomed the Bord’s ruling and Irish Water described it as a “landmark decision”.

A water specialist warned on Monday that delays in building the plant would put added pressure on the overloaded Ringsend facility, leading to “more failures”.

Jenny Lawler, of DCU Water Institute, said this would likely cause more discharges into Dublin Bay during periods of heavy rain.

Fianna Fail TD Darragh O’Brien estimated the scheme could cost in the region of €1.2 billion, rather than the €500 million price tag it was originally given.

FF TD for Dublin Bay North, Sean Haughey, said: “Sewage should be treated as close as possible to the source of its production.

“Irish Water should instead plan for a number of smaller treatment plants around the Greater Dublin Area which would be a more environmentally sustainable policy.”