Opponents of a controversial visitor centre proposed for the Dublin Mountains believe approval for the project may be overturned after An Bord Pleanala rejected a key finding of its own inspector.
Save the Hellfire Club, an umbrella organisation of resident and community groups opposed to the development at Dublin's Hellfire Club in Rathfarnham, said the rejection of the inspector's recommendation provides grounds for a judicial review of the board's ruling.
Plans for the visitor centre - designed as a gateway to the mountains - include a 75-seat cafe, shop, toilets, changing facilities, a walkers' lounge, exhibition space and education centre along with a 50-seat auditorium.
Another feature is a treetop canopy walk over the Killakee Road connecting the centre with Massy's Wood - another popular walking area.
The development is a joint project between South Dublin County Council, Coillte and the Dublin Mountain Partnership.
Most objectors dispute claims by the council that a threefold increase in visitor numbers to the Hellfire Club would not result in significantly more numbers accessing other nearby protected habitats with a negative impact on local wildlife and fauna.
An inspector with An Bord Pleanala said the board could not be satisfied in the absence of a Natural Impact Statement that the centre would not lead to adverse indirect effects on the conservation interests of protected habitats, including the Wicklow Mountain Special Protection Area in relation to merlin, a bird of prey.
"There remains scientific doubt there would be no adverse effects," the inspector said.
As a consequence, she claimed the board was precluded from granting planning permission for the centre.
The inspector said she had "significant concerns with the impact of the project on biodiversity" in relation to habitats and species.
However, she supported the principle of a flagship visitor centre as it complied with the area's development plan.
The project would also address serious parking issues, while a "do nothing" approach was "untenable".
The board said it was satisfied the impact of the project on biodiversity had been "adequately assessed".
Frank Doyle, for Save the Hellfire group, said it was hard to understand why the board ignored the recommendation of its own inspector.
"It seems they are trying to overrule science and ignore their own adviser who had looked at all the details," he said.
The board also decided not to accept the inspector's recommendation to omit the proposed treetop canopy.