DUBLIN developers Cosgraves have been directed by An Bord Pleanala to produce a comprehensive environmental impact statement on their proposed high-rise office and apartment development at George's Quay in Dublin 2. The developers, along with architects Skidmore Owings Merrill and planning consultants Frank Belton and Associates have discovered that 12 appeals have been lodged against the corporation's decision last December to grant permission for an 80-metre high tower in the centre of the site opposite the dome of the Custom House. If built, the tower block would be the tallest building in Dublin. The developers have until May to submit the EIS to the board after which it will be circulated to the appellants and other objectors. It is then expected there will be an oral hearing with the likelihood that the board will not make a decision on the case until October - more than a year after the corporation's planning decision. Cosgraves have a fall-back position, however. If the board eventually refuses permission for the high-rise development, Cosgraves can revert to the earlier scheme done for Irish Life by Keane Murphy Duff which would involve erecting a cluster of seven office buildings in the middle of the site and two more on the Moss Street frontage. This permission, granted by the board in 1991, was made valid for ten years, twice as long as usual.