The GAA's redevelopment programme at Croke Park is in turmoil after An Bord Pleanala unexpectedly ruled that the Hill 16 terrace must be seated. The decision came after an appeal from a local resident against the original permission granted by Dublin Corporation.

As a result Croke Park has a major headache regarding how to maintain as high a capacity as possible without holding up work on the project for too long. Matters have been exacerbated by the industrial action taken by scaffold workers which has brought to a halt work on a number of big building sites around Dublin.

Yesterday's significance lies not so much in the end of the Hill as a terrace - although that will have a sentimental impact particularly on Dublin supporters - but in the disruption caused to the current redevelopment schedule.

GAA PRO Danny Lynch responded to the news on behalf of the association: "The decision came as a disappointment and a surprise on the basis that the GAA would regard the decision as inexplicable. We submitted the revised application for planning permission on the back of three years research and professional advice and on the basis that Dublin Corporation and the city fathers agreed fully with the retention of the Hill as a terrace.

"As indeed did all the official local community representative organisations of which there are five and the public representatives. The impact of this decision will be that Hill 16 which has a culture all of its own will be no more and will require to be seated. That work will have to be undertaken before the development of the Hogan Stand."

In the hope that they were about to win the appeal, the GAA were preparing to demolish the Hogan Stand after this year's championship and have its replacement fully operational by the 2001 All-Ireland final. Now that will have to be put on hold and there are even question marks over the legitimacy of the plans to demolish Aras Daimhin, the administrative offices behind the Hogan.

This was due to go ahead next month and interim office accommodation has already been secured in a nearby part of Dublin 3. Every step of the way will now be subject to interpretation of what is provided for in the conditions.

In the light of the lottery grant of £20 million in the 1997 budget, Croke Park had decided to proceed with the Hogan development ahead of schedule and in tandem with the Canal End redevelopment. Corporate tickets for the new Hogan Stand have been on sale for two months but this doesn't create any financial problems for the GAA.

According to Dermot Power, manager of the Croke Park Redevelopment, there is no deadline on the opening of the new Hogan. "The agreement with those who have bought 10-year tickets is that they firstly move into the Canal End as soon as it is operational and then into the Hogan when it is ready.

"There is no loss of income affecting our financial plans because the funding projections were based on the projected sale of the Hogan and the resale of the Cusack. We hadn't based our figures on the resale of the Hogan." The resale of the Hogan may now be delayed by a year.

"The big impact on us," said Power, "is twofold: delay and capacity. We could seat the Hill tomorrow but while the development is going on at the Canal End, we have to balance the need to keep construction moving with the need to optimise capacity.

"Our advice was that we should be optimistic about being successful (at An Bord Pleanala) and we'll have to look at all our options now. It's impossible to say how long the building strike will continue but the longer it goes on, the tighter it becomes for us. We had hoped to have the lower tier of the Canal End ready for the Leinster final and the corporate level ready for the All-Ireland. Now there has to be concern about that timetable."

Potential loss of capacity for the coming season stands at a maximum of 11,000 - were the building dispute to go on so long that no-one could be accommodated on the Canal End. The problem with throwing bucket seats onto the Hill is that it would lower capacity by at least a few thousand, a shortfall which, combined with the potential deficit at the Canal End, would create a real capacity shortage.

Where the GAA go from here is difficult to envisage. Their project advisers met yesterday afternoon to consider all aspects of the decision and among the options is that of a judicial review - taking An Bord Pleanala to the High Court.

Yet this doesn't seem to hold out much promise of success. For a challenge to be successful, it would need to be based on legal grounds, e.g. that the procedures followed were deficient, that issues were taken into account although not addressed in the appeal, that issues were taken into account without due notice to one of the parties, that regulations were incorrectly interpreted.

Yesterday's decision rested on three essential planks: that the international trend since the Hillsborough disaster in 1989 was towards the provision of all-seater stadia; the recommendations of the 1996 Department of Education Code of Practice; the fact that permission was originally granted by An Bord Pleanala in 1993 for a 79,500 capacity rather than the 84,000 intended under current plans.

The GAA take issue with all three findings, arguing that the conclusions concerning all-seater grounds apply to the experience of soccer in Britain and that properly managed terracing is as safe as seated accommodation. They also argue that independent monitoring, over three years, of crowd egress revised the safe capacity up to 84,000 - a finding accepted by Dublin Corporation.

Nonetheless, these arguments do not create an argument for judicial review. There is in general a provision in relation to quasi-judicial tribunals like An Bord Pleanala, that a finding can be challenged as perverse on the basis that no reasonable person on the basis of the evidence could arrive at that decision.

This is a hard argument to win and in the O'Keeffe Case (concerning the Radio Tara/Atlantic 252 mast), the Supreme Court decided that any material on file which can support the decision of An Bord Pleanala can be taken into account.

The files on this appeal should become public in a few days and it's highly unlikely they will support the charge of a perverse finding. They may, however, reveal procedural inadequacies and support such an appeal.