The Dún Laoghaire-Rathdown County Council is expected to seek a court order lifting an injunction preventing work from proceeding on the controversial site of Carrickmines Castle on the M50 next month.
Work on the site has been blocked since February by a Supreme Court interlocutory injunction, which was granted to protesters.
It was granted pending a full hearing into claims by the protesters that the authorities had not complied with relevant conservation legislation at the Carrickmines Castle site.
The road scheme involves removal of part of the earthwork defences, or fosse, belonging to the castle.
However, the Minister for Transport, Mr Brennan, said an order currently before the Houses of the Oireachtas would enable the council to have the injunction lifted.
The order by the Minister for the Environment, Mr Cullen, gives permission for the work to proceed at the site, which is designated as a national monument.
Announcing his decision last July, Mr Cullen said it was "satisfactorily demonstrated that a systematic approach" had been used by Dún Laoghaire-Rathdown County Council for "the archeological resolution of the Carrickmines area".
Ministerial consent was required under the National Monuments Act 1930 in order to interfere with the archeological site at Carrickmines Castle, originally demolished in 1641. The order was placed before the Houses of the Oireachtas in early July. However it must lie before the Oireachtas for 21 sitting days before it can be implemented.
Mr Brennan said it was intended that the order would be acted as soon as the 21 days were completed by mid-November, and the authorities would move to have the injunction lifted immediately.
Mr Brennan acknowledged he had "taken a risk" in directing that work continue on either side of the controversial site in the meantime. Last May a new "supplementary contract" was agreed between Dún Laoghaire-Rathdown County Council and road builders Ascon which did not include the Carrickmines section.
Work will have to get under way at the Carrickmines site by April if the road is to be completed by its August 2005 deadline. Conservationists are expected to continue challenging the proposed work, and if successful the road would be without a key section.
During the summer, Mr Vincent Salafia, a spokesman for the Carrickmines Castle Preservation Group, had two legal teams to challenge the Minister's decision. They have been seeking a solution to the scheme which would retain the castle remains. This has been rejected by Mr Brennan as infeasible, as it would require a new planning process.