Work at the controversial Carrickmines Castle site could resume as early as Monday after the Department of the Environment fast-tracked the final approval stage for the work.
Two weeks ago, the Minister for the Environment, Mr Cullen, gave an official direction to Dún Laoghaire/Rathdown County Council to allow plans to be drawn up for the removal and partial destruction of some of the remains of the medieval castle site which lies along the route of the final section of the M50 motorway.
The direction was made under new legislation drawn up following a two-year legal battle with conservationists who were attempting to preserve the whole site.
The delays have added €20 million to the cost of the motorway, bringing its final estimated cost to €596 million.
Dún Laoghaire/Rathdown council was required to send a method statement to the Department of the Environment, which would have to approve it before work could commence on the site.
The council sent the statement to the Department last Monday, and it was expected to take a number of weeks before official approval would be given.
However, a Department of the Environment spokesman told The Irish Times that final approval was issued by the Department yesterday.
According to sources close to the project, work is expected to get under way at the site as early as next week.
"The council is anxious to make a start on the site as soon as is possible, and that could be as early as next Monday."
This week the National Roads Authority said that the final section of the motorway, between Ballinteer and Shankill, would be opened by May.
Meanwhile, Dún Laoghaire-Rathdown Green Party councillor Mr Kealin Ireland expressed sadness at Mr Cullen's decision to allow work to resume.
"The commuting public has waited in traffic jams for far too long. €20 million has been squandered by the Government because of what was, at the end of the day, bad planning.
"The Minister could and should have identified many years ago the existence of this important archaeological site, and moved the route of the motorway.
"Instead, he delayed making this fundamental decision, and the public and our heritage have suffered unnecessarily."