Youth offenders detained at a notorious adult prison will be sent to a newly-revamped national children's detention centre from next summer.
As construction work to overhaul the Oberstown campus in Lusk, Co Dublin began today, Children's Minister Frances Fitzgerald confirmed the timeline for the long-awaited state commitment to get children out of adult facilities.
"The objective of ending the detention of children in adult prison facilities has been recognised by successive administrations since at least the 1980s," Ms Fitzgerald said.
"There have been numerous attempts over the years to progress this project but this Government has, at a time of major constraint for the public finances, committed the resources needed to resolve this issue once and for all."
In a move the Children's Rights Alliance described as "a major step forward for vulnerable children", the minister confirmed the transfer of 17-year-old boys from St Patrick's Institution will be given priority.
She said three new residential units, build to increase campus capacity, will be completed in the third quarter of 2014, meaning those in the Victorian prison could be re-housed at Oberstown as soon as July, August or September next year.
Three remaining residential units will be delivered by the third quarter of 2015 and will be used to replace existing run-down accommodation at Oberstown.
The construction work will also include the development of education, recreation, security and other ancillary facilities, meaning all detention services will be available on one main site.
The current capacity of the campus is for 44 boys and eight girls.
As the children's minister turned the sod at the site north of Dublin city centre, she announced a construction contract had been awarded to BAM Building Ltd to the value of 56.4 million euro.
The Office of Public Works released the funding for the project.
Teams of specialist contractors providing electrical work, mechanical engineering and security doors and gates have also been appointed.
"This is the culmination of a long process to design, fund and procure this project which, by increasing capacity on the Oberstown campus, will deliver on the Government's commitment to end the use of St Patrick's Institution for children detained by the courts," Ms Fitzgerald said.
"Following on from my decision as an interim measure to assign responsibility for 16-year-old boys to the Oberstown campus during 2012, this project will ensure the extension of the child care model of detention to all children under the age of 18 years."
The Oberstown campus is currently made up of three parts - Oberstown Boys School, Oberstown Girls School and Trinity House School.
The first phase of three residential units will be built to increase overall campus capacity and a further three - built in 2015 - will replace the Oberstown Boys building.
The other two buildings will be retained to operate as part of the overall national campus.
Children's Rights Alliance chief executive Tanya Ward said the current practice of holding boys at St Patrick's had been "a serious blot on Ireland's human rights record".
"Ending the detention of children in St Pat's is a major step forward for vulnerable children," she added.
"The Government should be commended for following through on this commitment and securing 56.4 million euro to redevelop Oberstown in the midst of a recession. It just shows what can be achieved when children are placed at the heart of decision-making."
The Irish Penal Reform Trust (IPRT) said the announcement on the end of St Patrick's was momentous.
Liam Herrick, executive director, said: " Given the current pressures on fiscal resources, IPRT believes that the construction of new facilities at Oberstown is a significant statement of the Government's commitment to the rights of children, including children in conflict with the law."
Mr Herrick called for clarification on when 17-year-olds will be moved out of St Patrick's.