The initial works on the long-awaited dig are set to take four weeks before the full-scale excavation gets under way in mid-July.
The full process is expected to take approximately two years to complete.
Located within the Dublin Road estate in Tuam, the entire site, including the Memorial Garden, is under forensic control and will be closed to the public for the duration of the works.
A 2.4-metre hoarding around the perimeter will be installed during the preliminary works to preserve the forensic integrity of the process.
St Mary’s mother and baby home came to global attention in 2014, when the work of local historian Catherine Corless revealed that up to 796 babies were likely buried in a makeshift crypt at the facility.
Their causes of deaths included deformities, heart conditions, whooping cough and influenza, and their burial in a septic tank caused outrage across the world and forced the government to establish a commission of inquiry into mother and baby homes.
It was also revealed there were no burial records for the children who died there during its years of operation.
In 2017, the Commission of Investigation into Mother and Baby Homes found that "significant quantities of human remains" were buried in a sewage facility at the former mother and baby home.
The commission’s final report, published in January 2021, revealed up to 9,000 children died in similar circumstances in other religious-run institutions across the country, including Sean Ross Abbey in Roscrea, Co Tipperary; Castlepollard in Co Westmeath and Bessborough in Co Cork.
The homes for unmarried mothers and their children were established because it was considered a sin and shameful to have a baby outside wedlock. Many of the babies were adopted against the mother’s wishes.
The institution in Tuam was run by the Bon Secours Sisters between 1925 and 1961.
The building was demolished in 1972 to accommodate the construction of housing, but the unmarked mass grave has mostly remained untouched.
A special body was established to oversee a staged approach to the recovery of human remains from the site, known as the Office of the Director of Authorised Intervention, Tuam (ODAIT).
The ODAIT has briefed survivors and relatives of those who died in the facility about the timeline for the start of the works. A day for family and survivors will also be held in the coming weeks to allow them to view the site.
The update on the timeline was provided by Daniel MacSweeney, who leads the ODAIT.
Describing the process as “unique and incredibly complex”, he said the a fixed timeline for completion is still unclear.
“The work is expected to take approximately 24 months to complete. The final timetable will depend on many variables, some of which may only become fully clear as the work progresses,” he said.
“As the site will be under forensic control at all times during the excavation, we have encouraged families and survivors to visit the site, if they wished to do so, in recent weeks.
“In addition, we are putting in a place plans to facilitate a day for family members and survivors to include a visit to the perimeter of the forensically controlled site to view the works being undertaken. This will take place in the coming weeks.