Gardai will use metal detectors and have obtained the services of a forensic anthropologist for the search of Fiona Pender's remains.
The dig operation is expected to take place very soon.
Sources say officers are "confident" of finding the remains of Fiona in Laois after new information came to light following the arrest of the main suspect in relation to serious separate alleged offences abroad.
Ms Pender, a part-time model and hairdresser, was last seen at Church Street, Tullamore, Co Offaly, on the morning of August 23, 1996.
She was seven months' pregnant at the time and had bought clothes for her baby. Gardai and her family have long been convinced that she was murdered but now there is major hope that her body will be found.
When searches get under way, metal detectors will be used - as Ms Pender had two metal pins inserted in her arm following an accident.
Sources say that a forensic anthropologist will also be used in the event of her remains being found. These are medical specialists involved in the careful collection of old human remains, the cleaning of the bones and analysis in order to establish a profile of the person and how they died.
Sources say that the chief suspect in the case is "extremely violent" and has been engaged in other "very serious crimes, very violent crimes" against women since Fiona disappeared without trace.
While he has always denied any involvement in the suspected murder, gardai have received information that he may have shown another woman the location of where Fiona is buried.
He is facing a possible long stretch in prison before he can be extradited back to Ireland if gardai are successful in their "imminent" searches which are expected to take place close to the same area of the Slieve Bloom Mountains on the Laois/ Offaly border where previous searches took place in 2008 after a wooden cross was found there.
Over the last 12 months, gardai investigating the case undertook a full review of it including looking back on their suspects and the people they had arrested.
It emerged recently that the main suspect, a man in his 40s, was taken into police custody while abroad.
This was in relation to sickening attacks on a woman who was placed into protective care, where she was interviewed by gardai who obtained new information.
Investigators searched extensively for Ms Pender following her disappearance - even draining four miles of the Royal Canal - but found nothing.
The following year, five people were arrested and questioned in relation to her disappearance but were released without charge.
Her 65-year-old mother Josephine, who suffers from ill-health, said earlier this month in an interview: "All I want is my Fiona and her baby back - nothing else matters."
She had previously said that although she had given up hope that her daughter is still alive, she feared she would die before her daughter's remains are found but there is now confidence this will happen.