Accounts are being taken of their time at the unit along with details of the practices used in dealing with patients there.
Medical and child care experts are also being asked to review the material gathered to provide their professional views on the treatment of children staying at the unit.
The Constabulary began a criminal investigation in November last year into reports of physical and sexual abuse against patients who were at the adolescent unit between 1969 and 1995, when it closed.
To date, a total of 75 people, who spent time at the unit as patients or knew someone who stayed there, have spoken to police.
The majority of those that have contacted the force have made allegations in relation to the way they were treated while staying there. Others are witnesses to treatment at the unit or have made a third party report.
Hertfordshire Constabulary takes all reports of sexual and physical abuse seriously regardless of how long ago the offence may have occurred and we have specialist officers who are trained in supporting victims through the investigation process.
Those who believe they have been a victim of this type of abuse can make contact with police by calling 101, using our online reporting option through the Op Meadow web pages, or anonymously via Crimestoppers on 0800 555 111 or through their anonymous online form at www.crimestoppers-uk.org.
A central email - firstname.lastname@example.org - has been set up in order to receive any referrals and to answer queries. This email address will be monitored seven days a week and specialist officers aim to be in contact with any reporting person within 72 hours of their initial contact.