Around €10m has been invested in the two facilities but both remain closed due to staffing shortages.
Siptu, with around 70 members connected to both facilities, say their proposals would free up nursing and other staff to work the re.
The 40-bed Deer Lodge, an €8m residential unit in the former St Anne’s isolation hospital in Killarney, was completed last December, but has not yet opened. Its availability could ensure the transfer of over 30 long-stay patients from the O’Connor unit in the grounds of nearby St Finan’s.
It would also allow intellectual disability residents at a unit in Ballydribbeen to be transferred to their own residential living in the community, said Donie Doody of Siptu in Killarney.
Furthermore, a four-bed, €2m high-observation unit in Tralee has remained unopened for the past two years.
“Siptu has accommodated management in every way possible including extensions to the closure date of Ballydribbeen which was first given as December 2015,” said Mr Doody.
“Despite two further extensions to date, only one further client has been transferred out to a community setting and 21 of the original 29 are still accommodated there.”
The union says it was not prepared to tolerate any further delays and gave the HSE until October 31 to complete the closures and the transfer of patients. Failure to do so, Siptu says, will result in members being balloted for industrial action.