The $2.31 million four-bed unit is designed to help move some people with an intellectual disability from the secure inpatient unit back into the community.
It will serve both male and female patients and will be close to the existing secure unit, housed in Helensburgh House at the Wakari site.
In his report to the Southern District Health Board's hospitals' advisory committee, facilities and site development manager Warren Taylor said the tenders approved so far for the various projects involved were ahead of budget by $46,823.
The $2.31 million Ministry of Health funding for the project was announced in June last year.
There had been some stoppages on the earthworks, being carried out by Waihola Excavation, because of bad weather, he said.
Associated work involving alterations to the 13-bed secure unit Ward 10A, Helensburgh House, expected to take 10 weeks, is being carried out by Keith Mitchell builders.
Board mental health and community services general manager Elaine Chisnall said these alterations were taking place while clients were still within the unit.
This was being closely monitored to ensure any issues which might arise were identified early, she said.
Intellectual disability service clinical staff were working on the model of care for the new unit and the process to identify suitable clients to transfer to it.
Recruitment for extra staff for the unit, including nurses and an occupational therapist, was "well advanced" and there had been a high level of interest in the positions, she said.
Pomeroy Construction Ltd is building the new unit.
Mr Taylor said time was tight on the programme, because the project was due for completion in late October and there had already been some stoppages.
