The overhaul could also include redundancies from the unit later this year.
The 30 labourers maintain and repair the council's water and wastewater infrastructure, dealing with floods, blocks, leaks and other on-site jobs.
This work will be contracted out by the council if its executive management team approves a proposal being considered by affected staff. The 30 workers will be employed under existing terms and conditions by a successful contractor as part of its agreement with the council, although chief executive Paul Orders confirmed that deal was only valid ''at the point of transfer''.
''It will then be up to the staff and their new employer to negotiate terms and conditions.''
Mr Orders led a media briefing on the proposal yesterday, alongside council operations general manager Tony Avery and the council's water and waste services manager, Laura McElhone, who helped write it.
She said the 30 staff were ''understandably'' worried about their futures as well as the continued maintenance and repair of the council's water and wastewater network, about which they were ''passionate''.
Mr Orders said that over the next decade, the ''ageing'' network would cost an additional $30 million to maintain - to a total of about $75 million a year.
Network maintenance cost about $3.9 million a year. Contracting services would save between $300,000 and $550,000 a year, avoid the need for further investment of about $590,000, and see assets worth about $900,000 sold.
Such savings were part of a wider effort to ensure rates increases stayed below 3% a year, Mr Orders said.
In August, the second phase of the overhaul would aim to identify more savings but would not involve further outsourcing. Mr Orders did not rule out redundancies, saying the business unit's structure would be ''looked at'' and staff would have ''certainty'' about their jobs by the end of the year.
Already, the council had not filled some vacancies.
There were 98.2 full-time equivalent staff in the division, including the 30 labourers and two managers whose jobs would be changed under the first phase.
The council's Turakina Rd depot, where they were based, would be leased by a successful contractor for about $190,000 a year or sold, prompting the relocation of nine mechanical and electrical council staff.
Mr Orders said the council wanted to retain full ownership and control of its water and wastewater network - worth about $1.5 billion - and see existing levels of service kept or bettered.
A contractor could use economies of scale and its greater resources to complete work more cheaply.
Dr McElhone said the council started inviting expressions of interest on the proposal yesterday ''to confirm what interest there is''. Contracts would last between five and 10 years.
Affected staff have until June 4 to provide feedback. The proposal will not affect the council's 2013-14 budget, as any savings will be included from the 2014-15 financial year.
