Sonoma County supervisors Tuesday voiced support for a move that would expand the county’s central landfill by permanently turning over operations to a national solid waste contractor, starting with a 20-year deal with worth an estimated $547 million.

The latest solution to Sonoma County’s garbage situation is a 20-year contract worth more than half a billion dollars that would outsource operations of the solid waste system.

It would give control of the county’s troubled 42-year-old central landfill west of Cotati to an Arizona company with $8 billion in annual revenue. But it would keep the site, and the county’s five waste transfer stations, in public ownership.

The proposal is being called the largest public-private business deal in county history and is headed to the Board of Supervisors for the first time Tuesday.

A short-lived ceasefire between Sonoma County government and its largest labor union broke down this week over last-minute changes to the pay and benefits proposed for the county’s highest-paid employees.

Attorneys for Sonoma County government’s largest labor union are set to decide early this week if a vote that appeared to approve a new labor contract for the union will stand.

Sonoma County government’s largest labor union voted Tuesday by a slim 52 percent majority to approve a proposed labor contract that would balance a short-term salary freeze with future-year wage growth.

The outcome of a standoff between Sonoma County’s government and its largest union could be decided today in a contract vote by workers.

Sonoma County government administrators have told members of the county’s largest labor union that they could be disciplined if they participate in a planned Feb. 28 strike and the walkout later is found to be unlawful by a state labor board.

The largest group of unionized Sonoma County government employees plans to strike next month to protest what it says is county inaction on a union proposal to save taxpayer money and several other issues it says amount to unfair labor practices.

The largest union of Sonoma County government workers on Monday soundly rejected a proposed contract that would have cut their pensions and pay. Eighty-three percent of those workers, represented by Service Employees International Local 1021, who voted opposed the proposal.