The Sonoma County Board of Supervisors on Tuesday unanimously approved an agreement that permanently privatizes operation of the county's central landfill west of Cotati but keeps the site in public ownership.

The deal with Arizona-based Republic Services is set to begin this summer in a 20-year contract with an estimated worth of $547 million. But it depends on cities committing their garbage to the 170-acre Mecham Road site in order to take effect.

County and city representatives have advanced the deal over the past three years as the best way to enable a $60 million landfill expansion, cap and stabilize rates that have shot up under county operation, and settle more than $90 million in shared liabilities for the central site and seven former dumps across the county.

Recycling programs, including recovery of commercial food waste and construction material, are set to expand under the deal. The initial impact on curbside garbage service is projected to be no more than a 4 percent increase on the average monthly household bill.

"I think we've turned over almost every piece of trash in trying to reach our common goals," said Supervisor Shirlee Zane, who led the solid waste discussions.

The vote comes four years after a controversial and ultimately unsuccessful attempt by the county to sell the troubled landfill to Republic Services. It was closed for five years starting in 2005 because of water quality concerns raised by state regulators.

The deal would ensure an in-county disposal site for at least two decades, require regular reporting of greenhouse gas emissions and set hard targets on annual recycling goals.

"We've come a long way," said Ann Hancock, executive director of the Santa Rosa-based Climate Protection Campaign, which opposed the 2009 sale but supported the new deal.

Republic Services, the country's second-largest solid-waste firm, would be responsible for all closure and post-closure costs for the landfill, including $52 million in financial assurances.

The deal could face a late-breaking legal challenge from a litigious environmental group, the Petaluma River Council, and landfill neighbors opposed to the dump's expansion.

They filed a 77-page letter with the county Tuesday requesting a new environmental impact report for the landfill.

The current two reports date to 1998, but have been updated three times since 2009, according to the county.

The opponents say those updates do not sufficiently account for impacts from a $5 million sorting facility to be built and run by the Ratto Group of Companies, the county's main trash hauler and a subcontractor to Republic under the deal.

(You can reach Staff Writer Brett Wilkison at 521-5295 or