CalPERS, the giant state workers pension fund, has ended several months of uncertainty by signaling to Sonoma County that it intends to move forward with a huge, controversial timber-to-vineyard conversion project near Annapolis.

Called Preservation Ranch, the project would clear up to 1,769 acres of forest for wine grapes on nearly 20,000 acres in northwestern Sonoma County.

It is said to be the largest forest conversion project for agriculture in California in generations. Currently in the study stage, it has drawn nationwide opposition from environmentalists and others concerned about impacts on water resources and wildlife, including struggling salmon and steelhead populations in the Gualala River watershed.

For years, the California Public Employees Retirement System has owned a majority stake in the project through a $200 million investment in vineyard portfolios overseen by a Napa-based vineyard management firm.

But CalPERS last year severed its ties with that firm, Premier Pacific Vineyards, and Sonoma County officials have since been looking to confirm who controls the future of Preservation Ranch.

The answer is CalPERS, state pension fund officials said last week in a letter to the county.

"As of January 1, 2012, the California Public Employees' Retirement System is the owner of Pacific Vineyards Partners LLC," Judy Alexander, CalPERS portfolio manager, wrote in the letter.

Pacific Vineyard Partners is the investment portfolio that controls landholding subsidiaries for Preservation Ranch.

The notice came as CalPERS holds exploratory talks with at least one conservation group on the possibility of selling the sprawling ranch or a conservation easement on it, sources said.

Wayne Davis, a CalPERS spokesman, confirmed the discussions but declined to say if the property was for sale.

CalPERS' letter to the county, however, signaled the pension fund's intent to move forward with the project. It designated Jeffrey Redding, a former Napa County planning director and consultant, and Tom Adams, a former Premier Pacific Vineyards land-use director, as local representatives for Preservation Ranch.

Eric Koenigshofer, a former Sonoma County supervisor who worked as a consultant and attorney for the project, is not currently involved, though he might be brought on in the future, Redding said in an interview.

"We're not stopping the process. It's moving forward," Davis, the CalPERS spokesman, said Monday.

The $233.7 billion pension fund has switched overall management of its vineyard portfolio, including 19 vineyards in California, Oregon and Washington, to GI Partners of Menlo Park.

CalPERS' moves come at a key time for developers of vineyards on forested land. Last week, the Sonoma County Board of Supervisors temporarily halted new hillside and ridgetop vineyard projects requiring tree removal. The four-month moratorium is to allow an upgrade of vineyard rules that would, if approved, apply to Preservation Ranch.

The project would permanently set aside 15,000 acres for timber operations, dedicate 2,700 acres for a private wildlife preserve and donate 220 acres for a public park expansion.

But critics, including a coalition of environmental groups, local tribal members and others say those measures are inadequate. They have pressed CalPERS to abandon the plan and have called for protection of the entire 19,652 acres as a timber reserve.

Opponents plan to ramp up their efforts today with a presentation to the Board of Supervisors of 90,000 signatures from those who say they oppose Preservation Ranch and large timber-to-vineyard conversions in general. A Los Angeles woman started the online petition last year using the website Change.org.

CalPERS officials, meanwhile, have quietly reached out to a national group that specializes in forest conservation deals.

Chris Kelly, California program director for The Conservation Fund, said he was called last month by Judy Alexander, the CalPERS portfolio manager, and that he has had several conversations with CalPERS officials in recent weeks.

Kelly said he indicated the group would be interested in talking further about purchasing a conservation easement over the ranch or working with other groups and backers on an outright purchase of the property.

The Conservation Fund owns and manages more than 50,000 acres of forest in Mendocino County for sustainable timber production and sale of carbon credits. One of their properties, a 13,900-acre tract in the Gualala River watershed, borders Preservation Ranch.

"I just told them its something we've done in the neighborhood," Kelly said. "The ball is in CalPERS' court."

County officials are set to meet Friday with Redding, the Preservation Ranch consultant, to discuss a revised schedule for the project's environmental impact report.

Release of the much-anticipated study, which is said to cost up to $2 million, would kick off the public comment and hearing process. The report was originally due at the end of 2011, but was pushed back last year to mid-2012.

David Schiltgen, the Sonoma County planner overseeing the application process, suggested it may be delayed further.

"With this whole changing of agents and consultants, there's been some delay," Schiltgen said.