A community effort to keep Annadel State Park open that includes a $100,000 donation from philanthropist Henry Trione is expected to get a big boost today from Sonoma County's Board of Supervisors.

The board is expected to give county officials the authority to enter into a one-year agreement with the state allowing the county to take over operations of the popular 5,000-acre park in east Santa Rosa.

The deal, which requires approval from the California Department of Parks and Recreation, would keep Annadel open past a July 1 deadline when dozens of parks statewide are slated to close for budget reasons.

The agreement also would represent an unprecedented role for the county in state park management, one that Supervisor Valerie Brown, whose district includes Annadel, said could extend past June 2013, when the agreement is set to expire.

"I can't imagine the state gets in a better financial position to take it back," she said Monday.

Trione's $100,000 donation was made last July but only now is becoming public. He could not be reached for comment Monday.

Trione was instrumental in helping to acquire the property that would become Annadel State Park in 1972 and thwarting a massive development proposed on the property surrounding Lake Ilsanjo.

Trione put $300,000 to $400,000 into the Annadel deal, and purchased a 400-acre portion of the property that he developed into a polo field and the Wild Oak subdivision. His home is adjacent to the park.

County Regional Parks said it will cost $277,737 to operate Annadel for a year. The money has been raised through private donations and a one-time payment of $50,000 from state parks, which also has committed to retaining a supervising park ranger at Annadel, an in-kind value of $100,000.

The county's regional parks agency will manage Annadel as part of its adjacent Spring Lake Park operation.

"To some extent it really gives us an opportunity to take it to another level," said Caryl Hart, the county's regional parks director.

The county plans to install a day-use parking area on Channel Drive in an effort to prevent people from parking outside the gates and walking or biking into Annadel for free. The cost would be $7, which is what people pay to park at other regional parks, including Spring Lake.

County supervisors have yet to approve the fees, which are not part of today's agenda, Hart said.

Under the county's proposed agreement to run Annadel, regional parks officials could allocate fees generated at Annadel or Spring Lake for either park "in reasonable proportion to the intensity of their use."

The terms also indemnify the state from any legal claims that result from the county's operation of Annadel.

Hart, who also is chairwoman of the California Parks and Recreation Commission, called the potential agreement a new model for operating state parks.

"We've created a whole new infrastructure for helping these parks thrive," she said. "It's not just a matter of keeping Annadel open. It's looking at the whole system and how to make things better going into the future."

Brown acknowledged feeling some "anxiety" over the county shouldering more of the financial burden with state parks. She said she hopes the state eventually will provide more "taxpayer money" toward helping the county.

Five state parks in Sonoma County were originally on the closure list. Agreements are in place to keep three of the parks open — Sugarloaf Ridge State Park, Jack London State Historic Park and Petaluma Adobe State Historic Park. Besides Annadel, efforts also are under way to keep Austin Creek State Recreation Area in Guerneville open as well.

The effort to save Annadel involves a new partnership between county parks, the Sonoma County Regional Parks Foundation and the Parks Alliance of Sonoma County.

A new volunteer organization, Friends of Annadel Park, also is marshaling the efforts of hundreds of volunteers.

You can reach Staff Writer Derek Moore at 521-5336 or derek.moore@pressdemocrat.com.