A group is exploring whether the 500-acre Misty Isle Farm could be purchased for farmland preservation and transformed into a multi-use site.

“There is no other piece of land on the island with so many assets,” said Tom Dean, who heads the Vashon Maury Island Land Trust and is leading the effort. “This is a once-in-a-lifetime opportunity.”

For the past six months, Dean and several other high-profile islanders, as well as representatives from King County and PCC Farmland Trust — a nonprofit that works to preserve threatened farmland — have been meeting regularly and working to determine whether the massive estate once owned by the late Tom Stewart could not only be purchased and protected, but one day hold farms and other resources or amenities that would benefit Vashon.

While the property near Paradise Valley hasn’t been on the market in years, committee members say they believe that if a nonprofit were to fundraise millions of dollars for the ambitious project, it may be able to negotiate a buy.

“We all came to the conclusion that yes, we think there’s a good idea here, and a window of opportunity,” Dean said.

The exploratory committee, which members say is still in the early stages of research, will now look to develop a rough business plan for the site, gather more community feedback and have an appraisal done on the property. Should they craft a plan that pencils out, Dean said, they’ll begin approaching potential donors to gauge interest in funding such an endeavor.

“I have vetted this idea with leaders in the community, and I have gotten universal excitement around it,” Dean said. “We’re trying to learn as much as we can and piece together something that makes sense.”

Dean estimates that a property appraisal alone will cost up to $70,000, funds he called at-risk seed money. A purchase would likely cost tens of millions.

“This community would have to have some skin in the game,” he said. “This doesn’t get off the ground without some private donors on Vashon.”

Misty Isle Farm, the sprawling estate Stewart pieced together decades ago from multiple parcels, went on the market in 2007, when the wealthy businessman moved his company, Services Group of America, to Arizona. Stewart died in a helicopter accident in 2010.

Originally priced at $125 million, Misty Isle, which includes rolling pastures, miles of wooded trails, a 6,500-square-foot home and several other structures, was said at the time to be one of the most expensive residential properties in the world.

The estate has since been taken off the market, but Dean said many islanders remain concerned that once the real estate market recovers, the property, with pieces owned by both Stewart’s family and his company, will eventually be purchased for development. Some have suggested a resort or hotel may go in, and Dean believes there are development rights to build up to 48 homes there. For years, he said, there’s been talk of trying to protect it.

“Instead of letting some developer snatch that up and do something we don’t like that doesn’t fit the character of the island or doesn’t support the island that much, can we put this property in community ownership and control?” he said.

The 10-person exploratory committee, which includes farmers, conservationists, lawyers and real estate experts, is now vetting many ideas for the ecologically diverse place.

Large swaths of the property are already protected as farmland — the site once held Stewart’s black Angus cattle and before that the Wax Orchards farm. Group members imagine it could be the future site of a large-scale farming operation, creating local jobs and providing a constant supply for buyers both on and off the island. Produce, dairy, even meat produced at the farm could be sold to local grocery stores and organizations such as the school district or Vashon Community Care, something Dean said would “close the loop” and keep dollars on the island.

Merilee Runyan, the president of the Vashon Island Grower’s Association and an organizer of the exploratory committee, said so far the idea had local farmers’ support.

“Most of the farms on the island are small acreages intensively cultivated,” she said. “I think all of us would benefit from more land on which to grow crops.”

Amenities established at the site — perhaps a farm-to-table restaurant or vacation rentals — could generate income there, Dean said, something that would help cover the high costs of maintaining the property but that committee members believe could be more controversial than farming.

“I don’t see this penciling out without some sort of agro-tourism business,” he said. “Maybe instead of rows of mansions, it’s rows of yurts and people are coming out for weddings and eating in restaurants with food supplied on-site.”

From a conservation standpoint, Dean said, he’s excited about the prospect of preserving acres of habitat, including the stretch of Fisher Creek that runs through Misty Isle, and keeping miles of trails open to hikers, runners and equestrians. There’s also been talk of offering farm education at the site, perhaps through internships or partnering with a local college, and providing low-income housing for workers.

“It is a great piece of property for the community because it has the potential to contain all these different possibilities,” Runyan said.

While hopeful about their ideas, both Dean and Runyan say a plan will only take off if it’s one islanders support — and give generously to.

Though the property isn’t currently on the market, Dean said committee members have been in touch with members of Stewart’s family and representatives of his company who have given them hope. Those they’ve talked with won’t say much and don’t seem to consider the group a serious buyer, Dean said, but some have indicated that family members aren’t interested in keeping the place and if a buyer should approach them with funds in hand, they’d likely consider an offer.

Rich Wilson, president of Development Services of America, a subsidiary of Services Group of America based in Arizona, said on Monday that he hadn’t heard that anyone was seriously looking at the property and declined to comment on the situation.

“The property is not marketed for sale. That’s about the best I can tell you right now,” he said.

Dave Speers, a Seattle broker who handled Misty Isle’s listing when it was on the market, said every now and then he gets calls about the property, but he’s had no serious inquiries in years. He’s not sure what the estate would sell for now, he said, but he would forward any offers to Stewart’s family. He said he did speak with someone from Vashon recently.

“We’re not engaged with them at all,” he said, referring to the exploratory committee.

Dean said more conversations were in order should they move forward, but a broker close to the situation suggested a buyer — either the land trust or a newly created nonprofit — may be able to purchase the property for $25 million.

“He’s not the owner, so we don’t really know how it would all play out,” Dean said.

While he believed any buyer would have to purchase the entire thing, Dean said, it’s possible that portions with homes or other structures on them could be sold off afterward, recouping some of costs. And like the performing arts facility that Vashon Allied Arts is currently fundraising to build, it’s likely that a working farm at Misty Isle would require an endowment for operations.

“It’s incredibly exciting and it’s incredibly daunting at the same time,” Dean said. “I think part of the challenge is … even though it’s fun to noodle on, how do we make this pay for itself?”

The concept, nonetheless, is gathering interest from large regional players. PCC Farmland Trust, which has preserved more than 1,100 acres of working farmland in the Northwest, has been involved in the committee’s talks and is “very interested,” Dean said.

Christie True, director of the King County Department of Natural Resources and Parks and a Vashon resident, has also been to committee meetings. She said that should the group craft a viable plan for the site, the county would likely consider helping fund its purchase. Money from the county’s parks levy and Conservation Futures Tax are set aside specifically for projects such as this, she said. Conservation Futures funds helped the county purchase the former Glacier site, True noted, and thecounty recently put forward $11 million to purchase the development rights to a 43,000-acre tree farm in southeast King County. State and federal programs, she noted, also fund farmland preservation.

“It’s definitely not a crazy idea,” she said. “We’re always looking for what are the opportunities for conservation and preservation throughout King County, including Vashon.”