Florida International University is pursuing a complicated land swap that would allow it to expand into the county fairgrounds next door.

The key to the deal: 350 acres of West Miami-Dade wetlands the state bought 13 years ago for $3.7 million as part of an Everglades restoration project since scrapped by the South Florida Water Management District.

FIU’s plan calls for securing the parcel at an attractive price — a free, 99-year lease — and then giving it to Miami-Dade County in exchange for the existing 87-acre fairgrounds. A new home for the 60-year-old Miami-Dade County Fair & Exposition, as well as a county park, would then be constructed on the new site.

FIU pitches the proposal as a win-win, helping a university with a fast-growing medical school that has run out of real estate while also preserving undeveloped land near the Everglades.

Environmentalists haven’t been won over.

They contend the plan would destroy wading bird habitat, encourage building beyond the county’s urban development boundary and short-change the state’s cash-strapped Everglades restoration efforts. They’re also concerned FIU is trying to fast-track a deal that has undergone little public scrutiny, pointing to legislative language circulating in Tallahassee that would authorize the transfer.

“FIU is flexing its political muscle to try to push this,” said Laura Reynolds, executive director of The Tropical Audubon Society.

Sandra Gonzalez-Levy, FIU’s senior vice president for external relations, said she wasn’t certain who wrote the proposed legislation but insisted FIU was not trying to ram through a deal. She also acknowledged the proposal faces legal and political hurdles, including possible conservation covenants and wetlands development restrictions. Under the county charter, voters would have to approve the plan in a countywide referendum before FIU could build on the old fairground .

“We are in a discovery and exploratory phase right now, so there are many questions that are still unanswered,” she said, adding that FIU welcomed public review of the proposal.

With the school projecting attendance to grow by 10,000 over the next five years, she said FIU must find more space. Even with planned additions at its North Miami campus, FIU needs more room for labs, its new Herbert Wertheim College of Medicine and med student housing.

For FIU, the fairground has an obvious advantage of being next door to its main campus at the junction of Tamiami Trail and Florida’s Turnpike. The fair moved there in 1972, a few years after FIU’s establishment.

The university broached the expansion about a year ago, meeting with Miami-Dade’s Parks and Recreation Department, which owns the fairgrounds, and the non-profit company that runs the fair under a 90-year lease signed in 1995. Both agreed to join a group to evaluate potential new fairground locations, evaluating 16 sites that fit the criteria of at least 250 acres, most needed for parking up to 18,000 cars. The fair, which attracts more than 500,000 patrons each March and ranks as the largest in the state, also rents three exhibition halls many weekends.

Manny Rodriguez, chairman of the board of Miami-Dade Fair & Exposition Inc. and a regional director for Florida Power & Light, said the fair’s board was open to helping FIU — “a valuable entity in this community” — if the right spot could be found.

“We’re happy where we are but also realize FIU is land-locked,’’ he said.

Kevin Asher, supervisor of special projects for the parks department, said the aim was to accommodate the fair’s needs as well.

“No one is holding a gun to anyone’s head,’’ he said. “It’s an open exploration.’’

The top choice: a chunk of wetlands along Tamiami Trail a few miles east of Krome Avenue that the water district was considering selling as “surplus.” The agency, which manages Everglades restoration for the state, has been downsizing staff, programs and projects in an effort to balance its shrinking budget.

The 350 acres, purchased in 1999 for about $3.7 million under the state’s Preservation 2000 conservation land-buying program, was intended to be part of a much larger project called the Bird Drive Recharge Area. The goal was to create a sprawling basin that could hold stormwater and groundwater seeping from Everglades National Park, help recharge Miami-Dade’s nearby drinking water wells and expand wetlands habitats bordering the park.

But the project was plagued with problems. The district encountered difficulty finding willing sellers and faces a slew of lawsuits from other area landowners. Water managers dropped it after engineers in 2008 deemed the project “unfeasible’’ and not worth the high costs — largely because holding water in the area could raise flood risks to surrounding properties.

That decision left the agency with a checkerboard of some 930 acres.

FIU formally expressed its interest in acquiring the largest pieces in a Dec. 7 letter from school president Mark Rosenberg to the district. He said the school was interested in acquiring about 500 acres through a “state-to-state transfer,” spelling out the proposed fairgrounds move and the creation of a county “environmental legacy park’’ that would protect much of the remaining wetlands. The request has since been reduced to 350 acres.

Water managers did not respond to calls for comment. The Florida Department of Environmental Protection is reviewing FIU’s proposal but has not yet taken a position, said spokeswoman Jennifer Diaz.

Parks officials, fair executives and FIU see the site as promising but insist the idea remains preliminary.

“It’s a lovely parcel... but there is still a long way to go,’’ said Asher.

Though the land could come free, the cost of building new facilities could be problematic. Asher said one estimate put a $12 million price on wetlands mitigation, which typically involves restoring wetlands elsewhere to compensate for development. It’s also unsettled who would pay for the move.

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FIU’s Gonzalez-Levy called the new site superior to other options and not so far west from current fairgrounds to be inconvenient.

“What’s it going to take, five more minutes, the driving time?" she asked.

The property sits just west of the urban development boundary (UDB), she said, but FIU would not ask to move the line established to discourage suburban sprawl. She also noted that parts of it are already degraded, over-run with exotic plants, rutted by off-road vehicles and used as a dumping ground.

Environmentalists stress they don’t oppose FIU’s expansion but they argue it should not come at the expense of Miami-Dade’s disappearing wetlands.

Megan Tinsley, Everglades policy associate for Audubon of Florida, said her group has been pressing the district to find new ways to use land originally purchased with the intent of preserving habitat for wildlife, including endangered wood stork, which feed in the area.

“Even if you’re not going to build the project you previously envisioned, there needs to be a more robust evaluation of what to do with it,’’ she said.

She also said FIU’s plans conflicted with county land-use restrictions as well as state and federal covenants tied to land purchase programs. She also questioned whether state and federal regulators would approve a massive parking lot on wetland outside the UDB .

“We definitely wouldn’t want to see a lot of asphalt poured out there,” she said.

Tinsley believes environmentalists’ call for re-evaluating the district land sale had been getting traction — at least until FIU stepped in with proposed legislation and “changed the game.”

Rep. Carlos Lopez-Cantera, chair of Miami-Dade’s legislative delegation and House Republican leader, said he was aware of FIU’s desire for the land swap, and is supportive.

“I believe that FIU does their due diligence before they bring issues to elected officials from their community,” Lopez-Cantera said.

But he cautioned against assuming lawmakers would act with the legislative session more than half over. It’s too late for a individual bill to be filed but language still could be tacked onto an existing bill as an amendment.

“Is it guaranteed to happen? That is uncertain,” Lopez-Cantera said.