Washington — Connecticut’s environmental community is dismayed at a study released Friday on the sale of Plum Island because they believe its recommendations do not adequately protect the island’s unique ecology and wildlife.

Curt Johnson, an attorney for Save the Sound, said his group will push back against the study’s conclusions.

“It just really is sad that we have to fight this fight,” Johnson said.

Congress mandated the sale of Plum Island in Long Island Sound once the federal government closes a national biological lab that studies animal diseases there. That will occur after 2019, when a new lab capable of studying even deadlier biological agents is built in Manhattan, Kan.

The General Services Administration’s release of a 408-page environmental impact study Friday is the first step toward that sale.

Adrienne Esposito, executive director of the Citizens Campaign for the Environment, said she’d prefer the federal government keep the property, even if the aging biological lab continues its work there.

“It’s operated without incident for 60 years,” she said.

To Esposito and many environmental activists, the best solution would be for the federal government to keep the island and turn it into a national park.

She’s upset the GSA did not evaluate that option and consider the jobs it would create by boosting tourism in the area.

“The federal government will never have another chance to own land like this,” Esposito said.

The GSA study considered five alternatives. One would ignore Congress’ wish and allow the federal government to keep the 860-acre island. Another would allow the existing buildings and roads on the island to be used for purposes similar to their use now.

A third option is “low density” residential development, allowing the construction of no more than 90 residential units, a plan similar to that of Fishers Island.

A fourth plan would allow high-density development on the island, allowing for 750 residential units and roads to serve those living in them.

The final plan is the “conservation/preservation option” that would allow a private or government buyer to leave the property largely undeveloped.

But Johnson said those options don’t matter, because once the federal government sells the property, its use will be determined by local zoning laws.

He’s also dismayed the GSA did not consider “the option of a true conservation sale” that included restrictions on development.

“But a much better option is for the federal government to keep it,” he said.

Plum Island has been owned by the federal government since 1826 and is home to Fort Terry, a once-active military installation. In 1954 the U.S. Department of Agriculture established a national biological lab on the island and it is now a high-security area. The lab was renovated in the 1990s, but is outdated for the USDA’s current needs for biological research.

Sen. Richard Blumenthal, D-Conn., said he will be “critically reviewing” the GSA’s environmental study, because it “raises well-founded concerns” about whether Plum Island’s dunes and wildlife will be protected in a sale.

The GSA is required to have a 90-day public comment period that will allow environmentalists and lawmakers like Blumenthal to weigh in on the plan.

Public hearings are also planned on the Plum Island proposal in New York and Connecticut in September.