ROCKFORD, Ill. (WTVO) — A controversial Rockford airport expansion project, on a piece of land with environmental interest, has been allowed to continue.

The Federal Aviation Administration (FAA) announced on Monday that work on the “Bell Bowl Prairie” is allowed to continue.

“Chicago Rockford International Airport will retain more than six acres of the Bell Bowl Prairie. This includes more than three acres of high-quality prairie. Any excavation and shrub and brush clearing work in the project area will occur between October 15 through March 15 to avoid impacts to the Rusty Patched Bumble Bee and avoid the prime nesting seasons for the black-billed cuckoo and the upland sandpiper,” the FAA wrote.

The prairie, located near Beltline Road, would become part of an expansion of the Chicago Rockford International Airport. Environmental advocacy groups have been pushing to save the piece of land owned by the airport, which they say is home to important prairie grasses and an endangered bee species.

The airport said that a 2019 environmental impact study found no concerns.

In 2019, the FAA cleared the Greater Rockford Airport Authority to start the operation, and construction began in 2020. The next year, the Illinois Department of Natural Resources (IDNR) identified the Rusty Patched Bumble Bee in an area near the project.

When Airport Authority was notified about the endangered insect, they stopped construction and the FAA consulted with the U.S. Fish and Wildlife Services (USFWS) about the Endangered Species Act regarding the bee and other species.

In October 2021, The Natural Land Institute (NLI) sued the FAA, USFWS, and Airport Authority, claiming they failed to comply with the National Environmental Policy Act (NEPA) and with the Endangered Species Protection Act in a federal court case.

Work was paused in 2022.

The expansion project is expected to cost $50 million.