Editor's note: This corrects that there was no preferred alternative in the draft EIS, and the public review period runs 30 days, not 60.

A proposal by the National Park Service to swap some land in Everglades National Park with a utility company looking to build a transmission line corridor is dividing conservationists over whether it will benefit or harm the national park.

The proposal, outlined Thursday in a Federal Register notice, calls for the park to swap 260 acres along its eastern boundary to Florida Power and Light in return for 320 acres located in an inholding the utility owns inside the park.

At issue is a corridor that Florida Power and Light has proposed to locate 70, 150-foot-tall, high-power transmission towers to reach two proposed nuclear power reactors next to two existing units at the Turkey Point nuclear facility on the edge of nearby Biscayne National Park. The company's preferred route would take the corridor along the Everglades boundary, though one option would be to run it through the 320-acre inholding. The 2009 Omnibus Public Lands Bill gave the Park Service permission to pursue acquisition of this 7-mile-long tract.

Park Service acquisition of the FPL property, or a flowage easement on the property, is needed to support the mission of the park and is vital to long-term protection of the park for ecosystem restoration purposes, according to park officials. The FPL property is needed to support the goals of restoring the Northeast Shark River Slough and to fulfill the purposes of the Modified Water Deliveries project and the Comprehensive Everglades Restoration Plan.

One alternative in the Park Service's draft Environmental Impact Statement called for the agency to acquire the 320 acres through a purchase or use of eminent domain, the preferred alternative in the final EIS announced Thursday centers on a land swap.

The National Parks Conservation Association cautiously applauded the proposal, with Cara Capp, the group's Everglades Restoration program manager, saying the "land swap presents an opportunity for FPL to be good corporate stewards of our beloved Everglades by sticking to its promise to use only a portion of the exchanged lands, possibly none, for its power line corridor and donate the unused land back to the park to be managed for preservation and restoration."

But Mathew Schwartz, executive director of the South Florida Wildlands Association, said it was a bad deal.

"The environmentally preferred alternative is acquiring FPL's old and unused corridor inside the park - same as they did with hundreds of other private parcels inside the East Everglades Expansion Area - and stopping there.  Giving the company the east side of the park in exchange is not good," he said in an email. "FPL will have the option of building a massive powerline corridor along the floodplain of the Shark River Slough - the lifeblood of water into the park, and the reason that the East Everglades was acquired in 1989 in the first place."

At the NPCA, Ms. Capp said the park advocacy group would prefer to see the Park Service simply acquire the inholding without swapping any land in return. "But under this new alternative, which I’m still assessing, we appreciate that there’s an opportunity that most or possibility all of the swamp lands will be donated back to the park," she said during a phone call.

Ms. Capp said that if the final EIS is formally approved by the Park Service following its 30-day public review period, Florida Power and Light officials would begin trying to obtain land outside the park for their needs. She said there are lands now owned by gravel pit operations and state lands that possibly could be used for the transmission corridor.

“Over the course of the next few years, FPL will try to buy land and piece together a corridor outside of the park," said the NPCA official. If the utility is able to do that, it would donate the 260 acres obtained through the proposed swap back to Everglades National Park, she added.