The prospect of towering high voltage lines running through Everglades National Park may be dimming.

State environmental regulators, with no objections from Florida Power & Light, have agreed to consider new routes for a controversial power line corridor the utility wants as part of its proposed expansion of the Turkey Point nuclear plant in South Miami-Dade County.

The decision for the first time offers alternatives to FPL’s congressionally endorsed but environmentally damaging “preferred’’ corridor. That corridor would erect a string of 150-foot-tall concrete and steel towers along about seven miles of the park’s northeastern boundary and across sensitive wetlands and rookeries used by endangered wood storks and other birds.

The move doesn’t ensure the Florida Department of Environmental Protection will adopt the new corridors, which could add millions of dollars in land or easement costs, but Everglades Superintendent Dan Kimball called them “a positive development” that could potentially resolve a three-year battle.

The new routes were drawn by an unlikely alliance, an environmental group and the rock-mining industry, in consultation with FPL, park managers, state water managers and Miami-Dade environmental regulators. The county issued a key report last year recommending the state reject sections of a pathway critics argue would harm wildlife, destroy wetlands, disrupt Everglades restoration projects and leave an ugly scar on the park.

“Just the fact we’ve gotten all of these agencies to work together with FPL through the issues is encouraging,’’ said Dawn Shirreffs, Everglades restoration program manager for the National Parks Conservation Association, which submitted one of the routes on Monday.

She credited FPL with being open to a “win-win” solution that would steer the 500 kilovolt towers east of Krome Avenue to the county’s rock-mining belt and sparsely populated western lands largely owned by the state or county.

FPL spokesman Peter Robbins said the utility was reviewing alternatives but not backing away from its routes: “We continue to believe that our proposal will best meet our customer’s needs for reliable electricity and reasonable cost.”

Pinecrest and Coral Gables also are fighting an eastern corridor FPL wants, a 230-volt line up U.S. 1 from Cutler Bay to Coconut Grove. A county report recommended the state deny that route.

FPL applied for the corridors in 2009 as part of its proposal to add two more nuclear reactors to Turkey Point, calling the new lines critical to improving reliability and serving South Florida’s growing population. The lines, including a new substation, are projected to cost some $710 million in an expansion that could run an estimated $12 billion to $18 billion overall.

The utility’s “preferred” western corridor would run along Everglades National Park’s eastern boundary, land FPL currently doesn’t own. To secure it, FPL hopes to swap its secondary route — a narrow, 7.4-mile-long strip it acquired more than 40 years ago. It sits in the middle of the long-parched Northwest Shark River Slough, a target of a critical project intended to restore water flows.

Under a land swap worked out by state water managers, FPL and the U.S. Interior Department, which oversees the park, the park service would grant FPL an easement along the border in exchange for the strip. The deal, approved by Congress in 2009 as part of a massive spending bill, authorizes a potential swap but leaves the final decision to the interior secretary.

Backlash has built since. The park is expected to finish a formal environmental impact study next year but an initial review found either FPL route could have significant impacts on wading bird nests nearby and projects to restore water flow. The park also received more than 11,000 public comments, almost all opposing power lines.

Despite the congressional clearance, FPL could win state approval for an Everglades route but still not secure the corridor if federal agencies reject the swap or permits to build in wetlands. Shirreffs hopes that uncertainty will sway FPL to accept the new routes.

Not all environmentalists, however, are aboard.

“We don’t think there is any need for more power lines or power plants,’’ said Jonathan Ullman, a senior organizer for the Sierra Club.

An administrative law judge is expected to issue a recommendation by next October, with Gov. Rick Scott and the Cabinet making a final call by December.