One of Florida's biggest sugar companies is poised to begin a massive expansion of rock mining in western Palm Beach County's farming region.

United States Sugar Corp. proposes to allow Stewart Mining Industries of Fort Pierce to mine lime rock on 4,000 acres of sugar-cane land 5 miles northwest of 20-Mile Bend.

The mine would be bigger and farther west than the roughly 1,200-acre rock quarry that Palm Beach Aggregates has been excavating west of Lion Country Safari.

Stewart proposes to mine 100 acres a year for 40 years.

Nick Stewart, president of Stewart Mining, said pits created by the mining would store water from U.S. Sugar's cane fields.

"There would be many lakes that would be established," Stewart said. "There would not be a 4,000-acre hole in the ground."

Still, the proposal drew alarm from environmentalist Rosa Durando, who has warned for years that expanded mining poses a threat to the sugar region north of the Everglades.

"It destroys the land with no real plan of rehabilitation," said Durando, conservation director of the Audubon Society of the Everglades. "To me, it's about the worst insult you can put on the Earth."

Stewart needs a permit from the state Department of Environmental Protection, along with approval from county commissioners.

County rules allow mining on farmland only if it supports agriculture, road or water projects.

Alan Whitehouse, a DEP environmental specialist, said the state will consider the mine's effects on wildlife and wetlands.

Palm Beach Aggregates found a lucrative use for its mining pits last year when it sold 1,190 acres for $188 million to South Florida water managers, who plan to use the pits as reservoirs for Everglades restoration.

Stewart said he didn't know whether U.S. Sugar planned to use its lakes for any environmental water storage.

"I think that could be a possibility in the future," he said. "That's going to be U.S. Sugar's concern."

The Clewiston-based sugar company announced Monday that it has signed a lease with Stewart Mining. U.S. Sugar spokeswoman Judy Sanchez declined to say how much rent her company would receive.

"This mining lease is a part of U.S. Sugar's effort to maximize its land assets during a business and global-trade atmosphere that has forced us to reduce the acreage devoted to sugar cane," according to a statement issued by U.S. Sugar Senior Vice President Robert Coker.

Earlier this month, DEP officials surveyed the U.S. Sugar property, which is south of the J.W. Corbett Wildlife Management Area.

It is directly west of 14,500 acres that the state's other major sugar company, Florida Crystals Corp. of West Palm Beach, has indicated an interest in developing.