SODA SPRINGS, Idaho | By KEITH RIDLER, (AP) — Federal land managers have released a final plan for a phosphate mine with five open pits as well as reclamation work in eastern Idaho proposed by Idaho-based J.R. Simplot Company.

The U.S. Bureau of Land Management and U.S. Forest Service released the jointly-prepared final environmental impact statement Friday for the Dairy Syncline Mine Project about 14 miles (23 miles) east of Soda Springs.

The five open pits, disposal areas, tailing ponds and other mine workings would cover about 4.3 square miles (11 square kilometers).

The release of the documents begins a 30-day protest period for the bureau and a 60-day objection period for the Forest Service.

Phosphate mining is a major business in southeastern Idaho, where phosphate ore is turned into fertilizer needed by farmers to grow food. Simplot started mining in the area nearly 80 years ago.

Simplot is a privately-held multinational agricultural company engaged in a wide array of activities that include seed production, farming, ranching, frozen-food processing and gene editing. It already has an operating phosphate mine in the area as well as a phosphate fertilizer manufacturing plant in nearby Pocatello.

Company spokesman Josh Jordan said Monday that the Smokey Canyon Mine employs about 250 workers and the Don Plant in Pocatello about 350 workers. Jordan said the new mine will make sure the plant doesn’t run out of phosphate. He said Simplot expects to begin transitioning to the new site sometime within the next decade, likely mining at both areas simultaneously for a limited time.

“The operations are basically going to move to the new area when it’s necessary,” Jordan said. The new mine is expected to be productive for 30 years.

As part of the deal of Simplot acquiring federal land for the new open pits, Simplot is transferring to the Bureau of Land Management and Forest Service a combined 1,100 acres, with some of that becoming part of a roadless area.

Other companies have also mined phosphate, leaving open pits and waste rock dumps. Selenium from the sites has leached into streams or been absorbed by plants. Selenium is needed for life, but it is toxic in large quantities. In 1997, sheep and horses eating selenium-laden plants died. Now, the area has more than a dozen federal Superfund sites needing cleanup.

Simplot will be using new techniques at the new mine to prevent those types of problems, Jordan said. “There are a lot of new mining practices that we’re going to be doing at the new place to limit the impact of selenium into the water,” he said.

The Idaho Conservation League, an environmental watchdog group, was still reviewing the environmental impact statement and didn’t have a comment, spokesman Scott Ki said.

Earlier this year, the Bureau of Land Management approved three phosphate mines as part of the Caldwell Canyon Mine project being developed by Bayer subsidiary P4 Production. Bayer acquired agricultural giant Monsanto, which previously mined the area, for $63 billion in 2018.

That company said the approval would keep 185 miners working as well as nearly 600 jobs at the company’s processing plant in Soda Springs for the 40-year life of the mine.

Experts say the area is rich in phosphate because it was once a 116,000-square-mile (300,440-square-kilometer) inland sea where organic material from fish, plants and small animals was deposited over a 5-million-year span about 265 million years ago.