A Navajo coal mine and the adjacent electric power plant it feeds have scaled back operations in northern New Mexico.

But the Four Corners Power Plant - operated by Arizona Public Service - intends to continue generating electricity for cities like Phoenix, Albuquerque and Los Angeles.

APS and the Navajo Mine Coal Co. are seeking renewed energy leases and mine permits for future operations at the plant, located southwest of Farmington, N.M.

A draft Environmental Impact Statement on the plans for the coal-fired power plant and mine was recently released by the U.S. Office of Surface Mining Reclamation and Enforcement.

The EIS was presented during an open-house meeting at Montezuma- Cortez High School on May 1. Public comment on the proposals runs until May 27.

In a previous agreement with the Environmental Protection Agency, APS permanently shut down three of the most outdated electric generating units at the plant in December 2013.

The requirement was part of the Clean Air Acts' regional haze rule passed in 2010 to clean up older coal-fired power plants and improve visibility.

The Four Corners Power Plant is requesting a renewed lease to operate until 2041. Under the draft EIS, the remaining two generating units are slated to be upgraded with best available technology to further reduce emissions from the plant.

"Under the preferred Alternative A, units four and five will be retrofitted with selective catalytic reduction devices by 2018," said Dan Tormey, a project manager for OSM. "It translates to fewer pollutants and cleaner air."

According to the EIS, the closure of Units 1, 2 and 3, and installation of additional pollution controls on Units 4 and 5 would reduce nitrogen oxides by 86 percent, mercury by 61 percent, particulates by 43 percent, carbon dioxide by 30 percent, sulfur dioxide by 24 percent and greenhouse gases by 26 percent.

"The improvements take the Four Corners Power Plant out of the 50 worst polluting power plants in the country," said Paul Clark, an environmental technician for OSM.

Operating the two units, the plant will generate 1,540 megawatts per year, enough to power 500,000 homes. With all five units, it produced 2,100 megawatts.

The adjacent Navajo coal mine supplies the needs of the power plant, but now at a reduced rate.

The mine is seeking a 5-year permit to expand mining operations onto 5,600 acres within an approved lease area. Mine operators want extract 5.8 million tons of coal per year, down from 8 million tons per year when the plant was operating all five units.

After the coal is burned, the remaining ash is stored on site in managed piles. The EIS shows the disposal site expanding to store future coal ash from plant operations.

The EPA does not classify coal ash as a hazardous waste, Clark said. "Still, the dry-ash piles are closely managed, reclaimed, and monitored to prevent them from migrating off site by wind, precipitation, or runoff," he said.

Dozens of monitoring wells help engineers make sure the ash is contained, he said. Five new monitoring wells will be installed within the expanded coal-ash disposal area.

An added feature is an interceptor ditch that will be dug between the ash-pile disposal area and the nearby Chaco River.

Socioeconomic impacts of the mine and power plant were reviewed as well. The mine, which was recently purchased by the Navajo Nation, employs 85 percent Native American workers.

The mine and power plant directly employ 1,000 workers. As a result of the downsizing, the mine and power plant will reduce its labor force by 300 workers through attrition.