The U.S. Office of Surface Mining Reclamation and Enforcement wrapped up its final environmental impact statement on a request from a former subsidiary of Westmoreland Coal Co. to mine 53 million tons of coal from federal land in New Mexico.

The proposed Deep Lease Extension modification to the mining plan would add 10 to 15 years to the operation's life until 2033, allowing newly formed Westmoreland Mining LLC to produce about 3 million tons of coal annually from the San Juan mine, according to a March 1 decision posted in the Federal Register on March 15. The modification would not add any acres of federal surface land to the operation but would allow miners to recover coal from nearly 4,500 underground acres of federal coal.

However, the San Juan mine sells its coal to the San Juan Generating Station, which is slated to retire in 2022 once its contract with the mine expires.

The agency preferred an alternative that assumes the plant closes its remaining coal-fired units in 2022 and the coal is then sold on the open market, which could include sales to a potential buyer of the plant. Under that option, mining would continue at the same rate from 2023 through 2033.

Should the agency deny the modification, mining will stop in the Deep Lease Extension on Aug. 31. All mining at the mine would stop in December, and the plant would stop burning coal about six months later.

Approving the modification would have a long-term but minor impact on air quality and a permanent but minor effect on climate change, according to the impact statement. The proposal would have a permanent but minor effect on groundwater quality. The impact to surface water quality would be long-term and minor.

The agency will issue a recommendation on the mining plan modification within 30 days of the impact statement's publication to the office of the Assistant Secretary for Land and Minerals Management, which will then make a final decision.