The San Juan Mine is located on the western flank of the San Juan Basin. The underground mining operation targets the Fruitland Formation Number 8 coal seam, the shallowest coal-bearing formation; the seam averages 11 feet in thickness in the permit area.

San Juan is located in northwest New Mexico, and is one of the largest underground coal mines in the world. San Juan has implemented unique management standards and tools in our commitment to achieving “Zero Harm” to people, our host communities, and the environment.

Mined coal is transported by either chain conveyor or mobile equipment to conveyor belts that remove it from the mine. At the surface, coal is conveyed to a stacking tube. The coal is then loaded into large-capacity haul trucks using frontend loaders and taken to coal stockpiles or taken to the preparation plant where it is crushed, sampled, and transported by covered conveyor to the Generating Station.

Longwall Mining
Longwall mining is the primary mining method used for the San Juan Mine underground operation. The mine layout consists of main and sub-main entries to access the coal reserve. Room and pillar methods are used to support the mains and sub-mains. The underground mine is operated as a bleederless mine, meaning the mined-out areas of longwall panels are sealed and not ventilated.

Subsidence occurs progressively behind the longwall mining area, resulting in a surface expression that generally ranges from four to eight feet. The amount of subsidence depends on the thickness of coal extracted and depth to coal: shallower depth to coal and thicker coal units generally creates more subsidence. Surface disturbance associated with the underground mining operation is limited to access roads and drill pads for boreholes (described below), along with long-term support and ventilation facilities. This disturbance represents a relatively small percentage of the lease area (approximately 8-12 percent).

San Juan Mine has constructed a redundant ventilation system comprised of two fans, one 20-foot ventilation shaft, and four portals. This redundant system allows for maintenance and backup in case of a failure of one of the attached fans. The existing ventilation system is expected to be used throughout the life of the mine. The ventilation shaft is provided with an emergency escape system.

Mine layouts consist of main and sub-main entries where coal removal is required to access the reserve. Mains and sub-mains typically have five to nine entries depending on mining conditions, ventilation, and access requirements. The entries are used for intake and return air ventilation, coal haulage, and personnel and material transportation. The entries are separated as necessary by stoppings to facilitate ventilation. Coal in the pillars of mains and sub-mains developments is typically not recovered. Coal may also be left in the roof and floor of the entries and crosscuts to assist in ground control.

Mining Setup and Coal Delivery
Development using room and pillar mining techniques uses a system of continuous miners, haulage vehicles, and a conveyor system to cut and transport the coal out of the mine. Continuous miners cut the coal from the seam. The cut coal is then loaded from the miners into battery-powered haulage vehicles for transport to the feeder-breaker. Alternatively, coal mined from the longwall is dropped onto a conveyor of steel chains and metal bars, which transports the coal to the stage loader where it is sent through the feeder-breaker to crush and reduce the coal grain size. It is then transferred to the main conveyor for transport out of the mine. The conveyor system operates approximately 12 hours per day, 4 days per week. At the surface, coal is conveyed to a stacking tube. The coal is then loaded into large-capacity haul trucks using frontend loaders and taken to the coal preparation plant where it is crushed, sampled, and stacked.

There are two active coal stockpiles at the San Juan Mine, known as Juniper and Northfield, each with a capacity of approximately 3 million tons. Surface haulage vehicles typically operate 18 hours per day for 10 shifts per week.

The coal preparation plant is a crushing and stacking facility.