The Navajo Tribal Coal Lease is located on the western flank of the San Juan Structural Basin in northwestern San Juan County approximately 15 miles southwest of Farmington, New Mexico. This basin is an asymmetric, structural basin with a northwest trending axis parallel to the Hogback Monocline in northwest New Mexico. The basin is bounded on the northwest by the Hogback Monocline and on the north by the San Juan Uplift. The eastern rim is formed by the Brazos Uplift and the Nacimiento Uplift. The Zuni Uplift and the Chaco Slope form the southern margin of the basin while the Defiance Uplift and Four Corners Platform complete the northwestern basin rim. The San Juan Watershed lies on the eastern edge of the Colorado Plateau and extends from northwestern New Mexico into portions of northeastern Arizona along the New Mexico/Arizona border, southwestern Colorado, and the southeastern most corner of Utah. The San Juan Watershed is approximately 140 miles wide by 200 miles Jong, and covers a total area of 21,600 square miles (URS 2009).

The rock strata in the southern part of the lease area strike north-south while the strata in the northern part strike northeast-southwest. The geologic formation dips gently to the east toward the center of the San Juan Basin at an angle of one to two degrees, and steepens toward the outcrop areas where the fairly abrupt monocline (Hogback) can be observed.

The stratigraphic section in the lease area reflects the Late Cretaceous transition of shallow marine depositional environment to a terrestrial fluvial depositional environment. During the late Cretaceous geologic period, the shoreline of a vast shallow inland sea shifted back and forth across the basin and ultimately receded, depositing alternating marine and nonmarine sediments. The strata in the lease area have not been intensively folded, and faults in the strata have limited displacement and extent.

The mine lease area surface, and adjacent areas, are comprised of the Lewis Shale, Pictured Cliffs Sandstone Formation, Fruitland Formation, Kirtland Shale and unconsolidated alluvial deposits in the valleys of the San Juan River, Chaco River, and the Chaco River tributaries.

All coal mined at the Navajo Mine SMCRA Permit Area exists within the Fruitland Formation, the shallowest coal-bearing formation. The extent of the Fruitland Formation’s coal seams differs across the Navajo Mine SMCRA Permit Area. Eight primary coal seams and eight corresponding overburden or interburden horizons are present within the Navajo Mine SMCRA Permit Area (BNCC 2009). Individual coal seams are as much as 20 feet thick, and average 6 feet in thickness. [05/01/2015 Final Environmental Impact Statement-Section2, p. 5]

The Navajo Mine - dragline operation with 2 draglines.

Dragline stripping is the primary mining method used for multiple seam mining operations at the Navajo Mine. The typical sequence for multiple seam mining is as follows:
1. Vegetation and topdressing removal
2. Overburden drilling and blasting
3. Overburden removal
4. Coal drilling and blasting
5. Coal removal
6. Interburden drilling and blasting
7. Interburden removal
8. Repeat steps 5 through 7 for each minable seam.
[05/01/2015, Final Environmental Impact Statement-Section2, p. 5]

The coal seams at the Navajo Mine are exposed in pits that range in width depending on the size of the dragline equipment that is being used to expose them. Pit depths range from 5 to 240 feet, and pit lengths range from 1,000 to 15,000 feet. [05/01/2015, Final Environmental Impact Statement-Section2, p. 6]

Overburden Drilling and Blasting
After all suitable topdressing material is removed, rotary drills are used to drill overburden blast holes. Blast-hole diameters range from 5 to 10 5/8 inches. Blast holes typically are drilled to the top of the coal seam that is being uncovered (until coal is encountered) and then backfilled with 1 to 10 feet of drill-hole cuttings to prevent coal shattering and any accompanying coal loss during blasting. However, some holes may be drilled to a specified elevation of 3 to 7 feet above the coal seam and not backfilled to reduce coal loss due to the movement of the overburden over the coal seam. [05/01/2015, Final Environmental Impact Statement-Section2, p. 9]

Once a set of blast holes has been drilled, the overburden is blasted by one of two methods, cast or standup blasting. In both blasting methods, the blast holes are loaded with bulk explosives and the explosive column is detonated by a ½-pound to 3-pound primer initiated with either a nonelectric detonating cord, nonelectric blasting caps, or electronic/electric blasting caps. The bulk explosives typically consist of ammonium nitrate and fuel oil (ANFO), an emulsion and ANFO blend, or bagged slurry product. To ensure proper blast sequencing, the shots are controlled using in-hole delays and/or surface delays. [05/01/2015, Final Environmental Impact Statement-Section2, p. 9]

All blasting is conducted under the supervision of OSMRE-certified blasters. The blaster present at the firing of the blast, as well as all other personnel assisting blasting operations, are responsible for having a thorough working knowledge of the site-specific performance standards and requirements. [05/01/2015, Final Environmental Impact Statement-Section2, p. 9]

Overburden Removal
The tops of the coal seams are exposed in parallel cuts, or “strips,” with each contiguous sequence of strips comprising a pit. Overburden and interburden materials, which are also included in the strips (commonly referred to as “spoil”), are removed primarily using electric-powered walking draglines. Strips vary in width as a function of the size and capability of the dragline operating in each pit. Pits vary in depth from 5 to 240 feet (measured from the topographic crest to the toe of the highwall), depending on the stratigraphic location of the recoverable coal seams and individual operating constraints. In most cases, a minimum pit width of 100 feet is required to facilitate safe operation of the mobile mining equipment. Pit length varies from 1,000 to 15,000 feet, depending on pit geometry and planned mining sequence. [05/01/2015, Final Environmental Impact Statement-Section2, p. 9]

NTEC utilizes two methods of dragline stripping: conventional side casting and conventional spoil-side stripping. Conventional side casting is generally used on upper layers and consists of moving the material to the side as dragline stripping, or removal of the overburden and interburden, continues. Conventional spoilside stripping is generally used on lower layers and entails excavation and removal prior to placement in the spoil area. Geologic conditions, such as depth of coal and number of coal seams, along with the size of the dragline and its basic configurations determine the methods of stripping used in any given pit. [05/01/2015, Final Environmental Impact Statement-Section2, p. 10]

In addition to primary dragline stripping, dozers, front-end loaders, and haul trucks are used as needed. Dozers and truck/loader stripping is used in isolated areas where dragline stripping is not practical (e.g., mesas, pits with short lengths, constrained spaces). Dozers and truck/loader stripping are also used within dragline pits on thin overburden and interburden horizons where dragline operations are not effective. [05/01/2015, Final Environmental Impact Statement-Section2, p. 10]

Coal Drilling and Blasting
After the coal is exposed by stripping operations, the top of the coal is cleared using small front-end loaders. The resulting diluted coal is piled on the spoil side of the pit. The coal seam is then drilled in preparation for blasting. Thin coal seams are generally ripped with dozers rather than blasted. Blasting of the coal seam is similar to the blasting of overburden, as described above. [05/01/2015, Final Environmental Impact Statement-Section2, p. 10]

Coal Removal
Once the coal is blasted or ripped, it is mined using large front-end loaders that load large-capacity haul trucks. The entire thickness of the coal seam is mined in one pass, except where a non-coal unit (parting) separates the coal beds, or where the coal quality makes a distinct division in the coal seam. In the former case, the top part of the coal seam is mined by the front-end loader, the parting is ripped by dozers and pushed into the adjoining spoil area, and the rest of the coal seam is mined with front-end loaders. [05/01/2015, Final Environmental Impact Statement-Section2, p. 10]

Although the operations are engineered and planned to recover the maximum amount of coal, a small percent (approximately 8 percent) is lost in “wedges,” also known as “ribs” at the top and bottom of coal seams. A coal wedge or rib is the portion of the coal seam left to serve as a safety barrier either on upper coal seams to prevent trucks and front-end loaders from accidently going over the highwall, or on lower spoil-encroached coal seams to increase spoil stability and reduce the occurrence of loose material rolling into the active work area. In both cases, front-end loaders are used to recover as much of the coal wedge as safely as possible once the coal seam is mined out. [05/01/2015, Final Environmental Impact Statement-Section2, p. 10]

The coal preparation plant is a stacking and reclaiming facility and not a coal cleaning operation.

Coal delivered by railcar (or occasionally by haul trucks) to the preparation plant located in Area I is unloaded into one of two stations into underground hoppers. Fully enclosed feeder systems transfer the coal from the hoppers via electric conveyors into redundant systems consisting of enclosed single-roll crushers, coal quality samplers and scales. The coal is crushed to a ¾-inch to 1-inch diameter suitable for the Four Corners Power Plant (FCPP) pulverizing mills. Hoppers and feeders are equipped with water spray systems, and a mixture of foam and binder is added at the crushers for dust suppression.

Once the coal has been crushed and passed through the sampling towers, it is delivered to the coal stackers via an interconnected electric conveyor and flop gate system. The coal stackers place the coal into one of 10 stacker piles. The coal is stacked in layers ........