Overview
Stage | Production |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
- Truck & Shovel / Loader
- Dragline
|
Processing |
|
Mine Life | 2047 |
North Antelope Rochelle Mine (NARM) is the world’s largest coal mine with the cleanest coal in the United States. |
Source:
p. 349
Company | Interest | Ownership |
Peabody Energy, Inc.
|
100 %
|
Indirect
|
Peabody Powder River Mining, LLC
(operator)
|
100 %
|
Direct
|
Peabody Powder River Mining, LLC operates as a subsidiary of Peabody Energy Corp.
Summary:
The Wasatch Formation and local Quaternary age deposits comprise all of the overburden lithologies at the mine site. The Wasatch consists of alternating, lenticular deposits of sandstones, siltstones, claystones, coal, and carbonaceous shales. Coal has been mined exclusively from the Wyodak-Anderson (WA) Seam. The remaining coal is 50-87 ft thick and 180 to 460 ft deep within the leased area. The WA seam is in the uppermost section of the Paleocene Fort Union Formation. The coal is thickest on the northwest side of the lease. There are two main geologic features at NARM. The first is a monocline that exists in a northwest to southeast trend over the middle portion of the mine. The lower 12-14 feet of the WA seam splits off as a hanger seam (Lower Wyodak-Anderson, or LWA) and has a steeply dipping gradient after it splits. The LWA seam is not mined because of poor quality and an increasingly high strip ratio. The mineable WA coal thickness averages 80 feet in the west and 60 feet east of the monocline. The second geologic feature is a ribbon split occuring in the southwest portion of the lease and trending northwest to the southeast. The WA splits into two nearly equally thick (30-35 ft) mineable seams: WA1 (upper split) and WA2 (lower split). The midburden between the WA1 and WA2 increases to a maximum of 120 ft thick. Structurally, the WA2 seam remains relatively flat, whereas the WA1 rides up over the parting and has a dipping structure. In conclusion, several thin rider seams (1-4 feet in thickness) occur within the overburden. They are quite consistent throughout the eastern portions of the lease but become more sporadic west of the splitline. The rider seams are not mined due to poor quality. The WA in the northern half and the WA1/WA2 in the southwest are the only seams mined at NARM. There are no known faults within the controlled coal area.
NARM is on the eastern flank of a regional syncline. The bedding inclination is gentle with dips less than three degrees toward the west. Because of the undulating character of the coal beds, there can be localized dips toward the east. Many of the coal beds in the Fort Union and Wasatch formations have been oxidized and burned along their outcrops producing clinker (locally referred to as the scoria). The clinker is the baked or thermally altered shale and sandstone in the strata overlying the burned-out coal bed.
Mineralization and Deposit Type
The mined coal at NARM is high volatile sub-bituminous C as defined by ASTM coal rank. The coal seam has very low sulfur content and is marketable as thermal coal for power generation. The heating value of the coal seams ranges from 8400 to 9250 BTU per pound over the remaining project area and the heating content generally increases with increasing depth.
The area is categorized as having low geologic complexity based on the following factors:
- The Wyodak-Anderson (WA) seam is laterally continuous and can be correlated using geophysical logs across large distances with high confidence.
- The seam is generally flat-lying and gently dipping towards the west with minor undulations. The depth of cover to the WA seam is generally shallow from the outcrop along the east to a maximum of 450 ft and averaging 320 ft for the remainder of the reserve.
- There are no major geologic anomalies across the area except for two well-defined seam split areas: a ribbon split in the southwest and a monocline with a hanger seam toward the east.
- The WA seam is currently mined across most of Campbell County and the northern portion of Converse County.
- Local quality variations are small and regional quality trends have been established from a long mining history.
Mining Methods
- Truck & Shovel / Loader
- Dragline
Summary:
The relatively shallow and very thick coal seam at this deposit determines that the most efficient mining method is the surface striping method which utilizes a combination of processes, including truck and shovel, cast blasting and dozing, dragline, etc. As a result of the high volume of sales with a wide range of quality requirements, the mining operation consists of multiple open pits mainly in four mining areas: West, North, East, and NARM North.
Conventional and cast blasting methods are generally used to fracture and fragment overburden and coal. After the cast blast and before the dragline operation, the backhoes are utilized to remove the shot material in the highwall and scale the highwall back to competent material down to a dragline bench operating level. Dozers are used to push more blasted material into the previous pit where the coal has been removed and at the same time prepare the working bench for the dragline. The dragline typically mines cuts that are 220 feet wide and with a bench height of 140-220 feet. The dragline is typically positioned on the spoil side of the pit when removing this remaining overburden. This allows for much of the dragline's spoil material to be stacked further from the low wall crest to reduce the overall spoil bank slope angle (internal angle of friction) to approximately the natural angle of repose of the shot material and thus minimize the risk of spoil slope failures or loose material rolling into the pit area. Other equipment, including shovel and trucks, backhoe and trucks, front end loader and trucks or dozers, may be used to move the overburden above the coal instead of and/or in conjunction with the dragline system. The truck/shovel benches will generally be 55 feet high. Dragline deadheading setback is limited to a minimum of 20' from the crest of the low wall spoil bench. Dragline bench height and spoil bank angle are varied based on site-specific conditions.
Mining Process
The mine employs conventional truck/shovel methods, utilizing multiple P&H 4100 shovels and end-dump trucks, and dragline methods utilizing two Bucyrus-Erie 2570 draglines, a Marion 8200 dragline, and a Bucyrus-Erie 1570 dragline with cast/doze and truck/shovel prebenching operations to remove overburden material where necessary. The methods for controlling highwall and spoil bank stability described here are general and may be modified as conditions warrant. The methods shown may be modified based on localized geological conditions encountered.
Generally, Truck/shovel system is utilized to strip overburden down to a consistent cast bench height and then a cast blasting, dozer push and dragline stripping system is utilized to uncover the coal. Truck/shovel may assist with dragline system burden as necessity requires. There may also be times during the life of the mine that traditional truck/shovel overburden stripping may be utilized in pits that have an insufficient length for a dragline system.
In general, after the topsoil has been removed from the surface of the uppermost bench, the overburden is mined by dragline and/or truck/shovel fleets in a series of lifts, with the bench heights varying in relation to the total overburden thickness. Blasting is usually required to fragment the overburden.
Cast blasting will be employed in almost all pits to optimize cost and operational effectiveness. As overburden gets thicker and geologic, hydrologic, and geotechnical conditions warrant, cast blasting or a cast blasting/dozer push system is often employed to enhance the system’s efficiency. This mining method will result in a small coal wedge that is left partially un-recovered for spoil stability.
Overburden removal and backfilling is generally one continuous operation with spoil material being transported to mined-out areas in a series of stair-step lifts. The backfill area is shaped to conform to approved post-mining topography. Pre-mining and pre-topsoil replacement sampling programs ensure that backfill material is placed appropriately to meet sub-soil quality parameters. Top soiling typically occurs within a year of final backfilling. Revegetation begins in the first suitable season following topsoil replacement.
Coal will generally be mined in one bench in the North, East, and NARM North areas whereas two benches are presently used in the southern portion of the West mining area where there is a parting layer of varying thickness, located approximately midway in the coal seam, separating the coal into Upper (WA1) and Lower (WA2) coal benches/seams. Although this layer also exists in the northern portion of the West Pit, it is too thin to be significant, and operational constraints generally determine the height of the two coal benches. This major interburden waste layer (found primarily on leases WYW154001, WYW180753, WYW180754, and WYW176095) will be removed by either a truck/shovel fleet or a dragline though dozers, scrapers and frontend loaders may also be used. It should be noted, however, that two benches may also be used in any pit because of the presence of parting, equipment digging height constraints, and/or adverse conditions. The operation doesn’t have coal washing facility and the coal mining process cleans the coal top and bottom very thoroughly in order to control the product quality.
The North Antelope Rochelle Mine presently operates 24 hours per day.
Coal and overburden removal is performed 12 hours/shift, 2 shifts/day, 7 days/week (weather permitting).
Crusher / Mill Type | Model | Size | Power | Quantity |
Roll crusher
|
.......................
|
|
|
1
|
Roll crusher
|
.......................
|
|
|
8
|
Flow Sheet:
Summary:
The coal seam at NARM has very low inherent ash and it is extracted from the pits with minimum dilutions. The washing plant is not needed and all final products shipped to customers are ROM coal. The coal processing at NARM mainly includes sizing, conveyance, storage, and train loading.
Process Selection and Design
The processing plants at NARM include five sites with truck dumps and crushers. They were constructed through different periods of this operation. The most recent major upgrades include an in-pit truck dump, crusher and overland conveyor system along with a central blending/loading facility along the loadout loop. These were completely operational in 2008. The current processing plants have sufficient capacity to meet the requirements in the mine plan. There are no major additions or upgrades planned in the future other than routine maintenance or periodic relocation.
Coal Handling and Processing Plant
After the overburden has been removed ........

Production:
Commodity | Units | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Coal (thermal)
|
M tons
| ...... ^ | ......  | ......  | ......  | 98 | 102 | 93 |
Heat Content | BTU/lb | | | 8,800 | 8,800 | 8,800 | 8,800 | 8,800 |
All production numbers are expressed as ROM coal.
^ Guidance / Forecast.
- Subscription is required.
Operational Metrics:
Metrics | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Coal tonnes mined
| ......  | ......  | 85,340,711 tons | 98,315,794 tons | 101,595,323 tons | 92,863,811 tons |
- Subscription is required.
Reserves at December 31, 2021:
Category | Tonnage | Commodity |
Proven
|
1,378 M tons
|
Coal (thermal)
|
Probable
|
106 M tons
|
Coal (thermal)
|
Proven & Probable
|
1,484 M tons
|
Coal (thermal)
|
Corporate Filings & Presentations:
- Subscription is required.
Aerial view:
- Subscription is required.