Overview
Stage | Production |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
- Truck & Shovel / Loader
- Dragline
|
Production Start | ...  |
Mine Life | 2045 |
The largest lignite mine in the United States. |
Source:
p. 10
Company | Interest | Ownership |
NACCO Industries Inc.
|
100 %
|
Indirect
|
Coteau Properties Company
(operator)
|
100 %
|
Direct
|
The Coteau Properties Company (Coteau), a subsidiary of The North American Coal Corporation (NACoal) is the owner and operator of the Freedom Mine, an active lignite surface mining operation in production status. NACoal is a wholly-owned subsidiary of NACCO.
Contractors
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Deposit Type
- Unconformity related
- Sedimentary
Summary:
The Freedom Mine is located within the glaciated subsection of the Missouri Plateau, part of the Great Plains Province. The formations of sedimentary origin were deposited in the Williston Basin, the dominant structural feature of western North Dakota. The center of this essentially symmetrical basin is located near the town of Williston, North Dakota, approximately 100 miles northwest of the mine site. The basin consists of approximately 15,000 feet of sedimentary rock overlying a basement complex of gneisses, schists, and granites. This sequence records a geologic time interval spanning late Precambrian (1 to 2 billion years ago) to Holocene (last 10,000 years). The structural influence of the Williston Basin is reflected in the dip of the formations underlying the Freedom Mine area. Drill hole data indicates that the Sentinel Butte Formation, the uppermost bedrock unit of the sedimentary series within the Freedom Mine area, dips westward toward the center of the Williston Basin at 50 to 75 feet per mile (about ½ to 1 degree). The dip of the bedrock strata increases with depth due to the physical characteristics of the Williston Basin. The subsidence of the Williston Basin began early in the Paleozoic Era (425 to 542 million years ago). Subsidence has not been continuous, nor has sedimentation occurred at a constant rate. These irregularities are evidenced by the presence of several unconformities in the stratigraphic column of North Dakota.
The most prolific lig ........

Mining Methods
- Truck & Shovel / Loader
- Dragline
Summary:
The lignite at the Freedom Mine surface mining operation is recovered using dragline and conventional truck and shovel mining methods due to the proximity of the lignite to the surface and the physical characteristics of the deposit. Mining operations includes; suitable plant growth material (SPGM) removal, replacement and storage, overburden removal, lignite production, and spoil backfill and grading. In the development phase, drainage and water control were established, and then the required infrastructure consisting of power, mine office and maintenance facilities, lignite stockpile facilities, and roadways were established.
The Freedom Mine is designed to supply approximately 14 to 16 million tons of lignite per year but generally produces between 12.5 million and 13.5 million tons of lignite coal annually.
TYPE AND GENERAL MINING METHOD
The Freedom Mine is a surface mining operation, which currently encompasses approximately 45,000 acres within the permitted areas. The mineable coal seam is known as the Beulah-Zap bed, ranging from 15 to 22 feet thick, with a weighted average thickness of approximately 18 feet throughout the permit area. The overburden directly above the Beulah-Zap bed ranges in thickness from 25 feet along the cropline, to more than 250 feet in the larger strip ratio areas.
Coteau utilizes standard surface mining techniques to extract coal from the proposed permit area. Mining operations will typically occur in a s ........

Summary:
Mineral processing does not occur at the Freedom Mine.
Production:
Commodity | Units | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Coal (thermal)
|
tons
| ......  | ......  | ......  | 14,183,313 | 14,716,777 | 14,109,960 |
Heat Content | BTU/lb | | 6,700 | 6,700 | 6,700 | 6,700 | 6,700 |
Sulfur | % | | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 |
All production numbers are expressed as ROM coal.
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Operational Metrics:
Metrics | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Coal tonnes mined
| ......  | ......  | 13.5 M tons | 14.2 M tons | 14.7 M tons | 14.1 M tons |
Raw coal annual capacity
| ......  | ......  | | | | |
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Reserves at December 31, 2021:
Mineral Resources classification distances from point of measurement for each class are as follows: Measured – less than 660 feet, Indicated - from 660 feet to 1,320 feet, and Inferred - greater than 1,320 feet. A cut-off grade of $1.70/mmBTU has been applied to the Mineral Resource Estimation.
A cut-off grade of $1.55/mmBTU has been applied to the Measured and Indicated Resources to upgrade these resources into Proven and Probable Reserves.
Category | Tonnage | Commodity |
Proven
|
253,946,500 tons
|
Coal (thermal)
|
Probable
|
3,552,300 tons
|
Coal (thermal)
|
Proven & Probable
|
257,498,800 tons
|
Coal (thermal)
|
Measured
|
322,310,200 tons
|
Coal (thermal)
|
Indicated
|
8,188,400 tons
|
Coal (thermal)
|
Measured & Indicated
|
330,498,600 tons
|
Coal (thermal)
|
Inferred
|
15,000 tons
|
Coal (thermal)
|
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