Mining Intelligence and News
United States

San Miguel Mine

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Summary

Mine TypeOpen Pit
StatusActive
Commodities
  • Lignite
Mining Method
  • Dragline
  • Truck & Shovel / Loader
  • Surface miner
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Mine Life... Lock
SnapshotThe San Miguel Mine delivers millions of tons of lignite coal through a Wholesale Power Contract with South Texas Electric Cooperative (STEC).

In late December 2024, San Miguel Electric Cooperative, Inc. (SMECI), the owner of the San Miguel Mine was awarded over $1.4 billion by the United States Department of Agriculture (USDA) Rural Utilities Service (RUS) through the Empowering Rural America (New ERA) program. This initiative aims to support energy projects prioritizing greenhouse gas reductions.

SMECI plans to replace its lignite operations with a 400-megawatt (MW) solar generation facility with 200 MW of battery storage.

If SMECI can convert from lignite to solar, it will enter into a new Wholesale Power Contract with STEC to supply the output of the proposed solar and battery storage facility, which is expected to be operational by 2027.

Owners

SourceSource
CompanyInterestOwnership
San Miguel Electric Cooperative, Inc. 100 % Direct
The San Miguel Lignite Mine is owned by San Miguel Electric Cooperative, Inc.

Contractors

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Deposit type

  • Sedimentary

Summary:

The mine extracts lignite coal from the Jackson formation, seams A, B, C and D ranging in thickness from 1.0 to 4.5 feet with a combined average total lignite thickness of approximately 9 feet. The seams are separated by relatively thin partings which vary in thickness from 0.5 to 1.5 feet.

The deposit consists of four or more thin (generally < 1 m or 3.3 ft thick) lignite benches that are separated by claystone and mudstone partings. The partings are composed of altered volcanic air-fall ash that has been reworked by tidal or channel processes associated with a back-barrier depositional environment (Snedden and Kersey, 1981; Gowan, 1985; Ayers, 1986; Senkayi and others, 1987; and Warwick and others, 1996).

In the mine area, the Jackson strata dip to the southeast about 17 m/km (90 ft/mi) (Ayers, 1986). Gowan (1985) and Ayers (1986) suggest that the mud-dominated sediments the comprise the floor, partings, and roof of the San Miguel lignite deposit originated in lagoonal mires landward (west) of the sandstone-dominated barrier island complex. The lignite-bearing interval is laterally persistent along strike for more than 40 kilometers (25 mi) (Ayers, 1986, 1989; Tewalt and others 1983).

The San Miguel lignite interval consists of four (or more) thin (generally <1 m or 3.3 ft thick) lignite benches that are separated by claystone and mudstone partings. The upper bed is designated as the A bed and is underlain by the B, C, and D beds (Gowan, 1985). Tewalt and others (1983) referred to this interval as South Jackson seam no. 10. The rocks above the lignite beds are dominated by fine siltstone and claystone with occasional thin layers of gastropod and bivalve shells.

Kaiser (1982), Gowan (1985), and Ayers (1986, 1989) suggested that the rock partings within the San Miguel lignite deposit are composed of volcanic air-fall ash that has been reworked by possibly tidally influenced channel processes. Senkayi and others (1987) examined the partings in detail and found that most contained altered kaolinite and mixed detrital and volcanic quartz grains, thereby supporting the interpretation of a volcanic origin and subsequent detrital mixing of the sediment that forms these layers. These findings are consistent with the conclusions of Warwick and others (1996).

Mining Methods

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Heavy Mobile Equipment

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EV - Electric

Comminution

Crushers and Mills

Milling equipment has not been reported.

Processing

Summary:

Commodity Production

CommodityUnits2024202320222021202020192018201720162015
Lignite tons  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe3,003,7802,977,0993,070,7082,776,8582,574,464
All production numbers are expressed as ROM coal.

Operational metrics

Metrics20242023202220212020201920182017
Coal tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe3,003,780 tons2,977,099 tons3,070,708 tons

Production Costs

Commodity production costs have not been reported.

Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required May 23, 2025
....................... Subscription required ....................... Subscription required Subscription required May 16, 2025

Workforce

Total WorkforceYear
...... Subscription required 2024
...... Subscription required 2023
...... Subscription required 2022
...... Subscription required 2021
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...... Subscription required 2019
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...... Subscription required 2016
...... Subscription required 2015
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...... Subscription required 2012

Aerial view:

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