U.S. Coal Resources and Reserves Assessment Project

Assessing U.S. Coal Resources and Reserves

The U.S. Coal Resources and Reserves Assessment Project, as part of the U.S. Geological Survey (USGS) Energy Resources 

Program, conducts systematic, geology-based, regional assessments of significant coal beds in major coal basins in the United 

States. These assessments detail the quantity, quality, location, and economic potential of the Nation’s remaining coal resources 

and reserves and provide objective scientific information that assists in the formulation of energy strategies, environmental 

policies, land-use management practices, and economic projections.

Introduction

The U.S. Energy Information Administration (EIA) projects 

that approximately 30 percent of the electricity used in the United 

States will be generated from coal over the next several years and 

that coal will continue to be a major fuel source for the generation 

of electricity into the foreseeable future (U.S. Energy Information 

Administration, 2017b). The coal resources and reserves of the 

Nation that will supply the continued demand occur in numerous 

coal beds and coal zones, of varying thickness, rank, areal extent, 

and quality in coal fields and basins throughout the United States 

(fig. 1). To determine if the Nation’s coal resources and reserves 

are sufficient to meet the projected future demands, periodic 

objective and scientific assessments of these coal resources and 

reserves are required.

Coal fields of the conterminous United States—National Coal Resource Assessment updated version

Williston

Basin

Piceance

Basin

Raton

Basin

Illinois

Basin

Appalachian

Basin

(northern)

GULF

COAST

PROVINCE EASTERN

PROVINCE

PACIFIC

COAST

PROVINCE

NORTHERN

GREAT

PLAINS

PROVINCE

INTERIOR

PROVINCE

ROCKY

MOUNTAIN

PROVINCE

0 250 500 KILOMETERS

0 250 500 MILES

EXPLANATION

Predominant coal rank

Anthracite

Low-volatile bituminous

Medium- and high-

 volatile bituminous

Unassessed Triassic coal basins

Coal province boundary

Proposed future assessment area

 (generalized)

Minimal or no coal present

Unknown coal potential

Coal present

Subbituminous

Lignite

DENVER

REGION

WESTERN

REGION

PENNSYLVANIA

ANTHRACITE

REGION

ATLANTIC

COAST

REGION

TEXAS

REGION

MISSISSIPPI

REGION

SOUTHWESTERN

UTAH

REGION

FORT UNION

REGION

EASTERN

REGION

APPALACHIAN

REGION

GREEN

RIVER

REGION

SAN JUAN

RIVER

REGION

BIGHORN

BASIN

REGION

POWDER

RIVER

REGION

UINTA

REGION

WIND

RIVER

REGION

DENVER

REGION

WESTERN

REGION

PENNSYLVANIA

ANTHRACITE

REGION

ATLANTIC

COAST

REGION

TEXAS

REGION

MISSISSIPPI

REGION

SOUTHWESTERN

UTAH

REGION

FORT UNION

REGION

EASTERN

REGION

APPALACHIAN

REGION

GREEN

RIVER

REGION

SAN JUAN

RIVER

REGION

BIGHORN

BASIN

REGION

POWDER

RIVER

REGION

UINTA

REGION

WIND

RIVER

REGION

Figure 1. Coal fields of the conterminous United States from the National Coal Resource Assessment updated version (modified from East, 2013).

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2017–3067

September 2017
Resources Versus Reserves

The United States is richly endowed with coal 

resources, although only a small percentage of these coal 

resources can be defined as reserves. The terms “resources” 

and “reserves” are often used interchangeably, but there 

are major differences in their definitions. The terms, 

modified from USGS Circular 891 (Wood and others, 1983, 

p. 18–19), are defined as follows:

• Coal resources are naturally occurring deposits of coal in 

the Earth’s crust in such amounts that economic extraction 

is currently or potentially feasible.

• Coal reserves are the portion of the recoverable coal 

resources that can be extracted economically at the time 

of classification, even if the facilities for extraction are 

not in place or operative at the time of classification.

Coal resources can be classified into categories that 

are progressively refined; this categorization reduces coal 

quantities using criteria such as previous mining, geologic 

conditions, environmental restrictions, and miningtechnology limitations. As these criteria are applied, the 

quantity of coal resources available in each category is 

reduced. An explanation of the categories and the criteria 

affecting coal quantity losses that the USGS calculates are 

shown in figure 2.

The portion of recoverable coal resources that can be 

defined as reserves by the USGS will vary over time on 

the basis of fluctuations in mining costs and the market 

value of the coal. In order to be classified as economically 

extractable, the current market value of the extracted coal 

must be greater than the cost to extract it. The projected 

costs of extraction are calculated by compiling economicmodel designs based on regional mining practices and 

prefeasibility cost projections.

As an example, the projected tonnage values for each 

coal resources category and the total reserves that the 

USGS calculated for the Powder River Basin (Luppens and others, 

2015) are shown in table 1. Note that the reserves are only a small 

percentage of the original coal resources. Estimating the recoverable 

coal resources and reserves provides a more accurate and relevant 

assessment of the U.S. coal resources that are realistically available 

for extraction into the foreseeable future using current technology.

Table 1. Powder River Basin (Wyoming and Montana) coal resources and reserves showing the percent of each classification as 

compared to the original resources (tonnage values from Luppens and others, 2015).

Powder River Basin Coal Resources and Reserves

Assessment

classification Factors

Tons

(billions of

short tons)

Percent of

original

resources

Original resources 1,156 100%

SUBTRACT Previously mined or sterilized; Weathering or burn along outcrops

Remaining resources 1,148 99%

SUBTRACT Geological constraints; Environmental, societal, technological restrictions

Available resources 179 15%

SUBTRACT Too deep; Too thin; High stripping ratios; Mining technology limitations

Recoverable resources 162 14%

SUBTRACT Cost to extract is greater than market value of coal

Reserves 25 2%

All in-place coal resources prior to mining activities

ORIGINAL COAL RESOURCES 

SUBTRACT coal resources that have been previously extracted, sterilized by previous

mining activities, or lost because of weathering or burn along outcrops. 

REMAINING COAL RESOURCES

SUBTRACT coal resources lost due to geological constraints and environmental,

societal, and technological restrictions. 

AVAILABLE COAL RESOURCES

SUBTRACT coal resources not extractable because of excessive depths of cover, high stripping

ratios, or mining technology limitations. 

RECOVERABLE COAL RESOURCES

SUBTRACT coal resources where cost to extract is greater than market value of coal (will vary

because of demand and technology). 

RESERVES

Figure 2. Flow chart for the classification of coal resources and reserves 

(modified from Luppens and others, 2009).
Objective and Scope

The objective of the U.S. Coal 

Resources and Reserves Assessment 

Project is to conduct systematic, geologybased, regional assessments of the 

Nation’s remaining coal resources, as 

well as recoverable coal resources and 

reserves for individual, significant coal 

beds in major coal provinces and regions. 

“Significant coal beds” are defined as 

laterally extensive and of sufficient 

thickness to warrant assessment as coal 

resources and (or) reserves.

The current coal assessment project 

differs from previous generations of USGS 

coal assessments in that

• Current assessments report tonnages 

for all coal resources classifications, as 

well as for reserves, whereas previous 

assessments only reported total coal 

resources or remaining coal resources;

• Current assessments of coal resources 

and reserves are conducted for basins 

or coal fields within basins, whereas 

previous assessment areas ranged in 

size from geographic regions or coal 

provinces down to USGS 7.5-minute 

quadrangle scale; and

• Current assessments focus on individual, 

significant coal beds, whereas some previous assessments focused on composite 

intervals or zones containing multiple 

coal beds.

The current objective of the project is 

to assess coal resources and reserves in the 

Northern Great Plains and Rocky Mountain 

Coal Provinces (fig. 1), with an emphasis 

on coal underlying Federal lands. The first 

coal basin evaluated, using the individual, 

significant coal bed methodology, was 

the Powder River Basin in Wyoming and 

Montana (Luppens and others, 2015).

The Greater Green River Basin in 

Wyoming and Colorado is the second basin 

under assessment (fig. 3). The assessment is 

focused in three separate areas: 

1. Little Snake River coal field and Red 

Desert (south-central Wyoming)

2. Yampa coal field (northwestern 

Colorado)

3. Rock Springs uplift (southwest 

Wyoming)

The Greater Green River Basin was prioritized for assessment because it contains vast 

tracts of Federal lands and large areas of the basin have not been formally assessed by the 

USGS for coal resources and reserves. For example, in the Little Snake River coal field and 

Red Desert assessment area, approximately 58 percent of the surface land is owned by the 

Federal Government (U.S. Geological Survey, 2000).

Additionally, much of the drill hole data that is being used in the geologic modeling 

and economic evaluations in the Greater Green River Basin was acquired by the USGS 

within the last 5 years and provides an increased data density within the assessment areas.

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DEN017_0084_fig_03.ai

LINCOLN

UINTA

SUMMIT

DUCHESNE

CARBON

UINTAH

EMERY GRAND

MOFFAT

RIO BLANCO

GARFIELD

MESA

DELTA GUNNISON

PITKIN

LAKE

EAGLE

GRAND

ROUTT

JACKSON

DAGGETT

SWEETWATER

CARBON

FREMONT

HOT SPRINGS WASHAKIE JOHNSON

NATRONA

TETON

SUBLETTE

YAMPA COAL FIELD

ASSESSMENT AREA

LITTLE SNAKE RIVER

COAL FIELD AND

RED DESERT

ASSESSMENT AREA

GREATER GREEN

RIVER BASIN

WYOMING

IDAHO

WYOMING

Base from U. S. Geological Survey digital data, 1:2,000,000, 2017

Albers Equal-Area Conic projection

Standard parallels 29°30'N. and 45°30'N.

Central meridian –109°W.

North American Datum of 1983 

UTAH

COLORADO

ROCK SPRINGS

UPLIFT

ASSESSMENT

AREA

111° 110° 109° 108° 107° 106°

39°

40°

41°

42°

43°

70

70

80

25

80

0 25 50 75 KILOMETERS

0 25 50 75 MILES

Figure 3. U.S. Coal Resources and Reserves Assessment Project current assessment 

studies in the Greater Green River Basin, Wyoming and Colorado. Outline of Greater 

Green River Basin from U.S. Geological Survey Southwestern Wyoming Province 

Assessment Team (2005).
Areas under consideration for future assessments include the 

Raton and Piceance Basins in the Rocky Mountain Province and 

the Williston Basin in the Northern Great Plains Province (fig. 1). 

Also under consideration for assessment are the Illinois Basin, the 

northern Appalachian Basin, and the Gulf Coast Province. These 

areas warrant consideration for assessment because they will continue to provide substantial amounts of the coal produced in the 

United States in the foreseeable future (U.S. Energy Information 

Administration, 2017a).

Methodologies

The systematic determination of recoverable coal resources 

and reserves conducted by the U.S. Coal Resources and Reserves 

Assessment Project uses a peer-reviewed methodology based on 

established USGS practices (Rohrbacher and others, 2005). The 

assessment methodology can be divided into three distinct phases:

• Phase 1—Data collection: Geologic, coal quality, restrictions, 

and economic data are collected and organized.

• Phase 2—Data modeling: Significant coal beds are correlated 

and modeled.

• Phase 3—Calculations: Geologic and economic models are 

evaluated and resources and reserves are calculated.

The USGS works cooperatively with Federal and State 

agencies, including State geological surveys and the Bureau of 

Land Management in data sharing, correlations, and geologic 

interpretations.

Results

The results of the coal assessments provide essential 

information on the quantity, quality, and availability of coal 

resources and reserves remaining in the United States. This 

information is used in academia and industry and by a variety of 

Federal and State agencies and contributes to the formulation of 

energy strategies, environmental policies, land-use management 

practices, and economic projections.

Selected U.S. Coal Resources and Reserves 

Assessment Project Publications

• Preliminary Geologic Mapping of Cretaceous and Tertiary 

Formations in the Eastern Part of the Little Snake River Coal 

Field, Carbon County, Wyoming (Haacke and others, 2016)

• Coal Geology and Assessment of Coal Resources and 

Reserves in the Powder River Basin, Wyoming and Montana 

(Luppens and others, 2015)

• Geospatial Data for Coal Beds in the Powder River Basin, 

Wyoming and Montana (Kinney and others, 2015)

• Drill Hole Data for Coal Beds in the Powder River Basin, 

Montana and Wyoming (Haacke and Scott, 2013)

• Assessment of Coal Geology, Resources, and Reserve Base 

in the Powder River Basin, Wyoming and Montana (Scott and 

Luppens, 2013)

• Assessment of Coal Geology, Resources, and Reserves in the 

Montana Powder River Basin (Haacke and others, 2013)

• A Critical Review of Published Coal Quality Data from the 

Southwestern Part of the Powder River Basin, Wyoming 

(Luppens, 2011)

• Assessment of Coal Geology, Resources, and Reserves in the 

Southwestern Powder River Basin, Wyoming (Osmonson and 

others, 2011)

• Assessment of Coal Geology, Resources, and Reserves in the 

Northern Wyoming Powder River Basin (Scott and others, 

2011)

• Assessment of Coal Geology, Resources, and Reserves in the 

Gillette Coalfield, Powder River Basin, Wyoming (Luppens 

and others, 2012)

Panoramic view of surface mine operation in the Powder River Basin, Wyoming. (Photo by David C. Scott)
References Cited

East, J.A., 2013, Coal fields of the conterminous United States—

National Coal Resource Assessment updated version: U.S. 

Geological Survey Open-File Report 2012–1205, one sheet, 

scale 1:5,000,000. [Also available at https://pubs.usgs.gov/

of/2012/1205.]

Haacke, J.E., Barclay, C.S.V., and Hettinger, R.D., 2016, 

Preliminary geologic mapping of Cretaceous and Tertiary 

formations in the eastern part of the Little Snake River coal 

field, Carbon County, Wyoming: U.S. Geological Survey 

Open-File Report 2016–1170, 9 p., accessed February 27, 

2017, at https://doi.org/10.3133/ofr20161170.

Haacke, J.E., and Scott, D.C., 2013, Drill hole data for coal 

beds in the Powder River Basin, Montana and Wyoming: 

U.S. Geological Survey Data Series 713, 15 p., accessed 

February 27, 2017, at https://pubs.usgs.gov/ds/713.

Haacke, J.E., Scott, D.C., Osmonson, L.M., Luppens, J.A., 

Pierce, P.E., and Gunderson, J.A., 2013, Assessment of coal 

geology, resources, and reserves in the Montana Powder River 

Basin: U.S. Geological Survey Open-File Report 2012–1113, 

133 p., accessed February 27, 2017, at https://pubs.usgs.gov/

of/2012/1113/.

Kinney, S.A., Scott, D.C., Osmonson, L.M., and Luppens, 

J.A., 2015, Geospatial data for coal beds in the Powder 

River Basin, Wyoming and Montana: U.S. Geological 

Survey Data Series 912, 7 p., accessed February 27, 2017, at 

https://doi.org/10.3133/ds912.

Luppens, J.A., 2011, A critical review of published coal 

quality data from the southwestern part of the Powder River 

Basin, Wyoming: U.S. Geological Survey Open-File Report 

2011–1148, 23 p. [Also available at https://pubs.usgs.gov/

of/2011/1148/.]

Luppens, J.A., Rohrbacher, T.J., Osmonson, L.M., and Carter, 

M.D., 2009, Coal resource availability, recoverability, and 

economic evaluations in the United States—A summary, 

chap. D of Pierce, B.S., and Dennen, K.O., eds., The national 

coal resource assessment overview: U.S. Geological Survey 

Professional Paper 1625–F, 17 p.

Luppens, J.A., Scott, D.C., Haacke, J.E, Osmonson, L.M., and 

Pierce, P.E., 2015, Coal geology and assessment of coal 

resources and reserves in the Powder River Basin, Wyoming 

and Montana: U.S. Geological Survey Professional Paper 1809, 

218 p. [Also available at https://doi.org/10.3133/pp1809.]

Luppens, J.A., Scott, D.C., Haacke, J.E., Osmonson, L.M., 

Rohrbacher, T.J., and Ellis, M.S., 2012, Assessment of coal 

geology, resources, and reserves in the Gillette Coalfield, 

Powder River Basin, Wyoming (revised February 2, 2012): 

U.S. Geological Survey Open-File Report 2008–1202, 127 p. 

[Also available at https://pubs.usgs.gov/of/2008/1202/.]

Osmonson, L.M., Scott, D.C., Haacke, J.E., Luppens, J.A., and 

Pierce, P.E., 2011, Assessment of coal geology, resources, and 

reserves in the southwestern Powder River Basin, Wyoming: 

U.S. Geological Survey Open-File Report 2011–1134, 

135 p., accessed February 27, 2017, at https://pubs.usgs.gov/

of/2011/1134/.

Loading coal at the Trapper Mine, northwest Colorado. (Photo by David C. Scott)
Rohrbacher, T.J., Luppens, J.A., Osmonson, L.M., Scott, D.C., 

and Freeman, P.A., 2005, An external peer review of the U.S. 

Geological Survey Energy Resource Program’s economically 

recoverable coal resource assessment methodology—

Report and comments: U.S. Geological Survey Open-File 

Report 2005–1076, CD–ROM, 21 p. [Also available at 

https://pubs.er.usgs.gov/publication/ofr20051076/.] 

Scott, D.C., Haacke, J.E., Osmonson, L.M., Luppens, J.A., 

Pierce, P.E., and Rohrbacher, T.J., 2011, Assessment of 

coal geology, resources, and reserves in the northern 

Wyoming Powder River Basin: U.S. Geological Survey 

Open-File Report 2010–1294, 136 p. [Also available at 

https://pubs.er.usgs.gov/publication/ofr20101294/.] 

Scott, D.C., and Luppens, J.A., 2013, Assessment of coal 

geology, resources, and reserve base in the Powder River 

Basin, Wyoming and Montana: U.S. Geological Survey 

Fact Sheet 2012–3143, 6 p., accessed February 27, 2017, at 

https://pubs.usgs.gov/fs/2012/3143/.

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energy outlook 2017: U.S. Energy Information Administration, #AEO2017, 127 p., accessed February 27, 2017, at 

https://www.eia.gov/outlooks/aeo/pdf/0383(2017).pdf.

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energy outlook, release date February 7, 2017: U.S. Energy 

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https://www.eia.gov/outlooks/steo/.

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United States: U.S. Geological Survey metadata file, accessed 

February 27, 2017, at https://nationalmap.gov/small_scale/

atlasftp.html.

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Assessment Team, 2005, Petroleum systems and geologic 

assessment of oil and gas in the Southwestern Wyoming 

Province, Wyoming, Colorado, and Utah: U.S. Geological 

Survey Digital Data Series DDS–69–D, CD–ROM.

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W.C., 1983, Coal resource classification system of the U.S. 

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[Also available at https://pubs.er.usgs.gov/publication/cir891/.]

For More Information

Coal assessment results also are available at the USGS 

Energy Resources Program website at https://energy.usgs.gov/.

U.S. Coal Resources and Reserves Assessment 

Project Team

Brian N. Shaffer, Jon E. Haacke, David C. Scott, 

Paul E. Pierce, Scott A. Kinney, Ricardo A. Olea, 

James A. Luppens

Contact Information

Contact information for the U.S. Coal Resources and 

Reserves Assessment Project is available at the USGS Energy 

Resources Program website at https://energy.usgs.gov/.

A train loaded with coal leaves the Powder River Basin, Wyoming. 

(Photo by David C. Scott)

ISSN 2327-6916 (print)

ISSN 2327-6932 (online) https://doi.org/10.3133/fs20173067