Chapter PAR

COAL AVAILABILITY AND RECOVERABILITY STUDIES

IN THE POWDER RIVER BASIN,

WYOMING AND MONTANA

By Carol L. Molnia,1 Lee M. Osmonson,

1

Edith M. Wilde,

2

 Laura R.H. Biewick,

1

Timothy J. Rohrbacher,

1

 and M. Devereux Carter

1

in U.S. Geological Survey Professional Paper 1625-A

 

1

 U.S. Geological Survey

2

 Montana Bureau of Mines and Geology, Butte, Montana
PAR-ii

Contents

Part 1. Definitions and concepts ..................................................................... PAR-1

Part 2. Powder River Basin study areas.......................................................... PAR-9

Part 3. U.S. Geological Survey study of coal availability

in the Hilight quadrangle, Wyoming.............................................. PAR-12

Part 4. U.S. Bureau of Mines study of coal availability and recoverability

in the Hilight quadrangle ............................................................... PAR-27

Part 5. Coal availability in the Willow Crossing 7.5’ quadrangle,

Montana.......................................................................................... PAR-41

Part 6. The Middle Pod study area, Gillette Coalfield, Wyoming................ PAR-54

Part 7. Results and conclusions..................................................................... PAR-63

References cited............................................................................................. PAR-72

Appendices..................................................................................................... PAR-75

1. Appendix PAR-1. Summary text for Part 3. ............................ PAR-77

2. Appendix PAR-2. Summary text for Part 5. ............................ PAR-92

Figures

PAR-1. Powder River Basin study areas for coal availability and recoverability.

PAR-2. Mining restrictions in the Hilight quadrangle, Wyoming.

PAR-3. Mining restrictions in the Willow Crossing quadrangle, Montana.

PAR-4. Additional factors affecting mining in the Willow Creek quadrangle.
PAR-iii

Table

PAR-1. Differences between two studies of the Hilight quadrangle
in the Powder in the Powder River Basin,

Wyoming and Montana yoming and Montana

by

Carol L. Molnia, Lee M. ol L. Molnia, Lee M. Osmonson Osmonson,

Edith M. Edith M. Wilde, Laura R.H. , Laura R.H. Biewick Biewick,

Timothy J. imothy J. Rohrbacher Rohrbacher,

and M. Devereux Carter

"Determining the amount of coal that

can be mined under current

environmental, societal, technologic,

and economic conditions"

Coal Availability and Recoverability Studies vailability and Recoverability Studies

 PAR-iv
Part 1. Definitions

and concepts

 PAR-1
COAL AVAILABILITY STUDIES

 ORIGINAL COAL

- minus -

 AREAS ALREADY MINED

- minus -

LAND-USE RESTRICTIONS

- minus -

TECHNOLOGIC CONSIDERATIONS

- equals -

AVAILABLE COAL

 PAR-2
The quantity of coal resources within the United States has been debated for

many years. Past figures were based on gross estimates of coal in the ground

and did not address the amount that might realistically be available for

production after environmental and technological constraints were considered.

Regulatory and land-use restrictions, the presence of towns and other cultural

resources, current mining technology, geologic conditions, coal quality, and

other factors significantly reduce the amount of coal actually available for

mining.

Since 1986, the U.S. Geological Survey (USGS), in cooperation with State

geological surveys, has been producing estimates of available coal in coal

production areas of the country by identifying constraints on potentially

minable coal resources. The results of these availability studies make it

possible for Federal and State agencies, utilities, social planners, and energy

consumers and producers to make informed decisions regarding energy use

and policies.

Coal availability

 PAR-3
COAL RECOVERABILITY STUDIES

COAL AVAILABLE FOR MINING

- minus -

MINING LOSSES

- minus -

WASHING LOSSES

- equals -

RECOVERABLE RESOURCES

- minus -

MINABLE RESOURCES TOO COSTLY TO EXTRACT

- equals -

ECONOMICALLY RECOVERABLE RESOURCE

(Reserve)

 PAR-4
In coal recoverability studies, the available coal resource estimates are analyzed

to determine that part which is economically recoverable. Coal recoverability

addresses the many technological, economic, and environmental restrictions

that affect the profitable extraction of coal. Mining production costs, current

mining machinery and methods, present and near-future market conditions,

and the impact of the Clean Air Act regulations all determine what coal

resources can be profitably developed.

The ultimate objectives of coal recoverability are to contribute background

data for local, State, and Federal energy policy decisions and to assist

governmental entities in determining the socio-economic effects on coal-mining

areas within their jurisdictions as the profitable coal resources become

depleted.

Coal recoverability studies began as a cooperative effort with the U.S. Bureau

of Mines in 1989. Now the program is conducted solely within the USGS as an

important adjunct to coal availability studies.

Coal recoverability

 PAR-5
• Recoverable Resource—That part of the

available coal that is left after normal mining and

cleaning losses are subtracted. Costs involved with the

extraction and cleaning of the coal are not considered,

nor is the potential selling price of the coal.

• Economically Recoverable Resource—That

part of the recoverable coal that can be mined, cleaned,

and marketed at a profit (depends on the mine location,

the characteristics of the coal bed, the quality of the coal,

and the mining methods used). Also known as a reserve.

Coal recoverability terms

 PAR-6
Helpful concepts

• Both the U.S. Geological Survey and the U.S. Bureau of

Mines (USBM) separately studied coal availability in the

Hilight quadrangle (see Part 3 and Part 4) as part of a

cooperative effort to develop availability methodology for

the western United States. The two agencies used different

techniques and assumptions, and thus their results are not

directly comparable.

• The USBM, however, added to its availability study a coal

recoverability calculation (see Part 4) that built on the

same techniques and assumptions used in the USBM

availability study. Thus the two parts of the USBM study

can be legitimately compared and contrasted.

 PAR-7
Helpful concepts, continued

• Restrictions to mining vary with location and local

land-management regulations. Thus, different study

areas can have different mining restrictions and

availability considerations.

• This report reflects reasonable assumptions concerning

restrictions to mining based on local practices in the

Powder River Basin, Wyoming and Montana. A more

detailed determination of restrictions and other

availability considerations would occur during the

leasing and mine-planning phases of property

development.

• All tonnage figures are in short tons.

 PAR-8
Part 2. Powder River

Basin study areas

Availability and recoverability areas in Wyoming and Montana

 PAR-9
 Factors in selecting study areas (fig. PAR-1)

• Presence of Coal Resource

• Mining Activity—Past and Current

• Geologic and Cultural Characteristics

• Resource Management Issues

• Data Accessibility

 PAR-10
100 0 Miles 100

Bu l l Mts.

N

WYOMING

Willow Crossing

Otter

Colstrip E

Colstrip SW

Hilight

MONTANA

Powder

River

Basin

Powder River Basin 

Half Moon Hill

Middle Pod area

complete

complete

Study in progress

Coal-bearing rocks

Cretaceous

Tertiary

Major Railroads

 Availability study

Availability and 

recoverability 

studies

 

Figure PAR-1. Powder River Basin study areas for coal availability and recoverability. 

All areas shown are 7.5-minute quadrangles except the Middle Pod area. 

 PAR-11
Part 3. U.S. Geological

Survey study of

coal availability in the

Hilight quadrangle,

Wyoming

Determining the amount of coal that can be developed

 • Click here to read Summary text in Appendix PAR-1

 PAR-12
COAL AVAILABILITY STUDIES

 ORIGINAL COAL

- minus -

 AREAS ALREADY MINED

- minus -

LAND-USE RESTRICTIONS

- minus -

TECHNOLOGIC CONSIDERATIONS

- equals -

AVAILABLE COAL

 PAR-13
Helpful concepts

• Both the U.S. Geological Survey and the U.S. Bureau of

Mines (USBM) separately studied coal availability in the

Hilight quadrangle (see Part 3 and Part 4) as part of a

cooperative effort to develop availability methodology for

the western United States. The two agencies used different

techniques and assumptions, and thus their results are not

directly comparable (table PAR-1).

• The USBM, however, added to its availability study a coal

recoverability calculation that built on the same techniques

and assumptions used in the USBM availability study.

Thus the two parts of the USBM study can be legitimately

compared and contrasted (table PAR-1).

 PAR-14
Helpful concepts, continued

• Restrictions to mining vary with location and local

land-management regulations. Thus, different study

areas can have different restrictions and availability

considerations.

• This report reflects reasonable assumptions concerning

restrictions to mining based on local practices in the

Powder River Basin, Wyoming and Montana. A more

detailed determination of restrictions and other

availability considerations would occur during the

leasing and mine-planning phases of property

development.

• All tonnage figures are in short tons.

 PAR-15
Table PAR-1. Differences between the

two studies of the Hilight quadrangle

 USGS availability study

•Original resources: 4.4 billion tons

• Percent of original available: 60

•Modeled 5 coal beds

•Power line and cemetery included

as restrictions to mining

•Entire area of Hilight oil and gas

field considered unavailable for

mining

USBM availability and

 recoverability study

• Original resources: 3.6 billion tons

• Percent of original available : 95

• Percent of original recoverable: 89

• Percent economically recoverable: 11

• Modeled 2 coal-bed mining intervals

• Power line and cemetery not included

as restrictions to mining

• Only areas around individual oil and

gas wells considered unavailable for

mining

 PAR-16
Hilight quadrangle

Bighorn

Mountains

WYOMING

RIVER

POWDER

BASIN

MONTANA

USGS study of coal availability in the Hilight quadrangle*, 

Powder River Basin, Wyoming

As a complement to the regional

scope of the National Coal 

Assessment, the USGS has completed

a coal availability study of a selected

portion of the Powder River Basin,

the Hilight 7.5-minute quadrangle,

to determine the amount of available coal. 

Available coal is that quantity of the

total coal resource that is accessible

for mine development under current

regulatory, land-use, and 

technologic considerations. 

* See U.S. Geological Survey Open-File Report 97-469

 (Molnia and others, 1997) for the complete report

 on the Hilight availability study.

 PAR-17
CAMPBELL

COUNTY

CONVERSE

COUNTY

R 73 W

R 69 W

T 52N

T40 N

Buckskin

Rawhide

Dry Fork

Caballo

Coal Creek

Black Thunder

North Rochelle

Rochelle 

Antelope

Cordero

Eagle Butte

Fort Uni Wyodak

North Antelope 

Rocky Butte

Belle Ayr

Caballo

Rojo

Gillette

Hilight quadrangle

Our study determined that 

approximately 60 percent, or

2.7 billion tons of coal in the 

quadrangle, is available 

for development. 

Coal development considerations

in the quadrangle include dwellings,

railroads, pipelines, power lines,

wildlife habitat, alluvial valley

 floors, a cemetery, and the 

Hilight oil and gas field and

 gas plant. 

The Hilight quadrangle was

chosen because of its location

between two producing coal mines,

the interest in developing coal in

the Hilight area, and the issues 

that exist in multiple-use

management of the land. This 

quadrangle has also been studied 

for coal recoverability (see next 

chapter).	 Surface coal mines near

the Hilight quadrangle

Jacobs Ranch

on

105°30'W

44°30' N

44° N

43°30' N

105°30'W

0 6 Miles

 PAR-18
550

80 1153

250

SYSTEM

SERIES

FORMATION

COAL BEDNAME

?

TERTIARY

PALEOCENE EOCENE

WASATCH FORT UNION 

WYODAK Lower Main Rider

Wildcat

Moyer

Oedekoven

LITHOLOGY

THICKNESS  (FEET)

Generalized composite

stratigraphic section

for the

Hilight quadrangle 

Non-coal rock:

siltstone, mudstone,

claystone, shale,

and sandstone

Coal 

 PAR-19
0

Restrictions to mining

Power line

 Railroad

 Producing 

 oil and gas field

Producing 

oil and gas well

 

Area underlain by

Wyodak coal bed

105° 22'30"W

 

43°45'N

 Coal

Outcrop

1 Mile

Gas plant

Cemetery

105°15'W

43°52'30"N

Figure PAR-2. Restrictions to mining. These areas are not available

for surface mining because of land-use and technologic constraints.

 PAR-20
 Inactive oil and gas well

 Oil and gas pipeline

0 1 Mile

 Area underlain by

Wyodak coal bed

105° 22'30"W 105°15'W

 Coal

Outcrop

Alluvial valley floor

Dwellings

 Raptor sites (including

 golden eagles)

43°45'N

 43°52'30"N

Additional mining considerations. Most likely, coal under these 

areas would be available for mining, but with certain mitigations and

stipulations which might add to the complexity and cost of the mining

operation. 

Considerations to mitigate

 PAR-21
 Available:

2.7 billion tons 

60% of original

 Unavailable:

 1.7 billion tons

 40% of original

Coal availability in the Hilight quadrangle 

Total original resources of 4.4 billion tons

This USGS study shows that approximately 60 percent

(2.7 billion tons) of the total 4.4 billion tons

of coal in the quadrangle is available for development. 

 PAR-22
Available

60%

Technologic 

Restrictions

22%

Land-use 

Restrictions

18%

Results of Hilight Quadrangle

Coal Availability Study by USGS

Original Coal: 4.4 Billion Tons

Land-use 

 Restrictions 18 %

Technologic

 Restrictions 22 %

Available 60 %

 PAR-23
(444 million tons) (305 million tons)

72%

 Main Wyodak

 (1,909 million tons)

 17% 

Lower Wyodak

 11%

Rider Wyodak 

The total available coal (fig. PAR-2) is 

composed of these three beds. 

Sixty percent of the total resources, 

or 2.7 billion tons, is available for 

mine development.

 PAR-24
 67% Available 

 24% Restricted by land-use

 considerations

 9% Restricted by technologic

 considerations

 

 Land-use

Restrictions

 Available 

(1.9 billion tons) 

Technologic

Restrictions

 (261 million tons) 

 

Power lines

 5%

Railroads

 9%

Gas plant

 1% Cemetery

 <1%

Oil & gas wells

 85%

 (678 million tons)

 Land-use 

Restrictions 

Main Wyodak coal bed

 PAR-25
Comparing resource calculations

The Rider Wyodak, Main Wyodak, and Lower Wyodak coal

beds together contain 3.8 billion tons, as calculated for this

coal availability study. In another study, Ellis and others

(1999, and Chapter PN) calculated that the Wyodak

(-Anderson) coal interval contains 3.5 billion tons in the

Hilight quadrangle. These two resource estimates are quite

similar, considering that the Wyodak coal beds were

designated somewhat differently in the two studies.

 PAR-26
Part 4. U.S. Bureau

of Mines study of

coal availability and

recoverability in the

Hilight quadrangle

Determining the amount of coal that is profitable to mine

 PAR-27
Hilight quadrangle

Bighorn

Mountains

WYOMING

RIVER

POWDER

BASIN

MONTANA

 Location of the Hilight quadrangle

 PAR-28
COAL RECOVERABILITY STUDIES

COAL AVAILABLE FOR MINING

- minus -

MINING LOSSES

- minus -

WASHING LOSSES

- equals -

RECOVERABLE RESOURCES

- minus -

MINABLE RESOURCES TOO COSTLY TO EXTRACT

- equals -

ECONOMICALLY RECOVERABLE RESOURCE

(Reserve)

 PAR-29
• Recoverable Resource—That part of the

available coal that is left after normal mining and

cleaning losses are subtracted. Costs involved with the

extraction and cleaning of the coal are not considered,

nor is the potential selling price of the coal.

• Economically Recoverable Resource—That

part of the recoverable coal that can be mined, cleaned,

and marketed at a profit (depends on the mine location,

the characteristics of the coal bed, the quality of the coal,

and the mining methods used). Also known as a reserve.

Coal recoverability terms

 PAR-30
 Helpful concepts

• Some factors (such as coal thickness and overburden

thickness) are considerations in both availability and

recoverability calculations. The recoverable resource is a

part or a subset of the available resource.

For example, coal beds that are thick enough to be

considered available resources may be too thin to be

profitably mined, and thus would not be part of the

recoverable coal estimate.

 PAR-31
Helpful concepts, continued

• Both the U.S. Geological Survey and the U.S. Bureau of

Mines (USBM) separately studied coal availability in the

Hilight quadrangle (see Part 3 and Part 4) as part of a

cooperative effort to develop availability methodology for

the western United States. The two agencies used different

techniques and assumptions, and thus their results are not

directly comparable (table PAR-1).

• The USBM, however, added to its availability study a coal

recoverability calculation that built on the same techniques

and assumptions used in the USBM availability study.

Thus the two parts of the USBM study can be legitimately

compared and contrasted (table PAR-1).

 PAR-32
Helpful concepts, continued

• Restrictions to mining vary with location and local

land-management regulations. Thus, different study

areas can have different mining restrictions and

availability considerations.

• This report reflects reasonable assumptions concerning

restrictions to mining based on local practices in the

Powder River Basin, Wyoming and Montana. A more

detailed determination of restrictions and other

availability considerations would occur during the

leasing and mine-planning phases of property

development.

• All tonnage figures are in short tons.

 PAR-33
Table PAR-1. Differences between the

two studies of the Hilight quadrangle

 USGS availability study

•Original resources: 4.4 billion tons

• Percent of original available: 60

•Modeled 5 coal beds

•Power line and cemetery included

as restrictions to mining

•Entire area of Hilight oil and gas

field considered unavailable for

mining

USBM availability and

 recoverability study

• Original resources: 3.6 billion tons

• Percent of original available : 95

• Percent of original recoverable: 89

• Percent economically recoverable: 11

• Modeled 2 coal-bed mining intervals

• Power line and cemetery not included

as restrictions to mining

• Only areas around individual oil and

gas wells considered unavailable for

mining

 PAR-34
The coal recoverability process calculates the amount of overburden and

interburden (waste rock) which would need to be removed to access

the coal beds of interest. 

Thickness of overburden

and interburden to be 

removed during mining

Hilight quadrangle

500

300

400

100

600

200

Feet

3 Miles

Coal outcrop

 PAR-35
(Rider+Main+Lower Wyodak)

From drill hole data, we derive the total thickness of coal beds that meet

the mining criteria for adequate thickness and coal quality.

 Total coal thickness 

Hilight quadrangle

100

75

50

25

Feet

3 Miles 

Coal outcrop

 PAR-36
It is most economic to mine areas that have the lowest stripping ratios 

(for example, 1:1 or 2:1). In current practice in the Powder River Basin, 

it is not profitable for coal mines to operate in areas where the stripping ratio 

is higher than about 3:1.

Ratio of waste rock

to minable coal 

(Stripping ratio) 

Hilight quadrangle

3 Miles

6:1

8:1

2:1

4:1

Coal outcrop

 PAR-37
0 1 Mile

105°22'30"W

43°52'30"N

105°15'W 

43°45'N

Hilight gas plant and 

surrounding area

Railroad 

Active oil and 

gas wells

 Alluvial valley floor

Coal outcrop

Area underlain by

 Wyodak coal 

U.S. Bureau of Mines availability study

Restrictions to mining

 PAR-38
0 500 1000 1500 2000 2500 3000 3500 4000

3,636 million tons

 3,227 

Economically recoverable resource 

U.S. Bureau of Mines results: 

Hilight coal availability and recoverability

3,470 million tons

 Original resource

 Available resource 

 Recoverable resource

(100 percent

(89 percent of original resource)

 (11 percent of original resource)

of original resource) 

(95 percent of original resource)

million tons

389 million tons

Millions of tons

 PAR-39
 COAL

RESOURCE

 ORIGINAL

 REMAINING

 AVAILABLE

RECOVERABLE

 ECONOMIC

 EXCLUSIONS

 NONE

 MINED AND

 LOST IN MINING

 RESTRICTED

 MINING + CLEANING

 LOSSES

 UNECONOMIC

U.S. Bureau of Mines results:

 Hilight coal availability and recoverability

 100 %

 79 21

 59

11

89

95

100

100 percent

6

5

 78

 PAR-40
Part 5. Coal availability Part 5. Coal availability

 in the Willow Crossing in the Willow Crossing

7.5' quadrangle, 7.5' quadrangle,

Montana Montana

A completed study in the Montana part of the Powder River Basin

• Click here to read Summary text in Appendix PAR-2

 PAR-41
COAL AVAILABILITY STUDIES

 ORIGINAL COAL

- minus -

 AREAS ALREADY MINED

- minus -

LAND-USE RESTRICTIONS

- minus -

TECHNOLOGIC CONSIDERATIONS

- equals -

AVAILABLE COAL

 PAR-42
Helpful concepts

• Restrictions to mining vary with location and with

local and State land-management regulations.

Thus, different study areas can have different

restrictions and availability considerations.

• All tonnage figures are in short tons.

 PAR-43
Colstrip E

Colstrip SW

Willow

Crossing

Half

Moon

Hill

Otter

0 10 20 30

Miles

For t Union

Formation

Lignite

Region

Subbituminous

Coal Region

2

1

4 3

Forsyth

Miles City

Broadus

Great Falls

Missoula

Helena

Butte

Billings

12

212

15

90

15

90

90

94

94

90

Coal availability study areas 

in the Montana part 

of the Powder River Basin.

The Willow Crossing 7.5-minute 

quadrangle (number 1 on lower map)

is the subject of this report. Studies in 

areas 2, 3, and 4 are underway 

or proposed.

Montana

 PAR-44
2.6

5.0

4.9

5.8

5.4

8.7

2.9

2.6

2.8

4.9

45.4

4.7

5.7

6.9

2.0

5.1

4.0

9.6

COOK

WALL

PAWNEE

BREWSTER-ARNOLD

CACHE

MACKIN-WALKER

KING

UPPER SAWYER

LOWER SAWYER

A

KNOBLOCH

CALVERT

NANCE

LAY CREEK

FLOWERS-GOODALE

WITHAM

TERRET

STAG

< 20

110-130

150-180

80-140

60-180

40-80

0-60

50-120

0-60

0-60

60-120

10-60

20-80

35-55

15-45

0-30

45-85

25-35

< 20

Tertiar

y

Paleocene

Fort Union

Tongue River

lower middle upper

SYSTEM

SERIES

FORMATION

MEMBER

INFORMAL DIVISION

LITHOLOGY

AVERAGE 

COAL THICKNESS

(in feet)

COAL BED

NAMES

 AVERAGE 

INTERBURDEN

 THICKNESS

(in feet)

Generalized composite stratigraphic section 

for the Willow Creek quadrangle

Rocks between 

the coal beds 

are sandstone, 

siltstone, shale, 

claystone, and

clinker. 

 PAR-45
Figure PAR-3. Mining restrictions in the 

Willow Crossing quadrangle. These areas 

are not available for surface mining because

of land-use or technologic restrictions.

106°15'W

45°37'30"N

106°7'30"W 

45°30' N

0 1 Mile

Restrictions

Alluvial valley floors 

Willow Crossing 

National Forest

cemetery

 PAR-46
Figure PAR-4. Additional restrictions affecting 

mining in the Willow Crossing quadrangle. These

land-use restrictions encompass both unsuitable areas 

and multiple-use areas where mitigation would be

necessary in order to mine.

 Restrictions to mitigate 

 Roads

 Power lines

 Telephone lines

 Buildings

0 1 Mile

 PAR-47
This chart shows the percentage of the original coal resource 

that is contained in each mining restriction and the percentage 

that is available. Total unavailable coal in the Willow 

Crossing quadrangle is 2.4 billion tons.

 PAR-48

Other

1%

Buildings

1%

Available

44%

Alluvial valley floors

7%

National Forest

28%

Too-thin

12%

Too-deep

5%

Powerlines

2%
This chart shows the percentage of the total available 

resource contained in each coal bed. The total available

resource in the Willow Crossing quadrangle is 

1.9 billion tons.

 

 PAR-49

Lay Creek

6%

Terret

6%

Other

1%

Sawyer (incl. Upper 

and Lower)

Stag 1%

1%

Knobloch

65%

Calvert

2%

Nance

5%

Flowers-Goodale

13%
AVAILABLE

1.9 billion tons 

(44%)

MINED-OUT

(less than 1%)

UNAVAILABLE

2.4 billion tons 

(56%)

RESTRICTED

AVAILABLE

Results of the availability study of the Willow 

Crossing quadrangle (under restrictions shown in 

fig. PAR-3 and fig. PAR-4).

 

 PAR-50
Available

48%

Technologic 

Restrictions

15%

Land-use 

Restrictions

37%

Results of the Willow Crossing

Coal Availability Study

(Using only restrictions in fig. PAR-3)

Original Coal: 4.3 Billion Tons

 Land-use 

 Restrictions 37 %

 Technologic

 Restrictions 15 %

 Available 48 %

 PAR-51
 Classification of restraints to coal mining in the Willow Crossing quadrangle

TYPE 

TECHNOLOGICAL LAND-USE

Restrictions to mining COAL THICKNESS

OVERBURDEN THICKNESS

ALLUVIAL VALLEY FLOORS

NATIONAL FOREST LANDS

CEMETERIES

Restrictions that are INHABITED BUILDINGS

commonly mitigated TELEPHONE LINES

POWER LINES

ROADS

 PAR-52

CATEGORIES
COAL BED ORIGINAL MINED-OUT REMAINING RESTRICTED AVAILABLE

Cook 12 0 12 12 0

Wall 131 0 131 131 0

Pawnee 2,268 0 2,268 2,268 0

Brewster-Arnold 9,657 0 9,657 9,657 0

Cache 13,337 0 13,337 13,337 0

Mackin-Walker 35,086 0 35,086 35,086 0

King 10,580 0 10,580 10,312 268

Upper Sawyer 13,415 0 13,415 11,232 2,183

Sawyer 72,689 114 72,575 58,595 13,980

Lower Sawyer 20,383 0 20,383 15,787 4,596

A 55,321 0 55,321 39,403 15,918

Knobloch 1,973,875 0 1,973,875 730,787 1,243,088

Calvert 235,873 0 235,873 197,975 37,898

Nance 346,735 0 346,735 242,067 104,669

Lay Creek 364,679 0 364,679 251,451 113,228

Flowers-Goodale 556,163 0 556,163 303,231 252,932

Witham 91,928 0 91,928 91,928 0

Terret 281,505 0 281,505 173,994 107,511

Stag 237,587 0 237,587 210,785 26,802

TOTAL 4,321,223 114 4,321,110 2,398,037 1,923,073

 PAR-53

Summary of tonnages for original, mined-out, 

remaining, restricted, and available coal resources in 

the Willow Crossing quadrangle

(in thousands of short tons; rounded to whole tons)
Part 6. The Middle

Pod study area,

Gillette Coalfield,

Wyoming

Availability considerations in a large area of active coal mining

 PAR-54
 Factors in selecting study areas (fig. PAR-1)

• Presence of Coal Resource

• Mining Activity—Past and Current

• Geologic and Cultural Characteristics

• Resource Management Issues

• Data Accessibility

 PAR-55
Hilight quadrangle 

Middle Pod Study Area 

Bighorn

Mountains

WYOMING

RIVER

POWDER

BASIN

MONTANA

Index map showing the Middle Pod 

 coal availability and recoverability study area. 

 The Hilight 7.5-minute quadrangle is 

 within the Middle Pod study area.

The USGS designed this study to calculate 

available and recoverable coal in a

large area of the Powder River Basin and 

to better characterize the extensive

Wyodak coal deposit in the Gillette coalfield.

We delineated an area we call "Middle Pod" 

study area. It encompasses eight full 

7.5-minute quadrangles and parts of eight 

additional quadrangles; the total area is

about 600 square miles. The full data-collection area

extends three miles beyond the study area,

in all directions. We examine data in this three-mile 

border to help us verify geologic trends within the

study area. 

The Middle Pod study area is in the 

central part of the Wyodak coal deposit,

which also has a Northern Pod and a

Southern Pod. Each pod of the Wyodak coal

deposit is currently being mined. The mines in

the Middle Pod are shown in the next frame.

The Middle Pod study is just beginning. 

The graphics in this chapter illustrate some 

of the factors that will be considered 

when available and recoverable coal resources

are calculated in this study area. 

Middle Pod of the Gillette Coalfield

 PAR-56
Caballo

Black Thunder

Coal Creek

Bel

Ayr

Jacobs Ranch

Rocky Butte

Wyodak

Gillette

SR450

SR387

SR

59

SR 80

I-90

0 10 Miles

Middle Pod

Roads

Railroads

Hilight Quadrangle

7 ' .5 quadrangles

Hilight gas plant

Mines

Power plant

Wright

Wyodak

outcrop

coal bed

le

Caballo Rojo

Cordero

Middle Pod 

study area

Data collection 

 area

5

T 43 N

R 73 W

T 50 N

R 69 W

Study area, coal mines,

 and infrastructure

 PAR-57
Gillette

0 10Miles

Dry-land crops

Irrigated crops

Mixed- grass prairie

Wyoming Big S a gebrush

Greasewood fans and flats

Ponderosa pine

Shrub- dominated riparian

Grass- dominated riparian

Surface mining operations

Land cover in the 

Middle Pod study area

City of Gillette

5

Middle Pod 

study area

Data collection 

 area

Land cover types

43 42' 23" N

105 37' 30" W 105 8' 32" W

44 17' 37" N

 PAR-58
Perennial streams

Alluvial valley floors

Water bodies

Power plant

Roads

Railroads

Coal mines

Wyodak coal outcrop 

Clinker areas

Raptor areas

Sage grouse areas

 Availability factors

 to be considered 

 in the Middle Pod 

 study area

Middle Pod study

Area in which BLM supplied land-use data 

USGS data collection area

area

0 5 Miles

105 8' 32" W

43 42' 23" N

105 37' 30" W

44 17' 37" N

 PAR-59
5.9 percent of the surface

is Federally owned

Data collection area

0 5 10

Surfaceownership status 

Middle Pod study area

Wyodak coal outcrop

U.S. Bureau of Land Management

U.S. Forest Service

State

Private

Land Status

Miles (after Biewick and others, 1998)

105 8' 32" W

43 42' 23" N

105 37' 30" W

44 17' 37" N

 PAR-60
0 5

84 percent

of the Middle Pod study area

is underlain by 

Federally owned coal

 Coal Ownership 

Federal coal

Non-Federal coal

Middle Pod study area

Data collection area

Miles

105 8' 32" W

43 42' 23" N

105 37' 30" W

44 17' 37" N

(after Biewick and others, 1998)

 PAR-61
This map shows 

the thickness of

the Main Wyodak 

coal bed in and 

around the 

Middle Pod area

feet

7.5' quadrangles

Data points

Wyodak outcrop

Main Wyodak 

 coal isopach:

Miles

43 42' 23" N

105 37' 30" W

44 17' 37" N

105 8' 32" W

 PAR-62
 Part 7. Results

and conclusions 

 

 PAR-63
100 0 Miles 100

Bu l l Mts.

N

WYOMING

Willow Crossing

Otter

Colstrip E

Colstrip SW

Hilight

MONTANA

Powder

River

Basin

Powder River Basin 

Half Moon Hill

Middle Pod area

complete

complete

Study in progress

Coal-bearing rocks

Cretaceous

Tertiary

Major Railroads

 Availability study

Availability and 

recoverability 

studies

 

Powder River Basin study areas for coal availability and recoverability. 

All areas shown are 7.5-minute quadrangles except the Middle Pod area. 

 PAR-64
Available

54%

Technologic 

Restrictions

18%

Land-use 

Restrictions

28%

Averaged Results:

Hilight and Willow Crossing Availability Studies

Combined Original Coal: 8.7 Billion Tons

Land-use 

 Restrictions 28 %

Technologic

 Restrictions 18 %

Available 54 %

Percents shown are averages of values from the two completed studies.

Hilight values are taken from the USGS availability study.

 PAR-65
0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Combined results: Hilight (USGS study) and 

Willow Crossing availability studies

4,698 million tons

8,700 million tons

(100 percent of original )

(54 percent of original )

Millions of tons

8,700 million tons

 Original resource (100 percent of combined 

Remaining resource

 Available resource 

original resource) 

 PAR-66
• Recoverable Resource—That part of the

available coal that is left after normal mining and

cleaning losses are subtracted. Costs involved with the

extraction and cleaning of the coal are not considered,

nor is the potential selling price of the coal.

• Economically Recoverable Resource—That

part of the recoverable coal that can be mined, cleaned,

and marketed at a profit (depends on the mine location,

the characteristics of the coal bed, the quality of the coal,

and the mining methods used). Also known as a reserve.

Coal recoverability terms

 PAR-67
0 500 1000 1500 2000 2500 3000 3500 4000

3,636 million tons

 3,227 

Economically recoverable resource 

U.S. Bureau of Mines results*: 

Hilight coal availability and recoverability

3,470 million tons

 Original resource

 Available resource 

 Recoverable resource

(100 percent

(89 percent of original resource)

 (11 percent of original resource)

of original resource) 

(95 percent of original resource)

million tons

389 million tons

Millions of tons

* See Table PAR-1 for study criteria

 PAR-68
 COAL

RESOURCE

 ORIGINAL

 REMAINING

 AVAILABLE

RECOVERABLE

 ECONOMIC

 EXCLUSIONS

 NONE

 MINED AND

 LOST IN MINING

 RESTRICTED

 MINING + CLEANING

 LOSSES

 UNECONOMIC

U.S. Bureau of Mines results*:

Hilight coal availability and recoverability

*See Table PAR-1 for study criteria

 100 %

 79 21

 59

11

89

95

100

100 percent

6

5

 78

 PAR-69
Conclusions about available and recoverable

coal in the Powder River Basin

• The average of the two availability studies in the Basin show

that 54 percent of the original coal is available for

development. Land-use restrictions remove about 28

percent of the original coal from development; technological

considerations remove another 18 percent.

• The U.S. Bureau of Mines study showed that only 11 percent

of the original coal resource calculated for the Hilight

quadrangle is economically recoverable.

• Many availability considerations in the Powder River Basin

can be mitigated so that mining can still proceed. However,

mitigation might add complexity and cost to the mining

operation.

 PAR-70
• Methodologies for determining availability and recoverability can

be applied routinely to future coal production regions, including

multiple-quadrangle areas.

• Only a fraction of the coal resource is available for development.

Even less of the resource is economically recoverable.

• Traditional coal-producing regions and local economies may be

severely impacted by lack of economic coal reserve.

• National, regional, and local planners are becoming aware of

these projections.

• Coal availability and recoverability determinations can better

guide us as an economy and a society as we develop our

 natural resources and the lifestyles that depend on them.

General findings,

Coal availability and recoverability

 PAR-71
References cited

 PAR-72
References cited

• Biewick, Laura R.H., Urbanowski, Shayne R., Cain,

Sheila, and Neasloney, Larry, 1998, Land status and

Federal mineral ownership in the Powder River Basin,

Wyoming and Montana: a digital data set for Geographic

Information Systems: U.S. Geological Survey Open-File

Report 98-102.

Available on the Web at:

http://energy.cr.usgs.gov/fedland/prb_own.html

 PAR-73
 References cited, continued

• Ellis, M.E., Gunther, G.L., Flores, R.M., Ochs, A.M., Stricker, G.D.,

Roberts, S.B., Taber, T.T., Bader, L.R., and Schuenemeyer, J. H., 1999,

Preliminary report on the coal resources of the Wyodak-Anderson Coal Zone,

Powder River Basin, Wyoming and Montana: U.S. Geological Survey OpenFile Report 98-789-A.

Available on the Web at:

http://greenwood.cr.usgs.gov/pub/open-file-reports/ofr-98-0789-a/

• Molnia, Carol L., Biewick, Laura R.H., Blake, Dorsey, Tewalt, Susan J.,

Carter, M. Devereux, and Gaskill, Charlie, 1997, Coal availability in the

Hilight quadrangle, Powder River Basin, Wyoming: a prototype study in a

western coal field: U.S. Geological Survey Open-File Report 97-469.

Available on the Web at:

http://energy.cr.usgs.gov:8080/coal/OF-97-469.html

 PAR-74
Appendices

Appendix PAR-1. Summary text for Part 3.

"Results of the first western coal availability

study—Hilight quadrangle, Powder

River Basin, Wyoming"

 Appendix PAR-2. Summary text for Part 5.

"Coal availability in the Willow Crossing 7.5-

minute quadrangle, Montana"

 PAR-75
Helpful concepts

• Restrictions to mining vary with location and with

local and State land-management regulations.

Thus, different study areas can have different

restrictions and availability considerations.

• In the Willow Crossing summary text (Appendix

PAR-2), the restriction classifications “Type 1”

and “Type 2” are equivalent to “Category 1” and

“Category 2,” respectively, as used in the Hilight

summary text (Appendix PAR-1).

• All tonnage figures are in short tons.

 PAR-76
Appendix PAR-1

Summary text for Part 3 of Chapter PAR

RESULTS OF THE FIRST WESTERN

COAL AVAILABILITY STUDY 3⁄4

HILIGHT QUADRANGLE,

 POWDER RIVER BASIN, WYOMING

By C.L. Molnia1, L.R.H. Biewick1, Dorsey Blake1,

S.J. Tewalt2, M.D. Carter2, and Charlie Gaskill 3

Note: This text is modified from: Molnia, C. L., Biewick, L. R. H., Blake, D.,

Tewalt, S. J., Carter, M. D., and Gaskill, C., 1996, Results of the first western coal

availability study Hilight quadrangle, Powder River Basin, Wyoming, in Chiang,

S.-H., ed., Coal Energy and the Environment, 1996: Thirteenth Annual

International Pittsburgh Coal Conference Proceedings, p. 798-803.

 

 

1 U.S. Geological Survey, Denver, Colorado

2 U.S. Geological Survey, Reston, Virginia

3

 U.S. Bureau of Land Management, Casper, Wyoming
PAR-78

ABSTRACT

 The U.S. Geological Survey, in cooperation with the U.S. Bureau of Land

Management, Geological Survey of Wyoming, and U.S. Bureau of Mines, has

produced an estimate of the amount of available coal in an area about 35 mi south of

Gillette, Wyoming, where the Wyodak coal bed is, in places, more than 100 ft thick.

 Available coal is coal that actually is accessible for development under

current regulatory, land-use, and technologic conditions. This first western coal

availability study, in the Hilight quadrangle, has shown that approximately 60

percent (2.7 billion tons4) of the total 4.4 billion tons of original coal resources in the

quadrangle is available for development (fig. PAR-5). Of this total 4.4 billion tons,

2.9 billion tons are contained in the Main Wyodak coal bed; 67 percent (1.9 billion

tons) of this coal bed is considered available. 

Local coal-development considerations include dwellings, railroads, pipelines,

power lines, wildlife habitat (eagles), alluvial valley floors, cemeteries, the Hilight oil

and gas field, and the Hilight gas plant. Some of these considerations would be

mitigated so that surface mining could proceed; others presently preclude mining in

their vicinity.

 

4 All tonnage measurements in this report are given in short tons.
PAR-79

Traditional Federal and State coal resource estimates have not taken into account the

multitude of land-use, environmental, regulatory, and technologic restrictions

affecting coal mining. This has led some Federal, State, and local planners to

probably overestimate the future supply of the Nation's coal. A cooperative

program, referred to as "Coal Availability," among the U.S. Geological Survey and

other Federal agencies and State geological surveys, was initiated in 1987 to identify

current major constraints on the availability of coal resources for development and to

estimate the amount of remaining coal resources that may be accessible for

development under those constraints (Carter and Gardner, 1989, 1994).

Because the Coal Availability Program has been successful in the Eastern United

States, there was great interest in extending the program to western coalfields to see

what factors would be involved and how the process could be applied to the

different geologic and mining conditions. This Hilight study is the first western Coal

Availability study.

GEOLOGIC SETTING AND COAL MINING

The Powder River Basin covers about 22,000 sq mi in northeastern Wyoming and

southeastern Montana. Along the eastern side of the Powder River Basin, the Fort

Union Formation (Paleocene) contains some of the most significant deposits of

low-sulfur subbituminous coal in the world (Molnia and Pierce, 1992), including the

thick Wyodak coal bed found in the Hilight quadrangle. The Wyoming part of the

Powder River Basin provides about 20 percent of the coal produced annually in the

United States (Mining Engineering, 1994).
PAR-80

The study site, the Hilight 7.5-minute quadrangle, is an area of about 50 sq mi and is

located in Campbell County, Wyoming, about 35 mi south of the town of Gillette

(fig. PAR-6). The Hilight quadrangle is situated between the Coal Creek mine

(owned by Thunder Basin Coal Co., subsidiary of ARCO Coal Co.) and the Jacobs

Ranch mine (owned by Kerr-McGee Coal Co.). There has been no commercial

mining todate in the Hilight quadrangle, but the site of the formerly proposed

Keeline coal mine (Neil Butte Co.) is fully within the quadrangle. The proposed

productive capacity of that mine was to have been as much as 12 million tons

annually.

The economic coal bed in the Hilight quadrangle is the Wyodak coal bed of the

Tongue River Member of the Fort Union Formation (fig. PAR-7). We recognize

three divisions of the Wyodak coal bed: Rider, Main, and Lower. The Main

Wyodak bed is much thicker than the others; in places, it contains 120 ft of coal, and

has several partings. Overburden thickness for the Main Wyodak coal bed ranges

from 15 to more than 600 ft within the Hilight quadrangle.

The Wyodak coal bed in the Keeline lease area is a non-agglomerating,

subbituminous class C coal which averages approximately 9,150 BTU/lb on a

moisture, mineral-matter-free basis (Neil Butte Company, 1985). On an as-received

basis, heating value of the coal averages 8,350 BTU/lb; average moisture is 28

percent, ash content is 7.9 percent, and sulfur content is 0.6 percent.
PAR-81

GENERAL FACTORS AFFECTING AVAILABILITY OF

COAL RESOURCES

 [Note: Not every factor listed will ultimately restrict coal mining in the quadrangle.]

UNSUITABILITY CRITERIA DETERMINATIONS

The coal unsuitability criteria listed in the Federal Regulations (43 CFR 3461) are

applicable to the Hilight quadrangle. The unsuitability criteria are used to determine

if an area can be mined by surface mining methods. The 43 CFR 3461 regulations

are issued under the authority of, and implement several major provisions of, Public

Law 95-87, which is the Surface Mining Control and Reclamation Act of 1977 (30

U.S.C. 1201 et seq.). Within the Hilight quadrangle, the U.S. Bureau of Land

Management (1984) has identified the following six elements of the unsuitability

criteria:

Railroad corridor Raptor sites, including golden eagles

Cemetery Lands in certain Federal systems

Dwellings Alluvial valley floor (potential)
PAR-82

AVAILABILITY FACTORS TO BE CONSIDERED IN ADDITION

TO UNSUITABILITY CRITERIA

Other land-use conflicts 1⁄2Geological and mining factors

Pipelines 1⁄2 Active mines; previously mined areas

Hilight oil and gas field 1⁄2 Limit of coal3⁄4 Outcrop and clinker

Hilight gas plant 1⁄2 Overburden depth

Power line 1⁄2 Overburden geochemistry

Gravel pits 1⁄2 Coal quality

Surface- and coal-ownership 1⁄2 Coal beds too thin

Roads 1⁄2

GROUPING OF CONSIDERATIONS FOR USE IN

AVAILABILITY CALCULATIONS

 

After studying local mining practices and consulting with the land-management

agency, we grouped the factors affecting the availability of coal into two sets: those

(Category 1) that were likely to be restrictions to a mining operation in the Hilight

quadrangle (fig. PAR-8), and those (Category 2) that probably could be mitigated

(fig. PAR-9). Category 1 considerations would result in a certain amount of coal

tonnage being unavailable for coal mining; in contrast, Category 2 considerations

would likely increase the cost and complexity of the mining operation, but, through

mitigating measures, may allow for mining of the coal involved.
PAR-83

Category 1 considerations: Category 2 considerations:

(1) Railroad corridor (1) Dwellings

(2) Power line (2) Alluvial valley floor

(3) Cemetery (3) Pipelines

(4) Hilight oil and gas field (4) Raptor areas

and other active oil and gas wells (5) Inactive oil and gas wells

(5) Hilight gas plant 

COMPUTER TECHNIQUES

 The major steps required in calculating coal resources for this study include: (1)

acquisition of coal stratigraphic and analytical data, and their transfer into a pointdata management system; (2) correlation and grouping of coal beds by bed or zone

name; (3) transfer of point-source and line data into a geographic information

system (GIS); (4) conversion of point-source and line data into grids (raster data)

using GIS programs; (5) calculation of original coal resources from grids; and,

finally, (6) calculation of restricted coal tonnages and available coal tonnages by

overburden thickness and by Category 1 and 2 restrictions. The methodology for

coal-resource calculations used in this study follows the Coal Resource

Classification System of the USGS, as described in (Wood and others, 1983). 

RESULTS COAL AVAILABILITY CALCULATION

Because no commercial mining has yet taken place in the Hilight quadrangle, the

original resources are equal to the remaining resources (4.4 billion tons). However,
PAR-84

were mining to take place under the Category 1 restrictions, about 60 percent of the

original coal resources in the Hilight quadrangle would be considered available for

development. This 60 percent represents the sum of the available Rider, Lower,

and Main Wyodak coal resources (totaling approximately 2.7 billion tons) as a

proportion of the total 4.4 billion tons of original coal in the quadrangle. All of the

resources contained within the Wildcat, Moyer, and Oedekoven coal beds are

considered unavailable because of their depth.

Of the total 4.4 billion tons in the quadrangle, 2.9 billion tons are contained in the

Main Wyodak coal bed; 67 percent, or 1.9 billion tons of the Main Wyodak coal

bed are considered available for development.

If the Category 2 restrictions (fig. PAR-9) for the Rider, Lower, and Main Wyodak

beds are added to the Category 1 restrictions, then an additional 807 million tons of

coal would be unavailable. Addition of the Category 2 restrictions would mean that

only 1.9 billion tons of the three Wyodak coal beds would be available for mining;

this represents 42 percent of the original coal resources in the quadrangle.

COMPARISON TO OTHER COAL AVAILABILITY STUDIES

Studies in the Appalachian coal region indicate that, overall, only 50 percent of the

original coal resource in that area is available for development (Carter and Gardner,

1994). In the Hilight quadrangle, there has been no mining yet; whereas in the

Appalachian region, much of the original coal resource is already mined-out. Of

the remaining Appalachian coal resource, no more than 60 percent is considered

available for future development Carter and Gardner, 1984). Further,

the U.S. Bureau of Mines Coal Recoverability Studies of the Appalachian region
PAR-85

have shown that less than 10 percent of the original resource can be mined and

marketed at a currently economic profit (Rohrbacher and others, 1993). 

There are significant differences in coal quality parameters between Appalachian

coal and Powder River coal; these differences must be considered in any

comparison of available resources of different regions. In general, Powder River

Basin coal is lower in rank, lower in sulfur content, and higher in moisture content

than Appalachian coal. Also, there are several differences between Appalachian and

Powder River Basin coal development. Powder River Basin coal development

involves relatively flat topography; numerous, gently-dipping, thick coal beds;

undeveloped areas and few population centers; no underground mining; mostly

Federally-owned coal deposits; and different land-ownership patterns,

environmental regulations, and land management policies than in the Appalachian

coal region. All of these factors influence the amount of coal that is available in a

region. Availability determinations guide us as an economy and a society as we

develop our natural resources and the lifestyles that depend on them.

REFERENCES CITED

Carter, M.D., and Gardner, N.K., 1989, An assessment of coal resources available

for development: U.S. Geological Survey Open-File Report 89-362.

Carter, M.D., and Gardner, N.K., 1994, Coal availability studies3⁄4 The impact of

restrictions on the development potential of coal resources, in Chiang, ShiaoHung, ed., Coal3⁄4 Energy and the Environment: 11th Annual International

Pittsburgh Coal Conference, p. 1-4.
PAR-86

IntraSearch, 1979, Coal resource occurrence and coal development potential maps of

the Hilight quadrangle, Campbell County, Wyoming: U.S. Geological

Survey Open-File Report 79-69.

Mining Engineering, vol. 46, no. 8 (August, 1994).

Molnia, C.L. and Pierce, F.W, 1992, Cross sections showing coal stratigraphy of

the central Powder River Basin, Wyoming and Montana: U.S. Geological

Survey Miscellaneous Investigations Series Map I-1959-D, scale 1:500,000.

Neil Butte Company, Mine and reclamation plan for the Keeline Mine, 1985.

Rohrbacher,T.J., Teeters, D.D., Osmonson, L.M., and Plis, M.N., 1994, Coal

recoverability and the definition of coal reserves, Central Appalachian Region,

1993: U.S. Bureau of Mines Open-File Report 10-94.

U.S. Bureau of Land Management, 1984, Second draft resource management plan

and draft environmental impact statement for the Buffalo Resource Area,

Casper District, Wyoming.

Wood, G.H., Jr., Kehn, T.M., Carter, M.D. and Culbertson, W.C., 1983, Coal

resource classification system of the U.S. Geological Survey, U.S.

Geological Survey Circular 891.
 Available:

2.7 billion tons 

60% of original

 Unavailable:

 1.7 billion tons

 40% of original

Figure PAR-5. This USGS study shows that approximately 60 percent

(2.7 billion tons) of the total 4.4 billion tons of coal in the Hilight 

quadrangle is available for development. 

 PAR-87
CAMPBELL

COUNTY

CONVERSE

COUNTY

R 73 W

R 69 W

T 52N

T40 N

Buckskin

Rawhide

Dry Fork

Caballo

Coal Creek

Black Thunder

North Rochelle

Rochelle 

Antelope

Cordero

Eagle Butte

Fort Uni Wyodak

North Antelope 

Rocky Butte

Belle Ayr

Caballo

Rojo

Gillette

Hilight quadrangle

Jacobs Ranch

on

105°30'W

44°30' N

44° N

43°30' N

105°30'W

Figure PAR-6. Surface coal mines near the

Hilight quadrangle. 

0 6 Miles

 PAR-88
550

80

11

5

3

250

SYSTEM

SERIES

FORMATION

COAL BEDNAME

?

TERTIAR

Y

PALEOCENE EOCENE

WASATCH FOR

T UNION 

WYODAK Lower Main

Rider

Wildcat

Moyer

Oedekoven

LITHOLOGY

THICKNESS  (FEET)

Figure PAR-7. Generalized 

composite stratigraphic 

section for the Hilight 

quadrangle.

Non-coal rock:

siltstone, mudstone,

claystone, shale,

and sandstone

Coal 

 PAR-89
0

Restrictions to mining

Power line

 Railroad

 Producing 

 oil and gas field

Producing 

oil and gas well

 

Area underlain by

Wyodak coal bed

105° 22'30"W

 

43°45'N

 Coal

Outcrop

1 mile

Gas plant

Cemetery

105°15'W

43°52'30"N

Figure PAR-8. Restrictions to mining. These areas are not available

for surface mining because of land-use and technologic constraints.

 PAR-90
 Inactive oil and gas well

Considerations 

 Oil and gas pipeline

0 1 mile

 Area underlain by

Wyodak coal bed

105° 22'30"W 105°15'W

 Coal

Outcrop

Alluvial valley floor

Dwellings

 Raptor sites (including

 golden eagles)

43°45'N

 43°52'30"N

Figure PAR-9. Additional mining considerations. Most likely, the coal under these 

areas would be available for mining, but with certain mitigations and stipulations

which might add to the complexity and cost of the mining operation. 

 PAR-91
Appendix PAR-2

Summary text for Part 5 of Chapter PAR

COAL AVAILABILITY IN THE

WILLOW CROSSING 7.5-MINUTE QUADRANGLE,

POWDER RIVER BASIN, MONTANA

By Edith M. Wilde1

1 Montana Bureau of Mines and Geology, Butte, Montana
PAR-93

ABSTRACT

The total original resource in the Willow Crossing 7.5-minute quadrangle is

estimated to be 4.3 billion tons2 (Wilde, in press). The restricted coal is estimated

at 2.4 billion tons (56 percent), and the total available resource is 1.9 billion tons

(44 percent). Eighty percent of the available resource underlies overburden less

than 300 ft thick, and 20 percent underlies from 300 to 500 ft of overburden.

The beds most attractive for future mining are the Knobloch (1.2 billion tons

available), the Flowers-Goodale (252 million tons), and the Sawyer (20.7 million

tons). The entire Sawyer resource area (including the available areas in the Upper

Sawyer, Lower Sawyer, and where the splits merge to form the Sawyer) underlies

overburden less than 150 ft thick.

INTRODUCTION

The Willow Crossing 7.5-minute quadrangle is located in the central part of the

Montana part of the Powder River Basin (fig. PAR-10); for coal evaluation

purposes, it is considered representative of the immediately surrounding area. A

geographic information system (GIS) called GRASS (Geographical Resource

Analysis Support System, U.S. Army Construction Engineering Research

Laboratory) was used to estimate tonnages for the original, mined-out, and

remaining coal; for restrictions to mining; and for available resources. Data from a

total of 948 locations were used for these calculations.

 

2

 All tonnage measurements in this report are given in short tons.
PAR-94

The availability of coal for future mining in the Willow Crossing 7.5-minute

quadrangle is limited by several factors that are broadly categorized as either

technological restrictions or as land-use restrictions (table PAR-2). The

restrictions are also separated into two types based on the possibility of gaining

mining rights through legal action (table PAR-2): Type 1 restrictions are unlikely

to be legally reversible, while Type 2 restrictions are generally mitigated so that

mining can proceed.

Under the currently existing land-use and technological restrictions, ten beds

(King, Sawyer, A, Knobloch, Calvert, Nance, Lay Creek, Flowers-Goodale, Terret,

and Stag) have available resources. The Sawyer bed was locally mined in the past,

but no commercial mines are currently active in any bed. The Knobloch coal bed

is the thickest bed and contains the largest minable resource.

COAL DESCRIPTION

The coal in the Willow Crossing quadrangle is typically rated as subbituminous,

with heating values ranging between 7,000 and 9,500 Btu's per pound, as received.

Ash content varies between 6 and 8 percent, and sulfur content varies between 0.3

and 0.7 percent, both on an as-received basis. Average quality information is from

Warren (1959), Bass (1932), Matson and others (1973), and McKay (1976).

Excluding splits, 11 coal beds crop out in the area, and 6 additional coal beds are

present in the subsurface (table PAR-3 and fig. PAR-11). All coal in this area

exists in the Tongue River Member of the Fort Union Formation (Paleocene). The

general sequence of beds in the Willow Crossing area is shown in figure PAR-11.
PAR-95

RESTRICTION ISSUES

Factors that would restrict or limit the availability of coal for mining are

categorized as either technological or land-use restrictions (table PAR-2).

Technological restrictions considered in the study are thickness of overburden and

thickness of coal beds. Land-use restrictions considered are the location of alluvial

valley floors, National Forests (public lands), cemeteries, roads, inhabited

buildings, telephone lines and power lines. Technological and land-use restrictions

are also separated into two types (table PAR-2) as follows, based on the possibility

of gaining mining rights through legal action.

Type 1 restrictions (fig. PAR-12) are unlikely to be legally reversible and include

both of the technological restrictions, as well as three of the land-use restrictions:

location of alluvial valley floors, National Forest lands, and cemeteries. Coal

underlying these areas is considered unavailable for mining.

Type 2 restrictions (fig. PAR-13) are generally mitigated and include the

remaining land-use restrictions: locations of roads, inhabited buildings, telephone

lines, and power lines. They are considered limited restrictions in this report

because these features are generally moved during mining operations. However,

the mitigation and moving process generally increases the production costs for

mining.
PAR-96

TYPE 1 RESTRICTIONS

Technological Restrictions

Coal-Thickness Factors. The standard U.S. Geological Survey (USGS)

criterion for coal resource classification (Wood, and others, 1983) includes all

resources which are 2.5 or more ft thick and are less than 1,000 ft deep. Some

subroutines in the GRASS GIS programs will not accept decimal ft (that is,

numbers in tenths of feet, such as 10.2) for calculations. Therefore, 2 ft was used

as the lower limit for original resources.

Five ft is considered to be the minimum economically minable thickness by

companies working near the area. The USGS's thickness categories for minable

reserves of subbituminous coal are listed (Wood, and others, 1983) as 5-10 ft, 10-

20 ft, 20-40 ft and greater than 40 ft. The USGS resources module in GRASS

allows only two thickness categories, so “5-40 ft” and “greater than 40 ft” were the

categories used for calculating available resources.

Overburden-Thickness Factors. The common surface-mining practice in the

Powder River Basin area of Montana is to use a ratio of coal thickness to

overburden thickness (“stripping ratio”) as a guide to minability. Companies

mining in the area quote ratios that vary from 3:1 to 10:1. According to mine

representatives, coal under overburden thicknesses of as much as 150 ft will

usually be economic to surface mine. The 150-300-ft range is often surface-mined

as well, but this is a range that might become uneconomic because of conditions

such as bed thickness and production costs. The 300-500-ft range is usually

uneconomic, but may be surface-mined for very thick, good quality beds. It should
PAR-97

be noted that underground mining has not been a common practice in this area

because of the nature of the overburden.

The following divisions were determined to be most applicable for this study:

0-150 ft 3⁄4 Minable by surface techniques;

150-300 ft 3⁄4 Might be surface minable (deep pit);

300-500 ft 3⁄4 Probably too deep, but might be surface

minable under some conditions;

500-1000 ft 3⁄4 Underground minable only;

1000 ft or greater 3⁄4 Probably too deep to mine by either

surface or underground methods.

Land-use Restrictions

Section 82-4-227 of the Montana Strip and Underground Mine Reclamation Act of

1993 (MCA) lists the land-use restrictions along with the boundary limits (the

closest mining can approach the feature) for each restriction. This state legislation

is based on the Federal law known as the Surface Mine Control and Reclamation

Act of 1977 (Public Law 95-87). The areas used for restrictions in this report (fig.

PAR-12 and fig. PAR-13) are based on the limits stated in these documents.

National Forest. The Montana state legislation states “... no strip- or

underground-coal mining operations..., may be conducted on lands within the

boundaries of units of the national park system, ...”, but this document does not

specifically mention National Forests. The Federal regulation states that coal in

public parks and historic sites cannot be mined, except in the extremely rare case in

which all agencies responsible for managing them approve. It also states that
PAR-98

mining may be allowed on National Forest land, but only if the mining will not

interfere in any way with the original purpose for which the land was set aside. In

the Willow Crossing quadrangle, there are two areas of Custer National Forest

which were originally set aside as public recreation areas (fig. PAR-12) and thus

are considered land-use restrictions in this study.

Alluvial Valley Floors. Because ground and surface water is of such great

concern in Montana, and particularly in the semi-arid regions of eastern Montana,

a considerable amount of discussion is given to the subject in the state legislation,

which goes beyond the flowing-stream restrictions listed in the Federal regulation.

The definition of “alluvial valley floor” is given in section 82-4-203 (2) MCA as

“...unconsolidated stream-laid deposits holding streams where water availability is

sufficient for sub-irrigation or flood irrigation agricultural activities; ...” Section

82-4-227(3)(b)(I) MCA, states that no mining will be permitted which will

“...interrupt, discontinue, or preclude farming on alluvial valley floors...” Section

82-4-227(3)(b)(ii) MCA states that no mining will be permitted that would

“...materially damage the quantity or quality of water in surface water or

underground water systems that supply these valley floors...” In the Willow

Crossing quadrangle, the valleys of Otter Creek, Threemile Creek, Home Creek

and East Fork Creek (fig. PAR-12) have been defined and mapped as alluvial

valley floors (Malde and others, 1976) and thus are considered land-use restrictions

in this study.

Cemeteries. Section 82-4-227(7) MCA states that no mining will be permitted if

“....the operation will constitute a hazard to a dwelling house, public building,

school, church, cemetery, commercial or institutional building, public road, stream,

lake, or other public property.” Additionally, section 82-4-227(7) MCA prohibits

mining within 100 ft of any cemetery. The Federal regulation states that surface
PAR-99

mining cannot be conducted through a cemetery; and the Office of Surface Mining

Reclamation and Enforcement (OSM) requests a 100-foot buffer. The Willow

Crossing Cemetery is located in the central part of the quadrangle. It falls within

the confines of the alluvial valley floor restriction (fig. PAR-12), and therefore

does not cause any additional restriction.

TYPE 2 (LIMITED) RESTRICTIONS

The Willow Crossing quadrangle contains a number of inhabited buildings, two

paved public roads, phone lines and power lines (fig. PAR-13). These features are

often moved by mining companies if located on land that will be mined, but are

considered in this report as limited restrictions to mining because of the increase in

cost associated with moving such features.

Inhabited Buildings. No mining is permitted within 300 ft of any inhabited

building according to section 82-4-227(7) MCA. Federal law requires the same

buffer zone. However, according to the state regulations "individual homeowners

may sign a waiver allowing mining up to or through the house." There are homes

and ranches scattered throughout the Willow Crossing quadrangle (fig. PAR-13).

Roads and Highways. Highway 212 runs east-west through the north-central part

of the quadrangle. Another paved road (fig. PAR-13) runs south from Highway

212 through the central part of the area and generally along Otter Creek. Section

82-4-227(7) MCA states that no mining will be allowed within 100 ft of the road

right-of-way. Federal regulation requires the same buffer zone. Both State and

Federal laws allow moving these features during mining.
PAR-100

Utility Lines. There are both power line and phone line rights-of-way located

within the Willow Crossing quadrangle which service homes and ranches in the

area. A restriction of 100 ft from power lines and 50 ft from phone lines is used in

this report. No specific State or Federal regulation prohibits mining through these

areas. However, the lines within the study area are the major line networks for the

entire area and would have to be moved in order to maintain service (fig. PAR-13).

SUMMARY OF RESULTS

ORIGINAL COAL RESOURCES

Original coal resources were calculated for all beds in the area. Total original

resources for the Willow Crossing quadrangle were estimated at 4.3 billion tons

(table PAR-3). Approximately 22 percent of that total (951.3 million tons)

underlies less than 150 ft of overburden. An additional 45 percent (2.0 billion

tons) underlies 150-300 ft of overburden; 300-500 ft of overburden cover 26

percent (1.1 billion tons); and 500-1000 ft of overburden cover 6 percent (277.8

million tons).
PAR-101

MINED-OUT AND REMAINING COAL RESOURCES

Past mining in the area was very limited. Coal was mined from the Sawyer bed,

but the total area and tonnage affected were very small3⁄4 less than 113.8 thousand

tons were removed. Therefore, nearly all of the original resources of the Sawyer

coal bed still remain (106.5 million tons, or 99.9 percent.)

RESTRICTED COAL

Most of the mining restrictions in this area result from land-use conflicts, primarily

because of land defined as alluvial valley floors and National Forest (fig. PAR-14).

Total restricted coal is 2.4 billion tons (56 percent of the original and remaining

resources). Type 1 restrictions (technological restrictions: coal too deep or too thin

to mine; land-use restrictions unlikely to be removed by legal processes) account

for 94 percent of the total restricted tonnage. Type 2 restrictions (land-use

restrictions which are usually mitigated) account for only 6 percent of the total

restrictions. By themselves, the technological restrictions account for 34 percent

of the total restricted coal. Without regard to either overlapping areas of

occurrence or type, the total land-use restrictions account for 81 percent of the

total restricted coal.
PAR-102

AVAILABLE COAL RESOURCES

The available resources are estimated to be 1.9 billion tons, or 44 percent of the

original resource (table PAR-3, fig.PAR-15, fig. PAR-16). If only the Type 1

restrictions are included, 48 percent of the original is then available to be mined

(fig. PAR-17). The beds most likely to be mined are the Knobloch, FlowersGoodale and the Sawyer, because of factors such as overall bed thickness,

accessibility, and bed depth.

CONCLUSIONS

Previous studies have estimated Montana's total identified coal resources to be

about 291.6 billion tons (Averitt, 1975), and the strippable subbituminous reserves

to be about 32.0 billion tons (Matson and others, 1973). By itself, the Willow

Crossing quadrangle contains an estimated 4.3 billion tons in original resources,

and the total restricted resource is estimated at 2.4 billion tons (56 percent). The

total available resource is 1.9 billion tons (44 percent) (fig. PAR-15).

The beds most likely to be mined in the near future are the Sawyer, Knobloch, and

Flowers-Goodale, although considerable resources are available from other beds as

well. The Sawyer coal zone averages 11 ft thick in this quadrangle, with 100

percent of the available coal underlying less than 150 ft of overburden. The 21

million available tons (1 percent of total available) are distributed in the Upper

Sawyer, Lower Sawyer, and the Sawyer beds.
PAR-103

The largest single resource is the Knobloch coal bed, which averages over 50 ft

thick in the quadrangle. It contains 1.2 billion tons (65 percent of the total original

resource). A total of 32 percent (399 million tons) underlies less than 150 ft of

overburden, and 64 percent (791 million tons) underlies 150-300 ft.

The Flower-Goodale coal bed averages 11 ft thick and is the next largest resource

at 0.2 billion tons (13 percent of the total available). However, less than 1 percent

(1.3 million tons) underlies less than 150 ft of overburden. An additional 45

percent (114.3 million tons) underlies 150-300 ft of overburden.

Restrictions to mining not included in this study are surface ownership (other than

National Forest lands), mineral ownership, most economic considerations

(recoverability), geologic configurations such as channel cuts, most bed splitting,

and coal-quality parameters. Additionally, the assumption that the subsurface beds

cover the entire quadrangle might not be correct in all cases. For the deepest beds,

very few data points were available, so the results should be considered

preliminary.

Several areas used in this study were checked using manual calculations of area,

thickness, and volume to determine if computer computations produced

comparable results. Results from both methods were within 10 percent of each

other.
PAR-104

REFERENCES CITED

Averitt, P., 1975, Coal resources of the United States, January 1, 1974: U.S.

Geological Survey Bulletin 1412, 131p.

Bass, N.W., 1932, Ashland coal field, Rosebud, Powder River, and Custer

Counties, Montana: U.S. Geological Survey Bulletin 831-B, p. 19-105,

plate 3, scale 1:62,000.

Malde, H.E., and Boyles, J.M., 1976, Maps of alluvial valley floors and strippable

coal in forty-two 7.5-minute quadrangles, Big Horn, Rosebud, and Powder

River Counties, Southeast Montana: U.S. Geological Survey Open-File

Report 76-162.

Matson, R.E., Blumer, J.W., and Wegelin, L.A., 1973, Quality and reserves of

strippable coal, selected deposits, southeastern Montana: Montana Bureau

of Mines and Geology Bulletin 91, 135 p.

McKay, E.J., 1976, Preliminary geologic map and coal sections of the Willow

Crossing quadrangle, Rosebud and Powder River Counties, Montana:

U.S. Geological Survey Miscellaneous Field Studies Map MF-802, scale

1:24,000.

Warren, W.C., 1959, Reconnaissance geology of the Birney-Broadus coal field,

Rosebud and Powder River Counties, Montana: U.S. Geological Survey

Bulletin 1072-J, p. 561-585, plate 19, scale 1:63,360.
PAR-105

Wilde, E.M., in press, Coal resources of the Willow Crossing 7.5-minute

quadrangle, Rosebud and Powder River Counties, Montana: Montana

Bureau of Mines and Geology Open-File Report Number 367.

Wood, G.H., Kehn, T.M., Carter, M.D., and Culbertson, W.C., 1983, Coal

classification system of the U.S. Geological Survey: U.S. Geological

Survey Circular 891, 65 p.
Colstrip E

Colstrip SW

Willow

Crossing

Half

Moon

Hill

Otter

0 10 20 30

Miles

For t Union

Formation

Lignite

Region

Subbituminous

Coal Region

2

1

4 3

Forsyth

Miles City

Broadus

Great Falls

Missoula

Helena

Butte

Billings

12

212

15

90

15

90

90

94

94

90

Figure PAR-10. Coal availability 

study areas in the Montana part 

of the Powder River Basin.

The Willow Crossing 7.5-minute 

quadrangle (number 1 on lower map)

is the subject of this report. Studies in 

areas 2, 3, and 4 are underway 

or proposed.

Montana

 PAR-106
2.6

5.0

4.9

5.8

5.4

8.7

2.9

2.6

2.8

4.9

45.4

4.7

5.7

6.9

2.0

5.1

4.0

9.6

COOK

WALL

PAWNEE

BREWSTER-ARNOLD

CACHE

MACKIN-WALKER

KING

UPPER SAWYER

LOWER SAWYER

A

KNOBLOCH

CALVERT

NANCE

LAY CREEK

FLOWERS-GOODALE

WITHAM

TERRET

STAG

< 20

110-130

150-180

80-140

60-180

40-80

0-60

50-120

0-60

0-60

60-120

10-60

20-80

35-55

15-45

0-30

45-85

25-35

< 20

Tertiar

y

Paleocene

Fort Union

Tongue River

lower middle upper

SYSTEM

SERIES

FORMATION

MEMBER

INFORMAL DIVISION

LITHOLOGY

AVERAGE 

COAL THICKNESS

(in feet)

COAL BED

NAMES

 AVERAGE 

INTERBURDEN

 THICKNESS

(in feet)

Figure PAR-11. Generalized composite stratigraphic section 

for the Willow Creek quadrangle. Rocks between the

coal beds are sandstone, siltstone, shale, claystone, and clinker.

 PAR-107
Willow Crossing quadrangle. These areas 

are not available for surface mining

 because of land-use or technologic restrictions. 

Figure PAR-12. Type 1 restrictions in the 

106°15'W

45°37'30"N

106°7'30"W 

45°30' N

0 1 Mile

 PAR-108

Restrictions

Alluvial valley floors 

Willow Crossing 

National Forest

cemetery
Figure PAR-13. Type 2 restrictions in the 

Willow Crossing quadrangle. These land-use

restrictions encompass both unsuitable areas

and multiple-use areas where mitigation would 

be necessary in order to mine.

 Type 2 Restrictions 

 Roads

 Power lines

 Telephone lines

0 1 Mile Buildings

 PAR-109
Figure PAR-14. This chart shows the percentage of the 

original coal resource that is contained in each mining 

restriction and the percentage that is available. Total 

unavailable coal in the Willow Crossing quadrangle is

2.4 billion tons.

 PAR-110

Other

1%

Buildings

1%

Available

44%

Alluvial valley floors

7%

National Forest

28%

Too-thin

12%

Too-deep

5%

Powerlines

2%
Figure PAR-15. This chart shows the percentage of the total 

available resource contained in each coal bed. The total available 

resource in the Willow Crossing quadrangle is 1.9 billion tons.

 PAR-111

Lay Creek

6%

Terret

6%

Other

1%

Sawyer (incl. Upper 

and Lower)

Stag 1%

1%

Knobloch

65%

Calvert

2%

Nance

5%

Flowers-Goodale

13%
AVAILABLE

1.9 billion tons 

(44%)

MINED-OUT

(less than 1%)

UNAVAILABLE

2.4 billion tons 

(56%)

RESTRICTED

AVAILABLE

Figure PAR-16. Results of the availability study of the Willow 

Crossing quadrangle (using Type 1 and Type 2 restrictions). 

 PAR-112
Available

48%

Technologic 

Restrictions

15%

Land-use 

Restrictions

37%

Original Coal: 4.3 Billion Tons

Land-use 

 Restrictions 37 %

Technologic

 Restrictions 15 %

Available 48 %

Figure PAR-17. Results of Willow Crossing

coal availability study (using Type 1 restrictions).

 PAR-113
Table PAR-2. Classification of restraints to coal mining in the Willow Crossing quadrangle.

Type 1 restrictions are unlikely to be mitigated, while Type 2 restrictions are commonly

TYPE 

TECHNOLOGICAL LAND-USE

1 COAL THICKNESS

1 OVERBURDEN THICKNESS

1 ALLUVIAL VALLEY FLOORS

1 NATIONAL FOREST LANDS

1 CEMETERIES

2 INHABITED BUILDINGS

2 TELEPHONE LINES

2 POWER LINES

2 ROADS

 PAR-114

CATEGORIES

 mitigated so that mining can proceed
COAL BED ORIGINAL MINED-OUT REMAINING RESTRICTED AVAILABLE

Cook 12 0 12 12 0

Wall 131 0 131 131 0

Pawnee 2,268 0 2,268 2,268 0

Brewster-Arnold 9,657 0 9,657 9,657 0

Cache 13,337 0 13,337 13,337 0

Mackin-Walker 35,086 0 35,086 35,086 0

King 10,580 0 10,580 10,312 268

Upper Sawyer 13,415 0 13,415 11,232 2,183

Sawyer 72,689 114 72,575 58,595 13,980

Lower Sawyer 20,383 0 20,383 15,787 4,596

A 55,321 0 55,321 39,403 15,918

Knobloch 1,973,875 0 1,973,875 730,787 1,243,088

Calvert 235,873 0 235,873 197,975 37,898

Nance 346,735 0 346,735 242,067 104,669

Lay Creek 364,679 0 364,679 251,451 113,228

Flowers-Goodale 556,163 0 556,163 303,231 252,932

Witham 91,928 0 91,928 91,928 0

Terret 281,505 0 281,505 173,994 107,511

Stag 237,587 0 237,587 210,785 26,802

TOTAL 4,321,223 114 4,321,110 2,398,037 1,923,073

 PAR-115

Table PAR-3. Summary of tonnages for original, minedout, remaining, restricted, and available coal resources in 

the Willow Crossing quadrangle (in thousands of short 

tons; rounded to whole tons)