Chapter PN

COAL RESOURCES, POWDER RIVER BASIN

By M.S. Ellis,1 G.L. Gunther,2 A.M. Ochs,2 S.B. Roberts,1 E.M. Wilde3,

J.H. Schuenemeyer,

1

 H.C. Power,

4

 G.D. Stricker,1 and Dorsey Blake1

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

1 U.S. Geological Survey

2 Consultant, U.S. Geological Survey, Denver, Colorado

3

 Montana Bureau of Mines and Geology, Butte, Montana

4

 University of Delaware, Newark, Delaware
PN-ii

Contents

Coal Resources—Wyodak-Anderson Coal Zone, Powder River Basin, Wyoming

and Montana........................................................................................................PN-1

Wyodak-Anderson Coal Zone Resource Estimates—An Overview .............PN-1

Wyodak-Anderson Coal Zone Coal Resources .............................................PN-2

Confidence Limits for Wyodak-Anderson Coal Zone Coal Resources.........PN-4

References Cited .................................................................................................PN-6

Figures

PN-1 Location of 7.5-minute quadrangle maps in the Wyodak-Anderson study

limit.

PN-2 Federal coal and surface ownership in the Powder River Basin.

PN-3 Wyodak-Anderson net coal isopach map.

PN-4 Wyodak-Anderson overburden isopach map.

PN-5 Wyodak-Anderson clinker, mine and lease areas, and resource area.

Tables

PN-1 Wyodak-Anderson coal resources in the Powder River Basin reported by

State, county, overburden thickness, net coal thickness, and reliability

categories

PN-2 Wyodak-Anderson coal resources in the Powder River Basin reported by

7.5-minute quadrangle map area
PN-iii

Tables—continued

PN-3 Wyodak-Anderson coal resources in the Powder River Basin reported by

State and by Federal coal and Federal surface ownership

PN-4 Key to 7.5-minute quadrangle maps in the Wyodak-Anderson study limit

PN-5 Data used for computation of confidence limits intervals within reliability

categories for Wyodak-Anderson coal resources

PN-6 Estimates of uncertainty with measurement error for Wyodak-Anderson

coal resources
PN-1

COAL RESOURCES—WYODAK-ANDERSON COAL ZONE,

POWDER RIVER BASIN, WYOMING AND MONTANA

WYODAK-ANDERSON COAL ZONE RESOURCE ESTIMATES—AN

OVERVIEW

• Coal resources are calculated using the specific gravity of the coal calculated

from apparent coal rank, which is the weight of coal per unit volume, net coal

thickness, and areal extent of the coal.

• Resource tables for the Wyodak-Anderson coal zone in the Powder River Basin

include coal and overburden thickness categories from Wood and others (1983),

which are based on apparent coal rank. Additional categories have been added

to provide more detail. Resources are also reported by State, county, Federal

coal and surface ownership, and 7.5-minute quadrangle.

• Following USGS published guidelines (Wood and others, 1983) coal resource

estimates are divided into measured, indicated, and inferred categories

according to relative abundance and reliability of data.

• Where data are widely spaced a hypothetical resource may be extrapolated.

• Measured resources are tonnage estimates of coal in the coal zone within a

radius of 0.25 mi of a control point where the net thickness of coal is measured.

• Indicated resources are tonnage estimates of coal that is within a radius of 0.25-

0.75 mi of a control point where the net thickness of the coal is measured.
PN-2

• Inferred resources are tonnage estimates of coal that is within a radius of 0.75-3

mi of a control point where the net thickness of the coal is measured.

• Hypothetical resources are tonnage estimates of coal that is beyond a radius of 3

mi of a control point where the net thickness of coal is measured.

• These resource categories assume a high to low degree of geologic certainty. A

statistical method, which measures levels of uncertainty (confidence limits) for

the Wyodak-Anderson resource estimates in the Powder River Basin, is also

included in this study.

• Resource estimates are reported in millions of short tons with two significant

figures.

WYODAK-ANDERSON COAL ZONE COAL RESOURCES

The lateral extent (study limit) of the Wyodak-Anderson coal zone is based on

published geologic maps by Kent and Berlage (1980), Bryson and Bass (1973),

Robinson and Culbertson (1984), Warren (1959), and Baker (1929). The study

limit was generalized in some areas to include small areas of Wyodak-Anderson

coal outside of the main boundary. The contact of Cretaceous and Tertiary rocks

(Love and Christiansen, 1985; Ross and others, 1955) was used for a boundary in

some areas where more detailed geologic and coal outcrop maps were not

available. The entire study area is about 5,972,000 acres (2,416,786 hectares) in

size.

Wyodak-Anderson coal resources in the Powder River Basin of Wyoming and

Montana were calculated using several software packages and custom programs.

Details of the methodology used are given in Ellis and others (1999, in press).
PN-3

To calculate Wyodak-Anderson coal resources data was compiled in a StratiFact*

(GRG Corporation, 1996) relational database. The coal beds in the WyodakAnderson coal zone, including the Anderson, Dietz, Canyon, Monarch, Werner,

Wyodak, Smith, Swartz, Sussex, School, and Badger coal beds (see an explanation

of coal-bed nomenclature in the chapter on Fort Union coal in the Powder River

Basin (chapter PS), were correlated in the database. A custom program was used

to calculate the net coal thickness at each data point (drill hole or measured

section) location.

The net coal thickness and overburden were gridded, and isopach maps were

produced using EarthVision* software (Dynamic Graphics, Inc., 1997). The grid

for the coal thickness was made using an isopach grid option (special handling of 0

values and terminated data) and 300 x 300-meter grid spacing.

The spatial parameters for querying coal resources (for example, 7.5-minute

quadrangle (fig. PN-1) map area (U.S. Geological Survey National Mapping

Division unpublished data, undated), Federal coal and surface ownership (fig. PN2) (Biewick and others, 1998), and reliability, coal thickness (fig. PN-3), and

overburden (fig. PN-4) categories) were created on individual layers as

ARC/INFO* (ESRI, 1998a) polygon coverages. The coverages were unioned to

make one polygon coverage with many attributes for each polygon. The polygons

in the union coverage were edited in ARC/INFO* and ArcView* (ESRI, 1998b).

Coal resources were calculated using the EarthVision* (EV) volumetrics tool,

which calculates tonnages in each union coverage polygon using the net coal

thickness grid, the area of each polygon, and a conversion factor of 1,770 short

tons per acre-ft for subbituminous rank coal (Wood and others, 1983). Data from
PN-4

the EV volumetrics report and the union coverage polygon attribute table were

combined in Excel* (Microsoft, 1997) spreadsheet software. Data for polygons

containing Wyodak-Anderson clinker (fig. PN-5) (Kanizay, S.P., 1978; Heffern

and others, 1993; Boyd and others, 1997; and Heffern unpublished data, undated),

Wyodak-Anderson mine and lease areas (fig. PN-5) (Bureau of Land Management,

1996; Kennecott Energy and others, undated; and Dunrud and Osterwald, 1980), or

areas of net coal less than 2.5 ft thick were deleted from the data set. Lease areas

may include public and/or state leases in addition to Federal leases. Resource

tables were created using data from the remaining polygons (tables PN-1, PN-2,

and PN-3). The final resource area (fig. PN-5) (area that met all coal resource

criteria) was about 5,414,000 acres (2,190,971 hectares) in area.

*Commercial software package.

CONFIDENCE LIMITS FOR WYODAK-ANDERSON COAL ZONE

COAL RESOURCES

A confidence interval is a statistic designed to capture uncertainty associated with

a point value estimate. In this study we computed 90-percent confidence intervals

on the volume (total resource in millions of short tons) of coal in the WyodakAnderson coal zone in the measured, indicated, inferred, and hypothetical

categories.

The three main potential sources of error that might bias the confidence intervals

are preferential sampling, measurement errors, and model fitting. The probabilistic

interpretation of a confidence interval is based upon a random sample, which does

not apply in this situation, because there is preferential sampling in those areas

deemed to be minable. Measurement error can be caused by an error in recording
PN-5

the coal bed thickness or in the definition of coverage areas. Modeling fitting

variability and bias result from the choice of models and fitting procedures.

Confidence limits for coal resources of the Wyodak-Anderson coal zone in the

Powder River Basin were calculated by J.H. Schuenemeyer and H.C. Power. The

data set that they used contained net coal measurements from 4,462 locations. This

data set included drill hole or measured section data for locations that contained

Wyodak-Anderson coal (no 0 values) and data that were representative of the

entire coal zone (no terminated holes).

The confidence limits were derived through a complex series of steps. These steps

included modeling coal thickness trends and removing the coal thickness trends

using a nonparametric regression algorithm called loess (with span=0.5), using

residual thickness to compute a semivariogram, and fitting the semivariogram to an

exponential model. Parameter estimates were sill=529.75 ft2, nugget=212.04 ft2,

and range=2.357 miles. Standard deviations of coal thickness were obtained from

the semivariogram model. Differences in point densities were compensated for by

calculating sample size, called a pseudo n, within each reliability category and

calculating the variability of volume for each of the reliability categories.

Volumes of Wyodak-Anderson coal were then calculated at a 90-percent

confidence interval with measurement error. Some of the parameters used and

results of the confidence interval calculations are shown in tables PN-5 and PN-6.

A detailed description of the methodology used is given in Schuenemeyer and

Power (in press) and in Ellis and others (1999, in press).
PN-6

REFERENCES CITED

Baker, A.A., 1929, Sheridan coal field, northward extension: U.S. Geological

Survey Bulletin 806-B, p. 15-67.

Biewick, L.R.H., Urbanowski, S.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 98-108, coverage scale

1:100,000.

Boyd, C.S., and Van Ploeg, A.J., 1997, Geologic map of the Gillette 30' x 60'

quadrangle, Campbell, Crook, and Weston Counties, northeastern Wyoming:

Wyoming State Geological Survey Map Series 49, scale 1:100,000.

Bryson, R.P., and Bass, N.W., 1973, Geology of the Moorhead coal field, Powder

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

Bulletin 1338, 116 p.

Bureau of Land Management, 1996, Powder River Basin Coal Production—1995

(N. Braz, C. Gaskill, and R. Nelson compilers): U.S. Department of the

Interior, Bureau of Land Management, Casper, Wyoming, file

D\drawings\wo-map.dwg.
PN-7

Dunrud, C.R., and Osterwald, F.W., 1980, Effects of coal mine subsidence in the

Sheridan, Wyoming area: U.S. Geological Survey Professional Paper 1164,

p.7, figure 4.

Dynamic Graphics, Inc., 1997, EarthVision, v.4: Dynamic Graphics, Inc., 1015

Atlantic Ave., Alameda, CA 94501.

Ellis, M.S., 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 coal resources of the Wyodak-Anderson coal zone, Powder River Basin,

Wyoming and Montana: U.S. Geological Survey Open-File Report 98-789A,

49 p. (digital version available at http:greenwood.cr.usgs.gov/pub/open-filereports/ofr-98-0789-a/).

Ellis, M.S., Gunther, G.L., Flores, R.M., Stricker, G.D., Ochs, A.M., and

Schuenemeyer, J.H., in press, Preliminary report on the methodology for

calculating coal resources in the Wyodak-Anderson coal zone, Powder River

Basin, Wyoming and Montana: U.S. Geological Survey Open-File Report 98-

789B.

ESRI-Environmental Systems Research Institute, Inc., 1998a, ARC/INFO, v. 7.1.1:

Environmental Systems Research Institute, Inc., 380 New York Street,

Redlands, CA 92373, USA.

_____ 1998b, ArcView, v.3.0a: Environmental Systems Research Institute, Inc.,

380 New York Street, Redlands, CA 92373, USA.
PN-8

GRG Corporation, 1996, StratiFact, relational database software, v. 4.5: GRG

Corporation, 4175 Harlan Street, Wheatridge, CO 80033-5150, USA.

Heffern, E.L., Coates, D.A., Whiteman, Jason, and Ellis, M.S., 1993, Geologic

map showing distribution of clinker in the Tertiary Fort Union and Wasatch

Formations, Northern Powder River Basin, Montana, U.S. Geological

Survey Coal Investigations Map C-142, scale 1:175,000.

Kanizay, S.P., 1978, Preliminary geologic map of the Sheridan area, northwestern

Powder River Basin, Wyoming, U.S. Geological Survey Miscellaneous

Field Studies Map MF-1043, scale 1:50,000.

Kennecott Energy, and Peter Kiewit and Sons, undated, Maps showing lease

boundaries, extent of mining, and areas planned for future mining in the

Decker Coal Mine: scales 1:48,000 and 1:24,000.

Kent, B.H., and Berlage, L.J., 1980, Geologic map of the Recluse 1 x 2 degree

quadrangle, Campbell and Crook Counties, Wyoming: U.S. Geological

Survey Coal Investigations Map C-81-D, scale 1:100,000.

Love, J.D., and Christiansen, A.C., 1985, Geologic map of Wyoming: U.S.

Geological Survey, scale 1:500,000.

Microsoft, 1997, Excel spreadsheet software, v. Office 97: Microsoft Corporation,

1 Microsoft Way, Redman, WA 98052.

Robinson, L.N., and Culbertson, W.C., 1984, Map showing isopachs of coal and

overburden of the Canyon coal bed, Birney 30’ x 60’ quadrangle, Big Horn
PN-9

and Rosebud Counties, Montana: U.S. Geological Survey Coal

Investigations Map C-96-B, scale 1:100,000.

Ross, C.P., Andrews, D.A., and Witkind, I.J., 1955, Geologic map of Montana:

U.S. Geological Survey and Montana Bureau of Mines and Geology, scale

1:500,000.

Schuenemeyer, J. H., and Power H., in press, Uncertainty estimation for resource

assessment—An application to coal: Mathematical Geology.

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.

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, 65 p.
Figure PN-1. Location of 7.5-minute quadrangle maps in the WyodakAnderson study limit.

Wyodak-Anderson

Study Limit

22 23

59 60 61 62 63 64 65 66 67 68 69 70 71 72

73 74 75 76 77 78 79 80 81 82 83 84 85 86

100 101 102103 104 105 106 107 108 109 110 111112

113 114 115 116 117118 119120 121 122 123 124 125

126 127128129 130 131 132 133 134 135 136 137 138 139

140 141 142 143 144 145 146 147148 149 150 151

152

16 17

19

18

26 27 28 29

14 15

24 25

13

44 45 46 47 48 49 50

8 9 10 11 12

20 21

51 52 53 54 55 56 57 58

153154 155156 157158 159 160 161162 163

164 165 166 167 168 169 170 171 172 173 174 175

176 177178 179 180 181 182 183 184 185 186 187

188 189 190 191 192 193 194 195 196

197 198 199 204

205 206 207 208 209 210 211

212213 214 215 216 217

200 201 202 203

225 226 227 224

218 219 220 221 222 223

Miles

Kilometers

0 20 40

0 40

107 106 105

45

44

43

o

o

o

o o o

 Powder 

River 

Basin 

Boundary

1 2 3 4 5 6 7

30 31 32 33 34 35 36 37 38 39 40 41 42 43

87 88 89 90 91 92 93 94 95 96 97 98 99
Federal coal = Subsurface

Federal management of all minerals, 

coal only, or oil, gas, and coal

Federal surface = Federal surface

ownership

Federal coal and Federal surface

Federal coal, but no Federal surface

No Federal coal, but Federal surface

No Federal coal or Federal surface

Figure PN-2. Federal coal and surface ownership in the Powder River Basin.

Wyodak-Anderson

Study Limit

107 

45 

44 

43 

106 

o

o o

o

o

105 o

46 o

Montana

Wyoming
Figure PN-3. Wyodak-Anderson net coal isopach map.

Net coal 

thickness (ft)

Powder River

 Basin 

Boundary

Miles

Kilometers

0 10 20 30 40

0 20 40 60

WyodakAnderson

Study Limit

Rosebud

Johnson

Powder River

Natrona

Campbell

Converse

Sheridan

Big 

Horn

107 

45 

44 

43 

106 

o

o o

o

o

Wyoming

Northern Cheyenne 

and Crow Indian 

Reservations (part) 

County lines

2.5

5

10

20

30

40 

50

75

100

150

200

250

0

Montana
Figure PN-4. Wyodak-Anderson overburden isopach map.

Overburden 

thickness (ft)

Miles

Kilometers

0 10 20 30 40

0 20 40 60

WyodakAnderson

Study Limit

Rosebud

Johnson

Powder River

Natrona

Campbell

Converse

Sheridan

Big 

Horn

107 

45 

44 

43 

106 

Powder River

 Basin 

Boundary

Montana

Wyoming

o

o o

o

o

Northern Cheyenne 

and Crow Indian 

Reservations (part)

100

200

300

400

500

1000

2000

County lines

0
Miles

Kilometers

Powder River Basin boundary

County lines

State line

Wyodak-Anderson mines and 

lease areas

Wyodak-Anderson

clinker

Montana

Wyoming

Montana

Wyoming

Johnson

Sheridan

Big Horn

Powder River

Campbell

Natrona Converse

Washakie

Carter

Niobrara

Weston

Fallon

Treasure

Crook

Johnson

Sheridan

Powder River

Campbell

Natrona Converse

Carter

Niobrara

Weston

Fallon

e

Crook

0 20 40 60

0 40 80

46

45

44

43

Resource area (Area meeting 

resource criteria--does not include 

areas with mines, leases, clinker, 

or net coal < 2.5 ft thick)

 PN-5. Wyodak-Anderson clinker, mine and lease areas, and resource 

owder River Basin, Wyoming.

Index Map Showing Area

Included in Resource Calculations

Northern Cheyenne and Crow 

Indian Reservations (part)

Montana

Wyoming
Table PN-1. Wyodak-Anderson coal resources in the Powder River Basin, Wyoming and Montana, reported by

State, county, overburden thickness (fig. PN-4), net coal thickness (fig. PN-3), and reliability categories.

Resources are shown in millions of short tons (MST) with two significant figures. Zeros (0) indicate that no coal

resources were calculated within those categories. The table does not include resources in Wyodak-Anderson mine

or lease areas, areas containing Wyodak-Anderson clinker, or areas where coal is less than 2.5 ft thick (fig. PN-5).

Resource numbers will not sum to match totals due to independent rounding

State County Overburden Net Reliability categories (distance from control point) Total

thickness coal

thickness

Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

Montana BIG HORN 0-100 ft 2.5-5 ft 0 0.35 2.3 0 2.7

5-10 ft 0.26 0.20 10 0 10

10-20 ft 21 54 79 0 150

20-40 ft 120 420 240 0 780

>40 ft 650 2,100 1,100 0 3,900

0-100 ft total 790 2,600 1,500 0 4,900

100-200 ft 2.5-5 ft 0 0.29 0.76 0 1.0

5-10 ft 0 1.9 6.6 0 8.4

10-20 ft 11 41 36 0 89

20-40 ft 92 350 220 0 670

>40 ft 1,000 3,200 1,400 0 5,700

100-200 ft total 1,100 3,600 1,700 0 6,400

200-500 ft 2.5-5 ft 0.14 0.40 0.076 0 0.61

5-10 ft 0 4.1 0.55 0 4.6

10-20 ft 2.9 28 64 0 95

20-40 ft 27 140 430 0 600

>40 ft 1,500 7,300 5,100 0 14,000

200-500 ft total 1,500 7,500 5,600 0 15,000

>500 ft 2.5-5 ft 0 0.25 0 0 0.25

5-10 ft 0.75 1.2 0 0 2.0

10-20 ft 0.95 0.15 0 0 1.1

20-40 ft 3.4 1.1 0 0 4.5

>40 ft 190 1,100 1,400 0 2,700

>500 ft total 200 1,100 1,400 0 2,700

BIG HORN total 3,600 15,000 10,000 0 29,000
Table PN-1. Wyodak-Anderson coal resources—continued

State County Overburden Net Reliability categories (distance from control point) Total

thickness coal

thickness

Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

Montana POWDER RIVER 0-100 ft 2.5-5 ft 0.42 1.0 19 4.1 25

5-10 ft 2.3 15 110 13 140

10-20 ft 59 260 450 32 800

20-40 ft 220 930 670 93 1,900

>40 ft 200 730 760 40 1,700

0-100 ft total 490 1,900 2,000 180 4,600

100-200 ft 2.5-5 ft 0 0 3.8 0.52 4.3

5-10 ft 0.55 6.6 39 4.3 51

10-20 ft 2.0 47 140 14 200

20-40 ft 30 180 370 50 630

>40 ft 130 730 730 7.1 1,600

100-200 ft total 160 970 1,300 75 2,500

200-500 ft 2.5-5 ft 0 0 0.7 0 0.70

5-10 ft 0 2.0 8.9 1.4 12

10-20 ft 0 3.4 27 9.2 40

20-40 ft 9.5 88 180 24 300

>40 ft 200 1,100 2,200 0 3,500

200-500 ft total 210 1,100 2,400 34 3,800

>500 ft >40 ft 0 0.53 0 0 0.53

>500 ft total 0 0.53 0 0 0.53

POWDER RIVER total 860 4,100 5,700 290 11,000

ROSEBUD 0-100 ft 2.5-5 ft 0.38 0.47 6.3 1.5 8.6

5-10 ft 11 31 66 30 140

20-40 ft 29 120 180 0 320

>40 ft 62 330 220 0 610

0-100 ft total 120 590 610 56 1,400

100-200 ft 2.5-5 ft 0 0.46 4.2 0.094 4.8

5-10 ft 2.4 15 24 8.3 50

10-20 ft 7.2 34 79 16 140

20-40 ft 9.4 89 110 0 210

>40 ft 75 340 340 0 750

100-200 ft total 94 470 560 25 1,200
Table PN-1. Wyodak-Anderson coal resources—continued

State County Overburden Net Reliability categories (distance from control point) Total

thickness coal

thickness

Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

Montana ROSEBUD 200-500 ft 2.5-5 ft 0 0 0.61 0 0.61

5-10 ft 0.097 6.2 9.6 4.0 20

10-20 ft 0 20 61 7.0 89

20-40 ft 3.4 3.9 19 0 26

>40 ft 11 82 27 0 120

200-500 ft total 15 110 120 11 250

ROSEBUD total 230 1,200 1,300 92 2,800

Montana total 4,700 20,000 17,000 380 42,000

Wyoming CAMPBELL 0-100 ft 2.5-5 ft 3.6 9.6 57 12 83

5-10 ft 24 36 83 33 180

10-20 ft 140 140 300 32 620

20-40 ft 380 780 1,100 0 2,300

>40 ft 1,900 4,400 2,900 420 9,600

0-100 ft total 2,500 5,300 4,500 490 13,000

100-200 ft 2.5-5 ft 1.1 5.4 14 0.58 21

5-10 ft 6.9 32 31 5.6 76

10-20 ft 55 180 140 2.7 380

20-40 ft 290 880 660 3.3 1,800

>40 ft 3,200 6,800 1,800 0 12,000

100-200 ft total 3,500 7,900 2,600 12 14,000

200-500 ft 2.5-5 ft 3.5 9.5 5.3 0.73 19

5-10 ft 31 49 23 0.96 100

10-20 ft 120 360 200 0 680

20-40 ft 540 1,400 830 0 2,800

>40 ft 9,300 29,000 11,000 20 49,000

200-500 ft total 10,000 30,000 12,000 22 52,000
Table PN-1. Wyodak-Anderson coal resources—continued

State County Overburden Net Reliability categories (distance from control point) Total

thickness coal

thickness

Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

Wyoming CAMPBELL >500 ft 2.5-5 ft 0.25 3.8 9.0 0 13

5-10 ft 2.3 18 59 0 79

10-20 ft 1.3 37 160 0 200

20-40 ft 120 390 1,400 49 1900

>40 ft 13,000 57,000 120,000 6,900 200,000

>500 ft total 13,000 58,000 130,000 6,900 200,000

CAMPBELL total 29,000 100,000 140,000 7,500 280,000

CONVERSE 0-100 ft 2.5-5 ft 0.10 0.36 1.8 190 200

5-10 ft 1.6 21 80 620 720

10-20 ft 41 280 570 380 1,300

20-40 ft 92 440 650 22 1,200

>40 ft 46 100 280 0 430

0-100 ft total 180 850 1,600 1,200 3,800

100-200 ft 2.5-5 ft 0.33 1.1 15 30 46

5-10 ft 1.4 17 89 120 230

10-20 ft 47 230 370 54 700

20-40 ft 76 360 440 88 960

>40 ft 65 270 100 0 440

100-200 ft total 190 880 1,000 300 2,400

200-500 ft 2.5-5 ft 1.6 7.3 92 92 190

5-10 ft 20 97 290 710 1,100

10-20 ft 70 350 960 530 1,900

20-40 ft 41 260 730 230 1,200

>40 ft 150 480 230 0 860

200-500 ft total 280 1,200 2,300 1,600 5,300

>500 ft 2.5-5 ft 2.3 14 16 2.4 35

5-10 ft 20 120 430 430 1,000

10-20 ft 22 150 590 1,000 1,800

20-40 ft 1.3 20 350 340 710

>40 ft 0 0 190 0 190

>500 ft total 45 300 1,600 1,800 3,700

CONVERSE total 700 3,200 6,500 4,900 15,000
Table PN-1. Wyodak-Anderson coal resources—continued

State County Overburden Net Reliability categories (distance from control point) Total

thickness coal

thickness

Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

Wyoming JOHNSON 0-100 ft 2.5-5 ft 0 2.3 3.3 10 16

5-10 ft 0 5.6 13 9.9 28

10-20 ft 5.4 15 52 26 99

20-40 ft 33 62 42 10 150

>40 ft 32 82 150 0 270

0-100 ft total 71 170 260 56 560

100-200 ft 2.5-5 ft 0 2.3 2.0 10 15

5-10 ft 0 4.0 4.3 12 20

10-20 ft 2.0 5.3 17 8.5 33

20-40 ft 9.2 42 100 7.9 160

>40 ft 30 130 220 0 380

100-200 ft total 41 180 350 39 610

200-500 ft 2.5-5 ft 0 2.9 4.7 36 44

5-10 ft 0.036 7.0 17 85 110

10-20 ft 5.6 25 74 38 140

20-40 ft 23 72 440 23 560

>40 ft 32 310 1,300 16 1,600

200-500 ft total 61 410 1,800 200 2,500

>500 ft 2.5-5 ft 1.6 6.6 33 88 130

5-10 ft 5.7 49 500 420 970

10-20 ft 20 130 1,500 1,200 2,900

20-40 ft 85 620 5,000 3,200 9,000

>40 ft 6,800 32,000 96,000 7,700 140,000

>500 ft total 6,900 33,000 100,000 13,000 160,000

JOHNSON total 7,100 34,000 110,000 13,000 160,000

SHERIDAN 0-100 ft 2.5-5 ft 0.053 8.2 2.2 22 33

5-10 ft 12 40 11 37 100

10-20 ft 36 170 120 40 370

20-40 ft 45 230 420 5.5 700

>40 ft 100 350 740 0 1,200

0-100 ft total 200 790 1,300 110 2,400
Table PN-1. Wyodak-Anderson coal resources—continued

State County Overburden Net Reliability categories (distance from control point) Total

thickness coal

thickness

Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

Wyoming SHERIDAN 100-200 ft 2.5-5 ft 1.4 4.1 2.0 15 23

5-10 ft 4.6 11 14 51 81

10-20 ft 22 62 90 54 230

20-40 ft 98 410 660 46 1,200

>40 ft 290 620 850 81 1,800

100-200 ft total 420 1,100 1,600 250 3,400

200-500 ft 2.5-5 ft 1.4 8.1 7.6 16 33

5-10 ft 6.7 23 20 49 98

10-20 ft 34 160 530 180 910

20-40 ft 260 1,100 3,400 370 5,100

>40 ft 840 3,700 6,500 220 11,000

200-500 ft total 1,100 4,900 11,000 840 17,000

>500 ft 2.5-5 ft 0.51 3.0 4.7 87 95

5-10 ft 4.9 33 73 580 690

10-20 ft 23 140 760 1,600 2,500

20-40 ft 120 790 7,800 5,200 14,000

>40 ft 310 1,800 8,600 1,300 12,000

>500 ft total 450 2,700 17,000 8,700 29,000

SHERIDAN total 2,200 9,600 31,000 9,900 52,000

Wyoming total 39,000 150,000 290,000 35,000 510,000

Grand total (MST) 44,000 170,000 300,000 36,000 550,000
Table PN-2. Wyodak-Anderson coal resources in the Powder River Basin, Wyoming and Montana, reported by

State and by 7.5-minute quadrangle map area (see location map (fig. PN-1) and quadrangle key (table PN-4)).

Resources are shown in millions of short tons (MST) with 2 significant figures. The table does not include

resources in mine or lease areas, areas containing Wyodak-Anderson clinker, or areas where coal is less than 2.5 ft

thick (fig. PN-5). Resource numbers will not sum to match totals due to independent rounding

State 7.5-minute quadrangle map Total (MST) State 7.5-minute quadrangle map Total (MST)

Montana ACME 160 Montana HOLMES RANCH 2,700

BAR N DRAW 150 KING MOUNTAIN 22

BAR V RANCH 320 KIRBY 1,700

BAR V RANCH NE 740 LACEY GULCH 1,100

BEAR CREEK SCHOOL 2,700 MONARCH 1.2

BIRNEY 74 MOORHEAD 43

BAY HORSE 2.1 O T O RANCH 140

BIRNEY DAY SCHOOL 2.2 OTTER 630

BIRNEY SW 130 PEARL SCHOOL 4,600

BLACK DRAW 51 PHILLIPS BUTTE 600

BLOOM CREEK 65 PINE BUTTE SCHOOL 3,400

BOX ELDER DRAW 89 POKER JIM BUTTE 1,000

BRADSHAW CREEK 1,100 QUIETUS 3,500

BROWNS MOUNTAIN 60 REANUS CONE 360

CABIN CREEK NE 150 ROUNDUP DRAW 110

CABIN CREEK NW 150 SAYLE 1,100

CEDAR CANYON 130 SAYLE HALL 2,600

CLUBFOOT CREEK 2.4 SONNETTE 46

COOK CREEK BUTTE 81 SPRING CREEK RANCH 47

DECKER 1,900 SPRING GULCH 790

FORKS RANCH 2,700 STROUD CREEK 1,000

FORT HOWES 160 TAINTOR DESERT 1,100

GOODSPEED BUTTE 43 THREE BAR RANCH 39

GREEN CREEK 56 THREEMILE BUTTES 3.4

HALF MOON HILL 1,600 TONGUE RIVER DAM 250

HAMILTON DRAW 2,400 Montana total 42,000

HODSDON FLATS 210
Table PN-2. Wyodak-Anderson coal resources—continued

State 7.5-minute quadrangle map Total (MST) State 7.5-minute quadrangle map Total (MST)

Wyoming ACME 2,700 Wyoming CALF CREEK 3,400

ALTA CREEK 6.0 CARR DRAW 7,800

ANTELOPE DRAW 59 CEDAR CANYON 2,700

APPEL BUTTE 5,000 CLEARMONT 1,500

ARPAN BUTTE 2,800 COAL BANK DRAW 64

ARTESIAN DRAW 4,600 COAL DRAW NORTH 1,200

ARVADA 2,200 COAL DRAW SOUTH 230

ARVADA NE 3,700 COAL HILL 1,300

BAKER SPRING 4,200 COON TRACK CREEK 51

BANNER 93 CORRAL CREEK 1,600

BAR N DRAW 2,900 COYOTE DRAW 1,400

BAY HORSE 0.25 CRAZY WOMAN RANCH 2,700

BEAR CREEK 680 CROTON 6,200

BEAR DRAW 6,700 DEAD HORSE LAKE 1,300

BEAUCHAMP RESERVOIR 29 DOUBLE TANKS 7,500

BETTY RESERVOIR 1,700 DRY CREEK RESERVOIR 570

BIG HORN 520 DRY FORK RANCH 7,300

BLACK DRAW 1,200 DUGOUT CREEK NORTH 840

BOBBY DRAW 67 DUGOUT CREEK SOUTH 2.7

BOGIE DRAW 6,900 EAGLE ROCK 4,200

BOON 3,400 ECHETA 4,900

BOWMAN FLAT 7,000 ELAINE DRAW 620

BOX ELDER DRAW 1,200 FATS DRAW 7,300

BROWN RANCH 750 FAWN DRAW 2,600

BUFFALO 1600 FIGURE 8 RESERVOIR 670

BUFFALO NE 3,300 FLOATE DRAW 5,900

BUFFALO RUN CREEK 880 FLY DRAW 250

BUFFALO SE 3,900 FORT RENO 3,600

CABIN CREEK NE 1,400 FORT RENO SE 7,600

CABIN CREEK NW 2,500 FORTIN DRAW 390

CABIN CREEK SE 2,400 FOUR BAR J RANCH 4,600
Table PN-2. Wyodak-Anderson coal resources—continued

State 7.5-minute quadrangle map Total (MST) State 7.5-minute quadrangle map Total (MST)

Wyoming FOURMILE RESERVOIR 2,000 Wyoming LEITER 1,600

FREDRICK DRAW 4,500 LEUENBERGER RANCH 480

GARDNER GULCH 2,000 LINCH 390

GILBERT LAKE 80 LITTLE BEAR CREEK 1.2

GILLAM DRAW EAST 1.1 LITTLE THUNDER RESERVOIR 5,700

GILLETTE EAST 2,400 LIVINGSTON DRAW 5,700

GILLETTE WEST 4,900 MACKEN DRAW 670

GLENROCK NW 96 MARSH DRAW 330

GREASEWOOD RESERVOIR 4,700 MITCHELL DRAW 6,000

GUMBO HILL 390 MONARCH 690

HILIGHT 3,500 MOORHEAD 1.8

HOE RANCH 4,600 MORGAN DRAW 9,700

HOLDUP HOLLOW 770 MOYER SPRINGS 530

HOMESTEAD DRAW 480 NEGRO BUTTE 9,200

HOMESTEAD DRAW SW 2,700 NEIL BUTTE 2,200

HORSE HILL 1,100 NORTH BUTTE 8,000

HOUSE CREEK 4,700 NORTH RIDGE 78

HULTZ DRAW 240 O T O RANCH 2,200

HYLTON RANCH 590 OLIVER DRAW 36

JEFFERS DRAW 4,500 OPEN A RANCH 430

JEWELL DRAW 3,900 ORIVA 4,400

JONES DRAW 1,700 ORIVA NW 5,100

JULIO DRAW 2,800 PATSY DRAW 33

JUNIPER DRAW 7,900 PEPSSON DRAW 5,500

KAYCEE NE 110 PINE GULCH 5,100

KLINE DRAW 3,200 PINE TREE 4,200

LAKE DE SMET EAST 2,200 PINEY CANYON NW 110

LAKE DE SMET WEST 380 PINEY CANYON SW 520

LAREY DRAW 3,800 PITCH DRAW 1,100

LARIAT 5,200 PLEASANTDALE 5,300

LASKIE DRAW 9,500 PLOESSERS DRAW 5,700
Table PN-2. Wyodak-Anderson coal resources—continued

State 7.5-minute quadrangle map Total (MST) State 7.5-minute quadrangle map Total (MST)

Wyoming PROVENCE RANCH 2,000 Wyoming SOUTH BUTTE 5,300

PURDY RESERVOIR 35 SOUTH FORK RESERVOIR 900

RANCHESTER 180 SPOTTED HORSE 5,400

RATTLESNAKE DRAW 4,000 STORY 7.5

RAWHIDE SCHOOL 4,300 SUICIDE HILL 1,100

RECLUSE 3,400 SUSSEX 1,900

RED HILL 630 T A RANCH 310

RENO FLATS 4,300 T A RANCH NE 1,400

RENO JUNCTION 6,000 TAYLOR RANCH 2,600

RENO RESERVOIR 3,100 TECKLA 3,700

RESERVOIR CREEK 2,600 TECKLA SW 4,800

ROCKY BUTTE 100 THE GAP 3,800

ROCKY BUTTE GULCH 6,200 THE GAP SW 3,200

ROCKY BUTTE SW 240 THE NIPPLE 7,300

ROLLING PIN RANCH 7,000 THOMPSON DRAW 720

ROSS 770 THREE BAR RANCH 1.2

ROSS FLAT 1,200 THREEMILE CREEK RESERVOIR 6,400

ROUGH CREEK 1,500 TRABING 450

ROUNDUP DRAW 1,500 TRUMAN DRAW 6,200

S R SPRINGS 1,300 TURNERCREST 2,900

SADDLE HORSE BUTTE 370 TWENTYMILE BUTTE 4,600

SAVAGETON 5,600 UCROSS 2,700

SAWMILL CANYON 33 ULM 710

SCAPER RESERVOIR 5,900 VERONA 630

SCOTT DAM 5,600 WAGS PINNACLE 5,800

SEVEN L CREEK EAST 59 WESTON SW 100

SHERIDAN 1,100 WHIPPLE HOLLOW 400

SHULER DRAW 1,500 WHITE TAIL BUTTE 1,500

SOLDIER CREEK 1,100 WILDCAT 4,100

SOMERVILLE FLATS EAST 6,800 WYARNO 2,700

SOMERVILLE FLATS WEST 7,300 Wyoming total 510,000

Grand total (MST) 550,000
Table PN-3. Wyodak-Anderson coal resources in the Powder River Basin, Wyoming and Montana, reported by

State and by Federal coal and surface ownership (fig. PN-2) (Biewick and others, 1998). Resources are shown in

millions of short tons (MST) with 2 significant figures. The table does not include resources in mine or lease areas,

areas containing Wyodak-Anderson clinker, or areas where coal is less than 2.5 ft thick (fig. PN-5). Resource

numbers will not sum to match totals due to independent rounding

State Federal ownership Total (MST)

Montana No Federal coal or surface ownership 3,900

No Federal coal ownership, but Federal surface ownership 2.9

Federal coal ownership, but no Federal surface ownership 32,000

Federal coal and surface ownership 6,700

Montana total 42,000

Wyoming No Federal coal or surface ownership 64,000

No Federal coal ownership, but Federal surface ownership 1,900

Federal coal ownership, but no Federal surface ownership 360,000

Federal coal and surface ownership 79,000

Wyoming total 510,000

Grand total (MST) 550,000
Table PN-4. Key to 7.5-minute quadrangle maps in the Wyodak-Anderson study limit, Powder River Basin. See

coal resources listed by quadrangle area (table PN-2) and quadrangle location map (fig. PN-1)

Number 7.5-minute quadrangle map Number 7.5-minute quadrangle map Number 7.5-minute quadrangle map

1 COOK CREEK BUTTE 31 BAR V RANCH 61 WYARNO

2 CLUBFOOT CREEK 32 PEARL SCHOOL 62 JONES DRAW

3 BIRNEY DAY SCHOOL 33 DECKER 63 S R SPRINGS

4 GREEN CREEK 34 HOLMES RANCH 64 SHULER DRAW

5 KING MOUNTAIN 35 PINE BUTTE SCHOOL 65 GARDNER GULCH

6 THREEMILE BUTTES 36 FORKS RANCH 66 FAWN DRAW

7 SONNETTE 37 QUIETUS 67 CABIN CREEK SE

8 SPRING CREEK RANCH 38 BEAR CREEK SCHOOL 68 KLINE DRAW

9 KIRBY 39 SAYLE HALL 69 RESERVOIR CREEK

10 TAINTOR DESERT 40 BRADSHAW CREEK 70 HOMESTEAD DRAW SW

11 BIRNEY SW 41 MOORHEAD 71 WHITE TAIL BUTTE

12 BIRNEY 42 THREE BAR RANCH 72 ROCKY BUTTE SW

13 BROWNS MOUNTAIN 43 BAY HORSE 73 BEAVER CREEK HILLS

14 POKER JIM BUTTE 44 RANCHESTER 74 BIG HORN

15 FORT HOWES 45 MONARCH 75 BUFFALO RUN CREEK

16 GOODSPEED BUTTE 46 ACME 76 VERONA

17 PHILLIPS BUTTE 47 BAR N DRAW 77 ULM

18 HODSDON FLATS 48 CEDAR CANYON 78 CLEARMONT

19 BAR V RANCH NE 49 O T O RANCH 79 LEITER

20 HALF MOON HILL 50 ROUNDUP DRAW 80 ARVADA

21 TONGUE RIVER DAM 51 BOX ELDER DRAW 80 ARVADA

22 SPRING GULCH 52 CABIN CREEK NW 81 ARVADA NE

23 LACEY GULCH 53 CABIN CREEK NE 82 LAREY DRAW

24 STROUD CREEK 54 BLACK DRAW 83 SPOTTED HORSE

25 HAMILTON DRAW 55 DEAD HORSE LAKE 84 RECLUSE

26 OTTER 56 CORRAL CREEK 85 PITCH DRAW

27 REANUS CONE 57 HOMESTEAD DRAW 86 OLIVER DRAW

28 SAYLE 58 ROCKY BUTTE 87 STORY

29 BLOOM CREEK 59 HULTZ DRAW 88 BANNER

30 LITTLE BEAR CREEK 60 SHERIDAN 89 HORSE HILL
Table PN-4. Key to 7.5-minute quadrangle maps, Wyodak-Anderson study limit—continued

Number 7.5-minute quadrangle map Number 7.5-minute quadrangle map Number 7.5-minute quadrangle map

90 UCROSS 120 CARR DRAW 150 THE GAP SW

91 JULIO DRAW 121 JEFFERS DRAW 151 SADDLE HORSE BUTTE

92 ARPAN BUTTE 122 ORIVA 152 ANTELOPE DRAW

93 JEWELL DRAW 123 GILLETTE WEST 153 ELAINE DRAW

94 LARIAT 124 GILLETTE EAST 154 PROVENCE RANCH

95 CROTON 125 FORTIN DRAW 155 HOE RANCH

96 TRUMAN DRAW 126 KLONDIKE RANCH 156 THE NIPPLE

97 WILDCAT 127 T A RANCH 157 FATS DRAW

98 CALF CREEK 128 T A RANCH NE 158 WAGS PINNACLE

99 WESTON SW 129 CRAZY WOMAN RANCH 159 PEPSSON DRAW

100 STONE MOUNTAIN 130 PLOESSERS DRAW 160 THREEMILE CREEK RESERVOIR

101 LAKE DE SMET WEST 131 JUNIPER DRAW 161 EAGLE ROCK

102 LAKE DE SMET EAST 132 LASKIE DRAW 162 NEIL BUTTE

103 BUFFALO NE 133 MORGAN DRAW 163 ROUGH CREEK

104 FREDRICK DRAW 134 SCOTT DAM 164 DRY CREEK RESERVOIR

105 FLOATE DRAW 135 FOUR BAR J RANCH 165 FOURMILE RESERVOIR

106 MITCHELL DRAW 136 APPEL BUTTE 166 SOLDIER CREEK

107 LIVINGSTON DRAW 137 THE GAP 167 FORT RENO

108 ECHETA 138 COYOTE DRAW 168 FORT RENO SE

109 TWENTYMILE BUTTE 139 COON TRACK CREEK 169 NORTH BUTTE

110 ORIVA NW 140 PURDY RESERVOIR 170 SAVAGETON

111 RAWHIDE SCHOOL 141 TRABING 171 GREASEWOOD RESERVOIR

112 MOYER SPRINGS 142 BROWN RANCH 172 ROCKY BUTTE GULCH

113 NORTH RIDGE 143 BOON 173 RENO JUNCTION

114 BUFFALO 144 BOWMAN FLAT 174 HILIGHT

115 BUFFALO SE 145 NEGRO BUTTE 175 OPEN A RANCH

116 PINE GULCH 146 BOGIE DRAW 176 KAYCEE NE

117 BEAR DRAW 147 DOUBLE TANKS 177 FIGURE 8 RESERVOIR

118 SOMERVILLE FLATS WEST 148 PLEASANTDALE 178 SUSSEX

119 SOMERVILLE FLATS EAST 149 SCAPER RESERVOIR 179 HOUSE CREEK
Table PN-4. Key to 7.5-minute quadrangle maps, Wyodak-Anderson study limit—continued

Number 7.5-minute quadrangle map Number 7.5-minute quadrangle map Number 7.5-minute quadrangle map

180 DRY FORK RANCH 196 PINEY CANYON SW 212 SEVEN L CREEK EAST

181 ROLLING PIN RANCH 197 SAWMILL CANYON 213 FLY DRAW

182 SOUTH BUTTE 198 ROSS 214 SOUTH FORK RESERVOIR

183 BAKER SPRING 199 ROSS FLAT 215 SUICIDE HILL

184 RATTLESNAKE DRAW 200 MACKEN DRAW 216 RED HILL

185 LITTLE THUNDER RESERVOIR 201 COAL DRAW NORTH 217 PATSY DRAW

186 RENO RESERVOIR 202 BETTY RESERVOIR 218 BEAUCHAMP RESERVOIR

187 PINEY CANYON NW 203 DUGOUT CREEK NORTH 219 GUMBO HILL

188 LINCH 204 COAL BANK DRAW 220 COAL HILL

189 TAYLOR RANCH 205 GILLAM DRAW EAST 221 HOLDUP HOLLOW

190 ARTESIAN DRAW 206 MARSH DRAW 222 WHIPPLE HOLLOW

191 PINE TREE 207 THOMPSON DRAW 223 BOBBY DRAW

192 TURNERCREST 208 BEAR CREEK 224 GLENROCK NW

193 RENO FLATS 209 COAL DRAW SOUTH 225 HYLTON RANCH

194 TECKLA SW 210 ALTA CREEK 226 LEUENBERGER RANCH

195 TECKLA 211 DUGOUT CREEK SOUTH 227 GILBERT LAKE
Table PN-5. Data used for computation of confidence intervals within reliability categories for Wyodak-Anderson

coal resources in the Powder River Basin. Volume refers to the calculated resource in millions of short tons

(MST). NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 1,488,759,443 5,670,020,546 11,140,313,431 3,612,068,158 21,911,161,578

Percent of area 7 26 51 16 100

Acres (area x 0.0002471) 367,880 1,401,092 2,752,831 892,561 5,414,365

SD (standard deviation (in ft) from

semivariogram model)

18.38 22.78 26.67 26.89 NA

Acre feet (acres x SD) 6,759,910 31,921,428 73,423,804 24,000,492 NA

Volume standard deviation (MST) 227 1,634 10,675 43,028 55,564

Pseudo n 2,928 1,239 152 1 NA

Table PN-6. Estimates of uncertainty (calculated with measurement error) for Wyodak-Anderson coal resources in

the Powder River Basin. To show detail, resources are reported in millions of short tons (MST) with four significant

figures

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Total calculated resource (MST) 43,670 167,700 303,700 35,610 550,700

Lower 90% confidence limit (MST) 43,300 165,000 286,100 0 459,300

Upper 90% confidence limit (MST) 44,050 170,400 321,200 106,400 642,100