Chapter HN

COAL RESOURCES OF THE HANNA AND CARBON

BASINS

By M.S. Ellis,1 G.L. Gunther,2 A.M. Ochs,2 V.V. Cavaroc,3

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

 North Carolina State University, Raleigh, North Carolina

4

 University of Delaware, Newark, Delaware
HN-ii

Contents

Coal Resources—Ferris 23, 25, 31, 50 and 65 Coal Zones, Ferris Coalfield,

Hanna Basin, Wyoming.....................................................................................HN-1

Ferris Coal Zones Resource Estimates—An Overview.....................................HN-1

Ferris Coal Zones Coal Resources................................................................HN-2

Confidence Limits for Ferris Coal Zones Coal Resources...........................HN-5

Coal Resources—Hanna 77, 78, 79, and 81 Coal Zones, Hanna Coalfield,

Hanna Basin, Wyoming.....................................................................................HN-8

Hanna Coal Zones Resource Estimates—An Overview...............................HN-8

Hanna Coal Zones Coal Resources...............................................................HN-9

Confidence Limits for Hanna Coal Zones Coal Resources........................HN-11

Coal Resources—Johnson-107 Coal Zone, South Carbon Coalfield, Carbon

Basin, Wyoming .............................................................................................HN-14

Johnson-107 Coal Zone Resource Estimates—An Overview....................HN-14

Johnson-107 Coal Zone Coal Resources....................................................HN-15

Confidence Limits for Johnson-107 Coal Zone Coal Resources................HN-17

References Cited ..............................................................................................HN-19

Figures

HN-1 Ferris 23 net coal isopach map and resource area.

HN-2 Ferris 25 net coal isopach map and resource area.

HN-3 Ferris 31 net coal isopach map and resource area.

HN-4 Ferris 50 net coal isopach map and resource area.

HN-5 Ferris 65 net coal isopach map and resource area.

HN-6 Location of 7.5-minute quadrangle maps in the Ferris coalfield.

HN-7 Federal coal and surface ownership in the Ferris 23 study limit.
HN-iii

Figures—continued

HN-8 Federal coal and surface ownership in the Ferris 25 study limit.

HN-9 Federal coal and surface ownership in the Ferris 31 study limit.

HN-10 Federal coal and surface ownership in the Ferris 50 study limit.

HN-11 Federal coal and surface ownership in the Ferris 65 study limit

HN-12 Ferris 23 overburden isopach map.

HN-13 Ferris 25 overburden isopach map.

HN-14 Ferris 31 overburden isopach map.

HN-15 Ferris 50 overburden isopach map.

HN-16 Ferris 65 overburden isopach map.

HN-17 Hanna 77 net coal isopach map and resource area.

HN-18 Hanna 78 net coal isopach map and resource area.

HN-19 Hanna 79 net coal isopach map and resource area.

HN-20 Hanna 81 net coal isopach map and resource area.

HN-21 Location of 7.5-minute quadrangle maps in the Hanna coalfield.

HN-22 Federal coal and surface ownership in the Hanna 77 study limit.

HN-23 Federal coal and surface ownership in the Hanna 78 study limit.

HN-24 Federal coal and surface ownership in the Hanna 79 study limit.

HN-25 Federal coal and surface ownership in the Hanna 81 study limit.

HN-26 Hanna 77 overburden isopach map.

HN-27 Hanna 78 overburden isopach map.

HN-28 Hanna 79 overburden isopach map.

HN-29 Hanna 81 overburden isopach map.

HN-30 Location of 7.5-minute quadrangle maps in the South Carbon coalfield.

HN-31 Federal coal and surface ownership in the Johnson-107 study limit.

HN-32 Johnson-107 net coal isopach map and resource area.

HN-33 Johnson-107 overburden isopach map.
HN-iv

Tables

HN-1 Coal resources of the Ferris 23 coal zone in the Ferris coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories

HN-2 Coal resources of the Ferris 23 coal zone in the Ferris coalfield, Hanna

Basin, reported by 7.5-minute quadrangle map area and Federal coal and

surface ownership

HN-3 Coal resources of the Ferris 25 coal zone in the Ferris coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories

HN-4 Coal resources of the Ferris 25 coal zone in the Ferris coalfield, Hanna

Basin, reported by 7.5-minute quadrangle map area and Federal coal and

surface ownership

HN-5 Coal resources of the Ferris 31 coal zone in the Ferris coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories

HN-6 Coal resources of the Ferris 31 coal zone in the Ferris coalfield, Hanna

Basin, reported by 7.5-minute quadrangle map area and Federal coal and

surface ownership

HN-7 Coal resources of the Ferris 50 coal zone in the Ferris coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories

HN-8 Coal resources of the Ferris 50 coal zone in the Ferris coalfield, Hanna

Basin, reported by 7.5-minute quadrangle map area and Federal coal and

surface ownership
HN-v

Tables—continued

HN-9 Coal resources of the Ferris 65 coal zone in the Ferris coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories

HN-10 Coal resources of the Ferris 65 coal zone in the Ferris coalfield, Hanna

Basin, reported by 7.5-minute quadrangle map area and Federal coal and

surface ownership

HN-11 Parameters and confidence intervals within reliability categories for

Ferris 23 coal resources

HN-12 Parameters and confidence intervals within reliability categories for

Ferris 25 coal resources

HN-13 Parameters and confidence intervals within reliability categories for

Ferris 31 coal resources

HN-14 Parameters and confidence intervals within reliability categories for

Ferris 50 coal resources

HN-15 Parameters and confidence intervals within reliability categories for

Ferris 65 coal resources

HN-16 Coal resources of the Hanna 77 coal zone in the Hanna coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories

HN-17 Coal resources of the Hanna 77 coal zone in the Hanna coalfield, Hanna

Basin, reported by 7.5-minute quadrangle map area and Federal coal and

surface ownership

HN-18 Coal resources of the Hanna 78 coal zone in the Hanna coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories
HN-vi

Tables—continued

HN-19 Coal resources of the Hanna 78 coal zone in the Hanna 78 coalfield,

Hanna Basin, reported by 7.5-minute quadrangle map area and Federal

coal and surface ownership

HN-20 Coal resources of the Hanna 79 coal zone in the Hanna coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories

HN-21 Coal resources of the Hanna 79 coal zone in the Hanna coalfield, Hanna

Basin, reported by 7.5-minute quadrangle map area and Federal coal and

surface ownership

HN-22 Coal resources of the Hanna 81 coal zone in the Hanna coalfield, Hanna

Basin, reported by overburden, net coal thickness, and reliability

categories

HN-23 Coal resources of the Hanna 81 coal zone in the Hanna coalfield, Hanna

Basin, reported by 7.5-minute quadrangle map area and Federal coal and

surface ownership

HN-24 Parameters and confidence intervals within reliability categories for

Hanna 77 coal resources

HN-25 Parameters and confidence intervals within reliability categories for

Hanna 78 coal resources

HN-26 Parameters and confidence intervals within reliability categories for

Hanna 79 coal resources

HN-27 Parameters and confidence intervals within reliability categories for

Hanna 81 coal resources

HN-28 Coal resources of the Johnson-107 coal zone in the South Carbon

coalfield, Carbon Basin, reported by overburden, net coal thickness, and

reliability categories
HN-vii

Tables—continued

HN-29 Coal resources of the Johnson-107 coal zone in the South Carbon

coalfield, Carbon Basin, reported by 7.5-minute quadrangle map area and

Federal coal and surface ownership

HN-30 Data used for computation of confidence limits intervals with reliability

categories for Johnson-107 coal resources

HN-31 Estimates of uncertainty with measurement error for the Johnson-107

coal resources
HN-1

COAL RESOURCES—FERRIS 23, 25, 31, 50, AND 65 COAL

ZONES, FERRIS COALFIELD, HANNA BASIN, WYOMING

FERRIS COAL ZONES RESOURCE ESTIMATES—AN OVERVIEW

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

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

thickness, and areal extent of the coal.

• Resource tables for the Ferris 23, 25, 31, 50, and 65 coal zones in the Ferris

coalfield include coal and overburden thickness categories from Wood and

others (1983) that are based on apparent coal rank, and additional categories to

provide more detail. Resources are also reported by Federal coal and surface

ownership categories and by 7.5-minute quadrangle areas for each of the coal

zones.

• 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 is 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.
HN-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 assurance.

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

for the Ferris 23, 25, 31, 50, and 65 coal resource estimates in the Ferris

coalfield, is also included in this study.

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

figures.

FERRIS COAL ZONES COAL RESOURCES

The assessment units in the Ferris coalfield were investigated as the Ferris 23, 25,

31, 50, and 65 coal zones. Each coal zone has a specific lateral extent (study limit)

based on outcrop data, unpublished maps, drill hole data availability and

distribution, and extrapolated overburden. Where overburden was very thick and

data were scarce, a generalized boundary was drawn along a geographic or cultural

feature that was about three miles from the deepest control point(s).

The study areas in the Ferris coalfield were defined as follows. The Ferris 23 study

limit (fig. HN-1) is defined by the outer edge of the Seminoe Reservoir to the

northwest, the Ferris 23 outcrop from Glass and Roberts (1980) to the south and

southwest, and the contact of the Ferris and Hanna Formations to the east from

Dobbin and others (1929). The entire study area is about 50,800 acres (20,558

hectares) in size.
HN-3

The Ferris 25 study limit (fig. HN-2) is defined by the outer edge of the Seminoe

Reservoir to the northwest, the Ferris 25 outcrop to the south and southwest from

Glass and Roberts (1980), and the contact of the Ferris and Hanna Formations to

the east and northeast from Dobbin and others (1929). The entire study area is

about 47,900 acres (19,384 hectares) in size.

The Ferris 31 study limit (fig. HN-3) is defined by the Ferris 31 outcrop to the

south from Glass and Roberts (1980), the contact of the Ferris and Hanna

Formations to the east from Dobbin and others (1929), and the outer edge of the

Seminoe Reservoir to the west. The southeastern boundary is generalized to show

the approximate extent of the Ferris 23 coal (where the coal appears to pinch out)

based on the drill hole data. The entire study area is about 25,600 acres (10,560

hectares) in size.

The Ferris 50 study limit (fig. HN-4) is defined by the Ferris 50 outcrop to the

south and southwest from Glass and Roberts (1980), the contact of the Ferris and

Hanna Formations to the east and fault lines in the northwest from Dobbin and

others (1929). The northeastern extent is a generalized boundary approximately 3

miles from the deepest control points. The entire study area is about 30,200 acres

(12,222 hectares) in size.

The Ferris 65 study limit (fig. HN-5) is defined by the Ferris 65 outcrop to the

south and west from Glass and Roberts (1980) and the contact of the Ferris and

Hanna Formations to the east from Dobbin and others (1929). The northern extent

is a generalized boundary approximately 3 miles from the deepest control points in

the eastern part of the study area. The generalized boundary extends west and

terminates in the northwest to include an area that contains several control points
HN-4

between two bounding faults. The entire study area is about 19,600 acres (7,932

hectares) in size.

Ferris coal resources were calculated using several software packages and custom

programs. Details of the resource calculation methodology are given in Ellis and

others (1999, in press).

To calculate the Ferris coal resources, data was compiled in a StratiFact* (GRG

Corporation, 1996) relational database. The coal beds to be included in the Ferris

23, 25, 31, 50, and 65 coal zones were correlated in the database and data were

initially managed in one data set. Data for each coal zone were down loaded

individually and a custom program was used to calculate net coal thickness at each

data point (drill hole or measured section) location. From this point on, the data

for each coal zone were managed separately.

For each coal zone, net coal thickness and overburden thickness was gridded, and

isopach maps were produced using EarthVision* (Dynamic Graphics, Inc., 1997)

software. The grids were made using an isopach grid option (special handling of 0

values and terminated data) with grid spacings of 50 x 50 meters.

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

quadrangle map area (fig. HN-6) (U.S. Geological Survey National Mapping

Division unpublished data, undated), Federal coal and surface ownership (figs.

HN-7 through HN-11) (Bureau of Land Management unpublished data, undated),

reliability, net coal thickness (figs. HN-1 through HN-5), and overburden

categories (figs. HN-12 through HN-16)) were created on individual layers as

ARC/INFO* (ESRI, 1998a) polygon coverages. The coverages for each coal zone

were unioned to make one polygon coverage for each of the five coal zone study
HN-5

areas. These union coverages contained all of the polygons for each coal zone,

with many attributes in every polygon. The polygons in the union coverages were

edited in ARC/INFO* and ArcView* (ESRI, 1998b).

Coal resources were calculated for each study area using the EarthVision* (EV)

volumetrics tool, which calculates tonnages in each polygon in the union coverage

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 the EV volumetrics report and the union coverage polygon

attribute table for each of the study areas were combined in Excel* (Microsoft,

1997) spreadsheet software. In each of the five Excel spreadsheets, data for

polygons containing mine or lease areas or areas of coal less than 2.5 ft in

thickness were deleted from the data sets. Resource tables were created using the

data from the remaining polygons (tables HN-1 through HN-10). Lease areas may

include public and/or State leases in addition to Federal leases. The final resource

areas (areas that met all coal resource criteria) were 24,900 acres (10,077 hectares)

in size for Ferris 23 (fig. HN-1), 36,900 acres (14,933 hectares) in size for Ferris

25 (fig. HN-2), 18,900 acres (7,649 hectares) for Ferris 31 (fig. HN-3), 24,300

acres (9,834 hectares) in size for Ferris 50 (fig. HN-4), and 16,800 acres (6,799

hectares) in size for Ferris 65 (fig. HN-5).

*Commercial software package

CONFIDENCE LIMITS FOR FERRIS COAL ZONES COAL RESOURCES

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

a point estimate. In this study we computed 90-percent confidence intervals on the
HN-6

volume of coal in the Ferris 23, 25, 31, 50, and 65 coal zones 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

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 Ferris 23, 25, 31, 50, 65 coal zones in

the Ferris coalfield were calculated by J.H. Schuenemeyer and H.C. Power. The

data sets that they used contained net coal measurements from 69 locations for the

Ferris 23, 68 locations for the Ferris 25, 14 locations for the Ferris 31, 12 locations

for the Ferris 50, and 93 locations for the Ferris 65 coal zones. These data sets

only included data points for locations where net coal was greater than or equal to

2.5 ft in thickness (no 0 net coal thickness values) and data that were representative

of the entire coal zone (no terminated holes) being represented.

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

included investigating coal thickness trends and spatial correlation. Ferris 23 and

25 coal zones showed no significant coal thickness trends, therefore coal thickness

was used to compute semivariograms, and the semivariograms were fitted to linear

models. Parameter estimates for Ferris 23 were sill=40.00 ft2, nugget=0.00 ft2,

range=2.50 miles, and slope=16.00. Parameter estimates for Ferris 25 were

sill=40.00 ft2, nugget=20.00 ft2, range=3.00 miles, and slope=8.57. Standard

deviations of coal thickness were obtained from the semivariogram models. Ferris
HN-7

31, 50, and 65 coal zones showed no coal thickness trends or spatial correlations

that were statistically significant. The standard deviations of coal thickness were

obtained directly from the data.

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 Ferris 23, 25, 31, 50, and

65 coal were then calculated at a 90-percent confidence interval with measurement

error. Sample sizes for the Ferris 31, 50, and 65 coal zones were small, therefore

the computed confidence limits are not statistically meaningful. Some of the

parameters used and results of the confidence interval calculations are shown in

tables HN-11 through HN-15. A detailed description of the methodology used is

given in Schuenemeyer and Power (in press) and in Ellis and others (1999, in

press).
HN-8

COAL RESOURCES—HANNA 77, 78, 79, AND 81 COAL ZONES,

HANNA COALFIELD, HANNA BASIN, WYOMING

HANNA COAL ZONES 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 Hanna 77, 78, 79, and 81 coal zones in the Hanna

coalfield include coal and overburden thickness categories from Wood and

others (1983) that are based on apparent coal rank, and additional categories to

provide more detail. Resources are also reported by Federal coal and surface

ownership categories and by 7.5-minute quadrangle areas for each of the coal

zones.

• 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 is 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.
HN-9

• 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 assurance.

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

for the Hanna 77, 78, 79, and 81 coal resource estimates in the Hanna coalfield,

is also included in this study.

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

figures.

HANNA COAL ZONES COAL RESOURCES

The assessment units in the Hanna coalfield were investigated as the Hanna 77, 78,

79, and 81 coal zones. Each coal zone has a specific lateral extent (study limit)

based on outcrop data, unpublished maps, drill hole data availability and

distribution, and extrapolated overburden. Where overburden was very thick and

data were scarce, a generalized boundary was drawn along a geographic or cultural

feature that was about three miles from the deepest control point(s). The study

areas in the Hanna coalfield were defined as follows: The Hanna 77 study limit

(fig. HN-17) is defined by the Medicine Bow River along the northern margin and

the Hanna 77 coal outcrop from Dobbin and others (1929). The entire study area is

about 38,100 acres (15,519 hectares) in size. The Hanna 78 study limit (fig. HN18) is defined by the Medicine Bow River along the northern margin and the

Hanna 78 coal outcrop from Dobbin and others (1929). The entire study area is

about 36,100 acres (14,609 hectares) in size. The Hanna 79 study limit (fig. HN-
HN-10

19) is defined by the Medicine Bow River along the northern margin and the

Hanna 79 outcrop from Dobbin and others (1929). The entire study area is about

27,500 acres (11,129 hectares) in size. The Hanna 81 study limit (fig. HN-20) is

defined by the Medicine Bow River along the northern margin and the Hanna 81

outcrop from Dobbin and others (1929). The entire study area is about 25,800

acres (10,441 hectares) in size.

Hanna coal resources were calculated using several software packages and custom

programs. Details of the resource calculation methodology are given in Ellis and

others (1999, in press). To calculate the Hanna coal resources, data was compiled

in a StratiFact* (GRG Corporation, 1996) relational database. Coal beds to be

included in the Hanna 77, 78, 79, and 81 coal zones were correlated in the

database. Data were initially managed in one data set. Data for each coal zone

were downloaded individually. A custom program was used to calculate net coal

thickness at each data point (drill hole or measured section) location. From this

point on, data for each coal zone were managed separately.

For each coal zone, net coal thickness and overburden thickness were gridded, and

isopach maps were produced using EarthVision* (Dynamic Graphics, Inc., 1997)

software. The grids were made using an isopach grid option (special handling of 0

values and terminated data) with grid spacings of 50 x 50 meters.

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

quadrangle map (fig. HN-21) area (U.S. Geological Survey National Mapping

Division unpublished data, undated), Federal coal and surface ownership (fig. HN22 through HN-25) (Bureau of Land Management unpublished data, undated),

reliability, net coal thickness (figs. HN-17 through HN-20), and overburden

categories (figs. HN-26 through HN-29)) were created on individual layers as

ARC/INFO* (ESRI, 1998a) polygon coverages. The coverages for each coal zone
HN-11

were unioned to make one polygon coverage for each of the four study areas.

These union coverages contained all of the polygons for each coal zone, with many

attributes in every polygon. The polygons in the union coverages were edited in

ARC/INFO* and ArcView* (ESRI, 1998b).

Coal resources were calculated for each study area using the EarthVision* (EV)

volumetrics tool, which calculates tonnages in each polygon in the union coverage

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 the EV volumetrics report and the union coverage polygon

attribute table for each of the study areas were combined in Excel* (Microsoft,

1997) spreadsheet software. In each of the five Excel spreadsheets, data for

polygons containing mine or lease areas or areas of net coal less than 2.5 ft in

thickness were deleted from the data sets. Resource tables were created using the

data from the remaining polygons (tables HN-16 through HN-23). Lease areas may

include public and/or state leases in addition to Federal leases. The final resource

areas (areas that met all coal resource criteria) were about 32,400 acres (13,112

hectares) in size for Hanna 77 (fig. HN-17), about 30,900 acres (12,505 hectares)

in size for Hanna 78 (fig. HN-18), about 24,100 acres (9,753 hectares) in size for

Hanna 79 (fig. HN-19), and 21,700 acres (8,782 hectares) in size for Hanna 81 (fig.

HN-20).

*Commercial software package

CONFIDENCE LIMITS FOR HANNA COAL ZONES COAL

RESOURCES

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

a point estimate. In this study we computed 90-percent confidence intervals on the
HN-12

volume (total resource in millions of short tons) of coal in the Hanna 77, 78, 79,

and 81 coal zones 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

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 Hanna 77, 78, 79, and 81 coal zones in

the Hanna Basin were calculated by J.H. Schuenemeyer and H.C. Power. The

data sets that they used contained net coal measurements from 74 locations for

Hanna 77, 217 locations for Hanna 78, 117 locations for Hanna 79, and 108

locations for Hanna 81. These data sets only included locations that contained

Ferris coal in each of the individual coal zones (no 0 values) and data that were

representative of the entire coal zones (no terminated holes). Each data set was

studied separately.

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

included investigating coal thickness trends and spatial correlation. Neither the

trends nor the spatial correlations in the coal zones were found to be statistically

significant. Standard deviations of coal thickness for each coal zone were obtained

from the data directly. Volumes of Hanna 77, 78, 79, and 81 coal were 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 HN-24 through HN-27. A detailed description of the methodology used is
HN-13

given in Schuenemeyer and Power (in press) and in Ellis and others (1999, in

press).
HN-14

COAL RESOURCES—JOHNSON-107 COAL ZONE, SOUTH

CARBON COALFIELD, CARBON BASIN, WYOMING

JOHNSON-107 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 Johnson-107 coal zone in the South Carbon coalfield

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

that are based on apparent coal rank, and additional categories to provide more

detail. Resources are also reported by Federal coal and surface ownership

categories and by 7.5-minute quadrangle areas.

• 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.

• 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.

• 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.
HN-15

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

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

for Johnson-107 coal resource estimates in the South Carbon coalfield, is also

included in this study.

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

figures.

JOHNSON-107 COAL ZONE COAL RESOURCES

The lateral extent (study limit) of the Johnson-107 coal zone is defined by the

outcrop of the Johnson coal bed as defined by Dobbin and others (1929) to the

south and the zero net coal thickness isopach line in the northwest and north

central area. The northeastern area was defined by a generalized boundary along a

three-mile buffer from the data locations. The entire study area is about 19,400

acres (7,851 hectares) in size.

Johnson-107 coal resources were calculated using several software packages and

custom programs. Details of the resource calculation methodology are given in

Ellis and others (1999, in press).

To calculate the Johnson-107 coal resources, data was compiled in a StratiFact*

(GRG Corporation, 1996) relational database. The beds included in the Johnson107 coal zone, the Johnson, Finch, C106, and C107 coal beds, were then correlated

in the database. A custom program was used to calculate net coal thickness of coal

in the Johnson-107 coal zone at each data point (drill hole or measured section)

location.

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

were produced using EarthVision* (Dynamic Graphics, Inc., 1997) software. The
HN-16

grids were made using an isopach grid option (special handling of 0 values and

terminated data) with grid spacings of 50 x 50 meters.

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

quadrangle (fig. HN-30) map area (U.S. Geological Survey National Mapping

Division, unpublished data, undated), Federal coal and surface ownership (fig. HN31) (Bureau of Land Management, unpublished data, undated), reliability, net coal

thickness (fig. HN-32), and overburden categories (fig. HN-33)) 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* 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 acreft for subbituminous rank coal (Wood and others, 1983). Data from the EV

volumetrics report and the union coverage polygon attribute table were combined

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

mine or lease areas (fig. HN-32) 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 HN-28 and HN-29). The final resource area (fig. HN32) (area that met all coal resource criteria) was about 14,700 acres (5,949

hectares) in size.

*Commercial software package
HN-17

CONFIDENCE LIMITS FOR JOHNSON-107 COAL ZONE COAL

RESOURCES

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

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

volume (total resource in millions of short tons) of coal in the Johnson-107 coal

zone in the measured, indicated, and inferred 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

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 Johnson-107 coal zone in the South

Carbon coalfield were calculated by J.H. Schuenemeyer and H.C. Power. The

data set that they used contained net coal measurements from 35 locations. This

data set only included data points for locations where net coal was greater than or

equal to 2.5 ft in thickness (no 0 net coal thickness 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). Spatial

correlation, as determined from the semivariogram of residual thickness, was

negligible. Standard deviation of coal thickness was computed from residual

thickness. Differences in point densities were compensated for by calculating
HN-18

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

variability of volume for each of the reliability categories. The estimated pseudo n

for the inferred category was less than one, thus the uncertainty estimates are not

statistically meaningful. Volumes of Johnson-107 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 HN-30

and HN-31. A detailed description of the methodology used is given in

Schuenemeyer and Power (in press) and in Ellis and others (1999, in press).
HN-19

REFERENCES CITED

Dobbin, C.E., Bowen, C.F., and Hoots, H.W., 1929, Geology and coal and oil and

gas resources of the Hanna and Carbon Basins, Carbon County, Wyoming:

U.S. Geological Survey Bulletin 804, Plate 27.

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

(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., and Ochs, A.M., in press,

Preliminary report on methodolgy for calculating coal resources of the

Wyodak-Anderson coal zone in the Powder River Basin, Wyoming and

Montana, U.S. Geological Survey Open-File Report 98-789B.

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

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

Redlands, CA 92373, USA.

_____ 1998, ArcView, v.3.0a: Environmental Systems Research Institute, Inc., 380

New York Street, Redlands, CA 92373, USA.
HN-20

Glass, G.B. and Roberts, J.T., 1980, Coals and coal-bearing rocks of the Hanna

coalfield, Wyoming: Geological Survey of Wyoming Report of

Investigations No. 11.

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

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

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

1 Microsoft Way, Redman, WA 98052.

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

assessment—An application to coal: Mathematical Geology.

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.
Ferris Coalfield

Ferris 23 

Study Limit

(ft)

gure HN-1. Ferris 23 net coal isopach map and resource area.

0 2 4 Miles

0 2 4 6 8 Kilometers

o

Normal fault (Glass

and Roberts, 1980)

Index map showing area

included in resource calculations

(does not include areas of mines, leases, 

or net coal < 2.5 ft thick)

Resource area

0

2.5

5

10

Mine or 

lease

areas
Ferris Coalfield

Ferris 25 Study Limit

(ft)

gure HN-2. Ferris 25 net coal isopach map and resource area.

2 

0"

0 2 4 Miles

0 2 4 6 8 Kilometers

o

Normal fault (Glass

and Roberts, 1980)

Index map showing area

included in resource calculations

(does not include areas of mines, leases, or 

net coal < 2.5 ft thick)

Resource area

0

2.5

5

20

10

Mine or 

lease 

areas
Ferris Coalfield

Ferris 31 Study Limit

(ft)

gure HN-3. Ferris 31 net coal isopach map and resource area.

0 2 4 Miles

0 2 4 6 8 Kilometers

Normal fault (Glass

and Roberts, 1980)

Index map showing area

included in resource calculations

(does not include areas of mines, leases, 

or net coal < 2.5 ft thick)

Resource area

0

2.5

5

10

20

Mine or

lease 

areas
Ferris Coalfield

Ferris 50 Study Limit

(ft)

gure HN-4. Ferris 50 net coal isopach map and resource area.

0 2 4 Miles

0 2 4 6 8 Kilometers

Normal fault (Glass

and Roberts, 1980)

Index map showing area

included in resource calculations

(does not include areas of mines, leases, 

or net coal < 2.5 ft thick)

Resource area

0

2.5

5

10

Mine or 

lease

areas
Ferris Coalfield

Ferris 65 Study Limit

 

"

0 2 4 6 Miles

0 2 4 6 8 Kilometers

o

ure HN-5. Ferris 65 net coal isopach map and resource area.

Normal fault (Glass

and Roberts, 1980)

Index map showing area

included in resource calculations

(does not include areas of mines, leases, 

or net coal < 2.5 ft thick)

Resource area

0

2.5

5

10

Mine or 

lease areas
42 

41 52'30"

106 52'30" 106 45' 106 37'30"

0 2 4 Miles

0 2 4 6 8 Kilometers

o o o

o

o

Figure HN-6. Location of 7.5-minute quadrangle maps in the Ferris 

coalfield.

6 7 8

1 Seminoe Dam SE

2 Schneider Ridge

3 Pats Bottom

4 Tenmile Spring

5 Elmo

6 Walcott

7 Dana 

8 Hanna

7.5-minute quadrangle maps

Ferris coalfield

Ferris 25 study limit

Common boundary 

Common Boundary

 For Ferris 23 and 25

 Common Boundary

 For Ferris 23, 25, 50, and 65 

Ferris 23 study limit

Ferris 50 study limit

Ferris 65 study limit

1 2

4 5

 Common Boundary

 For Ferris 23, 25, and 31 

Ferris 31 study limit

3
Ferris 23 Study Limit

42 

41 52'30"

106 52'30" 106 45' 106 37'30"

0 2 4 Miles

0 2 4 6 8 Kilometers

o o o

o

o

Ferris Coalfield

No Federal coal or Federal surface

Federal coal, but no Federal 

surface

Federal Coal = Federal subsurface Federal coal and Federal surface

management of all minerals, coal 

only, or oil, gas, and coal 

Federal Surface = Federal surface 

ownership

Figure HN-7. Federal coal and surface ownership in the Ferris 23 

study limit. 
Ferris Coalfield

Ferris 25 Study Limit

42 

41 52'30"

106 52'30" 106 45' 106 37'30"

0 2 4 Miles

0 2 4 6 8 Kilometers

o o o

o

o

No Federal coal or Federal surface

Federal coal, but no Federal 

surface

Federal Coal = Federal subsurface Federal coal and Federal surface

management of all minerals, coal 

only, or oil, gas, and coal 

Federal Surface = Federal surface 

ownership

Figure HN-8. Federal coal and surface ownership in the Ferris 25 

study limit. 
Ferris Coalfield

Ferris 31 Study Limit

42 

41 52'30"

106 52'30" 106 45' 106 37'30"

0 2 4 Miles

0 2 4 6 8 Kilometers

o o o

o

o

No Federal coal or Federal surface

Federal Coal = Federal subsurface Federal coal and Federal surface

management of all minerals, coal 

only, or oil, gas, and coal 

Federal Surface = Federal surface 

ownership

Figure HN-9. Federal coal and surface ownership in the Ferris 31 

study limit. 
Ferris Coalfield

Ferris 50 Study Limit

42 

41 52'30"

106 52'30" 106 45' 106 37'30"

0 2 4 Miles

0 2 4 6 8 Kilometers

o o o

o

o

No Federal coal or Federal surface

Federal coal, but no Federal 

surface

Federal Coal = Federal subsurface Federal coal and Federal surface

management of all minerals, coal 

only, or oil, gas, and coal 

Federal Surface = Federal surface 

ownership

Figure HN-10. Federal coal and surface ownership in the Ferris 50 

study limit. 
Ferris Coalfield

Ferris 65 Study Limit

42 

41 52'30"

106 52'30" 106 45' 106 37'30"

o

o

o o o

0 2 4 Miles

0 2 4 6 8 Kilometers

No Federal coal or Federal surface

Federal coal, but no Federal 

surface

Federal Coal = Federal subsurface Federal coal and Federal surface

management of all minerals, coal 

only, or oil, gas, and coal 

Federal Surface = Federal surface 

ownership

Figure HN-11. Federal coal and surface ownership in the Ferris 65

study limit. 
Ferris Coalfield

Ferris 23 Study Limit

500

1000

2000

3000

4000

gure HN-12. Ferris 23 overburden isopach map.

2 

0"

0 2 4 Miles

0 2 4 6 8 Kilometers

o

0

Normal fault (Glass

and Roberts, 1980)
0 2 4 Miles

0 2 4 6 8 Kilometers

Ferris Coalfield

Ferris 25 

Study Limit

Figure HN-13. Ferris 25 overburden isopach map.

42 

30"

500

1000

2000

3000

4000

(ft)

0

o

Normal fault (Glass

and Roberts, 1980)
500

1000

2000

3000

4000

thickness (ft)

0

Ferris Coalfield

Ferris 31 Study Limit

42 

30"

o

Normal fault 

(Glass and 

Roberts, 1980)

Figure HN-14. Ferris 31 overburden isopach map.

0 2 4 Miles

0 2 4 6 8 Kilometers
Ferris Coalfield

Ferris 50 Study Limit

thickness (ft)

42 

30"

o

Figure HN-15. Ferris 50 overburden isopach map.

0 2 4 Miles

0 2 4 6 8 Kilometers

500

1000

2000

3000

4000

0

 Normal fault 

(Glass and 

Roberts, 1980)
Overburden 

thickness (ft)

Ferris Coalfield

Ferris 65 Study Limit

42 

30"

o

500

1000

0

100

400

300

200

Normal fault 

(Glass and 

Roberts, 1980)

Figure HN-16. Ferris 65 overburden isopach map.

0 2 4 Miles

0 2 4 6 8 Kilometers
Miles

Kilometers

0 1 2 3

0 2 4

Normal fault (Glass 

and Roberts, 1980)

Hanna 77

Study Limit

5

10

20

30

40

50

(does not include lease areas or net coal < 2.5 ft thick)

Resource area

Index map showing area

included in resource calculations

gure HN-17. Hanna 77 net coal isopach map and resource area.

Lease

areas
Net coal 

thickness (ft)

Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

Hanna 78

Study Limit

2.5

5

10

20

30

40

Normal fault (Glass

and Roberts, 1980)

gure HN-18. Hanna 78 net coal isopach map and resource area.

Index map showing

area included in

resource calculations

(does not include lease areas

or net coal < 2.5 ft thick)

Resource area

lLease

areas
Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

Normal fault (Glass 

and Roberts, 1980)

Hanna 79

Study Limit

2.5

5

10

20

30

0

Index map showing area

included in resource calculations

(does not include lease areas 

or net coal < 2.5 ft thick)

Resource area

Lease

areas

gure HN-19. Hanna 79 net coal isopach map and resource area.
Miles

Kilometers

0 1 2 3

0 2 4

Normal fault (Glass 

and Roberts, 1980)

2 

0"

Hanna 81

Study Limit

2.5

5

10

20

30

Index map showing area

included in resource calculations

(does not include lease areas or net coal < 2.5 ft thick)

o

Resource area

Lease

areas

gure HN-20. Hanna 81 net coal isopach map and resource area.
Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

 

"

o

1 T E Ranch

2 Difficulty

3 Elmo

4 Como West

5 Hanna

6 Carbon

7.5-minute quadrangle maps

Hanna coalfield

Hanna 78 study limit

Common boundary 

Hanna 81 study limit

Hanna 79 study limit

Hanna 77 study limit

Figure HN-21. Location of 7.5-minute quadrangle maps in the Hanna coalfield.

5

3 4

6 
Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

Hanna 77

Study Limit

No Federal coal or Federal surface

Federal coal, but no Federal 

surface

Federal coal and Federal surface

Federal coal = Federal 

subsurface management of 

all minerals, coal only, 

or oil, gas, and coal 

Federal surface = Federal 

surface ownership

gure HN-22. Federal coal and surface ownership in the Hanna 77 study limit. 
Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

Hanna 78

Study Limit

No Federal coal or Federal surface

Federal coal, but no Federal 

surface

Federal coal and Federal surface

Federal coal = Federal 

subsurface management of 

all minerals, coal only, 

or oil, gas, and coal 

Federal surface = Federal 

surface ownership

gure HN-23. Federal coal and surface ownership in the Hanna 78 study limit. 
Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

Hanna 79

Study Limit

No Federal coal or Federal 

surface

Federal coal, but no Federal 

surface

Federal coal and Federal 

surface

Federal coal = Federal 

subsurface management of 

all minerals, coal only, 

or oil, gas, and coal 

Federal surface = Federal 

surface ownership

Figure HN-24. Federal coal and surface ownership in the Hanna 79 study limit. 
Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

Hanna 81

Study Limit

No Federal coal or Federal surface

Federal coal, but no Federal 

surface

Federal coal and Federal surface

Federal coal = Federal 

subsurface management of 

all minerals, coal only, 

or oil, gas, and coal 

Federal surface = Federal 

surface ownership

igure HN-25. Federal coal and surface ownership in the Hanna 81 study limit. 
500

1000

2000

3000

4000

Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

Hanna 77

Study Limit

Normal faults (Glass and

Roberts, 1980)

gure HN-26. Hanna 77 overburden isopach map.

400
0

100

200

300

400

500

1000

2000

3000

4000

5000

Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

Hanna 78

Study Limit

o

Normal faults (Glass and

Roberts, 1980)

igure HN-27. Hanna 78 overburden isopach map.
Miles

Kilometers

0 1 2 3 4 5

0 2 4 6 8

0

100

500

1000

2000

3000

4000

Hanna 79

Study Limit

Normal faults 

(Glass and Figure HN-28. Hanna 79 overburden isopach map. Roberts, 1980)

200

300

400
Miles

Kilometers

0 1 2 3

0 2 4

500

1000

2000

3000

 

Hanna 81

Study Limit

o

Normal faults (Glass 

and Roberts, 1980)

100

Figure HN-29. Hanna 81 overburden isopach map.

200

300

400
Carbon Basin

Miles

0 Kilometers

2

4 6

0 1 3

2

4

South Carbon

Coalfield

(Johnson-107

Study Limit)

106 22'30"

41 52'30"

41 45'

1 Carbon

2 Halfway Hill

7.5-minute quadrangle maps

o

o

o

Figure HN-30. Location of 7.5-minute quadrangle maps in the South Carbon 

coalfield.

3 Elk Mountain

4 T L Ranch

1 2

3 4
Carbon Basin

Miles

0 Kilometers

2

4 6

0 1 3

2

4

Johnson-107

Study Limit

106 22'30"

41 52'30"

41 45'

o

o

o

No Federal coal or Federal surface

Federal coal, but no Federal 

surface

Federal Coal = Federal subsurface Federal coal and Federal surface

management of all minerals, coal 

only, or oil, gas, and coal 

Federal Surface = Federal surface 

ownership

Figure HN-31. Federal coal and surface ownership in the Johnson-107 

study limit. 
Carbon Basin

Net coal 

thickness (ft)

Miles

0 Kilometers

2

4 6

0 1 3

2

4

Johnson-107

Study Limit 

106 22'30"

41 52'30"

41 45'

5

10

20

30

40

50

100

0

Index map showing 

area included in 

resource calculations

(does not include areas of mines, 

leases,or net coal < 2.5 ft thick)

Resource 

area

Mine 

and 

lease

Areas

o

o

o

2.5

Figure HN-32. Johnson-107 net coal isopach 

map and resource area.

Fault 
o

o

o

Overburden 

Carbon Basin thickness (ft)

0

100

200

300

400

500

1000

0

2

4 6

0 1 3

2

4

Johnson-107

Study Limit

106 22'30"

41 52'30"

41 45'

Miles

Kilometers

Fault 

Figure HN-33. Johnson-107 overburden isopach map.
Table HN-1. Coal resources of the Ferris 23 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

overburden (fig. HN-12), net coal thickness (fig. HN-1), and reliability categories. Zeros (0) indicate areas where

no resources were calculated. Resources are reported in millions of short tons (MST) with two significant figures.

The table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN-1).

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

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

0-100 ft 2.5-5 ft 1.8 8.7 5.1 0.27 16

5-10 ft 4.1 7.8 37 2.7 52

10-20 ft 6.5 5.8 0.17 0 12

0-100 ft total 12 22 42 3.0 80

100-200 ft 2.5-5 ft 0.24 0.025 1.3 0.62 2.2

5-10 ft 0.71 2.2 1.1 0.11 4.1

10-20 ft 0.78 0 0 0 0.78

100-200 ft total 1.7 2.2 2.4 0.73 7.1

200-500 ft 2.5-5 ft 0.53 0.13 6.8 6.1 14

5-10 ft 2.1 3.4 8.2 0.16 14

10-20 ft 3.7 1.2 0 0 4.9

200-500 ft total 6.3 4.8 15 6.3 32

500-1,000 ft 2.5-5 ft 0.23 0.069 7.2 4.4 12

5-10 ft 0.78 4.1 13 0.15 18

10-20 ft 1.2 4.4 0.26 0 5.9

500-1,000 ft total 2.2 8.6 20 4.6 36

1,000-1,500 ft 2.5-5 ft 0 0 3.5 5.8 9.3

5-10 ft 0 0 7.8 0.065 7.9

1,000-1,500 ft total 0 0 11 5.8 17

1,000-2,000 ft 2.5-5 ft 0 0 4.2 5.2 9.5

5-10 ft 0 0 2.5 0.061 2.6

1,500-2,000 ft total 0 0 6.8 5.3 12

>2,000 ft 2.5-5 ft 0 0 7.5 35 42

5-10 ft 0 0 3.8 3.3 7.2

>2,000 ft total 0 0 11 38 50

Grand total (MST) 23 38 110 64 230
Table HN-2. Coal resources of the Ferris 23 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

7.5-minute quadrangle (fig. HN-6) and Federal coal and surface ownership (fig. HN-7). Resources are reported in

millions of short tons (MST) with two significant figures. The table does not include resources for coal less than

2.5 ft thick or coal in mine or lease areas (fig. HN-1). Resource numbers will not sum to match totals due to

independent rounding

7.5-minute quadrangle map Federal ownership Total (MST)

DANA No Federal coal or surface ownership 0.15

Federal coal and surface ownership 0.14

DANA total 0.29

PATS BOTTOM No Federal coal or surface ownership 88

No Federal coal, but Federal surface ownership 9.0

Federal coal and surface ownership 27

PATS BOTTOM total 120

SCHNEIDER RIDGE No Federal coal or surface ownership 2.6

No Federal coal, but Federal surface ownership 0.24

Federal coal and surface ownership 3.8

SCHNEIDER RIDGE total 6.7

SEMINOE DAM SE No Federal coal or surface ownership 42

Federal coal and surface ownership 39

SEMINOE DAM SE total 80

TENMILE SPRING No Federal coal or surface ownership 9.8

Federal coal and surface ownership 7.9

TENMILE SPRING total 18

WALCOTT No Federal coal or surface ownership 3.2

No Federal coal, but Federal surface ownership 0.48

Federal coal and surface ownership 0.28

WALCOTT total 4.0

Grand total of Federal coal (MST) 78

Grand total (MST) 230
Table HN-3. Coal resources of the Ferris 25 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

overburden (fig. HN-13), net coal thickness (fig HN-2), and reliability categories. Zeros (0) indicate areas where

no resources were calculated. Resources are reported in millions of short tons (MST) with two significant figures.

Table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN-2). Resource

numbers will not sum to match totals due to independent rounding

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

0-100 ft 2.5-5 ft 0.067 0.39 0.12 0 0.58

5-10 ft 0.30 0.86 1.5 2.9 5.6

10-20 ft 1.0 0.20 0 6.8 8.0

20-30 ft 1.4 0.70 0 0.77 2.9

0-100 ft total 2.8 2.1 1.6 10 17

100-200 ft 2.5-5 ft 0.14 0.091 0.33 0 0.56

5-10 ft 0.54 1.3 1.7 6.4 9.9

10-20 ft 1.7 0.21 0 7 8.9

20-30 ft 0.5 0.35 0 5.9 6.8

100-200 ft total 2.8 1.9 2.0 19 26

200-500 ft 2.5-5 ft 0.40 0.65 3.7 1.8 6.5

5-10 ft 1.7 8.9 24 33 68

10-20 ft 15 23 46 33 120

20-30 ft 17 9.6 0 13 40

200-500 ft total 34 42 73 81 230

500-1,000 ft 2.5-5 ft 0 0 3.2 4.3 7.5

5-10 ft 0.45 2.8 13 28 45

10-20 ft 2.9 10 0.25 7.3 21

20-30 ft 1.8 6.9 0 0 8.6

500-1,000 ft total 5.1 20 17 40 82
Table HN-3. Ferris 25 coal resources—continued

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

1,000-1,500 ft 2.5-5 ft 0 0 0.051 2.6 2.7

5-10 ft 0.81 3.2 10 21 35

10-20 ft 0.23 0.13 0 0 0.36

1,000-1,500 ft total 1.0 3.4 11 23 38

1,500-2,000 ft 2.5-5 ft 0 0 0.010 1.2 1.2

5-10 ft 0 0.41 9.7 14 24

1,500-2,000 ft total 0 0.41 9.7 15 25

>2,000 ft 2.5-5 ft 0 0 0.0092 1.5 1.5

5-10 ft 0 0 29 90 120

>2,000 ft total 0 0 29 92 120

Grand total (MST) 46 70 140 280 540
Table HN-4. Coal resources of the Ferris 25 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

7.5-minute quadrangle (fig. HN-6) and Federal coal and surface ownership (fig. HN-8). Resources are reported in

millions of short tons (MST) with two significant figures. Table does not include resources for coal less than 2.5 ft

thick or coal in mine or lease areas (fig. HN-2). Resource numbers will not sum to match total due to independent

rounding

7.5-minute quadrangle map Federal ownership Total (MST)

DANA No Federal coal or surface ownership 52

No Federal coal, but Federal surface ownership 2.2

Federal coal, but no Federal surface ownership 2.6

Federal coal and surface ownership 36

DANA total 93

ELMO No Federal coal or surface ownership 0.63

Federal coal and surface ownership 0.25

ELMO total 0.88

HANNA No Federal coal or surface ownership 4.0

Federal coal, but no Federal surface ownership 0.54

Federal coal and surface ownership 3.0

HANNA total 7.6

PATS BOTTOM No Federal coal or surface ownership 120

No Federal coal, but Federal surface ownership 17

Federal coal and surface ownership 38

PATS BOTTOM total 180
Table HN-4. Ferris 25 coal resources—continued

7.5-minute quadrangle map Federal ownership Total (MST)

SCHNEIDER RIDGE No Federal coal or surface ownership 5.0

Federal coal and surface ownership 6.7

SCHNEIDER RIDGE total 12

SEMINOE DAM SE No Federal coal or surface ownership 74

Federal coal and surface ownership 73

SEMINOE DAM SE total 150

TENMILE SPRING No Federal coal or surface ownership 52

No Federal coal, but Federal surface ownership 4.1

Federal coal and Surface ownership 41

TENMILE SPRING total 97

WALCOTT No Federal coal or surface ownership 2.3

Federal coal and surface ownership 0.20

No Federal coal, but Federal surface ownership 1.4

WALCOTT total 3.8

Grand total Federal coal 200

Grand total (MST) 540
Table HN-5. Coal resources of the Ferris 31 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

overburden (fig. HN-14), net coal thickness (fig. HN-3), and reliability categories. Zeros (0) indicate areas where

no resources were calculated. Resources are reported in millions of short tons (MST) with two significant figures.

The table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN-3).

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

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

0-100 ft 2.5-5 ft 0.40 0.30 1.3 0.37 2.4

5-10 ft 0.087 0.33 6.0 0.92 7.3

10-20 ft 0 0 1.8 9.1 11

20-30 ft 0 0 0 1.3 1.3

0-100 ft total 0.49 0.63 9.1 12 22

100-200 ft 2.5-5 ft 0.094 0.035 0.021 0.36 0.51

5-10 ft 0.24 0.63 0.66 1.1 2.7

10-20 ft 0 0 0 7.2 7.2

20-30 ft 0 0 0 0.62 0.62

100-200 ft total 0.33 0.67 0.68 9.3 11

200-500 ft 2.5-5 ft 0.68 1.5 2.0 2.1 6.3

5-10 ft 0.60 1.9 5.4 34 42

10-20 ft 0 0 0 28 28

20-30 ft 0 0 0 7.3 7.3

200-500 ft total 1.3 3.4 7.4 71 83

500-1,000 ft 2.5-5 ft 0 0.57 0.31 0.56 1.4

5-10 ft 0 0.39 13 19 32

10-20 ft 0 0 0 20 20

20-30 ft 0 0 0 0.038 0.038

500-1,000 ft total 0 0.96 13 39 53
Table HN-5. Ferris 31 coal resources—continued

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

(MST)

1,000-1,500 ft 2.5-5 ft 0 0.0065 3.7 0.12 3.8

5-10 ft 0 0.063 9.7 12 22

10-20 ft 0 0 0 14 14

1,000-1,500 ft total 0 0.069 13 26 39

1,500-2,000 ft 2.5-5 ft 0 0.015 2.4 0.12 2.5

5-10 ft 0 0.036 2.6 10 13

10-20 ft 0 0 0 8.7 8.7

1,500-2,000 ft total 0 0.051 5.0 19 24

>2,000 ft 2.5-5 ft 0 0.012 0.26 3.6 3.8

5-10 ft 0 2.0 3.6 22 28

10-20 ft 0 0 0 4.1 4.1

>2,000 ft total (MST) 0 2.0 3.9 30 36

Grand total (MST) 2.1 7.8 53 210 270
Table HN-6. Coal resources of the Ferris 31 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

7.5-minute quadrangle (fig. HN-6) and Federal coal and surface ownership (fig. HN-9). Resources are reported in

millions of short tons (MST) with two significant figures. Table does not include resources for coal less than 2.5 ft

thick or coal in mine or lease areas (fig. HN-3). Resource numbers will not sum to match totals due to independent

rounding

7.5-minute quadrangle map Federal ownership Total (MST)

DANA No Federal coal or surface ownership 10

Federal coal and surface ownership 7.5

DANA total 18

PATS BOTTOM No Federal coal or surface ownership 93

No Federal coal, but Federal surface ownership 15

Federal coal and surface ownership 36

PATS BOTTOM total 140

SEMINOE DAM SE No Federal coal or surface ownership 25

Federal coal and surface ownership 23

SEMINOE DAM SE total 47

TENMILE SPRING No Federal coal or surface ownership 31

Federal coal and surface ownership 29

TENMILE SPRING total 60

WALCOTT No Federal coal or surface ownership 0.080

No Federal coal, but Federal surface ownership 0.36

WALCOTT total 0.44

Grand total of Federal coal (MST) 95

Grand total (MST) 270
Table HN-7. Coal resources of the Ferris 50 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

overburden (fig. HN-15), net coal thickness (fig. HN-4), and reliability categories. Zeros (0) indicate areas where

no resources were calculated. Resources are reported in millions of short tons (MST) with two significant figures.

The table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN-4).

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

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

0-100 ft 2.5-5 ft 0.36 2.1 3.4 2.4 8.3

5-10 ft 0.35 0.76 7.7 16 25

10-20 ft 2.3 12 19 1.5 34

0-100 ft total 3.0 15 30 20 67

100-200 ft 2.5-5 ft 0.14 0.39 0.8 1.5 2.8

5-10 ft 1.0 1.4 2.5 1.8 6.7

10-20 ft 0.89 3.4 4.8 0.82 9.9

100-200 ft total 2.0 5.2 8.1 4.1 19

200-500 ft 2.5-5 ft 0.50 0.91 1.1 0.072 2.6

5-10 ft 0.58 6.6 13 3.1 24

10-20 ft 1.8 6.3 8.6 0.25 17

200-500 ft total 2.8 14 23 3.4 43

500-1,000 ft 2.5-5 ft 0.012 0.13 0.049 0.044 0.24

5-10 ft 1.1 7.6 16 0.061 25

10-20 ft 1.9 11 21 0.18 34

500-1,000 ft total 3.1 19 36 0.28 59

1,000-1,500 ft 2.5-5 ft 0 0 0 0.033 0.033

5-10 ft 2.3 3.7 1.6 0.0016 7.6

10-20 ft 0.30 7.8 39 0.19 47

1,000-1,500 ft total 2.6 11 40 0.22 55
Table HN-7 Ferris 50 coal resources—continued

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

1,500-2,000 ft 2.5-5 ft 0 0 0 0.013 0.013

5-10 ft 0.091 4.3 0.029 0 4.4

10-20 ft 0 4.4 39 3.3 46

1,500-2,000 ft total 0.091 8.7 39 3.3 51

>2,000 ft 2.5-5 ft 0 0 0 0.0071 0.0071

5-10 ft 0 0.0056 0.025 0 0.031

10-20 ft 0 0.80 160 49 210

>2,000 ft total 0 0.80 160 49 210

Grand total (MST) 14 73 340 80 510
Table HN-8. Coal resources of the Ferris 50 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

7.5-minute quadrangle (fig. HN-6) and Federal coal and surface ownership (fig. HN-10). Resources are reported in

millions of short tons (MST) with two significant figures. Table does not include resources for coal less than 2.5 ft

thick or coal in mine or lease areas (fig. HN-4). Resource numbers will not sum to match totals due to independent

rounding

7.5-minute quadrangle map Federal ownership Total (MST)

DANA No Federal coal or surface ownership 36

No Federal coal, but Federal surface ownership 6.0

Federal coal, but no Federal surface ownership 3.2

Federal coal and surface ownership 15

DANA total 61

ELMO No Federal coal or surface ownership 4.2

Federal coal and surface ownership 1.5

ELMO total 5.7

HANNA No Federal coal or surface ownership 7.2

Federal coal, but no Federal surface ownership 1.3

Federal coal and surface ownership 5.0

HANNA total 14

PATS BOTTOM No Federal coal or surface ownership 62

No Federal coal, but Federal surface ownership 1.1

Federal coal and surface ownership 35

PATS BOTTOM total 97

TENMILE SPRING No Federal coal or surface ownership 190

No Federal coal, but Federal surface ownership 10

Federal coal and surface ownership 130

TENMILE SPRING total 330

Grand total of Federal coal 190

Grand total (MST) 510
 Table HN-9. Coal resources of the Ferris 65 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported by

overburden (fig. HN-16), net coal thickness (fig. HN-5), and reliability categories. Zeros (0) indicate areas where

no resources were calculated. Resources are reported in millions of short tons (MST) with two significant figures.

The table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN-5).

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

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

0-100 ft 2.5-5 ft 0.27 1.6 0.35 0 2.2

5-10 ft 4.1 11 2.4 0 17

10-20 ft 0.79 4.8 0 0 5.6

0-100 ft total 5.2 17 2.7 0 25

100-200 ft 2.5-5 ft 0.23 1.3 0.65 0 2.1

5-10 ft 0.4 6.9 3.5 0 11

10-20 ft 1.0 2.6 0 0 3.7

100-200 ft total 1.7 11 4.2 0 17

200-500 ft 2.5-5 ft 1.1 3.8 9.0 0 14

5-10 ft 0.91 7.2 54 0.98 64

10-20 ft 4.9 5.1 1.1 0 11

200-500 ft total 6.9 16 65 0.98 88

500-1,000 ft 2.5-5 ft 0.075 0.62 7.4 0 8.1

5-10 ft 1.5 2.5 40 0 44

10-20 ft 4.3 6.5 0 0 11

500-1,000 ft total 5.9 9.6 47 0 63

1,000-1,500 ft 5-10 ft 0 0 4.6 0 4.6

1,000-1,500 ft total 0 0 4.6 0 4.6

Grand total (MST) 20 54 120 0.98 200
Table HN-10. Coal resources of the Ferris 65 coal zone in the Ferris coalfield, Hanna Basin, Wyoming, reported

by 7.5-minute quadrangle map area (fig. HN-6) and Federal coal and surface ownership (fig. HN-11). Resources

are reported in millions of short tons (MST) with two significant figures. The table does not include resources for

coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN-5). Resource numbers will not sum to match totals

due to independent rounding

7.5-minute quadrangle map Federal ownership Total (MST)

DANA No Federal coal or surface ownership 6.7

No Federal coal, but Federal surface ownership 0.39

Federal coal, but no Federal surface ownership 0.16

Federal coal and surface ownership 3.3

DANA total 11

ELMO No Federal coal or surface ownership 1.5

Federal coal and surface ownership 0.94

ELMO total 2.5

HANNA No Federal coal or surface ownership 6.4

Federal coal, but no Federal surface ownership 0.093

Federal coal and surface ownership 5.1

HANNA total 12

PATS BOTTOM No Federal coal or surface ownership 18

No Federal coal, but Federal surface ownership 0.11

Federal coal and surface ownership 7.6

PATS BOTTOM total 25

TENMILE SPRING No Federal coal or surface ownership 86

No Federal coal, but Federal surface ownership 1.4

Federal coal and surface ownership 61

TENMILE SPRING total 150

Grand total of Federal coal 78

Grand total (MST) 200
Table HN-11. Parameters and confidence intervals within reliability categories for Ferris 23 coal resources, Ferris

coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error. Volume

refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are reported

using four significant figures. NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 6,116,176 12,591,713 46,035,986 36,008,928 100,752,804

Percent of area 6 12 46 36 100

Acres (area x .0002471) 1,511 3,111 11,376 8,898 24,897

SD (standard deviation (in ft) from

semivariogram model)

2.000 3.464 6.325 6.325 NA

Acre feet (acres x SD) 3,023 10,778 71,946 56,276 NA

Volume standard deviation (MST) 2 12 161 100 273

Pseudo n 12 3 1 1 NA

Total calculated resource (MST) 22.60 38.00 109.3 64.00 233.8

Lower 90% confidence limit (MST) 20.00 19.00 0 0 0

Upper 90% confidence limit (MST) 25.00 57.00 374.0 228.0 683.0
Table HN-12. Parameters and confidence intervals within reliability categories for Ferris 25 coal resources, Ferris

coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error. Volume

refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are reported

using four significant figures. NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 6,563,920 12,895,672 40,318,426 89,497,646 149,275,664

Percent of area 4 9 27 60 100

Acres (area x 0.0002471) 1,622 3,187 9,963 22,115 36,887

SD (standard deviation (in ft) from

semivariogram model)

4.705 5.141 6.760 6.760 NA

Acre feet (acres x SD) 7,632 16,382 67,351 149,504 NA

Volume standard deviation (MST) 4 17 161 265 446

Pseudo n 13 3 1 1 NA

Volume (MST) 45.60 70.10 142.2 281.8 539.7

Lower 90% confidence limit (MST) 39.00 42.00 0 0 0

Upper 90% confidence limit (MST) 52.00 99.00 407.0 717.0 1,274
Table HN-13. Parameters and confidence intervals within reliability categories for Ferris 31 coal resources, Ferris

coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error. Volume

refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are reported

using four significant figures. NA, not applicable

Parameter Reliability Category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 1,023,193 3,264,636 20,455,234 51,626,255 76,369,319

Percent of area 1 4 27 68 100

Acres (area x 0.0002471) 253 807 5,055 12,757 18,871

SD (standard deviation (in ft) from data) 2.241 2.241 2.241 2.241 NA

Acre feet (acres x SD) 567 1,808 11,328 28,591 NA

Volume standard deviation (MST) 1 4 38 51 93

Pseudo n 2.0 0.7 0.3 1.0 NA

Volume (MST) 2.095 7.832 52.89 206.1 268.9

Lower 90% confidence limit (MST) 0.9300 1.600 0 122.9 115.9

Upper 90% confidence limit (MST) 3.260 14.07 115.3 289.4 422.0
Table HN-14. Parameters and confidence intervals within reliability categories for Ferris 50 coal resources, Ferris

coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error. Volume

refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are reported

using four significant figures. NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 3,330,441 16,842,693 60,894,465 17,082,509 98,150,108

Percent of area 3 17 62 17 100

Acres (area x 0.0002471) 823 4,162 15,047 4,221 24,253

SD (standard deviation (in ft) from data) 3.438 3,438 3.438 3.438 NA

Acre feet (acres x SD) 2,830 14,310 51,739 14,514 NA

Volume standard deviation (MST) 2 13 100 26 141

Pseudo n 6.5 3.7 0.8 1.0 NA

Volume (MST) 13.61 73.43 338.2 80.31 505.5

Lower 90% confidence limit (MST) 10.39 51.71 173.0 38.05 273.1

Upper 90% confidence limit (MST) 16.83 95.15 503.4 122.6 737.9
Table HN-15. Parameters and confidence intervals within reliability categories for Ferris 65 coal resources, Ferris

coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error. Volume

refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are reported

using four significant figures. NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 5,417,001 17,736,198 44,443,346 352,117 67,948,662

Percent of area 8 26 65 1 100

Acres (area x 0.0002471) 1,339 4,383 10,982 87 16,790

SD (standard deviation (in ft) from data) 2.469 2.469 2.469 2.469 NA

Acre feet (acres x SD) 3,305 10,820 27,113 215 NA

Volume standard deviation (MST) 2 10 62 0 74

Pseudo n 10.7 3.9 0.6 1.0 NA

Volume (MST) 19.65 53.66 123.5 0.980 197.8

Lower 90% confidence limit (MST) 16.70 37.66 22.18 0.3600 76.90

Upper 90% confidence limit (MST) 22.60 69.67 224.9 1.610 318.7
Table HN-16. Coal resources of the Hanna 77 coal zone in the Hanna coalfield, Hanna Basin, Wyoming, reported

by overburden (fig. HN-26), net coal thickness (fig. HN-17), and reliability categories. Zeros (0) indicate areas

where no resources were calculated. Resources are reported in millions of short tons (MST) with two significant

figures. The table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN17). Resource numbers will not sum to match totals due to independent rounding

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

0-100 ft 10-20 ft 0.55 3.0 6.2 2.8 13

40-50 ft 0.51 0.17 15 19 34

0-100 ft total 1.1 3.2 21 22 47

100-200 ft 5-10 ft 0 0.0034 0 0 0.0034

10-20 ft 1.1 7.4 7.7 4.4 21

40-50 ft 2.1 0.29 21 28 51

100-200 ft total 3.2 7.7 29 32 72

200-300 ft 5-10 ft 0 0.16 0 0 0.16

10-20 ft 1.7 8.3 7.7 3.8 21

30-40 ft 0.078 0 0 0 0.078

40-50 ft 2.5 1.4 21 28 54

200-300 ft total 4.3 10 29 32 75

300-400 ft 5-10 ft 0 0.17 0 0 0.17

10-20 ft 3.9 6.3 7.2 3.1 20

30-40 ft 0.43 0 0 0 0.43

40-50 ft 1.9 3.8 23 21 50

300-400 ft total 6.3 10 30 24 71

400-500 ft 10-20 ft 0.42 3.4 6.3 2.5 13

30-40 ft 0.046 0 0 0 0.046

40-50 ft 0.36 6.6 24 13 44

400-500 ft total 0.83 9.9 31 15 57

500-1,000 ft 10-20 ft 0.011 1.0 14 10 25

40-50 ft 0 18 140 21 180

500-1,000 ft total 0.011 19 150 31 200
Table HN-16. Hanna 77 coal resources—continued

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

1,000-1,500 ft 10-20 ft 0.94 0.83 4.5 4.0 10

20-40 ft 0 0 1.8 0.55 2.4

40-50 ft 0.20 2.6 120 3.4 130

1,000-1,500 ft total 1.1 3.4 130 8.0 140

1500-2,000 ft 5-10 ft 0.063 0 0 0 0.063

10-20 ft 0.99 2.0 0.69 0.27 3.9

20-40 ft 0 0 7.5 0 7.5

40-50 ft 0 0 100 0 100

1,500-2,000 ft total 1.1 2 110 0.27 120

>2,000 ft 10-20 ft 0.3 4.4 0.22 0 4.9

20-30 ft 0 0.87 0.86 0 1.7

30-40 ft 0 0.61 51 0 52

40-50 ft 10 100 570 0 680

50-100 ft 12 55 11 0 78

>2,000 ft total 23 160 630 0 810

Grand total (MST) 40 230 1,200 160 1,600
Table HN-17. Coal resources of the Hanna 77 coal zone in the Hanna coalfield, Hanna Basin, Wyoming, reported

by 7.5-minute quadrangle (fig. HN-21) and Federal coal and surface ownership (fig. HN-22). Resources are

reported in millions of short tons (MST) with two significant figures. Table does not include resources for coal

less than 2.5 ft thick or coal in mine or lease areas (fig. HN-17). Resource numbers will not sum to match totals

due to independent rounding

7.5-minute quadrangle map Federal ownership Total (MST)

COMO WEST No Federal coal or surface ownership 490

Federal coal, but no Federal surface ownership 9.9

Federal coal and surface ownership 340

COMO WEST total 830

DIFFICULTY No Federal coal or surface ownership 150

Federal coal, but no Federal surface ownership 18

Federal coal and surface ownership 8.9

DIFFICULTY total 180

ELMO No Federal coal or surface ownership 290

Federal coal, but no Federal surface ownership 0.86

Federal coal and Federal surface ownership 150

ELMO total 440

HANNA No Federal coal or surface ownership 47

Federal coal and surface ownership 0.45

HANNA total 47

T E RANCH No Federal coal or surface ownership 44

Federal coal, but no Federal surface ownership 16

Federal coal and surface ownership 34

T E RANCH total 94

Grand total Federal coal 580

Grand total (MST) 1,600
Table HN-18. Coal resources of the Hanna 78 coal zone in the Hanna coalfield, Hanna Basin, Wyoming, reported

by overburden (fig. HN-27), net coal thickness (fig. HN-18), and reliability categories. Zeros (0) indicate areas

where no resources were calculated. Resources are reported in millions of short tons (MST) with two significant

figures. The table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN18). Resource numbers will not sum to match totals due to independent rounding

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

0-100 ft 2.5-5 ft 0.018 0 0 0 0.018

5-10 ft 0.32 0.27 0 0 0.59

10-20 ft 2.1 2.9 3.4 0 8.3

20-30 ft 4.4 0 0.68 1.4 6.5

30-40 ft 8.3 7.0 9.2 5.2 30

0-100 ft total 15 10 13 6.6 45

100-200 ft 2.5-5 ft 0.055 0 0 0 0.055

5-10 ft 1.3 0.79 0 0 2.1

10-20 ft 3.2 0.84 2.5 0 6.5

20-30 ft 6.9 0.69 3.9 3.2 15

30-40 ft 11 4.2 14 7.7 37

100-200 ft total 22 6.6 21 11 60

200-300 ft 2.5-5 ft 0.059 0 0 0 0.059

5-10 ft 1.0 0.85 0 0 1.9

10-20 ft 4.0 1.1 2.1 0 7.2

20-30 ft 4.7 2.7 5.1 3 16

30-40 ft 7.3 1.5 13 6.3 28

200-300 ft total 17 6.2 20 9.2 53

300-400 ft 2.5-5 ft 0.075 0 0 0 0.075

5-10 ft 0.67 0.93 0 0 1.6

10-20 ft 3.4 2.1 1.8 0 7.3

20-30 ft 4.2 4.7 5.9 2.3 17

30-40 ft 5.7 0.43 13 5.1 24

300-400 ft total 14 8.1 21 7.4 50
Table HN-18. Hanna 78 coal resources—continued

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

400-500 ft 2.5-5 ft 0.027 0.002 0 0 0.029

5-10 ft 0.26 0.82 0 0 1.1

10-20 ft 2.7 4.0 1.6 0 8.4

20-30 ft 4.0 2.5 7.6 1.4 15

30-40 ft 4.8 0.92 11 4.6 22

400-500 ft total 12 8.3 20 6 47

500-1,000 ft 5-10 ft 0.098 5.0 6.3 0 11

10-20 ft 7.0 11 11 0 29

20-30 ft 7.9 9.0 33 1.2 51

30-40 ft 16 13 41 24 93

500-1,000 ft total 31 38 91 25 180

1,000-1,500 ft 5-10 ft 0 0 0.61 0 0.61

10-20 ft 0.12 0.57 15 0 16

20-30 ft 0.74 4.1 14 0 19

30-40 ft 1.7 13 37 9 60

1,000-1,500 ft total 2.5 18 67 9 96

1,500-2,000 ft 10-20 ft 0 0 10 0 10

20-30 ft 0.085 4.1 12 0 16

30-40 ft 1.3 13 45 4.4 64

1,500-2,000 ft total 1.4 17 67 4.4 90

>2,000 ft 10-20 ft 0.19 6.9 30 0 37

20-30 ft 0.64 27 56 0 83

30-40 ft 11 83 290 0 380

40-50 ft 3.3 18 2.5 0 24

>2,000 ft total 15 130 370 0 520

Grand total (MST) 130 250 690 79 1,100
Table HN-19. Coal resources of the Hanna 78 coal zone in the Hanna coalfield, Hanna Basin, Wyoming, reported

by 7.5-minute quadrangle (fig. HN-21) and Federal coal and surface ownership (fig. HN-23). Resources are

reported in millions of short tons (MST) with two significant figures. Table does not include resources for coal

less than 2.5 ft thick or coal in mine or lease areas (fig. HN-18). Resource numbers will not sum to match totals

due to independent rounding

7.5-minute quadrangle map Federal ownership Total (MST)

COMO WEST No Federal coal or surface ownership 250

Federal coal and surface ownership 170

COMO WEST total 420

DIFFICULTY No Federal coal or surface ownership 130

Federal coal and surface ownership 21

DIFFICULTY total 150

ELMO No Federal coal or surface ownership 280

Federal coal and surface ownership 120

ELMO total 390

HANNA No Federal coal or surface ownership 90

Federal coal and surface ownership 0.80

HANNA total 90

T E RANCH No Federal coal or surface ownership 44

Federal coal and surface ownership 51

T E RANCH total 95

Grand total Federal coal 360

Grand total (MST) 1,100
Table HN-20. Coal resources of the Hanna 79 coal zone in the Hanna coalfield, Hanna Basin, Wyoming, reported

by overburden (fig. HN-28), net coal thickness (fig. HN-19), and reliability categories. Zeros (0) indicate areas

where no resources were calculated. Resources are reported in millions of short tons (MST) with two significant

figures. The table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN19). Resource numbers will not sum to match totals due to independent rounding

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

0-100 ft 2.5-5 ft 0.0090 0 0 0 0.0090

5-10 ft 0.42 0.35 0 0 0.78

10-20 ft 6.6 1.8 0.15 0 8.6

20-30 ft 0.41 0 0 0 0.41

30-40 ft 12 3.9 5.1 1.4 22

0-100 ft total 19 6.0 5.3 1.4 32

100-200 ft 5-10 ft 0.32 0.29 0 0 0.61

10-20 ft 12 0.24 0.66 0 13

20-30 ft 0.31 0 0 0 0.31

30-40 ft 6.7 2.4 14 3.8 27

100-200 ft total 19 14 3.8 40

200-300 ft 5-10 ft 0.049 0.089 0 0 0.14

10-20 ft 9.2 1.3 0.78 0 11

30-40 ft 1.1 7.0 15 3.6 26

200-300 ft total 10 8.4 15 3.6 38

300-400 ft 10-20 ft 5.4 4.7 0.37 0 10

30-40 ft 0.42 6.6 16 2.9 26

300-400 ft total 5.8 11 16 2.9 36

400-500 ft 10-20 ft 1.6 6.4 0.083 0 8.1

30-40 ft 0.45 5.7 15 2.8 24

400-500 ft total 2.1 12 15 2.8 32

500-1,000 ft 10-20 ft 0.035 5.6 6.9 0 13

30-40 ft 1.5 7.4 79 10 99

500-1,000 ft total 1.5 13 86 10 110
Table HN-20. Hanna 79 coal resources—continued

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

1,000-1,500 ft 10-20 ft 0 2.0 4.1 0 6.1

30-40 ft 1.7 4.7 61 5.6 73

1,000-1,500 ft total 1.7 6.6 65 5.6 79

1,500-2,000 ft 5-10 ft 0 0 1.1 0 1.1

10-20 ft 0 0.73 3.5 0 4.3

30-40 ft 0.98 14 55 3.7 74

1,500-2,000 ft total 0.98 14 60 3.7 79

>2,000 ft 5-10 ft 0 0 0.23 0 0.23

10-20 ft 0 0.85 9.1 0 9.9

30-40 ft 12 100 320 0 440

>2,000 ft total 12 110 330 0 450

Grand total (MST) 73 180 610 34 900
Table HN-21. Coal resources of the Hanna 79 coal zone in the Hanna coalfield, Hanna Basin, Wyoming, reported

by 7.5-minute quadrangle (fig. HN-21) and Federal coal and surface ownership (fig. HN-24). Resources are

reported in millions of short tons (MST) with two significant figures. Table does not include resources for coal

less than 2.5 ft thick or coal in mine or lease areas (fig. HN-19). Resource numbers will not sum to match totals

due to independent rounding

7.5-minute quadrangle map Federal ownership Total (MST)

COMO WEST No Federal coal or surface ownership 240

Federal coal, but no Federal surface ownership 7.5

Federal coal and surface ownership 190

COMO WEST total 440

DIFFICULTY No Federal coal or surface ownership 130

Federal coal, but no Federal surface ownership 17

Federal coal and surface ownership 2.7

DIFFICULTY total 150

ELMO No Federal coal or surface ownership 150

Federal coal, but no Federal surface ownership 0.52

Federal coal and surface ownership 78

ELMO total 230

T E RANCH No Federal coal or surface ownership 35

Federal coal, but no Federal surface ownership 11

Federal coal and surface ownership 30

T E RANCH total 76

Grand total Federal coal 340

Grand total (MST) 900
Table HN-22. Coal resources of the Hanna 81 coal zone in the Hanna coalfield, Hanna Basin, Wyoming, reported

by overburden (fig. HN-29), net coal thickness (fig. HN-20), and reliability categories. Zeros (0) indicate areas

where no resources were calculated. Resources are reported in millions of short tons (MST) with two significant

figures. The table does not include resources for coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN20). Resource numbers will not sum to match totals due to independent rounding

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

0-100 ft 2.5-5 ft 0.10 1.2 0 0 1.3

5-10 ft 0.86 0.31 0 0 1.2

10-20 ft 2.0 0.053 0 0 2.0

30-40 ft 14 10 36 3.2 64

0-100 ft total 17 12 36 3.2 68

100-200 ft 2.5-5 ft 0.00084 0.56 0.16 0 0.72

5-10 ft 0.0098 0.74 0.086 0 0.84

10-20 ft 0.40 0.50 0 0 0.90

30-40 ft 7.1 16 22 3.9 49

100-200 ft total 7.5 18 22 3.9 51

200-300 ft 2.5-5 ft 0 0.40 0.52 0 0.93

5-10 ft 0 0.39 0.40 0 0.79

10-20 ft 0.37 0.68 0.33 0 1.4

30-40 ft 3.9 13 17 3.1 37

200-300 ft total 4.3 14 18 3.1 40

300-400 ft 2.5-5 ft 0 0.18 0.92 0 1.1

5-10 ft 0 0.41 0.43 0 0.84

10-20 ft 0.20 0.74 0.77 0 1.7

30-40 ft 3.3 7.5 14 2.4 27

300-400 ft total 3.5 8.9 16 2.4 31

400-500 ft 2.5-5 ft 0 0.0049 0.73 0 0.73

5-10 ft 0 0.35 0.56 0 0.91

10-20 ft 0.045 1.0 0.70 0 1.7

30-40 ft 2.9 5.1 11 1.9 21

400-500 ft total 3.0 6.4 13 1.9 25
Table HN-22. Hanna 81 coal resources—continued

Overburden Net coal Reliability category (distance from data point) Total

thickness thickness Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

Hypothetical

(>3 mi)

 (MST)

500-1,000 ft 2.5-5 ft 0 0 0.11 0 0.11

5-10 ft 0 0.26 3.3 0 3.5

10-20 ft 0.27 5.3 3.8 0 9.4

30-40 ft 1.2 2.1 48 3.3 54

500-1,000 ft total 1.5 7.6 55 3.3 67

1,000-1,500 ft 10-20 ft 0.017 7.7 8.5 0 16

30-40 ft 0.17 1.4 43 0 45

1,000-1,500 ft total 0.18 9.1 52 0 61

1,500-2,000 ft 10-20 ft 0.0051 3.9 3.9 0 7.8

30-40 ft 0.42 4.6 50 0 55

1,500-2,000 ft total 0.43 8.5 54 0 63

>2,000 ft 5-10 ft 0 0 0.016 0 0.016

10-20 ft 0 2.3 8.0 0 10

20-30 ft 0 0 0.43 0 0.43

30-40 ft 10 71 170 0 250

>2,000 ft total 10 73 170 0 260

Grand total (MST) 47 160 440 18 660
Table HN-23. Coal resources of the Hanna 81 coal zone in the Hanna coalfield, Hanna Basin, Wyoming, reported

by 7.5-minute quadrangle (fig. HN-21) and Federal coal and surface ownership (fig. HN-25). Resources are

reported in millions of short tons (MST) and in two significant figures. Table does not include resources for coal

less than 2.5 ft thick or coal in mine or lease areas (fig. HN-20). Resource numbers will not sum to match totals

due to independent rounding

7.5-minute quadrangle map Federal ownership Total (MST)

COMO WEST No Federal coal or surface ownership 150

Federal coal and surface ownership 160

COMO WEST total 310

DIFFICULTY No Federal coal or surface ownership 100

Federal coal and surface ownership 0.089

DIFFICULTY total 100

ELMO No Federal coal or Federal surface ownership 87

Federal coal and Federal surface ownership 47

ELMO total 130

HANNA No Federal coal or surface ownership 87

Federal coal and surface ownership 0.42

HANNA total 87

T E RANCH No Federal coal or surface ownership 17

Federal coal and surface ownership 13

T E RANCH total 30

Grand total of Federal coal 160

Grand total (MST) 660
Table HN-24. Parameters and confidence intervals within reliability categories for Hanna 77 coal resources,

Hanna coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error.

Volume refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are

reported using four significant figures. NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 4,466,516 20,546,927 89,799,994 16,425,438 131,238,875

Percent of area 3 16 68 13 100

Acres (area x 0.0002471) 1,104 5,077 22,190 4,059 32,430

SD (standard deviation (in ft) derived

directly from the data)

9.894 9.894 9.894 9.894 NA

Acre feet (acres x SD) 10,920 50,236 219,555 40,159 NA

Volume standard deviation (MST) 7 42 351 71 471

Pseudo n 9 4 1 1 NA

Total calculated resource (MST) 40.43 225.7 1,162 164.9 1,593

Lower 90% confidence limit (MST) 30.00 157.0 585.0 48.00 819.0

Upper 90% confidence limit (MST) 51.00 295.0 1,740 282.0 2,367
Table HN-25. Parameters and confidence intervals within reliability categories for Hanna 78 coal resources,

Hanna coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error.

Volume refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are

reported using four significant figures. NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 17,355,245 27,276,139 71,020,583 9,390,185 125,042,152

Percent of area 14 22 57 8 100

Acres (Area x 0.0002471) 4,289 6,740 17,550 2,320 30,899

SD (Standard deviation (in ft) derived

directly from the data)

6.827 6.827 6.827 6.827 NA

Acre feet (Acres x SD) 29,279 46,017 119,816 15,842 NA

Volume standard deviation (MST) 9 33 215 28 286

Pseudo n 34 6 1 1 NA

Total calculated resource (MST) 129.9 247.1 692.5 78.73 1,148

Lower 90% confidence limit (MST) 115.0 192.0 338.0 33.00 678.0

Upper 90% confidence limit (MST) 144.0 302.0 1,047 125.0 1,618
Table HN-26. Parameters and confidence intervals within reliability categories for Hanna 79 coal resources,

Hanna coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error.

Volume refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are

reported using four significant figures. NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 13,615,932 23,226,193 58,562,863 2,157,339 97,562,328

Percent of area 14 24 60 2 100

Acres (area x 0.0002471) 3,365 5,739 14,471 533 24,108

SD (standard deviation (in ft) derived

directly from the data)

4.147 4.147 4.147 4.147 NA

Acre feet (acres x SD) 13,953 23,801 60,012 2,211 NA

Volume standard deviation (MST) 5 19 119 4 146

Pseudo n 27 5 1 1 NA

Total calculated resource (MST) 73.27 180.6 607.2 34.17 895.2

Lower 90% confidence limit (MST) 65.00 150.0 412.0 28.00 655.0

Upper 90% confidence limit (MST) 81.00 211.0 803.0 41.00 1,136
Table HN-27. Parameters and confidence intervals within reliability categories for Hanna 81 coal resources,

Hanna coalfield, Hanna Basin, Wyoming. Estimates of uncertainty were calculated with measurement error.

Volume refers to the calculated resource in millions of short tons (MST). To show detail, resources in this table are

reported using four significant figures. NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred Hypothetical area

Area (in square meters) 6,030,945 23,789,170 60,454,785 1,459,792 91.734,691

Percent of area 7 26 66 2 100

Acres (area x 0.0002471) 1,490 5,878 14,939 361 22,668

SD (standard deviation (in ft) derived

directly from the data)

7.145 7.145 7.145 7.145 NA

Acre feet (Acres x SD) 10,648 42,000 106,734 2,577 NA

Volume standard deviation (MST) 5 33 208 5 251

Pseudo n 12 5 1 1 NA

Total calculated resource (MST) 47.52 158.1 443.0 17.61 666.2

Lower 90% confidence limit (MST) 39.00 104.0 101.0 10.00 254.0

Upper 90% confidence limit (MST) 57.00 212.0 785.0 25.00 1,078
Table HN-28. Coal resources of the Johnson-107 coal zone in the South Carbon coalfield, Wyoming, reported by

overburden (fig. HN-33), net coal thickness (fig. HN-32), and reliability categories. Zeros (0) indicate areas where

no resources were calculated. Resources are reported in millions of short tons (MST) with two significant figures.

Resources do not include coal less than 2.5 ft thick or coal in mine or lease areas (fig. HN-32). Resource numbers

will not sum to match totals due to independent rounding

Overburden Net coal Reliability category (distance from data point) Grand total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

 (MST)

0-100 ft 2.5-5 ft 0 0.053 0 0.053

5-10 ft 0.78 4.9 1.5 7.3

10-20 ft 2.0 8.9 3.3 14

20-30 ft 2.0 21 5.5 28

30-40 ft 0 8.1 6.1 14

>40 ft 0 71 120 190

0-100 ft total 4.8 110 130 250

100-200 ft 2.5-5 ft 0.022 0.036 0 0.059

5-10 ft 1.2 1.3 0.31 2.8

10-20 ft 0.48 5.5 3.6 9.6

20-30 ft 0.63 9.1 0.34 10

30-40 ft 0 6.8 4.8 12

>40 ft 3.4 41 39 84

100-200 ft total 5.8 64 49 120

200-300 ft 2.5-5 ft 0.044 0.011 0 0.055

5-10 ft 1.0 0.064 0 1.1

10-20 ft 0.52 1.6 0.27 2.4

20-30 ft 0.62 6.7 0.77 8.1

30-40 ft 0 7.5 3.6 11

>40 ft 4.1 57 64 130

200-300 ft total 6.3 73 69 150
Table HN-28. Johnson-107 coal resources—continued

Overburden Net coal Reliability category (distance from data point) Grand total

thickness thickness Measured

 (<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

 (MST)

300-400 ft 2.5-5 ft 0.11 0.0003 0 0.11

5-10 ft 0.89 0.65 0 1.5

10-20 ft 2.5 6.5 0 9.0

20-30 ft 0.25 11 0.63 12

30-40 ft 0.24 9.4 0.17 9.8

>40 ft 5.2 130 49 190

300-400 ft total 9.2 160 50 220

400-500 ft 2.5-5 ft 0.21 0 0 0.21

5-10 ft 1.7 1.9 0 3.6

10-20 ft 3.4 8.4 0 12

20-30 ft 1.7 0.9 0 2.6

30-40 ft 3.2 0.59 0 3.8

>40 ft 48 99 0.37 150

400-500 ft total 58 110 0.37 170

>500 ft 2.5-5 ft 0.61 0.36 0 0.97

5-10 ft 1.7 3.6 0.48 5.9

10-20 ft 0.34 18 0.18 19

20-30 ft 4.8 11 0 16

30-40 ft 1.7 19 0 21

>40 ft 48 130 0 170

>500 ft total 57 180 0.66 240

Grand total (MST) 140 700 300 1,100
Table HN-29. Coal resources of the Johnson-107 coal zone in the South Carbon coalfield, Wyoming, reported by

7.5-minute quadrangle map area (fig. HN-30) and Federal coal and surface ownership (fig HN-31). Resources are

reported in millions of short tons (MST) with two significant figures. Resources do not include coal less than 2.5 ft

thick or coal in mine or lease areas (fig. HN-32). Resource numbers will not sum to match totals due to

independent rounding

7.5-minute quadrangle map Federal ownership Total (MST)

CARBON No Federal coal or surface ownership 410

Federal coal, but no Federal surface ownership 20

Federal coal and surface ownership 48

CARBON total 470

ELK MOUNTAIN No Federal coal or surface ownership 40

Federal coal, but no Federal surface ownership 0.69

Federal coal and surface ownership 0.65

ELK MOUNTAIN total 41

HALFWAY HILL No Federal coal or surface ownership 420

Federal coal, but no Federal surface ownership 3.4

Federal coal and surface ownership 140

HALFWAY HILL total 560

T L RANCH No Federal coal or surface ownership 66

Federal coal, but no Federal surface ownership 0.37

Federal coal and surface ownership 0.095

T L RANCH total 66

Grand total of Federal coal 210

Grand total (MST) 1,100
Table HN-30. Data used for computation of confidence intervals within reliability categories for Johnson-107 coal

resources in the South Carbon coalfield, Carbon Basin, Wyoming. Volume refers to the calculated resource in

millions of short tons (MST). NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred area

Area (in square meters) 9,114,330 37,519,215 12,687,826 59,321,371

Percent of area 15 63 21 100

Acres (area x 0.0002471) 2,252 9,271 3,135 14,659

SD (standard deviation (in ft) from variogram model) 13.780 13.780 13.780 NA

Acre feet (acres x SD) 31,035 127,757 43,203 NA

Volume standard deviation (MST) 13 79 184 276

Pseudo n 18 8 0.17 NA

Table HN-31. Estimates of uncertainty (calculated with measurement error) for Johnson-107 coal resources in the

South Carbon coalfield, Carbon Basin, Wyoming. To show detail, resources calculations are reported in millions of

short tons (MST) with four significant figures

Parameter Reliability category Entire

Measured Indicated Inferred area

Total calculated resource (MST) 141.0 698.5 300.6 1,140

Lower 90% confidence limit (MST) 120.0 569.0 0 687.0

Upper 90% confidence limit (MST) 162.0 828.0 603.0 1,594