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Assessment of Coal Geology, Resources, and Reserves in the Northern Wyoming Powder River Basin

Open-File Report 2010–1294

U.S. Department of the Interior U.S. Geological Survey

Assessment of Coal Geology, Resources, and Reserves in the Northern Wyoming Powder River Basin
By David C. Scott, Jon E. Haacke, Lee M. Osmonson, James A. Luppens, Paul E. Pierce, and Timothy J. Rohrbacher

Open-File Report 2010–1294

U.S. Department of the Interior U.S. Geological Survey

U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

This and other USGS information products are available at http://store.usgs.gov/ U.S. Geological Survey Box 25286, Denver Federal Center Denver, CO 80225 To learn about the USGS and its information products visit http://www.usgs.gov/ 1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.

Suggested citation: Scott, D.C., Haacke, J.E., Osmonson, L.M., Luppens, J.A., Pierce, P.E., and Rohrbacher, T.J., 2011, Assessment of coal geology, resources, and reserves in the northern Wyoming Powder River Basin: U.S. Geological Survey Open-File Report 2010–1294, 136 p.

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Contents
Abstract ...........................................................................................................................................................1 Introduction and Objectives .........................................................................................................................1 Previous Coal Resource Estimates .............................................................................................................2 Previous and Proposed Coal Mining ..........................................................................................................2 Other Energy Commodities ...........................................................................................................................3 Study Methodology........................................................................................................................................4 Data Collection ...............................................................................................................................................4 Coal Bed Nomenclature ......................................................................................................................5 Coal Bed Correlations ..........................................................................................................................5 Geologic Setting ....................................................................................................................................6 Geologic Modeling.........................................................................................................................................6 Influence of Geology in Coal Bed Correlations .........................................................................................7 Faults .......................................................................................................................................................7 Paleochannel Systems ........................................................................................................................8 Coal Bed Geology...........................................................................................................................................8 Upper Healy Coal Bed ..........................................................................................................................8 Healy Coal Bed ......................................................................................................................................8 Ucross Coal Bed....................................................................................................................................8 Felix Coal Bed ........................................................................................................................................8 Lower Felix Coal Bed ..........................................................................................................................12 Roland (Upper Rider) Coal Bed .........................................................................................................12 Roland of Baker Coal Bed .................................................................................................................12 Roland of Taff Coal Bed......................................................................................................................12 Smith Coal Bed ....................................................................................................................................12 Anderson Coal Bed .............................................................................................................................13 Lower Anderson Coal Bed ................................................................................................................13 Dietz 1 Coal Bed ..................................................................................................................................13 Dietz 2 Coal Bed ..................................................................................................................................13 Dietz 3 Coal Bed ..................................................................................................................................13 Dietz 4 Coal Bed ..................................................................................................................................14 Canyon Coal Bed .................................................................................................................................14 Lower Canyon Coal Bed ....................................................................................................................14 Ferry Coal Bed .....................................................................................................................................14 Werner Coal Bed.................................................................................................................................14 Otter Coal Bed .....................................................................................................................................14 Gates Coal Bed ....................................................................................................................................14 Pawnee Coal Bed................................................................................................................................15 Odell Coal Bed .....................................................................................................................................15 Roberts Coal Bed ................................................................................................................................15 Resource Allocation Planning ...................................................................................................................15 Factors Affecting Extraction of Coal Resources ....................................................................................16 Federal Land Systems ........................................................................................................................17 Railroads...............................................................................................................................................17

iv

Roads ....................................................................................................................................................17 Dwellings and Buildings ....................................................................................................................17 Alluvial Valley Floors ..........................................................................................................................17 Airports .................................................................................................................................................17 Archaeological Areas ........................................................................................................................17 Coalbed Methane................................................................................................................................17 Oil and Gas Wells ................................................................................................................................18 Pipelines ...............................................................................................................................................18 Power Lines .........................................................................................................................................18 Rivers, Lakes, and Streams ...............................................................................................................18 Towns ....................................................................................................................................................18 State Lands ..........................................................................................................................................18 Coal Reserve Evaluation Methodology ....................................................................................................18 Geologic Aspects of Mine Model Development ............................................................................19 Coal Quality ..........................................................................................................................................19 In-Place Coal Quality ..........................................................................................................................19 Mine Model Design ............................................................................................................................20 Surface Mine Model Assumptions ..................................................................................................20 Capital Cost .................................................................................................................................21 Operating Cost ............................................................................................................................21 Cash Flow ....................................................................................................................................21 Required Income ........................................................................................................................21 Underground Mine Model Assumptions .........................................................................................22 Resources Assessment Results ................................................................................................................23 Resources Evaluation.........................................................................................................................23 Reserves Evaluation ...........................................................................................................................23 Surface Coal Economic Analyses Results ......................................................................................24 Underground Coal Economic Analyses Results ............................................................................24 Conclusions...................................................................................................................................................32 Acknowledgments .......................................................................................................................................33 References Cited..........................................................................................................................................33 Glossary .........................................................................................................................................................35

Figures
1–6. Maps of the following: 1. Northern Wyoming Powder River Basin assessment area and Gillette coal field, Powder River Basin, Wyoming and Montana .......................................................37 2. Coal fields in the Northern Wyoming Powder River Basin assessment area...........38 3. Geology of Sheridan coal field showing abandoned mines and faults ......................39 4. Proposed PSO lease area showing approximate location of faults ...........................40 5. Coal bed and coal zone names used in various publications about the Powder River Basin .............................................................................................................41 6. Drill holes in the Northern Wyoming Powder River Basin assessment area, Wyoming ...............................................................................................................................42

v

7. 8. 9. 10. 11. 12–18.

Diagram of generalized methodology used for coal resource and reserve evaluation.....................................................................................................................................43 Map of generalized geology of the Powder River Basin, Wyoming and Montana..........44 Generalized stratigraphy of Powder River Basin, Wyoming and Montana ......................45 Stratigraphy of coal beds in the Northern Powder River Basin assessment area .........46 Map showing lines of cross section A-A’, B-B’, C-C’ (see figures 12–14).........................47 Cross sections of the following: 12. 13.

A-A’, faults and coal beds in Sheridan coal field .........................................................48 B-B’, a major fault with 430 feet of displacement and splitting of Dietz 3 coal bed in Sheridan coal field .......................................................................................49 14. C-C’, faults and coal beds in Sheridan coal field .........................................................50 15. D-D’, subsurface distribution of coal beds in the Northern Wyoming Powder River Basin assessment area...........................................................................51 16. E-E’, subsurface distribution of coal beds in the Northern Wyoming Powder River Basin assessment area...........................................................................52 17. F-F’, subsurface distribution of coal beds in the Northern Wyoming Powder River Basin assessment area...........................................................................53 18. G-G’, subsurface distribution of coal beds in the Northern Wyoming Powder River Basin assessment area...........................................................................54 19. Map showing stripping ratio of Roland of Baker (1929), Smith, Anderson, Dietz 3, Canyon, Lower Canyon, and Werner coal beds ......................................................55 20. Map showing elevation at top of Canyon coal bed and fault along southwestern edge of the Northern Wyoming Powder River Basin assessment area............................56 21–26. Upper Healy or Healy coal beds—Maps of the following: 21. 22. 23. 24. 25. 26. 27–29. 27. Isopachs showing extent of resources at least 2.5 feet thick in Upper Healy coal bed ..............................................................................................................................57 Depth to top of coal in Upper Healy coal bed...............................................................58 Coal resource reliability categories of Upper Healy coal bed...................................59 Isopach map showing extent of resources at least 2.5 feet thick in Healy coal bed ..............................................................................................................................60 Depth to top of coal in Healy coal bed...........................................................................61 Coal resource reliability categories of Healy coal bed...............................................62

Ucross coal bed—Maps of the following: Isopachs showing extent of resources at least 2.5 feet thick in Ucross coal bed ..............................................................................................................................63 28. Depth to top of coal in Ucross coal bed ........................................................................64 29. Coal resource reliability categories of Ucross coal bed ............................................65

30–35.

Felix and Lower Felix coal beds—Maps of the following: 30. 31. 32. 33. 34. 35. Isopachs showing extent of resources at least 2.5 feet thick in Felix coal bed ....66 Depth to top of coal in Felix coal bed.............................................................................67 Coal resource reliability categories of Felix coal bed.................................................68 Isopach map showing extent of resources at least 2.5 ft thick in Lower Felix coal bed ........................................................................................................69 Depth to top of coal in Lower Felix coal bed ................................................................70 Coal resource reliability categories of Lower Felix coal bed ....................................71

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36–44.

Roland coal beds—Maps of the following: 36. 37. 38. 39. 40. 41. 42. 43. 44. Isopachs showing extent of resources at least 2.5 feet thick in Roland (Upper Rider) coal bed .....................................................................................................72 Depth to top of coal in Roland (Upper Rider) coal bed ...............................................73 Coal resource reliability categories of Roland (Upper Rider) coal bed ...................74 Isopachs showing extent of resources at least 2.5 feet thick in Roland of Baker (1929) coal bed .......................................................................................................75 Depth to top of coal in Roland of Baker (1929) coal bed.............................................76 Coal resource reliability categories of Roland of Baker (1929) coal bed.................77 Isopachs showing extent of resources at least 2.5 feet thick in Roland of Taff (1909) coal bed ...........................................................................................................78 Depth to top of coal in Roland of Taff (1909) coal bed .................................................79 Coal resource reliability categories of Roland of Taff (1909) coal bed.....................80

45–47.

Smith coal bed—Maps of the following: 45. Isopachs showing extent of resources at least 2.5 feet thick in Smith coal bed ..............................................................................................................................81 46. Depth to top of coal in Smith coal bed...........................................................................82 47. Coal resource reliability categories of Smith coal bed...............................................83 Anderson and Lower Anderson coal beds—Maps of the following: 48. Isopachs showing extent of resources at least 2.5 feet thick and channel area in Anderson coal bed .......................................................................................................84 49. Overburden thickness above Anderson coal bed .......................................................85 50. Coal resource reliability categories of Anderson coal bed .......................................86 51. Isopachs showing extent of resources at least 2.5 ft thick and channel area in Lower Anderson coal bed ...........................................................................................87 52. Depth to top of coal in Lower Anderson coal bed .......................................................88 53. Coal resource reliability categories of Lower Anderson coal bed ...........................89 Dietz 1, 2, 3, 4 coal beds—Maps of the following: 54. Isopachs showing extent of resources at least 2.5 feet thick in Dietz 1 coal bed ..............................................................................................................................90 55. Depth to top of coal in Dietz 1 coal bed .........................................................................91 56. Coal resource reliability categories of Dietz 1 coal bed .............................................92 57. Isopachs showing extent of resources at least 2.5 feet thick in Dietz 2 coal bed ..............................................................................................................................93 58. Depth to top of coal in Dietz 2 coal bed .........................................................................94 59. Coal resource reliability categories of Dietz 2 coal bed .............................................95 60. Isopachs showing extent of resources at least 2.5 ft thick and west and east channels in Dietz 3 coal bed ...........................................................................................96 61. Depth to top of coal in Dietz 3 coal bed .........................................................................97 62. Coal resource reliability categories of Dietz 3 coal bed .............................................98 63. Isopachs showing extent of resources at least 2.5 feet thick in Dietz 4 coal bed ..............................................................................................................................99 64. Depth to top of coal in Dietz 4 coal bed .......................................................................100 65. Coal resource reliability categories of Dietz 4 coal bed ...........................................101

48–53.

54–65.

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66–71.

Canyon and Lower Canyon coal beds—Maps of the following: 66. Isopachs showing extent of resources at least 2.5 feet thick and channel area in Canyon coal bed ................................................................................................102 67. Depth to top of coal in Canyon coal bed .....................................................................103 68. Coal resource reliability categories of Canyon coal bed .........................................104 69. Isopachs showing extent of resources at least 2.5 feet thick and channel area in Lower Canyon coal bed ....................................................................................105 70. Depth to top of coal in Lower Canyon coal bed .........................................................106 71. Coal resource reliability categories of Lower Canyon coal bed .............................107 Ferry coal bed—Maps of the following: 72. 73. 74. Isopachs showing extent of resources at least 2.5 feet thick in Ferry coal bed ............................................................................................................................108 Depth to top of coal for Ferry coal bed ........................................................................109 Coal resource reliability categories of Ferry coal bed..............................................110 Isopachs showing extent of resources at least 2.5 feet thick and channel area in Werner coal bed ................................................................................................111 Depth to top of coal in Werner coal bed .....................................................................112 Coal resource reliability categories of Werner coal bed .........................................113

72–74.

75–77.

Werner coal bed—Maps of the following: 75. 76. 77.

78–80.

Otter coal bed—Maps of the following: 78. Isopachs showing extent of resources at least 2.5 feet thick map in Otter coal bed ............................................................................................................................114 79. Depth to top of coal in Otter coal bed ..........................................................................115 80. Coal resource reliability categories of Otter coal bed ..............................................116

81–83.

Gates coal bed—Maps of the following: 81. 82. 83. Isopachs showing extent of resources at least 2.5 feet thick in Gates coal bed ............................................................................................................................117 Depth to top of coal in Gates coal bed ........................................................................118 Coal resource reliability categories of Gates coal bed ............................................119 Isopachs showing extent of resources at least 2.5 feet thick in Pawnee coal bed ............................................................................................................................120 Depth to top of coal in Pawnee coal bed ....................................................................121 Coal resource reliability categories of Pawnee coal bed ........................................122 Isopachs showing extent of resources at least 2.5 feet thick in Odell coal bed ..................................................................................................................123 Depth to top of coal in Odell coal bed..........................................................................124 Coal resource reliability categories of Odell coal bed..............................................125 Isopachs showing extent of resources at least 2.5 feet thick in Roberts coal bed ............................................................................................................................126 Depth to top of coal in Roberts coal bed .....................................................................127 Coal resource reliability categories of Roberts coal bed .........................................128

84–86.

Pawnee coal bed—Maps of the following: 84. 85. 86.

87–89.

Odell coal bed—Maps of the following: 87. 88. 89.

90–92.

Roberts coal bed—Maps of the following: 90. 91. 92.

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93.

Diagram showing the effect of coal bed depth upon restricted resource owing to mine pit highwall setback requirements ..............................................................129 94. Map of land use restrictions in the Northern Wyoming Powder River Basin assessment area.......................................................................................................................130 95. Map of coal ownership in the Northern Wyoming Powder River Basin assessment area.......................................................................................................................131 96. Cross section H-H’ in Gillette coal field ................................................................................132 97–99. Diagrams of the following: 97. Reserve estimate for Northern Wyoming Powder River Basin assessment area ...................................................................................................................................133 98. Resources in five categories for the seven coal beds in reserve evaluation .......134 99. Results of Northern Wyoming Powder River Basin assessment area coal resource analysis for the seven coal beds in reserve evaluation ..........................135 100. Mining costs for Northern Wyoming Powder River Basin assessment area and Gillette coal field compared ............................................................................................136

Tables
1. 2. 3. 4. 5. 6. 7. Original coal resources in beds at least 2.5 feet thick in the Northern Wyoming Powder River Basin assessment area ......................................................................................9 Regional mining model stratigraphic sequence in the economic evaluation of the Northern Wyoming Powder River Basin assessment area .................................................20 Underground resources in beds at least 10 feet thick in the Northern Wyoming Powder River Basin assessment area ....................................................................................23 Original coal resources in beds at least 2.5 feet thick, by subsurface coal ownership categories in the Northern Wyoming Powder River Basin assessment area..................25 Original coal resources in beds at least 2.5 feet thick, by overburden depth in the Northern Wyoming Powder River Basin assessment area .................................................27 Original resources in beds at least 5.0 feet thick and at least a 10:1 strip ratio by stripping ratio in the Northern Wyoming Powder River Basin assessment area ............31 Resources in beds at least 2.5 thick, reported by bed for restrictions, recovery rates, mining losses, and recoverable resources for the Northern Wyoming Powder River Basin assessment area ....................................................................................31 Life-of-mine costs by mining strip ratio in the Northern Wyoming Powder River Basin assessment area .............................................................................................................32 Break-even cost and resource volumes by stripping ratio in the Northern Wyoming Powder River Basin assessment area ....................................................................................32

8. 9.

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Abbreviations Used in This Report
Btu/lb mi mi2 yr API BST GIS LLC MST MST/yr NWPRB PRB PSO	 	 ST USGS UTM British thermal unit per pound mile square mile year American Petroleum Institute billion short tons geographic information system limited liability company million short tons million short tons per year Northern Wyoming Powder River Basin (assessment area) Powder River Basin lease area in Sheridan County; part of a land-exchange proposal short ton U.S. Geological Survey Universal Transverse Mercator

Conversion Factors
Multiply By Length foot	(ft) mile	(mi) square	mile	(mi ) square	feet	(ft2) pounds	(lbs) short	tons	(2,000	lbs) million	short	tons	(MST) billion	short	tons	(BST) trillion	short	tons	(TST)
2

To obtain

0.3048 1.609 2.590 0.929 Density 0.4536 0.90718474 1,000,000 1,000,000,000 1,000,000,000,000 Area

meter	(m) kilometer	(km) square	kilometer	(km2) square	meter	(m2) kilograms	(kg) metric	tons	(2,204.6	lb) short	tons short	tons 	short	tons

acre-ft

1,770

short	tons,	subbituminous	coal

Assessment of Coal Geology, Resources, and Reserves in the Northern Wyoming Powder River Basin
By David C. Scott1, Jon E. Haacke1, Lee M. Osmonson1, James A. Luppens2, Paul E. Pierce2, and Timothy J. Rohrbacher3

Abstract
The abundance of new borehole data from recent coal bed natural gas development in the Powder River Basin was utilized by the U.S. Geological Survey for the most comprehensive evaluation to date of coal resources and reserves in the Northern Wyoming Powder River Basin assessment area. It is the second area within the Powder River Basin to be assessed as part of a regional coal assessment program; the first was an evaluation of coal resources and reserves in the Gillette coal field, adjacent to and south of the Northern Wyoming Powder River Basin assessment area. There are no active coal mines in the Northern Wyoming Powder River Basin assessment area at present. However, more than 100 million short tons of coal were produced from the Sheridan coal field between the years 1887 and 2000, which represents most of the coal production within the northwestern part of the Northern Wyoming Powder River Basin assessment area. A total of 33 coal beds were identified during the present study, 24 of which were modeled and evaluated to determine in-place coal resources. Given current technology, economic factors, and restrictions to mining, seven of the beds were evaluated for potential reserves. The restrictions included railroads, a Federal interstate highway, urban areas, and alluvial valley floors. Other restrictions, such as depth, thickness of coal beds, mined-out areas, and areas of burned coal, were also considered. The total original coal resource in the Northern Wyoming Powder River Basin assessment area for all 24 coal beds assessed, with no restrictions applied, was calculated to be 285 billion short tons. Available coal resources, which are part of the original coal resource that is accessible for potential mine development after subtracting all restrictions, are about 263 billion short tons (92.3 percent of the original coal resource). Recoverable coal, which is that portion of available coal remaining after subtracting mining and processing losses, was determined for seven coal beds with a stripping ratio of 10:1 or less. After mining and processing losses were subtracted, a total of 50 billion short tons of recoverable coal was calculated.
1 2 3

Coal reserves are the portion of the recoverable coal that can be mined, processed, and marketed at a profit at the time of the economic evaluation. With a discounted cash flow at 8 percent rate of return, the coal reserves estimate for the Northern Wyoming Powder River Basin assessment area is 1.5 billion short tons of coal (1 percent of the original resource total) for the seven coal beds evaluated.

Introduction and Objectives
Technical terms used in this report requiring additional explanation are italicized when used for the first time and their definitions are given in the Glossary section at the end of the report. The United States Geological Survey (USGS) National Coal Resource Assessment represented the first national digital coal assessment of in-place coal resources (Pierce and Dennen, 2009). However, in-place estimates do not, by themselves, provide all the information needed for resource planning; estimates of that portion of the in-place coal resources that are economically recoverable (reserves) are equally important. Since the National Coal Resource Assessment study, the methodology used by the USGS for determining coal resources and reserves has been refined, taking advantage of improvements in geologic and mining model computer software (Luppens and others, 2008). Confusion concerning the use of the terms resources and reserves is common but, although they are frequently used interchangeably, there are significant differences. Coal resources include those in-place tonnage estimates determined by summing the volumes for identified and hypothetical coal resources and coal zones of a minimum thickness and within certain depth limits (commonly 0-2,000 feet (ft) deep). Coal reserves, a subset of the coal resources, are considered economically producible at the time of classification (Pierce and Dennen, 2009). Luppens and others (2009) discuss the terms “resources” and “reserves” and summarize how coal availability and resource studies are used to determine estimates of economically recoverable coal resources. Previous estimates (see references in “Previous Coal Resource Estimate” section) of coal reserves have typically used average mining percentages to obtain volume estimates

U.S. Geological Survey, Denver, Colorado 80225 U.S. Geological Survey, Reston, Virginia 20192 Scientist Emeritus, U.S. Geological Survey

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Northern Wyoming Powder River Basin Coal

of recoverable coal. Those estimates are general and do not take into consideration the amount of coal that cannot be mined because of environmental concerns, geological constraints, coal loss owing to mining and preparation technology, or economic constraints. More recently, published studies by the USGS have indicated that application of site-specific restrictions to estimates of available coal resources markedly reduces the amount of coal that is considered recoverable (for example, Ellis and others, 2002). The first United States coal basin to be evaluated in the current USGS assessment is the Powder River Basin (PRB) in northeastern Wyoming and southeastern Montana (fig. 1). The Powder River Basin was subdivided into four assessment areas to keep the databases and modeled areas at a manageable size and permit a more timely publication of assessment results. The first such assessment area was the Gillette coal field (fig. 1), for which coal resource and reserve estimates were made by Luppens and others (2008). This report summarizes the assessment of the second assessment area, an area of approximately 3,000 square miles (mi2) in the central part of the PRB in Sheridan, Campbell, and Johnson Counties, Wyoming. The area extends from the northern boundary of the Gillette coal field north to the Montana border and east-west across the basin (fig. 1). This part of the PRB is referred to in this report as the Northern Wyoming Powder River Basin (NWPRB) assessment area. Reliable coal resource and reserve estimates are essential for use in making local, State, and Federal energy and land-use policy decisions for the foreseeable future. Additionally, this information can aid planners in determining possible socioeconomic effects on the region as coal resources are developed and eventually approach depletion. Previous coal availability and recoverability studies in the United States have relied extensively on reinterpretation of existing data. With the recent development of coalbed methane in Wyoming and Montana, substantial of new data from drill holes are now available. The interpretation of these new data provides much more detailed information that can be used to more accurately calculate coal resources and reserves in the PRB. The primary objectives of this assessment were as follows: 1. 2. Complete the coal resource and reserve assessment for the second assessment area in the PRB. Improve geological assurance by updating the current stratigraphic database with information obtained from recently completed coalbed methane well and oil and gas well data. Develop a more comprehensive in-place coal resource computer model with the geological assurance to support regional reserve estimates. Complete an economic mining evaluation that was customized to the environmental and technological restrictions in the NWPRB and derive the estimate of coal resources and reserves for the assessment area.

Previous Coal Resource Estimates
A number of previous studies contain estimates of coal resources and reserves in the NWPRB assessment area, as well as for all of the PRB. These studies, some of which are listed below, have included different coal beds, coal zones, and boundaries. There have also been different purposes for which resources and reserves have been calculated, as well as differences in criteria, such as variations in coal thickness and overburden categories, used for those calculations (Luppens and others, 2008). Therefore, the results are difficult to compare with one another. 1. Berryhill and others (1950) published a report estimating coal reserves in the Sheridan coal field in the NWPRB assessment area at 16.3 billion short tons (BST). The Sheridan coal field covers about 1,000 mi2, or about one-third of the NWPRB assessment area (figs. 2, 3). The resource estimates included reliability categories of measured, indicated, and inferred based on distance from a drill hole. Olive (1957) estimated that the Spotted Horse coal field contained a total of 12 BST of coal reserves (fig. 2). The estimate was based on measured, indicated, and inferred reliability categories and included all coal beds at least 2.5 ft thick. Coal reserves in Campbell County (fig. 1) totaled about 8 BST, with 4 BST in Sheridan County. Glass (1978) estimated more than 26 BST of coal in Sheridan County at depths up to 3,000 ft (fig. 2). An estimated 7.1 BST of that coal occurs under less than 1,000 ft of overburden, with 5.2 BST estimated to be minable by underground methods. An additional 1.9 BST of coal is potentially recoverable by surface mining at depths less than 200 ft. Ellis and others (1999) estimated 11 BST of coal for the Wyodak-Anderson coal zone in the Sheridan coal field (fig. 2). This estimate was reported on reliability categories of measured, indicated, inferred, and hypothetical to a depth of 1,500 ft. Pittsburg and Midway Coal Mining Company estimated an area of about 2,500 acres in the northern part of the Sheridan coal field to contain 112.5 million short tons (MST) of mineable Federal coal, of which, 107 MST was classified as recoverable (fig. 4; U.S. Bureau of Land Management, 2003a).

2.

3.

4.

5.

3.

Previous and Proposed Coal Mining
Coal mining in the PRB began in 1883 near the towns of Glenrock and Douglas, Wyoming (fig. 1); development of railroad lines in 1886 and 1887 facilitated the growth of mining activity. The Sheridan, Spotted Horse, and Little Powder River

4.

Other Energy Commodities coal fields are all within the boundary of the NWPRB assessment area (fig. 2), as are portions of the Buffalo and Powder River coal fields (fig. 2) (Glass, 1976). The first documented coal mining in the NWPRB assessment area began in the Sheridan coal field in Sheridan County about 1887, and substantial production was attained in the early 1900s (figs. 2, 3). Records from Sheridan County show that underground coal mine production totaled about 1.9 MST in 1918 (Glass, 1978). Subsequent production declined but continued above 400,000 short tons (ST) per year until a steep decline began in the late 1950s. Yearly production declined to about 217,790 ST of coal in 1968 (Glass, 1978). Until 1978, most of the coal production in the Sheridan coal field was from underground mines. Of the Sheridan County cumulative coal tonnage of 61.5 MST through 1978, underground mining accounted for about 47.8 MST, or 78 percent. This production came from some 70 underground mines, most of which are located in the Acme area, about 10 miles (mi) north of Sheridan, Wyoming (fig. 3). Surface subsidence pits and troughs mark locations of many of the abandoned underground mine workings (Glass, 1978). The Dietz (Dietz 3 of this report) and Monarch (Canyon of this report) coal beds in the Sheridan coal field were surface mined at the Big Horn mine (fig. 3) from the years 1962 to 2000 (Ellis and others, 1999). From 1944 until 2000, more than 47 MST of coal was produced from the Big Horn mine. Total recorded production from the entire NWPRB assessment area is estimated at greater than 100 MST of coal (Nick Jones, Wyoming State Geological Survey, written commun., 2009). Presently (2009), there are no active surface or underground coal mines in the NWPRB assessment area. In 2003, Pittsburg and Midway Coal Mining Company proposed a land exchange with the Federal government for lands within the Sheridan coal field. This land, which encompasses about 2,500 acres in T. 58 N., R. 84 W., secs. 20, 21, 22, 23, 27, 28, 29, 33, and 34, is referred to as the PSO lease area in the remainder of this report (fig. 4). The PSO lease area is adjacent to the reclaimed Ash Creek mine in T. 58 N., R. 84 W., NE ¼ sec. 22 (U.S. Bureau of Land Management, 2003a). Pittsburg and Midway Coal Mining Company estimated that the PSO lease area contains 112.5 MST of mineable Federal coal, of which 107 MST was classified as recoverable. The projected mining rate was 1 MST for the first year; subsequent production increased to 10 MST per year by the fifth year of mining. Within the PSO proposed lease, the Dietz 1 and Dietz 3 coal beds would be surface mined using a strip mining ratio of about 2.5 to 1 (fig. 5). The Dietz 1 coal bed is present in the northern half of the lease area and ranges from 5 to 20 ft thick. The Dietz 3 coal bed is present throughout the lease area and averages 41 ft thick. Overburden above the Dietz 1 seam is as much as 275 ft thick. The overburden above the Dietz 3 where Dietz 1 is not present is from 20 to 120 ft thick. The interburden thickness between the Dietz 1 and Dietz 3 seams ranges from 20 to 140 ft, with a thickening trend from east to west. Two northeast-trending faults approximate the northwest and southeast boundaries of the lease area

3

(fig. 4).These faults are known to be present, although their exact locations and displacements have not been accurately defined by drilling. The displacements across each of these two major faults are estimated to be 60 to 180 ft. Generally, the stratigraphic dip is to the northeast at approximately 4 degrees between the faults. There are local areas where the shallow strata dip at higher angles, generally owing to local folding or faulting (U.S. Bureau of Land Management, 2003a). Pittsburg and Midway Coal Mining Company entered into a joint venture agreement with CONSOL Energy Inc. to develop the PSO lease area (Lynn Manning, CONSOL Energy, oral commun., 2009). CONSOL of Wyoming LLC, and Chevron NPRB, LLC, formed a new company, Youngs Creek Mining Company, LLC, to develop and operate the proposed mine (Lynn Manning, CONSOL Energy, oral commun., 2009). The PSO lease area contains coal reserves totaling approximately 315 MST with an estimated heat content of 9,350 British thermal units per pound (Btu/lb) and an average sulfur content of 0.47 percent. As of early 2009, there were no immediate plans to develop the PSO lease area. A spokesperson for CONSOL indicated that coal prices would dictate the development of the property (Lynn Manning, CONSOL Energy, oral commun., 2009).

Other Energy Commodities
Other energy commodities currently being developed in the NWPRB assessment area include conventional oil and gas and coalbed methane. Although methane is a gas, it is discussed separately because there are potential conflicts and concerns specific to the development of that resource that do not apply to conventional oil and gas development. Powder River Basin oil and gas development began in 1887 with the discovery of an oil and gas field near Moorcroft, Wyoming (Ellis and others, 2002; fig. 1). According to the Wyoming Oil and Gas Conservation Commission, 3,235 oil and gas wells were reported within the NWPRB assessment area as of September, 2009 (Wyoming Oil and Gas Conservation Commission, 2009) (fig. 6). Current infrastructure for production and transport of oil and gas in the area includes roads, pipelines, pump houses, and separators. Generally, there is little conflict between coal development and conventional oil and gas development in the NWPRB assessment area, as oil and gas reservoirs are primarily in stratigraphic units below the minable coal seams. Where there are oil and gas development and coal mining in the same geographic areas, mining is confined to areas outside a specific buffer distance from wells, pipelines, and other oil- and gas-related facilities. Development of coalbed methane in the PRB began in the early 1980s. As of September 2009, more than 9,491 wells were producing this gas in the NWPRB assessment area (fig. 6) (Wyoming Oil and Gas Conservation Commission, 2009). In 2003, an Environmental Impact Statement document contained an analysis of potential effects based on the assumption that by the year 2012, there will be about 51,000 producing private,

4

Northern Wyoming Powder River Basin Coal

State, and Federal coalbed methane wells and associated ancillary facilities in about an 8-million-acre area, covering all or parts of Campbell, Converse, Johnson, and Sheridan Counties, Wyoming (U.S. Bureau of Land Management, 2003b). The production life of such a well is estimated to be about 10 to 12 years (yr), although production from multiple seams can extend the life of the well by an additional 10 to 30 yr (De Bruin and others, 2004). Approved spacing for coalbed methane wells in the Wyoming PRB is one well per coal bed per 80 acres, or eight well-cluster locations per section. Because there are three potential productive coal beds in the PSO lease area, a total of 78 methane-producing wells could be drilled within the boundary of that area. As of March 2003, five such wells had been completed or spudded within the PSO lease area (U.S. Bureau of Land Management, 2003a). There are three coal beds within the PSO lease area that are expected to produce coalbed methane: the Dietz 3, Canyon, and the Werner (figs. 4, 5). Methane resources associated with the Dietz 3 coal bed that are not recovered prior to mining would be vented to the atmosphere and irretrievably lost when the coal is removed. Because the Canyon and Werner coal beds are stratigraphically below the Dietz coal bed, methane that is not recovered prior to mining of the Dietz 3 coal bed would not be lost as a direct result of mining activities, but it could be recovered by methane wells located on lands adjacent to the proposed mining area (U.S. Bureau of Land Management, 2003a). To produce coalbed methane, a large volume of groundwater is pumped from the coal bed. The groundwater can be discharged to holding ponds for consumption by livestock, discharged to existing drainage systems, released into the atmosphere through the use of misting towers, or reinjected into another stratigraphic unit. Concerns regarding possible contamination of existing surface water, the quality of water in holding ponds, the production of saline crust on the ground surface, the lowering of the water table, and possible contamination or depletion of groundwater in existing aquifers have all been examined in the PRB by Rice and others (2000). Conflicts have arisen between coal mining and coalbed methane development. One conflict involves the ownership of the methane—whether it belonged to the owner of the oil and gas estate or the owner of the coal estate. The U.S. Supreme Court resolved this issue in 1999, when it ruled that coalbed methane in Wyoming is part of the oil and gas estate. In addition, the court specified that the owner of the methane leases has the right to gain access and to develop its estate, and owners of the land surface should be adequately compensated for damage to their property resulting from methane extraction. The Bureau of Land Management established Conflict Administration Zones to guide development of coalbed methane leases in the path of near-term coal mining. In these zones, standard guidelines offer a process for settling conflicts and scheduling development of each resource under a Federal mineral estate.

Study Methodology
The methodology for calculating coal resources and reserves in the NWPRB assessment area is described by the three phases shown on the flow chart in figure 7. The first phase began with data collection and editing as a result of the acquisition of recently generated geologic information. The second phase involved correlating individual coal beds, subsequent geologic modeling of those beds, and resource allocation to determine land use, and technologic restrictions within the NWPRB assessment area. The third phase involved completing a mining economics evaluation to determine economically recoverable coal resources (reserves).

Data Collection
The first phase of coal resource and reserve evaluation involved data collection and editing of those data (fig. 7). The database of Luppens and others (2008) was used as a basis for coal bed correlations along the southeastern edge of the NWPRB assessment area. Data from Molnia and Pierce (1992) were used as a basis for coal bed correlations in the Sheridan coal field. Data points (geophysical well logs) were added between these two areas to complete coal bed correlations. A total of 4,003 drill holes were used to construct the database in the assessment area (fig. 6). As of September 2009, approximately 3,235 oil and gas wells and 9,772 coalbed methane wells had been drilled in the NWPRB assessment area. Data within a 3-mile-wide buffer zone were added around the assessment area’s boundary to extend stratigraphic correlations and to minimize the edge effect when the coal beds were modeled. The drill hole geophysical logs selected for data entry were downloaded as TIFF images from the Wyoming Oil and Gas Conservation Commission web site (Wyoming Oil and Gas Conservation Commission, 2009). USGS personnel completed data entry for a total of 2,496 new geophysical well logs. In addition, the Wyoming State Geological Survey contributed 291 data points, and the USGS National Coal Resources Data System, contributed 1,216 data points. The entire 4,003 data points were then entered into the StratiFact database program (GRG Corporation, 1998). These new data consisted of both oil and gas logs and coalbed methane geophysical well logs. Because geophysical logs differ widely in quality and resolution, interpretation of coal thickness is commonly difficult. Gamma-ray logs were available for most of the wells and constituted the basis for most of the lithologic interpretations. Traditionally, oil and gas wells are logged primarily for detail in deep formations, and the upper (coal-bearing) intervals were either not logged or only minimally logged with the gamma ray tool through the surface casing. Log data in older wells generally consisted only of spontaneous potential, resistivity, and conductivity logs, making the identification of coal beds more difficult.

Data Collection The most reliable log suite consisted of natural gamma ray, gamma-gamma density, and resistivity traces. However, many coalbed methane wells were logged with gamma ray only, either in open hole or through steel drill pipe or casing. Additionally, many of those methane wells were logged with gamma ray only to the top of the target coal. Because the primary focus of this report was to determine coal resources and reserves rather than conducting a comprehensive geological study, detailed noncoal lithology types were not critical to the results of the evaluation. Therefore, all lithology was coded as either coal or rock. Parting intercepts within coal beds and interburden between coal beds were also coded as rock. Intervals with no geophysical log, such as the shallower part of an oil well or coalbed methane well that was not logged to the bottom, were entered as “No Log.” However, if the methane-producing interval was available from production records for those wells not completely logged, that interval was entered as coal.

5

lease area. The Anderson coal bed in the PSO lease area is correlated with and also known as the Dietz 1 coal bed in this report. The Dietz 1 coal bed in the PSO lease area is correlated with and also known as the Dietz 2 coal bed in this report. The Dietz 2 coal bed in the PSO lease area is correlated with and known as the Dietz 3 coal bed in this report. The two mineable coal beds within the PSO lease area were referred to as the Dietz 1 and Dietz 3 (U.S. Bureau of Land Management, 2003a). The stratigraphic framework for coal bed correlations in this report (fig. 5) is based primarily on Molnia and Pierce (1992) and Luppens and others (2008). Within their original framework, hundreds of new coalbed methane wells have been used to extend their correlations from the Sheridan coal field across the entire NWPRB assessment area.

Coal Bed Correlations
When the drill hole data entry was completed, the graphical interface of the StratiFact (GRG Corporation, 1998) database was a critical tool for interpretation and management of the large volume of accumulated information. With the graphics program, on-screen cross sections were selected, edited, and correlated, and the real-time database was edited. Both linear and circular cross sections were constructed to correlate coal beds across the NWPRB assessment area. Circular cross sections that verify closure were especially valuable when coal beds either split or thinned adjacent to sand channels. In this process, the beginning and ending drill holes of the cross section are the same, assuring the integrity of the correlations. The coal bed nomenclature used by Molnia and Pierce (1992) in the Sheridan and Gillette coal fields was used as a basis for correlating and naming coal beds between those two coal fields. Guidelines were established regarding which nomenclature would be used when two named beds merge into a single bed. The general correlation guidelines used for this assessment are as follows: 1. Two named beds are considered to have merged into a single named bed when the intervening parting is less than 2.0 ft thick. The following exceptions were made for modeling purposes: • In individual holes, coal beds split by partings as much as 5 ft thick are considered to be merged if nearby surrounding holes indicate the beds have merged into a single bed. • In individual holes, coal beds with no partings or partings less than 2.0 ft thick are considered to be split into two beds if surrounding holes show the coal has split into two beds. 2. The upper bed’s name will be used for the mergedbed name with two exceptions:

Coal Bed Nomenclature
Prior to the recent development of coalbed methane, correlation of individually named coal beds across the entire PRB was difficult, because the coal beds commonly split, merge, and pinch out (Flores and others, 1999). In addition, distances between drill holes used for the correlation process were generally large, increasing the uncertainty in correlating individual coal beds from one drill hole to the next. Previous reports relied on drill-hole data that were 10 mi. or more apart. However, with the recent drilling and development of methane wells in the PRB, data from thousands of new drill holes are now available, and the distance between drill holes is thus reduced (fig. 6). Many different names for individual coal beds have been used during the past 29 yr (fig. 5). A report by Kent and others (1980), who described the northern part of the Gillette coal field that falls within the Spotted Horse coal field of Olive (1957), established a coal bed nomenclature system that has become the standard for much of the PRB in Wyoming. Kent and others (1980) retained certain existing coal bed nomenclature and revised other nomenclature by introducing new coal bed names. Molnia and Pierce (1992) also described coal bed stratigraphy in the central PRB in Wyoming and Montana; their nomenclature follows the usage of Culbertson and others (1979), Law and others (1979), Kent and others (1980), and Culbertson (1987). Flores and others (1999) defined a coal zone in the PRB known as the Wyodak-Anderson, which includes many named coal beds in the upper part of the Tongue River Member of the Fort Union Formation. For assessment purposes, the individual correlated coal beds composing the Wyodak-Anderson zone include the Smith, Anderson, Lower Anderson, Dietz 1, Dietz 2, Dietz 3, Dietz 4, Canyon, Lower Canyon, Ferry, and Werner (fig. 5). Pittsburg and Midway Coal Mining Company utilized the following nomenclature for coal beds in the PSO

6

Northern Wyoming Powder River Basin Coal • A rider name becomes the main bed name; for example, Roland (Baker, 1929) bed merged with Roland (Upper Rider) bed becomes Roland (Baker, 1929) bed. • In the west-central part of the NWPRB assessment area, the thick Canyon (lower) bed merges with the thin Anderson bed and retains the Canyon bed name.

Geologic Modeling
The first step of phase two of the assessment (fig. 7) was the creation of a digital coal bed model. Following coal bed correlations, preliminary coal isopach maps were created using the single bed mapping software Surfer (Golden Software, 2002) to decide which coal beds would be included in the geologic model. The basic criterion for inclusion was a minimum areal continuity of two or more townships. Twentyfour coal beds were selected and digital models for each bed were constructed. The integrated, multibed modeling program PC/Cores (Mentor Consultants, 2005) was used to produce the gridded geologic models. This modeling program was designed for coal or mineral evaluations and is more effective because of its capability to grid multiple beds at one time. The multiple gridding software allows for a considerable reduction in time when compared with other programs that grid only one parameter at a time. The time required to produce all of the required grids using a program that generates grids one parameter at a time can be large, considering that for each coal bed, grids must be made for coal thickness, parting thickness, coal height (coal plus parting), and roof and floor structures. Grids must then be calculated for the overburden and interburden for each seam, and roof grids for each coal bed must be individually subtracted from the surface grid or the floor grid for the next stratigraphically higher coal bed. In cases where the drill holes were not deep enough, or an interval was not logged, a zero coal thickness is assigned to each affected coal bed. To mitigate these false zeros, each coal bed isopach was edited manually, which was especially time consuming given the number of coal beds modeled and the prevalence of shallow drill holes in the NWPRB assessment area. Most multiple-bed modeling programs are highly automated; a subroutine uses individual coal bed structure grids to check for drill holes too shallow to penetrate a given bed. This feature produces more-accurate digital models without the need for extensive manual editing. The PC/Cores program (PC/Cores (Mentor Consultants, 2005) code allows correlations to pass through the sections of the drill holes that were not geophysically logged to reduce the generation of false zero-thickness values. The geologic models were gridded at a cell size of about 246 ft (75 meters). To verify coal bed correlations and coal bed areal distributions, preliminary roof and floor contour maps for each modeled bed were generated to check for “bull’s eye” anomalies. A routine within the PC/Cores modeling program was used to identify suspect locations by comparing collar elevations to the digital elevation model of the Earth’s surface. A number of location errors were resolved using this technique. When editing was completed, the final geologic model was created and all the grids necessary for determination of the in-place coal resource volumes were generated. A copy of the in-place coal resources model was modified to generate the grids necessary for the coal reserve evaluation. The need for a second model was dictated by the fact that only 7 of the

Geologic Setting
The PRB covers about 22,000 mi2 in northeastern Wyoming and southeastern Montana (fig. 8). Near the west edge of the basin, the axis trends northwest-southeast and is markedly asymmetrical with steep dips on the west side and gentle dips on the east (fig. 8). The Eocene Wasatch Formation covers about one-third of the PRB, mostly in Wyoming, and the underlying Paleocene Fort Union Formation is exposed along the basin margins in Wyoming and throughout most of the basin in Montana (figs. 8, 9). The Wasatch Formation conformably overlies the Fort Union Formation in the center of the basin and unconformably overlies it along the basin margins (fig. 9). The boundary between the two formations is generally placed above the Roland coal bed (fig. 10) (Ellis and others, 1999). Fort Union strata lie unconformably on the Upper Cretaceous Lance Formation (figs. 8, 9, 10). In the Wyoming part of the PRB, the Fort Union Formation comprises three members, in ascending order the Tullock, Lebo, and Tongue River Members (fig. 9) (Ellis and others, 2002). The strata incorporate some of the thickest and most extensive deposits of low-sulfur subbituminous coal in the world (Molnia and Pierce, 1992). Most of this coal is in the Wyodak-Anderson coal zone in the Tongue River Member (Ellis and others, 1999). In general, the coals range from subbituminous C to subbituminous A in apparent rank. The lower rank subbituminous C coal is located primarily in the shallower part of the basin (surface to 1,000-ft depth), the subbituminous B ranked coal is at an intermediate depth in the basin (1,000– 1,400-ft depth), and subbituminous A ranked coal is in the deepest part of the basin (greater than 1,400-ft depth) (Stricker and others, 2007). The NWPRB assessment area encompasses an area of about 3,000 mi2 in the central part of the PRB (fig. 8). The southeastern part is adjacent to the northern boundary of the Gillette coal field as defined by Luppens and others (2008). The northern boundary of this assessment area is the Montana border, and the east and west boundaries are the approximate eastern and western margins of the PRB. Along the western edge of the PRB, strata dip between 20° and 25° to the east, whereas rocks dip only about 2° to 5° to the west along the eastern edge of the basin (Flores and others, 1999). Surface coal mining has been more prevalent along the eastern edge of the basin because of the shallower dip, whereas underground mining was more prevalent along the western edge of the basin in the area of the Sheridan coal field.

Influence of Geology in Coal Bed Correlations 24 coal beds modeled were to be included in reserve analysis. The basic assumption used to qualify coal beds for potential coal reserve evaluation was to include coal beds that had 2.5 ft or greater thickness. A final set of grids from both the coal resources and reserves models (thickness, parting thickness, and roof and floor structures) for each coal bed was converted in PC/Cores to a generic ASCII grid format. These ASCII grids were then exported to the software program ArcView (Environmental Systems Research International, 2001) to begin the last step in phase two of the assessment, which was the modeling of the restrictions to mining.

7

Influence of Geology in Coal Bed Correlations
The large increase in borehole data for this assessment has resulted in a much better understanding of the coal geology in the NWPRB assessment area. Although the focus of this assessment does not include a detailed discussion of the geology of this area, it is informative to address the influence of geology as it relates to resources, reserves, and the mining of coal beds. The calculation of resources and reserves requires the identification of geological constraints that are likely to inhibit mining (Thomas, 2002). Such geologic constraints in the NWPRB area include faults offsetting the coal beds, geometry (dip) of the coal beds, and paleochannels within the coal-bearing strata.

Faults
Although faults do not markedly alter calculation of coal resources, they have a pronounced effect on the determination of coal reserves. In the northwestern part of the NWPRB assessment area, numerous northeast-trending faults are present in the Sheridan coal field (fig. 3). The faults, most of which are downthrown on the east, postdate coal formation. Faults shown in figure 3 are based on Ellis and others (1999) or they were identified during the correlation phase of this study from observations of stratigraphic offset between drill holes. Cross sections that show typical northeast-trending faults in the Sheridan coal field are shown in figures 11–18. The incidence of faults in coal beds has an important effect on the selection of mining methods and on productivity. Major faults with vertical displacements greater than 65 ft commonly are used to delineate mine plan boundaries. Numerous minor faults are generally associated, trending almost parallel to the major faults. The adverse effects of faulting are greater on underground mining operations: whereas a fault with a vertical displacement of 3–16 ft may not pose much of a problem in a surface mine, it may be a serious impediment in underground mining (Thomas, 2002).

The PSO lease area proposed by Pittsburg and Midway Coal Mining Company, which is within the area of faults in the Sheridan coal field, provides an example of how faults can relate to mining (fig. 4). The proposed 15-yr mining block for the PSO lease area is generally confined by two northeasttrending faults labeled A-A′ and B-B′ in figure 4. Surface mining by truck/shovel method would remove coal between the faults with a stripping ratio of about 2.5 to 1 (U.S. Bureau of Land Management, 2003a). Olive (1957) described concentrations of faults in two areas within the Spotted Horse coal field (fig. 2). Eleven faults were mapped in an area of shallow southwesterly plunging folds near T. 56 and 57 N., R. 76 W., and T. 56 and 57 N., R. 77 W. The second concentration contained five northeast-toeast-trending faults in T. 54 N., R. 74 and 75 W., all but one of which are normal with vertical displacements ranging from 20 to 300 ft and whose lengths range from a fraction of a mile to more than 3.5 mi. The method of underground mining will influence resource losses associated with faults. If the method used is longwall mining, a larger resource loss will occur, due to the fact that longwall operations need hazard-free runs in a designated panel of coal. Longwall panels are typically 5,000–10,000 ft long and 750–1,500 ft wide, requiring a large block of coal. All faulted areas would need to be restricted if their amounts of throw displace the coal bed to be mined out of line with the preset coal shearer. If the coal panels between faults are too small, then the whole block may be discounted (Thomas, 2002). Mine gas emissions have been attributed to sources unrelated to the mined coal bed since the first documentation of methane explosions in coal mines (Payman and Statham, 1930). Faults may pose problems with respect to gas emissions. In certain cases, for example, faults may act as barriers to gas flow, especially if they contain impermeable fault gouge, or the displacement causes impermeable rock above or below the mined coal bed to abut against it (Diamond, 1982). In these situations, large volumes of overpressured gas can be trapped behind the fault. If, on the other hand, underground mine development proceeds through the fault, there is a potential for sudden, explosive gas emissions. As shown in figure 3, there are abandoned underground workings associated with faults in the northern part of the Sheridan coal field. Another important factor in the evaluation of the resources and reserves in the NWPRB assessment area is the dip of the coal beds. As mentioned previously, the PRB is asymmetric, with a northwest-trending axis parallel to the west edge of the basin. Coal beds dip about 2° to the west along the east edge of the basin and about 20°–25° to the east along the west edge of the basin. Stripping ratios for present surface mining along the east edge of the basin are between 1:1 and 3:1. Figure 19 shows the stripping ratio for the Roland (Baker, 1929), Smith, Anderson, Dietz 3, Canyon, Lower Canyon, and Werner coal beds. The structural elevation at the top of the Canyon coal bed is shown in figure 20.

8

Northern Wyoming Powder River Basin Coal 3.0 mi from point of measurement) can be established on the basis of distance from a data point (Wood and others, 1983). Coal resource reliability maps were constructed from the digital model for each coal bed assessed.

Paleochannel systems
It is also important to address the influence of paleochannel geometry upon the spatial distribution of the assessed coal beds. The coals originated as peat deposits that accumulated in interchannel raised mires flanked by deposits of a fluvialchannel complex (Ellis and others, 1999).The lenticular coal beds of the Wyodak-Anderson coal zone (Smith, Anderson, Lower Anderson, Dietz 1, Dietz 2, Dietz 3, Dietz 4, Canyon, Lower Canyon, Ferry, and Werner of this report) are laterally split by, and pinch out into, strata that were deposited in the adjacent fluvial channels (Flores and others, 1999). Channel systems can generally be defined by the lack of coalbed methane production drilling within a lease tract, indicating a thinning of coal beds as they approach a channel, or possibly a total absence of coal within the channel. Channel systems not only influence the thickness and areal extent of the coal beds, but they can also influence coal quality. Typically, ash content in the coal increases when the coal approaches channel margins where ash-bearing thin clastic lamina and partings in the coal beds are more numerous. Higher ash content also results in lower Btu content in the coal (Luppens and others, 2008). In summary, the calculation of recoverable resources and extractable reserves is dependent on the identification of geological constraints that are likely to inhibit mining. In the NWPRB assessment area, these geological constraints include the identification and location of faults, steepness of the dip of the coal beds, and identification of or mapping of channel systems.

Upper Healy Coal Bed
The Upper Healy coal bed is the uppermost bed evaluated in this report; it is limited in extent to the southwestern part of the NWPRB assessment area. This coal bed, identified on 68 geophysical well logs, has a maximum thickness of 57.3 ft and an average thickness of 16.4 ft (figs. 10, 21). Areas where thickness exceeds 20 ft are along the western limit of the coal bed. Depth in the area of greatest coal thickness ranges from subcrop to about 500 ft (fig. 22). Approximately 50 percent of the Upper Healy coal is within the “measured” and “indicated” reliability categories (table 1); the resource reliability map is shown in figure 23.

Healy Coal Bed
Limited in extent to the southwestern part of the NWPRB assessment area, the Healy coal bed was identified on 219 geophysical well logs; it has a maximum thickness of 45.9 ft and an average thickness of 16.6 ft (figs. 10, 24). In most places, thicknesses exceed 20 ft. Depth of the bed ranges from shallow subcrop to about 1,000 along the axis of the basin (fig. 25). More than 50 percent of the Healy coal is in the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for this bed is shown in figure 26.

Coal Bed Geology
During this evaluation, 33 coal beds were identified in the NWPRB assessment area (fig. 10). Of that total, 24 were assessed for resource calculations. Inclusion of a coal bed was based on thickness, areal extent, and stratigraphic position in relation to other minable beds. Except for the Upper Healy, Healy, Ucross, Felix, and the Lower Felix coal beds, which are in the Eocene Wasatch Formation, the remaining assessed coal beds are all within the Tongue River Member of the Fort Union Formation (fig. 10). Because a typical surface-mining sequence begins at the ground surface, the following descriptions of coal beds that were assessed in this area are discussed from youngest to oldest. The overburden maps for all the coal beds were projected to the last data point as indicated by the “area of no data” boundary on the overburden maps. Summary data for the coal bed thicknesses and depths were derived from statistical summaries based on coal bed digital models. Coal resources are classified according to geologic assurances of existence or reliability (Wood and others, 1983). The degree of assurance increases with higher densities of geologic data points. Different reliability categories of measured (0.25 mi from point of measurement), indicated (0.25–0.75 mi from point of measurement), inferred (0.75–3.0 mi from point of measurement), and hypothetical (greater than

Ucross Coal Bed
The Ucross coal bed is present in two large areas within the western part of the NWPRB assessment area. The coal bed was identified on 365 geophysical well logs; it has a maximum thickness of 39.5 ft and an average thickness of 6.7 ft (figs. 10, 27). In one small area along the southwestern part of this area, thickness exceeds 20 ft. Depth ranges from shallow subcrop to about 1,000 ft along the axis of the basin (fig. 28). The resource reliability map for this bed is shown in figure 29; about 50 percent of the coal is in the “measured” and “indicated” reliability categories (table 1).

Felix Coal Bed
The extent of the Felix coal bed is limited to one small area in the south-central part of the NWPRB assessment area. This coal bed, identified on 118 geophysical well logs, has a maximum thickness of 27.9 ft and an average thickness of 13.1ft (figs. 10, 30). Two local areas contain coal that exceeds a thickness of 20 ft. Depth ranges from shallow subcrop to more than 500 ft throughout the areas of the thickest part of the coal bed (fig. 31). The coal resource reliability map for this coal bed is shown in figure 32. More than 60 percent of the coal is in the “measured” and “indicated” reliability categories (table 1).

Coal Bed Geology

9

Table 1. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by reliability category in millions of short tons. Resource includes coal plus partings. Reliability categories are based on distance from data point: Measured, <¼ mile; Indicated, ¼–¾ mile; Inferred, >¾–3 miles; Hypothetical, >3 miles. Columns may not sum exactly owing to rounding]

Coal bed name

Reliability category Measured Indicated

Original resources ≥ 2.5 ft thick 242 572 1,097 128 2,039 556 1,225 1,400 10 3,191 307 640 842 156 1,945 222 745 448 0 1,415 996 2,139 2,552 118 5,805 774 1,897 2,497 228 5,396 4,062 9,143 11,310 274 24,789 715 902 1,418 0 3,035

Previously mined 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Land use restrictions 0 3 10 0 13 0 6 3 0 9 0 0 0 0 0 0 0 0 0 0 1 2 2 1 6 9 15 13 0 37 47 54 17 0 118 5 9 1 0 15

Technical restrictions 2 5 16 0 23 19 44 39 8 110 105 220 178 25 528 11 21 28 0 60 121 245 365 33 764 181 425 482 24 1,112 69 152 144 12 377 186 413 639 0 1,238

Available resources 240 564 1,071 128 2,003 537 1,175 1,358 2 3.072 202 420 664 131 1,417 211 724 420 0 1,355 874 1,892 2,185 84 5,035 584 1,457 2,002 204 4,247 3,946 8,937 11,149 262 24,294 524 480 778 0 1,782

Percentage of original resource 99.2 98.6 97.6 100.0 98.2 96.6 95.9 97.0 20.0 96.3 65.8 65.6 78.9 84.0 72.9 95.0 97.2 93.8 0 95.8 87.8 88.5 85.6 71.2 86.7 75.5 76.8 80.2 89.5 78.7 97.1 97.7 98.6 95.6 98.0 73.3 53.2 54.9 0 58.7

Upper Healy

Inferred Hypothetical Total Measured Indicated

Healy

Inferred Hypothetical Total Measured Indicated

Ucross

Inferred Hypothetical Total Measured Indicated

Felix

Inferred Hypothetical Total Measured Indicated

Lower Felix

Inferred Hypothetical Total Measured

Roland (Upper Rider)

Indicated Inferred Hypothetical Total Measured

Roland (Baker, 1929)

Indicated Inferred Hypothetical Total Measured Indicated Inferred Hypothetical Total

Roland (Taff, 1909)

10

Northern Wyoming Powder River Basin Coal

Table 1. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by reliability category in millions of short tons. Resource includes coal plus partings. Reliability categories are based on distance from data point: Measured, <¼ mile; Indicated, ¼–¾ mile; Inferred, >¾–3 miles; Hypothetical, >3 miles. Columns may not sum exactly owing to rounding]

Coal bed name

Reliability category Measured Indicated

Original resources ≥ 2.5 ft thick 2,058 3,307 4,619 245 10,229 5,597 8,844 5,175 174 19,790 667 1,469 606 0 2,742 522 319 60 0 901 469 402 296 0 1,167 8,054 13,136 4,778 393 26,361 295 422 109 0 826 7,587 13,485 6,504 52 27,628

Previously mined 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 6 0 0 9 0 0 0 0 0 6 11 0 0 17 0 0 0 0 0 25 69 20 0 114

Land use restrictions 10 4 0 0 14 199 109 57 0 365 0 0 0 0 0 21 27 1 0 49 65 9 1 0 75 227 100 2 0 329 5 1 0 0 6 129 84 11 0 224

Technical restrictions 128 373 603 24 1,128 126 421 559 33 1,139 141 297 238 0 677 141 97 42 0 280 46 95 124 0 265 104 334 475 116 1,029 103 126 60 0 289 97 315 499 11 922

Available resources 1,920 2,930 4,016 221 9,087 5,272 8,314 4,558 142 18,286 526 1,172 368 0 2,066 357 189 17 0 563 358 298 171 0 827 7,717 12,691 4,302 277 24,986 184 293 47 0 531 7,336 13,017 5,974 41 26,368

Percentage of original resource 93.3 88.6 86.9 90.2 88.8 94.2 94.0 88.1 81.1 92.4 78.9 79.8 60.7 0 75.3 68.4 59.2 28.3 0 62.5 76.3 74.1 57.8 0 70.9 95.8 96.6 90.0 70.5 94.8 62.4 69.4 43.1 0 64.3 96.7 96.5 91.9 78.8 95.4

Smith

Inferred Hypothetical Total Measured Indicated

Anderson

Inferred Hypothetical Total Measured Indicated Inferred Hypothetical Total Measured Indicated

Lower Anderson

Dietz 1

Inferred Hypothetical Total Measured Indicated

Dietz 2

Inferred Hypothetical Total Measured Indicated

Dietz 3

Inferred Hypothetical Total Measured Indicated

Dietz 4

Inferred Hypothetical Total Measured Indicated

Canyon

Inferred Hypothetical Total

Coal Bed Geology

11

Table 1. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by reliability category in millions of short tons. Resource includes coal plus partings. Reliability categories are based on distance from data point: Measured, <¼ mile; Indicated, ¼–¾ mile; Inferred, >¾–3 miles; Hypothetical, >3 miles. Columns may not sum exactly owing to rounding]

Coal bed name

Reliability category Measured

Original resources ≥ 2.5 ft thick 5,428 8,430 5,015 76 18,949 558 1,702 2,869 66 5,195 6,444 14,824 8,544 284 30,095 5,170 14,093 11,670 1,041 31,974 3,878 10,317 10,370 749 25,314 1,172 3,138 2,903 1,651 8,864 1,193 3,125 4,020 497 8,835 1,201 5,278 11,961 550 18,990

Previously mined 0 4 9 0 13 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Land use restrictions 50 74 4 0 128 0 0 0 0 0 44 18 0 0 62 0 0 0 0 0 0 0 0 0 0 3 2 0 0 5 0 0 0 0 0 0 0 0 0 0

Technical restrictions 138 476 734 57 1,405 88 205 395 49 737 100 257 280 60 697 96 340 593 197 1,226 107 424 946 103 1,578 67 283 668 337 1,355 115 506 966 172 1,759 100 404 947 339 1,790

Available resources 5,240 7,876 4,268 19 17,403 470 1,497 2,474 17 4,458 6,299 14,545 8,258 224 29,326 5,074 13,753 11,077 844 30,748 3,771 9,893 9,424 646 23,734 1,102 2,853 2,235 1,314 7,504 1,078 2,619 3,054 325 7,076 1,101 4,874 11,014 211 17,200

Percentage of original resource 96.5 93.4 85.1 25.0 91.8 84.2 88.0 86.2 25.8 85.8 97.7 98.1 96.7 78.9 97.4 98.1 97.6 94.9 81.1 96.2 97.2 95.9 90.9 86.2 93.8 94.0 90.9 77.0 79.6 84.7 90.4 83.8 76.0 65.4 80.1 97.7 92.3 92.1 38.4 90.6

Lower Canyon

Indicated Inferred Hypothetical Total Measured Indicated

Ferry

Inferred Hypothetical Total Measured Indicated

Werner

Inferred Hypothetical Total Measured Indicated

Otter

Inferred Hypothetical Total Measured Indicated

Gates

Inferred Hypothetical Total Measured Indicated

Pawnee

Inferred Hypothetical Total Measured Indicated

Odell

Inferred Hypothetical Total Measured Indicated

Oedekoven

Inferred Hypothetical Total

12

Northern Wyoming Powder River Basin Coal

Table 1. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by reliability category in millions of short tons. Resource includes coal plus partings. Reliability categories are based on distance from data point: Measured, <¼ mile; Indicated, ¼–¾ mile; Inferred, >¾–3 miles; Hypothetical, >3 miles. Columns may not sum exactly owing to rounding]

Coal bed name

Reliability category Measured Indicated

Original resources ≥ 2.5 ft thick 58,167 119,553 101,063 6,692 285,474

Previously mined 34 90 29 0 153

Land use restrictions 815 517 122 1 1,455

Technical restrictions 2,392 6,482 10,025 1,600 20,488

Available resources 54,923 112,463 90,884 5,092 263,376

Percentage of original resource 94.4 94.1 89.9 76.1 92.3

Total beds

Inferred Hypothetical Total

Lower Felix Coal Bed
The Lower Felix coal, the lowest bed identified in the Eocene Wasatch Formation, is present in a large area in the southwestern part of the NWPRB assessment area. It was identified on 516 geophysical well logs; it has a maximum thickness of 52.1 and an average thickness of 9.8 ft (figs. 10, 33). There are three areas where thickness exceeds 20 ft. Depth ranges from zero to more than 1,000 ft along the axis of the basin (fig. 34). The coal resource reliability map for the Lower Felix bed is shown in figure 35. More than 50 percent of the coal is within the “measured” and “indicated” reliability categories (table 1).

(fig. 10). The Roland was identified on 1,797 geophysical well logs. With a maximum thickness of 34.5 ft and an average thickness of 13.9 ft (figs. 10, 39), it is continuous throughout most of the western and south-central parts of the NWPRB assessment area and correlates eastward with the Roland coal bed of Luppens and others (2008) in the Gillette coal field. The largest area where the Roland coal exceeds a thickness of 20 ft is in the west-central to southwestern part of the area. Depth exceeds 1,500 ft along the axis of the basin (fig. 40). Approximately 60 percent of the coal is within the “measured” and “indicated” reliability categories (table 1), the distributions of which are shown in figure 41.

Roland (Upper Rider) Coal Bed
The Roland (Upper Rider) coal bed is an upper split of the Roland coal bed (Baker, 1929). It is most continuous throughout the central part of the NWPRB assessment area, where it reaches a maximum thickness of 19.8 ft. A smaller area containing this coal is present in the extreme southwestern part of this area. The bed was identified on 851 geophysical well logs, the interpretations of which indicated an average thickness of 6.3 ft (figs. 10, 36). Where present, its top marks the contact between the Wasatch and Fort Union Formations. Depth of the bed ranges from subcrop to more than 1,500 ft to the west of the axis of the basin (fig. 37). Approximately 40 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The resource reliability map for this coal bed is shown in figure 38.

Roland of Taff Coal Bed
The Roland of Taff (1909) coal bed is present in three areas within the western part of the NWPRB assessment area. The coal bed, identified on 866 geophysical well logs, has a maximum thickness of 25.6 ft and an average thickness of 5.1 ft (figs. 10, 42). Maximum depth is about 1,500 ft along the axis of the PRB in the extreme southwestern part of this area (fig. 43). The coal resource reliability map for this coal bed is shown in figure 44. Approximately 50 percent of the coal is within the “measured” and “indicated” reliability categories (table 1).

Smith Coal Bed
The Smith coal bed, as identified on 1,310 geophysical well logs, has a maximum thickness of 33.8 ft and an average thickness of 8.3 ft (figs. 10, 45). The unit is fairly continuous throughout the western half of the NWPRB assessment area and correlates with the Smith coal bed of Luppens and others (2008) in the Gillette coal field. Depth ranges from shallow subcrop to more than 2,000 ft along the axis of the basin (fig. 46). Coal resource reliability categories of the Smith bed are shown in figure 47; more than 50 percent of the coal is within the “measured” and “indicated” reliability categories (table 1).

Roland of Baker Coal Bed
Where the Roland (Upper Rider) coal bed is absent, the Roland of Baker (1929) coal bed is stratigraphically the highest coal bed within the Tongue River Member of the Fort Union Formation and is generally considered to mark the contact with the Wasatch Formation (Flores and others, 1999)

Coal Bed Geology

13

Anderson Coal Bed
The Anderson coal bed, as interpreted from 2,089 geophysical well logs, has a maximum thickness of 46.5 ft (figs. 10, 48), averages 11.3 ft thick, and correlates with the Anderson coal bed in the Gillette coal field (Luppens and others, 2008). The bed is present in two large portions of the NWPRB assessment area separated by a channeled area (labeled channel, fig. 48) in which it is thin to absent. As documented in the Gillette coal field report by Luppens and others (2008), paleochannels are identified by their lenticular shape, absence of coal, and thinning of coal along the edges of the channel, all of which are apparent in figure 48. The Anderson coal bed was correlated by Baker (1929) with the Dietz 1 coal beds; it was also referred to as the Dietz 1 by the Pittsburg and Midway Coal Mining Company in the PSO proposed mine area in the Sheridan coal field (fig. 4) and is one of the two principal minable coal beds in this area. However, the Anderson is here interpreted to be a separate bed and the Dietz 1 to be a lower split. The Anderson, Dietz 3, and Canyon coal beds (described below), constitute the principal coalbed methane targets in the area. Guidelines discussed in the methodology section of this report were used to separate the Anderson, Dietz 1, Dietz 2, Dietz 3, and Dietz 4 into separate beds. The entire sequence of coals is part of the Wyodak coal zone of Molnia and others (1999). In the Sheridan coal field the separation between the Anderson and Dietz coal beds changes from a few inches to several feet within a short distance; regionally, the interburden ranges from an inch to several feet. Depth of the Anderson coal bed ranges from shallow subcrop along the east edge of the NWPRB assessment area to more than 1,500 ft along the axis of the basin (fig. 49). As seen in the resource reliability category map of the Anderson coal bed, there has been a significant amount of drilling throughout the area underlain by the coal bed (fig. 50). More than 60 percent of the coal is within the “measured” and “indicated” reliability categories (table 1).

6.0 ft thick (figs. 10, 54). Dietz 1 coal thickness greater than 10 ft is limited to several small areas in the northwestern part of the Sheridan coal field. Depth of the Dietz 1 coal bed ranges from shallow subcrop to more than 1,500 ft along the axis of the basin (fig. 55). More than 90 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Dietz 1 bed is shown in figure 56.

Dietz 2 Coal Bed
The Dietz 2 coal bed is present only in isolated areas in the northwestern and central parts of the NWPRB assessment area. The bed, which was identified on 430 geophysical well logs, has a maximum thickness of 28.3 ft and an average thickness of 6.7 ft (figs. 10, 57). Thicknesses greater than 20 ft are limited to a small area in the Sheridan coal field, where the Dietz 1 merges with the Dietz 2 and Anderson coal beds. Depth to the Dietz 2 coal bed ranges from shallow subcrop to more than 1,500 ft (fig. 58). More than 75 percent of the coal is within the “measured” and “indicated” reliability categories (table 1).The coal resource reliability map for the Dietz 2 bed is shown in figure 59.

Dietz 3 Coal Bed
The Dietz 3 coal bed is present in two large areas of the NWPRB assessment area, one in the northwestern part, and the other in the central part (fig. 60). Within the latter area, the bed locally attains a thickness of about 70 ft. The Dietz 3, which was identified on 2,280 geophysical well logs, has an average thickness of 16.2 ft (figs. 10, 60). The combined Anderson, Canyon, and Dietz 3 coal beds form one of the most important coal zones in the area. In the Sheridan coal field, the Dietz 3 is the primary minable coal bed for the PSO lease area of Pittsburg and Midway Coal Mining Company (fig. 4). The Dietz 3 coal bed correlates with the Dietz coal bed in the Gillette coal field (Luppens and others, 2008). Within the Sheridan coal field, the Dietz 3 merges and splits with the Dietz 1 and Dietz 2, but ultimately it becomes the dominant bed. Depth of the Dietz 3 coal bed ranges from shallow subcrop to more than 2,000 ft along the axis of the basin (fig. 61). More than 75 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Dietz 3 bed is shown in figure 62. As shown in the Dietz 3 isopach map, there are two significant channel systems, both trending northerly through the NWPRB assessment area (east channel and west channel in fig. 60). The west channel is the same channel observed in both the Anderson and Lower Anderson isopach maps (figs. 48, 51). It bisects the entire area, attains a width of some 25 mi, and gradually thins along both margins. The east channel is much narrower but also completely erodes out the coal bed.

Lower Anderson Coal Bed
The Lower Anderson coal bed is a lower split of the Anderson coal bed. Figure 51 shows that its subsurface extent is limited to the south-central part of the NWPRB assessment area, with an intervening area that is essentially devoid of coal. Maximum thickness of the bed is 43.8 ft in the south-central part of the area; average thickness is 6.6 ft thick (fig. 10), and depth ranges from shallow subcrop to more than 1,500 ft (fig. 52). Coal resource reliability categories of the Lower Anderson are shown in figure 53. “Measured” and “indicated” resource reliability categories total more than 70 percent of the extent of the coal bed (table 1).

Dietz 1 Coal Bed
The Dietz 1 coal bed was identified on 635 geophysical well logs; it has a maximum thickness of 28.2 ft and averages

14

Northern Wyoming Powder River Basin Coal

Dietz 4 Coal Bed
The Dietz 4 coal bed is present in relatively limited areas of the NWPRB assessment area (fig. 63). The bed, which was identified on 384 geophysical well logs, reaches a maximum thickness of 19.9 ft and has an average thickness of 5.3 ft (figs. 10, 63). Depth ranges from shallow subcrop to more than 2,000 ft along the axis of the basin (fig. 64). More than 80 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). Reliability categories of the Dietz 4 coal bed are shown in figure 65.

Ferry Coal Bed
The Ferry coal bed, identified on 328 geophysical well logs, has a maximum thickness of 25.4 ft. Although relatively thin (average thickness 7.1 ft), it is continuous across the southcentral and southwestern parts of the NWPRB assessment area (figs. 10, 72). Depth ranges from shallow subcrop to more than 2,500 ft along the axis of the basin (fig. 73). Approximately 40 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Ferry bed is shown in figure 74.

Canyon Coal Bed
Originally named the Monarch coal bed by Taff (1909), this coal bed is equivalent to the Canyon coal bed as defined by Baker (1929) (Law and others, 1979). Since that time it has been referred to as both the Canyon and the Monarch. In this report it will be referred to as the Canyon coal bed and correlated with the Canyon coal bed in the Gillette coal field (Luppens and others, 2008). The unit is present throughout most of the NWPRB assessment area and was identified on 2,596 geophysical well logs. It reaches a maximum thickness of 80.0 ft with an average thickness of 13.3 ft (figs. 10, 66). Depth ranges from shallow subcrop to about 2,500 ft along the axis of the basin (fig. 67). In the east-central part of the area, overburden is considerably thinner over the thickest part of the coal bed. More than 70 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Canyon bed is shown in figure 68. One large channel system can be observed in the southcentral part of the Canyon isopach map (labeled channel in fig. 66). It is probably an extension of the large north-southtrending channel system along the western edge of the Gillette coal field that was identified by Luppens and others (2008). Coal thins rapidly along the margins of this channel.

Werner Coal Bed
Present in the northern part of the Gillette coal field, the Werner coal bed extends into the central part of the NWPRB assessment area, as identified on 1,764 geophysical well logs. It reaches a maximum thickness of 63.5 ft within the eastcentral part of the area and has an average thickness of 16.2 ft (figs. 10, 75). Depth ranges from shallow subcrop to more than 3,000 ft along the axis of the basin (fig. 76). More than 70 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Werner bed is shown in figure 77. The channel system in the Canyon and Lower Canyon coal beds (figs. 66, 69) can also be observed in the Werner isopach map (labeled channel) (fig. 75). Gradual thinning of the coal bed along the margins of the channel is similar to the Canyon and Lower Canyon coal beds.

Otter Coal Bed
The Otter coal bed is present throughout much of the NWPRB assessment area and was identified on 1,553 geophysical well logs. Maximum thickness of 63.2 ft is in the south-central part of this area, and average thickness is 14.6 ft (figs. 10, 78). Depth ranges from shallow subcrop to about 4,000 ft along the axis of the basin (fig. 79). More than 50 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Otter bed is shown in figure 80.

Lower Canyon Coal Bed
The Lower Canyon coal bed is a lower split of the Canyon coal bed. The thickest deposits, as interpreted from 2,163 geophysical wells, are in the central and northwestern parts of the NWPRB assessment area (fig. 69). Maximum thickness is 53.8 ft within the south-central area and average thickness is 10.9 ft (figs. 10, 69). It is also channeled in the same general area as the Canyon bed (fig. 66). Depth ranges from shallow subcrop to more than 2,000 ft along the axis of the basin (fig. 70). More than 70 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Lower Canyon bed is shown in figure 71.

Gates Coal Bed
The Gates coal bed is also present throughout most of the NWPRB assessment area. As interpreted from 1,536 geophysical well logs, it reaches a maximum thickness of about 45.4 ft within the southeastern part of this area and has an average thickness of 10.5 ft (figs. 10, 81). Depth ranges from shallow subcrop to about 4,000 ft along the axis of the basin (fig. 82). More than 40 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Gates bed is shown in figure 83.

Resource Allocation Planning

15

Pawnee Coal Bed
Distribution of the Pawnee coal bed is shown in figure 84. On the basis of 766 geophysical well logs, it reaches a maximum thickness of 27.6 ft in the eastern part of the NWPRB assessment area and has an average thickness of 6.9 ft (figs. 10, 84). Depth ranges from shallow subcrop to about 4,000 ft along the axis of the basin (fig. 85). More than 60 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Pawnee coal bed is shown in figure 86.

Odell Coal Bed
The Odell coal bed is present in the eastern, central, and southern parts of the NWPRB assessment area (fig. 87) and was identified on 760 geophysical well logs. It has a maximum thickness of 25.5 ft within the eastern part of this area, and its average thickness is 7.2 ft (figs. 10, 87). Depth ranges from shallow subcrop to about 4,000 ft along the axis of the basin (fig. 88). More than 40 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Odell bed is shown in figure 89.

Roberts Coal Bed
The Roberts coal bed is distributed throughout much of the NWPRB assessment area (fig. 90). On the basis of 608 geophysical well logs, it reaches a maximum thickness of 37.9 ft and has an average thickness of 10.9 ft (figs. 10, 90). Depth ranges from shallow subcrop to more than 4,000 ft along the axis of the basin (fig. 91). More than 40 percent of the coal is within the “measured” and “indicated” reliability categories (table 1). The coal resource reliability map for the Roberts bed is shown in figure 92.

Resource Allocation Planning
The objective in resource planning is to determine the available resources. This objective is accomplished by first subtracting the resources previously mined from the original resources; the result equals the remaining resources. Subtracting the land use and technical restrictions from the remaining resources equals the available resources. The following discussion details the methodology used in determining available resources. Geologic digital modeling for the evaluated coal beds was done using PC/Cores (Mentor Consultants, 2005). In the next step of the coal resource assessment, files were imported into a geographic information system (GIS). The GIS system was used to allocate coal resources, by first subtracting areas with various restrictions to mining (previous mining, towns, railroads, and alluvial valley floors) in order to calculate the amount of available coal.

ArcView and the ArcView Spatial Analyst extension (Environmental Systems Research Institute, Inc., 2000, 2001) were used to perform the various GIS analyses and ultimately calculate coal resource volumes. In addition, ArcGIS (Environmental Systems Research Institute, Inc., 2006) was used in some cases to project digital coverages, shapefiles, or grids to the assessment area’s base map projection. The geographic referencing base of the digital data used for the GIS analysis is the Universal Transverse Mercator (UTM) map projection, using the following parameters: map units=meters; zone=13; datum=NAD27; and spheroid=Clarke 1866. USGS coal resource assessments do not have a standard grid-cell size that is used for all GIS analyses. For this GIS assessment, a grid-cell size of 246 ft (75 m) on a side was chosen. Consequently, all grids used within the GIS analysis were either originally created with a grid cell size of 246 ft or resampled to 246 ft from another cell size. The first task in the GIS analysis involved the creation of ArcView (Environmental Systems Research Institute, Inc., 2000) -readable grids from ASCII files of the coal, parting, and overburden isopach grids that were created as part of the digital coal models. These ArcView grids were used to create a total thickness (coal plus parting) grid and an arealextent grid for each coal bed to be evaluated. The next task involved creating a group of grids that contained all of the attributes needed for coal resource analysis for the NWPRB assessment area, with each grid representing one specific theme. These grid themes consisted of restrictions to mining (such as previously mined coal, land use restrictions (including environmental), technical restrictions, and unsuitability criteria), overburden-to-coal bed ratios, coal ownership, resource reliability categories, and coal bed depth. The grid themes for mined out areas, land-use restrictions, and coal ownership were derived from digital information obtained from the Wyoming Bureau of Land Management. The grid theme for the counties was developed from a digital file of Wyoming county lines obtained from the Wyoming Spatial Data Clearinghouse (2009) (http://wgiac2.state.wy.us). The other grid themes were developed independently for this evaluation. The grid of environmental restrictions (such as towns, roads, railroads and previously mined areas), includes buffer zones that surround these areas. The location and width of these buffers are commonly mandated by State or Federal regulations, but specifications presented in the Buffalo Resource Management Plan (U.S. Bureau of Land Management, 2001), such as additional buffers around the town of Sheridan, Wyoming, were also used in this evaluation. Each restriction buffer measures hundreds or, in the case of the extra-jurisdictional buffer around the town of Sheridan, thousands of feet in width at the surface, as discussed in the following section on factors affecting coal resources. One of the improvements in the assessment methodology was revising the technique for defining surface restrictions at depth. Previous economic assessments used a simple “cookie cutter” approach when they applied regulatory surface buffers

16

Northern Wyoming Powder River Basin Coal

(such as a 300-ft buffer around an inhabited house) below the surface. The surface buffers were simply projected vertically downward through the coal beds to be evaluated. However, a restricted area actually widens with depth when surface mining operations are considered, owing to the additional distance required to maintain a safe mining pit highwall angle. Consequently, the area that is affected by a restriction becomes larger, the deeper a coal bed lies beneath the surface. For example, a circular restriction at the surface having a diameter of 600 ft encompasses an area of about 282,600 ft2, or approximately 6.5 acres. At a depth of 200 ft, however, this same restriction has a diameter of 858 ft encompassing an area of about 577,900 ft2, or approximately 13 acres, whereas at a depth of 500 ft the restriction has a diameter of 2,144 ft and encompasses an area of about 3,608,400 ft2, or approximately 83 acres. Figure 93 illustrates the effect of depth on overall land-use restriction size. Technical restrictions grids were also made that included (1) areas where coal beds are less than 2.5 ft thick and (2) areas where coal beds are less than 5 ft thick. For this evaluation, coal resources of less than 2.5 ft in thickness (which are subbituminous in apparent rank) are not considered to represent viable resources. Coal resources greater than 2.5 ft thick but less than 5.0 ft thick are not considered to represent currently minable resources or potential reserves. The grid of previously mined out areas accounted for all previous mining within the NWPRB assessment area, including those mines shown in figure 94. The counties grid contained locations of three counties within this area (Sheridan, Campbell, and Johnson). The coal mineral ownership grid divided the area into Federal, State, and private ownership categories (fig. 95). The resource reliability grid divided the area into measured, indicated, inferred, and hypothetical coal resources, whereas the coal bed depth grid divided the area into four categories of depth:0–500 ft; 500–1,000 ft; 1,000–2,000 ft; and greater than 2,000 ft. Thickness grids were created, and reliability grids for measured, indicated, inferred, and hypothetical were also created. Once all the individual theme grids were generated, the next step was to apply these grids to the coal resources of the 24 coal beds to be evaluated. First, the individual theme grids were combined into one composite themes grid, which was then used with the coal bed areal-extent grids to define resources of the NWPRB assessment area on a bed-by-bed basis according to all the various categories. Next, areas within each coal bed that represented previously mined coal and restrictions (land-use and technical) were removed from consideration. For this assessment of the NWPRB assessment area, coal resources were allocated to separate stripping-ratio areas for seven of the 24 evaluated coal beds (fig. 19). These coal beds—Roland of Baker, (1929), Smith, Anderson, Dietz 3, Canyon, Lower Canyon, and Werner—represent potentially minable resources within the foreseeable future. However, areas where these coal beds are less than 5 ft thick are considered technically restricted for surface mining.

Factors Affecting Extraction of Coal Resources
Many factors affect the availability of coal for mining. About 73 percent of the coal in the NWPRB assessment area is owned by the Federal government and must be leased in order to be mined. A four-step coal screening process, defined in the 43 Code of Federal Regulations (CFR) 3420.1-4 regulations (Office of the Federal Register, 2003), determines which areas of Federal coal are acceptable for leasing. The following list shows coal-leasing unsuitability criteria listed in the Code of Federal Regulations, Title 43 Subpart 3461.5 (43 CFR 3461.5).
Unsuitability Criteria
Federal land systems Rights-of-way and easements (e.g., railroads) Dwellings, roads, cemeteries, and public buildings Wilderness study areas Lands with outstanding scenic quality Lands used for scientific study Historic lands and sites Natural areas Critical habitat for threatened or endangered plant and animal species State listed threatened or endangered species Bald or golden eagle nests Bald and golden eagle roost and concentration areas Federal lands containing active falcon cliff nesting site Habitat for migratory bird species Fish and wildlife habitat for resident species Floodplains Municipal watersheds National resource waters Alluvial valley floors State or Indian tribe proposed criteria

These 20 specific legal criteria are used to determine if an area is unsuitable for leasing and surface mining. The criteria were established by the Surface Mining Control and Reclamation Act of 1977 (Public Law 95-87, 1977). The unsuitability criteria require consideration of land use, scenic areas, natural areas, historic sites, wildlife habitats, flood plains, alluvial valley floors, and other special lands. Although developed for lands owned by the Federal government, many of the criteria are also applicable to State-owned and privately owned lands. For example, areas containing threatened or endangered plant or animal species are protected from destruction. Municipal watersheds are likewise protected from detrimental actions regardless of who owns the land. It is important to emphasize that not all criteria in the above list affect development within the NWPRB assessment area. Other potential restrictions to mining include land use restrictions such as airports, archaeological areas, coalbed methane wells, oil and oil-related gas wells, pipelines, power lines, rivers, lakes, streams, and towns. Restrictions to mining vary with location and local land-management regulations. Thus, different study areas can

Factors Affecting Extraction of Coal Resources have different mining restrictions and availability considerations. This report reflects assumptions concerning restrictions to mining that are based on local practices in the PRB and specifically to those practices within the NWPRB assessment area. In addition, Bureau of Land Management personnel in Casper, Wyoming, provided guidance concerning restrictions to mining and the distances to be buffered around specific features and also provided files that delineate many of the features and the buffer distances used for the study. Because required buffer distances can change through time, distances were selected that were considered the maximum amount likely to be required by future regulations. A more detailed determination of restrictions and other availability considerations would be necessary as part of the leasing and mineplanning phases of property development. Figure 94 shows the areas within the NWPRB assessment area that were affected by land-use restrictions. In some cases, an area that was originally declared unavailable for coal mining could have a mitigation measure that would permit mining. The following is a detailed discussion of potential mining restrictions for this area. All buffer restrictions refer to surface distances.

17

Dwellings and Buildings
Individual dwellings and buildings that exist within the NWPRB assessment area, outside of the incorporated area of Sheridan, Wyoming, are not considered to be restrictions to mining. These individual structures could potentially be purchased by a coal company, which could then move or raze them in order to proceed with mining.

Alluvial Valley Floors
All areas identified as alluvial valley floors by the State program delegated to enforce the Surface Mining Control and Reclamation Act of 1977 (Surface Mining Control and Reclamation Act, Public Law 95-87), where mining would interrupt, discontinue, or preclude farming, are unsuitable for surface coal mining and thus are deemed to be restrictions (fig. 94). Areas outside alluvial valley floors where mining would materially damage the quantity or quality of water supplying alluvial valley floors are also considered unsuitable for mining; however, this assessment did not include those areas as restrictions.

Federal Land Systems
No Federal lands systems unsuitable for coal leasing are in the NWPRB assessment area. Where the mineral ownership is Federal, the Bureau of Land Management develops coal-leasing and mining stipulations in cooperation with the U.S. Forest Service. Federal, state, and private subsurface coal ownership is shown in figure 95.

Airports
The Sheridan County airport is located adjacent to the city of Sheridan; about 2 mi southwest of the central business district, and it is included within the Sheridan restriction buffer area.

Archaeological Areas
No major archaeological areas that would prevent mining are known in the NWPRB assessment area. There are several minor archaeological sites and also several minor historic sites within this area. A mitigation plan would be developed before coal mining disturbed these areas. Therefore, coal within these known sites was not excluded from this resource study.

Railroads
There is one main railroad route through the NWPRB assessment area (fig. 94), the southeast-northwest rail line of the Burlington Northern Santa Fe Railway. About 5 mi to the east of the town of Sheridan, a spur rail line runs north from the main line to the Spring Creek mine in Montana. It is assumed that the spur rail would be moved; therefore, the spur rail is not considered to be a restriction to mining. The total restricted width for the main rail line, including the right-ofway and a 100-ft buffer along each side, is 600 ft.

Coalbed Methane
The rapid growth in coalbed methane production within the NWPRB assessment area has resulted in the placement of thousands of wells, along with their accompanying pipeline infrastructure, throughout the area (fig. 6). Designating all of these wells and their extensive gas delivery systems as being restrictive to mining would effectively exclude most of the assessment area from resource consideration. As stated previously, the expected lifetime of these wells in this area, producing from a single coal bed, is 10 to 12 yr. The Bureau of Land Management has designated Conflict Administration Zones to minimize conflicts between coal mines and coalbed methane wells in the path of projected near-term mining. For the purpose of this study, it is assumed that coal within any part of the assessment area will be mined after methane operations have ceased. Therefore, these facilities are not considered a restriction to mining.

Roads
County roads (mostly gravel) cross many areas throughout the NWPRB assessment area. These roads are not considered to be restrictions to mining because it is assumed that they could easily be relocated or temporarily blocked off to allow mining to proceed. In addition, there are a number of paved State and United States highways that could be relocated to allow for mining. However, Interstate Highway 90, which trends north-south through the west side of this area (fig. 94), does pose a restriction to mining that was considered to be 450 ft wide, including the highway right-of-way and a 100-ft buffer on each side.

18

Northern Wyoming Powder River Basin Coal

Oil and Gas Wells
Hundreds of oil and gas wells are located throughout the NWPRB assessment area. Resolution of land-use conflicts between coal mining and oil and gas field development will depend on economic conditions, regulations, and negotiations between oil developers and coal developers. An area around a major cluster of active wells might be eliminated from mining activities until these wells are no longer actively producing, or mining activities might proceed around individual active wells that are given a buffer zone. Conversely, specific wells might be plugged and then reestablished after mining. For this study, it was assumed that the wells will no longer be actively producing when mining operations reach them and thus they are not considered to be restrictions to mining.

Towns
The municipalities of Sheridan, Ranchester, and Clearmont are located within the NWPRB assessment area and are permanent restrictions to mining (fig. 94). In addition to the actual incorporated area, the mining restriction for each municipality includes a buffer that extends beyond the municipality limits. The boundary of the town buffer for Sheridan is taken from the Buffalo Resource Management Plan Update (U.S. Bureau of Land Management, 2001) developed by the Bureau of Land Management for potential coal development areas within the PRB of Wyoming. The buffers for Ranchester and Clearmont extend out to a distance of 300 ft beyond each town’s limits.

State Lands
There are no State parks, forests, or specially designated State lands within the NWPRB. Therefore, there are no State lands that are considered to be restrictions to mining for this evaluation.

Pipelines
There is a network of underground oil and gas pipelines throughout the NWPRB assessment area. Probably most, if not all, of these pipelines would be moved so that surface mining could proceed. However, moving and restoring them would represent an added economic cost to mining. In any case, pipelines were not considered to be restrictions to mining for this study.

Coal Reserve Evaluation Methodology
The third and final phase in the resource assessment is the application of technical restrictions and the economic evaluation of the available resources calculated in phase two (fig. 7). This phase begins by selecting the available resources information for each evaluated bed and parsing them into strippingratio increments. The coal beds selected for the reserves evaluation are the Roland of Baker (1929), Smith, Anderson, Dietz 3, Canyon, Lower Canyon, and Werner. These beds were selected on the basis of their relatively broad areal extent of coal greater than 5 ft thick. In the extreme southwestern portion of the NWPRB assessment area, there is a relatively limited area of potentially mineable Wasatch coal beds (Upper Healy, Healy, Ucross, Felix, and Lower Felix). These coal beds are the northernmost extension of the Buffalo coal field (Glass, 1977). Using mining economics with a discounted cash flow analysis at 8.0 percent rate of return, recoverable coal resources were calculated. That portion of the recoverable coal that is economically minable at or below the current sales price of coal is designated as reserves. In addition to the surface minable resources, the NWPRB assessment area study included a preliminary assessment of the potential of underground minable resources. A considerable volume of the coal resources in this area are contained in relatively thinner beds at greater depth and greater stripping ratios than the Gillette coal field assessment (Luppens and others, 2008). Underground recovery may offer a more practical alternative for those deeper beds in the future. Underground minable resources are discussed later in this report.

Power Lines
All power lines within the assessment area could be moved to accommodate surface mining operations. Thus, power lines are not considered a restriction to mining in this area.

Rivers, Lakes, and Streams
The Powder River, Tongue River, and Little Powder River constitute the major flowing watercourses within the NWPRB assessment area. These and their tributaries consist mostly of shallow, meandering streams throughout the area. Therefore, surface mining operations could temporarily redirect the channels and then return them to their original locations during mine reclamation. Only those parts of the watercourses that have been designated by the State Land Quality Division as alluvial valley floors significant to farming would need to be preserved with no modification. Shallow lakes and small ponds exist that could either be temporarily moved during mining or simply be reformed after the mining operations ceased. However, a small northern part of Lake De Smet is located within this area and is considered to be a restriction to mining for this assessment (fig. 94). The restriction includes a 100-ft buffer surrounding that part of the lake.

Coal Reserve Evaluation Methodology

19

Geologic Aspects of Mine Model Development
There are significant differences in the basic coal geology of the Gillette coal field (Luppens and others, 2008) and that of the NWPRB assessment area, and these differences can appreciably influence the economic analysis. To better address the mining conditions in this area, a new mining model was developed rather than using the CoalVal model used for the Gillette coalfield assessment (Luppens and others, 2008) Typically, mining costs will be higher for the recovery of multiple beds as opposed to a single bed scenario which was used in the Gillette coal field (Luppens and others, 2008). For the Gillette coal field, the exceptionally thick Anderson and Canyon bed sequence dominated the economic evaluation. These two coal beds are generally close to each other stratigraphically, with little or no separation by parting material. The Roland, Smith, Anderson Rider, and Dietz coal beds stratigraphically above the Anderson and Canyon beds were also included in the Gillette coal field mine models. The Anderson and Canyon beds accounted for about 82 percent of the total recoverable resources in the Gillette coal field. Additionally, this thick coal interval represented more than 90 percent or more of the resources down to the 6–7:1 stripping ratio interval. Thus, aggregating all the coal beds into a single composited-bed mine model for the Gillette coal field provided an appropriate practical regional mining model. However, in the northern portion of the Gillette coal field, the Anderson and Canyon beds begin to split apart and thin northward towards the NWPRB assessment area (fig. 96). Furthermore, the Canyon bed splits into the Canyon and Lower Canyon beds in this area. The same methodology of parsing out the coal resources by composite stripping-ratio increments used in the Gillette coal field assessment (Luppens and others, 2008) was also used in the NWPRB assessment. However, with more beds that have a thinner average thickness throughout a larger stratigraphic interval, the approach to the coal reserve evaluation model for the NWPRB assessment area had to be modified from the composited single seam approach used for the Gillette coal field. Further complicating the development of a regional mining model for this area is the fact that not all beds are present everywhere. This spottiness is especially true for coal beds at lower stripping ratios. For example, in the 2:1 ratio areas, some areas contain the Werner and Lower Canyon or Lower Canyon and Canyon, or other bed combinations. For stripping ratios of 5:1 or greater, five or six of the assessed beds are typically present. Interburden thicknesses between the beds are also variable. To develop a single regional model with bed and interburden variability represented a challenge. A straightforward modeling approach was needed that still addressed the multiple seam situations in this area. To simplify the development of a NWPRB assessment area regional mining model and keep it as accurate as practical, a representative model-bed section was built based on approximate average thicknesses of the seven coal beds assessed for reserves and those of the interburden intervals.

The regional mining model stratigraphic sequence that was used for the economic evaluation is shown in table 2. One coal bed is modeled at the 1:1 ratio. From 2:1 through the 4:1 ratios, additional coal beds are added. Because the coal beds in lower ratio models are highly variable, the coal beds are labeled bed 1, bed 2, and so on rather than using specific bed names. For the 5:1 through the 10:1 ratios, six coal seams are modeled. To help simplify the models, interburden thicknesses remain constant and additional overburden is increased for the 5:1+ ratio models. Although the mining model utilized is a simplification of the actual conditions, it was felt that this approach still provided a more realistic representation than the single seam model scenario used in the Gillette coal field assessment (Luppens and others, 2008), especially given the fact that the economic assessments for these study areas in the PRB are done only on a prefeasibility level.

Coal Quality
Coal quality is a major factor in its marketability and is an important input parameter for cost calculations. Quality parameters, such as ash content and heat of combustion (British thermal unit [Btu]), influence operating and maintenance costs at coal-fired power plants. Furthermore, there are government restrictions that aid in the reduction of potentially hazardous air pollutants (Public Law 101-549, 1990). Therefore, coals with lower ash and sulfur content, higher heat contents, and low content of hazardous air pollutants command a higher price.

In-Place Coal Quality
Owing to the lack of significant historical mining except for the relatively small areas of the Sheridan coal field in the extreme northwest corner of the NWPRB assessment area (fig. 3), coal quality data for coal in this area are sparse. In general, coal quality in the area is best near the Sheridan coal field and decreases to the east and southeast. Available quality data from the Sheridan coal field indicates typical ranges, on an as-received basis, as follows: moisture, 20.0−26.0 percent; ash, 3.1−7.0 percent; sulfur, 0.3−0.7 percent; and heat content, 9,000−9,800 Btu/pound (Baker, 1929; Glass, 1980; Ellis and others, 1999; U.S. Bureau of Land Management, 2003a). Most of the coal resources at less than a 10:1 stripping ratio are in the eastern third of the NWPRB assessment area (fig. 19). Unfortunately, little coal quality data from the eastern half of this area are available. Therefore, it was assumed that the quality in the eastern part of this area is similar to that of the northern mining area of the Gillette coal field, which has an in-place average of moisture, 30.04 percent; ash, 6.29 percent; sulfur, 0.39 percent; and heat content, 8,203 Btu/lb (Luppens and others, 2008). The average in-place quality of coal from the Buckskin mine in the Gillette coal field, the closest active mine to this area, is moisture, 29.9 percent; ash, 5.2 percent; sulfur, 0.35 percent; and heat content, 8,400 Btu/lb (Keystone Coal Industry Manual, 2005). Therefore, published coal sales prices

20

Northern Wyoming Powder River Basin Coal replacement capital expenses, and operating costs for each major operational activity, including overburden removal and sequenced removal of interburden materials, coal loading and hauling, reclamation, general mine equipment application, and facilities use.

(as of January 2010) for PRB coal containing 8,400 Btu/lb were used for the economic analyses of the NWPRB assessment (Platts, 2010).

Mine Model Design
Potential recoverable coal resources in the NWPRB assessment area were determined by evaluating the cost of developing and operating a coal mine that is typical for the region. However, coal mining is not currently being conducted in this area. Past coal mining in the area is generally characterized as small to medium for surface coal mines and shallow and small for underground mines, but there is little historical information that can be used to formulate a mine model. For the present assessment, a mine model was developed to calculate expected mining costs based on the bulk volume and mass excavation of overburden and coal respectively. The necessary excavation rate on a cubic-yards-per-hour basis was calculated to move each coal and interburden horizon in parallel operations to attain an overall annual production rate. Input into the mine model included the stripping ratio, annual coal production rate, and thicknesses of coal beds and interburden horizons. A load-out capacity was calculated for each mining pass or bench. The mine model was then created, using Microsoft EXCEL (2007) spreadsheets, to assess initial capital expenses,

Surface Mine Model Assumptions
Coal loading in the mine model was evaluated for annual production rates ranging from 1 to 12 MST/yr. A nominal production rate of 10 MST/yr was selected from numerous mine model runs as being most representative for mining cases having stripping ratios of 2:1 to 10:1. A lower maximum annual production rate of 8 MST was determined for a 1:1 stripping ratio, owing to the relative thicknesses of the overburden and the coal bed. In the model, coal is mined by excavating pits with lengths of up to one-half mile. Highwalls range in height from 26 ft at a 1:1 stripping ratio to 732 ft for a 10:1 stripping ratio. Bench heights are variable and are dimensioned accordingly with appropriate excavation equipment. Production rates are adjusted to allow a 20- to 30-day period before excavation reaches the end of the strip pit, turns, and reverses direction. Overburden thicknesses differ to a considerable degree, indicating the desirability of flexibility in excavation.

Table 2. Stratigraphic sequence in the regional mining model used for the economic evaluation of the Northern Wyoming Powder River Basin assessment area.
Coal bed Bed 6 Bed 5 Bed 4 Bed 3 Bed 2 Bed 1 Interburden and overburden average thickness and totals (feet) Average overburden thickness Average thickness Average overburden thickness Average thickness Average overburden thickness Average thickness Average overburden thickness Average thickness Average overburden thickness Average thickness Average overburden thickness Average thickness Total coal Total burden Total interburden 26 24 24 26 26 26 16 60 24 40 86 86 51 22 102 21 55 16 60 24 80 68 268 106 15 95 22 105 21 55 16 60 24 98 421 421 Stripping ratio 1:1 2:1 3:1 4:1 5:1 146 11 125 15 95 22 105 21 55 16 60 24 109 586 440 6:1 263 11 125 15 95 22 105 21 55 16 60 24 109 703 440 7:1 380 11 125 15 95 22 105 21 55 16 60 24 109 820 440 8:1 498 11 125 15 95 22 105 21 55 16 60 24 109 938 440 9:1 615 11 125 15 95 22 105 21 55 16 60 24 109 1,055 440 10:1 732 11 125 15 95 22 105 21 55 16 60 24 109 1,172 440

Coal Reserve Evaluation Methodology A suite of equipment systems are considered that include any combination of front-end loader, scraper, or shovel system for initial stripping in single or multiple passes. Push-pull scrapers (22 cubic-yard capacity) with 410 horsepower tracked dozers are used, for reclamation purposes, to excavate and replace top soil in all cases and may also serve for the stripping and hauling of thin overburden horizons. Front-end loaders (8 to 12 cubic-yard capacity) serve for thin overburden and coal loading. Electric shovels (15 and 50 cubic-yard capacity) serve for loading thick single pass and multiple pass (benching) burden and coal loading. Rear-dump haul trucks (40- to 240-ton capacity) serve to haul burden and coal. Drilling is included to drill blast holes, and ammonia nitrate fuel oil explosives are used for overburden and coal breakage. A typical powder factor of 0.85 lb per ton is applied to overburden and 0.5 lb per ton for coal. A discounted cash flow rate of return analysis was performed by determining the capital and operating cost of surface coal mining and calculating the break-even mining cost per short ton of coal. This cost is the point at which the measured tons of coal per stripping ratio may be mined for a specific rate of return or return on investment. An annual rate of eight percent was used in the mine model (T.K. Lee, written commun., 2004). Calculations include initial and replacement capital costs and annual operating costs that incorporate equipment operating expenses, mining administrative and operating personnel, and materials used. The break-even cost per ton is derived from a required annual income to which a corresponding annual coal production rate is applied. A four-step process that includes treatment of capital expense, operating cost, cash flow, and required income was employed in performing an economic analysis upon each mining case from 1:1 to 10:1 stripping ratio.

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office overhead when applicable, and similar expenses. An amount of 8 percent is added as indirect cost. Amortization, salvage, and working capital are excluded in this evaluation. Capital depreciation is determined for the various taxrelated class life designations. A depreciation schedule that is based on Internal Revenue Service guidelines as set forth in Publication 946 (Department of the Treasury, 2008) is developed for equipment with 3-, 5-, 7-, 15-, 20-, and 39-yr class life designations. Depreciation options are available. The convention used herein is to depreciate capital items as quickly as allowable—that is, 3-, 5-, and 7-yr class life capital items use the 200 percent declining balance method, 15- and 20-yr class life capital use the 150 percent declining balance method, and 39-yr class life capital uses the straight line method. Annual depreciation amounts for each of the class life designations are calculated using standard percentages provided in the modified accelerated cost recovery system general depreciation system and totaled for each year of the 20-yr project life (Department of the Treasury, 2008). The amount for each year was discounted to a total present value.

Operating Cost
Operating costs for labor and materials or supplies are calculated as annual expenses. Only explosives are given separately as a consumable supply. The other major supply is electrical power, which is included in equipment operating cost.

Cash Flow
Cash flow in this analysis is the total amount of annual aggregate income and operating expense items for a hypothetical project life. The project cash flow is assumed to be equivalent to total project capital expense for a 20-yr project life.

Capital Cost
The purchase and replacement costs for capital items are determined for each stripping ratio case. As capital costs are mobile-equipment intensive, particular attention has been given to stripping and coal loading activities. Direct capital costs include both initial and replacement capital expense. The total capital investment for equipment and facilities is applied as a single expense to correspond with an initial time (project year 0), which for this evaluation is calendar year 2010. Additional capital investments are made in the 5th, 7th, and 10th year of project life for equipment replacement to account for obsolete and worn-out items. Certain major equipment replacements such as shovels and haul trucks may not coincide with the depreciation schedule. These items will be maintained long after they can be depreciated. Such items in this model are replaced in the 10th project year. Other capital items, which include buildings and support facilities, are not replaced because their useful life exceeds the economic evaluation period of 20 yr. Indirect capital cost is applied as a percentage of the initial capital investment for lease acquisition, engineering, home

Required Income
An assumed single cumulative tax rate, total project depreciation, and total project operating cost are applied to the total project cash flow amount to produce the required income to match overall project costs. The total project production in short ton equivalence is divided into the required income to yield the breakeven cost per ton. The economic analysis was performed on an escalated cost basis to account for the time value of money. Project expenses were escalated to 2010 dollar values. U.S. Department of Labor Bureau of Labor Statistics indices for various commodities were applied as appropriate and projected to provide 2010 dollar values that correspond with a projected midyear or June index. Three time-value-of-money calculations were made: capital cost, capital depreciation, and operating cost. Initial capital investment was made at project year 0 and does not have discounted value. Capital investments made

22

Northern Wyoming Powder River Basin Coal holidays per year were assumed). The development ratio, a ratio of longwall advance rate to development rate, was used to calculate the total continuous miner production needed to maintain longwall production. A ratio of 4.0 was used with a longwall advance rate of 71 ft per day (based on 2 shifts per day for longwall production). Longwall panel development entries were designed for 16-ft wide and 10-ft high sections and the resulting production rate, when multiplied by the development ratio and daily face advance was calculated at 306 tons per shift per continuous miner development section or 919 short tons per day per continuous miner development section. Annual production from the development sections was planned at 992,000 tons. Owing to the importance of mine development, one continuous miner, one roof bolter, two coal haulers, and one scoop tram were written into the model as spares and kept underground for quick access when major repairs were required on development equipment. A recovery rate of approximately 65 percent for the longwall mining model would be expected. Longwall production was based on published production rates (Peng, 2006) and information from the Twenty-Mile and West Elk mines in Colorado, the San Juan mine in New Mexico, and the Bridger mine in Wyoming (Platts, 2009d). Longwall production was scheduled for two 8-hr shifts per day, 7 days per week schedule, and 355 days per year. The third shift was scheduled for maintenance and belt moves 7 days per week, 355 days per year. The advance rate of 6 feet per hour yielded 14, 400 tons per 8-hr shift, and the annual production from the longwall face was 10,388,500 short tons. Total employment was estimated to be 512 employees: 169 production laborers, 256 auxiliary labor employees (including maintenance), 53 mine operations staff employees, and 34 management and technical staff employees. Productivity for similar configurations in the western coal fields range from 7 tons per man-hour to 10 tons per man-hour (Platts, 2009a). This longwall mine model resulted in 10 tons per man-hour productivity. Costs for fuel, lube, repair, maintenance, explosives, miscellaneous, general operations, and electrical power for production equipment were derived from interviews with former U.S. Bureau of Mines and USGS employees and from InfoMine USA, Inc., (2008, 2009) data. General utilities were estimated for the office, shop, and warehouse complex. Ancillary support equipment costs for the auxiliary equipment were estimated to be 2 percent of the auxiliary capitalization and ancillary support for surface support facility capitalization was estimated at 1 percent of the total surface capital. Mine overhead costs were included in the cost models; however, corporate overhead costs were not estimated. Wages, salaries, and benefits rates were taken from data gathered from U.S. Bureau of Mines and USGS employee interviews and from InfoMine USA, Inc. (2008, 2009) adjusted to January 1, 2010. Taxes were developed from data from county and state tax assessors in Wyoming. All nonproduction items required for development of the mine, prior to the first ton of production from the longwall, were amortized. The remainder of the nonproduction equipment, such as feeder breakers, ventilation system and other equipment, was not amortized.

in project year 5, 7, and 10 were discounted at an assumed interest rate to year 0. The aggregate of these investments is the present value of the capital. Operating costs were calculated to be uniform for each of the project years. A total present value operating cost was determined by discounting a uniform series of payments to year 0. Coal losses due to mining inefficiencies preclude recovery of all of the available resources. Coal recovery in the mine model is projected at 90 percent of available resources.

Underground Mine Model Assumptions
Although no coal in the PRB is currently or is anticipated to be recovered by underground mining in the near future, it was felt that for a complete assessment of the NWPRB area this option should be evaluated at least on a preliminary basis. The lack of the extraordinarily thick coal beds, such as in the Gillette coal field, presented a different mining scenario compared with the economics of evaluating relatively thinner coal beds to 10:1 ratio in the NWPRB assessment area. Underground resources having a strip ratio greater than 10:1 are listed in table 3. A longwall mine model was developed to conduct an economic evaluation of the deeper underground potentially mineable coal resources in this area. The primary purposes of the longwall mining model were (1) to determine if underground mining economics might, at some point, compare with surface mining economics and, if so, (2) to estimate the economic tipping point where underground mining might be a more viable alternative to surface mining. A longwall mine model developed in the program CoalVal (Rohrbacher and McIntosh, 2009) used a 13-ft-thick section of coal from each coal bed; however, production rates for purposes of this study were calculated using a 10-ft-high mining height because that is the average used in mining. Conveyor belts were planned to transport the coal from underground dump sites or from the tailgate feeder-breaker to the surface crushing and storage facilities, then to a rail loadout facility. Where coal resources were isolated from the outcrop or from the final highwalls of the surface mining operations, slope entries for the conveyor and ventilation systems and for equipment and manpower access were designed. Vertical shafts were used to assist in mine ventilation and manpower entry where necessary for deep access into the active mine. The model assumed that roof and floor conditions were optimum and did not require any more support than that used in other longwall coal mines located in the Tertiary and Upper Cretaceous coal beds in the Green River, Hanna, and San Juan Basins, and Colorado Plateau areas. The model assumed the purchase of new equipment upon mine startup, normal equipment life, and 8-hr use per operating shift. The discounted cash flow-rate of return was set for 8 percent. Mine development was modeled with a seven-entry system for the main entries and three entries for the longwall panel by using continuous miner development sections. Equipment and manpower for mine development were scheduled for three 8-hr shifts per day, seven days per week, 355 days per year (10

Resources Assessment Results
Table 3. Underground resources in beds at least 10 feet thick in the Northern Wyoming Powder River Basin assessment area.
[Coal beds listed in stratigraphic order. Columns may not sum exactly owing to rounding]

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Resources Assessment Results
A total of 33 individual coal beds were identified and correlated. Of these, 24 coal beds were assessed for in-place coal resources, and 7 of the 24 were included in the economic evaluation for estimating reserve quantities given current market prices.

Coal bed

Depth (feet) 500–1000 1,000–2,000 Subtotal >2,000 Total 500–1000 1,000–2,000

Underground tonnage (million short tons) 6,254 9,308 15,563 109 15,672 831 3,447 4,278 67 4,346 3,540 2,547 6,087 0 6,087 5,610 5,322 10,932 39 10,972 3,334 3,319 6,653 124 6,777 401 6,125 6,526 954 7,481 2,871 4,282 7,153 3,204 10,358 22,844 34,352 57,196 4,499 61,696

Acreage (acres) 236,036 274,965 511,001 4,870 515,871 33,618 131,204 164,822 3,528 168,350 120,272 86,015 206,287 0 206,287 108,745 167,202 275,947 1,797 277,744 122,429 132,399 254,828 5,679 260,507 16,109 215,886 231,995 34,801 266,796 74,702 156,073 230,775 130,002 360,777 711,911 1,163,744 1,875,655 180,677 2,056,332

Resources Evaluation
Original coal resources were calculated for all coal beds at least 2.5 ft thick and with no restrictions taken out. Remaining resources were calculated using the volume of the original resource minus the volume of coal that had been mined. Land use (environmental) and technical restrictions were then calculated and subtracted from the remaining resource to determine available resources. The 24 coal beds evaluated in the NWPRB assessment area contained 285 BST of original coal resources (tables 1, 4, 5). The majority of the available resources, 263 BST (92.3 percent of the total), are on Federal lands (table 4). About 153 MST (0.1 percent) of the total original coal resource) has already been mined, and approximately 21 BST (7.4 percent) is affected by restrictions (too thin, land use, and technical). Subtraction of all the restrictions to mining leaves 263 BST (93.2 percent) of the total original coal resource available for development in this area. Coal resources reported by reliability categories for the original coal resources of the 24 assessed coal beds are summarized in table 1. About 63.5 percent of the total original resources can be classified as “measured” or “indicated,” reflecting an overall substantial improvement in geologic confidence provided by the additional data included in this assessment, compared with the PRB coal resource assessment done by the USGS in 1999 (Ellis and others, 1999).

Roland (Baker, 1929)

Smith

Subtotal >2,000 Total 500–1000 1,000–2,000

Anderson

Subtotal >2,000 Total 500–1000 1,000–2,000

Dietz 3

Subtotal >2,000 Total 500–1000 1,000–2,000

Canyon

Subtotal >2,000 Total 500–1000 1,000–2,000 Subtotal >2,000 Total 500–1000 1,000–2,000

Reserves Evaluation
The first step in the reserves evaluation is a determination of the surface mining costs by ratio, and the underground mining cost. On the basis of those cost analyses, the total recoverable resources are defined. The final step is to calculate the portion of the recoverable tons that can be considered reserves given the current average market price. Once the discounted cash flow costs per ton are determined for all the recoverable resources, the final step in the economic evaluation is determining what portion of those resources can be considered coal reserves (total tons at or below current estimated sales price). To derive a reserve estimate for the NWPRB assessment area coal beds, a composite cost curve was developed for the total recoverable resources by incremental discounted cash flow costs (fig. 97). These costs utilized an 8 percent rate of return. With a February 2010 sales price of $9.30 per ton for the 8,400 Btu/lb coal from the PRB (Platts, 2010), an estimated 1.5 BST of the total 50 BST of recoverable resources are considered as coal reserves (fig. 97). From the cost curve, the relation between sales price and estimated reserves can readily be demonstrated. On January 5, 2009, the sales price per ton for

Lower Canyon

Werner

Subtotal >2,000 Total 500–1000 1,000–2,000

Total

Subtotal >2,000 Total

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Northern Wyoming Powder River Basin Coal interburdens, and six coal beds at a stripping ratio of 5:1 and greater. Increased overburden thicknesses are projected for stripping ratio cases above 5:1. Three key parameters were evaluated as to their effect upon the break-even price per ton for mining coal: production level, stripping ratio, and rate of return. Parametric analysis results indicate that assumed physical constraints limit the annual production rates in the NWPRB assessment area to 8 MST per year for a 1:1 stripping ratio and 10 MST per year at 2:1 to 10:1 stripping ratios. The break-even costs per ton at an 8 percent rate of return and resource volume for 1:1 to 10:1 stripping ratios are shown in table 8. The total NWPRB assessment area recoverable coal resources to a stripping ratio of 5:1 are 7,100 MST of coal (table 9), whereas only 515 MST of coal are present at a stripping ratio of 2:1 or less. Resource volumes for stripping ratios greater than 5:1 are shown in parentheses in table 9 to emphasize that these values are included the recoverable category. Any of the coal resources not economically recoverable by surface mining might be considered available for underground mining The mining costs for the NWPRB assessment area are higher than those for the Gillette coal field (fig. 100), and one reason is that mining costs for the latter are not adversely affected by the joint line railroad (Luppens and others, 2008). However, higher mining costs in the NWPRB area are mainly due to the more complex coal geology and multibed mine models that are inherently more costly than the simpler single-bed model used for the Gillette coal field assessment. Also included are the slightly higher costs for minor equipment, labor, and supplies, and for truck, shovel, and dragline operations.

the 8,400 Btu/lb coal from the PRB was $11.00 per ton (Platts, 2009a). An estimated 2.7 BST would be a reserves equivalent at this price. The $11 per ton price held steady through April 6, 2009, then suddenly dropped to $8.00 per ton in one week (Platts, 2009b, c). By November 23, 2009, the sales price had bottomed out at $7.65 per ton (Platts, 2009d), which would be a reserves equivalent of 0.8 BST at this price. The current sales price as of February 15, 2010, for 8,400 Btu/lb coal from the PRB was $9.30 per ton (Platts, 2010). The changes in the sale price during approximately a 1-yr period corresponded to a swing in reserves estimates from a maximum of 2.7 BST to a low of 0.8 BST (fig. 97). This swing of 1.9 BST emphasizes the value of preparing cost curves. The bar charts in figures 98 and 99 summarize the results of the NWPRB coal resources and reserves assessment by tonnages and percentages for the seven coal beds in the economic evaluation. Two key points from the bar graphs need to be emphasized. First, the 50 BST of recoverable resources, which are only 32 percent of the original resources, owing to mining restrictions, represent the total estimated amount of coal that could be produced by current surface mining technologies. These recoverable resources would be equivalent to the coal resource categories included in the U.S. Energy Information Administration’s estimated recoverable reserves base (Energy Information Agency, 1997). The estimated recoverable reserves base, which is periodically updated by the agency, is currently the only published national summary of potentially minable coal in the United States. The second point that needs to be stressed is that the volume of estimated coal reserves is even a much smaller subset of the original resources (1 percent) than recoverable resources. The relation of original resources to reserves is consistent with previous USGS coal assessments that typically estimated the reserve fraction to be less than 20 percent (Luppens and others, 2009). This finding emphasizes the need to avoid use of the terms resource and reserves interchangeably and why the determination of reserves is not a one time or static process. Typically, as a basin’s resource development matures through time, the resources become progressively more expensive to produce. Sale prices generally increase in the long term and operating costs follow accordingly as long as demand is steady. With continued favorable sales prices productivity and technological advances in mining, resources once considered to be subeconomic may be elevated to the status of reserves. Therefore, reserve studies should be considered a cyclic process; hence, models should be adjusted periodically using the most recent data and minable resources, then reassess them utilizing the most current recovery technology and economics.

Underground Coal Economic Analyses Results
The study of potentially mineable underground coal beds was conducted to determine the cut-off (tipping point) where underground mining is uneconomic. Additionally, a preliminary estimate of the magnitude of underground resources was tabulated. The workable coal bed thickness for longwall systems is about 5 to 13 ft (Thomas, 2002). Deeper in-place resource totals for coal beds with a 10-ft minimum thickness and a stripping ratio greater than 10:1 are listed in table 3; these include the same beds that were evaluated for surface minable deposits. Although longwall shearers are commonly used for seam thicknesses between 5 ft and 20 ft (Myszkowski and Paschedag, 2009), a 10-ft minimum was used as a more conservative estimate of potential underground resources with the most attractive recoverable thicknesses for longwall operations. As with other developed coal basins, it must be emphasized that typically only a fraction of the total underground resources is ultimately recoverable. Factors such as adverse roof and floor conditions, slope of the coal beds, and essential safety barriers between different mining operations typically present notable restrictions to mining. Although recovery in multibed areas is generally most efficient by mining from the

Surface Coal Economic Analyses Results
Mine modeling was performed on stripping ratios from 1:1 to 10:1 (tables 6, 7, 8). Coal beds were added from the initial overburden and one coal bed to an overburden, five

Resources Assessment Results topmost bed downward, that is virtually impossible to control. Additionally, the interburden between the beds must be thick enough to prevent interbed structural influences. None of these factors were evaluated to develop an integrated model of restrictions to underground mining for this assessment. The threshold sales price for the longwall mine model for a 10-ft thick coal bed with production of 11.2 MST per year using

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a discounted cash flow analysis at an 8 percent hurdle rate was $20.00 per ton. This particular rate is important, as it establishes a point where underground recovery may be more attractive economically than surface mining. As seen in table 8, the $20 per ton tipping point falls between the 5:1 and 6:1 stripping ratios. Therefore, for this assessment, recoverable resources are defined as surface minable at a stripping ratio of 5:1 or less.

Table 4. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by subsurface coal ownership categories in millions of short tons. Resource includes coal plus partings. Columns may not sum exactly owing to rounding]

Coal bed

Coal ownership Federal

Original resources ≥ 2.5 ft thick 1,278 551 210

Previously mined 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Land use restrictions 5 0 8 13 3 0 6 9 0 0 0 0 0 0 0 0 1 2 3 6 24 0 13 37 73 12 33 118 1 4 10 15

Technical restrictions 14 3 6 23 71 22 17 110 314 112 102 528 58 2 0 60 536 71 157 764 888 89 134 1,111 303 24 50 377 956 89 194 1,239

Available resources 1,259 548 196 2,003 1,835 618 620 3,073 756 202 459 1,417 1,270 83 2 1,355 2,872 1,057 1,106 5,035 3,290 262 696 4,248 18,350 2,660 3,284 24,294 1,426 124 230 1,780

Percentage of original resource 98.5 99.5 93.3 98.2 96.1 96.6 96.4 96.3 70.7 64.3 81.8 72.9 95.6 97.6 100.0 95.8 84.2 93.5 87.4 86.7 78.3 74.6 82.6 78.7 98.0 98.7 97.5 98.0 59.8 57.1 53.2 58.7

Upper Healy

State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal

2,039 1,909 640 643 3,192 1,070 314 561 1,945 1,328 85 2 1,415 3,409 1,130 1,266 5,805 4,202 351 843

Healy

Ucross

Felix

Lower Felix

State Roland (Upper Rider) Private Total Federal Roland (Baker, 1929) State Private Total Federal Roland (Taff, 1909) State Private Total

5,396 18,726 2,696 3,367 24,789 2,383 217 434 3,034

26

Northern Wyoming Powder River Basin Coal

Table 4. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by subsurface coal ownership categories in millions of short tons. Resource includes coal plus partings. Columns may not sum exactly owing to rounding]

Coal bed

Coal ownership Federal

Original resources ≥ 2.5 ft thick 6,691 1,413 2,125

Previously mined 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9 0 0 0 0 0 0 17 17 0 0 0 0 12 6 96 114 0 3 10 13 0 0 0 0

Land use restrictions 3 1 10 14 149 12 204 365 0 0 0 0 11 0 38 49 13 1 61 75 61 1 267 329 6 0 0 6 34 1 189 224 19 0 109 128 0 0 0 0

Technical restrictions 795 89 244 1,128 827 90 222 1,139 582 44 50 676 138 24 118 280 249 8 9 266 733 77 219 1,029 153 35 101 289 717 86 119 922 1.087 119 199 1,405 483 95 159 737

Available resources 5,893 1,323 1,871 9,087 14,300 1,549 2,437 18,286 1,831 156 79 2,066 232 63 268 563 686 46 94 826 19,867 1,985 3,134 24,986 287 57 187 531 21,286 2,005 3,077 26,368 13,411 1,605 2,387 17,403 3,578 458 422 4,458

Percentage of original resource 88.1 93.6 88.0 88.8 93.6 93.8 84.1 92.4 75.5 78.0 60.2 75.0 60.9 72.4 61.9 62.5 72.4 83.6 57.9 70.9 96.2 96.2 86.2 94.8 64.3 62.0 64.9 64.3 96.5 95.6 88.4 95.4 92.4 92.9 88.2 91.8 88.2 82.7 72.4 85.8

Smith

State Private Total Federal State Private Total Federal

10,229 15,276 1,651 2,863 19,790 2,413 200 129

Anderson

Lower Anderson

State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal State Private Total

2,742 381 87 433 901 948 55 164 1,167 20,661 2,063 3,637 26,361 446 92 288 826 22,049 2,098 3,481 27,628 14,517 1,727 2,705 18,949 4,058 554 583 5,195

Dietz 1

Dietz 2

Dietz 3

Dietz 4

Canyon

Lower Canyon

Ferry

Resources Assessment Results

27

Table 4. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by subsurface coal ownership categories in millions of short tons. Resource includes coal plus partings. Columns may not sum exactly owing to rounding]

Coal bed

Coal ownership Federal

Original resources ≥ 2.5 ft thick 25,600 2,290 2,205

Previously mined 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 12 9 132 153

Land use restrictions 5 0 57 62 0 0 0 0 0 0 0 0 2 2 1 5 0 0 0 0 0 0 0 0 410 36 1,009 1,455

Technical restrictions 492 51 154 697 807 98 320 1,226 1,076 151 353 1,580 819 154 382 1,355 1,347 177 235 1,759 1,311 122 357 1,790 14,756 1,832 3,900 20,488

Available resources 25,102 2,239 1,986 29,326 26,309 2,019 2,421 30,748 19,214 1,938 2,582 23,734 5,353 600 1,549 7,502 6,055 502 519 7,076 14,585 1,139 1,476 17,200 209,047 23,238 31,082 263,376

Percentage of original resource 98.1 97.8 90.1 97.4 97.0 95.4 88.3 96.2 94.7 92.8 88.0 93.8 86.7 79.4 80.2 84.7 81.8 73.9 68.9 80.1 91.8 90.3 80.5 90.6 93.2 92.5 85.0 92.3

Werner

State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal State Private Total Federal State Private Total

30,095 27,116 2,117 2,741 31,974 20,290 2,089 2,935 25,314 6,174 756 1,932 8,862 7,402 679 754 8,835 15,896 1,261 1,833 18,990 224,223 25,116 36,135 285,474

Otter

Gates

Pawnee

Odell

Oedekoven

Total beds

Table 5. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by overburden depth in millions of short tons. Resource includes coal plus partings. Columns may not sum exactly owing to rounding]

Coal bed name

Overburden thickness (feet) 0–500 500–1,000

Original resources ≥ 2.5 ft thick 2,037 2 0 0 2,039

Previously mined 0 0 0 0 0

Land use restrictions 13 0 0 0 13

Technical restrictions 23 0 0 0 23

Available resources 2,001 2 0 0 2,003

Percentage of original resource 98.2 100.0 0 0 98.2

Upper Healy

1,000–2,000 > 2,000 Total

28

Northern Wyoming Powder River Basin Coal

Table 5. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by overburden depth in millions of short tons. Resource includes coal plus partings. Columns may not sum exactly owing to rounding]

Coal bed name

Overburden thickness (feet) 0-500 500-1,000

Original resources ≥ 2.5 ft thick 2,913 279 0 0 3,192 778 1,058 107 2 1,945 1,406 9 0 0 1,415 1,043 3,843 899 20 5,805 2,558 1,667 1,099 72 5,396 6,963 7,639 10,069 118 24,789 1,174 978 882 0 3,034 1,033 2,512 6,506 178 10,229

Previously mined 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Land use restrictions 9 0 0 0 9 0 0 0 0 0 0 0 0 0 0 6 0 0 0 6 23 0 14 0 37 118 0 0 0 118 15 0 0 0 15 14 0 0 0 14

Technical restrictions 107 3 0 0 110 338 178 12 0 528 52 8 0 0 60 389 305 70 0 764 485 402 224 0 1,111 320 30 27 0 377 401 339 499 0 1,239 186 368 574 0 1,128

Available resources 2,885 235 0 0 3,073 440 880 95 2 1,417 1,354 1 0 0 1,355 648 3,538 829 20 5,035 2,050 1,265 861 72 4,248 6,525 7,609 10,042 118 24,294 758 639 383 0 1,780 833 2,144 5,932 178 9,087

Percentage of original resource 99.0 84.2 0 0 96.3 56.6 83.2 88.8 100.0 72.9 96.3 11.1 0 0 95.8 62.1 92.1 92.2 100.0 86.7 80.1 75.9 78.3 100.0 78.7 93.7 99.6 99.7 100.0 98.0 64.6 65.3 43.4 0 58.7 80.6 85.4 91.2 100.0 88.8

Healy

1,000-2,000 > 2,000 Total 0-500 500-1,000

Ucross

1,000-2,000 >2,000 Total 0-500 500-1,000

Felix

1,000-2,000 >2,000 Total 0-500 500-1,000

Lower Felix

1,000-2,000 > 2,000 Total 0-500

Roland (Upper Rider)

500-1,000 1,000-2,000 > 2,000 Total 0-500

Roland (Baker, 1929)

500-1,000 1,000-2,000 > 2,000 Total 0-500 500-1,000 1,000-2,000 >2,000 Total 0-500 500-1,000

Roland (Taff, 1909)

Smith

1,000-2,000 >2,000 Total

Resources Assessment Results

29

Table 5. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by overburden depth in millions of short tons. Resource includes coal plus partings. Columns may not sum exactly owing to rounding]

Coal bed name

Overburden thickness (feet) 0-500 500-1,000

Original resources ≥ 2.5 ft thick 8,742 6,190 4,842 16 19,790 1,242 1,186 314 0 2,742 296 429 176 0 901 285 466 416 0 1,167 7,494 11,128 7,454 285 26,361 131 131 553 11 826 11,272 8,725 6,676 955 27,628 3,580 4,582 9,138 1,649 18,949

Previously mined 0 0 0 0 0 0 0 0 0 0 9 0 0 0 9 0 0 0 0 0 17 0 0 0 17 0 0 0 0 0 114 0 0 114 161 13 0 0 0 13

Land use restrictions 365 0 0 0 365 0 0 0 0 0 49 0 0 0 49 75 0 0 0 75 329 0 0 0 329 6 0 0 0 6 224 0 0 0 224 128 0 0 0 128

Technical restrictions 252 418 469 0 1,139 188 251 237 0 676 64 104 112 0 280 52 133 81 0 266 211 289 451 78 1,029 41 65 182 1 289 137 81 530 174 922 183 415 461 346 1,405

Available resources 8,125 5,772 4,373 16 18,286 1,054 935 77 0 2,066 174 325 64 0 563 158 333 335 0 826 6,937 10,839 7,003 207 24,986 84 66 371 10 531 10,797 8,644 6,146 781 26,368 3,256 4,167 8,677 1,303 17,403

Percentage of original resource 92.9 93.2 90.3 100.0 92.4 84.9 78.8 24.5 0 75.3 58.8 75.8 36.4 0 62.5 55.4 71.5 80.5 0 70.8 92.6 97.4 93.9 72.6 94.8 64.1 50.4 67.1 90.0 64.3 95.8 99.1 92.1 81.8 95.4 90.9 90.9 95.0 79.0 91.8

Anderson

1,000-2,000 >2,000 Total 0-500 500-1,000 1,000–2,000 >2,000 Total 0–500 500–1,000

Lower Anderson

Dietz 1

1,000–2,000 >2,000 Total 0–500 500–1,000

Dietz 2

1,000–2,000 >2,000 Total 0–500 500–1,000

Dietz 3

1,000–2,000 >2,000 Total 0–500 500–1,000

Dietz 4

1,000–2,000 >2,000 Total 0–500 500–1,000

Canyon

1,000–2,000 >2,000 Total 0–500 500–1,000 1,000–2,000 >2,000 Total

Lower Canyon

30

Northern Wyoming Powder River Basin Coal

Table 5. Original coal resources in beds at least 2.5 ft thick in the Northern Wyoming Powder River Basin assessment area.—Continued
[Coal beds listed in stratigraphic order. Reported by overburden depth in millions of short tons. Resource includes coal plus partings. Columns may not sum exactly owing to rounding]

Coal bed name

Overburden thickness (feet) 0–500 500–1,000

Original resources ≥ 2.5 ft thick 8 489 2,431 2,267 5,195 7,184 11,067 7,370 4,474 30,095 3,110 7,653 13,264 7,947 31,974 2,561 6,303 8,617 7,883 25,314 647 2,371 3,764 2,080 8,862 988 2,441 1,408 3,998 8,835 402 1,261 2,722 14,605 18,990 67,847 82,409 88,707 46,510 285,474

Previously mined 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 153 0 0 0 153

Land use restrictions 0 0 0 0 0 62 0 0 0 62 0 0 0 0 0 0 0 0 0 0 5 0 0 0 5 0 0 0 0 0 0 0 0 0 0 1,441 0 14 0 1,455

Technical restrictions 3 66 240 428 737 119 42 331 205 697 94 74 627 431 1,226 116 129 641 694 1,580 45 197 383 730 1,355 41 324 814 580 1,759 99 129 1,144 418 1,790 3,946 4,350 8,109 4,085 20,488

Available resources 5 422 2,191 1,840 4,458 6,995 11,024 7,039 4,269 29,326 3,016 7,579 12,637 7,516 30,748 2,445 6,174 7,976 7,139 23,734 597 2,174 3,381 1,350 7,502 947 2,117 594 3,418 7,076 303 1,132 1,578 14,187 17,200 62,395 78,017 80,584 42,425 263,376

Percentage of original resource 62.5 86.3 90.1 81.2 85.8 97.4 99.6 95.5 95.4 97.4 97.0 99.0 95.3 94.6 96.2 95.5 98.0 92.6 91.1 93.8 92.3 91.7 89.8 64.9 84.7 95.9 86.7 42.2 85.5 80.1 75.4 89.8 58.0 97.1 90.6 92.0 94.7 90.8 91.2 92.3

Ferry

1,000–2,000 >2,000 Total 0–500 500–1,000

Werner

1,000–2,000 >2,000 Total 0–500 500–1,000

Otter

1,000–2,000 >2,000 Total 0–500 500–1,000

Gates

1,000–2,000 >2,000 Total 0–500 500–1,000

Pawnee

1,000–2,000 >2,000 Total 0–500 500–1,000

Odell

1,000–2,000 >2,000 Total 0–500 500–1,000

Oedekoven

1,000–2,000 >2,000 Total 0–500 500–1,000

Total beds

1,000–2,000 >2,000 Total

Resources Assessment Results
Table 6. Original resources of beds at least 5.0 ft thick and less than or equal to a 10:1 strip ratio in the Northern Wyoming Powder River Basin assessment area.
[Coal beds listed in stratigraphic order. Reported by stripping ratio in millions of short tons. Resource includes coal plus partings. Columns may not sum exactly owing to rounding]

31

Stripping ratio <1:1 >1:1–2:1 >2:1–3:1 >3:1–4:1 >4:1–5:1 >5:1–6:1 >6:1–7:1 >7:1–8:1 >8:1–9:1 >9:1–10:1 Total

Coal bed Roland (Baker) 0 3 15 48 91 198 412 588 690 770 2,815 Smith 0 0 0 3 7 18 35 98 134 249 544 Anderson 1 38 148 281 590 822 861 1,091 1,126 1,235 6,193 Dietz 3 2 64 467 1,118 1,550 1,557 1,389 1,499 1,654 1,815 11,115 Canyon 59 235 793 1,576 2,369 2,576 1,990 1,628 1,320 1,163 13,709 Lower Canyon 46 95 243 572 834 865 969 1,052 1,116 1,239 7,031 Werner 62 137 475 1,275 2,448 2,884 2,544 2,242 1,962 1,646 15,675 Total 170 572 2,141 4,873 7,889 8,920 8,200 8,198 8,002 8,117 57,082

Table 7. Resources for beds at least 2.5 thick in the Northern Wyoming Powder River Basin assessment area.
[Coal beds listed in stratigraphic order. Reported by bed for restrictions, recovery rates, mining losses, and recoverable resources, in millions of tons. Columns may not sum exactly owing to rounding]

Coal bed Roland (Baker) Smith Anderson Dietz 3 Canyon Lower Canyon Werner Total

Original resources 24,792 10,229 19,790 26,361 27,628 18,949 30,095 157,844

Restrictions Mined out Land use 118 14 365 329 224 128 62 1,240 Technical 377 1,128 1,139 1,029 922 1,405 697 6,697 >10:1 ratio 21,657 8,334 12,379 14,257 12,985 10,614 13,824 94,050

Available resources (<10:1 ratio) 2,640 753 5,907 10,729 13,383 6,789 15,512 55,713

Recovery rate (percent) 90.0 90.0 90.0 90.0 90.0 90.0 90.0 90.0

Mining losses 264 75 591 1,073 1,338 679 1,551 5,571

Recoverable resources 2,376 678 5,316 9,656 12,045 6,110 13,961 50,142

0 0 0 17 114 13 0 144

32

Northern Wyoming Powder River Basin Coal

Table 8. Life-of-mine costs by mining strip ratio in the Northern Wyoming Powder River Basin assessment area.
[Coal beds listed in stratigraphic order. Costs based on a 20-year project life at an annual production rate of 10 million short tons per year. Costs reported in millions of dollars for the mid-2010 calendar year]

Total costs 1:1 Capital Depreciation Operating Break-even cost per ton 172.6 145.6 786.9 $4.87 2:1 235.4 210.8 1,204.5 $7.26 3:1 304.5 250.1 1,813.8 $10.73 4:1 384.4 328.6 2,405.0 $14.09

Stripping ratio 5:1 441.8 367.0 3,155.0 $18.17 6:1 553.1 464.8 3,645.8 $21.22 7:1 570.7 501.6 4,107.7 $23.57 8:1 656.2 555.0 4,530.6 $26.19 9:1 653.9 577.8 4,966.7 $28.29 10:1 699.4 608.9 5,399.0 $30.72

Table 9. Break-even cost and resource volumes by stripping ratio for the Northern Wyoming Powder River Basin assessment area.
[Reported in millions of tons at an 8 percent rate of return. Columns may not sum exactly owing to rounding]

Resources Available Recoverable Cumulative Break-even cost per ton

Stripping ratio 1:1 170 153 153 $4.87 2:1 572 515 668 $7.26 3:1 2,141 1,927 2,595 $10.73 4:1 4,873 4,386 6,981 $14.09 5:1 7,889 7,100 14,081 $18.17 6:1 8,920 (8,028) (22,109) $21.22 7:1 8,200 (7,380) (29,489) $23.57 8:1 8,198 (7,378) (36,867) $26.19 9:1 8,002 (7,202) (44,069) $28.29 10:1 8,117 (7,305) (51,374) $30.72

Conclusions
The assessment of the NWPRB assessment area adds to the resource and reserve estimates in the PRB. The extensive amount of coalbed methane development in the PRB during the last ten years has provided a wealth of new, publicly available data, especially in this area. Some of the key results of this assessment are as follows: • More than 4,000 drill holes were used to construct a database for resource and reserve calculations. This amount of data greatly improved the geological interpretation, including revision of coal bed correlations and definition of framework channels that controlled the areal extent and thickness of individual beds. • The new geologic coal bed models not only provide a more robust assessment of recoverable coal resources but will also facilitate other resource planning, such as development of coalbed methane resources and evaluation of the environmental impacts of energy-related production. • The methodology for assessing the restrictions to mining was improved as compared with the previous

“cookie cutter” approach to allow for safety setbacks needed to maintain stable highwalls in the mined coal beds rather than simple surface-only expressions around identified buffers. • The preliminary underground mine model provides a reasonable estimate of the economic tipping point where underground mining might be a more viable alternative to surface mining, which, in turn, establishes a limit on recoverable resources by surface mining. The original coal resource in the NWPRB assessment area for all 24 coal beds assessed, with no restrictions applied, was calculated to be 285 BST (table 1). Available coal resources, which are the part of the original coal resource that is accessible for potential mine development after subtracting all restrictions, are about 263 billion short tons (92.3 percent of the original coal resource) (table 1). Recoverable coal, which is the portion of the available coal remaining after subtracting mining and processing losses, was determined for seven coal beds with a stripping ratio of 10:1 or less. The total recoverable coal resource for all seven assessed coal beds is 50 MST (table 7). Coal reserves are the portion of the recoverable coal that can be mined, processed, and marketed at a profit at the time of the economic evaluation. There are a total of 158 BST of

References Cited original coal resources for the seven coal beds assessed for economic resources (table 7). Of these original coal resources, 56 BST (35 percent) of the coal resource is available and 32 percent (50 BST) is recoverable (table 7). Most important, with a discounted cash flow at 8 percent rate of return, only 1.5 BST (1 percent) of the original coal resources in the seven beds can be classified as reserves at the current average estimated sales price of $9.30 per ton (fig. 97). The reserves estimate will change depending on fluctuations in current sales prices (assuming mining costs remained constant).

33

Diamond, W.P., 1982, Site-specific and regional geologic considerations for coalbed gas drainage: U.S. Bureau of Mines Information Circular 8898, 24 p. Eggleston, J.R., Carter, M.D., and Cobb, J.C., 1990, Coal resources available for development—A methodology and pilot study: U.S. Geological Survey Circular 1055, 15 p. Ellis, M.S., Flores, R.M., Ochs, A.M., Stricker, G.D., Gunther, G.L., Rossi, G.S., Bader, L.R., Schuenemeyer, J.H., and Power, H.C., 1999, Chapters PH and PG, in 1999 resource assessment of selected Tertiary coal beds and zones in the Northern Rocky Mountains and Great Plains region: U.S. Geological Survey Professional Paper 1625–A, 2 CD-ROMs. Ellis, M.S., Molnia, C.L., Osmonson, L.M., Ochs, A.M., Rohrbacher, T.J., Mercier, T., and Roberts, N.R., 2002, Evaluation of economically extractable coal resources in the Gillette coal field, Powder River Basin, Wyoming: U.S. Geological Survey Open-File Report 02–180, 48 p. Environmental Systems Research International (ESRI), Incorporated, 2000, ArcView software version 3.2a: Environmental Systems Research International, Incorporated, 380 New York Street, Redlands, Calif. 92373. Environmental Systems Research International (ESRI), Incorporated, 2001, ArcView spatial analyst extension software version 2.0: Environmental Systems Research International, Incorporated, 380 New York Street, Redlands, Calif. 92373. Environmental Systems Research International (ESRI), Incorporated, 2006, ArcGIS software version 9.2: Environmental Systems Research International, Incorporated, 380 New York Street, Redlands, Calif. 92373. Energy Information Agency, 1997, U.S. coal reserves—1997 update: Energy Information Administration, Office of Coal, Nuclear, Electric and Alternate Fuels and Office of Integrated Analysis and Forecasting. U.S. Department of Energy, DOE/EIA-0529(97), 60 p., available at http://tonto.eia.doe.gov/FTPROOT/coal/052997. pdf; accessed June 2009. Flores, R.M., Ochs, A.M., Bader, L.R., Johnson, R.C., and Vogler, D., 1999, Framework geology of the Fort Union coal in the Powder River Basin, chapter PF in 1999 resource assessment of selected Tertiary coal beds and zones in the Northern Rocky Mountains and Great Plains region: U.S. Geological Survey Professional Paper 1625–A, 2 CD-ROMs. Glass, G.B., 1976, Update on the Powder River coal basin, in Wyoming Geological Association Guidebook: Annual Field Conference, 28, Casper, Wyoming, p. 209–220. Glass, G.B., 1977, Wyoming coal and coal mining: Contributions to Geology, University of Wyoming, v. 15, no. 2, p. 79–91.

Acknowledgments
This report was produced as a result of the efforts and cooperation of several people. Nicholas Jones and staff of the Wyoming State Geological Survey supplied drill-hole data and assisted in the correlations within the NWPRB assessment area. Michael Brownfield, Margaret Ellis, Mark Kirschbaum, Dick Keefer, and Tom Judkins, all of the USGS, provided technical reviews of the manuscript.

References Cited
Baker, A.A., 1929, The northward extension of the Sheridan coal field, Big Horn and Rosebud Counties, Montana: U.S. Geological Survey Bulletin 806–B, p. 15–67. Berryhill, H.L., Jr., Brown, D.M., Brown, Andrew, and Taylor, D.A., 1950, Coal resources of Wyoming: U.S. Geological Survey Circular 81, 78 p. Carter, M.D., and Gardner, N.K., 1989, An assessment of coal resources available for development: U.S. Geological Survey Open-File Report 89–362, 52 p. Culbertson, W.C., 1987, Diagrams showing proposed correlation and nomenclature of Eocene and Paleocene coal beds in the Birney 30′ × 60′ quadrangle, Big Horn, Rosebud, and Powder River Counties, Montana: U.S. Geological Survey Coal Investigations Map C–113, scale 1:100,000. Culberston, W.C., Kent, B.H., and Maple, W.J., 1979, Preliminary diagrams showing correlation of coal beds in the Fort Union and Wasatch Formations across the northern Powder River Basin, northeastern Wyoming and southeastern Montana: U.S. Geological Survey Open-File Report 79–1201, 11 p., 2 diagrams (no scale). De Bruin, R.H., Lyman, R.M., Jones, R.W., and Cook, L.W., 2004, Coalbed methane in Wyoming: Wyoming State Geological Survey Information Pamphlet 7, rev. 2, 24 p. Department of the Treasury Internal Revenue Service, 2008, How to depreciate property: Publication 946, catalog no. 13081-F, Washington, D.C., Government Printing Office.

34

Northern Wyoming Powder River Basin Coal Molnia, C.L., Osmonson, L.M., Wilde, E.M., Biewick, L.R.H., Rohrbacher, T.J., and Carter, M.D., 1999, Coal availability and recoverability studies in the Powder River Basin, Wyoming and Montana, in Fort Union Coal Assessment Team, 1999, Resource assessment of selected Tertiary coal beds and zones in the Northern Rocky Mountains and Great Plains region: U.S. Geological Survey Professional Paper 1625–A, 119 p. Molnia, C.L., and Pierce, F.W., 1992, Cross sections showing coal stratigraphy of the northern Wyoming Powder River Basin, Wyoming and Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I–1959–D, scale 1:500,000. Myszkowski, M., and Paschedag, U., 2009, Longwall mining in seams of medium thickness—Comparison of plow and shearer performance under comparable conditions: Milwaukee, Wisc., Bucyrus, 34 p. Accessible at http://www.bucyrus.com/ media/5712/longwall_extraction_of_medium_thickness_coal_ seams.pdf, accessed June 2009. Office of the Federal Register, 2003, Code of Federal Regulations, title 43, part 3460, subpart 3461.5: National Archives and Records Administration, p. 588–593. Accessible at http://www.gpoaccess.gov/cfr/retrieve.html; accessed June 2009. Olive, W.W., 1957, The Spotted Horse coal field, Sheridan and Campbell Counties, Wyoming: U.S. Geological Survey Bulletin 1050, 83 p. Payman,W.S., and Statham, I.C.F., 1930, Mine atmospheres: London, Methuen., 336 p. Peng, S.S., 2006, Longwall mining: Morgantown, W. Va., West Virginia University Department of Mining Engineering, 621 p. Pierce, B.S., and Dennen, K.O., eds., 2009, The National Coal Resource Assessment overview: U.S. Geological Survey Professional Paper 1625–F, 402 p. Platts, 2009a, Coal Outlook: New York, Platts, a division of The McGraw-Hill Companies, v. 33, no. 01, January 05, 2009, 10 p. Platts, 2009b, Coal Outlook: Platts, a division of The McGraw-Hill Companies, New York, NY, v. 33, no. 14, April 06, 2009, 14 p. Platts, 2009c, Coal Outlook: Platts, a division of The McGraw-Hill Companies, New York, NY, v. 33, no. 15, April 13, 2009, 12 p. Platts, 2009d, Coal outlook: New York, Platts, a division of The McGraw-Hill Companies, v. 33, no. 47, November 23, 2009, 16 p. Platts, 2010, Coal outlook: New York, Platts, a division of The McGraw-Hill Companies, v. 34, no. 02, January 11, 2010, 12 p.

Glass, G.B., 1978, Coal, in Porter, F.H., and Grasso, D.N., Sheridan County, Wyoming: The Geological Survey of Wyoming County Resource Series 5, 9 plates. Glass, G.B., 1980, Coal resources of the Powder River Coal Basin, in Guidebook to the coal geology of the Powder River coal basin, Wyoming, field trip 5: American Association of Petroleum Geologists Energy Minerals Division, June 12−14, 1980, p. 91−124. Golden Software, Inc., 2002, Surfer8 software: Golden Software, Inc., 809 14th Street, Golden, Colo., 80401–1866. GRG Corporation, 1998, StratiFact software version 4.57: GRG Corporation, 4175 Harlan Street, Wheat Ridge, Colo., 80033–5150. InfoMine USA, Inc., 2008, Mine and mill equipment costs— An estimator’s guide 2008: InfoMine USA, Inc., 1120 N. Mullan Rd., Suite 100, Spokane Valley, Wash. 99206, 412 p. InfoMine USA, Inc., 2009, Mining cost service: InfoMine USA, Inc., 1120 N. Mullan Road, Suite 100, Spokane Valley, Wash. 99206, 154 p. Kent, B.H., Berlage, L.J., and Boucher, E.M., 1980, Stratigraphic framework of coal beds underlying the western part of the Recluse 1×½-degree quadrangle, Campbell County, Wyoming: U.S. Geological Survey Coal Investigations Map C–81C, 2 plates, scale 1:100,000. Mining Media, Inc., Peter Johnson, ed., 2005, Keystone Coal Industry manual: Jacksonville, Fla., 553 p. Law, B.E., Barnum, B.E., and Wollenzien, T.P., 1979, Coal bed correlations in the Tongue River Member of the Fort Union Formation, Monarch, Wyoming, and Decker, Montana, areas: U.S. Geological Survey Miscellaneous Investigations Series Map I–1128, no scale. Luppens, J.A., Rohrbacher, T.J., Osmonson, L.M., and Carter, M.D., 2009, Coal resource availability, recoverability, and economic evaluations in the United States—A summary, in Pierce, B.S., and Dennen, K.O., eds., The National Coal Resource Assessment overview: U.S. Geological Survey Professional Paper 1625–F, chapter D, 17 p. Luppens, J.A., Scott, D.C., Haacke, J.E., Osmonson, L.M., Rohrbacher, T.J., and Ellis, M.S., 2008, Assessment of coal geology, resources, and reserves in the Gillette coal field, Powder River Basin, Wyoming: U.S. Geological Survey Open-File Report 2008–1202, 127 p. Mentor Consultants, 2005, PC/Cores, Post Office Box 3147, Glen Ellyn, Ill. 60137. Microsoft, 2007, Excel spreadsheet software, version Office 2007: Microsoft Corporation, 1 Microsoft Way, Redman, Wash. 98052.

Glossary Public Law 95–87, 1977 Surface Mining Control and Reclamation Act of 1977, (30 U.S.C. 1201 et seq.), 115 p. Accessible at http://www.osmre.gov/smcra.htm; accessed June 2009. Public Law 101–549, 1990, Clean Air Act (42 U.S. C. 7651d) 9 p. Accessible at http://www.epa.gov/air/caa/caa.text; accessed June 2009. Rice, C.A., Ellis, M.S., and Bullock, J.H., Jr., 2000, Water co-produced with coalbed methane in the Powder River Basin, Wyoming—Preliminary compositional data: U.S. Geological Survey Open-File Report 00–372, 20 p. Rohrbacher, T.J., and McIntosh, G.E., 2010, CoalVal–A coal resource valuation program: U.S. Geological Survey Open-File Report 2009–1282, 265 p. Stricker, G.D., Flores, R.M., Trippi, M.H., Ellis, M.S., Olson, C.M., Sullivan, J.E., and Takahashi, K.I., 2007, Coal quality and major, minor, and trace elements in the Powder River, Green River, and Williston Basins, Wyoming and North Dakota: U.S. Geological Survey Open-File Report 2007– 1116, 31 p. Taff, J.A., 1909, The Sheridan coal field, Wyoming, in Coal and lignite, pt 2: U.S. Geological Survey Bulletin 341, p. 123–150. Thomas, Larry, Dargo Associates Ltd., 2002, Coal geology: West Sussex, England, John Wiley, 365 p. U.S. Bureau of Land Management, 2001, Buffalo resource management plan, Appendix D—Coal screening process. Accessible at http://www.blm.gov/rmp/WY; accessed June 2009. U.S. Bureau of Land Management, 2003a, Final environmental impact statement for the Pittsburg and Midway Coal Mining Company Coal Exchange Proposal (WYW148816), Casper, Wyoming, Field Office, 187 p. U.S. Bureau of Land Management, 2003b, Final environmental impact statement and proposed plan amendment for the Powder River Basin Oil and Gas Project (WY-070-02-065), Buffalo, Wyoming, Field Office, 397 p. 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. Wyoming Oil and Gas Conservation Commission, 2009, On-line database accessible at http://wogcc.state.wy.us; accessed June 2009. Wyoming Spatial Data Clearinghouse, 2009, On-line database accessible at http://wgiac2.state.wy.us; accessed June 2009.

35

Glossary
The present study includes determinations of original, available, recoverable, and economically recoverable (reserves) resources. This terminology has been used in many USGS coal studies (see Wood and others, 1983; Carter and Gardner, 1989; Eggleston and others, 1990; and Molnia and others, 1999). The following definitions were applied in this resource evaluation: • Available coal resource is the amount of the original resource that is accessible for mine development under current regulatory and land-use constraints. This resource is the original coal minus previously mined coal and coal that cannot be mined owing to land use and technical restrictions. • Coal reserves are virgin or accessed parts of a coal reserve base which could be economically extracted or produced at the time of determination considering environmental, legal, and technologic constraints. The term reserves need not signify that extraction facilities are in place or operative. Reserves include only recoverable coal; thus, terms such as “extractable reserves” are redundant and are not a part of the classification system. Reserves can be categorized as “measured” and “indicated,” as underground or surface minable, by thickness of overburden, by thickness of coal in the bed, and by various quality factors (Wood and others, 1983). • Coal resources are a naturally occurring concentrations or deposits of coal in the Earth’s crust, in such forms and amounts that economic extraction is currently or potentially feasible (Wood and others, 1983). • Discounted cash flow is the stream of the net after-tax cash flows where the cash outlays include all operating costs, taxes, and investment costs, and where revenues include cash payments of product sales. • Fault is a planar fracture in rock in which the rock on one side of the fracture has moved with respect to the rock on the other side. • Hypothetical resources are a class of undiscovered resources that are either similar to known coal deposits which may be reasonably expected to exist in the same coal field or region under analogous geologic conditions or are an extension from inferred resources (Wood and others, 1983). • Hurdle rate is the rate of return required for the mining company to mine the coal resource at a profit. • Identified resources are resources whose locations, rank, quality, and quantity are known or estimated from specific geologic evidence. Identified coal resources include economic, marginally economic, and subeconomic components. To reflect varying distances from points of control or reliability, these subdivisions can be divided into demonstrated and inferred, or preferably into measured, indicated, and inferred (Wood and others, 1983). • Interburden is noncoaly material that lies between two coal beds.

36

Northern Wyoming Powder River Basin Coal • Land use restrictions are constraints placed upon mining by societal policies to protect those surface features or entities that could be harmed by mining. Since laws and regulations can be modified or repealed, the restrictions, including industrial and environmental restrictions, may change. Land use restrictions include railroads, cities and towns, airports, and interstate highways. Technical restrictions are constraints, relating to economics and safety, placed upon mining by the state of technology or prescribed by law. These restrictions can change with advances in science and technology, or modifications in the law. In this report, geologic factors are included as technologic restrictions. Technical restrictions include coal between 2.5 ft and 5.0 ft thick and clinker areas. Unsuitability criteria are constraints used to determine if an area can be mined by surface mining methods. These include, but are not limited to, Federal land systems, dwellings, and alluvial valley floors.

• Original coal resource is the total amount of coal in-place before production. Where mining has occurred, the total of original resources is the sum of the identified resources, undiscovered resources, coal produced, and coal lost in mining (Wood and others, 1983). • Overburden is rock including coal or unconsolidated material that overlies a specified coal bed. Overburden is reported in feet or meters and used to classify the depth to an underlying coal bed (Wood and others, 1983). • Paleochannel is a remnant of a stream channel cut in older rock and filled by the sediments of adjacent exposed rock. • Parting is a thin layer of stratum or noncoaly material within a coal bed which does not exceed the thickness of coal in either the directly underlying or overlying benches (Wood and others, 1983). • Previously mined coal is coal that has already been extracted. • Recoverable coal resource is coal that is or can be extracted from a coal bed during mining. The term “recoverable” should be used in combination with “resources” and not with “reserves” (Wood and others, 1983). • Reliability categories are based on the distance from points of measurement or sampling. The measured, indicated, inferred, and hypothetical resource categories, as defined, indicate the relative reliability of tonnage estimates as related to distance from points of thickness control of particular parts of a coal deposit. The reliability categories are not indicative of the reliability of the basic data (that is, the accuracy of coal measurements, or the accuracy of location of the coal outcrop. It is assumed that all basic data used in resource estimation have been judged reliable by the estimator and that unreliable data have been discarded (Wood and others, 1983). • Measured—Tonnage estimates computed by extrapolation of thicknesses of coal for a radius of 0.25 mi (0.4 km) from a point of measurement. • Indicated—Tonnage estimates computed by extrapolation of thicknesses of coal for a radius of 0.25 to 0.75 mi (0.4 to 1.2 kilometers (km)) from a point of measurement. • Inferred—Tonnage estimates computed by extrapolation of thicknesses of coal for a radius of 0.75 to 3.0 mi (1.2 to 4.8 km) from a point of measurement. • Hypothetical—Tonnage estimates computed by extrapolation of thicknesses of coal for a radius beyond 3.0 mi (4.8 km) from a point of measurement. • • Remaining resources are the original resource minus the volume of coal that had been previously mined. Restrictions to mining include land use, technical limitations, and unsuitability that would prohibit mining: • •

•

•

Surface (strip) mining is the practice of mining a seam of mineral by first removing a long strip of overlying soil and rock. Surface mining is practical only when the ore body to be excavated is relatively near the surface. When coal seams are near the surface, it may be economical to extract the coal using open cut (also referred to as open cast, open pit, or strip) mining methods. Open cast coal mining recovers a greater proportion of the coal deposit than underground methods, as more of the coal seams may be recovered. Stripping (mining) ratio is the most influential economic factor in the evaluation and planning of open pit coal mines. It represents the ratio of the volume of overburden or interburden (waste) that must be removed to gain access to a unit amount of coal. For this assessment, the ratio is expressed as cubic yards of overburden to tons of coal. The stripping ratio can be approximated by dividing the total thickness of waste by the total thickness of coal. For example, given two coal beds each 5.0 ft thick at 50 and 105 ft in depth, the total waste and coal thicknesses would be 100 and 10 ft respectively. A simple ratio would be 10:1, but a stripping ratio would be 9.1:1 (in cubic yards to a ton of coal). Threshold sales price is the minimum free-on-board (FOB) sales price required to recover all mine and beneficiation operating costs and investment expenditures, and to meet a specified after-tax rate of return to investment. Tipping point is the point at which the cost of surface mining exceeds the cost of underground mining. Undiscovered resources are coal resources, the existence of which are only postulated or which comprise deposits that are either separate from or are extensions of identified resources. Undiscovered resources may be postulated in deposits of such quality, rank, quantity, and physical location as to render them economic or subeconomic (Wood and others, 1983).

•

• •

Figures

Figures
108 o 00’ 106 o 00’ 104 o 00’

37

Miles City

Treasu re Musselshell
46 o 00’

Fallon Custer

94 90
Big Horn

Roseb ud Carter
Birney EXPLANATION
Powder River Basin Northern Wyoming Powder River Basin assessment area

Powder River

Decker
45 00’
o

MONTANA
Sherid an

Gillette coal field boundary County line Railroad

Sheridan

Campbell

WYOMING
Cook

90

INDEX MAP

Buffalo

Big Horn
44 o 00’

Moorcroft
Gillette
Powder River Basin

Montana

Washa kie

Wyoming

Weston
Hot Springs Freemo nt

Johnson
Natron a

0
43 o 00’

20 20 40

40 MILES 60 KILOMETERS

Converse

0

25

Niobrara
Glenrock Douglas

Platte
Figure 1. Northern Wyoming Powder River Basin assessment area and Gillette coal field, Powder River Basin, Wyoming and Montana (modified from Flores and others, 1999).

Figure 1. Map showing location of the Northern Wyoming Powder River Basin assessment area and Gillette coal field, Powder River Basin, Wyoming.

107 o 00’

106 o 00’

105 o 00’

38
EXPLANATION
Northern Wyoming Powder River Basin assessment area County Line Town of Sheridan

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County 45 00’
o

Powder River County

MONTANA WYOMING Spotted Horse coal field Sheridan coal field Little Powder River coal field Powder River coal field

T. 9 S. T. 58 N. T. 57 N.

Mine area (abandoned)
INDEX MAP

T. 56 N.

T. 55 N.

WYOMING

90
Sheridan County Johnson County

T. 55 N.

Sheridan County

T. 53 N.

Johnson County 44 30’ Big Horn County
o

Campbell County

Buffalo coal field Gillette coal field Barber coal field

T. 52 N.

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 2. Map showing the Northerncoal fieldsPowderNorthern Wyoming Powder River Basin assessment area. (Modified from Glass, 1976). location of Wyoming in the River Basin assessment area (modified from Glass, 1976). Figure 2. Coal fields in

45°00'
Tft

107 °15'
T Tftr

107 °00'
Qal Tftr

Montana Wyoming

106 °45'
Explanation Qal Tw Tftr
Quaternary alluvium Tertiary Wasatch Formation Tertiary Tongue River Member of the Fort Union Formation Tertiary Lebo Shale Member of the Fort Union Formation Tertiary Tullock Member of the Fort Union Formation Undifferentiated Fort Union Formation

Tw

Acme mine area

Big Horn Mine
Qal

T Tft

T Tft Tftr

Tw Tfu

Tfu

Sheridan

Underground mines (abandoned) Acme mine area Big Horn surface mine (abandoned) Fault

44°45'
Tfu

Railroad Road
INDEX MAP

Tft

Qal Tw Tft
Sheridan Coal Field Powder River Basin

Montana

Wyoming

0 0 5

5

10 MILES 10 KILOMETERS

Figures

Figure 3. Geology of the Sheridan coal field showing abandoned mines and faults (modified from Ellis and others, 1999).

39

Figure 3. Geologic map of the Sheridan Coal Field showing abandoned mines and faults. (Modi ed from Ellis and others, 1999).

40

R. 36 E.

R. 37 E.

R. 38 E.

R. 39 E.

R. 40 E.

R. 41 E. T. 9 S.

Northern Wyoming Powder River Basin Coal

3

2
17 16

MONTANA
18

1

32

33

34

A’ B’

WYOMING
EXPLANATION

19

U D

20

21

22

23

24

T. 58 N.

PSO lease area—Proposed

U D U D
29 28 27 26 25
T. 57 N.

U D

Approximate location of fault showing upthrown and downthrown sides

INDEX MAP

Montana
Proposed Mine Area Powder River Basin

A
30

Wyoming

31

32

B

33

34

35

36

T. 56 N.

R. 88W.
0 0

R. 87W.
1 1 2

R. 86W.
2

R. 85 W.

R. 84 W.

R. 83 W.

MILES

KILOMETERS

Figure 4. Location map of the PSO lease area showing approximate location of faults. Pittsburg and Midway Coal Mining Company estimated Figure 4. contain 107 lease of recoverable coal (U.S. Bureau of Land Management, Coal Mining Company estimated this and B-B’ faults is the this area toProposed PSO MST area showing approximate location of faults. Pittsburg and Midway2003a). The area between A-A’ area to contain 107 million short tons of recoverable mining Bureau approximate coal (U.S.limit. of Land Management, 2003a). The area between A-A’ and B-B’ faults is the approximate mining limit.

Formation Kent and Name others, 1980

Pierce and Fort Union Coal Molnia and others others, 1990 Assessment Team, 1997, 1999, and 1999, and Glass Osmonson, 2000 1999

Ellis and others, 2002

Luppens and others, 2008

This report Resources calculated on these beds Upper Healy Healy Ucross Felix Lower Felix Roland (Upper Rider) Roland of Baker,1929 Roland of Taff, 1909 Smith Anderson Lower Anderson Dietz 1, Dietz 2, Dietz 3, Dietz 4 Canyon Lower Canyon Ferry Werner Otter

Wasatch Felix Roland/ Badger Wyodak Rider Wyodak Rider Upper Felix Felix Roland Roland Smith Anderson Rider, Anderson Dietz Canyon

Smith

Wyodak-Anderson Wyodak or coal zone=Smith Upper Wyodak (Swartz), Badger, Fort Union (Anderson/ School, Sussex, Big (Tongue Canyon Canyon George, Wyodak, River Anderson, Dietz, Member) Canyon (Monarch), Werner Lower Werner Wyodak Gates/ Kennedy Upper Kennedy

Upper Wyodak

Main Wyodak

Upper Wyodak

Canyon Lower Wyodak Lower Wyodak

Werner

Wall

Gates/ Kennedy

Gates Pawnee

Gates Pawnee Odell Roberts

Figures

Figure 5 Coal bed and and zone names used in various in di erentabout the Powder River Basin. River Basin. Figure 5. . Coal bed coal coal zone names used publications publications in the Powder

41

42

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

EXPLANATION
Drill Hole Location Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 56 N.

T. 55 N.

Mine area (abandoned)
INDEX MAP

T. 55 N.
Sheridan County Johnson County

T. 53 N.

WYOMING

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 6. Drill holes in the Northern Wyoming Powder River Basin assessment area.

Figure 6. Map showing location of drill holes in the Northern Wyoming Powder River Basin assessment area.

PHASE 1--DATA COLLECTION AND EDITING
Coal bed geology (extent, thickness, partings, structure, overburden) Factors affecting extraction (land-use and technical restrictions) Location of preparation processing plants, roads, and rail facilities State and county jurisdictions and resource ownership

Coal bed correlations and editing

Coal quality information Recent coal sales price(s) Tax information

PHASE 2--MODELING
Create digital models for all assessed coal beds Create GIS models of restrictions to mining Calculate tonnages and areas for original, mined out, restricted, and available resources

PHASE 3--RESERVE ANALYSIS
Calculate available resources by mine model, all costs, and data Calculate mining costs, production rates, and tax rates Calculate recoverable tons for incremental cash costs and discounted cash cost/rate of return, cost curves, and reserves
Figures

Figure 7. Generalized methodology used for coal resource and reserve evaluation.

43

Figure 7. Flow chart showing generalized methodology used for coal resource and reserve evaluation.

44

Northern Wyoming Powder River Basin Coal
108 o 00’ 106 o 00’ 104 o 00’

Miles City
Treasu re Musselshell
46 00’
o

Fallon Custer

EXPLANATION

Qal Twr Tw Tftr Tftl Tft Tfu

Quaternary alluvium

Rosebu d

Tfu
Carter

Tertiary White River Formation

Tertiary Wasatch Formation

Powder River

Birney
Big Horn
45 o 00’

Tertiary Tongue River Member of the Fort Union Formation Tertiary Tongue River and Lebo Shale Members of the Fort Union Formation (undifferentiated) Tertiary Tullock Member of the Fort Union Formation

Decker
Tw

MONTANA WYOMING
Sherid an

Sheridan

Tftr Tft
Cook

Fort Union Formation (undifferentiated) Basin axis

Big Horn Washa kie

Buffalo

Moorcroft

Gillette

Northern Wyoming Powder River Basin assessment area Gillette coal field boundary County line Approximate location of faults

44 o 00’

Twr
Hot Spring s Freemo nt

Weston

Johnson
Natron a

Campbell

INDEX MAP

0
43 o 00’

20 20 40

40 MILES 60 KILOMETERS

Qal

Converse
Tw

Tftl Tft
Niobrara
Powder River Basin

Montana

Wyoming

0

Glenrock Douglas
Platte

Figure 8. Generalized geology of the Powder River Basin, Wyoming and Montana (modified from Flores and others, 1999).

Figure 8. Generalized geologic map of the Powder River Basin assessment area, Wyoming and Montana. (Modi ed from Flores and others, 1999).

Figures

45

AGE
QUATERNARY

STRATIGRAPHIC UNITS IN THE POWDER RIVER BASIN WYOMING MONTANA

TERTIARY

PLIOCENEOLIGOCENE EOCENE PALEOCENE

White River Formation surficial deposits Wasatch Formation Fort Union Formation Lance Formation Bearpaw Shale Mesaverde Formation Tongue River Member Lebo Member Tullock Member Hell Creek Formation

Fox Hills Sandstone

CRETACEOUS

LATE CRETACEOUS

Pierre Shale

Cody Shale Niobrara Formation Carlile Shale Frontier Formation Greenhorn Formation Belle Fourche Formation

Mowry Shale EARLY CRETACEOUS Muddy Sandstone Thermopolis Shale Fall River Formation Lakota Formation

Figure 9.Montana (modified from Ellis and others, 2002). Powder River Basin Wyoming and Montana. Generalized stratigraphic column for the (Modi ed from Ellis and others, 2002).

Figure 9. Generalized stratigraphic column of Powder River Basin stratigraphy, Wyoming and

46

Northern Wyoming Powder River Basin Coal

Coal Stratigraphy
Coal Bed Names/ Coal Bed Names/ Resources Reserves Maximum Average calculated calculated thickness (ft) thickness (ft)
Upper Healy Healy Ucross 57.3 45.9 39.5 16.4 16.6 6.7

Formation Coal Bed Names
Upper Healy Healy Ucross Wasatch Felix Upper Rider Felix Lower Rider Felix Lower Felix Roland (Upper Rider) Roland (Lower Rider) Roland (Baker) Roland (Taff) Upper Smith Smith Anderson (Upper Rider) Anderon (Lower Rider) Anderson Lower Anderson Fort Union Dietz 1 Dietz 2 Dietz 3 Dietz 4 Cox Canyon Lower Canyon Upper Ferry Ferry Werner Upper Otter Otter Gates Pawnee Odell Roberts

Felix Lower Felix Roland (Upper Rider) Roland (Baker) Roland (Taff) Smith Roland (Baker)

27.9 52.1 19.8 34.5 25.6 33.8

13.1 9.8 6.3 13.9 5.1 8.3

Smith

Anderson Lower Anderson Dietz 1 Dietz 2 Dietz 3 Dietz 4 Canyon Lower Canyon Ferry Werner Otter Gates Pawnee Odell Roberts

Anderson

Dietz 3

46.5 43.8 28.2 28.3 70.0 19.9 80.0 53.8 25.4 63.5 63.2 45.4 27.6 25.5 37.9

11.3 6.6 6.0 6.7 16.2 5.3 13.3 10.9 7.1 16.2 14.6 10.5 6.9 7.2 10.9

Canyon Lower Canyon

Werner

Figure Coal stratigraphy in the Northern Powder River Basin assessment area showing names used in this report. Figure 10. 10. Coal stratigraphy in the Northern Wyoming Powder River Basin assessment area, showing names used in this report.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County
45 00’
o

Powder River County

T. 9 S.

B A C

MONTANA

B’ C’

WYOMING

T. 58 N. T. 57 N.

EXPLANATION
Cross sections

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

T. 55 N.

INDEX MAP

Campbell County Sheridan County Johnson County

T. 55 N.
WYOMING

T. 53 N.

A’
44 30’ Big Horn County
o

T. 52 N.

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W. R. 75 W.
20 MILES

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 KILOMETERS

Figure 11. Map showing location of cross sections A-A’, B-B’, and C-C’ shown in gures 12-14.

Figure 11. Lines of cross sections A-A’, B-B’, C-C’ (see figures 12–14).

Figures 47

48

A
CDC 8026 3321966 3323998

NW
3321054
3800 3700 3600 3500 3400 3300 3200 3100 3000
ELEVATION IN FEET

26.1 MILES (42.1 KILOMETERS)
3325531 3305030 3320111 3320056 3320230 3326419 3324777 3305016

A’
Northern Wyoming Powder River Basin Coal
SE
3320133
3800 3700 3600 3500 3400

Smith Anderson Dietz 2 Dietz 3 Canyon

Roland (Taff, 1909) Roland (Taff, 1909)

3320099

3300 3200 3100

2900 2800 2700 2600 2500 2400 2300 2200 2100 2000 1900 1800 1700 FAULT WITH 170 FEET OF DISPLACEMENT

Dietz 2 Werner

2900 2800 2700

Smith

Canyon

Dietz 4

Anderson Dietz 3 Canyon

2600 2500 2400 2300 2200 2100

EXPLANATION No record Undifferentiated rock Coal

FAULT WITH 180 FEET OF DISPLACEMENT

Werner

2000 1900 1800 1700

of 12. Cross section A-A’ gure 11. (CDC indicates in the Conservation Division Corehole). Figurethis section shown in showing faults and coal beds USGS Sheridan coal field. Numbers above drill core indicate API numbers. Location of this section shown in figure 11. CDC, USGS Conservation Division core hole.

Figure 12. Cross section A-A’ showing faults and coal beds in the Sheridan Coal Field. Numbers above drill holes indicate API numbers. Location

ELEVATION IN FEET

Roland (Baker, 1929)

3000

B
W
3321495 3321273 3800 3321969

5.8 MILES (9.3 KILOMETERS)
3320258

B’
E
3800

3321407

3321968

3321966

3321790

3321287

3321417

3700

3700

3321298

3320261

3321188

3321201

3321226

3321221

3321315

Dietz 3
3500

3321185

Anderson

3321236

3321200

3600

3600

3500

3400

Canyon

Smith Anderson Werner Dietz 2

3400

ELEVATION IN FEET

3200

3200

3100

Dietz 2 and Dietz 3 merge

Dietz 3 Canyon

3100

3000

3000

2900
EXPLANATION

2900

2800

No record Undifferentiated rock Coal

FAULT WITH 430 FEET OF DISPLACEMENT

Werner
FAULT WITH 130 FEET OF DISPLACEMENT

2800

2700

2700

ELEVATION IN FEET

3300

3300

Figures

2600

2600

Figure 13.Coal Field. Numbers above drill fault with 430 ft of API numbers. The location of this coal bed in the Sheridan coal field. Numbers above drill holes indicate Cross section B-B’ showing a major holes indicate displacement and splitting of the Dietz 3 section is shown in gure 11. API numbers. The location of this section is shown in figure 11.

Figure 13. Cross section B-B’, showing major fault with 430 ft of displacement and splitting of the Dietz 3 coal bed in the Sheridan

49

50

C
3320402

3325120

3322514

3320409

3322205

3323056

3325282

3324831

3324825

3320610

3600

3321291

3322954

3322794

3700

Roland (Baker, 1929)

3322955

33222512

3322312

3800

3322756

3324942

3324382

N

14.0 MILES (22.4 KILOMETERS)

C’
S

Northern Wyoming Powder River Basin Coal

3800

3700

3321283

3600

3500

Smith Roland (Taff, 1909)

Felix Roland (Baker, 1929)

3500

3400

3400

Anderson
3300

Roland (Taff, 1909) Dietz 2 Dietz 3 Canyon

3300

ELEVATION IN FEET

Smith
3100

3100

3000

3000

2900

Anderson Werner Dietz 1 Dietz 2
EXPLANATION No record Undifferentiated rock Coal

2900

2800

2800

2700

2700

2600

FAULT WITH 150 FEET OF DISPLACEMENT FAULT WITH 140 FEET OF DISPLACEMENT

2500

Dietz 3 Dietz 4 Canyon Werner

2600

2500

2400

2400

Figure 14. The location of this section is shown on gure 11. Cross section C-C’ showing faults and coal beds in the Sheridan coal field. Numbers above drill holes indicate API numbers. The location of this section is shown in figure 11.

Figure 14. Cross section C-C’, showing faults and coal beds in the Sheridan Coal Field. Numbers above drill holes indicate API numbers.

ELEVATION IN FEET

3200

3200

D

D’

Vertical scale 2,000 ft Upper Healy 1,500 ft Healy Ucross 1,000 ft Anderson 500 ft Roland (Baker) Smith Dietz 3 Canyon Lower Canyon Felix

Approximate land surface

0 ft

Ferry Werner Otter Gates Pawnee Roberts Odell

D
0 0 5 5 10 10 20 20 MILES

D’
Location map

KILOMETERS

Figures 51

Figure 15. Cross section the Northern Wyoming Powder River Basin assessment River Basin assessment area showing subsurface distribution of Figure 15. Cross section D-D’ through D-D’ through the Northern Wyoming Powder area showing subsurface distribution of coal beds. Vertical exaggeration coal ×5,000. approximately beds. (Vertical exaggeration approximately 5,000 X).

E

E’

52 Northern Wyoming Powder River Basin Coal

Vertical scale 2,000 ft Approximate land surface Healy

1,500 ft

1,000 ft

Roland (Baker) Smith

Anderson

Ferry 500 ft Dietz 3 Canyon 0 ft Otter Lower Canyon Werner

Gates Odell Pawnee

E’ E

Roberts

0 0 5

5 10

10 20

20

MILES

Location map

KILOMETERS

Figure section E-E’ through E-E’ through the Northern Wyoming Powder River Basin assessment area showing subsurface distribution of Figure 16. Cross16. Cross sectionthe Northern Wyoming Powder River Basin assessment area showing subsurface distribution of coal beds. Vertical exaggeration coal beds. approximately ×5,000. (Vertical exaggeration approximately 5,000 X).

F

F’

Vertical scale 2,000 ft Healy 1,500 ft Ucross Upper Healy Approximate land surface

1,000 ft

500 ft

Roland (Baker) Smith Anderson

0 ft Canyon Lower Canyon Werner Gates Pawnee

Dietz 3

Ferry Otter Odell

F’
Roberts
0 0 5 5 10 10 20 20 MILES

F
Location map

KILOMETERS

Figures 53

Figure 17.Figure 17. Crossthrough the Northern WyomingNorthern Wyoming Powder River Basin assessment area showing subsurface distribution of Cross section F-F’ section F-F’ through the Powder River Basin assessment area showing subsurface distribution of coal beds. Vertical exaggeration coal×5,000. (Vertical exaggeration approximately 5,000 X). approximately beds.

G

G’

54 Northern Wyoming Powder River Basin Coal

Vertical scale 2,000 ft Healy Ucross 1,500 ft Approximate land surface Felix

1,000 ft

Roland (Baker) Smith

500 ft

Anderson Dietz 3 Ferry

Canyon

Werner

0 ft

Lower Canyon Otter Gates Pawnee Odell

G G’
MILES

Roberts
0 0 5 5 10 10 20 20

Location map

KILOMETERS

Figure section G-G’ through G-G’ through the Powder River Basin assessment area showing subsurface distribution of coal beds. Vertical exaggeration Figure 18. Cross 18. Cross sectionthe Northern WyomingNorthern Wyoming Powder River Basin assessment area showing subsurface distribution of approximately ×5,000. (Vertical exaggeration approximately 5,000 X). coal beds.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Stripping ratio 10:1or > 9:1 8:1 7:1 6:1 5:1 4:1 3:1 2:1 1:1 <1:1 Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Town of Sheridan

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 19. Map showing stripping ratio for Roland of Baker (1929), Smith, Anderson, Dietz 3, Canyon, Lower Canyon, and Werner coal beds.
Figures

Figure 19. Stripping ratio of the Roland of Baker (1929), Smith, Anderson, Dietz 3, Canyon, Lower Canyon, and Werner coal beds.

55

107 o 00’

106 o 00’

105 o 00’

56

EXPLANATION
R. 53 E. R. 54 E. R. 55 E. T. 8 S.
Elevation (ft)
4,400 4,200

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

4,000 3,800 3,600 3,400 3,200 3,000 2,800 2,600 2,400 2,200 2,000 1,800

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Fault Town of Sheridan

T. 55 N.

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

INDEX MAP

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 20. Map showing elevation at top of the Canyon coal bed and fault along southwestern edge of the Northern Wyoming Powder River Basin assessment area.

Figure 20. Elevation at top of the Canyon coal bed and fault along southwestern edge of the Northern Wyoming Powder River Basin assessment area.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Thickness (ft)
60 40 20 10 5

Big Horn County

Powder River County

45 00’

o

T. 9 S.

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

2.5

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 21.21. Isopach map extent of resources at least 2.5 feet showing extent of resources greater than 2.5 ft thick. Figure Isopachs showing of the Upper Healy coal bed thick in the Upper Healy coal bed.

Figures 57

107 o 00’

106 o 00’

105 o 00’

58

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

EXPLANATION
T. 9 S.
Depth to top of coal (ft)
500

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

250 1

Northern Wyoming Powder River Basin assessment area

T. 56 N.

Gillette coal Ffeld boundary Basin axis (approximate) Town of Sheridan

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.

R. 78 W.

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

0 0 5

5 10

10

20 MILES 20 KILOMETERS

Figure 22. Depth to top of coal in the Upper Healy coal bed.

Figure 22. Map showing depth to the top of the Upper Healy coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 23.23. Map showing coal resource reliability Healy coal bed. the Upper Healy coal bed. Figure Coal resource reliability categories of the Upper categories for

Figures 59

107 o 00’

106 o 00’

105 o 00’

60

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 54 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Thickness (ft)
60 40 20

Big Horn County

Powder River County

45 00’

o

T. 9 S.

MONTANA WYOMING
T. 58 N. T. 57 N.

10 5

T. 56 N.

2.5

Northern Wyoming Powder River Basin assessment area

T. 55 N.

Gillette coal eld boundary Town of Sheridan

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 24. Isopach map of the Healy coal bed showing extent of resources greater than 2.5 ft thick.

Figure 24. Isopachs showing extent of resources at least 2.5 feet thick in the Healy coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
1,000 500

Big Horn County

Powder River County

45 00’

o

T. 9 S.

MONTANA WYOMING
T. 58 N. T. 57 N.

250 1

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 25. Map showing depth to the top of the Healy coal bed.

Figure 25. Depth to top of coal in the Healy coal bed.

Figures 61

107 o 00’

106 o 00’

105 o 00’

62

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

45 00’

o

T. 9 S.

EXPLANATION
Hypothetical

MONTANA WYOMING
T. 58 N. T. 57 N.

Inferred Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 26. Coal resource reliability categories of the Healy coal bed.

Figure 26. Map showing coal resource reliability categories for the Healy coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Thickness (ft)
40 20 10

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

5 2.5

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5 5

R. 78 W.
10

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

10

Figure 27. Figure 27.Isopachs showing of theof resources at bed showing extentUcross coal bed.greater than 2.5 ft thick. Isopach map extent Ucross coal least 2.5 feet thick in the of resources

Figures 63

107 o 00’

106 o 00’

105 o 00’

64

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Depth to top of coal (ft)
1,000 500

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

250 1

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

T. 55 N.

Basin axis (approximate) Town of Sheridan

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.
Mine area (abandoned)

T. 53 N.
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 28. Depth to top of coal in the Ucross coal bed.

Figure 28. Map showing depth to the top of the Ucross coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

EXPLANATION
T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Hypothetical Inferred Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)

T. 53 N.
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 29. Coal resource reliability categories of the Ucross coal bed.

Figure 29. Map showing coal resource reliability categories for the Ucross coal bed.

Figures 65

107 o 00’

106 o 00’

105 o 00’

66

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Thickness (ft)
40

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

20 10 5 2.5

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal Ffeld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 30. Isopach map of the Felix coal bed showing extent of resources greater than 2.5 ft thick.

Figure 30. Isopachs showing extent of resources at least 2.5 feet thick in the Felix coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

EXPLANATION
Depth to top of coal (ft)
1,000 500 250 1

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 31. Depth to top of coal in the Felix coal bed.

Figure 31. Map showing depth to the top of the Felix coal bed.
Figures 67

107 o 00’

106 o 00’

105 o 00’

68

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

EXPLANATION
Inferred Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal Ffeld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)

T. 53 N.

INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 32. Figure 32.Coal resource reliability categories of the Felix coal bed. Map showing coal resource reliability categories for the Felix coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Thickness (ft)
60 40 20 10 5

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

2.5

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 33. Isopachs showing extent of resources at least 2.5 feet thick in the Lower Felix coal bed.

Figure 33. Isopach map of the Lower Felix coal bed showing extent of resources greater than 2.5 ft thick.

Figures 69

107 o 00’

106 o 00’

105 o 00’

70

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Depth to top of coal (ft)
1,500 1,000 500

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

250 1

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate)

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’
WYOMING
o

Big Horn County

Campbell County

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 34. Depth to top of coal in the Lower Felix coal bed.

Figure 34. Map showing depth to the top of the Lower Felix coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 35. Coal resource reliability categories of the Lower Felix coal bed.

Figure 35. Map showing coal resource reliability categories for the Lower Felix coal bed.

Figures 71

107 o 00’

106 o 00’

105 o 00’

72

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Thickness (ft)
20 10 5

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

2.5

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

T. 55 N.

Town of Sheridan

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
INDEX MAP

T. 53 N.
WYOMING

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 36. Isopach map of the Roland Upper Rider coal bed showing extent of resources greater than 2.5 ft thick.

Figure 36. Isopachs showing extent of resources at least 2.5 feet thick in the Roland (Upper Rider) coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Depth to top of coal (ft)
2,000 1,500 1,000 500 250 1

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate)

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 37. Depth to top of coal in the Roland (Upper Rider) coal bed.

Figure 37. Map showing depth to the top of the Roland Upper Rider coal bed.
Figures 73

107 o 00’

106 o 00’

105 o 00’

74

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

45 00’

o

T. 9 S.

EXPLANATION
Hypothetical

MONTANA WYOMING
T. 58 N. T. 57 N.

Inferred Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 38. Coal resource reliability categories of the Roland (Upper Rider) coal bed.

Figure 38. Map showing coal resource reliability categories for the Roland Upper Rider coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

EXPLANATION
T. 9 S.
Thickness (ft)
40 20 10 5 2.5

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)

T. 53 N.

INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 39.39. Isopach map extent of resources at least 2.5 feet thick inbedRoland of Baker (1929) coal bed. Figure Isopachs showing of the Roland of Baker (1929) coal the showing extent of resources greater than 2.5 ft thick.

Figures 75

107 o 00’

106 o 00’

105 o 00’

76

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Depth to top of coal (ft)
2,000

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

1,500 1,000 500 250 1

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 40. Depth to top of coal in the Roland of Baker (1929) coal bed.

Figure 40. Map showing depth to the top of the Roland of Baker (1929) coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

EXPLANATION
Hypothetical Inferred Indicated Measured

T. 56 N.
Northern Wyoming Powder River Basin assessment area

T. 55 N.

Gillette coal eld boundary Town of Sheridan

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 41. Map showing coal resource reliability categories for the Roland of Baker (1929) coal bed.

Figure 41. Coal resource reliability categories of the Roland of Baker (1929) coal bed.

Figures 77

107 o 00’

106 o 00’

105 o 00’

78

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Thickness (ft)
40 20 10 5 2.5

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)

T. 53 N.
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 42. Isopachs showing extent of resources at least 2.5 feet thick in the Roland of Taff (1909) coal bed.

Figure 42. Isopach map of the Roland of Ta (1909) coal bed showing extent of resources greater than 2.5 ft thick.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Depth to top of coal (ft)
2,000 1,500 1,000 500 250

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

1

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 43. Map showing depth to the top of the Roland of Ta (1909) coal bed.
Figures

Figure 43. Depth to top of coal in the Roland of Taff (1909) coal bed.

79

107 o 00’

106 o 00’

105 o 00’

80

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 44. Coal resource reliability categories of the Roland of Taff (1909) coal bed.

Figure 44. Map showing coal resource reliability categories for the Roland of Ta (1909) coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Thickness (ft)
40

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

20 10 5 2.5

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)

T. 53 N.

INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 45. Isopachs showing extent of resources at least 2.5 feet thick in the Smith coal bed.

Figure 45. Isopach map of the Smith coal bed showing extent of resources greater than 2.5 ft thick.

Figures 81

107 o 00’

106 o 00’

105 o 00’

82

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
2,500 2,000

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

1,500 1,000 500 250

T. 56 N.

1

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 46. Depth to top of coal in the Smith coal bed.

Figure 46. Map showing depth to the top of the Smith coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

EXPLANATION
Hypothetical Inferred Indicated Measured

T. 56 N.
Northern Wyoming Powder River Basin assessment area

T. 55 N.

Gillette coal eld boundary Town of Sheridan

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’
WYOMING
o

Big Horn County

Campbell County

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 47. Map showing coal resource reliability categories for the Smith coal bed.

Figure 47. Coal resource reliability categories of the Smith coal bed.

Figures 83

107 o 00’

106 o 00’

105 o 00’

84

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Thickness (ft)
60 40 20 10 5

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

2.5

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

AN

NE

L

T. 55 N.

Sheridan County Johnson County

CH

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 48. Isopach map of the Anderson coal bed showing extent of resources greater than 2.5 ft thick.

Figure 48. Isopachs showing extent of resources at least 2.5 feet thick and channel area in the Anderson coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
2,500 2,000 1,500 1,000 500 250 1

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal Ffeld boundary Basin axis (approximate)

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 49. Map showing depth to the top of the Anderson coal bed.
Figures

Figure 49. Overburden thickness above the Anderson coal bed.

85

107 o 00’

106 o 00’

105 o 00’

86

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Inferred Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 50. Coal resource reliability categories of the Anderson coal bed.

Figure 50. Map showing coal resource reliability categories for the Anderson coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Thickness (ft)
60 40

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

20 10 5

T. 56 N.

2.5

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

AN

NE

L

CH

T. 55 N.
Mine area (abandoned)
INDEX MAP

Sheridan County Johnson County

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 51. Isopachs showing extent of resources at least 2.5 feet thick and channel area in the Lower Anderson coal bed.

Figure 51. Isopach map of the Lower Anderson coal bed showing extent of resources greater than 2.5 ft thick and channel area.

Figures 87

107 o 00’

106 o 00’

105 o 00’

88

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

45 00’

o

T. 9 S.

Depth to top of coal (ft)
2,000 1,500 1,000 500 250 1

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate)

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.

R. 78 W.

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

0 0 5

5 10

10

20 MILES 20 KILOMETERS

Figure 52. Depth to top of coal in the Lower Anderson coal bed.

Figure 52. Map showing depth to the top of the Lower Anderson coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 53. Resource reliability categories of the Lower Anderson coal bed.

Figure 53. Map showing coal resource reliability categories for the Lower Anderson coal bed.

Figures 89

107 o 00’

106 o 00’

105 o 00’

90

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

EXPLANATION
T. 9 S.
Thickness (ft)
40

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

20 10 5 2.5

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 54. Isopachs showing extent of resources at least 2.5 feet thick in the Dietzresources greater than 2.5 ft thick. Figure 54. Isopach map of the Dietz 1 coal bed showing extent of 1 coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Depth to top of coal (ft)
2,000 1,500

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

1,000 500 250 1

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate)

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.

R. 78 W.

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

0 0 5

5 10

10

20 MILES 20 KILOMETERS

Figure 55. Depth to top of coal in the Dietz 1 coal bed.

Figure 55. Map showing depth to the top of the Dietz 1 coal bed.
Figures 91

107 o 00’

106 o 00’

105 o 00’

92

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 56. Coal resource reliability categories of the Dietz 1 coal bed.

Figure 56. Map showing coal resource reliability categories for the Dietz 1 coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Thickness (ft)
40 20 10

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

5 2.5

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure Isopachs showing of the resources at bed showing in the Dietz 2 coal bed. Figure 57.57. Isopach mapextent ofDietz 2 coalleast 2.5 feet thickextent of resources greater than 2.5 ft thick.

Figures 93

107 o 00’

106 o 00’

105 o 00’

94

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Depth to top of coal (ft)
2,000 1,500

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

1,000 500 250 1

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate)

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 58. Depth to top of coal for the Dietz 2 coal bed.

Figure 58. Map showing depth to the top of the Dietz 2 coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 59. Map showing coal resource reliability categories for the Dietz 2 coal bed.
Figures

Figure 59. Coal resource reliability categories of the Dietz 2 coal bed.

95

107 o 00’

106 o 00’

105 o 00’

96

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Thickness (ft)
80

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

60 40 20 10 5

T. 56 N.

2.5

NE

AN

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

L

EAS NEL HAN TC

T

CH

Sheridan County Johnson County

W

ES

T. 55 N.

Town of Sheridan

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
WYOMING
o

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 60. Isopachs showing extent of resources at least 2.5 feet thick and west and east channels in the Dietz 3 coal bed.

Figure 60. Isopach map of the Dietz 3 coal bed showing extent of resources greater than 2.5 ft thick and the west and east channels.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
2,500 2,000 1,500 1,000 500 250 1

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate)

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.

R. 78 W.

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

0 0 5

5 10

10

20 MILES 20 KILOMETERS

Figure 61. Depth to top of coal in the Dietz 3 coal bed.

Figure 61. Map showing depth to the top of the Dietz 3 coal bed.
Figures 97

107 o 00’

106 o 00’

105 o 00’

98

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 62. Coal resource reliability categories of the Dietz 3 coal bed.

Figure 62. Map showing coal resource reliability categories for the Dietz 3 coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

EXPLANATION
T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Thickness (ft)
20 10 5 2.5

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 63.63. Isopach map extent of resources at least 2.5 feet thick in the Dietzresources greater than 2.5 ft thick. Figure Isopachs showing of the Dietz 4 coal bed showing extent of 4 coal bed.

Figures 99

107 o 00’

106 o 00’

105 o 00’

100

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
2,500 2,000

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

1,500 1,000 500 250

T. 56 N.

1

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.

R. 78 W.

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

0 0 5

5 10

10

20 MILES 20 KILOMETERS

Figure 64. Map showing depth to the top of the Dietz 4 coal bed.

Figure 64. Depth to top of coal in the Dietz 4 coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

EXPLANATION
Inferred Indicated Measured

T. 56 N.
Northern Wyoming Powder River Basin assessment area

T. 55 N.

Gillette coal eld boundary Town of Sheridan

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 65.65. Map showing coal resource reliability categories for the Dietz 4 coal bed. Figure Coal resource reliability categories of the Dietz 4 coal bed.

Figures 101

107 o 00’

106 o 00’

105 o 00’

102

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION

Northern Wyoming Powder River Basin Coal

Thickness (ft)
Big Horn County Powder River County

T. 9 S.

80 60 40 20 10 5

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

2.5

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

T. 55 N.

Town of Sheridan

CH

Sheridan County Johnson County

AN NE L

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.

R. 78 W.

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

0 0 5

5 10

10

20 MILES 20 KILOMETERS

Figure 66. Figure 66.Isopachs showingof the of resources at least 2.5 feet thickextent of resources greatercoal bed. ft thick and channel area. Isopach map extent Canyon coal bed showing and channel area in the Canyon than 2.5

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
2,500 2,000

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

1,500 1,000 500 250

T. 56 N.

1

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

T. 55 N.

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 67. Map showing depth to the top of the Canyon coal bed.
Figures

Figure 67. Depth to top of coal in the Canyon coal bed.

103

107 o 00’

106 o 00’

105 o 00’

104

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical Inferred

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 68. Coal resource reliability categories of the Canyon coal bed.

Figure 68. Map showing coal resource reliability categories for the Canyon coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Thickness (ft)
60 40

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

20 10 5

T. 56 N.

2.5

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

NE

L

CH

AN

T. 55 N.
Mine area (abandoned)
INDEX MAP

Sheridan County Johnson County

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 69. Isopachs showing extent of resources at least 2.5 feet thick and channel area in the Lower Canyon coal bed.

Figure 69. Isopach map of the Lower Canyon coal bed showing extent of resources greater than 2.5 ft thick and channel area.
Figures 105

107 o 00’

106 o 00’

105 o 00’

106

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION

Northern Wyoming Powder River Basin Coal

Depth to top of coal (ft)
Big Horn County Powder River County
3,000

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

2,500 2,000 1,500 1,000 500 250

T. 56 N.

1

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.
Mine area (abandoned)

T. 52 N.
44 30’ Big Horn County
Campbell County
o

INDEX MAP

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 70. Depth to top of coal in the Lower Canyon coal bed.

Figure 70. Map showing depth to the top of the Lower Canyon coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical Inferred

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 71. Coal resource reliability categories of the Lower Canyon coal bed. the Lower Canyon coal bed. Figure 71. Map showing coal resource reliability categories for

Figures 107

107 o 00’

106 o 00’

105 o 00’

108

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Thickness (ft)
40

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

20 10 5 2.5

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)

T. 53 N.

INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 72.72. Isopach mapextent ofFerry coal bed showing extent of resources greater than 2.5 ft thick. Figure Isopachs showing of the resources at least 2.5 feet thick in the Ferry coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
3,000 2,500 2,000 1,500 1,000 500 250

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

1

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.
Mine area (abandoned)

T. 52 N.
44 30’ Big Horn County
Campbell County
o

INDEX MAP

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.

R. 78 W.

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

0 0 5

5 10

10

20 MILES 20 KILOMETERS

Figure 73. Map showing depth to the top of the Ferry coal bed.
Figures

Figure 73. Depth to top of coal in the Ferry coal bed.

109

107 o 00’

106 o 00’

105 o 00’

110

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 74. Coal resource reliability categories of the Ferry coal bed.

Figure 74. Map showing coal resource reliability categories for the Ferry coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Thickness (ft)
80 60

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

40 20 10 5

T. 56 N.

2.5

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

T. 55 N.

AN

Sheridan County Johnson County

NE

L

Town of Sheridan

CH

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 75. Isopach map of the Werner coal bed showing extent of resources greater than 2.5 ft thick and channel area.

Figure 75. Isopachs showing extent of resources at least 2.5 feet thick and channel area in the Werner coal bed.

Figures 111

107 o 00’

106 o 00’

105 o 00’

112

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
4,000

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

3,000 2,500 2,000 1,500

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

1,000 500 250

T. 56 N.

1

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Basin axis (approximate) Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
WYOMING

T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 76. Depth to top of coal in the Werner coal bed.

Figure 76. Map showing depth to the top of the Werner coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Inferred Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.

R. 78 W.

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

0 0 5

5 10

10

20 MILES 20 KILOMETERS

Figure 77. Map showing coal resource reliability categories for the Werner coal bed.
Figures

Figure 77. Coal resource reliability categories of the Werner coal bed.

113

107 o 00’

106 o 00’

105 o 00’

114

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Thickness (ft)
80 60

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

40 20 10 5

T. 56 N.

2.5

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.

WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 78. Isopachs showing extent of resources at least 2.5 feet thick in the Otter coal bed.

Figure 78. Isopach map of the Otter coal bed showing extent of resources greater than 2.5 ft thick.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
4,000 3,000 2,500

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

2,000 1,500 1,000 500

T. 56 N.

250 1

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

Basin axis (approximate) Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
WYOMING

T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10 10

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 79. Depth to top of coal in the Otter coal bed.

Figure 79. Map showing depth to the top of the Otter coal bed.
Figures 115

107 o 00’

106 o 00’

105 o 00’

116

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical Inferred Indicated Measured

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’
Campbell County
o

WYOMING

Big Horn County

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 80. Coal resource reliability categories of the Otter coal bed.

Figure 80. Map showing coal resource reliability categories for the Otter coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Thickness (ft)
60 40 20 10 5

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

2.5

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 81. Isopachs showing extent of resources at least 2.5 feet thick in the Gates coal bed.

Figure 81. Isopach map of the Gates coal bed showing extent of resources greater than 2.5 ft thick.
Figures 117

107 o 00’

106 o 00’

105 o 00’

118

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
4,000

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

3,000 2,500

MONTANA WYOMING
T. 58 N. T. 57 N.

2,000 1,500 1,000 500

T. 56 N.

250 1

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan Mine area (abandoned)
INDEX MAP

ea Ar of no ta da
T. 55 N.
Sheridan County Johnson County

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
WYOMING

T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 82. Depth to top of coal in the Gates coal bed.

Figure 82. Map showing depth to the top of the Gates coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Inferred Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 83. Map showing coal resource reliability categories for the Gates coal bed.
Figures

Figure 83. Coal resource reliability categories of the Gates coal bed.

119

107 o 00’

106 o 00’

105 o 00’

120

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Thickness (ft)
40

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

20 10 5

T. 56 N.

2.5

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 84. Isopachs showing extent of resources at least 2.5 feet thick in the Pawnee coal bed.

Figure 84. Isopach map of the Pawnee coal bed showing extent of resources greater than 2.5 ft thick.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
4,000

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

3,000 2,500 2,000 1,500 1,000 500

T. 56 N.

250 1

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan Mine area (abandoned)
INDEX MAP

ea Ar of no ta da
T. 55 N.
Sheridan County Johnson County

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
WYOMING

T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 85. Map showing depth to the top of the Pawnee coal bed.
Figures

Figure 85. Depth to top of coal in the Pawnee coal bed.

121

107 o 00’

106 o 00’

105 o 00’

122

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

EXPLANATION
Hypothetical Inferred

MONTANA WYOMING
T. 58 N. T. 57 N.

Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5 5

R. 78 W.
10

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

10

Figure 86. Map showing coal resource reliability categories for the Pawnee coal bed.

Figure 86. Coal resource reliability categories of the Pawnee coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Thickness (ft)
40 20 10 5 2.5

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10 10

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 87. Isopachs showing extent of resources at least 2.5 feet thick in the Odell coal bed.

Figure 87. Isopach map of the Odell coal bed showing extent of resources greater than 2.5 ft thick.
Figures 123

107 o 00’

106 o 00’

105 o 00’

124

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
4,000

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

3,000 2,500

MONTANA WYOMING
T. 58 N. T. 57 N.

2,000 1,500 1,000 500

T. 56 N.

250 1

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate) Town of Sheridan Mine area (abandoned)
INDEX MAP

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
WYOMING

T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10 10

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 88. Depth to top of coal in the Odell coal bed.

Figure 88. Map showing depth to the top of the Odell coal bed.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Big Horn County

Powder River County

T. 9 S.

EXPLANATION
Hypothetical Inferred

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Indicated Measured

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 89. Figure 89.Coal resource reliability categories of the Odell coal bed. Map showing coal resource reliability categories for the Odell coal bed.

Figures 125

107 o 00’

106 o 00’

105 o 00’

126

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

T. 9 S.

Thickness (ft)
40 20 10 5 2.5

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

T. 56 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)

T. 53 N.

INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

WYOMING

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10 10

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 90. Isopachs showing extent of resources at least 2.5 feet thick in the Roberts coal bed.

Figure 90. Isopach map of the Roberts coal bed showing extent of resources greater than 2.5 ft thick.

107 o 00’

106 o 00’

105 o 00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E. T. 8 S.

EXPLANATION
Depth to top of coal (ft)
5,000 4,000 3,000 2,500 2,000

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

1,500 1,000 500

T. 56 N.

250 1

T. 55 N.

Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Basin axis (approximate)

ea Ar of no ta da
Sheridan County Johnson County

T. 55 N.

T. 53 N.

Town of Sheridan Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’ Big Horn County
Campbell County
o

T. 51 N.
T. 50 N.
WYOMING

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10 10

R. 77 W.

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W. R. 68 W.

20 MILES 20 KILOMETERS

Figure 91. Depth to top of coal in the Roberts coal bed.

Figure 91. Map showing depth to the top of the Roberts coal bed.
Figures 127

107 o 00’

106 o 00’

105 o 00’

128

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

Big Horn County

Powder River County

T. 9 S.

45 00’

o

MONTANA WYOMING
T. 58 N. T. 57 N.

EXPLANATION
Hypothetical Inferred Indicated Measured

T. 56 N.
Northern Wyoming Powder River Basin assessment area Gillette coal eld boundary Town of Sheridan

T. 55 N.

T. 55 N.
Sheridan County Johnson County

T. 53 N.

Mine area (abandoned)
INDEX MAP

T. 52 N.
44 30’
WYOMING
o

Big Horn County

Campbell County

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0

R. 78 W.
5 5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 92. Coal resource reliability categories of the Roberts coal bed.

Figure 92. Map showing coal resource reliability categories for the Roberts coal bed.

Restriction to mining Coal bed

EXPLANATION

Mine accessible coal-bearing rock Surface restriction and bu er projected downward (coal unavailable for mining) Additional restriction due to required mine pit highwall angle (coal unavailable for mining)
Surface restriction Bu er distance Bu er distance

300 ft

300 ft

26 o 500 ft 858 ft
Mine bench

200 ft

26 o

Horizontal limits of projected surface restriction and buffer

Mine bench

2,144 ft
Figure 93. Effect of coal bed depth upon restricted resource due to mine pit highwall setback requirements (not to scale).

Figure 93. Illustration showing the e ect of coal bed depth upon restricted resource due to mine pit highwall setback requirements (not to scale).

Figures 129

-107 o 00’

130

-106 o 00’

-105 o00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

Northern Wyoming Powder River Basin Coal

EXPLANATION
Big Horn County Powder River County

T. 9 S.

45 00’
Alluvial Valley oor

o

MONTANA WYOMING
T. 58 N. T. 57 N.

Alluvial valley oor Town bu er Railroad NWPRB assessment area

Ranchester

Sheridan

T. 56 N.

Gillette coal eld boundary Interstate 90

T. 55 N.

Town of Sheridan

Clearmont
Sheridan County Johnson County

Alluvial Valley oor

T. 55 N.

Mine area (abandoned) Lake DeSmet
INDEX MAP

T. 53 N.
Lake DeSmet

44 30’

o

90
Campbell County

T. 52 N.

WYOMING

Big Horn County

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 94. Map showing land use restrictions for the Northern Wyoming Powder River Basin assessment area.

Figure 94. Land use restrictions in the Northern Wyoming Powder River Basin assessment area.

-107 o 00’

-106 o 00’

-105 o00’

R. 36 E.

R. 37 E.

R. 38 E. R. 39 E.

R. 40 E.

R. 41 E.

R. 42 E.

R. 43 E.

R. 44 E.

R. 45 E.

R. 46 E.

R. 47 E.

R. 48 E.

R. 49 E.

R. 50 E.

R. 51 E.

R. 52 E.

R. 53 E. R. 54 E.

R. 55 E.

T. 8 S.

EXPLANATION
Big Horn County Powder River County

45 00’

o

MONTANA WYOMING

T. 9 S. T. 58 N. T. 57 N.

Federal coal State coal Private coal NWPRB assessment area Gillette coal eld boundary Interstate 90 Town of Sheridan

T. 56 N.

T. 55 N.

T. 55 N.
Sheridan County Johnson County

Mine area (abandoned)
T. 53 N.
INDEX MAP

44 30’

o

90
Campbell County

T. 52 N.
WYOMING

Big Horn County

T. 51 N.
T. 50 N.

R. 87 W.

R. 86 W.

R. 85 W.

R. 84 W.

R. 83 W.

R. 82 W.

R. 81 W.

R. 80 W. R. 79 W.
0 0 5

R. 78 W.
5 10

R. 77 W.
10

R. 76 W.

R. 75 W.

R. 74 W.

R. 73 W.

R. 72 W.

R. 71 W.

R. 70 W.

R. 69 W.

R. 68 W.

20 MILES 20 KILOMETERS

Figure 95. Map showing coal ownership in the Northern Wyoming Powder River Basin assessment area.
Figures

Figure 95. Coal ownership in the Northern Wyoming Powder River Basin assessment area.

131

Elevation in feet 6000 -

132 Northern Wyoming Powder River Basin Coal

5500-

5000-

4500-

Approximate Land Surface

H’
4000-

Anderson H
3500-

Canyon

H H’
Gillette Coal Field

3000-

Location map
0 0 1 1 2 2 MILES KILOMETERS

Figure 96. Southeast-northwest cross section H-H’ showing rapid increase in interburden thickness in a channel separating the Anderson and Canyon Figure 96. Cross section H-H’ coal beds in the Gillette coal showing rapid ed from in interburden thickness in a channel separating the Anderson and Canyon coal beds in the Gillette coal field (modified eld. (Modi increase Luppens and others, 2008).
from Luppens and others, 2008).

Reserve Recoverable resource Additional resource

$35.00

$30.00

$25.00
DFC COST PER TON

$20.00

$15.00

$10.00 $9.30 $5.00

$0.00

1.5 0

5

10

15

20

25

30

35

40

45

50

55
Figures

BILLIONS OF TONS

Figure 97. Reserve estimate Curve line tons at $9.30/ton (as of February 1010) for the Northernreserves Powder River Basin assessment area.projected only to the Basin assessment area. of 1.5 billion is dashed above the 5:1 strip ratio because Wyoming and recoverable resources are Curve is dashed above the 5:1 strip ratio because reserves are projected only to the 5:1 strip ratio. 5:1 strip ratio.

Figure 97. Cost curve showing 1.5 billion ton reserve estimate at $9.30/ton (as of February, 2010) for the Northern Wyoming Powder River
133

134 Northern Wyoming Powder River Basin Coal

COAL RESOURCE CATEGORY

Original Resource --158 Remaining Resource -- 157 Available Resource --56 Recoverable Resource --50 1.5 Economic Resource

0

20

40

60

80

100

120

140

160

180

RESOURCE IN BILLIONS OF SHORT TONS (BST)
Figure 98. 98. Bar graph showing resources in different resourcebeds includedforthe reserve evaluation (5.0 ft thick orin the reserve evaluation (5.0 ftof the Figure. Resources in different resource categories for the seven coal categories in the seven coal beds included greater, 10:1 stripping ratio or less) thick Northern Wyoming Powder River Basin assessment area, reported in short tons (at a sales price of $9.30 as of February 2010). or greater, 10:1 stripping ratio or less) of the Northern Wyoming Powder River Basin assessment area, reported in short tons (at a sales price of

$9.30 as of February, 2010).

Figures

135

Coal resource
ORIGINAL REMAINING AVAILABLE RECOVERABLE ECONOMIC
0
59

Percentages
100 99 35 32 1
10

Exclusions
None

1 64 48

Coal already mined Restricted

3

Future mining losses
Uneconomic

31
20 30 40 50 60 70 80 90 100

Figure 99. Results showing Northern Wyoming Powder River Basin assessment area coal resource evaluation results for the seven Figure 99. Bar graph of coal resource analysis in the Northern Wyoming Powder River Basin assessment area for the seven coal beds reported as percentages of original resources (at a sales price of $9.30 as of February, 2010). Percent of remaining resources is shown coal beds included in the reserve evaluation. Results reported as percentage of original resource (at a sales price of $9.30 in colored bars; excluded resources from the previous category are shown in white bars. as of February 2010). Percent of remaining resource is shown in colored bars; excluded from the previous category is shown in white bars.

136 Northern Wyoming Powder River Basin Coal

$35
$31.00

Gillette coal field Northern Wyoming Powder River Basin assessment area

$30
$26.19

$28.29 $25.40

$30.72

$25
$21.20

$23.57

Cost per ton

$20 $15
$10.73

$18.17 $18.20 $14.09 $12.30 $9.80 $8.30 $6.60 $14.70

$20.90

$10
$7.26

$5 $0

$5.40 $4.87

1:1

2:1

3:1

4:1

5:1

6:1

7:1

8:1

9:1

10:1

Stripping ratio
Figure 100. Miningfield. (discounted cash flow, 8 percent rate of return) for Northern Wyoming Powder River Basin assessment area Gillette coal costs vs. the Gillette coal field.
Figure 100. Mining costs (discounted cash flow, 8 percent rate of return) for Northern Wyoming Powder River Basin assessment area compared with mining costs in the

Scott and others—Assessment of Coal Geology, Resources, and Reserves in the Northern Wyoming Powder River Basin—Open-File Report 2010–1294