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Home , Chugwater Formation, Cody Shale, Fort Union Formation, Harding Sandstone, Lakota Formation, Lance Formation

AECOM 2-1

2.0 Description of Current Conditions

This chapter presents the existing environmental conditions in the PRB study area, with the exception of water resources, air quality, and social and economic conditions (which are presented in standalone Task 1 reports) and cultural resources, which is addressed in the BLM Cultural Class I Regional Overview – Buffalo Field Office. The baseline information summarized in this chapter was obtained from published and unpublished information; interviews with local, state, and federal agencies; and the compilation of past and present actions in the Wyoming PRB, as presented in the Task 2 Report for the PRB Review (AECOM 2011).

As of the end of base 2008 existing disturbance acreages presented in this report were based on the data compiled for the Task 2 report (AECOM 2011) and, where resource-specific data were required, the associated Geographical Information System (GIS) information. The disturbance acreages generated through GIS vary from the disturbance acreages in the Task 2 data spreadsheets due to the following variables. The information in the Task 2 data spreadsheets was compiled from information obtained from the data sources and the applied assumptions defined in the Task 2 report. As a result, the data in the spreadsheets specifies a discrete disturbance acreage for each of the energy-related development activities (e.g., coal mines, individual oil and gas wells, etc.) identified for the study. Conversely, the GIS analysis considers the spatial relationship of the various development activities, thereby avoiding double counting of disturbance acreages where mapped disturbance areas overlap. Also, slight variations between the GIS study area boundary and GIS resource-specific layers resulted in some under counting of disturbance acreages. Where disturbance acreages are presented in this report, the appropriate source is noted.

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2.1 Topography, Geology, Minerals, and Paleontological Resources 2.1.1 Key Issues The key issues related to topography, geology, minerals, and paleontology include:

• The permanent alteration of topography from coal mining and to a lesser degree, from oil and gas drilling; • Access to mineral resources (e.g., oil and gas development may be temporarily precluded by active coal mining); and • Potential loss of scientific and educational value of paleontological resources due to the damage, destruction, or improper collection of resources in association with energy-related development activities.

With the advent of widespread horizontal and directional drilling for oil and gas, access to mineral resources may not present as large a concern as in the past. Additionally, the exclusion of oil and gas would be temporary in mine areas once mining is completed and the mined areas are reclaimed.

2.1.2 Study Area The study area for topography, geology, minerals, and paleontological resources generally includes all or portions of Campbell, Johnson, Sheridan, and Converse counties (Figure 1-1). It includes most of the area administered by the BLM Buffalo Field Office, a portion of the area administered by the BLM Casper Field Office, and a portion of the TBNG, which is administered by the FS (Figure 1-2). State and private lands also are included in the study area (Figure 1-3). However, some historical predictions of mineral production trends came from documents (BLM 1981, 1996, 2004, 2009) that analyzed mineral production in project areas defined differently from this study area. Some information concerning the mineral production history occurred outside of the defined study area; however, this information is presented because of the relevance to the study area. In addition, certain aspects of general geology (, structural geology) are discussed for the entire PRB, including .

2.1.3 Current Conditions The Phase I description of existing conditions in the Wyoming PRB study area for topography, geology, and minerals has been updated based on information from the Wyoming Oil and Gas Conservation Commission (WOGCC) on-line production data, public BLM documents, IHS Energy Services™ (IHS) well data, Wyoming State Geological Survey and U.S. Geological Survey (USGS) publications, other published documents, and the past and present action descriptions presented in the PRB Coal Review Task 2 Report (AECOM 2011). The description of existing conditions in the Wyoming PRB study area for paleontological resources reflects changes in BLM guidance and policy (BLM 2007, 2008b) and passage of the Paleontological Resources Preservation Act of 2009 (BLM 2012).

2.1.3.1 Topography and Physiography The PRB is located within the Upper Missouri Basin Broken Lands physiographic subprovince that includes northeastern Wyoming and eastern Montana to the Canadian border (USGS 1970). The topography generally is of low to moderate relief with occasional buttes and mesas (Radbruch-Hall et al. 1980). The underlying bedrock in some areas is very erodible, which in places results in heavily dissected to badland-type topography. The general topographic gradient slopes down gently (generally southwest to northeast) with elevations ranging from 5,000 to 6,000 feet above mean sea level (amsl) on the southern and western portions of the basin to less than 4,000 feet amsl on the north and northeast along the Montana state line. The Wyoming portion of the basin is bounded on the west by the Big Horn Mountains and the Casper Arch, on the south by the Laramie Mountains, on the southeast by the Hartville Uplift, and on the east by the (Figure 2.1-1).

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EXPLANATION

Qal Tw Tertiary Tftr Tertiary Member of the Tfu Undifferentiated Tongue River and Lebo Members of the Fort Union Formation Tfl Tertiary Lebo Member of the Fort Union Formation Tft Tertiary Tullock Member of the Fort Union Formation Kl B Lines of cross section Structural axis of the basin

Powder River Basin Coal Review

Figure 2.1-1

General Geology of the Source: Flores 2004.

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The major drainages in the basin flow from south to north or east to west and include the Tongue, Powder, Belle Fourche, and Cheyenne rivers (Figure 1-1). Most of the drainages in the area are intermittent and have flows during high precipitation events or during periods of snowmelt. The drainages are part of the upper Valley drainage basin. The Tongue River flows from the Big Horn Mountains and drains a small portion of the northwestern portion of the Wyoming PRB study area. The north-flowing Powder River and major tributaries also have headwaters in the Big Horn Mountains and drain much of the western portion of the PRB. The Belle Fourche River flows northeast and its drainage basin occupies much of the eastern portion of the study area. The Cheyenne River drains the southeastern portion of the PRB and generally flows to the east.

Surface coal mining alters the topography in mining areas by causing changes in slope, lowering the general land surface, and changing the physical nature of the surficial materials and overburden. The topography is affected only where mining occurs. Oil and gas exploration and development alter the landscape through leveling the land surface for drilling pads and cutting and filling during road construction. Oil and gas development affects topography to a much lesser degree than coal mining; however, it is more widespread than coal mining.

2.1.3.2 Geology Stratigraphy and Geologic History The PRB contains Phanerozoic rocks (younger than ) over 17,000 feet in thickness. These rocks range in age from to Tertiary (Figure 2.1-2). In addition, there are unconsolidated alluvial and surficial deposits. Most of the rocks are older than Tertiary outcrop along edges of the Wyoming PRB study area and also are found in the subsurface of the basin or are exposed along the margins of the basin. The following contains brief summaries of the rocks that are found in the study area.

Precambrian Era. The Precambrian rocks that are exposed in the adjacent mountain ranges and underneath the Phanerozoic rocks in the basin are complex assemblages of igneous and metamorphic rocks (Houston 1993). The Precambrian rocks are the oldest at billions of old.

Paleozoic Era. During early Paleozoic time, present-day Wyoming and much of the Rocky Mountain West were located along a fairly stable continental shelf (Lageson and Spearing 1991).

The area generally was inundated by shallow seas, and fluctuations in sea level resulted in the deposition or erosion of sediments. The rocks that were deposited on this shallow continental shelf were the result of numerous changes in sea level referred to as transgressions (relative rise in sea level) or regressions (relative drop in sea level or movement of coastlines seaward). Changes in sea level also caused many deposits to be eroded, resulting in (or gaps) in the rock record. The rocks that were deposited from the Cambrian to time period are typical of rocks that originally were deposited in a shallow marine environment. For instance, the Mississippian-age Madison is a massive carbonate that is widespread across Wyoming and is typical of conditions extant during the Paleozoic (Craig et al. 1972).

In the later Paleozoic, the of the represent an influx of sediment due to the uplift of the ancestral and a change to continental deposits in some areas. Erosion from the uplifts resulted in the deposition of the Tensleep and equivalents across the Rocky Mountain region. In the Wyoming PRB study area, Pennsylvanian rocks on the west side of the basin are represented by the Amsden and Tensleep formations (Love et al. 1993). On the east side of the basin, the Tensleep Formation equivalent is the Minnelusa Formation. During the , conditions changed to alternating shallow marine to continental environments as indicated by the , limestone, and anhydrites of the Goose Egg Formation.

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Stratigraphic Units Era System Series West East Quaternary Undifferentiated unconsolidated deposits White River Formation

Moncrief Member

Eocene Wasatch Wasatch Formation Kingsbury Tertiary Formation Member

Tongue River Member Fort Union Lebo Shale Member Formation Tullock Member Lance Formation Lance/ Fox Hills Sandstone Fox Hills Sandstone

Lewis Shale

Teapot Mesaverde Sandstone Member Upper Cretaceous Formation Parkman Sandstone Member

Sussex

Cody Shale Sandstone Member Shannon Sandstone Carlisle Shale Member

Frontier Formation Greenhorn Formation Belle Fourche Shale Muddy Sandstone Newcastle Sandstone Lower Cretaceous Thermopolis Shale Skull Creek Shale Cloverly Formation Fall River Formation Lakota Formation Gypsum Spring Formation Chugwater Group or Formation Goose Egg Formation Permian Goose Egg Formation Minnekahta Limestone

Opeche Shale

Pennsylvanian Minnelusa Amsden Formation Paleozoic Mississippian Madison Limestone Pahasapa Limestone Englewood Limestone No Units No Units Bighorn Dolomite Whitewood Dolomite Winnepeg Formation Gallatin Limestone Cambrian Gros Ventre Formation Deadwood Formation Flathead Sandstone Precambrian Precambrian rocks Source: Love et al. 1993.

Figure 2.1-2 Stratigraphic Chart for the Powder River Basin

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Mesozoic Era. During the beginning of the Mesozoic Era, northeastern Wyoming continued to be dominated by fluctuations of the western margin of . Early Mesozoic rocks of the Triassic System are represented by the Chugwater Group in the western portion of the basin and the Spearfish Formation in the east. The formations are similar and consist of red shale, limestone, sandstone, and gypsum (Watson 1980). During the Triassic, the Wyoming shelf was emergent, and much of the deposits laid down were terrestrial in origin, typified by the and evaporites of the Chugwater Group (Picard 1993).

During middle Mesozoic Era, the Wyoming shelf alternated between emergent and submerged, resulting in Sundance Formation deposits of the Jurassic System. The Sundance Formation rocks are representative of a transgressive-regressive sequence during the middle and . The Sundance Formation consists of sandstone and shale. The Canyon Springs Sandstone Member of the Sundance Formation was deposited during the advance of the sea onto the Wyoming shelf (Picard 1993). The Canyon Springs often consists of a calcareous, oolitic sandstone with well rounded and frosted grains (Watson 1980). Generally, the upper portion of the Sundance Formation has more shale. At the end of the Jurassic, terrestrial conditions predominated resulting in the Morrison Formation, which is characterized by stream deposits that were laid down on an alluvial plain. The Morrison Formation is characterized by shale of various pastel colors (often red, green, and purple) with interbedded sandstone, siltstone, and (Watson 1980).

Rocks from the later part of the Mesozoic Era belong to the Cretaceous System. When describing Cretaceous rocks, they usually are divided into upper and lower Cretaceous. In the lower part of the lower Cretaceous are sandstones that are loosely correlated and referred to as the Lakota Conglomerate and Fall River Sandstone. The Lakota Conglomerate and Fall River are sometimes indistinguishable and make up the Inyan Kara Group. The sandstones occasionally are separated by the Fuson Shale; however, it is often not present (McGookey et al. 1972; Watson 1980). Above the Inyan Kara Group is a black marine shale that in the western portion of the basin is called the Thermopolis Shale and in the east is called the Skull Creek.

During the Cretaceous, a feature known as the developed from the Gulf of Mexico to the Arctic Ocean (McGookey et at. 1972). During the Cretaceous, there were numerous episodes of transgressions and regressions that resulted in the deposition of thousands of feet of . Following the deposition of the Lakota Conglomerate, the first major Cretaceous transgression began resulting in the deposition of the marginal marine Fall River Sandstone then the Thermopolis-Skull Creek Shale. A regression followed that resulted in the deposition of the widespread Muddy Sandstone. In northeastern Wyoming, the Muddy equivalent is referred to locally as the Newcastle Formation.

The upper Cretaceous rocks consist of numerous formations that vary from west to east, indicative of the changing environments spatially and temporally across the basin during upper Cretaceous time. On the west side of the basin above the Muddy Sandstone are the Mowry Shale, , Cody Shale, Mesaverde Formation, Fox Hills Sandstone, and Lance Formation. Above the Muddy-Newcastle Sandstone on the east are the Belle Fourche Shale, Greenhorn Formation, , Niobrara Formation, Pierre Shale, Fox Hills Sandstone, and the Lance Formation (Love et at. 1993). The Mowry Shale is composed of black siliceous shale characterized by numerous bentonite beds (Watson 1980). The Carlile Shale is composed of non-calcareous shale and yellowish sands. The Niobrara Formation is composed of gray to black marine shale. The top of the Niobrara is often composed of limestone or calcareous shale (McGookey et al. 1972).

At the close of the lower Cretaceous, sea level rose and the Mowry Shale was deposited. The Frontier Formation resulted from several transgression-regression cycles and from west to east grades from fluvial to marine (Steidtmann 1993). The near shore and transitional marine deposits of the Frontier Formation in the western portion of the basin grade to the east into the Belle Fourche Shale and , which represent shallow marine conditions. After the Frontier, the Niobrara transgression resulted in the deposition of the marine Carlile, Niobrara, and Pierre Shale sequence

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(McGookey et al. 1972). Following the Niobrara Transgression, a regressive sequence, the Mesaverde Formation, was deposited and is composed of sandstone and shale that were deposited in near-shore and marginal marine environments in western and central Wyoming, including portions of the PRB (Steidtmann 1993). On the east side of the PRB, the Mesaverde equivalent, the Pierre Shale and associated sandstones, are marine in origin. The last major Cretaceous transgression resulted in the deposition of the Lewis Shale. Within the Lewis Shale are sandstones and siltstones that were deposited in marine and transitional marine environments (Van Horn and Shannon 1989). The last Cretaceous unit, the Lance Formation, was deposited under regressive conditions and is composed of sandstones, carbonaceous shale, and coal (Watson 1980).

Cenozoic Era. The earliest Tertiary System rocks (Paleocene Series) are the Fort Union Formation that is composed of sandstone, conglomerate, shale, and coal (Watson 1980). The depositional environments of the Fort Union Formation consisted of fluvial systems with flood plains and peat swamps (Flores et al. 1999). The Fort Union Formation is the major coal-producing unit in the region; the detailed stratigraphy of this unit is discussed in the Coal Resources subsection of Section 2.1.3.3, Mineral Resources. Series rocks in the PRB are represented by the Wasatch Formation, which generally is described as being composed of distinctively colored (pastel green, pink, and yellow) mudstone, sandstone, and siltstone (Watson 1980). The Wasatch Formation also contains numerous coal beds (Flores et al. 1999). There are two distinct members of the Wasatch Formation in the northern portion of the PRB, the Kingsbury Conglomerate and the Moncrief Gravel. The Oligocene Series White River Formation is the youngest of the Tertiary formations in the PRB. The White River is composed of mudstone, sandstone, and conglomerate with volcanic ash beds (Watson 1980).

Near the end of the Cretaceous, mountain building began in western Wyoming. As the mountains were uplifted, erosion occurred and sediment was transported into the shallow Cretaceous seaway. In the PRB, the uppermost Cretaceous unit, the Lance Formation, was derived from alluvial plain deposits marking the end of the Cretaceous (Lilligraven 1993). Also at the end of the Cretaceous and the beginning of Tertiary time, another episode of mountain building was occurring in the area. This episode of mountain building is referred to as the (Lageson and Spearing 1991). Uplift of the Precambrian basement occurred through the movement of Precambrian basement blocks along low- to high-angle reverse faults. This period of mountain building resulted in the mountain ranges that are adjacent to the basin: the Big Horn Mountains, the Laramie Mountains, and the Black Hills. The Hartville Uplift also is of Laramide origin. The uplifted blocks of basement rock were eroded, and the sediment was deposited resulting in the Fort Union and Wasatch formations.

In the later Tertiary (Oligocene-), large volcanic eruptions occurred to the west and north of the area. Prevailing winds carried the ash aloft over an extensive area, and thick layers of ash were deposited as a result of these eruptions. These ash deposits are found in the White River Formation. Erosion along the mountain fronts has removed the mantle Tertiary deposits in most places resulting in abrupt changes in elevation along the mountain fronts.

Unconsolidated Quaternary deposits consist of alluvium, terraces, colluvium, gravels, and pediments (Love and Christiansen 1985). Alluvial deposits generally are associated with alluvial valleys of the major rivers and tributaries.

Structural Geology The PRB is one of a number of structural basins in Wyoming and the Rocky Mountain area that were formed during the Laramide Orogeny. The basin is asymmetric with a structural axis that trends generally northwest to southeast along the western side of the basin (Flores et al. 1999). From the eastern margin of the basin, the rocks dip from 2 to 5 degrees to the structural axis (Figure 2.1-1). From the western edge of the basin, the rocks generally dip approximately 20 to 25 degrees to the axis of the basin. Along the margins of the basin adjacent to the Big Horn Mountains, Laramie Mountains, and the Hartville Uplift are large-scale reverse faults where blocks of the basement-cored uplifts were displaced during the Laramide Orogeny. Other structural elements by which the basin is structurally defined are the

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Black Hills to the east, the Casper Arch on the southwest, and the Miles City Arch on the north in Montana (Figure 2.1-1). These elements are structurally high, but there are no major bounding faults or dislocations. Along the west side of the Black Hills, gently dipping sedimentary rocks ramp onto the Precambrian core of the Black Hills with only minor faults (Grose 1972). The Casper Arch is a broad anticlinal area that trends northwest from the north end of the Laramie Mountains to the Big Horn Mountains. The Miles City Arch is a gentle anticlinal feature that trends northwest from the Black Hills and forms the north structural boundary of the PRB in Montana that separates it from the to the north. In addition to the major structural elements that define the basin, there are a number of folds on the western and southern margins of the basin. Much of the basin has very little internal structure, and the large area of west-dipping rocks east of the basin axis contains few, if any, major folds or dislocations.

Geologic Hazards Earthquakes occur when energy is released as blocks of the earth’s crust move along areas of weakness or faults. There are no identified active faults in the Wyoming PRB study area (USGS 2010). An active fault is a fault that has demonstrated movement within the last 11,000 years. The PRB is located in an area of low risk from ground shaking if a maximum credible earthquake were to occur in the region (Petersen et al. 2008).

Most of the Wyoming PRB study area is underlain by Cretaceous and Paleocene shale, siltstone, and sandstone. These rocks have high clay content and can be very unstable. Geologic formations in the project area that are known to be very susceptible to landslides are the Pierre Shale, Cody , and the Paleocene-age Fort Union Formation (Radbruch-Hall et al. 1980). Landslide occurrence is greatest along the Powder River in Johnson and Sheridan counties and along the Little Powder River north of Gillette (BLM 2003a). Slope instability also can occur in surface mine highwalls.

The PRB Oil and Gas EIS (BLM 2003a) discussed a number of potential hazards that could be associated with CBNG production. The potential hazards discussed were landslides, subsidence, gas seepage, and spontaneous combustion. There was no evidence of the occurrence of any of the aforementioned hazards in relation to CBNG production within the PRB.

2.1.3.3 Mineral Resources Coal Resources Geology and Stratigraphy of the Fort Union Formation. Most of the coal resources of the basin are found in the Fort Union and Wasatch formations. Most of the are in the Paleocene Fort Union Formation. Although coals are present in the Wasatch Formation, they are not as economically important as the coals in the Fort Union Formation. The following is a general description of the stratigraphy of the Fort Union Formation.

The Fort Union Formation and equivalent strata were deposited across a broad area of the Rocky Mountain Region from Northwestern to Montana and western North Dakota. In the PRB, the Fort Union Formation ranges in thickness from over 5,200 feet in the west to 2,300 feet in the east (Curry 1971). The thickest part of the formation is found along the structural axis of the basin (Figure 2.1-1). The Fort Union is divided into three members: from oldest to youngest are the Tullock, Lebo Shale, and Tongue River (Figure 2.1-3). The Tullock Member is up to 740 feet thick and consists of yellow calcareous sandstone and shale and carbonaceous shale beds (Watson 1980). The Lebo Shale Member consists of shale and interbedded sandstone. The Tongue River Member is composed of massive sandstone, shale, and thick coal beds. The coal beds in the Tongue River Member range from a few inches to more than 200 feet thick (Flores et al. 1999).

The Tongue River Member of the Fort Union Formation contains most of the economically important coal zones. The initial understanding of the coal stratigraphy in the PRB was based on the assumption that coal seams in the Tongue River Member were laterally continuous over many miles (Flores and

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Powder River Basin Coal Review Figure 2.1-3

Stratigraphic Column for the Fort Union and Source: Crockett 2010a. Wasatch Formations

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Bader 1999). However, with the advent of more data associated with the large number of drill holes for coal exploration, CBNG, non-CBNG, and oil, the coal stratigraphy is now shown to be more complex (Flores et al. 2010). A number of coal seams have been identified and mapped in the Wyoming portion of the PRB (Figure 2.1-3). As shown in Figure 2.1-3, the coals have been lumped into three zones for this study: Wyodak coals, shallow coals, and deep coals (Crockett 2010a). Coal stratigraphy is complex due to the nature of the environments in which the coal was originally deposited. The swamps (where the organic material that is deposited and eventually becomes coal) associated with the fluvial systems are not often laterally continuous over many miles or aerial extent. Often coals split (one bed becomes several beds), overlap, or end abruptly. It is not possible to detect these discontinuities without the aid of numerous outcrop and borehole sampling points.

Coal Quality. Coal quality for the Wyodak-Anderson coal is shown in Table 2.1-1. The information in Table 2.1-1 was derived from numerous coal samples from the Wyodak-Anderson coal, which has been mined in over 20 mines in the PRB (Stricker and Ellis 1999). As a result, the values in the table provide a general representation of the Wyodak coal. The data indicate that the coal is subbituminous, generally low sulfur, and has low concentrations of metallic constituents. The low sulfur nature of the coal has made it sought after because of its cleaner burning characteristics for power generation. Often utilities will blend PRB coal with higher sulfur coals in order to achieve air quality emissions compliance.

Table 2.1-1 Analytical Results for Coal in the Wyodak-Anderson Coal Zone

Range Number of Variable Samples1 Minimum Maximum Mean

Moisture2 300 14.50 42.30 27.66 Ash2 279 2.86 25.06 6.44 Total sulfur2 279 0.06 2.40 0.48 Calorific value3 277 3,740.00 9,950.00 8,220.00 Sulfur dioxide (pounds)4 277 0.14 7.88 1.24 MMMF Btu5 277 4,580.00 10,560.00 8,820.00 Antimony6 144 <0.01 17.00 0.49 Arsenic6 158 <0.20 19.00 2.60 Beryllium6 151 <0.078 3.30 0.54 Cadmium6 151 <0.007 3.00 0.21 Chromium6 161 <0.59 50.00 6.10 Cobalt6 160 <0.38 27.00 1.90 Lead6 162 <0.50 17.00 3.00 Manganese6 161 0.18 210.00 26.00 Mercury6 162 <0.006 27.00 0.13 Nickel6 161 <0.71 35.00 4.60 Selenium6 151 <0.08 16.00 1.10 Uranium6 157 <0.11 12.00 1.30

1 Samples collected from the Wyodak-Anderson coal zone in the Wyoming and Montana PRB. 2 Values are in percent and on an as-received basis. 3 Value is in British thermal units (Btu). 4 Value is in pounds per million Btu and on an as-received basis. 5 Value is in Btu on a moist, mineral-matter-free (MMMF) basis. 6 Values are in parts per million on a whole-coal and remnant moisture basis. Source: Stricker and Ellis 1999.

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Conventional Oil and Gas Over the past 20 years, conventional oil and gas development in the Wyoming PRB study area has been at a lower rate than CBNG development. Approximately 2,145 conventional wells were drilled from 1990 to 2008. These include 1,105 development oil wells, 693 wildcat (exploration) wells, and 347 service wells of various types (injection, disposal, source water, and observation wells). The only significant discovery has been the African Swallow Field, discovered in 2000, which produced over 1 million barrels of oil and nearly 17.5 billion cubic feet (Bcf) of gas from two wells as of the end of base year 2008 (WOGCC 2010).

As of the end of base year 2008, there were approximately 3,060 productive conventional oil and gas wells in the Wyoming PRB study area and 784 inactive wells (WOGCC 2010). Table 2.1-2 lists the annual production in the Wyoming PRB for the original (2003) and updated (2007 and 2008) base years. The numbers reflect a slow decline in annual production. Figure 2.1-4 shows the location of all wells (producing, non-producing, and plugged and abandoned).

Table 2.1-2 Annual Conventional Oil and Gas Production for Original and Updated Base Years

Annual Oil Production Annual Gas Production Base Year (million barrels) (Bcf) 2003 13.0 41.0 2007 11.4 22.0 2008 10.5 21.2 Sources: AECOM 2011; WOGCC 2010.

CBNG Total CBNG production for 2003 was 346 Bcf, or 88 percent of the total gas production from the basin (AECOM 2009). From 1987 to 2003, the total cumulative gas production from PRB coals was over 1.2 trillion cubic feet (TCF), and the total cumulative water production was approximately 2.3 billion barrels (AECOM 2011). As shown in Figure 2.1-5, annual CBNG production increased rapidly from 1999 through 2002 and started to level off in 2003. Annual water production (Figure 2.1-6) also increased between 1999 and 2002, but started to decrease slightly in 2003. In 2003, the average CBNG production was over 900 million cubic feet per day (MMcfpd). CBNG production appeared to have peaked at 977 MMcfpd in October 2003 (AECOM 2009). Average daily production dropped slightly and leveled off from 2004 to mid-2006. However, as of the end of base year 2008, CBNG production had rebounded and peaked at 548 Bcf, with cumulative gas production at 3.2 TCF and cumulative water production at 5.5 billion barrels (WOGCC 2010). In 2008 there were approximately 20,000 active CBNG wells, with a total annual gas production of approximately 531 Bcf (AECOM 2011).

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R89W R88W R87W R86W R85W R84W R83W R82W R81W R80W R79W R78W R77W R76W R75W R74W R73W R72W R71W R70W R69W T58N Bitter Cr. T58N

Prairie T57N Dog Cr. T57N

SHERIDAN Spotted Horse Cr. T56N Sheridan COUNTY T56N Little Powder River

Clear Cr. Burlington T55N Northern RR. Big Goose Cr. T55N

14/16

T54N Middle Prong T54N Little Goose Cr. 14 Wild Horse Cr. Wild Cat Cr. Cottonwood Cr.

T53N T53N

Wild Horse Cr.

Piney Cr. T52N T52N

Rock Cr. Burlington 16 Northern RR. T51N Crazy Woman Cr. Buffalo T51N

T50N Gillette T50N Powder River

North Fork Crazy Woman Cr.

T49N T49N I-90

T48N T48N Fourmile Cr. CAMPBELL FourHorse Cr.

Trabing Dry Cr. COUNTY T47N Timber Cr. T47N Pumpkin Cr. 59

T46N JOHNSON T46N

South Fork COUNTY T45N Crazy Woman Cr. Belle Fourche River T45N Bacon Cr. I-25 Union

Pacific RR. Red Fork North Fork T44N Powder River Powder River Dry Fork Powder River Black Thunder Cr. T44N Bear Trap Cr. Wright Kaycee T43N T43N Little Middle Fork Thunder Cr. Salt Cr. Buffalo Cr.Powder River Porcupine Cr. T42N T42N 387 T41N T41N South Fork Powder River R85W R84W R83W R82W R81W R80W R79W R78W R77W Antelope Cr. T40N T40N

T39N T39N CONVERSE COUNTY

T38N T38N Dry Cr. Dry Fork Cheyenne River T37N T37N 59

T36N T36N

Sage Cr. T35N T35N

Legend R76W R75W R74W R73W R72W R71W R70W R69W Approximate Coal Mined-out Area through 2008 Former Surface Coal Mine Site Existing and Historic CBNG Wells (as of end of 2008) Existing and Historic Conventional Oil and Gas Wells (as of end of 2008) County WYOMING River or Stream Railroad Powder River Basin River Powder Existing and Historic Existing and Oil and Gas Wells Oil and Gas Coal Review Coal Figure 2.1-4

0 5 10 15 Miles

0 5 10 15 Kilometers Sources: BLM 2003a, 2010a, 2011.

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600

500

400

300

200

Gas (Bcf) (Bcf) Gas 100

0 1985 1990 1995 2000 2005 2010 Year

Source: WOGCC 2010.

Figure 2.1-5 Annual CBNG Production to 2008

800 700

600 500

400

300 200 Water (million barrels) (million Water 100 0

1985 1990 1995 2000 2005 2010 Year

Source: WOGCC 2010.

Figure 2.1-6 Annual CBNG Water Production to 2008

Other Mineral Resources Other mineral resources in the Wyoming PRB study area include , bentonite, aggregates (clinker, sand, and gravel), and leonardite (a form of lignite). Information on these mineral resources in the PRB was based on the BLM’s mineral occurrence and development potential reports (BLM 2004, 2009).

Uranium. Uranium is found in the Wasatch, Fort Union, and Lance formations. It was discovered in the Wyoming PRB study area in 1952 (Love 1952). There are three defined uranium districts in the PRB:

Task 1D Report December 2012 AECOM 2.1-13

Pumpkin Buttes, Southern Powder River, and Kaycee (BLM 2003b). Numerous uranium mining sites were present in these districts, but they were mined out or were not considered economically viable. As of the end of base year 2008, uranium was produced via the in situ leach method in the Southern Powder River district at Smith Ranch and Highland/Morton Ranch (BLM 2009) (Figure 2.1-7). Between 1977 and 2008, approximately 45 million pounds of uranium were mined in the Wyoming PRB study area. As of the end of base year 2008, uranium production in the Wyoming PRB was 1.2 million pounds, all from the Smith Ranch-Highland uranium in situ recovery facility in Converse County (Wyoming Department of Revenue 2010).

Bentonite. In the Wyoming PRB, bentonite is mined in the Kaycee Mining District located in Johnson and Natrona counties. Existing mine permit areas in the Wyoming PRB study area as of the end of base year 2008 are shown in Figure 2.1-7. Bentonite beds occur in the upper Cretaceous Frontier and Mowry formations in an area west and southwest of Kaycee, Wyoming (BLM 2009). As of the end of base year 2008, cumulative production from the district was estimated at 12.0 to 14.0 million tons. Bentonite production from the Kaycee District mines has averaged approximately 354,000 tons per year from 1988 to 2008, for a total of approximately 7.4 million tons. The Johnson County portion of the district within the Wyoming PRB study area has produced over 6.0 million tons during the same time period (Wyoming Department of Revenue 2010).

Aggregates. Clinker is formed when coal beds burn and the adjacent rocks become baked. Clinker is used as road surfacing material and is found in extensive areas in the Wyoming PRB study area (BLM 2003b). Terrace and alluvial deposits associated with the larger streams in the study area are mined for sand and gravel. The more important aggregate mining localities are in Johnson and Sheridan counties (USGS 2003). An estimated 5.7 million tons of aggregate were mined in the study area as of the end of base year 2008 (AECOM 2011).

Leonardite. Leonardite is a form of lignite (low rank coal) that is mined in west-central Converse County. It is used primarily as a drilling fluid additive, although it also is used as a fertilizer. Production for 2008 was 54,162 tons.

2.1.3.4 Paleontological Resources Regulatory Framework Federal legislative protection for paleontological resources stems from the Antiquities Act of 1906 (Public 11 Law [P.L.] 59-209; 16 Code (USC) 431 et seq.; 34 Statute 225), which calls for protection of historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest on federally administered lands. Federal protection for scientifically important paleontological resources would apply to construction or other related project impacts that would occur on federally managed lands. This act provides for funding for mitigation of paleontological resources discovered during federal aid highway projects, provided that “excavated objects and information are to be used for public purposes without private gain to any individual or organization.” In addition to the foregoing, the National Registry of Natural Landmarks provides protection to paleontological resources. The BLM manages paleontological resources () on federal lands under the following statutes and regulations (BLM 2012):

• Federal Land Policy and Management Act of 1976 (FLPMA) (P.L. 94-579); • NEPA (P.L. 91-190); • Title 43 of the Code of Federal Regulations (CFR) regarding collection of , and plant fossils; and • The Paleontological Resources Preservation Act of 2009 (P.L. 111-011). The law authorizes the BLM and FS to manage and provide protection to fossil resources using “scientific principles and expertise.” The act defines paleontological resource as “any fossilized remains, traces, or imprints of organisms, preserved in or on the earth’s crust, that are of paleontological interest and that provide information about the history of life on earth.”

Task 1D Report December 2012 2.1-14 X:\0Projects\BLM_PRB_Phase_II_60143410\Figures\DOC\650_Task_1D_Report\Figure_2_1-7_UraniumBentonite_20120913.mxd

R89W R88W R87W R86W R85W R84W R83W R82W R81W R80W R79W R78W R77W R76W R75W R74W R73W R72W R71W R70W R69W T58N Bitter Cr. T58N

Prairie T57N Dog Cr. T57N

SHERIDAN Spotted Horse Cr. T56N Sheridan COUNTY T56N Little Powder River

Clear Cr. Burlington T55N Northern RR. Big Goose Cr. T55N

14/16

T54N Middle Prong T54N Little Goose Cr. 14 Wild Horse Cr. Wild Cat Cr. Cottonwood Cr.

T53N T53N

Wild Horse Cr.

Piney Cr. T52N T52N

Rock Cr. Burlington 16 Northern RR. T51N Crazy Woman Cr. Buffalo T51N

T50N Gillette T50N Powder River

North Fork Crazy Woman Cr.

T49N T49N I-90

T48N T48N Fourmile Cr. CAMPBELL FourHorse Cr.

Trabing Dry Cr. COUNTY T47N Timber Cr. T47N Pumpkin Cr. 59

T46N JOHNSON T46N

South Fork COUNTY T45N Crazy Woman Cr. Belle Fourche River T45N Bacon Cr. I-25 Union

Pacific RR. Red Fork North Fork T44N Powder River Powder River Dry Fork Powder River Black Thunder Cr. T44N Bear Trap Cr. Wright Kaycee T43N T43N Little Middle Fork Thunder Cr. Salt Cr. Buffalo Cr.Powder River Porcupine Cr. T42N T42N 387 T41N T41N South Fork Powder River R85W R84W R83W R82W R81W R80W R79W R78W R77W Antelope Cr. T40N T40N

T39N T39N CONVERSE COUNTY

T38N T38N Dry Cr. Dry Fork Cheyenne River T37N T37N 59

T36N T36N

Sage Cr. T35N T35N

R76W R75W R74W R73W R72W R71W R70W R69W Legend Approximate Coal Mined-out Area through 2008 Former Surface Coal Mine Site Existing Uranium Recovery Operation Existing Bentonite Mining Permit Areas County WYOMING River or Stream Railroad Powder River Basin River Powder Existing Uranium and Existing Uranium Bentonite Mining Coal Review Coal Figure 2.1-7

0 5 10 15 Miles

0 5 10 15 Kilometers Sources: BLM 2009, 2010a.

9/13/2012 AECOM 2.1-15

In addition to the statutes and regulations listed above, fossils on BLM-administered lands are managed through the use of the following internal BLM guidance and manuals. BLM Manual 8270 (BLM 1998a) and the BLM Handbook H-8270-1 (BLM 1998b) contain the BLM's policy and guidance for the management of paleontological resources on public lands. The manual presents information on the authorities and regulations related to paleontological resources. The handbook gives procedures for permit issuance, requirements for qualified applicants, and information on paleontology and planning. Important guidance in the protection of paleontological resources is contained in BLM Instruction Memorandum (IM) 2009-011, which provides guidelines for the assessment and mitigation of impacts to paleontological resources (BLM 2008b).

Potential Fossil Yield Classification (PFYC) System The BLM has adopted the PFYC system to identify and classify fossil resources on federal lands (BLM 2007). Paleontological resources are closely tied to the geologic units (i.e., formations, members, or beds) that contain them. The probability for finding paleontological resources can be broadly predicted from the geologic units present at or near the surface. Therefore, geologic mapping can be used for assessing the potential for the occurrence of paleontological resources.

The PFYC system is a way of classifying geologic units based on the relative abundance of vertebrate fossils or scientifically significant fossils (plants, , and ) and their sensitivity to adverse impacts. A higher class number indicates higher potential. The PFYC is not intended to be applied to specific paleontological localities or small areas within units. Although significant localities may occasionally occur in a geologic unit, a few widely scattered important fossils or localities do not necessarily indicate a higher class; instead, the relative abundance of significant localities is intended to be the major determinant for the class assignment. The PFYC system is meant to provide baseline guidance for predicting, assessing, and mitigating paleontological resources. The classification should be considered at an intermediate point in the analysis and should be used to assist in determining the need for further mitigation assessment or actions. The BLM intends for the PFYC system to be used as a guideline as opposed to rigorous definitions. Descriptions of the potential fossil yield classes are summarized in Table 2.1-3.

Paleontological Resources in the Study Area There are 45 mapped geologic units in the Wyoming PRB study area (Figure 2.1-8). These units are listed in Table 2.1-4 with the PFYC rankings. Where several units are listed on a single line, the grouping is from the geodatabase files from which the map was compiled. Although some groupings have units with different PFYC ranks, they comprise a relatively small amount of area as compared to the entire study area. For purposes of this report, the various members of the Fort Union Formation have been combined into a single unit since the PFYC ranking does not change from member to member.

As shown in Figure 2.1-8, many of the geologic units outcrop along the margins of the PRB. The most widely distributed units are the Wasatch and Fort Union formations, both of which are discussed below. With the exception of the Lance Formation and Pierre Shale, which are present on the surface in the northeastern corner of the Wyoming PRB study area, the older formations outcrop in the western portion of the basin. In the vicinity of the coal mines and CBNG activity in the eastern portion of the basin, these formations occur at depth. Within the study area, the highly fossiliferous White River Formation (Class 5) occurs only on Pumpkin Buttes in southwestern Campbell County.

The main body of the Wasatch Formation (Class 3a) is the most geographically widespread formation in the Wyoming PRB study area and comprises approximately 57 percent of the surface in the study area. In other basins of Wyoming, the Wasatch Formation is known for abundant fossil resources and its diverse mammalian fauna (BLM 2010b). The Wasatch Formation in the PRB has yielded fewer occurrences of important fossils. The Wasatch Formation also contains , , , and amphibian fossils. Leaf impressions also are common as well as petrified wood, often as fossil logs. While not ranked as high as the main body of the Wasatch Formation as in other basins, the Class 3a rating does

Task 1D Report December 2012 AECOM 2.1-16 not diminish its potential for important fossils. The Class 5 Kingsbury Conglomerate and Moncrief members of the Wasatch Formation, which outcrop in isolated areas along the north-western margin of the study area, have a higher potential for fossil occurrence.

The Fort Union (Class 3) is the second most prevalent formation, covering approximately 35 percent of the surface in the Wyoming PRB study area. It is composed of three members (from stratigraphically lowest to highest): Tullock, Lebo Shale, and Tongue River. The Fort Union Formation contains locally abundant fossil vertebrates, invertebrates, and plants, and displays an important time interval during the early Tertiary evolution of .

Of the energy-related development activities in the Wyoming PRB study area, coal mining and CBNG and conventional oil and gas development have the greatest potential to impact paleontological resources. Recent paleontological surveys conducted in conjunction with coal leasing impact analyses in the eastern Wyoming PRB have resulted in the discovery of numerous fossil localities. The surveys were conducted in proposed lease application areas, and the localities discovered have varying levels of importance (BLM 2010b). Surface coal mining has the potential to impact paleontological resources as a result of direct disturbance to the Wasatch and Fort Union formations. CBNG and conventional oil and gas development also may impact paleontological resources in the Wasatch and Fort Union formations because most of the oil and gas development in the Wyoming PRB study area takes place in areas of bedrock. Oil and gas development in the study area has a greater potential to result in impacts because, although those impacts would be widespread, the total amount of disturbance would be much greater than for coal mining.

Task 1D Report December 2012 AECOM 2.1-17

Table 2.1-3 Summary of Potential Fossil Yield Classifications

Class Description Basis Management Considerations 1 Very Low Potential. Geologic units not likely to contain The probability for impacting any fossils is Management concern for recognizable fossil remains. Rocks such as igneous or negligible. Assessment or mitigation of paleontological resources in Class 1 metamorphic units, (excluding reworked volcanic ash paleontological resources usually is units is usually negligible or not units) and units that are Precambrian in age or older. unnecessary. The occurrence of significant applicable. Assessment or fossils is non-existent or extremely rare. mitigation is usually unnecessary except in very rare or isolated circumstances. 2 Low Potential. Sedimentary geologic units which are not The probability for impacting vertebrate Management concern for likely to contain vertebrate fossils or scientifically important fossils or scientifically significant invertebrate paleontological resources is nonvertebrate fossils. Included in Class 2 are rock units or or plant fossils is low. Assessment or generally low and assessment or geologic deposits having the following characteristics: mitigation of paleontological resources is not mitigation is usually unnecessary Vertebrate or significant invertebrate or plant fossils not likely to be necessary. Localities containing except in rare or isolated present or very rare; units that generally are younger than important resources may exist, but would be circumstances. 10,000 years before present; recent aeolian deposits; and rare and would not influence the sedimentary rocks that exhibit significant physical and classification. These important localities chemical changes (i.e., diagenetic alteration). would be managed on a case-by-case basis.

Task 1D Report December 2012 AECOM 2.1-18

Table 2.1-3 Summary of Potential Fossil Yield Classifications

Class Description Basis Management Considerations 3a, 3b Moderate or Unknown Potential. Fossiliferous sedimentary This classification includes a broad range of Management concern for geologic units where fossil content varies in significance, paleontological potential. It includes geologic paleontological resources is abundance, and predictable occurrence; or sedimentary units of unknown potential, as well as units of moderate or cannot be determined units of unknown fossil potential. Class 3 units include the moderate or infrequent occurrence of from existing data. Management following types of geologic units: significant fossils. Surface-disturbing activities considerations cover a broad range • Often marine in origin with sporadic known may require field assessment to determine of options as well, and could include occurrences of vertebrate fossils. whether significant paleontological resources pre-disturbance surveys, monitoring, occur in the area of a proposed action, and or avoidance. Surface-disturbing • Vertebrate fossils and scientifically significant whether the action could affect the activities will require sufficient invertebrate or plant fossils known to occur paleontological resources. These units may assessment of activities – some intermittently; predictability known to be low. contain areas that would be appropriate to may require field assessment to • Poorly studied and/or poorly documented. Potential designate as hobby collection areas due to determine appropriate course of yield cannot be assigned without ground the higher occurrence of common fossils and action. reconnaissance. a lower concern about affecting significant Class 3a – Moderate Potential. Units are known to contain paleontological resources. vertebrate fossils or scientifically significant nonvertebrate fossils, but these occurrences are widely scattered. Common invertebrate or plant fossils may be found in the area, and opportunities may exist for hobby collecting. The potential for a project to be sited on or impact a significant fossil locality is low, but is somewhat higher for common fossils. Class 3b – Unknown Potential. Units exhibit geologic features and preservational conditions that suggest significant fossils could be present, but little information about the paleontological resources of the unit or the area is known. This may indicate the unit or area is poorly studied, and field surveys may uncover significant finds. The units in this Class may eventually be placed in another Class when sufficient survey and research is performed. The unknown potential of the units in this Class should be carefully considered when developing any mitigation or management actions.

Task 1D Report December 2012 AECOM 2.1-19

Table 2.1-3 Summary of Potential Fossil Yield Classifications

Class Description Basis Management Considerations 4a, b High Potential. Geologic units containing a high The probability for impacting significant Management concern for occurrence of significant fossils. Vertebrate fossils or paleontological resources is moderate to paleontological resources in Class 4 scientifically significant invertebrate or plant fossils are high, and is dependent on the proposed is moderate to high, depending on known to occur and have been documented, but may vary action. Mitigation considerations must include the proposed action. A field survey in occurrence and predictability. Surface disturbing assessment of the disturbance, such as by a qualified paleontologist is often activities may adversely affect paleontological resources in removal or penetration of protective surface needed to assess local conditions. many cases. Class 4 units have the following alluvium or soils, potential for future Management prescriptions for characteristics: accelerated erosion, or increased ease of resource preservation and • Extensive soil or vegetative cover; bedrock exposures access resulting in greater looting potential. If conservation through controlled are limited or not expected to be impacted. impacts to significant fossils can be access or special management anticipated, on-the-ground surveys prior to designation should be considered. • Areas of exposed outcrop are smaller than two authorizing the surface disturbing action will Class 4 and Class 5 units may be contiguous acres. usually be necessary. On-site monitoring or combined as Class 5 for broad • Outcrops form cliffs of sufficient height and slope so spot-checking may be necessary during applications, such as planning that impacts are minimized by topographic conditions. construction activities. efforts or preliminary assessments, • Other characteristics are present that lower the when geologic mapping at an vulnerability of both known and unidentified appropriate scale is not available. paleontological resources. Resource assessment, mitigation, Class 4a – Unit is exposed with little or no soil or and other management vegetative cover. Outcrop areas are extensive with considerations are similar at this exposed bedrock areas often larger than two acres. level of analysis, and impacts and Paleontological resources may be susceptible to adverse alternatives can be addressed at a impacts from surface disturbing actions. Illegal collecting level appropriate to the application. activities may impact some areas. Class 4b – These are areas underlain by geologic units with high potential but have lowered risks of human- caused adverse impacts and/or lowered risk of natural degradation due to moderating circumstances. The bedrock unit has high potential, but a protective layer of soil, thin alluvial material, or other conditions may lessen or prevent potential impacts to the bedrock resulting from the activity.

Task 1D Report December 2012 AECOM 2.1-20

Table 2.1-3 Summary of Potential Fossil Yield Classifications

Class Description Basis Management Considerations 5a, b Very High Potential. Highly fossiliferous geologic units that The probability for impacting significant fossils Management concern for consistently and predictably produce vertebrate fossils or is high. Vertebrate fossils or scientifically paleontological resources in Class 5 scientifically significant invertebrate or plant fossils, and significant invertebrate fossils are known or areas is high to very high. A field that are at risk of human caused adverse impacts or can reasonably be expected to occur in the survey by a qualified paleontologist natural degradation. Class 5 units have the following impacted area. On-the-ground surveys prior is usually necessary prior to surface characteristics: to authorizing any surface disturbing activities disturbing activities or land tenure • Extensive soil or vegetative cover; bedrock exposures will usually be necessary. On-site monitoring adjustments. Mitigation will often be are limited or not expected to be impacted. may be necessary during construction necessary before and/or during activities. these actions. Official designation of • Areas of exposed outcrop are smaller than two areas of avoidance, special interest, contiguous acres. and concern may be appropriate. • Outcrops form cliffs of sufficient height and slope so that impacts are minimized by topographic conditions. • Other characteristics are present that lower the vulnerability of both known and unidentified paleontological resources. Class 5a – Unit is exposed with little or no soil or vegetative cover. Outcrop areas are extensive with exposed bedrock areas often larger than two contiguous acres. Paleontological resources are highly susceptible to adverse impacts from surface disturbing actions. Unit is frequently the focus of illegal collecting activities. Class 5b – These are areas underlain by geologic units with very high potential but have lowered risks of human-caused adverse impacts and/or lowered risk of natural degradation due to moderating circumstances. The bedrock unit has very high potential, but a protective layer of soil, thin alluvial material, or other conditions may lessen or prevent potential impacts to the bedrock resulting from the activity.

Source: BLM 2007.

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R89W R88W R87W R86W R85W R84W R83W R82W R81W R80W R79W R78W R77W R76W R75W R74W R73W R72W R71W R70W Kft Tftr R69W Kc Kl Tfu T58N Tft Tftr Tfu Bitter Cr. Tft Tflt Kl T58N Tfl Tftr Kl Tftr Tflt Prairie T57N Dog Cr. T57N Qa Tftr Tflt Tfl Tftr Tftr Kp Qa Tft SHERIDAN Tftr Kc Spotted Horse Cr. Tfl T56N Tfu Sheridan COUNTY T56N Little PowderTfl River Tfu Tw Tw Clear Cr. Tfl Burlington T55N Tfu Northern RR. Big Goose Cr. Tfl T55N Klm Tft Twk 14/16 Tfl

T54N Twk Tw Tfl Middle Prong T54N Little Goose Cr.Twmo 14 Wild Horse Cr. Tw WVg Wild Cat Cr. Qa Tftl Cottonwood Cr. T53N Tw T53N

Wild Horse Cr. Tftl Piney Cr. T52N Tftl T52N Rock Cr. Burlington 16 Northern RR. T51N Crazy Woman Cr. T51N Tw Qt Qt Buffalo

T50N Gillette T50N Powder River Qa Twk

North Fork Crazy Woman Cr.

T49N Tftl T49N I-90 Tft

T48N Tw Tw Tft T48N Fourmile Cr. FourHorse Cr. O_ PM CAMPBELL

Trabing Dry Cr. COUNTY T47N Tw Timber Cr. Ugn T47N Kc Pumpkin Cr. 59 PM PM Ugn T46N Mm Tfu T46N Mm JOHNSON Mm South Fork COUNTY Qa Crazy Woman Cr. T45N Klm Belle Fourche River T45N Kf Kc Bacon Cr. O_ I-25 Union Qt Pacific RR. Red Fork North Fork T44N Powder River Powder River Dry Fork Powder River Black Thunder Cr. T44N Bear Trap Cr. Kc Kmv Tfl Wright Kmt Kmt T43N Kf Kaycee Tw T43N Kmt Kc Tfl Klm Little Middle Fork Tfl Thunder Cr. Kmv Salt Cr. Buffalo PowderCr. River Porcupine Cr. T42N Tft Kf Tft Tw _r KJ T42N PM Kc Mm Kl 387 T41N Tft @Pcg Kmt T41N South Fork Kf Powder River R85W Tfl R84W R83W R82W R81W R80W R79W R78W R77W Antelope Cr. T40N T40N

T39N T39N CONVERSE COUNTY Tft Legend T38N T38N Approximate Coal Mined-out Kmv - Tfl Dry Cr. Area through 2008 Kp - Pierre Shale Dry Fork Cheyenne River Former Surface Coal Mine Site Kc - Cody Shale T37N T37N Dike Kf - Frontier Formation 59 Fault Kft - Frontier Formation and Mowry and Qs Qa - Alluvium and Colluvium Thermopolis Shales Tfl T36N T36N Qu - Undivided Surficial Deposits Kmt - Mowry and Thermopolis Shales Qls - Landslide Deposits KJ - Cloverly and Morrison Formations Sage Cr. Qs - Dune Sand and Loess KJg - Cloverly, Morrison, Sundance and Tft Gypsum Spring Formations Qt - Gravel, Pediment, and Fan Deposits T35N Kl T35N KJs - Cloverly, Morrison, and Sundance QTg - Terrace Gravel ( and/or ) Formations Qs Qs Tfl Tml - Lower Miocene Rocks, Big Horn Mountains Jsg - Sundance and Gypsum Spring Twr - White River Formation Formations R76W R75W R74W R73W R72W R71W R70W R69W Tw - Wasatch Formation (Main Body) @c - or Group Twk - Wasatch Formation (Kingsbury Conglomerate @Pcg - Chugwater and Goose Egg Formations Member) @Pg - Goose Egg Formation Twmo - Wasatch Formation (Moncrief Member) PM - Ten Sleep Sandstone and Amsden Tfl - Fort Union Formation (Lebo Member) Formation Tflt - Fort Union Formation (Lebo and Tullock Members) Water Tft - Fort Union Formation (Tullock Member) MD - Madison Limestone and Darby Formation Tftl - Fort Union Formation (Tongue River and Mm - Madison Limestone or Group Lebo Members) MO - Madison Limestone and Bighorn Dolomite Tftr - Fort Union Formation (Tongue River Member) Ob - Bighorn Dolomite Tfu - Fort Union Formation (Undivided) O_ - Bighorn Dolomite, Gallatin Limestone, Kfh - Fox Hills Sandstone Gros Ventre Formation, and Flathead Sandstone Kfl - Fox Hills Sandstone and Lewis Shale _r - Gallatin Limestone, Gros Ventre Formation WYOMING Kfb - Fox Hills Sandstone and Bearpaw Shale and Equivalents, and Flathead Sandstone Kl - Lance Formation Ugn - Oldest Gneiss Complex Klm - Lance Formation, Fox Hills Sandstone, WVg - Plutonic Rocks Meeteetse Formation, and Bearpaw and WVsv - Metasedimentary and Metavolcanic Rocks Lewis Shales Powder River Basin River Powder Bedrock Geologic Coal Review Coal Figure 2.1-8 Formations

0 5 10 15 Miles

0 5 10 15 Kilometers Sources: BLM 2010a; Love and Christiansen 1985.

11/27/2012 AECOM 2.1-22

Table 2.1-4 PFYC Ranking of Geologic Units in the Wyoming PRB Study Area

Area Geologic Unit or Deposit (PFYC Rank) (square miles) Alluvium and colluvium (1) 423 Undivided surficial deposits (1) 18 Landslide deposits (1) 8 Dune sand and loess (1) 71 Gravel, pediment, and fan deposits (1) 56 Terrace gravel (1) 1 Lower Miocene rocks, Big Horn Mountains (PFYC not determined) 1 White River Formation (5) 11 Wasatch Formation: main body (3a) 6,997 Wasatch Formation: Kingsbury Conglomerate Member (5) 41 Wasatch Formation: Moncrief Member (5) 18 Fort Union Formation: Lebo Member (3) 1,154 Fort Union Formation: Lebo and Tullock members (3) 64 Fort Union Formation: Tullock member (3) 481 Fort Union Formation: Tongue River and Lebo members (3) 326 Fort Union Formation: Tongue River member (3) 943 Fort Union Formation: undivided (3) 196 Fox Hills Sandstone (3) 8 Fox Hills Sandstone (3) and Lewis Shale (3) 10 Fox Hills Sandstone (3) and Bearpaw Shale (3) 9 Lance Formation (5) 153 Lance Formation (5), Fox Hills Sandstone (3), Meteetse Formation (3), 74 Bearpaw Shale (3), and Lewis Shale (3) Mesaverde Group (3) 71 Pierre Shale (3) 11 Cody Shale (3) 239 Frontier Formation (3) 103 Frontier Formation (3), Mowry Shale (3), and Thermopolis Shale (3) 17 Mowry and Thermopolis shales (3) 81 Cloverly and Morrison formations (5) 31 Cloverly, Morrison, Sundance, and Gypsum Spring formations (5) 15 Cloverly, Morrison, and Sundance formations (5) 2 Sundance (5) and Gypsum Spring formations (3) 31 Chugwater Formation or Group (3) 4 Chugwater Formation (3) and Goose Egg Formation (2) 125 Goose Egg Formation (2) 12

Task 1D Report December 2012 AECOM 2.1-23

Table 2.1-4 PFYC Ranking of Geologic Units in the Wyoming PRB Study Area

Area Geologic Unit or Deposit (PFYC Rank) (square miles) Tensleep Sandstone (2) and Amsden Formation (3) 224 Madison Limestone (3) and Darby Formation (2) 36 Madison Limestone or Group (3) 101 Madison Limestone (3) and Bighorn Dolomite (2) 1 Bighorn Dolomite (2) 1 Bighorn Dolomite (2), Gallatin Limestone (2), Gros Ventre Formation (2), 92 and Flathead Sandstone (2) Gallatin Limestone (2), Gros Ventre Formation (2) and equivalents, and 29 Flathead Sandstone (2) Oldest Gneiss Complex (1) 56 Plutonic Rocks (1) 9 Meta sedimentary and Metavolcanic Rocks (1) 2 Total 12,3581 1 Rivers and creeks in the Wyoming PRB study area comprise approximately 3 acres. Source: BLM 2008a.

Task 1D Report December 2012