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VOLUME 11-A

OCCURRENCE AND CHARACTERISTICS OF

GROUND WATER IN THE BIGHORN BASIN, WYOMING

Robert Libra, Dale Doremus , Craig Goodwin

Project Manager Craig Eisen

Water Resources Research Institute University of Wyoming

Report to

U.S. Environmental Protection Agency Contract Number G 008269-791

Project Officer Paul Osborne

June, 1981 INTRODUCTION

This report is the second of a series of hydrogeologic basin reports that define the occurrence and chemical quality of ground water within Wyoming. Information presented in this report has been obtained from several sources including available U.S. Geological

Survey publications, the Wyoming State Engineer's Office, the Wyoming

Geological Survey, and the Wyoming Oil and Gas Conservation Commission.

The purpose of this report is to provide background information for implementation of the Underground Injection Control Program (UIC).

The UIC program, authorized by the Safe Drinking Water Act (P.L.

93-523), is designed to improve the protection of ground-water resources from possible contamination caused by injection of waste brines, sewage, and other fluids. This report identifies the stratigraphic limits, hydraulic properties, chemical quality, and use of the major water-bearing units within the Bighorn basin, and can therefore be used to assist identification of the aquifers in need of protection. TABLE OF CONTENTS

CHAPTER Page

I . SUMMARY OF FINDINGS ...... I1 . GEOGRAPHIC AND GEOLOGIC SETTING ...... PHYSIOGRAPHY ......

Topography ...... Climate and Surface Drainage ......

HUMAN GEOGWHY ...... Population Distribution ...... Land Use and Ownership ......

GEOLOGY ...... Stratigraphy and Depositional History .... Structure ...... Hydrostratigraphy ......

MAJOR GROUND-WATER USERS ......

Petroleum Industry ...... Agriculture ...... Irrigation ...... Livestock ...... Underground Drinking Water Supplies ..... Private Domestic Use ...... Public Drinking Water Supplies ...... Surface Water Use ...... IV. HYDROGEOLOGY ...... FLATHEAD AQUIFER ...... Hydrologic Properties ...... CHAPTER Page

PALEOZOIC AQUIFER SYSTEM ......

Hydrologic Properties ...... Permeability...... Specific Capacity ...... Transmissivity...... Ground-Water Movement ......

UPPER PALEOZOIC AND LOWER AND MIDDLE MESOZOIC AQUIFERS...... Hydrologic Properties ...... Permeability...... Specific Capacity ...... Transmissivity...... Ground-Water Movement ...... UPPER CRETACEOUS-TERTIARY AQUIFER SYSTEM .... Hydrologic Properties ...... Specific Capacity ...... Ground-Water Movement ...... QUATERNARY AQUIFERS...... Hydrologic Properties ...... Specific Capacity ...... Transmissivities...... Ground-Water Movement ...... V. WATERQUALITY...... GENERAL WATER QUALITY...... Flathead Aquifer...... Paleozoic Aquifer System...... Upper Paleozoic and Lower and Middle Mesozoic Aquifers ...... Upper Cretaceous-Tertiary Aquifer System. .. Quaternary Aquifers ...... Absaroka Volcanics...... CHAPTER Page

DRINKING WATER STANDARDS ...... Primary Standards ...... Fluoride ...... Nitrate ...... Other Primary Standards ...... Secondary Standards ...... Total Dissolved Solids ...... Sulfate ...... Chloride ...... Radionuclear Species ......

VI. REFERENCES ......

APPENDIX A: Non-Municipal and Non-Community Public Drinking Water Supplies ......

APPENDIX B: Geologic Properties of Major Water-Bearing Strata ......

APPENDIX C: Chemical Analyses of Bighorn Basin Ground Waters Sampled by WRRI ......

APPENDIX D: Location and Numbering System ...... LIST OF FIGURES

Page

11-1. Location and drainage map of the Bighorn basin . . 9 11-2. Population map of the Bighorn basin...... 14 11-3, Stratigraphic section of the Bighorn basin .... 17

11-4. Geologic cross sections through the Bighorn basin......

11-5. Major structural features of the Bighorn basin, Wyoming......

11-6. Generalized hydrostratigraphy of the Bighorn basin, Wyoming ......

111-1. Location of public drinking water supplies in the Bighorn basin......

IV-1. Potentiometric surface of the Tensleep aquifer in the Bighorn basin ......

IV-2. Generalized Upper Paleo zoic-Lower Mesozoic stratigraphy of the Bighorn basin......

V-1. Major ion composition of waters from the Paleozoic aquifer system, Bighorn basin, Wyoming......

V-2. Major ion composition of waters from the Phosphoria Formation, Bighorn basin, Wyoming ...

V-3. Major ion composition of waters from the Cloverly Formation, Bighorn basin, Wyoming ....

V-4. Major ion composition of waters from the Frontier Formation, Bighorn basin, Wyoming ....

V-5. Major ion composition of waters from the Upper Cretaceous-Tertiary aquifer system, Bighorn basin, Wyoming ......

V-6. Major ion composition of waters from Quaternary flood plain aquifers, Bighorn basin, Wyoming ... Figure Page

v-7. Major ion composition of waters from Quaternary terrace aquifers, Bighorn basin, Wyoming ..... 95 .

V-8. Location of ground-water fluoride concentrations greater than 2.0 mg/l...... 97

v-9. Variations in fluoride concentrat ions in Lance Formation waters, Manderson, Wyoming ...... 99

V-10. Location of ground-water nitrate concentrations inexcessof10mg/lN03-N ...... 100

vii LIST OF TABLES

Table Page

11-1. Surface drainage in the Bighorn basin...... 11

11-2. Populations of counties and population centers in the Bighorn basin ...... 13 11-3. Land cover in the Bighorn basin...... 16

111-1. Summary of ground-water use, Bighorn basin, Wyoming...... 27

111-2. Number of public drinking water supplies in the Bighorn basin by service category...... 33

111-3. Municipal ground-water supplies in the Bighorn basin...... 36

IV-1. Lithologic and hydrologic characteristics of rock units in the Bighorn basin, Wyoming ...... 41

IV-2. Hydrologic properties of Paleozoic aquifer system, Bighorn basin, Wyoming ...... 51

IV-3. Reported specific capacities of wells in the Paleozoic aquifer system, Bighorn basin, Wyoming . . 53

IV-4. Transmissivities of members of Paleozoic aquifer system, Bighorn basin, Wyoming ...... 55

IV-5. Hydrologic properties of Upper Paleozoic and Lower and Middle Mesozoic aquifers, Bighorn basin, Wyoming ...... 61

IV-6. Reported specific capacity for wells in the Upper Paleozoic and Lower and Middle Mesozoic aquifers, Bighorn basin, Wyoming ...... 65

IV-7. Reported specific capacity of wells in the Willwood aquifer, Upper Cretaceous-Tertiary aquifer system, Bighorn basin, Wyoming ...... 69

IV-8. Reported specific capacity and estimated transmissivity for wells completed in the Quaternary aquifers, Bighorn basin, Wyoming. .... 74 Table Page

V-1. Concentration ranges for sulfate, chloride, and total dissolved solids in ground waters from the Bighorn basin, Wyoming...... 102

V-2. Concentrations of radionuclear species in ground waters from the Bighorn basin, Wyoming ...... 105 Plate

1. Structural contour map of the Bighorn basin.

2. Permitted domestic wells in the Bighorn basin.

3. Total dissolved solids map of the Paleozoic aquifer system, Bighorn basin.

4. Total dissolved solids map of the Upper Cretaceous- Tertiary aquifer system, Bighorn basin.

5. Total dissolved solids map of the Quaternary aquifers, Bighorn basin.

'plates contained in Volume 11-B. I. SUMMARY OF FINDINGS I. SUMMARY OF FINDINGS

1. Two major bedrock aquifer systems have been identified within the Bighorn basin. These are the Paleozoic and Upper Cretaceous-

Tertiary aquifer systems. Additionally, several dispersed, hydrologically isolated water-bearing units have been distinguished including the basal Cambrian sandstone, several sandstone and carbonate units within the Upper Paleozoic through Middle Mesozoic sequence, and unconsolidated deposits of Quaternary age. Aquifer recharge rates, ground-water flow paths, the extent of interformational mixing, and historic water level fluctuations are poorly known. Data concerning hydrologic properties are sparse, especially for pre-Tertiary

strata in the central basin.

2. On the basis of available hydrologic and hydrochemical data, the Paleozoic aquifer system (Ordovician through Pennsylvanian

strata) has excellent potential for producing large quantities of good quality water. The Pennsylvanian Tensleep Sandstone and

Mississippian Madison Limestone are the most extensively exploited aquifers, mainly for secondary oil recovery, irrigation, and municipal uses. Declines in potentiometric elevations along the east flank of the Bighorn basin have been identified for the Madison Limestone.

Available data on the Tensleep Sandstone indicate it generally has the highest permeabilities within the system, although they decrease with increased burial depth. Madison Limestone hydrologic data are sparse; available information indicates somewhat poorer water production capabilities than the Tensleep, although areas with secondary permeability produce high yields. Areas of intense

fracturing produce the highest yields in all Paleozoic aquifers.

Consequently, site specific studies are needed before any large-

scale development of these aquifers can be considered.

Recharge to the Paleozoic aquifer system is considered to occur

primarily within outcrop areas, through direct infiltration of precig-

itation and surface water. Deep burial and thick overlying shales

produce highly artesian conditions away from the basin margins,

Generally, the Paleozoic aquifer system waters contain less

than 1,000 mg/l TDS (total dissolved solids) in the area east of

the Bighorn River. Deep basin waters typically have TDS concentra-

tions in excess of 3,000 mg/l and are associated with increased

levels of sodium, sulfate, and chloride. Low-TDS waters may occur

in this system along the west flank of the basin, but substantiating

data are lacking. Fluoride concentrations exceeded 2 mg/l F in

one-third of the tested wells in this system.

2. Where present, Quaternary aquifers yield the largest quantities

of ground water within the basin. The unconsolidated sediments

of these alluvial terrace and flood plain deposits have transmissivites

to 80,000 gpd/ft and specific capacities as high as 70 gpm/ft. Develop-

ment of the system for drinking water, irrigation, and stock uses

has been extensive, and large yields and shallow drilling depths

allow for a relatively inexpensive water source. Additional develop-

ment potential of the aquifers may be limited locally by existing use,

Recharge to Quaternary aquifers takes place through direct

infiltration of precipitation, streamflow loss, upward leakage from

underlying bedrock units, and from excess irrigation waters, which

have created artificial aquifers in places. Quaternary waters generally contain over 500 mg/l TDS, though less mineralized waters are found along the upper reaches of these valley aquifers. Locally, nitrate concentrations may be objectionably high.

4. Formations comprising the Upper Cretaceous-Tertiary aquifer system, the Mesaverde, Meeteetse, Lance, Fort Union, and Willwood formations, are characterized by large variations in both the quantity and quality of water produced due to sporadically changing lithologies.

Hydrologic data are sparse, but reported specific capacities generally are from 5 to 20 gpm/ft drawdown. TDS ranges from 250 mg/l to 4,500 mg/l and most values exceed 1,000 mg/l. Major ion composition is variable. Objectionably high levels of fluoride may be present.

However, the shallowness and wide geographic extent of this aquifer system allows for an easily exploitable ground-water resource throughout much of the basin. Because the quality and quantity of water vary both locally and regionally, site specific investigations are needed prior to development.

Recharge to the Upper Cretaceous-Tertiary aquifer system is through both outcrop infiltration and downward leakage from overlying strata.

5. The Cambrian Flathead Sandstone aquifer, at the base of the Paleozoic sedimentary sequence, contains good quality water

(<500 mg/l TDS) under high artesian pressure. Deep burial and the presence of highly productive overlying aquifers have limited current development of this unit.

Minor water-bearing formations ranging in age from Late Paleozoic to Late Cretaceous, the most important of which are the Phosphoria, Cloverly, and Frontier formations, yield small quantities of marginal to poor quality water. TDS varies from 1,000 mg/l to over 10,000 mg/l. Development is generally restricted to outcrop areas, where more desirable water-bearing units are absent or deeply buried.

6. Constituents that exceed U.S. Environmental Protection

Agency primary drinking water standards include fluoride, nitrate, and in a few instances selenium, mercury, and chromium. High (>ZOO mg/l) fluoride concentrations are common in waters of the Upper

Cretaceous-Tertiary and Paleozoic aquifer systems. High nitrate concentrations (>lo mg/l NO3 -N) are found mainly in Quaternary aquifer ground waters that are associated with agricultural activities.

The above aquifers are extensively utilized for drinking water supplies.

The secondary standards for sulfate (250 mg/l SO =) and TDS 4 (500 mg/l) are exceeded throughout much of the basin in all water- bearing units. Waters with less than 500 mg/l TDS are generally restricted to the Paleozoic aquifer system near the basin flanks and to Quaternary deposits in upstream areas. Although recommended standards are exceeded, the highly mineralized waters of the basin are used by many of its residents.

7. An accurate tabulation of ground-water use by economic sector and source aquifer is impossible until more actual withdrawal data are available. Current estimates indicate that ground water supplies between 4 and 9 percent (30,800 to 74,900 acre-feetlyear) of the water used in the basin.

8. The petroleum industry is the largest user of ground water within the basin, and withdraws between 13,400 and 56,000 acre-feetlyear, based on various estimates from differing sources. Withdrawals include both fresh water from sources developed specifically for secondary recovery purposes and by-product water produced during primary and secondary oil recovery. The Madison through Phosphoria sequence provides most of the water used for injection. Principal injected formations include the Amsden, Tensleep, Phosphoria, and

Frontier.

9. Agricultural activities use about 12,900 acre-feet of ground water per year. Irrigation ground water is supplied mainly by

Quaternary aquifers in the central basin and by the Paleozoic aquifer system along the east basin flank. Water for livestock consumption is obtained from virtually all formations, generally from the shallowest unit that provides a sufficient yield.

10, Human consumption of ground water is about 4,500 acre-feet/ year. Municipal systems are supplied primarily by Quaternary aquifers and the Madison Limestone aquifer (Paleozoic aquifer system).

Quaternary aquifers and the Upper Cretaceous-Tertiary aquifer system provide the majority of non-municipal public drinking water and private supplies. Ground waters from virtually all formations are developed locally for domestic water use. 11. GEOGRAPHIC AND GEOLOGIC

SETTING 11. GEOGRAPHIC AND GEOLOGIC

SETTING

PHYSIOGRAPHY

The Bighorn basin covers a roughly elliptical, northwest trending area of about 12,500 square miles. The basin includes all of Big

Horn, Hot Springs, and Washakie counties, the portion of Park County lying outside of Yellowstone National Park, and small portions of

Fremont and Sheridan counties. The basin is bounded on the east by the Bighorn Mountains, on the south by the Owl Creek and Bridger mountains, and on the northeast by the Beartooth Mountains. The western extent of the basin is uncertain, because the basin margin is covered by the volcanic Absaroka Mountains, and therefore is arbitrarily placed at the east boundary of Yellowstone National

Park. To the north, the basin is open into Montana. East-west distance across the basin is about 140 miles, while north-south distance, to the state line, is roughly 100 miles (Figure 11-1).

Topography

The topography within the central Bighorn basin is typified by rolling plains broken by broad river valleys, narrow terraces, and badlands. Elevations in the central plains are generally from

4,000 to 5,600 feet above sea level. The lowest elevation within the basin is about 3,500 feet, where the Bighorn River crosses the

Wyoming-Montana state line. The bounding mountains rise steeply t'a the east and west from the central plains and more gently to the WYOMING

Figure 11-1. Location and drainage map of the Bighorn basin. south. Elevations in the surrounding mountains commonly exceed

10,000 feet, reaching a maximum of 13,175 feet at the top of Cloud

Peak in the Bighorn Mountains. Total basin topographic relief,

therefore, is about 9,675 feet.

Climate and Surface Drainage

The climate of the Bighorn basin varies, primarily as a function of altitude, from a cool, dry desert to a cool, humid alpine type.

Much of the central lowland receives less than about six inches of precipitation a year, while in the surrounding mountains precipitation of over 70 inches a year can be expected. The mountainous regions receive the greatest part of their precipitation during the winter as snowfall, and the central plains receive their greatest precipitation during occasional spring and summer thunderstorms.

Most streamflow from perennial streams is the result of snowrnelt in the high mountains. Ephemeral streams in the central part of the basin flow only in response to thunderstorms and contribute an insignificant amount of the basin's overall streamflow. Major streams within the Bighorn basin are listed in Table 11-1 and are shown in Figure 11-1.

HUMAN GEOGRAPHY

Population Distribution

All large communities within the Bighorn basin are located within a few miles of a major stream or river. Worland, Thermopolis,

Basin, and Greybull developed along the Bighorn River, and Cody,

Powell, and Love11 are centered near the Shoshone River. Only a

few settlements have been located where there is no nearby supply TABLE 11-1

SURFACE DRAINAGE IN THE BIGHORN BASIN

Clarks Fork Yellowstone River Sunlight Creek Pat O'Hara Creek Big Sand Coulee Bighorn River Owl Creek Kirky Creek Cottonwood Creek Gooseberry Creek No Water Creek Fifteen Mile Creek Nowood River Tensleep Creek Paint Rock Creek Greybull River Wood River Dry Creek Shell Creek Shoshone River North Fork South Fork of surface water. These communities are usually associated with

areas of nearby mineral development.

The population of the four-county Bighorn basin area was about

40,000 in 1970, having decreased about 4,000 during the 1960's.

It is expected that the 1980 Census will show a population increase,

and growth is expected to continue in this region beyond the end of the century (U.S. Department of Agriculture, 1974). Growth will not be an overwhelming phenomenon, as in much of Wyoming, since

the Bighorn basin does not have the immense mineral resources found

in other parts of the state. One trend apparent in the basin, as

in much of Wyoming, is the movement of the population from rural

areas to the towns and cities. This urbanization is expected to

continue .

Population data for towns and counties of the Bighorn basin are presented in Table 11-2, and a map showing the locations of population centers is given in Figure 11-2.

Land Use and Ownership

Land use in the Bighorn basin varies primarily as a function

of precipitation. Within the high mountainous areas, the alpine environment is presently used only for recreational purposes. At lower elevations thick forested areas exist and silviculture is practiced. Grasslands along the mountain fronts and streams are used for grazing. Less than 5 percent of the basin area is cropland, much of which is located along the major streams where irrigation with surface water is possible. Most of the basin, and essentially 100 percent of the central lowland area, is either barren or brush-covered. Limited use of this land is made for livestock TABLE 11-2 POPULATIONS OF COUNTIES AND POPULATION CENTERS IN THE BIGHORN BASIN

County /Population Center 1979 (est.12 Big Horn Hot Springs Park Washakie

Total

Basin Burlington Byron Cody Cowley Deaver Emblem Frannie Grass Creek Greybull Hamilton Dome Hyattville Kirby Love11 Manderson Meeteetse Otto Powell Rals ton Shell Tensleep Thermopolis E. Thermopolis Worland Total 26,601

'u. S. Census Data summarized in U. S. Department of Agriculture, 1974. 2~yomingDepartment of Economic Planning and Development, 1980. WASHAKIE NGS -

ast Thermopolis !L--

larger than 8000 I el i

1000 to 4000 500 to 1000 POPULATION OF BIGHORN BASIN 100 to 500 tO to -100 (&d

Figure 11-2. Population map of the Bighorn basin. grazing. Table 11-3 lists the percentages of the various land types found within the basin.

Slightly over two-thirds of the land within the Bighorn basin

is under federal jurisdiction. The U.S. Bureau of Land Management

has control over most of the central-basin lands, while the U.S.

Forest Service manages most of the mountainous areas. Privately

owned land (about 24 percent of the land area in the basin) is con-

centrated along rivers and streams.

GEOLOGY

Stratigraphy and Depositional History

Up to 33,000 feet of stratigraphic thickness have been measured

in the Bighorn basin. A generalized stratigraphy is presented in

Figure 11-3.

Paleozoic age rocks, comprising about 4,000 feet of the strati-

graphic record, reflect a marine transgressive/regressive depositional

environment. Marine limestones and dolomites are the dominant lithol-

ogy of the Paleozoic sequence. Much less profuse are sandstones and

shales, which represent beach and nearshore conditions of deposition.

The early Mesozoic era was characterized by shallow seas that deposited the sandstones of the Chugwater, Gypsum Springs, and Sun- dance formations. A transition to a terrestrial environment occurred during the Jurassic, resulting in fluvial and paludal sandstones and shales. During the Cretaceous period thousands of feet of interbedded sandstones and thick shales were deposited under shallow marine and deltaic conditions.

Late Cretaceous time marked the beginning of the Laramide orogeny.

The Lance Formation represents the retreat of the Cretaceous seas TABLE 11-3

LAND COVER IN THE BIGHORN BASIN (U.S.D.A., 1974)

Land Type Percent of Basin

Alpine 0.57

Barren, Brush 59.65

Grass land 20.24

Forested 14.85

Cropland 4.26

0 ther 0.43 Rcecnt 6 Plei~tocene

Pliocene

Miocene

Oligocene

Eocene

y Paleocene For t Union----=--

Cretaceous

Jurassic

SAN0910W CONOLOUERATE GIPSllM SHALE ,CLAYSTONE ** . BtNTONITt LIMESTONE OO;.OUITL - :::COAL: VOCtUJIC FLOWS BRLCCIAS

Figure 11-3. Stratigraphic section of the Bighorn basin. (From Wyoming Geological Association, 1973). and the beginning of the terrestrial environments characterizing the Tertiary period. Mountains surrounding the Bighorn basin, uplifted by compressional forces, provided a source for the more than

10,000 feet of Tertiary sediments. These deposits are comprised of conglomerates, sandstones, and shales that were deposited in fan, fluvial, or lacustrine environments. During mid-Tertiary time several thousand feet of volcanics were emplaced in the western part of the basin. General upwarping of the basin during the late

Tertiary resulted in removal of portions of many Tertiary deposits.

The youngest units within the basin are Pliocene and Quaternary terrace deposits and Recent alluvial deposits. Age and occurrence of these deposits have been correlated with glacial and interglacial conditions (Mackin, 1937). These unconsolidated deposits may be up to several hundred feet thick locally.

Structure

The Bighorn basin is an asymmetric syncline between the Bighorn

Mountains on the east and the Absaroka and Beartooth mountains on the west. The synclinal axis is offset west of the basin center and trends generally northwest (Plate 1). Several cross sections are shown in Figure 11-4. The basin is rimmed by compressional uplifts of

Precambrian granite cores mantled by a cover of moderately to steeply dipping sedimentary beds. The western margin is covered by the

Absaroka volcanics, but it is suspected that the basin structure con- tinues under these deposits far into the Yellowstone Park region

(Thorn, 1952).

Along the margins of the basin numerous anticlinal structures are present as shown in Figure 11-5. These structures often exhibit LEGEND KJcm Cloverly and M~rrisonFormations Kft Frontier Formation p6r Igneous and Metamorphic Rocks Kc Cody Shale 06bf Bighorn, Gallatin, Gros Ventre, Knm Mesaverde Formation and Flathead Formations Klm Lance and Meetteetse Formations MDmj Madison, Jefferson, and Three Tfu Ft. Union Formations Forks Formations Tw Willwood Formation PMta Tensleep and Amsden Formations Tv Tertiary Volcanics Pp Phosphoria Formation TRpu-TRcd Chugwater, Dinwood-Goose Egg Formations Jsg Sundance and Gypsum Springs Formations

8x0' 6000' ~OoO' 2000' SEA LEVEL 2000'

SEA

-8000' -BoOO' - *oaa' - 2000' - SEA LEVEL - XwX)'

Figure II-4. Geol~giccross sections through the Bighorn Basin. Vertical exageration =2x. (After Lowry et al. , 1976) . f

PAR K \ 1 BIG HORN

WASHAKIE

EXPL ANAT/ON

Anticline Syncline 7 Anticline Exposing Paleozoic Rocks U - Major Fault MaJor Thrust Fault - Precambrian Rocks Exposed pm1 0c 10 20 30 Miles Figure 11-5. Major structural features of the Bighorn basin, Wyoming. 1 - Bighorn Mt. uplift; 2 - Owl Creek uplift; 3 - Beartooth uplift; 4 - Synclinal axis of the Bighorn basin; 5 - Little Sheep Mt. anticline ; 6 - Sheep Mt. anticline; 7 - Thermopolis/~armSprings anticline; 8 - Rattlesnake Mt. anticline. associated faulting and fracturing, which increase the permeability of the deformed rocks and decrease the efficiency of confining beds to act as flow barriers, allowing for interformational fluid movement (Stone, 1967). Where these structures are eroded and older strata exposed, discharge may occur through fracture and solution zones from deeper aquifers within the basin.

Hydrostratigraphy

Stratigraphically adjacent water-bearing units which have reason- ably consistent areal extent, hydrologic properties, and recharge/ discharge mechanisms, and which are not separated regionally by thick confining beds, have been defined as integrated aquifer systems.

These are the Paleozoic and Upper Cretaceous-Tertiary aquifer systems, each comprised of several discrete member aquifers. This grouping of hydrostratigraphic units aids in the regional analysis of ground- water movement, quality, and other hydrologic properties.

The degree of hydrologic connection between member aquifers may vary due to the presence or absence of local confining beds and/or fracture zones. Therefore, differences in hydrologic properties and water quality may exist between member aquifers, resulting in the occasional need to discuss individual aquifer properties separately.

The Paleozoic aquifer system consists of Ordovician through

Pennsylvanian age sandstone and carbonate strata (Figure 11-6).

This rock sequence is underlain by the thick, relatively impermeable shales of the Cambrian Gallatin and Gros Ventre formations, and is overlain by intertonguing siltstone, shale, and limestone facies of the Permian Phosphoria Formation, which act as local confining beds. Major water-bearing units are interbedded with less permeable SYSTEM GEOLOGIC AGE1 LITHOLOGY I FORMATION

Lance Formation - .-fining .=ds 1 ~~~~oNnNuous -;:: .:., 1:-. ::.;:m::

' . ,,.-.._Y - .",. . 0. *. 11 .. --. , . ._._. p:;:.- , * - Meesteetse For motion - Confining Beds/ DISCONTINUOUS AQUIFERS -

Mesiaverde Formation - Confining Beds/ Dl SCONTINUOUS AQUIFERS

Cretaceous

I=- I=- Cody Shale - REGIONAL AQUITARD

-- .:...... ;:.: ...... ,. '.'... ..' ...... -...... ;f. :...... &... $,..-::.:: Frontier Formation - MINOR AQUIFER - --- Mowry Shale- AQUl TARO -- - -,; '.'.:,'~.~-:'.:~:~.... .x...... '*.. ...:...... & --- Thermopolis Shale - AQUITAR D b."". .'.' ...... :...... ;.;..:.,...... Cleverly Formation - MINOR AQUIFER orrison Formation- Local Confining Bed/MINOR AQUIFER ndance Formation - Local Confining Bed/ MINOR AQUl FER psum Springs Formation- Local Confining Bed/ MINOR AQUIFER

water Formation - Local Confining Bed/ M INOR AQUl FER oody Formation- Local Confining Bed/M I NOR AQUl FER phoria Formation - Local Confining Bed/ MINOR AQUIFER sleep Sondstone- MAJOR AQU l FER sden Formation- MINOR AQUIFER

adison Limestone - MAJOR AQUIFER ree Forks / Jefferson Formations-Local Confining Bed/ MI NOR AQUIFER qhorn Dolomite - MAJOR AQUIFER

Ilatin /Gros Ventre Formations - REGIONAL AQUITARD

Figure 11-6. Generalized hydrostratigraphy of the Bighorn basin, Wyoming. strata that act as confining beds locally, restricting hydrologic connection between the major aquifers except in areas with extensive structural deformation.

The Upper Cretaceous-Tertiary aquifer system includes all bedrock units lying stratigraphically above the Cretaceous Cody Shale, a regional confining bed consisting of a thick series of relatively impermeable shales (Figure 11-6) . Major water-bearing units are lenticular, discontinuous sandstone bodies that are hydrologically isolated to varying degrees by intervening siltstones and claystones.

The intertonguing and discontinuous nature of major water-bearing units prevents the identification of regionally extensive productive horizons,

In addition to the two major aquifer systems, several dispersed, hydrologically isolated bedrock aquifers exist within the basin.

These include the basal Cambrian Flathead Sandstone, carbonate facies of the Permian Phosphoria Formation, and sandstone units of the

Lower Cretaceous Cloverly and the Upper Cretaceous Frontier formations.

The Tertiary Absaroka volcanics also represent a potential, but currently undeveloped, ground-water source. Where present, unconsolidated Quaternary terrace and flood plain deposits constitute important aquifers within the basin.

24 111. GROUND-WATER USE 111. GROUND-WATER USE

It is impossible to quantify with precision ground-water use within the Bighorn basin due to a lack of pertinent withdrawal data for all economic sectors. On the basis of various estimates for each sector, ground-water use ranges from 30,800 to 74,900 acre- feet/year, or 4 to 9 percent of the basin's total annual water demand, with the remainder being satisfied by surface water. The range in estimated total ground-water use is due to uncertainties in the amount of ground water withdrawn by the petroleum industry.

As this report is concerned with ground water, a sector by sector breakdown of surface water use is not included. However, as surface water supplies the majority of the basin's water needs, a short discussion of the current magnitude and future potential of surface water resources is included at the end of this chapter.

The Paleozoic aquifer system and Quaternary alluvial aquifers supply most of the ground water withdrawn within the basin, although virtually all water-bearing strata are exploited locally. The major uses of ground water within the basin are petroleum recovery enhance- ment, agricultural activities, and drinking water supplies (Table

111-1) .

Ground-water withdrawals by the petroleum industry range from

13,400 to 56,000 acre-feet/year, based on estimates from various sources. Petroleum-related withdrawals include fresh water developed solely for secondary recovery purposes and produced water withdrawn during primary and secondary oil recovery. TABLE 111-1

SUMMARY OF GROUND-WATER USE, BIGHORN BASIN, WYOMING

Estimated Annual Withdrawals Sector (acre-feet) Major Sources

Petroleum Industry Madison, Tensleep, and Phosphor ia aquifers

Agriculture Quaternary aquifers, Paleozoic aquifer system

Quaternary aquifers, Paleozoic aquifer system

--Stock Water All water-bearing formations

Underground Drinking Water Quaternary aquifers

--Private Domestic Supplies Quaternary aquifers, Upper Cretaceous/Tertiary aquifer system

-- Public Supplies Quaternary aquifers, Madison aquifer Agriculture withdraws roughly 12,900 acre-feet of ground water annually. Approximately two-thirds is utilized for irrigation, with the remainder used for stock watering.

Drinking water supplied from underground sources totals about

4,500 acre-feetlyear. Nine municipal water systems, five non-municipal community water systems, and the majority of all other public and private water supplies utilize ground water.

MAJOR GROUND-WATER USERS

Petroleum Industry

Ground-water withdrawals by the petroleum industry fall into two major categories--fresh water, which is developed solely for use in the secondary recovery of crude oil; and produced water, which is withdrawn as a byproduct of primary and secondary oil recovery. An unknown percentage of the produced water is reinjected for secondary recovery purposes while the remainder, depending upon quality, is injected through disposal wells, discharged into evaporation ponds and streams, or used for agricultural purposes.

Estimates of petroleum ground-water withdrawals vary greatly. An estimated total of 50,000 acre-feet were withdrawn in 1967, with about half of this water reinjected for secondary recovery (Wyoming Water

Planning Program, 1972). The U.S. Geological Survey estimated total withdrawals of 56,000 acre-feet in 1970 (Lowry et al., 1976). However, figures for 1978 showed that produced water withdrawals were only about 8,400 acre-feet (Donald Basko, Wyoming Oil and Gas Commission, personal communication, 1981). Information concerning fresh-water withdrawals is incomplete, but fields for which data are available indicate average annual water use of about 5,000 acre-feet for the mid-1970's (Collentine et a1., 1981). This value, combined with 1978 produced water withdrawals, indicates a petroleum ground-water use of only 13,400 acre-feetlyear. Incomplete data on fresh-water production may account for some of the discrepancy between this figure and earlier estimates.

Production of oil by injection methods is principally from formations of Upper Paleozoic age--the Amsden, Tensleep, and Phosphoria formations. Limited secondary oil recovery from Mesozoic formations, including the Chugwater, Morrison-Cloverly, and Frontier, also takes place within the basin. Water produced for injection comes primarily from the Madison and Tensleep aquifers of the Paleozoic aquifer system, as well as the Phosphoria aquifer. Lesser amounts are produced from the Bighorn Dolomite, Frontier, Muddy, Mesaverde, and Jefferson-

Three Forks aquifers.

Future projections of oil production within the Bighorn basin cannot be made reliably. Much oil remains to be produced by secondary and tertiary recovery methods, but economics will play a major role in whether or not this oil is produced. It seems likely that with rising prices oil production in the basin, especially the percentage produced by secondary recovery methods, will continue to grow, as will petroleum industry water consumption.

Agriculture

Agriculture is the second largest ground-water user in the

Bighorn basin. The principal use of ground water is for cropland irrigation with a secondary use for stock watering. Irrigation

Irrigation of about 5,850 acres with ground water is permitted within the basin (U.S. Department of Agriculture, 1974; U.S. Soil

Conservation Service, Casper, Information Files, 1981). However, the percentage of this acreage that is irrigated in any given year is uncertain. Studies of specific areas within the basin have shown that only 40 to 58 percent of the permitted irrigable acreage is actually irrigated, while the statewide average is about 50 percent

(M. O'Grady, Wyoming Water Development Commission, personal communication, 1981). Comparison of total (ground water plus surface water) permitted irrigable acreage within the basin to the amount actually irrigated in 1978 (Wyoming Crop and Livestock Reporting Service,

1979) shows that 70 percent of the acreage received irrigation water.

Assuming annual ground-water irrigation applications are propor- tionate to total irrigation water applications, about 4,095 acres are irrigated with ground water in any given year. Basinwide, about

2.1 feet of irrigation water is needed to meet average crop consumptive use demands (Trelease et al., 1970), requiring an estimated 8,600 acre-feetlyear of ground water. This compares to an estimate of

10,080 acre-feetlyear, derived from irrigation well power consumption records and production capacities, for the principal areas of ground water irrigation along the Greybull River and in the Tensleep-

Hyattville area (Lowry et al., 1976).

Near the west flank of the Bighorn Mountains ground water from the Paleozoic aquifer system is under artesian pressure and has been developed for irrigation. Along stream channels (such as the

Greybull River) Quaternary alluvial or terrace aquifers are tapped for irrigation. The amount of irrigable land in the Bighorn basin is roughly double that presently irrigated and projections are that much of this land will be put into production in the future (U.S. Department of Agriculture, 1974). It is expected that most increases in irrigated land will be through surface-water development, with ground water playing a less critical role (Wyoming Water Planning Program,

1972), although pending litigation concerning surface water rights and interstate compacts make future development projects difficult.

Livestock

Stock consumptive use of ground water in the Bighorn-Wind River drainage basin has been estimated at 6,400 acre-feet/year (Wyoming

Water Planning Program, 1972). Based upon cattle and sheep populations

(Wyoming Crop and Livestock Reporting Service, 1979), about two-thirds of this amount, or 4,300 acre-feetiyear, is used within the Bighorn basin. Stock wells are usually drilled until sufficient water yield

is obtained. Therefore, depending on location, almost every water- bearing formation is used for stock watering purposes.

Underground Drinking Water Supplies

Private Domestic Use

Of the total 1970 population in the Bighorn basin, about one- third, or about 13,000, were not living within communities. These people are served almost entirely by ground water in the form of family or multifamily wells. Assuming consumption of 180 gallons per capita per day, private domestic use in the basin is estimated at roughly 2,600 acre-feetiyear. Domestic wells are usually drilled until sufficient amounts of relatively good quality water are obtained. Therefore, almost every aquifer is used somewhere in the basin as a domestic water source.

Records of the Wyoming State Engineer indicate that there were

3,052 permitted domestic wells completed in the Bighorn basin through

1979. The number of wells completed in each aquifer reflects both

settlement patterns and areal extent of the various aquifers within the basin (Plate 2). Fifty-seven percent of the domestic wells are completed in either Quaternary alluvial or terrace deposits.

The next largest grouping, 33 percent, includes wells completed

in the Upper Cretaceous-Tertiary aquifer system. Only 8.5 percent of the domestic wells are completed in Upper Paleozoic and Lower and Middle Mesozoic aquifers, and less than two percent withdraw water from the Paleozoic aquifer system.

Public Drinking Water Supplies

Public drinking water supplies within the Bighorn basin include both community supplies, which serve a permanent population of over

25, and non-community supplies, which serve a permanent population of less than 25 but average over 25 transient residents daily. Com- munity supplies include ten municipal systems and five non-municipal supplies that support individual subdivisions or mobile home courts.

There are 61 non-community public water supplies serviced by ground water within the basin (U.S. Environmental Protection Agency, Denver,

Information Files, 1977). These include motels, service stations, restaurants, lodges, dude ranches, campgrounds, schools, ski resorts, etc. Table 111-2 lists the types of public water supplies within the Bighorn basin. Figure 111-1 locates all these systems. TABLE 111-2

NUMBER OF PUBLIC DRINKING WATER SUPPLIES IN THE BIGHORN BASIN BY SERVICE CATEGORY (Serviced by Ground Water)

Community

Municipal

Non-Municipal Residence Mobile homes

Non-Community

Motel Marina Restaurant Ski resort Service station Campground Institution School Lodge Recreation other2

TOTAL 76

'some Public Water Supplies provide more than one service type. Therefore, the sum of the various services will be greater than 61.

2~ngeneral, other consists of "dude" ranches, drive-in movies, country clubs, etc. lo 1090 108O 107 O I ----,- I I

WASHAK I E

\ HOT SPRINGS / i EXPLANATION

€PA Public Drinking Wa System I D Number

Figure 111-1. Location of public drinking water supplies in the Bighorn bqsin. Municipal Systems

Municipal systems account for most of the ground water used for public drinking water in the Bighorn basin. Figures for 1977 (u.s.

Environmental Protection Agency Water Supply Division, Denver,

Information Files, 1977) indicate municipal use of ground water exceeded 1,600 acre-feet. This compares with an estimate of 1,100 acre-feet in 1970 by the U.S. Geological Survey (Lowry et al., 1976), which did not include all municipalities using ground water.

Nine municipal systems in the basin are supplied entirely by ground water, while the tenth (Thermopolis) utilizes mainly surface water, augmented by ground water during the summer (Table 111-3).

These systems are publicly owned with the exception of Grass Creek, which has a system provided by Marathon Oil Company, and Hyattville, which has a system owned by a private water company. In 1977, about

26,700 people in the basin were served by municipal sater systems, of which 6,400 were served exclusively by ground water, and 3,400

(Thermopolis) by both surface and ground water (U.S. Environmental

Protection Agency Water Supply Division, Denver, Information Files, 1980).

Sources of municipal ground-water supplies include the Quaternary aquifers, the Madison Limestone aquifer of the Paleozoic aquifer system, and the Lance and Mesaverde aquifers of the Upper Cretaceous-

Tertiary aquifer system (Table 111-3). Byron, Cowley, Kirby,

Powell, and Thermopolis utilize Quaternary alluvial or terrace aquifers as ground-water sources. The town of Byron has an infiltration gallery for this purpose whereas Powell uses collector type wells that are generally 30 feet or less in depth. Frannie, Hyattville, and Tensleep derive their water supply from flowing artesian Madison TABLE 111-3

MUNIC IPAL GROUND -WATER SUPPLIES IN THE BIGHORN BAS IN

EPA PWS State Aquifer System Average ~roduction'

Municipality ID No. ~ocation~Permit No. Depth - -/Aqa%fer (acre-feet/year)

Byron P45996W 15 /Quaternary Alluvium Cowley Unk . Unk. /Quaternary Alluvium Fr annie P406G 4500 Paleozoic a ad is on Grass Creek Unk . 300? -- /~esaverde Hyattville P2186W 2895 Paleozoic /Madison-Amsden Kirby P1632W 15 /Quaternary Alluvium P1633W 15 /Quaternary Alluvium Manderson P1343W 1215 U. Cretaceous-Tertiary /~ance Powell P511C 12 l~uaternaryTerrace P512C 20 /Quaternary Terrace P519G 35 /Quaternary Terrace P520G 27 l~uaternaryTerrace P518G 27 /Quaternary Terrace Tensleep P368G 1050 Paleozoic /Madison-Amsden Thermopolis P3805W 13 /Quaternary Alluvium

'1977, from U.S. Environmental Protection Agency, Water Supply Division, Denver. 2 See Appendix D for a description of the location/well numbering system used in this report. Limestone wells (Paleozoic aquifer system). The Tensleep town well is 1,050 feet deep, the Hyattville well is 2,895 feet deep, and the Frannie well, located toward the center of the basin, is 4,500 feet deep. Manderson derives its water from the Lance aquifer (Upper

Cretaceous-Tertiary aquifer system) at a depth of 1,215 feet, while

Grass Creek obtains its water from the Mesaverde Formation aquifer at a depth of about 300 feet.

Non-Municipal Systems

Five non-municipal community public drinking water supply systems support a population of about 600 within the Bighorn basin (U.S.

Environmental Protection Agency, Water Supply Division, Denver,

Information Files). These systems include a mobile home court and subdivision in the Powell area, and three mobile home courts in

Cody which obtain water from the Upper Cretaceous-Tertiary aquifer system or Quaternary terrace and alluvial deposits. Total non- municipal community consumption is about 110 acre-feet/year. Details about these systems are given in Table A-1 (Appendix A).

Non-Community Systems

The 61 non-community public drinking water supply systems in the Bighorn basin provide water to a variety of businesses, schools, and institutions. A list of these systems is provided in Table

A-2, and locations are shown on Figure 111-1. Production from non- community wells is estimated at 170 acre-feet/year, with individual systems producing from less than 0.3 acre-feet/year to over 9.3 acre-feetlyear. A variety of aquifers are used, but the most common are Quaternary deposits bordering streams (Table A-2). Surface-Water Use

Surface-water use in the Bighorn basin was estimated at 700,000 acre-feet for 1969 , with over 99 percent of the water applied to 329,500

acres of irrigated lands (Wyoming Water Planning Program, 1972). Irri-

gated lands in the basin now total about 348,000 acres (U.S. Soil Con- servation Service, Casper, Information Files, 1981), indicating no large

change in surface-water use. Annual variations likely occur, however,

as not all irrigated lands receive irrigation water in any given year;

figures for 1977 and 1978 indicate that about 245,000 acres, or 70 per-

cent of the total irrigated lands, receive irrigation waters annually

(Wyoming Crop and Livestock Reporting Service, 1979).

Additional, presently unappropriated, surface water supplies

are available. Under the terms of the Yellowstone River Compact, 80 percent of the unappropriated flow in the Bighorn River drainage is

allocated to Wyoming. This presently amounts to an average additional

surface-water supply of 1.8 million acre-feetiyear. Further, 60 per-

cent of the unappropriated flow of Clarks Fork of the Yellowstone

River, or about 430,000 acre-feetiyear, is allotted to the state

(Wyoming Water Planning Program, 1972). Potential problems involved

in developing these allocations for use within the basin include:

(1) the need for greater storage reservoir capacity; (2) questions

concerning ownership of waters originating on Indian lands; and (3)

possible trans-basin diversions to areas of intensive energy development.

The magnitude of available surface-water supplies suggests rel-

atively little future development pressure on ground-water supplies, in

comparison to other basins within the state where surface waters are

more fully appropriated. IV. HYDROGEOLOGY IV. HYDROGEOLOGY

Virtually all stratigraphic units within the Bighorn basin yield sufficient quantities of water for local stock and domestic purposes.

Even thick shale sequences, generally considered aquitards, will yield water from fracture zones and dispersed sandy interbeds. However, less than a dozen formations are developed as water sources regionally.

The following section discusses the hydrologic properties of the major aquifer systems and other water-bearing strata which occur within the

Bighorn basin sedimentary sequence (Table IV-1). A detailed description of aquifer lithologies is contained in Appendix B.

FLATHEAD AQUIFER

The basal Cambrian Flathead Sandstone represents the stratigraphically lowest important water-bearing unit in the basin (Table IV-1).

The Flathead overlies Precambrian granites and metasediments, and is isolated from younger aquifers by the thick shale and bentonite sequence of the overlying Gros Ventre and Gallatin formations (Stone, 1967; Vietti,

1977). The Flathead is uplifted and exposed along the basin flanks, and is locally absent parts of the northeast basin. Maximum thickness of the unit is 170 feet.

Hydrologic Properties

Hydrologic data for the Flathead Sandstone are sparse because of the great depth to the unit throughout much of the basin, and because of its relative position below the highly productive Paleozoic aquifer system.

Several flowing Flathead wells exist along the eastern basin flank, with TABLE IV-1

LITHOLOGIC AND HYDROLOGIC CHARACTERISTICS OF ROCK UNITS IN THE BIGHORN BASIN, WYOMING (Compiled from Numerous Sources, See References Chapter)

Aquifer System Thickness System Erathem and/or Series Geologic Unit (ft) Lithologic Character Hydrologic character l

m Quaternary: Flood-plain 0-loo+ Silt, sand, gravel and boulders. Major Aquifer. Yields >200 gpm k alluvium and Present along and adjoining major possible, especially where induced w-4 Holocene & terrace gravel stream channels & tributaries. recharge from diverted irrigation 3 Pleistocene deposits. Terraces 50-300' above present water occurs. Yields generally <50 s stream levels. gpm throughout Basin. Terraces are h topographically high and often (d drained by seeps and springs along k an escarpment. U 0 Specific Capacity: 0.3-70 gpm/ft w Permeability: 2,200-4,400 gpd/ft2 Transmissivity: 200-80,000 gpd/ft

Tertiary :

Eocene Willwood Fm. Highly variable, "red-banded" sub- Aquifer. Chief water-yielding unit arkose sandstone interbedded with of the Upper Cretaceous-Tertiary siltstone, mudstone, and locally Aquifer System with yields generally conglomeratic discontinuous between 5-20 gpm throughout the sandstone lenses. Principally central Basin. found in the central Bssin. Specific Capacity: 0.01-1.50 gpm/ft -UNCONFORMITY-

Paleocene Fort Union Fm. 600-3,500 Basal, cliff-forming sandstone Aquifer. Development not as exten- (Polecat Bench (SW-Central) and conglomerate, overlain by sive as in overlying Willwood Fm. Fm. ) 0-8,000 interbedded claystone, sandstone, Yields generally <20 gpm throughout (Min .-Max. ) siltstone and minor coal. Basin. Specific Capacity: 0.016-0.17 gpm/ft

Cretaceous: Upper Lance Fm. 800-1,800 Massive sandstone overlain by Aquifer. Not extensively developed. Cretaceous (SW-N) interbedded claystone, silt- Wells located primarily in the stone, shale and minor coal west-central and east-central parts seams. Forms resistant ledges. of the Basin. Flowing wells in the central Basin. Depth to water may be up to 200 feet along Basin margins. TABLE IV-1 (continued)

System Thickness Erathem and/or Series Geologic Unit (ft) Lithologic Character Hydrologic character1

Upper Meeteetse Fm. 650-1,200 Lenticular, poorly indurated fine- Aquifer. Minor unit of the Upper Cretaceous (SE-NW) grained clayey to silty sandstone Cretaceous-Tertiary Aquifer System. interbedded with siltstone, clay- Few wells completed in this unit in stone, shale, bentonite, and the Basin. Yields less than 15 gpm. minor thin coal beds.

Mesaverde Fm. 1,100-1,800 Highly variable sequence of fine- Aquifer. Mesaverde water wells (NE-S ,C) to coarse-grained sandstone, silt- primarily located in southwest and 900-1,400 stone carbonaceous shale and coal. southeast parts of Basin yielding 120 (E-W) Tripartite division into lower, gpm (5-10 gpm on the average), fine-grained sandstone, middle although yields up to 48 gpm have interbedded sandstone and shale, been reported. and upper coarse-graind sandstone. Specific Capacity: 0.75-1.8 gpmlft

Cody Shale 2,100-3,000 Lower half dominantly dark gray Regional Aquitard. Separates the (NW-SE) marine shale, glauconite sand- Upper Cretaceous-Tertiary Aquifer stone, and thin bentonite beds System from underlying, isolated whereas upper half is mainly lower Mesozoic aquifers. In frac- interbedded gray, sandy shale and tured areas and where encountering sandstone. confined sandstone beds, yields up to 20 gpm may be obtained.

Frontier Fm. 450-700 Lenticular fine- to medium- Minor Aquifer. Sandstones produce (W-SE) grained sandstone and conglomer- water under artesian conditions. atic sandstone beds alternating Porosity: 10-26% with shale and lesser amounts of 2 Permeability: 0-1.4 gpd/ft bentonite. Transmissivity : 0-100 gpd/ft2

Lower Mowry Shale Siliceous brittle shale with thin Aquitard. Yields water locally Cretaceous sandstone and bentonite beds in in fracture zones. the upper part.

Thermopolis 600-400 Soft shale with bentonite beds and Aquitard. Muddy Sandstone member Shale (NW-S) sandy and silty zones. Muddy sand- yields minor amounts of water. stone member, approximately 40 feet thick, about 200 feet above base.

Cloverly Fm. 85-470 Composed of three units, on upper Minor Aquifer. Produces water under (SE-NW) sandstone, a middle shale, and a artesian pressure, primarily from lower lenticular conglomeratic upper sandstone. Yield 52.0 gpm. sandstone Porosity: 7-15% and up to 2.2 gpd/ft2 (120 md) Transmissivity: 0-6 gpd/ft and up to 50 gpdlft TABLE IV-1 (continued)

Aquifer System Thickness System Era them and/or Series Geologic Unit (ft) Lithologic Character Hydrologic character1

UNCONFORMITY- Jurassic Morrison Fm. 75-300 Variegated sandy shale and mud- Minor Aquifer. Sandstone beds pro- (NW-S) stone with lenses of fine-grained duce small yields where they are sandstone, conglomerate and extensive. limestones. Porosity: 15%+

Sundance Fm. Gray-green shale interbedded with Minor Aquifer. Sandstone layers sandstone and brown fossiliferous produce small yields. limestone.

4a, Triassic Gypsum Springs Fm. 215-80 Red siltstone and shale with grey Minor Aquifer. Solution zones in a (E-W) to brown limestone beds and gypsum beds yield small amounts of 'd.ti C massive gypsum beds. water. a -UNCONFORMITY-- rdC: LCV1 LC w Chugwater Fm. 450-1,000 Interbedded red shaley siltstone Minor Aquifer. Sandstones and a, .rl 3 3 (NE- S ) and fine-grained sandstone with gypsum beds produce small amounts one limestone bed in the southern of artesian water locally. 5" part of the Basin. Contains .dU .dU Porosity: 15-22% some gypsum. N0 N0 Permeability: 0.4-2.2 gpd/ft2 0a, 0V1 (up to 120 md) d P) Transmissivity: 5-40 gpd/ft PIa x LC Dinwoody Fm. Thin-bedded silty shale and Not generally considered an aa, a siltstone. Upper part contains aquifer . 3 some limestone and gypsum.

Permian Phosphoria Fm. 100-300 In the eastern part of the basin, Leaky Confining Bed. Some facies (N-SE) the Phosphoria consists of a produces ground water under shale and siltstone sequence with artesian conditions. limestone and gypsum beds. In Porosity: 2-24% the western Basin it is a sandy Permeability: commonly <0.1-0.4 limestone and cherty dolomite. gpd/ft2 and locally up to 1.4 ,gpd/ft2 (76 md) Transmissivity: commonly ~0.5-10 gpd/ft and up to 40 gpdlft TABLE IV-1 (continued) - System Thickness Erathem and/or Series Geologic Unit (ft) Lithologic Character Hydrologic ~haracterl

-UNCONFORMITY--

Pennsylvanian Tensleep ., 57-400 Tan to white, massive, cross- Major Aquifer. Artesian wells often Sandstone (NW-SE) bedded sandstone. Lower part more flow at the surface with yields dolomite with interbedded carbon- commonly 50 to 200 gpm. ate beds. Primary intergranular Porosity: 3-26% 2 porosity and secondary fracture Permeability: <1-15 gpd/ft porosity present. (up to 800 md) Transmissivity:

Amsden Fm. Red shale and dolomite with chert Minor Aquifer. Darwin sandstone and occasional gypsum. Darwin member yields water under pressure. sandstone member at base ranges Porosity : lo%+ -UNCONFORMITY in thickness from 0 to 90 feet.

Mississippian Madison 880-300 Massive crystalline limestone and Major Aquifer. Artesian, yields to Limes tone (NW-SE) dolomite with siltstone and shale 3,000 tpm, but usually less. zones, cherty in places. Breccia Porosity: 10-20% filled paleokarst in upper part Permeability: 0.4-0.6 gpd/ftz and a second breccia zone in 7-1 ,OoO middle. Secondary porosity due to Transmissivit~: gpd/ft to 30,000 solution along joints and fractures. gpd/ft where highly -UNCONFORMITF fractured

Devonian Three Forks- Siltstone, dolomite and limestone Aquitard. Not generally considered Jefferson Fm. with green and black shales and an aquifer. (undivided) silty dolomite in the western part of the Basin. -UNCONFORMITY--

Ordovician Bighorn 450-0 Massive to thin-bedded dolomite Aquifer. Produces artesian water Dolomite (NW-SE) and dolomite limestone. Fine- in areas of fracturing and solution. grained massive sandstone at the Porosity: 13%+ base. Porosity primarily due to fracturing and solution. Contains cavernous zones near outcrop areas. TABLE IV-1 (continued)

Aquifer System Thickness System Erathem and/or Series Geologic Unit (ft) Lithologic Character Hydrologic ~haracterl

Gallat in/ 1,100-900 Shale, flat pebble conglomerate Aquitard. Dispersed sandy interbeds + Gros Ventre Fm. (NE-SW) and limestone sequence. may yield small quantities of water.

wad (undivided) Gros Ventre contains bentonite 3 2' beds. a Flathead 0-170 Arkosic and quartzitic sandstone Aquifer. Produces water under sa, Sands tone (NE-SW) with interbedded shales in the very high artesian pressure. Little upper part. data available on hydrologic 4rd characteristics. Reported yields Fl of over 2,000 gpm.

Granitic and meta-sedimentary Locally yields small amounts of rocks. water to wells

'porosity, permeability, and transmissivity data for the Paleozoic Aquifer System and the Upper Paleozoic-Lower and Middle Mesozoic aquifers are from drill-stem tests unless otherwise indicated (Tables IV-2, IV-3, and IV-6). Transmissivities from drill-stem tests are for limited pay thickness only. Upper Cretaceous-Lower Tertiary and Quaternary aquifer system data and all specific capacity data are from water well completion statements.

2~eophysicaldata consist of the geometric mean of transmissivity values estimated by core analysis, neutron log, and sonic log methods within a limited area (Bredehoeft, 1964). artesian pressures as high as 450 lb/in2 reported (Cooley, in press,

1980). Well 47/88-16, completed in the Madison Limestone and Bighorn

Dolomite as well as the Flathead Sandstone, is reported to flow at 1,500 gpm with a specific capacity of 1.25 gpm/ft (Table IV-3).

Several other wells completed in both the Flathead and overlying

Paleozoic aquifer exist in the Tensleep-Hyattville area, with reported flows of over 2,000 gpm from the Flathead aquifer itself.

Recharge to the Flathead is primarily through outcrop infiltration of precipitation and stream water. Though information is sparse, ground-water movement in the eastern basin is believed to be similar to movement within the overlying Paleozoic aquifer system, from areas of outcrop toward the Bighorn River and northward (Lowry et al., 1976).

PALEOZOIC AQUIFER SYSTEM

The Paleozoic aquifer system consists of Ordovician through

Pennsylvanian age strata, and is uplifted and exposed along the flanks of the mountains that rim the basin. This sequence dips steeply away from Precambrian outcrops at the basin margins and lies at depths greater than 25,000 feet in the basin center. Several small anticlinal uplifts trending north and northwest near the basin margins also expose Paleozoic aquifer member units along their crests (Zapp, 1956) . The major water-bearing units (aquifers) within the system are the Ordovician Bighorn Dolomite, the Mississippian Madison Lime- stone, and the Pennsylvanian Tensleep Sandstone (Dana, 1962; Lowry et al., 1976; Cooley, in press, 1980). Cooley (in press, 1980) con- siders the basal Darwin Sandstone member of the Pennsylvanian Amsden

Formation a minor aquifer, and the Upper Amsden shales as local confining beds between the Madison and Tensleep aquifers. The "tight" dolomites of the Devonian Jefferson-Three Forks formations act as a local confining bed between the Bighorn Dolomite and Madison Lime- stone. Therefore, the extent to which major aquifers are hydraulically interconnected or isolated by less permeable shales and dolomites is uncertain. A report by Dana (1962) discusses the Tensleep and

Madison aquifers together but does not define them as hydraulically interconnected. Lawson and Smith (1966) indicate there is intermingling of reservoir fluids in many Bighorn basin oil fields as a result of extensive vertical fracturing of the Paleozoic sequence. Stone

(1967) also discusses oil fields in the eastern basin (T. 55-58 N.,

R 97-99 W.; T 49 N., R. 102 W.; T. 50-52 N., R. 100 W.), where the

Bighorn through Phosphoria sequence is saturated with chemically and physically similar reservoir fluids due to communication through fractures and faults. Along the eastern flank, Cooley (in press) reports higher heads within the Madison and Bighorn aquifers than the Tensleep aquifer, except in areas of major faulting, where similar potentiometric levels indicate interformational communication.

The Paleozoic aquifer system is isolated from below by the thick sequence of impermeable shales and bentonites of the Cambrian Gallatin and Gros Ventre formations (Stone, 1967; Vietti, 1977), as evidenced by potentiometric heads several hundred feet higher in the basal

Cambrian Flathead aquifer than in the overlying Paleozoic aquifer system in the eastern basin (Cooley, in press).

The upper boundary is less certain, and is dependent upon complex intertonguing facies relationships in the overlying Permian Phosphoria

Formation. Lowry and others (1976) consider the Phosphoria to be part of the Paleozoic hydrologic sequence. Stone (1967) presents evidence suggesting that virtually all oil found in Ordovician through

Permian strata originated within and migrated downward from Phosphoria source beds. However, Stone (1967) also states that: (1) in the eastern part of the basin the Phosphoria consists of red shale and evaporite facies that are not generally considered petroleum reservoir rocks, indicating low permeability; (2) in the west and central basin the Phosphoria consists of carbonate, siltstone, and shale facies of which only the carbonates are considered reservoir rocks, indicating a variable permeability distribution ; (3) in general, only a part of the upper Phosphoria, averaging 20 feet in thickness, is considered to have "attractive reservoir characteristics," with per- 2 meabilities usually less than 10 millidarcies (<0.2 gpd/ft ) , which puts it in the "poor" aquifer range according to Todd (1959); (4) in the lower Phosphoria fracturing is commonly required for commercial oil product ion, again suggesting low permeability ; and (5) migration of oil from Phosphoria sources to underlying strata was achieved primarily along faults and fractures, indicating that the Phosphoria acts as a relatively effective confining bed outside of deformed areas. Additionally, distinct hydrochemical differences exist between the Phosphoria and underlying formations (Chapter V, this report).

Therefore, although the carbonate facies of the Phosphoria Formation locally produce exploitable amounts of ground water, for purposes of this report the Phosphoria siltstone and evaporite facies are considered leaky confining layers acting as the upper boundary of the Paleozoic aquifer system.

Current development of the Paleozoic aquifer system is heaviest along the basin margins, where drilling depths are generally less than 3,500 feet (Dana, 1962). Many wells, especially on the east side of the basin, flow at the surface. Common yields range from

25 to 200 gpm; however, a yield of several thousand gpm has been reported for one Madison well.

Hydrologic Properties

Hydrologic data from Paleozoic aquifer system water wells are generally restricted to the developed areas along the basin margins.

Very little data are available in the basin center, where excessive drilling depths have prevented development. Hydrologic data available from petroleum investigations, such as drill stem test results and core permeabilities, are generally limited to oil-producing structures on the periphery of the basin. Drill stem test data usually exhibit conservative transmissivity values because such estimates use limited pay thickness. Most hydrologic data from the Paleozoic aquifer system are for the Tensleep aquifer since it is the most significant oil- producing formation in the basin.

Permeabilitv

Tensleep Sandstone aquifer permeability is dependent upon the extent of secondary cementation and recrystallization of quartz grains, which increases with depth. Quartz cementation predominates in the north-central part of the basin while carbonate cementation increases toward the southeast (Todd, 1963). Petroleum data reveal a substantial loss of porosity and permeability with increased depth of the sandstone (Bredehoeft, 1964; Lawson and Smith, 1966). Bredehoeft (1964), utilizing core analysis, neutron log, and sonic log methods, noted differences in permeability ranging from greater than 800 millidarcies 2 2 (14 gpd/ft ) near outcrop to about I millidarcy (0.02 gpd/ft ) toward

the central basin. Permeability decreases with an increase in secondary

cementation and recrystallization, but may be enhanced in carbonate-

rich zones by fracturing and solution (Stone, 1967; Lowry et al.,

1976). Oil field data, generally from core analyses which do not

reflect fracture or solution permeability, commonly show a permeability 2 range from 0.1 to 200 millidarcies (less than 0.02 to 3.6 gpd/ft ) 2 with a few values as large as 800 millidarcies (14 gpd/ft ).

Permeability in the Madison Limestone and Bighorn Dolomite

aquifers is controlled primarily by zones of fractures, joints, solu-

tion features, and bedding-plane partings. Limited data on Madison

permeabilities from oil field records (Table IV-2) show a range from 2 20 to 34 millidarcies (0.4 to 0.6 gpd/ft ). One value for the Bighorn

Dolomite at Hamilton Dome Field (T. 44 N., R. 97-98 W.) was reported 2 at 40 millidarcies (0.9 gpd/ft ).

Specific Capacity

Specific capacity data calculated from water well completion

statements (Wyoming State Engineer's Office, Information Files, 1980)

are sparse for the Paleozoic aquifer system and range from 0.2 gpm/ft

to 10.2 gpm/ft (Table IV-3). In the adjacent Powder River basin,

the presence of nonlinear head losses within Madison wells is attri-

buted to turbulent flow within fractures in the well vicinity (Kelly

et al., 1980). The Madison aquifer of the Bighorn basin possesses

similar fracture and solution permeability, as does the Bighorn Dolo- mite, and both can be expected to exhibit decreasing specific capacity

data to estimate transmissivity within the Madison is dubious because

laminar flow criteria are not met. TABLE IV-2

HYDROWGIC PROPERTIES OF PALEOZOIC AQUIFER SYSTEM, BIGHORN BASIN, WYOMING (Determined from Oil Field Data)

Average Pay Estimated Field Location T/R Thickness (f t) % Porosity Permeability (md) Transmissivity (p,pd/ft)6 Source

TENSLEEP SANDSTONE Black Mountain 42-43N/90-91W 20 14 - - 1 Murphy Dome 44~197-98~ 180 14 99 300 1

Hamilton Dome

Little Sand Draw 44N/96W 52 10-11 0.8-1.7 0.8-2 1

Gebo 44N/95W 105 10 8 10 1

Murphy Dome 43-44N/91-92W 113 13 48 100

Grass Creek 46N/98-99W 90 14 110 200

Sunshine North 47N/101W 100 15 88 200

Gooseberry 47N/100W

Little Buffalo Basin 47-48N/100W 28 10 74 40 Hidden Dome 47-48~190-71W 54 16 - - Pitch Fork 48N/102W 102 3.3-22 0.4-7.1 0.8-10

Nowood 48N/90W 15 17 120 30

Spring Creek 49N/102W

Bonanza 49N/91W

Torchlight 51192-93W 2 3 17 200 80

Oregon Basin 50-52N/100-101~ 60 16 150 200

Shoshone 53~/101~ 100 26 560 1000

Alkali Anticline 55N/95W 18 10 - Whistle Creek 56N/98W 71 12 61 80

Gar land 56N/98W 59 14 53 60 TABLE IV-2 (continued)

P Average Pay Estimated Field Location T/R Thickness (f t) % Porosity Permeability (md) Transmissivity (gpd/ft)6 Source Remarks - Byron 56N197W 70 14 - - 1

Elk Basin, South 57~199~

Sage Creek, West 57N/98W

Big Pole Cat 57N/98~

Sage Creek 47~197-98W

Deaver 57~197~ 10 15 130 20 1

AMSDEN FORMATION

Grass Creek 46~198-99W 19 7 - - 2 Darwin Sandstone Member

Alkali Anticline 55N195~ 7 0 10 - - 1 Darwin Sandstone Member

MADISON LIMESTONE

Hamilton Dome 44~197-98W 160 16 25 70 1 Walker Dome 46N/99W 25 15 - - 1

Oregon Basin 40-51-52~/100-101W 200 13 - - 1 Torchlight 51~192-93~ 67 21 34 40 2

Elk Basin 47-58~199-100W 336 12 20 100 2

Sage Creek 57N/97-98W 20 10-20 20 7 1

BIGHORN DOLOMITE

Hamilton Dome 44N/97-98~ 44 13 4 0 50 1

1. Wyoming Geological Association, Oil and Gas Fields Symposium, 1957 (supplemented, 1961) 2. Biggs and Koch, 1970 3. Wyoming State Oil and Gas Commission Files 4. Wyoming Geological Association Guidebook, 1975 5. Wyoming Geological Association Guidebook, 1952 6. All transmissivities rounded to one significant digit. Transmissivity (gpd/ft) = Average Permeability (gpdlft2) x Average Pay Thickness (f t) . TABLE IV-3

REPORTED SPECIFIC CAPACITIES OF WELLS IN THE PALEOZOIC AQUIFER SYSTEM, BIGHORN BASIN, WYOMING

Test Spec if ic Well No. Geologic Total Duration Drawdown Yield Capacity Test T /R-Sec . Units* Depth (hrs) (ft) (p;pm) (p;pm/ft) Date Remarks

0.47 8/19/52 Flowing well.

0.40 Flowing well.

11/06/57 Flowing well. - Flowing well.

2/02/55 Flowing well, test on each producing 2/02/55 interval.

9/21/78 Flowing well.

8/--168 Flowing well.

- Flowing well.

Source: Wyoming State Engineer's Office, Cheyenne, Wyoming, 1980. Transmissivity

Transmissivity values were obtained from oil field reports (Table

IV-2) and various published hydrologic sources (Table IV-4). Lowry

(1962) reports values, estimated by recovery method, for the Tensleep aquifer of 1,000 to 3,000 gpd/ft. Bredehoeft (1964) related porosities, obtained from core analyses, neutron logs, and sonic logs, to permeability and calculated Tensleep transmissivities ranging from 7 to

1,800 gpd/ft. Values calculated from oil field pay thickness and permeability show a range from less than 1 to 1,000 gpd/ft within the sandstone.

Lowry (1962) reported transmissivity values of 540 and 890 gpd/ft for the Madison aquifer alone; other estimates of up to 5,000 gpd/ft included several Paleozoic system aquifers, though a value of 30,000 gpd/ft was reported for the town of Tensleep well, which produces primarily from the Madison aquifer. Madison transmissivity values from oil field reports vary from 7 to 100 gpd/ft, but the few values reported do not adequately represent the Madison aquifer. One value of 40 gpd/ft was reported for the Bighorn aquifer.

Ground-Water Movement

The Tensleep Sandstone is the only aquifer in the Paleozoic system for which data have been compiled into a potentiometric map

(Bredehoeft and Bennett, 1971). The map (Figure IV-1) is an approxima- tion of the pre-developmental potentiometric surface. Although it does not show present conditions and has little data control in many areas, it is useful for interpreting general flow patterns in the

Tensleep aquifer. Gradients are steepest along the rim of the basin and generally converge along the Bighorn River in the east-central TABLE IV-4 TRANSMISSIVITIES OF MEMBERS OF PALEOZOIC AQUIFER SYSTEM, BIGHORN BASIN, WYOMING

4 5 Well Location Geologic Transmissivity Data (T/R-Sec) Unit (s) (gal/day/ft) Source Method (s) Remarks

43N/91,92W-6,l Pt 2 x lo2 1 core analysis Geometric mean, 3 wells

44N187W-8 Pt 3 x 103 2 recovery method 2 44N/95W-23,24 Pt 1 x 10 1 neutron log, sonic log Geometric mean, 2 wells

core analysis, neutron log Geometric mean, 3 wells sonic log 1 45N/92W-23 Pt 2 x 10 1 neutron log 1 46N/98W-19 Pt 7 x 10 1 neutron log 47N/88W-16 Pt ,Mm 3 x 104 3 Jacob and Lohman method (1962) City of Tensleep well

2 recovery method

1 Core analysis, neutron log Geometric mean, 2 wells 1 48N1103W-20 Pt 6 x 10 1 Core analysis, neutron log Geometric mean, 1 well

49N/89W-24 Pt,PMa,MDm,Ob 5 lo3 2 recovery method Cn recovery method recovery method recovery method

50N/90W-14 Pt 1 2 recovery method 2 51N/93W-12 Pt 2 x 10 1 Core analysis, neutron log Geometric mean, 1 well 1 5 x 10 1 Core analysis Geometric mean, 3 wells

3 x lo2 1 Core analysis Geometric mean, 2 wells

56N/101W-16 Pt 7 x lo2 1 Core analysis, neutron log Geometric mean, 1 well 2 57N/97W-18 Pt 4 x 10 1 Core analysis, neutron log Geometric mean, 2 wells

1) Bredhoeft, John D., 1964 2) Lowrv. M.E.. 1962 3) State Engineers Office, Cheyenne, Wyoming 4) Pt - Tensleep Sandstone Ma - Amsden Formation MI)m - Madison Limestone Ob - Bighorn Dolomite 5) Transmissivity values rounded to one significant figure. Figure IV-1. Potentiometric surface of the Tensleep aquifer in the Bighorn basin. (modified from Bredehoeft and Bennett, 1971). basin rather than at the structural axis in the west-central basin.

Flow in areas adjacent to the Bighorn River is northward, into Montana

(Figure IV-1) .

Ground-water movement within the other Paleozoic aquifers is

assumed similar to flow in the Tensleep (Stone, 1967; Lowry et al.,

1972). Stone (1967) stated that the presence of hydrodynamically

tilted oil-water contacts in Tensleep petroleum reservoirs and the

horizontal nature of oil-water contacts in Madison reservoirs indicate

a higher, more uniform transmissivity and therefore a lower regional

gradient in the Madison relative to the Tensleep. However, little

other hydrologic data are available to support this relationship.

Wells penetrating the Paleozoic aquifer system characteristically

are under high artesian pressure and often flow at the surface. 2 Cooley (in press) reports shut-in pressures as high as 150 lb/in

from the Tensleep aquifer and from 150 to 250 lb/in2 for the Madison

and Bighorn aquifers; the relatively higher levels in the Madison

and Bighorn aquifers indicate the potential for regional ground-

water movement from these aquifers iata the overlying Tensleep aquifer.

Recharge to the Paleozoic aquifer system is primarily by direct

infiltration of precipitation through the basin margin outcrop area

(Lowry et al., 1976). Additionally, Vietti (1977) reports several

creeks which sink into solution-modified fault and fracture zones in

the Bighorn and Madison aquifers along the Bighorn Mountain flank (T.

51-52 N., R. 88 W.). Although many of these sinking streams resurge

a short distance from where they sink, several do not resurge, indi-

cating the streams provide recharge to the deeper parts of the basin.

Natural discharge from the Paleozoic system occurs where the

Bighorn River has breached anticlinal structures and exposed Paleozoic strata. Egemeier (1973) notes thermal Madison and/or Tensleep springs

discharging from the Sheep Mountain, Little Sheep Mountain, and

~hermopolis/WarmSprings anticlines (Figure 11-5), with flows as great

as 13,000 gpm issuing from the Madison aquifer along the latter struc-

ture. Spring flows from Paleozoic outcrops also occur along the

Rattlesnake Mountain anticline, west of Cody. Additional Paleozoic

discharge occurs in the Nowood River area (Cooley and Head, 1979b), where artesian Tensleep water rises along solution-collapse features

in the Phosphoria evaporite facies, and discharges either as seeps and

springs or as recharge to alluvial deposits overlying the Phosphoria.

UPPER PALEOZOIC AND LOWER AND MIDDLE MESOZOIC AQUIFERS

The Upper Paleozoic through Middle Mesozoic stratigraphic sequence

consists of impermeable shales that isolate discrete water-bearing

sandstone and carbonate units (Figure IV-2). The principal aquifers

are carbonate facies of the Permian Phosphoria Formation, two sandstone members of the Lower Cretaceous Cloverly Group, and sandstone beds within the Upper Cretaceous Frontier Formation (Dana, 1962; Lowry et al.,

1976). Intervening shales, though generally considered confining

layers, may have enhanced permeabilities in fractured zones, along bedding planes, and within coarser clastic beds (Berry and Littleton,

1961, Lowry et al., 1976). Minor yields have been reported from the

Chugwater Formation, shaley sands within the Morrison Formation, the

Mowry Shale, and the Muddy Sandstone Member of the Thermopolis Shale

(Berry and Littleton, 1961; Dana, 1962; Lowry et al., 1976).

Wells penetrating the Upper Paleozoic and Lower and Middle Meso-

zoic aquifers are primarily located in outcrop areas around the basin ERA SYSTEM ~LITHO~GY~FORMATION

Frontier Formation

Mowry Shale

Thermopolis Shale Muddy Sandstone Member

Cloverly Formation

Morrison Formation

Sundance Formation

Gypsum Springs Formation

Chugwater Formation

Dinwoody Formation Phosphoria Formation

Figure IV-2. Generalized Upper Paleozoic-Lower Mesozoic stratigraphy of the Bighorn basin. periphery where drilling depths are not great (Dana, 1962). Wells are commonly artesian, producing about 10 to 100 gpm.

Hydrologic Properties

Most of the hydrologic data for the Upper Paleozoic and Lower and

Middle Mesozoic aquifers are from investigations by the petroleum industry. Available water well data on these aquifers are restricted to the flanks of the basin and along the axes of anticlinal structures.

Permeabilitv

Permeability within the upper Phosphoria Formation is attributed to secondary intercrystalline and fracture porosity (Stone, 1967).

McCaleb and Willingham (1967) indicate that in areas where extensive vertical fracturing of Phosphoria dolomites has occurred, permeabilities are increased significantly. However, relatively low values for Phos- phoria permeabilities were reported at oil fields, from less than 0.1 2 to 20 millidarcies and locally as high as 76 millidarcies (1.4 gpd/ft )

(Table IV-5).

Sparse permeability values for the Cloverly Group sandstones 2 (Table IV-5) range from 4 to 120 millidarcies (0.1 to 2.2 gpd/ft ).

Air permeability tests on the Frontier Formation range up to 420 2 millidarcies (7.6 gpd/ft ). However, permeability to fluids is con- siderably lower, and dependent upon fluid salinity, formation clay content, and the absorption and floculating properties of the clays

(Baptist et al., 1952). Laboratory tests indicate that Frontier permeability to solutions containing 16,500 mg/l sodium chloride is 113 to

1/25 that of air permeability, while permeability to fresh water solutions (<200 mg/l TDS) is essentially nonexistent (Baptist et al., 1952). TABLE IV-5

HYDROLOGIC PROPERTIES OF UPPER PALEOZOIC AND LOWER AND MIDDLE MESOZOIC AQUIFERS, BIGHORN BASIN, WYOMING (Determined from Oil Field Data)

Average Pay Estimated Thickness % Permeability Transmissivity Field Location (T/R) ( ft) Porosity (md) (gpd/ft) l source Remarks

FRONTIER FORMATION Zimmerman 44N/93W 12 10 - - 1 Walker Dome

Grass Creek 46N/98-99W

Sand Creek m i-' i-'

Hidden Dome Worland

Torchlight TABLE IV-5 (continued)

Average Pay Estimated Thickness % Permeability Transmissivity Field Locat ion (T/R) (ft) Porosity (md) (gpd/ftI1 source Remarks

Whistle Creek 0.3 1.6 0.5 0 Badger Basin - Elk Basin, South 6 Elk Basin 0 Silver Tip -

CLOVERLY FORMATION Greybull, West 4.5 Bearcat 6 Upper sandstone member Badger Basin 4.2 Upper sandstone member Elk Basin, South 120 Upper sandstone member 9 Lower sandstone member Silver Tip, South 0 Upper sandstone member - Lower sandstone member

MORRISON FORMATION Gar land

CHUGWATER FORMATION Hamilton Dome Curtis Sandstone member Grass Creek Curtis Sandstone member Curtis Sandstone member Curtis Sandstone member

PHOSPHORIA FORMATION Water Creek 43-44Nl90-91W Little Sand Draw 44N/96W Hamilton Dome 44N 197-98W Gebo 44N/95W Z immerman 44N/93W Walker Dome 46N199W Grass Creek 46N/98-99W TABLE IV-5 (continued)

Average Pay Estimated Thickness % Permeability Transmissivity Field Location (T/R) (ft) Porosity (md) (gpdlft j ' source Remarks

Fourteen Mile Slick Creek Sunshine, North Gooseberry South Friday Meyer Gulch Cottonwood Creek

Wor land Spring Creek Meeteetse Nerber Dome Mander son Oregon Basin Alkali Anticline Gar land

'~11transmissivities rounded to one significant figure2 Transmissivity (gpd/ft) = Average Permeability (gpd/ft ) x Average Pay Thickness (ft).

*sources are: 1 = Wyoming Geological Association, Oil and Gas Fields Symposium, 1957 (Supplemented, 1961) 2 = Biggs and Koch, 1968 3 = Wyoming State Oil and Gas Commission Files 4 = Wyoming Geological Association Guidebook, 1975 5 = Wyoming Geological Association Guidebook, 1952 Specific Capacity

Available specific capacity data for the Upper Paleozoic and

Lower and Middle Mesozoic aquifers were obtained from domestic well pump test data. The values for the interval from the Phosphoria through the Frontier are commonly from about 0.1 to 4 gpm/ft of drawdown (Table IV-6). A few values as high as 30 gpm/ft also were reported.

Transmissivity

Transmissivity data available for the Upper Paleozoic and Lower and Middle Mesozoic aquifers are calculated from oil field permeabilities and reservoir pay thickness (Table IV-5). Values tabulated for Phosphoria transmissivity are low, varying from less than 0.1 to 4 gpd/ft. Values from drill stem test data will generally be low because only limited pay thickness is considered rather than total saturated thickness. Four Chugwater (Curtis Sandstone Member) transmissivity values, reported from oil fields in the southern end of the basin, range from 5 to 40 gpd/ft. Limited Cloverly transmissivity data for the upper sandstone member range from about 0 to 6 gpd/ft, with one value of 50 gpd/ft. Petroleum-producing sandstones within the Frontier aquifer exhibit a variation of transmissivity from 0 to 20 gpd/ft and locally as high as 100 gpd/ft. As discussed earlier, Frontier permeabilities are dependent on the salinity of the water; therefore transmissivity values calculated from air permeability test results should not be considered truly representative. TABLE IV-6

REPORTED SPECIFIC CAPACITY FOR WELLS IN THE UPPER PALEOZOIC $ND LOWER AND MIDDLE MESOZOIC AQUIFERS, BIGHORN BASIN, WYOMING

Well Test Specific Test Locat ion Geologic Duration Drawdown Yield Capacity Date (T/R-Sec .) orm mat ion2 (hrs) (ft) kpm) (gpm/ft) (month/year) Remarks Kf 8-16-76 flowing well

Kc f 2-60 flowing well Kcv 7-19-75 - Kc f 7-8-73 flowing well

Kc f 10-31-55

Kc f 5-20-53

Kc f 4-30-45

Kc f 10-?-52

Kc f 4-4-74 production from sand

Kc f 9-23-76 production from sand

Kc f 4-25-78 production from sand

Kc f 4-12-65 from sand

Kc f 8- -57

Kcv 4-8-78 production from sandstone

1R c 3-15-78 flowing well, production from sands tone

lRc 3-10-78 production from sandstone

Kft 6-26-74 production from sandstone and shale

Kf t 11-11-74

Kc f 6-16-73 production from sand

Kf t 2-15-71

Kf t 11-30-78 production from shale TABLE IV-6 (continued)

Well Test Specific Test Location Geologic Duration Drawdown Yield Capacity Date (T/R-Sec.) Formation' (hrs) (ft) (gpd (gpdft) (monthlyear) Remarks

52NI103W-34 Kf t 2 2 20 10.00 8-1-76

53N192W-33 Kft 116 90 10 0.11 6-22-77

53~1101W-27 Kf 2 18 25 1.40 2-24-71 production from shale

53N/101W-27 Kf 2 9 20 2.20 4-22-71 production from shale 53Nl101W-27 Kf 1 65 20 0.31 10172 production from shale

54NI94W-1 Jsg 1 1 20 20.00 4/64

54NI94W-1 Jsg 1 2 20 10.00 4/64

56N/96W-15 Kcf 2 2 60 30.00 5/73 production from shale

'well data obtained from State Engineers Office Cheyenne, Wyoming Specific capacity (gpmlft) = Yield (gpm) I Drawdown (ft)

'wells are completed in the indicated formation Kcf - Cody Shale and Frontier Formation undivided Kf - Frontier Formation Kft - Frontier Formation, Mowry Shale and Thermopolis Shale undivided Kcv - Cloverly Formation Jsg - Sundance and Gypsum Springs Formations undivided mc - Chugwater Formation Ground-Water Movement

No potentiometric map has yet been compiled for any of the Upper

Paleozoic and Lower and Middle Mesozoic aquifers. The shape of the potentiometric surface is complicated by the intertonguing of permeable and impermeable zones. Ground-water movement within these water- bearing units is generally assumed to be from the area of outcrop recharge basinward, often under artesian conditions (Berry and Little-

ton, 1961; Lowry et al., 1976).

Recharge of these aquifers is by infiltration of precipitation and streamflow in outcrop areas (Lowry et al., 1976). The aquifers may be recharged locally by interformational flow in fractured zones along anticlinal structures, and by infiltration of water from overlying saturated alluvium (Berry and Littleton, 1961; Lowry et al., 1976).

Ground water discharges from the aquifers through springs, seeps, interformational movement, and gaining streams (Lowry et ale, 1976). No recharge or discharge rate estimates are available for these aquifers.

UPPER CRETACEOUS-TERTIARY AQUIFER SYSTEM

The Upper Cretaceous-Tertiary aquifer system is comprised of the Cretaceous Mesaverde, Meeteetse, and Lance formations and the

Tertiary Fort Union and Willwood formations. The Tertiary units are found primarily in the central part of the basin and are nearly horizontal while the Lance, Meeteetse, and Mesaverde formations dip more steeply basinward and crop out progressively toward the basin margins.

Generally, the formations comprising the Upper Cretaceous-Tertiary aquifer system consist of lenticular, interfingering beds of sandstone, shale, siltstone, and claystone with occasional coal layers. Interbedded sandstones are the major water-bearing units, and are isolated in varying degrees by interlayered finer clastic rocks.

The Cody Shale, because of its thickness (over 2,000 feet throughout the basin) and small permeability, is considered the lower boundary of this system, hydraulically separating it from more deeply buried

Mesozoic aquifers. Unconsolidated Quaternary aquifers overlie this. system in places.

Hydrologic Properties

Most hydrologic data for the Upper Cretaceous-Tertiary aquifer system are from shallow wells completed in the areally extensive

Willwood aquifer and consist solely of specific capacity data obtained from limited yield/drawdown tests. Throughout the basin the Willwood, and to a lesser extent the Fort Union and Upper Cretaceous aquifers, are capable of yielding small quantities of water, generally less than 25 gpm. Several larger yields, ranging from 50 to 100 gpm, have been reported.

Specific Capacity

Specific capacity for the Willwood aquifer throughout the basin has a mean value of about 0.4 gpm/ft with the most common range being between 0.01 and 1.5 gpm/ft (Table IV-7). Values as high as 6.0 to 20.0 gpm/ft have been reported in parts of Park County. Pump test data for wells in the southeast part of the basin (Washakie

County) indicate a mean value for specific capacity of 0.2 gpm/ft, whereas in the northwest (Park County) the mean value for specific capacity is an order of magnitude larger, or about 3.0 gpm/ft. A conglomeratic facies present in the Willwood in the northwest basin

TABLE IV-7 (continued)

Well Specific Depth to Location yield Drawdown Capacity Total Depth Water (T/R-Sec.) (gpm) (ft> (gpdf t) (ft) (f t) TABLE IV-7 (continued)

Well Specific Depth to Location Yield Drawdown Capacity Total Depth Water (T/R-Sec.) (gpd (ft) (gpdft) (f t) (f t)

'well data obtained from State Engineers Office, Cheyenne, Wyoming. (Neasham and Vondra, 1972) is likely the reason for the higher specific capacities reported in that area. Limited data for other members of the Upper Cretaceous-Tertiary aquifer system indicate specific capacities ranging from 0.1 to 1.8 gpm/ft drawdown.

Ground-Water Movement

No potentiometric data for this aquifer system or its members have been published, and due to the lenticular nature of the sandstone bodies, which are interbedded with clays and silts, any potentiometric map would be difficult to interpret.

Recharge to the Cretaceous members of the Upper Cretaceous-

Tertiary aquifer system occurs chiefly by the direct infiltration of precipitation at the outcrop, especially where large dip slope expo- sures of sandstone bodies are present along the flanks of the surrounding mountains (Berry and Littleton, 1961). Where these sandstone bodies are confined by interbedded shaley units of markedly lower permeability, artesian conditions develop as the water moves further downgradient. In some instances these confined aquifers are interconnected by fractures which allow for upward movement of water.

Where fractures are not present, further aquifer interconnection may be accomplished due to the pressure head alone depending on the permeability, position, thickness, and areal extent of the intervening con£ ining beds (Berry and Littleton, 1961) .

Recharge of the Tertiary Willwood and Fort Union aquifers occurs by infiltration from precipitation at the outcrop and locally from outflow and seepage from juxtaposed and overlying saturated terrace gravels or flood plain alluvium deposits of Quaternary age (Swenson and Swenson, 1957; Berry and Littleton, 1961). QUATERNARY AQUIFERS

Quaternary aquifers consist of Pliocene to Recent unconsolidated terrace gravels, flood plain alluvium, and to a minor extent alluvial fan, glacial outwash, and landslide deposits. These deposits are primarily found in, along, and adjoining the major drainage systems of the basin (Plate 5). Scattered terrace remnants are distributed throughout the south-central basin. Thicknesses of these deposits vary depending on stream valley and location within the particular stream course. Terrace deposits are generally 15 to 50 feet thick with a maximum reported thickness of 62 feet, whereas flood plain alluvial deposits may vary from 20 to 90 feet in thickness. The combined thickness of these units is generally less than 100 feet, although they are not necessarily found as a stratified group.

Hydrologic Properties

Specific Capacity

Specific capacities for the two main types of Quaternary aquifers, terrace gravel and flood plain alluvium deposits, were not identified separately. Throughout the basin specific capacity generally ranges from about 0.5 to 25 gpm/ft, although values of over 50 gpm/ft are recorded in Park and Washakie counties (Table IV-8). Berry and Littleton

(1961) report an anomalous value of 70 gpm/ft in the Owl Creek Valley from a terrace gravel deposit. Specific capacities for irrigation wells completed in the Sunshine Terrace range from 25 to 55 gpm/ft

(Robinove and Langford , 1963) .

Transmissivities

Table IV-8 lists estimated transmissivites for Quaternary aquifer wells throughout the basin as well as well data collected from the TABLE IV-8

REPORTED SPECIFIC CAPACITY l AND ESTIMATED TRANSMISSIVITY FOR WELLS COMPLETED IN THE QUATERNARY AQUIFERS, BIGHORN BASIN, WYOMING

Well Specific Depth to Test Estimated Location Yield Drawdown Capacity Total Depth Water Length Transmissivity (T/R-See.) (gpd (ft) (gpm/f t) (f t) (ft) (hr) (gpdlft) TABLE IV-8 (continued)

Well Specific Depth to Test Estimated Location Yield Drawdown Capacity Total Depth Water Length Transmissivity (TIR-Sec. ) (gpm) (ft) (gpmlft) (ft) (ft) (hr) (gpdlft) TABLE IV-8 (continued)

Well Specific Depth to Test Estimated Location Yield Drawdown Capacity Total Depth Water Length Transmissivity (T/R-~ec.) (ppd (f t) (gpdft) (ft) (ft) (hr) (gpdlft) RABLE IV-8 (continued)

Well Specific Depth to Test Estimated Location - Yield Drawdown Capacity Total Depth Water Length Transmissivi ty (TIR-Sec. ) (gpm) (ft) (gpdft) (ft) (f t) (hr) (gpdlft)

Wyoming State Engineer's files. The estimated transmissivities, calcu-

lated from specific capacity through a method by Walton (1962),

throughout the basin ranges from about 200 to 81,000 gpd/ft, with

a mean value of roughly 8,000 gpd/ft. Berry and Littleton (1961)

determined permeabilities and transmissivities for three wells in

Own Creek terrace deposits using the recovery method. Transmissivities

averaged about 53,000 gpd/ft while permeabilities ranged from 2,200

Ground-Water Movement

Little potentiometric data are available for the Quaternary

aquifers. In general, flow within these aquifers is in the downstream

direction. Berry and Littleton (1961) determined that in the Owl

Creek drainage the general direction of ground-water flow was toward

the Bighorn River at very nearly the same slope as the stream channel

(75 feet per mile in the western part and about 30 feet per mile

in the eastern part). The main stem of Owl Creek is generally "gaining"

or effluent but is "losing" or influent near its confluence with

the Bighorn River. Robinove and Langford (1963) state that the general

direction of ground-water movement in the Greybull River Valley is

also towards the Bighorn River. The Greybull River is effluent

throughout most of its length.

Recharge of the Quaternary aquifers primarily occurs from the

direct infiltration of precipitation, discharge from underlying aqui-

fers, and seepage that occurs from irrigation canals, ephemeral

streams, and laterals (Swenson and Swenson, 1957; Berry and Littleton,

1961; Robinove and Langford, 1963; Cooley and Head, 1979b). The water table rises with the application of irrigation water, derived mainly from the diversion of surface water, and declines after irrigation ceases (Swenson and Swenson, 1957; Robinove and Langford, 1963).

Discharge from the Quaternary aquifers occurs chiefly by evapotranspiration, stream gains, and discharge from wells, seeps, and springs. Evapotranspiration occurs most extensively in the cultivated areas underlain by terrace gravel and flood plain alluvium. The yield from wells, used primarily for domestic and stock use, is generally less than 25 gpm, but occasionally, where greater saturated thicknesses are encountered or gallery-type wells constructed, much larger yields are obtained for irrigation and municipal use. The average total depth of wells completed in this system is less than about 30 feet with the average depth to water rarely exceeding 15 feet (Table IV-8). V. WATER QUALITY WATER QUALITY

Roughly 600 water quality analyses were reviewed for this report.

Data sources included: the U.S. Geological Survey WATSTOR data system, the Wyoming Water Resources Research Institute (WRRI) data system

(WRDS), compilations of oil field water analyses by Crawford (1940) and Crawford and Davis (1962), and analyses conducted by the WRRI staff. All analyses used, except the latter, are published or available elsewhere and therefore are not reproduced in this report. The analyses collected by WRRI are tabulated in Appendix C.

The first part of this chapter discusses the general water quality of major aquifers and systems in terms of dissolved solids content and major ion composition. Where possible, trends in these constituents and the mechanism causing them have been identified. The latter portion of the chapter addresses water quality related to U.S.

Environmental Protection Agency drinking water standards.

GENERAL WATER QUALITY

Flathead Aquifer

Data on Flathead aquifer water are sparse due to the current lack of development of the aquifer. Two relatively deep wells in the northeast basin (well 49/88-29, 2,205 feet deep; well 55/92-33,

4,900 feet deep) contained dissolved solids concentrations of 136 and 440 mg/l, respectively. The former sample consisted primarily of dissolved calcium-bicarbonate while the latter was predominantly sodium-sulfate-bicarbonate. While data are too sparse to allow for interpretation, good quality water is available from the Flathead, even at considerable depths.

Paleozoic Aquifer System

Existing chemical analyses from the Paleozoic aquifer system are mainly for well and spring waters from the Madison and Tensleep aquifers. Few analyses are available for waters from the underlying aquifers .

Available data indicate that little interformational difference exists in either total dissolved solids (TDS) concentration or in the major ion composition of Paleozoic system waters (Figure V-1).

Near-outcrop Paleozoic system wells and springs generally yield waters with less than 500 mg/l TDS (Plate 3), with dissolved calcium and bicarbonate being the dominant ionic species (Figure V-1) . Basin- ward, TDS concentrations increase to over 3,000 mg/l, and sulfate replaces bicarbonate as the major anion in solution. Several samples with TDS exceeding 3,000 mg/l show sodium and chloride enrichment

(Figure V-1) .

Chemical data for the central basin are sparse. Based on analyses from the east basin flank, TDS levels show a variable rate of basinward increase (Plate 3). Comparison of Plate 3 with Figure

V-1 shows a limited correlation between high TDS zones and areas of tightly spaced potentiometric contours, suggesting that at least some of the observed increase in dissolved solids content is related to low permeabilities and the resulting restriction of ground-water circulation. Tota l Dissolved Solids

Figure V-1. Major ion composition of waters from the Paleozoic aquifer system, Bighorn basin, Wyoming. Numbers plotted are percent of total milliequivalents per liter. UDD~~Paleozoic and Lower and Middle Mesozoic Aquifers

Hydrochemical data for the major water-bearing units of the

Upper Paleozoic through Middle Mesozoic sequence are mainly for oil field waters, due to the general lack of development of these aquifers as water sources. Available data, though sparse and poorly distributed geographically, indicate several basic similarities in waters from these aquifers. All produce water with dissolved solids concentrations ranging from less than 1,000 to over 10,000 mg/l.

All ground waters also show a relationship between TDS concentrations and major ion composition; however, the relationship between TDS levels and major ions varies from aquifer to aquifer.

Within the Phosphoria aquifer, ground waters with TDS concentrations below 3,000 mg/l characteristically are predominantly dissolved calcium-sulfate-bicarbonate (Figure V-2) . Within this concentration range, dissolved calcium sulfate concentrations correlate directly with TDS concentrations, probably due to gypsum/anhydrite dissolution.

Increasingly saline waters are predominantly sodium-chloride-sulfate rich.

Cloverly aquifer waters have a similar relationship between dissolved solids and major ion composition, although there is a higher proportion of dissolved sodium in low TDS (<3,000 mg/l) waters, and greater chloride enrichment in more saline (>5,000 mg/l TDS) waters (Figure V-3).

Frontier aquifer waters are predominantly sodium bicarbonate at TDS levels below 1,000 mg/l. Figure V-4 indicates a trend toward either sulfate or chloride enrichment with increasing TDS. TOTAL DISSOLVED SOLIDS

0 500-I000

Figure V-2. Major ion composition of waters from the Phosphoria Formation, Bighorn basin, Wyoming. Numbers plotted are percent of total milliequivalents per liter. TOTAL DISSOLVED SOLIDS

Figure V-3. Major ion composition of waters from the Cloverly Formation, Bighorn basin, Wyoming. Numbers plotted are percent of total milliequivalents per liter. TOTAL DISSOLVED SOLIDS

0 500-1000

Figure V-4. Major ion composition of waters from the Frontier Formation, Bighorn basin, Wyoming. Numbers plotted are percent of total milliequivalents per liter. Upper Cretaceous-Tertiary Aquifer System

Water quality data are more generally available for the Upper

Cretaceous-Tertiary aquifer system because of its broad areal extent in the central part of the Bighorn basin and its extensive use for stock and domestic purposes. The discontinuous lenticular nature of water-bearing zones results in highly variable water quality both locally and regionally. However, there is little formation-dependent variation in waters from this aquifer system.

Dissolved solids content of Upper Cretaceous-Tertiary waters varies from 250 to about 5,000 mg/l (Plate 4). Low TDS waters (<1,000 mg/l) are found in a band in the south-central part of the basin.

Several widely scattered zones produce waters with greater than 3,000 mg/l TDS. On a regional basis, most analyses range between 1,000 and 3,000 mg/l TDS.

Major ion composition shows a relationship to TDS. The few available analyses with less than 500 mg/l dissolved solids are calcium- sodium-bicarbonate rich, while waters containing 500 to 1,000 mg/l

TDS are sodium-bicarbonate-sulfate rich (Figure V-5). In general, increased salinity correlates with enrichment in sodium and sulfate.

Whether the observed correlative changes in TDS and major ion composition are related to local downgradient processes or regional lithologic variability cannot be confidently determined. However, the regional distribution of TDS content (Plate 4) suggests the presence of some large-scale lithologic control of water quality, such as soluble mineral content. TOTAL DISSOLVED SOLIDS

Figure V-5. Major ion composition of waters from the Upper Cretaceous- Tertiary aquifer system, Bighorn basin, Wyoming. Numbers plotted are percent of total milliequivalents per liter. Quaternary Aquifers

Numerous chemical analyses of Quaternary aquifer ground waters

exist due to extensive development for irrigation and drinking water

supplies. Existing data indicate that the quality of alluvial ground

water often varies greatly over short distances, though a generally

basinward, or downstream, increase in dissolved solids is present

along many drainages.

Flood plain deposits along the Bighorn River produce waters

with TDS concentrations ranging from 1,700 to 6,400 mg/l; adjacent

terrace deposits yield waters with TDS concentrations from 880 to

3,310 mg/l (Plate 5). There is no apparent trend in the spatial

distribution of dissolved solids content in these terrace and flood

plain deposits.

Analyses of water from flood plain deposits of the Nowood River

drainage basin indicate a general downstream increase in dissolved

solids (Cooley and Head, 1979b). TDS increases from 126 mg/l in

the upper reaches of the basin to over 2,370 mg/l along the lower

reaches of the Nowood River. Water upwelling from the Tensleep Form-

ation through the gypsiferous deposits of the Goose Egg Formation

and into the alluvial aquifer is considered the primary cause of

this increase (Cooley and Head, 1979b) .

Waters from Greybull River alluvium contain from 404 to 3,210 mg/l of dissolved solids. As in the Nowood River basin, there is

an apparent downstream increase in TDS. Upstream from T, 52 N.,

R. 96 W., TDS concentrations are less than 1,000 mg/l, while down-

stream from this area concentrations increase to over 3,000 mg/l.

Saturated terrace deposits along the Greybull River have TDS concentrations that range from 385 to 2,160 mg/l but are generally less than 1,000 mg/l. There is no apparent trend in the distribution of dissolved solids in terrace waters, as exists in the adjacent flood plain deposits. A similar distribution of dissolved solids in Greybull River alluvial and terrace waters was noted by Cooley and Head (1979a). No mechanism was suggested for causing the observed conditions.

Flood plain deposits along the Shoshone River produce water with TDS ranging from less than 100 mg/l, in the mountainous area west of Cody, to 1,210 mg/l in downstream areas of the central basin.

Terrace waters contain TDS concentrations ranging from 346 to 6,360 mg/l. All wells sampled prior to 1960, however, showed TDS concentrations in excess of 1,000 mg/l, while all wells sampled after 1960, with the exception of one, had TDS concentrations less than 1,000 mg/l. As explained below, irrigation has played a major role in determining the water quality of these deposits during the past several decades.

Prior to irrigation, many terraces along the Shoshone River were dry or had relatively low water levels. The initiation of irrigation raised both water and TDS levels, with dissolved solids increasing to several thousand milligrams per liter. Swenson and

Swenson (1957) stated that irrigation-related recharge increased the leaching of soluble minerals within the terrace deposits, resulting in increased TDS. They further suggested that as irrigation continued and soluble salts were largely removed from the terraces, TDS levels would decrease. Existing data support this conclusion. Waters which contained high TDS (>2,000 mg/l) concentrations during the initial years of irrigation have since fallen well below 1,000 mg/l TDS. Saturated alluvial and terrace deposits throughout the basin have relatively similar major ion compositions (Figures V-6 and V-7).

Cation composition is generally mixed, and anion composition changes with TDS levels. At low TDS levels (less than 500 mg/l) bicarbonate is the predominant anion, but with increasing TDS concentrations sulfate becomes dominant.

Absaroka Volcanics

Data on the chemistry of waters from the Absaroka volcanics are virtually nonexistent. Two recent samples analyzed (Appendix C) by WRRI are characterized by low dissolved solids (<200 mg/l) with sodium bicarbonate enrichment. This ionic composition indicates that the action of carbonic acid (H2C03) on sodium silicate minerals contained within the rhyolitic volcanic flows controls the evolution of Absaroka water quality. These two analyses also indicate that the saturated volcanics can produce excellent quality water.

DRINKING WATER STANDARDS

Primary Standards

Of the ten inorganic species for which primary drinking water standards exist, available data indicate that the concentration of two species of concern, fluoride and nitrate, often exceed standard levels in Bighorn basin ground waters. Data on the concentrations of the remaining eight species, however, are sparse and generally inconclusive.

Fluoride

The primary standard for fluoride is based upon the annual maximum daily air temperature at a given sampling site. Within the Bighorn Total Dissolved Solids

CATIONS ANIONS

Figure V-6. Major ion composition ofLwaters from Quaternary flood plain aquifers, Bighorn basin, Wyoming. Numbers plotted are percent of total milliequivalents per liter. Total Dissolved Solids

Figure V-7. Major ion composition of waters from Quaternary terrace aquifers, Bighorn basin, Wyoming. Numbers plotted are percent of total milliequivalents per liter. basin the standard varies from 2.0 to 2.4 mg/l (as F). Approximately one-fourth of the ground waters analyzed for fluoride contained greater than 2.0 mg/l-F. These concentrations occur in waters from all major aquifer systems, as well as many other water-bearing units (~igureV-8).

Waters from the Upper Cretaceous-Tertiary aquifer system show the highest frequency of fluoride levels above 2.0 mg/l (about 45 percent). Waters from the Willwood and Lance aquifers generally contain higher fluoride concentrations than do waters from other members of this aquifer system.

Roughly ten percent of the available analyses of Quaternary aquifer waters show fluoride levels greater than 2.0 mg/l-F. High fluoride levels in Quaternary waters are concentrated in the Dry

Creek drainage basin. Alluvium in the Dry Creek drainage is underlain by the Willwood aquifer, which contains high fluoride waters in this area, suggesting bedrock-alluvial water interaction at this locale.

Six of the 26 wells sampled for fluoride from Upper Paleozoic and Lower and Middle Mesozoic aquifers produce waters with fluoride concentrations exceeding 2.0 mg/l; the highest concentration (5.0 mg/l) was from a well completed in the Mowry Shale. The six wells with high fluoride concentrations were located in the southern and eastern parts of the basin.

About one-third of the sampled wells completed in the Paleozoic aquifer system produce water with fluoride concentrations exceeding

2.0 mg/l. Some spatial distribution of fluoride concentration exists, as evidenced by the low fluoride levels in Washakie County Paleozoic system waters (average 0.3 mg/l-F). The highest concentration (5.4 mg/l) was reported from a Madison oil well within Park County. I BIG H Dry Creek Irrigated Area L

I 2.1 a2.2 '---!------7 WASHAKIE 1 2.4 EXPLANATION .-----62.3 2.02% B3.''---] Quaternary Aquifer System i / 1 Upper Cretaceous /Tertiary Aquifer System

Upper Paleozoic, Lower and Middle I).mit Aquitus s Y i lor Paleozoic Aquitar System

Figure V-8. Location of ground-water fluoride concentrations greater than 2.0 rng/l. Temporal variations in fluoride levels occur within Bighorn basin ground waters. A Lance aquifer well that supplies the community of Manderson (T. 50 N., R. 92 W., Sec. 32) was tested for fluoride intermittently during the period 1970-1980. Fluoride levels have varied between 0.75 and 4.5 mg/l-F (Figure V-9), though concentrations of other dissolved constituents remained relatively constant. The cause of the observed variations cannot be explained at present.

Nitrate

Nitrate concentrations from nine sites have exceeded the nitrate primary standard (10 mg/l-N), though temporal variations exist and the tested waters may be below the standard at times. All concentrations above the standard have been from Upper Cretaceous-Tertiary or Quaternary waters (Figure V-10) and are related to livestock or irrigation activities.

Other Primary Standards

Little or no data exist for the other species* both inorganic and organic, that come under primary drinking water standards within the Bighorn basin. Less than 40 wells or systems have been sampled for constituents other than fluoride or nitrate. Where sampling has occurred, it is usually a one-time grab sample, and unless some standard was exceeded no follow-up sample was taken. These problems, coupled with analytical errors, make interpretations concerning the distribution of these constituents suspect.

Of the approximately 40 wells sampled for primary standard constituents, only selenium, mercury, and chromium have exceeded standards.

The mercury standard (0.002 mg/l) was exceeded in an alluvial (?) YEA R

Figure V-9. Variations in fluoride concentrations in Lance Formation waters, Manderson, Wyoming, T

BIG HO 10.8 PARK

I .' 2-4 I I 9- I 1. 1,- \a

HOT SPRINGS EXPLANATION

Quaternary Aquifer System

Upper Cretaceous / Tertiary Aquifer System

\ L I 1 1 Miles

Figure V-10. Location of ground-water nitrate concentrations in excess of 10 mg/l NO N. 3- well near Cody, but resampling produced a value below the standard.

The one high (0.12 mg/l) chromium value was from an alluvial aquifer

near Kirby. Sampling of this same well at other times has shown

chromium levels below the standard. Two analyses indicate selenium

concentrations above the standard (0.01 mg/l); one sample was Cloverly

aquifer water (well 43/89-23 add), and the other Quaternary aquifer

water (well 531101-1 dc). Both analyses report 0.02 mg/l selenium.

Secondary Standards

Several chemical constituents such as sulfate, chloride, and

iron, though not considered toxic, may be aesthetically undesirable

in excessive quantities in drinking water. In many localities, however,

since no better drinking water is available, the population has adjusted

to drinking highly mineralized waters. Chemical constituents of

secondary concern in drinking water supplies are summarized in Table v-l .

Total Dissolved Solids

The TDS content of Bighorn basin ground waters is shown in Plates

3 through 5. In general, waters containing less than 500 mg/l TDS

are limited to the Paleozoic aquifer system near outcrop and to Quaternary

aquifer waters in upstream areas. Dissolved solids in the Paleozoic

and Quaternary waters from other areas generally exceed 1,000 mg/l,

as do most other ground waters within the basin.

Sulfate

High sulfate concentrations (>250 mg/l) essentially coincide with high (>500 mg/l) TDS levels. In general, only near-outcrop TABLE V-1

CONCENTRATION RANGES FOR SULFATE, CHLORIDE, AND TOTAL DISSOLVED SOLIDS IN GROUND WATERS FROM THE BIGHORN BASIN, WYOMING

Sulfate Chloride TDS Source County (mdl) (mg/l) (mg/l)

Quaternary Aquifer System Bighorn 32-3000 Hot Springs 578-7250 Park 10-4350 Washakie 430-3610 Upper Cretaceous-Tertiary Bighorn 8-1780 Aquifer System Hot Springs 104-1830 Park 11-2730 Washakie 3-1740

P Upper Paleozoic through 0 N Middle Mesozoic Aquifers -Frontier Aquifer Bighorn Hot Springs Park Washakie -Cleverly Aquifer Bighorn 0-1550 Hot Springs 58-2025 Park 0-3560 Washakie 1390-1800 -Phosphoria Aquifer Bighorn 1560-1869 48-305 2690-3556 Hot Springs 1350-5757 173-3925 261-3840 Park 971-3805 86-1700 2804-9072 Washakie 20-1420 0.5-19 254-2400 TABLE V-1

(continued)

Sulfate Chloride TDS Source County (mg/l) (mg/l) (mg/l)

Paleozoic Aquifer System Bighorn 2-2420 0-1071 136-4270 Hot Springs 21-1480 3.1-1480 261-3840 Park 1370-2303 10-378 2494-3800 Washakie 2-60 0.4-3.0 202-208 Flathead Aquifer Bighorn 12-140 Hot Springs - Park - Was hakie -

I--' Sources: 0 U.S. Geological Survey, WATSTOR data system, 1980; Wyoming Water Resources Research Institute w data system (WRDS) , 1980. Paleozoic system waters and upstream Quaternary system waters meet the 250 mg/l secondary sulfate standard.

Chloride

Available data indicate that high chloride concentrations (>250 mg/l) are rarely associated with TDS levels below 3,000 mg/l, and are stratigraphically limited to Upper Paleozoic through Middle Mesozoic waters, along with some deep basin Paleozoic system waters.

Radionuclear Species

Existing analyses of radionuclear species in Bighorn basin ground waters generally include determinations for gross alpha and gross beta radiation, dissolved uranium, and radium-226 (Ra-226), a decay product of uranium-238. Primary drinking water standards have been established for radium-226 (5.0 p~i/l)and gross alpha (15.0 pCi/l) .

Analysis for radium-226, gross alpha, and gross beta contain an error limit that generally indicates the 95 percent confidence interval of the analysis. Large error limits are usually due to either (1) a lack of instrument sensitivity at low concentrations, or (2) particle absorption in samples containing high dissolved solids.

Where the confidence interval is large relative to the given absolute value, interpretation of results is difficult. 4 Based on available data, concentrations of radionuclear species in Bighorn basin ground waters are generally low (Table V-2). No values above the Ra-226 standard are reported, and only one high gross alpha concentration (16'8 pCi/l) has been detected, in water from a Willwood aquifer well (56/96-18 dd). Gross beta levels TABLE V-2

CONCENTRATIONS OF RADIONUCLEAR SPECIES IN GROUND WATERS FROM THE BIGHORN BASIN, WYOMING

Location U Ra-226 Gross Alpha Gross Beta (T/R-Sec-%-k) Aquifer (mg/l) (pCi/l) (pCi/l) (pCi/l) Remarks ' Quaternary 0.011 /Alluvium Quaternary 0.006 /A1luvium Quaternary 0.002 /Alluvium Quaternary N.D. /Alluvium Quaternary - - City of Powell water supply, /Alluvium old tower pump Quaternary - - City of Powell water supply, /Alluvium new tower pump Absaroka N .D. 025 Volcanics Absaroka N.D. Volcanics Willwood 0.003 /Ft. Union Willwood N .D. /Ft. Union Willwood N.D. /Ft. Union Willwood 0.004 /Ft. Union TABLE V-2

(continued)

Locat ion U Ra-226 Gross Alpha Gross Beta (T/R-see-%-%) Aquifer (mg/l) (pCi/l) (pci/l) (pci/l) ~emarks'

56/96-18 dd Willwood 0.010 0.19k0.44 16+8 21+12 Exceeds gross alpha standards /Ft. Union 571102-21 ba Willwood 0.003 0.03+0.20 3+3 425 /Ft. Union 43/89-23 add Cloverly N.D. O.OOk0.33 0217 0235 Water used for stock watering 56/46-12 ca Cloverly 0.006 0.61+0.38 4+6 0+11 44187-8 ac Tens leep 0.003 2.4+0.59 7+4 5+5 Water used for irrigation P o 47/88-16 cc Tensleep N .D. 3.2t1.1 1+3 024 m 50189-33 bd Tensleep 0.004 2.5726.7 7+5 8+6 47/88-12 bc Madison 0.002 2.9650.69 223 125

'~llwells are used for domestic purposes except where noted.

*N.D. indicates not detected. are generally less than 10 pCi/l and dissolved uranium levels rarely exceed 0.010 mg/l, in the range considered average for ground water

(Hem, 1970).

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Sando, William J., 1974, Ancient solution phenomena in the Madison Limestone (Mississippian) of north-central Wyoming: U.S. Geol. Survey Jour. Research, v. 2, p. 133-141.

Sando, W. J., Mackenzie, G., Jr., and Dutro, J. T., 1975, Stratigraphy and geologic history of the Amsden Formation (Mississippian and ~ennsylvanian)of Wyoming: U.S. Geol. Survey Prof. Paper 848-A, 83 p.

Stone, D. S., 1967, Theory of Paleozoic oil and gas accumulation in Bighorn basin, Wyoming: Am. Assoc. Pet. Geol. Bull., v. 51, p . 2056-2114.

Swenson, F. A., and Swenson, H. A., 1957, Geology and groundwater, Heart Mountain and Chapman Bench Divisions, Shoshone Irrigation Project, Wyoming: U.S. Geol. Survey Water-Supply Paper 1418, 55 p.

Theis, C. V., 1963, Chart for the computation of drawdowns in the vicinity of a discharging well: in Bentall, Ray, ed., Short- cuts and special problems in aquifer tests: U.S. Geol. Survey Water-Supply Paper 1545-C , p . C10-C15. Thom, C. E., 1952, Structural features of the Bighorn basin rim: Wyoming Geol. Assoc. Guidebook, 7th Annual Field Conference, Southern Bighorn Basin, p. 15-17.

Todd, T. W., 1959, Ground water hydrology; John Wiley and Sons, New York, 333 p.

Todd, T. W., 1963, Post-depositional history of Tensleep Sandstone, Bighorn basin, Wyoming: Am. Assoc. Pet. Geol. Bull., v. 47, p. 599-616.

Todd, T. W., 1964, Petrology of Pennsylvanian rocks, Bighorn basin, Wyoming: Am. Assoc. Pet. Geol. Bull., v. 48, p. 1063-1090.

Trelease, F. J., Swartz, T. J., Rechard, P. A., and Burman, R. D., 1970, Consumptive use of irrigation water in Wyoming: Wyoming Water Planning Program, 83 p.

U.S. Department of Agriculture, 1974, Wind-Bighorn-Clarks Fork River Type IV Survey, Wyoming Supplement.

U.S. Environmental Protection Agency, Information Piles, 1977.

U.S. Soil Conservation Service, Casper, Information Files, 1981.

Vietti, Barbara T., 1977, The geohydrology of the Black Butte and Canyon Creek areas, Bighorn Mountains, Wyoming: M.S. Thesis, University of Wyoming, 45 p.

Walton, W. C., 1962, Selected analytical methods for well and aquifer evaluation: Illinois State Water Survey, Bull. 49, 81 p.

Wyoming Crop and Livestock Reporting Service, 1979, Wyoming agricultural statistics, 1979: 106 p.

Wyoming Geological Association, 1957 (supplemented 1961), Wyoming oil and gas fields symposium: 579 p.

Wyoming State Engineer's Office, Cheyenne, Information Files, 1981.

Wyoming Water Planning Program, 1972, Water and related land resources of the Bighorn River basin, Wyoming: Wyo. Water Planning Prog. Report No. 11, 231 p.

Zapp, A. D., 1956, Structural contour map of the Tensleep Sandstone in the Bighorn basin, Wyoming and Montana: U.S. Geol. Survey Oil and Gas Invest. Map OM-182. APPENDIX A

NON-MUNICIPAL AND NON-COMMUNITY

PUBLIC DRINKING WATER SUPPLIES TABLE A-1

NON-MUNICIPAL COMMUNITY PUBLIC DRINKING WATER SUPPLIES IN THE BIGHORN BASIN (SUPPLIED BY GROUND WATER)

EPA PWS Location ID No. (T-R-S) Aquifer Service Applicant 5600043 55N-99W-5 Quat Resid. North End Water Users Assoc.

5600212 53N-101W-? Quat? Mobile Homes Rivers Bend Trailer Court

5600238 53N-101W-? Unk . Mobile Homes Green Acres Village 5600280 53N-101W-? Unk . Mobile Homes Mountain View Mobile Home Park

5600283 55N-99W-15 Quat Mobile Homes Brownies Trailer Court TABLE A-2

NON-COMMUNITY PUBLIC DRINKING WATER SUPPLIES IN THE BIGHORN BASIN (SUPPLIED BY GROUND WATER)

Location Aquifer System EPA PWS ID No. (T-R-Sec) or Aquifer 5600211 46N-93W-16 CT-Q

52N-105W-22 44'27'~ 109'43 'W Unk . Unk . 5600459 Unk . Unk .

5600466 Unk . Unk . TABLE A-2 (continued)

Location Aquifer System EPA PWS ID No. (T-R-Sec) or Aquifer 5600473 Unk . Unk . 5600476 Unk . Unk .

5600508 Unk . Unk .

Unk . Unk. 47N-93W-24 CT 5600516 Unk . Unk .

5600627 52N-101W-4 Unk . TABLE A-2 (continued)

Location Aquifer System EPA PWS ID No. (T-R-Sec) or Aquifer

5600706 46N-102W-15 CT 5600714 Unk . Unk . 5600717 Unk . Unk .

5600738 47N-92W-18 Unk 5600744 52N-103W-10 CT?

Q = Quaternary aquifer CT = Upper Cretaceous-Tertiary aquifer system M = Upper Paleozoic and Lower and Middle Mesozoic aquifers P = Paleozoic aquifer system Unk. = Unknown APPENDIX B

GEOLOGIC PROPERTIES OF

MAJOR WATER-BEARING STRATA APPENDIX B

GEOLOGIC PROPERTIES OF WJOR WATER-BEARING STRATA

Flathead Aquifer

The Cambrian Flathead Sandstone lies at the base of the Paleozoic section above crystalline Precambrian rocks (see Figure 11-3). Stone

(1967) describes the Flathead as a sandstone composed of "coarse angular grains in a finer sand matrix" becoming conglomeratic near the base. Toward the top of the formation the sandstone is interbedded with shales especially in the eastern part of the basin. The Flathead is thickest in the western part of the basin where it attains a thickness of 170 feet, and is absent in parts of the northeastern basin.

No quantitative data are available on the porosity of the Flathead.

However, several authors consider it to have good reservoir and aquifer capabilities (Mills, 1956; Stone, 1967; Cooley, in press, 1980).

Paleozoic Aauifer Svstem

Bighorn Dolomite

The Ordovician Bighorn Dolomite is represented by two units in the

Bighorn basin, a lower dolomite and sandstone unit, and an upper massive and thin-bedded dolomite unit (Richards and Nieschmidt, 1961). The massive cliff-forming dolomites within the formation characteristically weather to a pitted, sharp-edged surface (Mills, 1956). They are well jointed throughout, with spacings as large as 10 feet (Vietti, 1977).

The development of recent karst features, such as sinkholes, solution caves, and sinking and rising streams, is generally controlled by faults and associated fracture zones (Hoxie , 1976 ; Vietti, 1977) . Bighorn porosity is principally associated with fracture zones, joints, and partings along bedding planes which have been enlarged by solution

(Vietti, 1977). One porosity estimate for the Bighorn Dolomite at the Hamilton Dome oil field was reported at 13 percent (TableIV-2).

The Jefferson Formation overlies the Bighorn Dolomite in the western and northeastern part of the basin, but is missing in the southeast, where the Madison Limestone unconformably overlies the

Bighorn Dolomite. The Bighorn, absent in the extreme southeastern corner of the basin, thickens to 450 feet in the northwest (Stone,

1967). Darton (1906) suggests that this southeastward thinning is due to pre-Mississippian erosion. The dolomite is underlain by the

800-foot sequence of shales, limestones, conglomerates, and bentonites of the Gallatin and Gros Ventre formations.

Madison Limestone

The Mississippian Madison Limestone consists predominantly of limestone and dolomite in the Bighorn basin. The upper part, known as the Bull Ridge Member, contains fossiliferous limestone and dolomite beds, with silty dolomite and shale at the base. Pre-Laramide solution features present in the silty zone are filled with a dolomite and limestone breccia (Sando, 1974). The middle part of the Madison

Limestone is a cherty limestone and dolomite that contains an extensively brecciated zone. The breccia is 10 to 50 feet thick and composed of angular carbonate fragments in a siltstone and shale matrix (Sando,

1975). The basal part of the formation varies locally from a finely crystalline dolomite and limestone to a silty shale and quartz siltstone. Porosity in the Madison carbonates is both intercrystalline and fracture related. Modern solution enlargement of faults and fractures has been noted in Madison outcrop areas (Hoxie, 1976; Vietti, 1977).

Paleokarst features within the formation are filled with fine-grained, well-cemented breccias and are not considered hydrologically significant

(Vietti, 1977). Limited data from oil and gas records show a range in

Madison porosity from 10 percent to 21 percent (Table IV-2).

In the northern Bighorn basin the Madison section is about 880 feet thick and thins southeastwardly to about 300 feet (Stone, 1967;

Egemeier, 1973). The lower contact of the Madison Limestone is unconformable with rocks of Devonian and Ordovician age. In the southern part of the basin the Madison rests on the Bighorn Formation and to the north it overlies the Jefferson Formation.

Amsden Formation

In most of the Bighorn basin, the Amsden Formation consists of three members ranging from Late Mississippian to Early Pennsylvanian age (Sando et al., 1975). The upper limestone and dolomite member is microcrystalline to finely crystalline in texture with abundant chert.

The limestone is locally interbedded with shales, and in the northern part of the basin the upper limestone is sandy with numerous interbedded sandstones. The middle shale member is interbedded with sandstones and becomes sandier toward the bottom.

The basal Darwin Sandstone is the most significant water-bearing unit within this formation. The sand is primarily quartz, well sorted,

fine to coarse in size, and has a porosity of about 8 percent based on very sparse data. Thickness of the basal sandstone varies widely over the basin from a maximum of 90 feet to zero in places (Mills, l956), due to unconformable deposition onto the Madison Limestone (Stone,

1967; Sando, 1974). Thickness of the entire formation varies from 117

feet in the northwestern part of the basin (sand0 et al., 1975) to a maximum of about 300 feet to the east.

Tensleep Sandstone

The Pennsylvanian Tensleep Sandstone is a massive to cross-bedded, well sorted, fine- to very fine-grained sandstone with subangular to

subrounded grains (Todd, 1964). The sandstone is composed of 82 to

92 percent quartz grains cemented with quartz and carbonate (Mankiewicz

and Steidtmann, 1979). Finely crystalline limestone and dolomitic

limestone beds within the sandstone unit range from 2 to 18 feet in

thickness, grade laterally into sandstone, and are most numerous in the southwestern part of the basin (Agatston, 1954).

Formation porosity is a function of the degree of cementation and recrystallization, which increases with the depth of burial of the sandstone (Todd, 1963; Bredehoeft, 1964). Lawson and Smith (1966) report an average porosity of 15 percent for the Tensleep at depths less than

5,000 feet, but only a 4 percent average porosity where the sandstone

is buried greater than 10,000 feet (Figure B-1). Data compiled from oil and gas field records indicate a range of porosity from 3 to 26 percent for the sandstone a able IV-2). Areas of prominent folding and faulting and associated fracture zones display increased secondary

porosity (~awsonand Smith, 1966; Lowry et al., 1976).

The Tensleep Sandstone is thinnest in the northern Bighorn basin where it ranges from 57 to 125 feet and is thickest in the southern Mesa

POROSITY

Figure B-1. Variation of porosity with depth in the Tensleep Sandstone in the Bighorn basin. Values represent average porosities for the sandstone section. Named values are for specific oil fields. (After Lawson and Smith, 1966). basin where it reaches 400 feet (Zapp, 1956). North of the Wyoming-

Montana border, the formation thickens again. The variation in thickness is probably due to post-Tensleep uplift and subsequent erosion

(Agatston, 1954; Pedry, 1975). The overlying Phosphoria Formation is

thick in areas of thin Tensleep and thin where the Tensleep is thickest

(Agatston, 1954). The formation lies as deep as 14,000 feet below the

land surface along the axis of the basin in the northwestern area

(Zapp, 1956).

Upper Paleozoic and Lawer and Middle Mesozoic Aquifers

Phosphoria Formation

Nomenclature of the Permian rocks in the Bighorn basin is complicated due to variable lithologies and facies changes within the unit.

The sequence can be divided into two distinct facies in the Bighorn basin: a carbonate facies known as the Park City Formation (McKelvey et al., 1956) and a red shale and evaporite facies named the Goose Egg

Formation (Burk and Thomas, 1956). Because the name Phosphoria is so widely used in the literature to include both of these facies, it will

also be used -in this report.

In the western and central part of the basin, the Phosphoria

carbonate facies is composed mostly of cherty dolomite and sandy lime-

stone interbedded with dark phosphatic shale and dolomite (Stone, 1967).

Limestones and dolomites are finely crystalline to finely granular in

texture. A second facies of red shale and siltstone with gypsum and

limestone intertongue with the carbonates and dominate the eastern side

of the basin (Mills, 1956). Solution within thick gypsum beds has formed collapse features which are present along the west flank of

the Bighorn Mountains (Cooley and Head, 1979b).

Porosities within the carbonate facies are intergranular, modified by dolomitization of limestones, solution, and fracturing

(Stone, 1967). Stone (1967) reports average porosities for the upper dolomite unit at less than 10 percent. Available data, compiled

from oil field reports, indicate a range in Phosphoria porosity from

2 to 24 percent (Table IV-5). McCaleb and Willingham (1967) discuss

the importance of fracture-related permeability in the Phosphoria carbonates at Cottonwood Creek field in the east-central part of

the basin. The shales and evaporites in the eastern basin have little or no porosity except in areas of fracturing and solution.

Sediments of the Phosphoria Formation fill the irregular ero-

sional surface of the Tensleep Sandstone (Agatston, 1954). The thickness of the sequence varies from about 100 feet in the northern area to about 300 feet in the southeastern end of the basin (Lowry et al., 1976).

The thin Dinwoody sequence, conformably overlying the Phosphoria, possesses little permeability (Stone, 1967) and therefore generally acts as a confining bed where present.

Cloverly Formation

The Lower Cretaceous Cloverly Formation is divided into three distinct units: a basal sandstone, a middle shale, and an upper sandstone. The lower member is composed of fine to coarse sandstones, conglomeratic sandstone, conglomerate, and siltstones, with thin layers of shale. Most of the middle Cloverly is composed of massive shales and claystones, with occasional sandstone lenses. The upper sandstone of the formation consists of fine to medium, subangular to subrounded quartz grains grading upward into interbedded silty sandstones and shales. This upper sandstone interval is most developed in the southern end of the basin and is regarded as conformable with the overlying Thermopolis Shale.

Intergranular porosities within the sandstones of this formation vary with the degree of cementation, sorting, and grain size. Stone

(1967) reports that the sandstones of the Cloverly are apparently tight over much of the northern Bighorn basin. Porosity values from oil field data in the northern and northeastern part of the basin range from 7 to 15 percent (Table IV-5).

Mills (1956) reports the thickness of the Cloverly sequence as generally 400 to 470 feet along the west side of the basin, and thinning to about 85 feet at the southeast end. The contact of the lower conglomeratic unit with the Morrison Formation is difficult to distinguish because of similar lithologies; therefore thicknesses reported in the literature often vary.

Frontier Format ion

The Upper Cretaceous Frontier Formation is a sequence of sandstones and conglomeratic sandstone alternating with shale and lesser amounts of bentonite (Keefer, 1972). Sandstones are described as

"salt and pepper," gray, fine- to medium-grained, friable to well cemented, argillaceous, and locally glauconitic. Most sandstone units are thin-bedded and lenticular; however, several distinct units are persistent in most of the basin. Conglomeratic and coarse-grained sandstones with chert locally occur near the top of the formation (Masters, 1952). Shales are generally gray, silty to sandy, fissile, and carbonaceous in places. Sandstones are most abundant in the southwestern part of the basin, while shales predominate in the eastern part. Upper Frontier sandstone units intertongue with the overlying

Cody Shale, and the Lower Frontier shale beds are gradational with the Mowry Shale.

Porosity in the Frontier sandstone units, in general, is lowest in the northern part of the basin (Baptist et al., 1952). The properties and content of clay minerals within the sandstone have a major effect upon the porosity and hydrologic characteristics of the sandstone units. Fresh water saturating some argillaceous sandstones in the formations causes dispersal of clays and extreme decreases in porosity (Baptist et al., 1952) . Porosities determined at numerous oil fields range from 10 percent to 26 percent for various sandstones within the Frontier (Table IV-5).

The Frontier Formation maintains a fairly constant thickness of 450 feet on the western side of the basin, and thickens eastward to about 650 to 700 feet (Hunter, 1952; Lowry et al., 1976). The

Frontier Formation is exposed along with the Paleozoic and Lower

Mesozoic sequence on the basin margins (Pierce et al., 1947).

Minor Water-Bearing Units

The Chugwater Formation of Triassic age consists of a lower shaley siltstone and shale, a thin middle limestone unit, a middle fine- to medium-grained sandstone with occasional shales (Curtis

Member), and a thick upper shale and siltstone unit (Love, 1957).

Sandstones within the formation reportedly yield water to wells at some locations (Lowry et al., 1976). Limited porosity data for the Curtis Sandstone Member range from 15 to 22 percent in oil fields of the south-central basin (Table IV-5). This sandstone unit is between 45 and 75 feet thick in the Bighorn basin (Mills, 1956).

The Muddy Sandstone Member of the Thermopolis Shale is known to yield small amounts of water to wells (Lowry et al., 1976). It is composed of sandstones and siltstones. Shales are commonly interbedded with sandstones, especially in the northern basin where the

Muddy grades into silts and sandy shales (Mills, 1956). No data are available on porosity of the Muddy Sandstone. Thickness varies from less than 10 feet at the north end of the basin to about 55 feet in the southeast (Mills, 1956).

Brittle, siliceous shales of the Mowry Formation develop fracture porosity in areas of folding and faulting and yield water to wells in some of these areas (Lowry et al., 1976). The Mowry is generally

370 feet thick throughout the basin.

Upper Cretaceous-Tertiary Aquifer System

Mesaverde Format ion

The Mesaverde Formation is comprised of a highly variable sequence of sandstone, shale, carbonaceous shale, and coal. The formation ranges in thickness from about 1,800 feet in the south-central part of the basin (Rohrer, 1966) to approximately 1,350 feet thick in the northern part (Pierce and Andrews, 1941). The contact between the underlying Cody Shale and the Mesaverde is gradational, defined at the base of the lowest massive sandstone below the lowest coal zone (Pierce and Andrews, 1941). The Mesaverde Formation is overlain conformably by the Meeteetse Formation, and the contact is placed at the change from resistant massive sandstone to nonresistant bentonite, claystone, shale, siltstone, or clayey sandstone of the

Meeteetse (Rohrer , 1966) .

Generally, the Mesaverde Formation can be divided into three parts that include a lower sandstone, a middle interbedded sandstone and shale unit, and an upper sandstone. Most individual beds are lenticular and can be traced laterally for only short distances. Sandstones in the lower and middle parts of the formation are characteristically tan, gray to yellowish-gray, very fine- to medium-grained, irregularly bedded to massive and cross-bedded, and friable to well-cemented. The sandstones constituting the upper members are white to light gray, very fine- to coarse-grained, massive to cross-bedded, moderately porous and friable, and ledge-forming. Individual sandstone beds range in thickness from a few feet to tens of feet, although Pierce and

Andrews (1941) measured one in excess of 350 feet in the upper part of the formation south of Cody.

Meeteetse Formation

The Upper Cretaceous Meeteetse Formation is comprised of slope forming, poorly indurated clayey to silty sandstone interbedded with siltstone, claystone, shale, bentonite, and thin coal beds. The formation is 650 to 710 feet thick inthe southeast part of the basin

(Rohrer, 1966) increasing to a maximum thickness of 1,200 feet toward the northwest (Pierce and Andrews, 1941). The contact with the overlying Lance Formation is sharp and marked by slope-forming Meeteetse strata overlain by the relatively resistant massive sandstones of the

Lance (Rohrer , 1966) . Most of the beds in the Meeteetse Formation are lenticular and

discontinuous, commonly pinching out within a few hundred feet along

strike. Sandstone beds grade laterally into siltstone and claystone.

The sandstone, most dominant in the lower part of the formation,

is generally light gray to buff, fine-grained, thin-bedded to massive,

and often concretionary. Individual beds are commonly less than

20 feet thick and attain a maximum thickness of about 50 feet near

the base of the formation.

Lance Formation

The Lance Formation is comprised principally of massive sandstone

overlain by interbedded claystone, siltstone, and sandstone. In

the southwest part of the basin the unit is approximately 800 feet

thick (Rohrer, 1966) and increases in thickness toward the north.

A section of the Lance Formation on the Shoshone River measured by

Hewett (1914) is about 1,800 feet thick, of which over 1,500 feet

consist of buff to olive green, friable sandstone. The contact with

the overlying Fort Union (Polecat Bench) Formation, according to

Hewett (1926), is marked by an unconformity.

The Lance is characterized by the dominance of poorly indurated

sandstone over claystone and shale. Rohrer (1966) informally sub-

divides the formation into a mainly massive sandstone, a lower member

about 500 feet thick, and a 210-foot-thick upper member consisting

of interbedded claystone, siltstone, and sandstone. The sandstone

in the lower member is light buff to gray, fine- to medium-grained, massive to thin-bedded, and generally cliff-forming. The upper member

is primarily claystone and siltstone with two principal buff-gray,

fine-grained sandstone beds, each about 10 feet thick. Fort Union Formation

The Paleocene Fort Union Formation (Polecat Bench Formation of Jepsen, 1940, and Jepsen and Van Houten, 1947) consists of a basal, cliff-forming sandstone and conglomerate overlain by alternating claystone, sandstone, and siltstone beds with minor amounts of coal.

Absent along the basin flanks, in the center basin the formation ranges in thickness from over 600 feet in the southwest part of the basin (Rohrer, 1966) to more than 3,500 feet. Reworked Fort Union accumulations from marginal, uplifted parts of the basin could account for the abnormally large thickness in the center of the basin (Rohrer,

1966). Over much of the central basin the contact with the overlying

Willwood Formation is conformable, although this relationship grades laterally toward the basin margins into an angular unconformity

(Weasham, 1967). In areas of conformity the most suitable contact between the Fort Union and Willwood formations is determined by the sudden appearance of hornblende in Willwood strata or the first occurrence of Willwood "red-banding" (Neasham, 1967).

Sandstone members of the formation are commonly fine- to coarse- grained, irregularly bedded, and ledge-forming. Cross-bedded and channel sandstones are also commonly observed. Individual strata are rarely traceable for more than a few hundred yards.

Willwood Formation

The Willwood Formation crops out mainly in the central part of the basin and is composed of variegated mudstone, sandstone, and locally abundant conglomerate. Near Basin, Wyoming, the Willwood is approximately 2,300 feet thick but it thins to the west, where near Meeteetse a section was measured at 1,320 feet. The Willwood Formation

is overlain conformably by the Tatman Formation of Middle Eocene age.

Neasham (1967) determined, for an "idealized" Willwood section,

that particular lithologic and stratigraphic features were repeated in

the depositional history. The dominant member of a depositional

sequence is a basal sandstone consisting of a main channel sandstone

and laterally extending "sheet" sandstones. "Sheet" sandstones are

characterized by thin units of relatively uniform thickness and lithology

that extend up to half a mile from the main channel and consist of a more fine-grained material than the channel sandstones. The channel

sandstones, generally 5 to 50 feet wide and 1 to 2 feet thick, reach as much as 35 feet in thickness. The basal sandstone grades vertically upward into progressively finer-grained, red or maroon sandstone, or

siltstone. Overlying these units are predominantly yellowish-brown,

grayish-green siltstones and claystones, which are capped by red or maroon silty claystone, grading upward into a lavender silty claystone.

From these alternating horizons the name "red-banded1' Willwood is derived. These two units are overlain in turn by channel sandstones which mark the initiation of a new depositional sequence (Neasham,

1967). The upper maroon and lavender beds are often truncated by channel sandstones of the next sequence, with the cut-and-fill rela-

tionships extending several feet into the underlying strata.

Ouaternarv Aquifers

Owl Creek Area

Owl Creek is located in the south-central part of the basin along the northward dipping flanks of the Owl Creek Mountains. Generally the terrace deposits are located to the north of and 30 to 50 feet above

Owl Creek and consist of gravel, sand, and silt, but pebbles and cobbles are locally present (Berry and Littleton, 1961). Most of the deposits are relatively thin (less than 15 feet thick) but locally they may be as much as 40 feet thick.

Alluvial deposits underlying the flood plains of the principal streams consist of clay, silt, sand, and gravel. Quaternary alluvium at the upper end of the Owl Creek drainage consists primarily of pebbles, cobbles, and boulders but becomes progressively finer downstream. Thickness of the alluvium ranges from a featheredge to as much as 38 feet, with an average of about 20 feet (Berry and Littleton,

1961).

Greybull River-Dry Creek Area

The Greybull River and Dry Creek flow eastward across the central part of the basin before their respective confluences with the Bighorn River near Greybull. Principal terrace deposits in this area include the Rim Terrace (YU Terrace of Mackin, 1937), Sunshine

Terrace (Emblem Surface of Mackin, 1937), and the Greybull Terrace.

These deposits are found principally north of the Greybull River and south of Dry Creek throughout the main reaches of both streams

(Plate 5) and consist predominantly of rounded to well-rounded pebbles and small cobbles which vary in composition from basalt and andesite to quartzite, chert, granite, and other rock types (Robinove and

Langford, 1963).

Deposits of the Rim Terrace are composed of poorly sorted rock debris that range in size from silt to small boulders. The deposits are predominantly subangular to rounded volcanic fragments derived from the Absaroka volcanic plateau to the west (Robinove and Langford, 1963).

The Rim Terrace deposits have a maximum width of 3-112 miles near the eastern edge of the YU Bench (Robinove and Langford, 1963).

Sediments comprising the Sunshine Terrace deposits are rounded, poorly sorted gravel, sand, and silt. Sunshine Terrace deposits are about 1 to 2 miles wide throughout most of their length and are exposed along Dry Creek where the terrace surface is roughly 110 to 225 feet above present-day flood plain.

The deposits underlying the Greybull Terrace are of the same type, size, and provenance as the other terrace deposits in the Greybull

River Valley. The deposits are about 15 feet thick throughout the

Greybull River area with a maximum thickness of 47 feet (Robinove and

Langford, 1963). Deposits are 10 to 40 feet above the present valley bottom and are as much as 2 miles wide in the area around Burlington.

Elsewhere, the deposits are generally less than I mile wide.

The flood plain alluvium in the Greybull River Valley is similar in composition to the higher terrace deposits and is as much as two miles wide in the area south of Burlington. These deposits are chiefly pebbles and small cobbles overlain by a thin veneer of sand and silt.

Robinove and Langford (1963) report that the thickness of the alluvium throughout the Greybull River Valley is generally less than 30 feet.

The alluvium of the Dry Creek Valley is composed primarily of sand and has much less gravel than the Greybull River Valley. The Dry Creek

Valley alluvium is probably not greater than 15 feet thick (Robinove and Langford, 1963). Cooley and Head (1979a) report that coarse volcanic debris from the Absaroka Range is present along the entire length of the Greybull River and, due to widespread distribution of the gravel, water is easily exchanged between the river and adjacent deposits.

Shoshone River Area

Ralston Terrace, Powell Terrace, and Cody Terrace are the three main terraces in the Shoshone River area. The deposits of these terraces are as much as 100 feet thick in places and consist mainly of well-rounded stream gravels with little fine material. Locally the cobbles are in a sandy matrix and in some instances are firmly cemented. Ralston Terrace deposits are composed largely of subangular to well-rounded cobbles of limestone and dolomite derived from Paleozoic formations and range in thickness from about four feet to more than

100 feet (Swenson and Swenson, 1957). Powell Terrace deposits consist mainly of rounded to sub-rounded cobbles of volcanic rocks mixed with very well-rounded quartzite and chert pebbles derived from

Paleozoic sedimentary rocks and the destruction of older terrace deposits (Swenson and Swenson, 1957). These gravel deposits are more than 50 feet thick at places near Cody and more than eight miles wide in the vicinity of Powell. The Cody Terrace lies 80 to 100 feet below Powell Terrace, is about two miles wide, and consists of 2 to 15 feet of gravel. Near Cody the deposits are very firmly cemented by calcareous material believed to be derived, in part, from springs (Swenson and Swenson, 1957). Surficial fine sand mantles the gravel deposits of the Cody Terrace and is more than 20 feet thick in places (Swenson and Swenson, 1957). Nowood River Area

Surficial deposits of the Quaternary aquifer in the Nowood River area consist of flood plain alluvium, terrace gravel, alluvial fan, pediment and landslide deposits. The flood plain alluvium and alluvial fan deposits are hydraulically connected (Cooley and Head, 1979b).

The flood plain alluvium, which is best developed along the Nowood

River and its main tributaries, includ'ing Paint Rock, Tensleep, Spring,

Otter, and Little Canyon creeks (Cooley and Head, 1979b), occurs in narrow bands adjoining the channel and ranges in width from about

500 feet along the Nowood River to as much as 3/4 mile along Tensleep

Creek (Cooley and Head, 1979b). Flood plain alluvium along the Nowood

River consists of thin layers of silty sand and clay containing considerable amounts of organic material. Rounded pebbles and cobbles consisting mainly of chert, quartzite, and other siliceous rocks occur as basal lenses, 5 to 11 feet thick, in the otherwise fine- grained deposits (Cooley and Head, 1979b). In general, the alluvium along Tensleep, Paint, and Medicine Lodge creeks consists mainly of pebbles and cobbles which occur as broad, multiple fill terraces that are commonly 3 to 8 feet above stream level.

The coarsest part of the alluvial aquifer in the Nowood River area is boulder-fan deposits which consist of large (up to 4 feet in diameter) granite and gneiss boulders. These deposits occur chiefly in the broad confluent valleys of Paint Rock and Medicine Lodge creeks about 4 miles northwest of Hyattville. Pediment deposits consisting of thin, discontinuous, fine-grained mixtures of sand and silt, with local lenticular beds of gravel, also occur in the Nowood River area, but are considered only a minor part of the alluvial aquifer. APPENDIX

CHEMICAL ANALYSES OF BIGHORN BASIN

GROUND WATERS SAMPLED BY WRRI TABLE C-1

CHEMICAL ANALYSES OF BIGHORN BASIN GROUND WATERS SAMPLED BY WRRI, JULY 1980

Location : 46/93-1 aa 49/100-13 bc 52/97-24 aa 53/101-1 dc 52/105-19 cc 52/107-21 db 49/100-34 51/96-18 bc Aquifer : Quaternary Quaternary Quaternary Quaternary Tertiary Tertiary Willwood/ Willwood/ Alluvium A1luvium Alluvium Alluvium Volcanics Volcanics Fort Union Fort Union

Field ~em~eraturel 10 11.5 17 15.5 11.5 12 13.5 13 Field pH 7.5 7.2 7 .O 8.4 7.1 6.5 7.1 - ~onductivity2 890 7 50 455 2 800 200 195 825 1100 Total Suspended 0.4 0.8 0.8 N.D. 0.4 0.4 0.4 0.8 solids3 Total Dissolved 7 36 544 44 2 2308 154 140 544 820 Solids Calcium 95 100 55 4 3 6 12 84 5 Magnesium 2 9 37 2 3 11 3 8 4 4 3 Sodium 98 39 51 775 4 4 2 9 59 288 Potassium 7 6 2 11 1 2 10 5 Bicarbonate 30 7 451 239 112 127 129 464 3 78 Carbonate 0 0 0 0 0 0 0 T Sulfate 264 124 9 6 1580 14 9 121 30 2 Chloride 16 2 19 192 4 4 6 12 Arsenic N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. Barium N.D. N.D. N.D. N.D. N.D. N.D. N .D. N.D. Cadmium N.D. N.D. N.D. N.D. N.D. N.D. N .D. N.D. Chromium N.D. N.D. N.D. N.D. N.D. N.D. N.D. N .D. Fluoride 0.84 0.50 0.61 0.40 0.55 0.44 0.54 3.16 Lead N.D. N.D. N.D. N .D. N .D. N.D. N.D. N.D. Mercury N.D. N.D. N.D. N .D. N .D. N.D. N.D. N.D. Nitrate-N N.D. N .D. N.D. N.D. N .D. N.D. N.D. N .D. Selenium N.D. N.D. N.D. N.D. N.D. N. D. N.D. N.D. Silver N.D. N .D. N.D. N .D. N.D. N.D. N.D. N.D. Uranium-U 0 0 .OO6 0.002 N. D. N.D. 3 8 0.011 N.D. 0.003 N.D. TABLE C-1 (continued)

Location : 54/100-2 ad 55/99-26 cd 56/96-19 dd 571102-21 ba 44187-8 ac 47/88-17 ac 50189-33 bd 47/88-12 dc Aquifer: Willwood / Willwood / Willwood / Willwood / Tensleep Tensleep Fort Union Fort Union Fort Union Fort Union Tensleep Madison

Field ~em~eraturel 12.1 13.4 Field pH 7.4 7.6 ~onduct ivit y 1250 525 Total Suspended N.D. N.D. solids Total Dissolved Solids Calcium 80 38 172 34 35 4 7 100 34 Magnesium 21 20 49 11 20 25 31 21 Sodium 58 102 94 91 1 5 13 5 Potassium 5 8 9 6 1 4 5 2 Bicarbonate 288 283 347 26 8 168 244 244 205 Carbonate 0 0 0 0 0 0 0 0 Sul fate 164 174 516 80 34 30 185 4 Chloride 8 10 20 6 4 5 10 4 Arsenic N.D. N.D. N.D. N.D. N. D. N .D. N.D. N.D. Barium N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. Cadmium N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. Chromium N.D. N.D. N .D. N.D. N. D. N.D. N.D. N.D. Fluoride 0.59 0.83 0.62 0.48 0.45 0.39 0.92 0.21 Lead N.D. N. D. N.D. N.D. N.D. N.D. N.D. N.D. Mercury N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. Nitrate-N N.D. 0.86 N. D. 0.46 N.D. N.D. N.D. N.D. Selenium N.D. N.D. N.D. N .D. N.D. N.D. N.D. N.D. Silver N.D. N.D. N.D. N.D. N.D. N .D. N.D. N.D. Uranium-U 0 N.D. 3 8 0 .OO4 0.010 0 .OO3 0 .OO3 N.D. N.D. 0.002

l~em~eraturein degrees Celsius. 4~.~.indicates not detected. Detection Lead : 0.05 mgll 2~onductivityat 68OF, in micromhos. limits for affected species are: Mercury: 0.001 mg/l Total suspended solids: 0.4 mg/1 Nitrate-N: 0.01 mg/l 3~emainingparameters in milligrams /l iter . Selenium: 0.01 mg/l Arsenic : 0.01 mg/l Barium : 0.05 mg/l Silver: 0.02 mg/l Cadmium : 0.01 mg/l Uranium-U308: 0.001 mg/l Chromium: 0.05 mg/1 5~ indicates trace amount present. APPENDIX D

LOCATION AND NUMBERING SYSTEM Locat ion-Numbering System

The location sites of the wells are designated by a numbering system based on the federal system of land subdivision.

The first number denotes the township, the second number denotes the range, and the third number denotes the section. One or more letters follow the section number and denote the location within the section. The section is divided into four quarters (160 acres) and lettered a, b, c, and d in a counterclockwise direction, beginning in the northeast quarter. Similarly, each quarter may be further divided into quarters (40 acres) and again into 10-acre tracts and lettered as before. The first letter following the section number denotes the quarter section; the second letter, if shown, denotes the quarter-quarter section; and the third letter denotes the quarter- quarter-quarter section, or 10-acre tract (Figure D-1) .

Figure D-1. Well identification system based on township-range subdivisions. VOLUME 11-B

OCCURRENCE AND CHARACTERISTICS OF

GROUND WATER IN THE BIGHORN BASIN, WYOMING

Robert Libra, Dale Doremus, Craig Goodwin

Proj ect Manager Craig Eisen

Water Resources Research Institute University of Wyoming

Report to

U.S. Environmental Protection Agency Contract Number G 008269-79 1

Project Officer Paul Osborne

June, 1981 LIST OF PLATES

1. Structural contour map of the Bighorn basin

2. Permitted domestic wells in the Bighorn basin

3. Total dissolved solids map of the Paleozoic aquifer system, Bighorn basin

4. Total dissolved solids map of the Upper Cretaceous- Tertiary aquifer system, Bighorn basin

5. Total dissolved solids map of the Quaternary aquifers, Bighorn basin