Scientific Investigations Report 2010−5075

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Bureau of Land Management

Geology, Geochemistry, and Geophysics of the Fry Canyon 

Uranium/Copper Project Site, Southeastern Utah—

Indications of Contaminant Migration

Geology, Geochemistry, and Geophysics 

of the Fry Canyon Uranium/Copper Project 

Site, Southeastern Utah—Indications of 

Contaminant Migration

By James K. Otton, Robert A. Zielinski, and Robert J. Horton

Prepared in cooperation with the Bureau of Land Management

Scientific Investigations Report 2010–5075

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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Suggested citation:

Otton, J.K., Zielinski, R.A., and Horton, R.J., 2010, Geology, geochemistry, and geophysics of the Fry Canyon uranium/

copper project site, southeastern Utah—Indications of contaminant migration: U.S. Geological Survey Scientific 

Investigations Report 2010–5075, 39 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Methods...........................................................................................................................................................3

Mapping..................................................................................................................................................3

Sampling.................................................................................................................................................3

Analyses.................................................................................................................................................3

Waters ...........................................................................................................................................3

Sediments......................................................................................................................................5

Electromagnetic Survey ......................................................................................................................5

Direct-Current Electrical Resistivity Survey............................................................................5

Survey Instrumentation ..............................................................................................................6

Resistivity Data Processing .......................................................................................................7

Geology, Geophysics, and Geochemistry ..................................................................................................7

Stratigraphy ...........................................................................................................................................7

Cross Sections—Geologic Relations and Interpretations...........................................................11

Direct-Current Resistivity Survey.....................................................................................................13

Interpretation..............................................................................................................................14

Line FC–1 ............................................................................................................................14

Line FC–3 ............................................................................................................................17

Line FC–2 ............................................................................................................................17

Line FC–4 ............................................................................................................................18

Structure...............................................................................................................................................18

General Chemical Character of Water............................................................................................19

Aqueous Geochemistry of Uranium.................................................................................................22

Spatial Distribution of Dissolved Uranium......................................................................................23

Uranium Isotopes................................................................................................................................23

Sulfur Isotopes ....................................................................................................................................25

Sediment Chemistry and Mineralogy ..............................................................................................26

Summary and Conclusions ........................................................................................................................29

Acknowledgments.......................................................................................................................................31

References Cited..........................................................................................................................................31

Appendix 1. Description of disturbed areas ........................................................................................35

Appendix 2. Apparent resistivity pseudosections and inversion results........................................37

Figures

1. Maps showing locations of the Fry Canyon project site in San Juan County, 

southeastern Utah, and areas of geologic mapping...............................................................2

2. Map of a portion of Fry Canyon, southeastern Utah, showing the location 

of the Fry Canyon project site and locations where surface water and 

groundwater and stream sediments were collected .............................................................5

3. Location of dc resistivity lines FC1–4 at the Fry Canyon project site...................................6

4. Geologic map of the ranch area north of the Fry Canyon project site.................................8

5. Geologic map of the Fry Canyon project site and vicinity......................................................9
iv

6. Geologic map of the Fry Spring area south of the Fry Canyon project site. .....................10

7. Cross section A–A’ across the modern stream channel of Fry Creek and 

the bench to the south, at the position of the berm between ponds 4 and 5.......................12

8. Cross section B–B’ across the valley floor of Fry Creek north of the 

Fry Canyon project site at the location of a washed-out road............................................12

9. Cross section C–C’ across the valley floor of Fry Creek at the location 

of the cottonwood tree well field .............................................................................................13

10. Direct-current resistivity profile for Fry Canyon line FC–1...................................................14

11. Direct-current resistivity profile for Fry Canyon line FC–3...................................................15

12. Direct-current resistivity profile for Fry Canyon line FC–2...................................................15

13. Direct-current resistivity profile for Fry Canyon line FC–4...................................................16

14. Pie diagrams showing the relative percentages of major cations and anions 

(on a milliequivalent basis) in well W15 from the center of the contaminant 

plume and well W16, which is more representative of other contaminated 

water samples collected in this study.....................................................................................21

15. Plot showing the relative abundance of major dissolved U(VI) species as a 

function of pH in waters of this study......................................................................................22

16. Plot showing degree of saturation of sampled waters with respect to a variety 

of minerals, including uranium minerals.................................................................................23

17. Plot of dissolved uranium concentration as a function of sampling-site location 

 along the main stem of Fry Creek............................................................................................23

18. Photograph of view upstream from water-sampling site W1 in Fry Creek .......................24

19. Plot of 234U/238U activity ratio (AR) of water as a function of sampling-site location 

along the main stem of Fry Creek.............................................................................................24

20. Plot of 234U/238U activity ratio (AR) compared to dissolved uranium concentration 

in waters of this study................................................................................................................25

21. Plot of δ34S of dissolved sulfate compared to dissolved sulfate concentration 

in waters of this study................................................................................................................25

22. Photographs of variably altered pyrite and chalcopyrite grains in the magnetic 

fraction of the 60–120 mesh size fraction of tailings sample T1 (A–F ), and in 

downstream sediment S5 (G–K), and S6 (L)...........................................................................27

23. Backscatter electron image (BSE) and corresponding X-ray intensity maps for 

copper, sulfur, and iron for a portion (8 square millimeters) of thin section T1 

containing magnetic minerals from the tailings location.....................................................29

24. Map of the Fry Canyon project study area showing modern channel and 

possible position of the paleochannel along the floor of Fry Creek...................................30
v

Appendix Figures

25. Supporting information for direct-current resistivity profile FC–1 .....................................37

26. Supporting information for direct-current resistivity profile FC–3 .....................................38

27. Supporting information for direct-current resistivity profile FC–2 .....................................38

28. Supporting information for direct-current resistivity profile FC–4 .....................................39

Tables

1. UTM coordinates of Fry Canyon direct-current resistivity profiles......................................7

2. Chemical and isotopic composition of surface water, seeps, springs, and wells, 

Fry Canyon, Utah.........................................................................................................................19

3. Concentrations of selected trace elements (μg/g) in the 60–120 mesh size fraction 

of tailings and stream sediments, Fry Canyon, Utah.............................................................26

Abstract

The Fry Canyon uranium/copper project site in San Juan 

County, southeastern Utah, was affected by the historical 

(1957–68) processing of uranium and copper-uranium ores. Relict 

uranium tailings and related ponds, and a large copper heap-leach 

pile at the site represent point sources of uranium and copper 

to local soils, surface water, and groundwater. This study was 

designed to establish the nature, extent, and pathways of contaminant dispersion. The methods used in this study are applicable at 

other sites of uranium mining, milling, or processing.

The uranium tailings and associated ponds sit on a bench 

that is as much as 4.25 meters above the level of the adjacent 

modern channel of Fry Creek. The copper heap leach pile sits 

on bedrock just south of this bench. Contaminated groundwater 

from the ponds and other nearby sites moves downvalley and 

enters the modern alluvium of adjacent Fry Creek, its surface 

water, and also a broader, deeper paleochannel that underlies 

the modern creek channel and adjacent benches and stream 

terraces. The northern extent of contaminated groundwater is 

uncertain from geochemical data beyond an area of monitoring 

wells about 300 meters north of the site. Contaminated surface 

water extends to the State highway bridge. Some uraniumcontaminated groundwater may also enter underlying bedrock 

of the Permian Cedar Mesa Sandstone along fracture zones.

Four dc-resistivity surveys perpendicular to the valley trend 

were run across the channel and its adjacent stream terraces 

north of the heap-leach pile and ponds. Two surveys were done 

in a small field of monitoring wells and two in areas untested 

by borings to the north of the well field. Bedrock intercepts, salt 

distribution, and lithologic information from the wells and surface 

observations in the well field aided interpretation of the geophysical profiles there and allowed interpretation of the two profiles 

not tested by wells. The geophysical data for the two profiles to 

the north of the well field suggest that the paleochannel persists 

at least 900 m to the north of the heap leach and pond sites. 

Contamination of groundwater beneath the stream terraces may 

extend at least that far.

Fry Creek surface water (six samples), seeps and springs 

(six samples), and wells (eight samples) were collected during 

a dry period of April 16–19, 2007. The most uranium-rich 

(18.7 milligrams per liter) well water on the site displays distinctive Ca-Mg-SO4

-dominant chemistry indicating the legacy 

of heap leaching copper-uranium ores with sulfuric acid. This 

same water has strongly negative δ34S of sulfate (–13.3 per mil) 

compared to most local waters of –2.4 to –5.4 per mil. Dissolved uranium species in all sampled waters are dominantly 

U(VI)-carbonate complexes. All waters are undersaturated with 

respect to U(VI) minerals. The average 234U/238U activity ratio 

(AR) in four well waters from the site (0.939±0.011) is different 

from that of seven upstream waters (1.235±0.069). This isotopic 

contrast permits quantitative estimates of mixing of site-derived 

uranium with natural uranium in waters collected downstream. 

At the time of sampling, uranium in downstream surface water 

was mostly (about 67 percent) site-derived and subject to further 

concentration by evaporation. Three monitoring wells located 

approximately 0.4 kilometer downstream contained dominantly 

(78–87 percent) site-derived uranium. Distinctive particles of 

chalcopyrite (CuFeS) and variably weathered pyrite (FeS2) are 

present in tailings at the stream edge on the site and are identified 

in stream sediments 1.3 kilometers downstream, based on inspection of polished grain mounts of magnetic mineral separates.

Introduction

Uranium ore upgrading (1957–1960) and sulfuric acid 

heap leaching of copper-uranium ores (1963–1968) have contaminated water and land at the Fry Canyon uranium/copper 

project site in San Juan County, southeastern Utah (fig. 1). The 

site is managed by the Bureau of Land Management (BLM), 

which is conducting site investigations to support final plans 

for site remediation. A plume of contaminated groundwater 

beneath the site contains elevated concentrations of dissolved 

uranium (1,000–20,000 micrograms per liter [μg/L]), copper 

(<4–20 μg/L), and sulfate (1,200–1,900 milligrams per liter 

Geology, Geochemistry, and Geophysics of the Fry Canyon 

Uranium/Copper Project Site, Southeastern Utah—

Indications of Contaminant Migration

By James K. Otton, Robert A. Zielinski, and Robert J. Horton
2 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

Figure 1. Maps showing locations of the Fry Canyon project site in San Juan County, southeastern Utah, and areas of geologic 

mapping (figs. 4–6).

COLORADO

ARIZONA NEW MEXICO

UTAH

WYOMING

Salt Lake City

Fry Canyon Blanding

Kayenta-Wingate

rim cliff

Fry Creek

Figure 4

Figure 5

Figure 6

Fry Canyon

project site

Ranch

Fry Spring

N

Fry Canyon 

Lodge Moenkopi cliff

15

70

80

SH95

SH95

Radium King Road

Fry Creek

0 0.5 1 MILE

0 0.5 1 KILOMETER
Methods 3

[mg/L]), and well waters 0.5 km downgradient from the site 

contain greater than 100 μg/L uranium (Wilkowski and others, 

2002). Features on the site include an abandoned copper heapleach pile and ponds and associated uranium tailings that contain uranium, copper, and other elements subject to mobilization 

by wind and water. Field studies by the U.S. Geological Survey 

(USGS) during 1996–2006 investigated the effectiveness of 

several prototype permeable reactive barriers (PRB) to treat the 

contaminant plume (Naftz and others, 1999, 2000, 2002, 2006).

The purpose of this report is to present additional geologic, chemical, geophysical, mineralogic, and isotopic data 

that indicate some of the mechanisms and pathways for offsite 

dispersion of contaminants and the effects on the surrounding environment. The new data include (1) geologic maps and 

cross sections that show areas upstream and downstream from 

the site and identify geologic controls on offsite movement of 

groundwater, (2) geophysical data that define older channel 

gravels that serve as reservoirs for contaminated groundwater 

and pathways for its movement downvalley, (3) chemical data 

that indicate the aqueous geochemistry of uranium in local 

waters and possible chemical controls on uranium mobility, (4) isotopic data for dissolved uranium that permit more 

accurate and sensitive tracing of site-derived uranium in local 

waters, and (5) chemical and mineralogical observations of 

stream sediments that permit tracing of site-derived sulfide 

minerals in the streambed of Fry Creek.

Methods

Mapping

Three partly overlapping aerial photographs derived from 

Google Earth were used as base maps for geologic mapping. 

Locations of the three mapped areas, each of which covered a 

tract approximately 520 m east-west by 450 m north-south, are 

shown in figure 1. They are (1) the area around a ranch north 

of the project site, (2) the project site (shaded area, fig. 1, also 

referred to as the ore-processing site), and (3) the area around 

Fry Spring south of the project site. The photographs have not 

been georeferenced, so there is some scale distortion near the 

margins of each image. Three cross sections were drawn across 

Fry Creek at selected locations near the project site by using a 

tape measure and hand level to supplement the geologic maps 

in showing the detailed geologic relations at and near the project 

site. Lithologic data from monitoring wells were used in two of 

the cross sections.

Sampling

Twenty water samples and 9 sediment samples (fig. 2) 

were collected in the drainage of Fry Creek during a dry 

period spanning April 16–19, 2007. This sampling provided 

a snapshot of conditions presumed to be typical for this small 

first-order stream located in a semiarid environment. In the 

absence of recent rainfall, normal streamflow of less than 

2.8 liters per second (L/s) is largely sustained by returns of 

groundwater as seeps and springs (Wilkowski and others, 

2002). Sampling within and adjacent to Fry Creek included 

locations upstream from the Fry Canyon project site and 

successive downstream locations over a total stream reach of 

approximately 4 km (fig. 2). Water samples included the main 

channel of Fry Creek (six samples), springs and seeps (six 

samples), and shallow (less than 7 m) plume wells and monitoring wells (eight samples). Wells included one upstream 

“background” well near Fry Spring (W19), four plume wells 

within the pond and tailings area on the bench (W15–W18), 

and three monitoring wells on a stream terrace downvalley 

from the project site (W13, W14, W20). The streamflow was 

continuous from the uppermost sampling site (W1) to a sampling site approximately 1.3 km downstream from the project 

site (W10). Two other stream samples (W11, W12) were collected farther downstream where surface flow reemerged from 

beneath a dry streambed.

 Water temperature, pH, and specific conductance were 

measured at the time of sampling. An additional 250 milliliters (mL) of each water sample was collected in a field-rinsed 

polyethylene bottle and placed under refrigeration for transport to the laboratory. Wells were sampled using a peristaltic 

pump, and water was collected only after stabilization of 

temperature and specific conductance. This required pumping 

of approximately 10 L of water before sampling.

Stream sediments (seven samples) were collected at locations that generally corresponded to locations of surface-water 

samples (fig. 2, inset). At each location, 2–3 kilograms (kg) of 

dominantly sand- to silt-sized moist sediment were collected 

by combining samples from several locations within the active 

stream channel. Two grab samples of sand- to silt-sized tailings were collected from a steep slope of tailings adjacent to 

Fry Creek (T1, T2, fig. 2, inset). The nose of this tailings slope 

is submerged and potentially mobilized by stream waters during intermittent flash floods that can increase stream discharge 

to over 8.5 cubic meters per second (m3/s) (Wilkowski and 

others, 2002). Sediments were collected with plastic scoops 

and stored in sealed polyethylene bags.

Analyses

Waters

Water samples were delivered to USGS laboratories in 

Denver and filtered through cellulose acetate filter membranes 

with 0.45-micrometer (mm) openings, under pressure from 

nitrogen gas. Approximately 60 mL of each sample was acidified to pH<2 with high-purity nitric acid and submitted for 

analyses of major dissolved cations by inductively coupled 

plasma–atomic emission spectrometry (ICP–AES), and for 

analyses of selected minor and trace elements by inductively 

coupled plasma–mass spectrometry (ICP–MS) (Briggs, 2002; 

Lamothe and others, 2002). Remaining amounts of acidified waters were used for determinations of uranium isotopic 

composition. Filtered but unacidified portions of each water 
4 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

Fry Canyon 

Lodge

Radium King Road

Ranch

Fry Spring

W 12

W 11

W 10

W 9

W 14

W 13

W 20 W 18

W 16

W 8

W 17

W 15

W 19

W 7

W 4

W 5

W 3

W 2

W 1

W 6

S 7

S 6

S 5

S 4

S 3

S 2 T 2

T 1

S 1

Radium King Road

Ranch

Fry Canyon 

tailings site

Fry Canyon 

tailings site

Fry Canyon 

Lodge

Radium King Road

Ranch

Fry Spring

W 12

W 11

W 10

W 9

W 14

W 13

W 20 W 18

W 16

W 8

W 17

W 15

W 19

W 7

W 4

W 5

W 3

W 2

W 1

W 6

S 7

S 6

S 5

S 4

S 1

S 3

S 2 T 2

T 1

T 1

S 1

Radium King Road

Ranch

Fry Canyon 

tailings site

Fry Canyon 

tailings site

0 500 METERS

0

250

1,000 2,000 FEET

0 300 METERS

0 1,000 FEET

Surface water

EXPLANATION

Seeps and springs

Wells

Stream sediment

Tailings

N SH95

SH95
Methods 5

sample were used for determination of carbonate alkalinity by 

titration with standard acid, for determination of other major 

dissolved anions by ion chromatography (IC), and for measurements of sulfur isotope composition. Estimated accuracy 

and precision of the chemical analyses, expressed as relative 

standard deviation (RSD), were generally better than 5 percent 

for alkalinity and major cations and anions and 10 percent for 

minor and trace elements.

The concentration and isotopic composition of dissolved 

uranium was determined by passing a 10-mL aliquot of acidified 

water through a column of uranium-specific resin (UTEVA®) 

and analyzing the eluted uranium by sector field ICP–MS. The 

isotopic ratio of interest in this study is the 234U/238U activity 

ratio (AR). This ratio of (radio)activity concentrations is calculated from the measured mass ratio of the two isotopes. Mass 

ratios are first corrected for instrument blanks and instrumentbased mass discrimination. Estimated accuracy and precision 

of the technique based on replicate measurements of standards 

is ±5 percent (RSD) for uranium concentration and better than 

±1 percent for AR values.

The concentration and isotopic composition of dissolved 

sulfur (as sulfate) was determined by (1) concentrating dissolved sulfate in a precipitate of barium sulfate and (2) combusting the barium sulfate in an elemental analyzer and directing the produced SO2

 gas into an in-line continuous-flow mass 

spectrometer. The sulfur isotopic composition is reported as a 

d34S value, calculated as follows:

d34S (in per mil, ‰) = (Rsample/Rstandard –1) × 1,000

where

R is the atomic 34S/32S ratio and the standard is Vienna 

Canyon Diablo troilite (V–CDT).

Accuracy and precision of the measurements was ±0.2 per mil 

based on multiple determinations of sulfur isotopic standards 

(NBS–127, IAEA–S–5, and IAEA–S–6).

Sediments

Sediments were air-dried at 40°C and then passed 

through a stainless steel sieve with 2-millimeter (mm) openings, with material coarser than 2 mm discarded. Approximately 500 g of each sediment was passed though a series of 

stainless steel sieves to produce the following size fractions: 

2.0–0.25 mm (10–60 mesh), 0.25–0.125 mm (60–120 mesh), 

and <0.125 mm (<120 mesh). The 60–120 mesh size fraction 

of each sample was observed under a binocular microscope 

to initially characterize constituent minerals. Approximately 

10 g of the 60–120 mesh fraction was ground to a fine powder 

in a ceramic ball mill, and 0.1-g aliquots were dissolved in a 

mixture of mineral acids. The acid digests were analyzed for 

copper, uranium, and other trace elements by ICP–MS.

Approximately 35 g of each 60–120 mesh fraction was 

screened with a hand magnet to remove (rare) magnetite and 

then passed through a Franz isodynamic magnetic separator 

(1.7 amperes, 15-degree tilt angle) to concentrate other magnetic minerals, including copper sulfide minerals (Rosenblum 

and Brownfield, 1999). Numerous grains of each magnetic 

concentrate were mounted as a closely packed assemblage 

on a 16- by 16-mm area of a polished thin section. The entire 

area of each thin section was viewed in 1- by 1-mm area 

increments at 160 times magnification under reflected light 

illumination, using oil-immersion objectives. The total number 

of highly reflective and variably altered sulfide grains on each 

thin section was recorded.

The thin section of tailings sample T1 was also scanned 

for grains containing high concentrations of copper using a 

JEOL JXA 8900 electron microprobe operating at 15-kilovolt 

accelerating voltage, 50-nanoampere current. Beam diameter 

was 10 mm. Backscatter electron image (BEI) mode was used 

to identify (brightest) grains containing high concentrations 

of heavy elements. Wavelength dispersive X-ray intensity 

maps of copper, iron, and sulfur were also acquired to distinguish copper-rich minerals from pyrite and iron oxides. 

Each map area covered approximately 8 mm2 and consisted 

of 800 × 800 pixels.

Electromagnetic Survey

Direct-Current Electrical Resistivity Survey

Direct-current (dc) resistivity surveys were conducted 

across the Fry Canyon stream channel. The purpose of the Fry 

Canyon resistivity surveys was to help delineate the stream’s 

bedrock channel downgradient from the mill site. Parts of the 

bedrock channel may coincide with the modern stream channel, 

but parts may be buried underneath adjacent benches and stream 

terraces. The sediment cover on the benches and stream terraces 

obscures the location of the bedrock channel, which may be 

a significant groundwater conduit for contaminant migration 

below the site. The basic premise for using the dc-resistivity 

method is that a resistivity contrast should exist between the 

surficial unconsolidated sediment and the underlying bedrock.

Resistivity is the property of a material to resist the 

flow of electric current. Resistivity is the inverse of electrical 

conductivity. Resistivity units are ohm-meters (ohm-m). The 

resistivity of rock and sediment is dependent on several factors 

including the amount of water present, porosity, the amount 

of total dissolved solids (TDS) in pore water, and mineral 

composition of the sediment or bedrock. The amount and TDS 

of pore water are typically the dominant factors that determine 

geologic media’s resistivity. All other factors being equal, dry 

Figure 2 (facing page). Map of a portion of Fry Canyon, 

southeastern Utah, showing the location of the Fry Canyon project 

site and locations where surface water and groundwater and 

stream sediments (S1–7, inset) were collected.
6 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

rock is more resistive than saturated rock, and rock saturated 

with low-TDS water is more resistive than rock saturated 

with high-TDS water. The presence of electrically conductive 

minerals, such as clays (that is, montmorillonite) and salts, 

typically results in a lower measured resistivity.

To determine if detectable resistivity contrasts were present 

at the site, three vertical electrical soundings (VES) were first 

conducted (Robert Horton, unpub. data, 2007). The VES data 

indicated conductive over resistive sections, interpreted as wet, 

often saline, sediment over variably saturated bedrock. Moderate 

resistivity contrasts observed in the VES data suggested that dcresistivity profiling could delineate the sediment/bedrock contact.

Based on the encouraging results of the VES measurements, four detailed dc-resistivity profiles were planned and 

conducted across the stream valley in areas suspected of 

having a buried bedrock channel based on the geomorphology 

and drillhole intercepts of bedrock on terraces that were below 

bedrock in the modern stream channel. Figure 3 shows the 

locations of the resistivity profiles.

Survey Instrumentation

For this project, two-dimensional (2–D) dc-resistivityprofile data were collected using a multielectrode Advanced 

Geosciences, Inc., SuperSting R8 resistivity/IP system. The 

standard survey setup was to lay out up to 100 stainless steel 

electrodes 1 m apart along a relatively straight line. The electrodes, which are similar to tent stakes, are pounded into the 

ground then connected to cables attached to the R8 transmitter/

receiver unit. The electrodes were watered with saltwater to 

FC-4

FC-2 FC-3 FC-1

Cottonwood tree

Fry Canyon site

Heap-leach pile 

Uranium 

 processing

 pits

Fry Creek

Fry Creek

Tailings

sample site

FC-4

FC-2 FC-3 FC-1

Cottonwood tree

Fry Canyon site

Heap-leach pile 

Uranium 

 processing

 pits

Fry Creek

Fry Creek

Tailings

sample site

N

0 100 METERS

0 500 FEET

Figure 3. Location of dc resistivity lines FC1–4 at the Fry Canyon project site (shown as gray square in fig. 1).
Geology, Geophysics, and Geochemistry 7

increase their electrical contact with the ground. The R8 unit 

was programmed to transmit a 1,000-mA (milliampere) pulse. 

For each measurement, two readings were made, with the average value being used to calculate the apparent resistivity.

The resistivity data presented here were collected using 

the inverse Schlumberger array. This array type was chosen 

because it has good signal-to-noise characteristics relative to 

other array types (that is, dipole-dipole). To measure the entire 

profile, the R8 unit sequentially switches the transmitter and 

receiver electrodes along the survey line by following instructions in a command file. When the R8 finishes collecting data 

from the existing electrodes, the profile can be extended by 

moving “used” electrodes from the start of the line to new 

positions beyond the end of the line. This technique, known 

as “roll along,” allows for the collection of data along a long, 

continuous profile. Line 2 used this roll-along technique to 

extend the line to 128 m.

To determine the position and elevation of the electrodes, 

the resistivity lines were surveyed using a Trimble R8 global 

positioning system (GPS). For this survey, the average relative 

horizontal precision of the GPS locations is 0.008 m (range 

0.004–0.031 m), whereas the average relative vertical precision 

is 0.014 m (range 0.008–0.069 m). Table 1 gives the starting and 

ending GPS position of each line in UTM, zone 12 coordinates.

Resistivity Data Processing

The resistivity data were processed using the computer 

program EarthImager 2D (Advanced Geosciences, Inc., 2003). 

The program is a 2–D inversion routine that takes the observed 

apparent resistivity data and produces 2–D cross sections that 

show “true” resistivity as a function of depth. These 2–D, 

topography-corrected resistivity cross sections are the basis 

for the subsurface interpretations.

For each inversion, two data files are used including the 

observed apparent-resistivity data file and a terrain file containing position and elevation data. Using the 2–D geometry of 

the survey line, the inversion minimizes the root mean square 

(RMS) error between the observed apparent resistivity and the 

resistivity calculated from the inverted model. To minimize the 

RMS error, sequential inversions were run. After each inversion, 

poorly fit data points are identified and removed on the basis of 

the percentage misfit value between the measured and calculated apparent resistivity. Typically, the data were sequentially 

inverted until the RMS error was less than 10 percent.

It is important to note that the resistivity data were collected in three-dimensional (3–D) space. If subsurface 3–D 

heterogeneities are present, the 2–D interpretation may contain 

errors in the location and size of anomalies. The magnitude of 

these errors depends on the distance the 3–D heterogeneities 

are offset from the survey line. The 3–D errors decrease as the 

distance from the line increases.

Geology, Geophysics, 

and Geochemistry

Stratigraphy

The geology of the site is characterized by bedrock composed of well-consolidated sandstone, siltstone, and mudstone 

of the Cedar Mesa Sandstone Member of the Cutler Formation 

(hereinafter referred to as the “Cedar Mesa sandstone”) of 

Permian age (Pcc and Pcb in figs. 4–6; Thaden and others, 

1964). Sandstone dominates and forms thick, stacked beds 

composed of crossbedded sandstone that were deposited during the Permian in a large dune field. Interbedded with these 

sandstones are thinner siltstones and mudstones formed by 

sediment deposited in interdune low areas. The thin siltstone 

and mudstone beds tend to weather readily; thus, the thicker 

sandstone beds form stairstepped ledges that extend away 

from Fry Creek up the valley slope to the contact with the 

overlying Organ Rock Member of the Cutler Formation (see 

bedrock ledges exposed in the minimally disturbed outcrop 

area southeast of the ore-processing site, dash-dot lines in the 

map unit Pcc southeast of the area labeled “d” in fig. 5). Along 

the stream channel and in a few upland areas, the sandstone 

forms “balds” almost completely devoid of vegetation, eolian 

sand, colluvium, or alluvium (Pcb in figs. 4–6). The map unit 

descriptor Pcc is used wherever the covering of surficial sediments is thin and sandstone is exposed almost continuously.

Along the active stream channel, cutbank cliffs have 

formed locally to expose basal stratified gravels that vary from 

well-sorted granule and pebble gravel to poorly sorted boulder 

gravel containing sandstone boulders as much as 1.5–3.0 m 

across; exposures are too limited, however, for the gravels to 

be mapped as a separate unit. These gravels contain mixed 

subangular to well-rounded clasts, eroded from sedimentary 

rocks in the Fry Creek drainage basin. Because of their proximity to the flowing stream channel, the clasts are commonly 

coated with soluble salts (probably sulfate salts) and also 

exhibit imbrications, which indicates a flow direction similar 

to the modern stream channel.

Table 1. UTM coordinates of Fry Canyon direct-current 

resistivity profiles.

[m, meters]

Line/Position UTM

Northing

UTM

Easting

Elevation

(meters)

FC–1 0m 4163734.689 576129.146 1,615.655

FC–1 100m 4163832.334 576131.525 1,611.198

FC–2 0m 4163833.353 575876.864 1,609.516

FC–2 128m 4163918.701 575946.202 1,614.469

FC–3 0m 4163750.790 576126.920 1,618.020

FC–3 64m 4163810.939 576122.667 1,613.233

FC–4 0m 4164221.329 575789.047 1,612.621

FC–4 100m 4164272.514 575871.901 1,603.650
8 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

Figure 4. Geologic map of the ranch area north of the Fry Canyon project site. Solid rectangles indicate ranch buildings.

N

Pcb

Qal

Pcc

Pcc

w

w

Qal

Pcb Qec

Qeb

Qeb

Pcb

Pcc

Qoal

Qal

Pcb

Qal

Qal

Pcb

Pcc

ps

Qe

Qe

Qe

Qe

Qal

Qec

Qec

Qec

Qec

Pcc

Pcc

Pcc

Pcc

Pcc

Qec

Ore

Ore

Pcb Qec

Qec

Pcc

Pcc

d

d

Qal2

Pcc

Qec

Pcc

Qec

Qec

Qec

Qec

Pcc

Ore

Ore

Pcc

Qeb Pcc

Qal

mer

b

rh

cs

Qal

ps

d

w

rh

cs

b

mer

Radium King

road (gravel)

EXPLANATION

Sandstone ledges

Large cottonwood tree

Road

Gully trace

Ponded sediment

Disturbed areas

Ponded water (4/2007)

Ranch house

Car shed

Barn

Main entry road to ranch Fence

Fry Creek

Fry Creek

Cedar Mesa Sandstone Member of the Permian Cutler Fm.; 

 Pcb, distinctive bald outcrop areas

Quaternary to Holocene eolian sand and colluvium;

 Qeb, areas where unit forms a bench along Fry Creek

Recent alluvial terraces 2–5 ft above modern channel

Recent alluvium

Quaternary to Holocene eolian sand

0 100 METERS

0 100 200 300 400

20 40 60 80

500 FEET

Qal2

Qal2

Qal2

Pcb

Qal2

Pcb

Qal2

Qal2

Qe

Qec, Qeb

Pcc, Pcb

Qal2

Quaternary to Recent older alluvium with dissected

 eolian sand surface layer

Qoal
Geology, Geophysics, and Geochemistry 9

Figure 5. Geologic map of the Fry Canyon project site (colored area) and vicinity. The locations of cross sections A–A‘, 

B–B‘, and C–C‘ are shown. PRB, location of the permeable reactive barrier. Numbers indicate uranium waste ponds.

B'

C

C'

A

A'

B

Qec

Qec

Qec

Pcc

Pcc

Pcc

Pcc

ss

Ore

Ore

Ore

d

Pcc

9

Pcb

r

Pcc

Qec

Pcc

ps

d

d

hlp

hlp

ss

ss

d

ss

hlp

d

Qec Qeb

Qeb

Qeb

Qeb

1

2

3

4

5

6

Pcb Pcc

Pcc

Pcc

d

d

Pcc

d

Ore

piles

Ore

f

f

d

Pcb

Pcb

Qeb

m

d

8

Pcb

cs

Pcb

Pcc

Pcb

Qeb

Qal Qec

Qal

Qeb Pcb

Qeb

Qal

Qal

Qal2

Qeb

t

j

Pcc

f

PRB

Qe

7

f

d

s

Qal2

Qal2

Fry Creek

EXPLANATION

Cedar Mesa Sandstone Member of the Permian Cutler Fm.; 

 Pcb, distinctive bald outcrop areas

Quaternary to Holocene eolian sand and colluvium;

 Qeb, areas where unit forms a bench along Fry Creek

Recent alluvial terraces 2–5 ft above modern channel

Recent alluvium

Quaternary to Holocene eolian sand

d

f

ps

cs

ss

t

r

hlp

j

m

s

Disturbed areas

Foundations

Ponded sediment

“Cowboy” shack

Sandstone exposures 

 in disturbed areas

Trench

Sandstone rubble

Heap-leach pile

Junk pile

Rusted metal scrap

Slime pile

Pcc, Pcb

Qec, Qeb

Qal

7 Pits in disturbed area (numbered)

Sandstone ledges

Large cottonwood tree

Road

Gully trace

Outwash from pile

Qe

Cross-section location

Qal2

0 100 METERS

0 100 200 300 400

20 40 60 80

500 FEET

N
10 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

Figure 6. Geologic map of the Fry Spring area south of the Fry Canyon project site.

Pcc

Pcc

Pcc

Pcc

Pcc

Qec

Qec

Pcc

Qeb

Pcc

Qal

d

Pcc

alk

alk

Qeb

Qec

Qoal

Qal2

Qeb

Pcb

Qal

Pcb

Ore pile

Badland

topography

Pcc

Qal2

Qal2

FS

Pcb

Pcc

Pit

Fry Creek

Fry Creek

Qal

Pcb

w

Pcb

t

Cedar Mesa Sandstone Member of the Permian Cutler Fm.; 

 Pcb, distinctive bald outcrop areas

Quaternary to Holocene eolian sand and colluvium;

 Qeb, areas where unit forms a bench along Fry Creek

Recent alluvial terraces 2–5 ft above modern channel

Recent alluvium

Quaternary to Recent older alluvium with dissected

 eolian sand surface layer

alk

FS Fry Spring

Trench

Alkali soil area

Water pool (4/2007)

Disturbed area

Pcc, Pcb

Qec, Qeb

Qal

t Pit

d Sandstone ledges

w Road

Gully or stream trace

Qoal

Qal2

EXPLANATION

0 100 METERS

0 100 200 300 400

20 40 60 80

500 FEET

N
Geology, Geophysics, and Geochemistry 11

Overlying the sandstone are unconsolidated, reddishbrown, eolian sand and silty sand that contain lenses of colluvium composed largely of clasts of the Cedar Mesa sandstone 

mixed with reworked eolian sand (map unit Qec). Along the 

stream, these deposits overlie and intertongue with the basal 

gravels; they are also well exposed in the cutbank cliffs previously mentioned. The reddish-brown color contrasts with the 

white to gray colors of the Cedar Mesa sandstone. The map 

unit symbol Qec is used where these deposits occur in an 

upland setting, whereas Qeb is the symbol designation along 

the Fry Creek stream channel, where the unit forms a bench 

3.7–5.5 m above the present-day stream channel (figs. 4–6). 

However, it should not be inferred that these deposits were 

stream deposited; rather, they were likely deposited by eolian 

and slope-wash processes without streamflow. In upland areas, 

Qec is mapped where it covers sandstone bedrock, but ledges 

of sandstone protrude through the sands in places, as shown in 

figures 4–6. The exposed maximum thickness of Qec is about 

4.6 m, which is in the large mapped area of Qec west of Fry 

Creek in the southern part of figure 6. Along some gully exposures in this area, thin lenses of alluvium are present in Qec. 

Also in this area, Qec contains patches of alkali soils (“alk,” 

fig. 6), which are coated with surface salts (probably sulfate 

salts) and characterized by low, hummocky topography that 

resembles badlands (marked in fig. 6).

Alluvium has been deposited along most of the length of 

the active Fry Creek stream channel (Qal in figs. 4–6), except 

where sandstone bedrock is exposed. The alluvium is composed of sand to coarse, sandy, boulder gravel. Some sandstone boulders as large as 1.5–3.0 m across protrude through 

the alluvium. These boulders could be eroded from the very 

coarse boulder gravel layers present locally or from the local 

sandstone bedrock exposures. Clasts in the active alluvium 

are representative of most of the units exposed in the local 

drainage basin.

At a distance of 0.6–1.5 m above the active channel are 

low stream terraces subjected periodically to flooding (Qal2, 

figs. 4–6). Higher stream terraces, such as the one near the cottonwood tree on the eastern edge of figure 4, have eolian sand 

deposited on them. Another stream terrace, in the southeastern part of figure 6, has a thick, gently dissected eolian sand 

covering the alluvium that is mapped as older alluvium (Qoal, 

fig. 6); it is distinguished from unit Qal2 immediately west of 

the creek by being topographically higher and from unit Qeb 

120–165 m to the north because the surface of the stream terrace is much lower and less dissected than the bench underlain 

by Qeb. It seems likely that floodwaters have seldom swept 

across this stream terrace. Another area of Qoal occurs on 

the west side of Fry Creek north of the ranch (fig. 4). It lies 

topgraphically about 3 m above an adjacent stream terrace 

underlain by Qal2.

Eolian sand units (Qe), mapped separately in four areas 

in figure 4, do not contain interbedded colluvium lenses in 

the limited exposures examined by the author, and in one area 

there are small dune features.

Cross Sections—Geologic Relations 

and Interpretations

In order to better understand potential storage and pathways 

of movement of contaminated groundwater at the site, three cross 

sections (locations shown in fig. 5) were constructed: (1) one is 

oriented northeast, extending from the east corner of the berm of 

pond 6 along the berm between ponds 4 and 5 (through drill holes 

FC–5 and FC–8) and across Fry Creek to the exposed sandstone 

slope on the northeast side of the creek (A–A′, fig. 7); (2) a second 

extends nearly due north along a deeply eroded road trace that 

drops to the creek level at the north corner of the disturbed area 

and continues across the creek to bedrock on the north side (B–B′, 

fig. 8); and (3) a third extends north-south across the stream 

terrace abreast of the cottonwood tree and on across the creek 

(C–C′, fig. 9).

Cross section A–A′ (fig. 7) shows that a 5.5-m-thick 

section of unconsolidated sediment underlies the approximately 4.3-m-high bench adjacent to Fry Creek. From nearby 

exposures and lithologic descriptions of well cuttings, this 

sediment appears to consist of tailings of varying thickness 

related to uranium operations, undisturbed eolian sand and 

colluvium deposited on the bench, and basal coarse gravels. 

As such, the two drill holes (FC–5, FC–8) define a paleochannel that is broader and deeper than the modern channel of Fry 

Creek (fig. 7). The limits of this paleochannel are considered 

to be the steep sandstone slope on the northeast side of the 

line of section and the sandstone ledges on the southwest side 

(shown hypothetically to the southwest of drill hole FC–8). 

The section in drill hole FC–5 contains more gravel than that 

observed in FC–8, indicating that the older stream channels 

tended to favor the northeast side of the valley, as they do now. 

The tailings and the underlying sand and gravel contaminated 

by leachate from the tailings and uranium- and copper-rich 

effluent placed in the ponds likely serves as a source for 

leachable uranium above the water table, a zone for temporary 

storage of uraniferous groundwater, and a pathway for movement of contaminated groundwater. The gravels may have 

high transmissivity.

Cross section B–B′ (fig. 8) portrays vertical sections of 

surficial sediments exposed in a road cut and in a 3.7-m-high 

cutbank adjacent to the south side of the stream channel. No 

drill holes have been located at this site. In these places, three 

layers of gravel and boulder gravel are exposed; however, the 

upper layer of gravel appears to be partly eroded and the voids 

filled with eolian sand and colluvium. Eolian sand and colluvium also form the uppermost layers exposed in the cutbank. 

A sandstone ledge is exposed just below the road surface, 

about 12.2 m from the edge of the stream channel; however, 

well-rounded fluvial gravel laps onto the bedrock surface as 

much as 26 m from the edge of the modern stream channel. 

These older gravels may be present beneath the bench at the 

project site, but they were undetected in the drill holes studied 

by the authors.
12 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

Figure 7. Cross section A–A' across the modern stream channel of Fry Creek and the bench to the south, at the position of the berm 

between ponds 4 and 5. See figure 5 for the line of section. Geochemical data for well FC–8 are in table 3. Datum for the cross section 

is the collar elevation of drill hole FC–8.

Figure 8. Cross section B–B' across the valley floor of Fry Creek north of the Fry Canyon project site at the location of a washed-out 

road. See figure 5 for location of section. Datum is the surface of the flowing channel.

B B'

NORTH

METERS

SOUTH

METERS

Hand-dug pit

g Modern glass at 55 centimeters

EXPLANATION

Modern channel

of Fry Creek

Low alluvial terrace

g Alluvium

Bench surface

Flowing channel (4/2007)

Modern channel sediment

Paleochannel deposits—thickness unknown

Paleochannel

Edge of older paleochannel ?

Cedar Mesa sandstone

Sandstone ledge

Sandstone ledge

Road surface

Eolian sand

and colluvium Gravel

Boulder gravel

Gravel

Gravel

Side channels

Colluvium

Old road

Ledge

Cedar Mesa

sandstone

0 10 20 30 40 50 60 70 80

–2

–3

–4

–1

0

1

2

3

4

5

6

–2

–3

–4

–1

0

1

2

3

4

5

6

VERTICAL EXAGGERATION, 2.5:1 DISTANCE (METERS)

Drill hole

FC–8

Drill hole

FC–5

Modern channel

of Fry Creek

Eolian sand

and colluvium

Cedar Mesa

sandstone

Sandstone

“bald” surface

Not exposed Eolian

sand and

colluvium

Tailings

Tailings Tailings Projection of

pond #5 profile

into section

BH12

collar

Gravel

Total depth Total depth

Flow

Berm of pond #6

Sandstone ledge projected

into section

Hypothetical lower

sandstone ledges

based on trenching

at Permeable 

Reactive

Barrier site

Cedar Mesa

sandstone

Eolian sand

A A'

SOUTHWEST

0 10 20 30 40 50 60 70

–6

–5

–4

–3

–2

–1

0

1

2

3

–7

–8

–6

–5

–4

–3

–2

–1

0

1

2

3

–7

–8

METERS

NORTHEAST

METERS

Paleochannel

DISTANCE (METERS) VERTICAL EXAGGERATION, 2.5:1
Geology, Geophysics, and Geochemistry 13

Figure 9. Cross section C–C' across the valley floor of Fry Creek at the location of the cottonwood tree well field. See figure 5 for 

location of section. Geochemical data for well FC–12 are in table 3. Datum is the surface of the flowing channel.

The depth of the valley fill beneath the exposed section and stream bottom is unknown. Four drives of rebar into 

the bottom of the modern channel went to refusal at 25–50 cm, 

but these depths are thought to represent the tops of large 

boulders (rather than bedrock) possibly at the top of older 

alluvium, such as that exposed at the base of the adjacent 

3.7-m-high cutbank.

The relations described above indicate that the modern 

channel probably overlies much of the paleochannel, which 

presently may be carrying groundwater in the subsurface. 

The possible limits of this water-bearing paleochannel would 

extend from the sandstone ledge exposed at the bottom of the 

road cut south of the modern channel to the small hand-dug pit 

north of the modern channel that contacted bedrock below one 

of the side channels (see horizontal arrow, fig. 8). The thickness of the paleochannel sediments below the modern stream 

surface is not known.

Cross section C–C′ (fig. 9) extends north from two 

prominent cedar trees perched on a thinly covered sandstone 

ledge through Geoprobe hole BH–08 and drill hole FC–12, 

across the narrow channel of Fry Creek, and up thinly covered 

sandstone bedrock to a sandstone ledge at the north end. 

The stream flows at the south edge of a bedrock exposure 

that probably defines the north edge of a paleochannel. The 

modern channel seems limited to the north by thin alluvium perched on bedrock and an adjacent eolian sand and 

colluvium deposit (see arrows in fig. 9). Drill holes BH–08 

and FC–12 penetrated 2.7 m of sediment, which places some 

constraints on the width of the central part of the paleochannel. A rebar probe along the cross section went to refusal at a 

depth of 48 cm (fig. 9). If this represents the bedrock contact, 

the south edge of the paleochannel lies north of that location. A resistivity survey along this cross section (described 

in the following section) indicates that the position of south 

edge of the channel is as shown in figure 9. The lithologic 

log for FC–12 shows 1.5 m of sand then 1.2 m of gravel and 

sand. The lithologic log for hole BH–08 was not available, 

but based on the driller’s comments, most of the section is 

eolian sand and colluvium with thin fluvial gravels at the base 

as portrayed in figure 9. An area of high-standing sediment 

lies between the position of the rebar probe and the two cedar 

trees, forming a bench. Pebbles and cobbles lie at the toe of 

the slope. Geophysical data (discussed in the following section) indicate that a modestly thick section of damp sediment, 

herein interpreted as gravel, underlies this bench as shown in 

figure 9. This body of gravel may be correlative with the older 

gravels shown in the cross section in figure 8. Both bodies 

of gravel are at about the same height above the present-day 

stream channel.

In this location, the modern channel and the paleochannel overlap only slightly. The width of the paleochannel 

is reasonably well constrained by drill-hole and geophysical data. Water analyses from the monitoring wells in this 

stream terrace area show significant contamination from the 

project site.

Direct-Current Resistivity Survey

Four direct-current (dc) resistivity surveys were completed in the study area. All four lines were designed to 

delineate the possible subsurface extent of the paleochannel 

that parallels the modern stream channel and may underlie the 

adjacent stream terraces. Line FC–1 (fig. 10) was located in an 

area of monitoring wells near a cottonwood tree, a local landmark on the bank of Fry Canyon Creek, 200–300 m northwest 

of the uranium tailings ponds (see fig. 3 for location of the 

geophysical survey line). Line FC–3 (figs. 11, 3) started about 

Twin trees

Ledge

Eolian sand

and colluvium

Older gravel

Projected

Cedar Mesa sandstone

Geophysical data suggests

gravel bed here

Rebar

probe Geophysical data

suggests ledge here Geoprobe

BH–08

Drill hole

FC–12

Eolian sand and colluvium

Total depth Total depth

Gravel

Modern channel

of Fry Creek

Not exposed

Flow

Alluvium

Eolian sand

and colluvium Ledge

Cedar Mesa sandstone

Paleochannel

VERTICAL EXAGGERATION, 2.5:1

C C'

SOUTH

6

–10 0 10 20 30 40 50 60 70 80

5

4

3

2

1

0

–1

–2

–3 –3

6

5

4

3

2

1

0

–1

–2

METERS

NORTH

METERS

DISTANCE (METERS)
14 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

16 m north and 2 m west of the origin of line FC–1, diverged 

to the west and extended only to the edge of the creek. This 

line parallels geologic cross section C–C′ (fig. 9) and extends 

from the –20 ft position to the 190-ft position on that section. 

Lines FC–1 and 3 have well data that show alluvium/bedrock 

contacts and thus provide some “ground truth” for interpreting 

the resistivity profiles. Line FC–2 (figs. 12, 3) extends from 

the modern stream channel across a terraced area between the 

cottonwood tree to the southeast and the ranch and barn complex to the northwest. Line FC–4 (figs. 13, 3) is located north 

of the ranch and barn complex in another terraced sector of 

the stream. There was no drill-hole control along these latter 

two lines.

Interpretation

The profiles show resistivity as a function of depth along 

each survey line. The resistive (low-conductivity) features 

seen in the profiles (red and orange features) generally represent dry materials, such as dry surface sediment and lowporosity bedrock. Low-resistivity (high-conductivity) features 

(purple and blue) generally represent wet and saline materials, 

such as wet sediment and groundwater in the alluvium. Moderately resistive features (green and yellow) generally represent alluvium or bedrock having a low moisture content and 

groundwater having a low TDS concentration. It is important 

to note that the horizontal and vertical scales vary from plot to 

plot. The horizontal scale of each profile was maximized for 

a page-size plot. The vertical scales are exaggerated for better 

anomaly resolution with depth.

Line FC–1

The purpose of line FC–1 (fig. 10) was to image the 

subsurface across the valley floor of Fry Creek between 

bedrock exposures on the south side of the creek and bedrock 

exposures on the north side. As noted, this line runs through 

an area of monitoring wells adjacent to a large cottonwood 

tree. Geologic and geochemical data for these wells provide 

ground truth information for interpreting the geophysical data and the evidence that groundwater in the sand and 

gravel present here is contaminated. The line is 100 m long 

and runs south to north roughly perpendicular to the creek 

valley. Important surface features to note include exposed 

bedrock near the start of the line at 0 m. Between 12 m and 

30 m is a high, sloping bench surface separated by a steep 

slope between 30 m and 38 m from a lower stream terrace 

surface that extends to about 68 m. Streamflow and bedrock 

exposures extend from 75 m to 84 m. The creek runs between 

78 and 79.5 m. Thin, saline, wet alluvium covers the bedrock 

from 88 m to near the end of the line. Monitoring well FC–9 

is located at 52 m. Wet sediment, with surficial white salt 

crystals, is located at 74 m and between 82 and 84 m. Bedrock 

ledges crop out adjacent to 100 m.

The resistive zone at 0–6 m (fig. 10) is caused by the 

dry bedrock seen outcropping at the start of the line. A small, 

conductive, vertically oriented anomaly, located at 6–8 m and 

extending nearly to the surface, may represent a fractured bedrock zone with higher water and clay content. A thin, resistive 

surface layer, between 6 and 60 m, is caused by a dry layer of 

surficial sediment. The resistive material at depth in this interval (1,610-m elevation in the south part and 1,605-m elevation 

Figure 10. Direct-current resistivity profile for Fry Canyon line FC–1. See figure 3 for location. The location of monitoring well FC–9 is 

shown. The bar is 3 meters long. Specific conductivity data for well FC–9 are in table 2. See section “Direct-Current Resistivity Survey” 

for key to colors.

Fry Canyon Line FC–1

1,610

1,620

1,600

1,590

ELEVATION (METERS)

0 10 20 30 40 50 60 70 80 90 100

NORTH

Fry Creek

DISTANCE (METERS)

OHM-METERS

0 100 200 300 400 500 600 700 800 900 1,000

FC–9

SOUTH
Geology, Geophysics, and Geochemistry 15

Figure 11. Direct-current resistivity profile for Fry Canyon line FC–3. See figure 3 for location. The location of monitoring well FC–12 is 

shown. The bar is 3 meters long. Specific conductivity data for well FC–12 are in table 2. See section “Direct-Current Resistivity Survey” 

for key to colors.

Figure 12. Direct-current resistivity profile for Fry Canyon line FC–2. See figure 3 for location. See section “Direct-Current Resistivity 

Survey” for key to colors. ELEVATION (METERS)

SOUTH NORTH

1,615

1,620

1,610

1,605

1,600

0 10 20

OHM-METERS

FC–12

Fry Creek

DISTANCE (METERS)

30 40 50 60 70

0 100 200 300 400 500 600 700 800 900 1,000

Fry Canyon Line FC–3

SOUTHWEST Fry Canyon Line FC–2 NORTHEAST

ELEVATION (METERS)

Fry Creek

0 100 200 300 400 500 600 700 800 900 1,000

DISTANCE (METERS)

OHM-METERS

1,615

1,620

1,610

1,605

1,600

0 10 20 30 40 50 60 70 80 90 100 110 120 130

in the north part) is low-porosity bedrock having a low 

moisture content. Between these two resistive layers, between 

12 and 44 m, is a moderately conductive zone. There seem 

to be two sections to this zone. The conductive zone between 

12 and 30 m is physically higher than the sector between 

30 m and 42 m, as is the surface topography. This layer that 

extends from12 to 30 m along the profile may represent damp, 

slightly saline sediment filling an older, high-standing channel. This part of geophysical profile FC–1 is contiguous to the 

cross section in figure 9 and the associated geophysical profile 

FC–3, which are interpreted to show a high-standing gravel 

bed in a similar position.

The northern portion of this moderately conductive 

zone, extending from 30 to 42 m, appears to be underlain by 

bedrock. A rebar probe was driven into the ground to the west 

of this line, and a Geoprobe hole was driven into the ground to 

the east of this line. Both went to refusal on hard sandstone at 

depths of 0.3–0.6 m at a position equivalent to the 38-m mark 
16 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

along line FC–1. This moderately conductive zone between 

30 and 42 m may represent (1) an inversion artifact produced 

by poor data coverage (see following discussion for FC–3); 

(2) moist bedrock composed of thin sandstone, siltstone, and 

mudstone (upstream from Fry Spring, springs were observed 

issuing from thin siltstone and mudstone layers beneath an 

overhanging ledge of sandstone); or (3) a paleochannel filled 

with sandstone boulders and other sediment, the rebar and 

Geoprobe both fortuitously contacting large sandstone boulders seen elsewhere.

A wide, very low resistivity zone is located between 45 

and 76 m. It extends to the streambank adjacent to the surface 

flow in the modern stream. This shallow conductive zone is 

as much as 6 m thick, and the upper, more conductive part 

(1–3 m deep) is interpreted as water-bearing and saline sediment filling a buried bedrock channel. Monitoring well FC–9 

(shown by a 3-m-long bar) is located within this conductive 

zone, and bedrock was contacted at a depth of 3.05 m with 

saturated sediment in the 0.6–1 m interval above bedrock 

(Brent Lewis, Bureau of Land Management, unpublished 

drill-hole logs). The data in the profile do not seem to discriminate between the damp to wet unsaturated zone and the 

0.6–1-m-thick saturated zone, suggesting that salinity in the 

unsaturated zone and groundwater blur the distinction. The 

more modest conductive zone below (3–6 m deep) may represent bedrock partly saturated with saline water.

From 62 to 76 m along the profile very low resistivity 

extends to the surface, suggesting that saline sediment dominates the unsaturated zone. White, damp, salt deposits on 

alluvial sediments were observed on the surface in this area, 

indicating that the shallow groundwater has relatively high 

TDS and that the unsaturated zone has significant salt accumulations. Evapotranspiration concentrates the salts in the 

near-surface sediments, resulting in a low-resistivity, though 

unsaturated, surface layer.

At the location of well FC–9 the resistivity profile shows 

values of 50–70 ohm-m (pale blue) at a depth of 3 m, which 

likely represents the sediment/bedrock contact given the 

drill-hole intercept. This drill-hole intercept and portions of 

this conductive anomaly are below the elevation of the current 

stream channel where bedrock is exposed, suggesting that a 

paleochannel is present here.

A resistive near-surface zone is located between 78 and 

86 m. This resistive feature probably represents the shallow 

bedrock exposed adjacent to the stream along the modern 

channel. Being located immediately below the current stream 

channel, but having a high resistivity, indicates the bedrock 

has a low porosity and is relatively unfractured at this location. The small, subhorizontal conductive anomaly, centered 

at 85 m and extending as much as 6 m below the surface, 

probably represents a fractured bedrock zone containing highTDS water. A long, wide, sinuous fracture is present in the 

Figure 13. Direct-current resistivity profile for Fry Canyon line FC–4. See figure 3 for location. See section “Direct-Current Resistivity 

Survey” for key to colors.

OHM-METERS

DISTANCE (METERS)

SOUTHWEST Fry Canyon Line FC–4 NORTHEAST

ELEVATION (METERS)

Fry Creek

Qeb

Qal2

1,610

1,620

1,600

1,590

1,580

0 10 20 30 40 50 60 70 80 90 100

0 100 200 300 400 500 600 700 800 900 1,000
Geology, Geophysics, and Geochemistry 17

exposed bedrock at this location. A surface layer of conductive 

alluvial sediment with saline crusts extends from 87 m to the 

end of the traverse near the base of bedrock ledges. At depths 

below 6 m the high resistivity indicates that the bedrock is not 

porous or fractured.

Line FC–3

Line FC–3 (fig. 11) is also located near the cottonwood 

tree (fig. 3). The purpose of line FC–3 was to provide subsurface 

information along the geologic cross section shown in figure 9. 

The line is 64 m long, runs subparallel to line FC–1, and has 

similar features. The line starts at two large juniper bushes, which 

are on the north edge of a thinly covered bedrock ledge; this line 

then crosses the valley onto bedrock exposed just north of the 

flowing stream (from the –20 to the +180 ft positions in the cross 

section in fig. 9). Important surface features to note in profile 

FC–3 include exposed bedrock 2 m south of station 0 and from 

60 to 64 m. A small patch of rounded (fluvial?) cobbles lies at the 

surface at the toe of the slope at about 20 m. A rebar probe was 

driven into the ground at 22 m. Geoprobe hole BH–08 is located 

at 35 m (not shown). Well FC–12 is located at 42 m (a 3-m-long 

bar marks the location). Bedrock intercept data provide information important to interpreting the geophysical data along line 

FC–3. Damp sediment with surficial white salt crystals is located 

on the streambank between 53 and 55 m. The stream is located 

at 58 m.

From 0 to 40 m, a thin resistive layer is located along 

the surface and is produced by dry, sandy sediment (fig. 11). 

Immediately below this resistive layer, the ground becomes 

more conductive, indicating an increase in moisture or salt 

content. A moderately conductive anomaly extending from 

4 to 12 m suggests the presence of shallow, damp, somewhat 

saline sediment, possibly representing a perched gravel bed 

similar to that noted in the southern part of line FC–1. The 

rounded cobbles observed at the surface at 20 m may have 

been weathered out of such a gravel bed. The conductive zone 

located between 14 and 20 m at a depth to 4 m, is similar to 

the zone seen in FC–1. This interval occurs in a similar position but with less resolution due to poor data coverage (see 

Appendix 2, fig. 26). The rebar probe at 22 m intercepted 

hard sandstone at 0.5 m. This anomaly is poorly constrained 

and cannot be interpreted as a real subsurface feature without 

further information. At depth below 4 m the section becomes 

resistive, indicating bedrock having a low porosity and low 

moisture content.

A low resistivity zone is located between 24 and 56 m. 

This shallow zone extends from about 1 to 4.5 m deep, and 

the upper, more conductive part from 1 to 3 m likely includes 

0.6–1 m of water-bearing sediment and overlying saline unsaturated-zone sediment. The relatively low resistivity suggests 

the saturated sediments contain conductive water. Like profile 

FC–1, the shape and depth of the anomaly suggest the presence 

of a sediment-filled bedrock channel. Geoprobe hole BH–08 

and monitoring well FC–12 are located within this conductive 

zone. Both wells indicate bedrock at a depth of 3.05 m (Brent 

Lewis, Bureau of Land Management, unpublished drill-hole 

logs). At both locations and similarly to the intercept in profile 

FC–1, the profile shows resistivity values of 50–70 ohm-m 

at a depth of 3 m, which probably represents the sediment/

bedrock contact.

The surface is very conductive between 46 and 56 m. 

Surface salt deposits were observed within this area, indicating 

shallow groundwater with high TDS and concentration of salts 

in the unsaturated zone by evapotranspiration.

The thin, modestly conductive surface layer between 

56 m and the end of the line is produced by wet sediment in 

the current stream channel. Here, the sediment is very thin 

with salt crusts overlying resistive bedrock. The high resistivity of the underlying bedrock suggests it has low porosity and 

is relatively unfractured at this location.

Line FC–2

Line FC–2 (fig. 12) is located approximately 200 m 

downstream from line FC–1 (fig. 3). The purpose of line FC–2 

was to image the subsurface below the modern stream channel and a broad, very gently sloping stream bench on the east 

bank of the creek. The line is 128 m long and strikes approximately N.40o

E. across the creek valley. The line runs from low 

bedrock exposures on the southwest edge of the wide, modern stream channel up onto the bench. Bedrock cliffs occur 

to the southwest of this line. Bedrock outcrops are observed 

approximately 15 m beyond the northeast end of the line. 

Important surface features to note include exposed bedrock 

in the streambed from 0 to 6 m. The creek flows between 9.5 

and 11 m. Thin, wet sediment in the streambed lies on bedrock 

and is covered with white salt crystals between 6 and 24 m. 

The streambank is covered with white salt crystals from 24 

to 26 m.

The southwest half of line FC–2 is considerably more 

conductive than the northeast half (fig. 12). The abrupt change 

in the near-surface resistivity observed at 58 m is interpreted 

as moist to wet sediment overlying saturated and unsaturated 

bedrock to the southwest, in contact with dry sediment over 

dry bedrock to the northeast. The relatively thick conductive zone located between 22 and 58 m, from the surface to 

a depth of about 4 m, is interpreted, in part, as wet fluvial 

sediment filling a broad paleochannel in the bedrock. The deep 

conductive zones, from 20 and 34 m and from 50 and 58 m, 

are interpreted as bedrock having greater porosities, possibly 

due to fracture zones, and containing increased amounts of 

groundwater. The relatively low resistivity of these zones 

suggests groundwater having relatively high TDS. The depth 

of the paleochannel is difficult to pick because of the apparent 

bedrock fracture zones, but it may be a meter or so below the 

modern stream channel.

The most conductive feature on the profile is located 

between 24 and 32 m. This shallow conductive zone is located 

on the sloping bank of the stream and the adjacent stream terrace edge, between the current channel and the stream terrace. 
18 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

The zone is 3–4 m thick, and is partly coincident with an area 

covered with white salt crystals. This conductive zone probably 

results from wet surface sediment having a high salt content. 

The surficial salt deposits suggest evapotranspiration and 

accumulation of salts in the unsaturated zone derived from the 

shallow groundwater.

The resistive surface, from 0 to 8 m, is produced by 

exposed bedrock in the stream channel. The thin surface 

conductive zone, from 10 to 22 m, is produced by the layer 

of wet sediment overlying resistive bedrock in the streambed. Based on the observed surficial salt crystals in this area, 

the water in the sediment is probably quite conductive due 

to the presence of dissolved salts. Resistive bedrock underlies the southwestern end of the line from 0– to 22 m. The 

modern stream channel is located over this part of the line; 

the resistive nature of the bedrock suggests it is composed 

of impermeable, unfractured sandstone having a low water 

content. Only relatively minor, tight fractures were noted in 

bedrock exposures.

Northeast of 58 m, the character of the profile becomes 

relatively resistive. Here, the surface is slightly more resistive, to a depth of 2–3 m, than the underlying material. The 

resistive surface layer is interpreted as dry sediment overlying 

bedrock having a low water content. The resistive features at 

depth represent dry or impermeable sandstone having little or 

no groundwater. The more conductive zones at depth (that is, 

70–85 m) are probably bedrock zones having slightly higher 

porosities. There seems to be no evidence in this profile for 

a high-standing gravel-filled paleochannel; however, if such 

a channel were completely dry, it may not be distinguishable 

from dry surface sediment or bedrock.

Line FC–4

Line FC–4 (fig. 13) is located approximately 400 m 

downstream from line FC–2 (fig. 3). The purpose of 

line FC–4 was to help define the west edge of the bedrock 

channel, which is covered by surface sediment on a two-level 

stream terrace. The line is 100 m long and strikes approximately N. 50o E. The line begins on high ground with bedrock 

outcrops about 80 m west of the stream and runs downhill, 

across a gently sloping high stream terrace, an essentially flat 

lower stream terrace, then across the stream and onto bedrock 

in the modern stream channel. This line is located north of the 

area mapped in figure 4, but the features mapped extend to the 

position of the profile.

Important surface features to note include thin dirt cover 

over bedrock from 0 to 19 m. The line follows a shallow gully 

from 10 to 19 m. The upper stream terrace is located between 

25 and 54 m (including the toe of the stream terrace). The 

lower stream terrace extends from 56 to 84 m and the streambank from 84 to 88 m. The stream is located between 90 and 

92 m. Wet surface sediment is located between 90 and 93 m. 

Wet sediment, with surficial white salt crystals, overlying bedrock is located between 93 and 102 m, beyond the profile.

In line FC–4 the highly resistive surface layer, located 

between 0 and 20 m, results from dry bedrock (fig. 13). The 

increase in conductivity with depth suggests that the water content increases. A small conductive anomaly, located at 8 m, may 

represent a fractured bedrock zone with higher water content.

A relatively thick, sloping conductive zone lies between 

26 and 54 m and corresponds with a mapped older stream 

terrace just upvalley (Qoal in fig. 4). The upper part of the 

conductive zone (that part less than 50–70 ohm-m in resistivity) is interpreted as wet to saturated saline sediment overlying 

bedrock, based on the 50–70-ohm-m values used to define 

a wet sediment/bedrock contact in FC–1 and FC–3. A thin 

resistive layer, produced by dry surficial sediment, covers 

much of this conductive feature. Much of this conductive 

anomaly is well above the modern stream channel. Therefore, 

the water source is not the stream; the source probably is 

buried bedrock springs and fractures recharged from the high 

ground to the west. We are uncertain if this is a sediment-filled 

channel equivalent to the higher channel suggested by the 

high-standing gravel in figure 9 and the possible high-standing 

channel in profiles FC–1 and FC–3.

The abrupt resistivity contrast at depth (represented by 

juxtaposed pale green and pale orange colors), located at 48 m 

and extending from 1,590 to 1,596-m elevation, is an inversion 

artifact produced by poor data coverage (see Appendix 2 and 

fig. 28). This vertical feature is poorly constrained and should 

not be interpreted as a real subsurface feature.

The part of the line located between 54 and 84 m crosses 

a wide, flat stream terrace. The thin surface resistive layer is 

dry surface sediment, noticeably thicker than the layer covering the conductive layer to the west. The conductive zone 

immediately beneath is interpreted as wet, somewhat saline 

sediment. This conductive zone, which overlies relatively 

resistive bedrock at depth, is partly below the modern streamchannel elevation and may represent sediment filling a broad 

channel in bedrock. This channel would seem to be the lower 

paleochannel traceable through the three previous profiles, 

here about 30 m wide. Extremely low resistivity (<50 ohm-m) 

saline sediment on the streambank between the creek and the 

lower terrace, seen in other profiles, is not seen here. From 90 

to 100 m, the very thin surface conductive layer is produced 

by wet, saline sediment in the modern stream channel. The 

underlying resistive zone is the shallow bedrock, which is 

widely exposed on the flat stream channel bottom. Surficial 

salt deposits observed here on the thin alluvium indicate that 

the shallow groundwater has high concentrations of TDS.

Structure

Dips of the bedrock in the mapped areas were difficult to 

determine, but generally they were about 1 degree to the west. 

The geologic and regional structure contour map of Thaden 

and others (1964, plate 1) showed that strikes of the section in 

Fry Canyon were about N. 10o W. and dips were about 1.3o W. 
Geology, Geophysics, and Geochemistry 19

Fractures in the Cedar Mesa sandstone are not abundant but 

may form local pathways for the migration of contaminants 

into bedrock as indicated by the resistivity profiles previously 

described. Fractures were observed in exposures of bedrock on 

natural balds, along the stream channel, and in areas disturbed 

by bulldozing. Most fractures are thin, sinuous, and of limited 

lateral extent. One fracture zone located west of, and downslope 

from, heap leach piles is as much as 25 centimeters wide and 

contains crushed sandstone; however, this zone could not be 

traced laterally because of cover. Fractures along the modern 

stream channel have been opened up by erosional processes and 

are generally filled with alluvium. Depths of any of these filled 

fractures cannot be determined from surface exposures. It seems 

likely that similar open fractures may be associated with the 

trace of the paleochannel in the subsurface, and such fractures 

may be pathways for movement of contaminated water into the 

bedrock, as suggested by the resistivity profiles.

General Chemical Character of Water

Waters sampled in this study are of circumneutral to 

slightly alkaline pH (6.75–8.65) and moderate specific conductance (1,200–2,800 microsiemens per centimeter (μS/cm), 

table 2). Total dissolved solids (calculated) range from 820 

to 2,800 mg/L, which indicates slightly saline waters (Hem, 

1985). Seeps and springs are slightly less saline than surface waters and downgradient well waters, which in turn are 

slightly less saline than plume wells on the Fry Canyon project 

Table 2. Chemical and isotopic composition of surface water, seeps, springs, and wells, Fry Canyon, Utah.

[NAD27 CONUS, North American Datum 1927 Continental United States; Spec. cond., specific conductance; TDS, total dissolved solids; μS/cm, microsiemens per 

centimeter; °C, degrees Celsius; mg/L, milligram per liter; μg/L, microgram per liter; km, kilometer; ft, feet; Est., estimated; <, less than]

Sample

ID Location notes

(NAD27 CONUS/12S) Est.

accuracy

(ft)

Longitude

(west)

Latitude

(north)

Fry

Creek

(km)

Fry

Creek

(miles) GPS-Easting GPS-Northing

07FC-W1 Upstream where surface flow first occurs 576811 4162450 18 110.130 37.608 0 0

07FC-W2 Seep pool in side channel adjacent to Qal-2 576858 4162615 17 110.129 37.609 0.193 0.12

07FC-W3 Seep pool in side channel adjacent to Qal-2 576846 4162920 14 110.129 37.612 0.499 0.31

07FC-W4 Seep from under overhanging sandstone 

ledge, near Fry Spring

576758 4163041 19 110.130 37.613 0.66 0.41

07FC-W5 Spring from side wash, near Fry Spring 576747 4163057 40

(rock 

ledges)

110.130 37.613 0.676 0.42

07FC-W6 Fry Spring—north edge of pool 576745 4163142 29 110.130 37.614 0.74 off channel 

at 0.46 

07FC-W7 Surface flow of stream, just upstream 

from Fry Spring

576768 4163132 18 110.130 37.614 0.74 0.46

07FC-W8 Seep pool at base of salt cedar adjacent 

to berm of Pit #2

576544 4163439 18 110.133 37.617 1.127 0.7

07FC-W9 Surface water adjacent to cottonwood 

tree well field

576192 4163610 14 110.137 37.618 1.545 0.96

07FC-W10 Surface flow of stream downvalley from 

the ranch site

575859 4164122 18 110.140 37.623 2.462 1.53

07FC-W11 Stagnant pool in small slot canyon 

downvalley from ranch

575355 4164905 16 110.146 37.630 3.541 2.2

07FC-W12 Stagnant pool, slot canyon just upstream 

from bridge

575120 4165436 20 110.149 37.635 4.41 2.74

(bridge 

at 2.80)

07FC-W13 Cottonwood tree well field—Well FC9 576195 4163582 20 110.137 37.618

07FC-W14 Cottonwood tree well field—Well FC12 576187 4163590 23 110.137 37.618

07FC-W15 Contaminant plume—Well FC7 576436 4163498 28 110.134 37.617

07FC-W16 Contaminant plume—Well FC4 576453 4163495 19 110.134 37.617

07FC-W17 Contaminant plume—Well FC8 576464 4163464 20 110.134 37.617

07FC-W18 Contaminant plume—Well FC3 576434 4163508 0.6

(SAIC)

110.134 37.617

07FC-W19 Fry Spring—Well FC1 576727 4163155 0.6

(SAIC)

110.131 37.614

07FC-W20 Cottonwood tree well field—Well FC11 576203 4163587 16 110.137 37.618
20 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

site. Sample W15 collected from the center of the contaminant 

plume stands out because it is approximately twice as saline 

(2,800 mg/L) as any other water sample. Based on the milliequivalent per liter (meq/L) concentrations of major cations 

and anions, most sampled waters are of the Na-Mg-HCO3 or 

Na-Mg-HCO3-SO4 chemical types. An important exception is 

well water W15, which is Ca-Mg-SO4 water with relatively 

minor amounts of bicarbonate, chloride, and sodium compared 

to the other waters (fig. 14). Contrasting chemistry of contaminant plume water and local water was noted earlier (Naftz 

and others, 2000) and indicates that plume water chemistry is 

variably affected by calcium and sulfate derived from the heap 

leach piles. Other dissolved anions (fluoride, nitrate, phosphate) were not measured but are of probable low concentration based on the close agreement (±3 percent) of calculated 

cation-anion balances for the waters using only bicarbonate, 

sulfate, and chloride.

The seeps, springs, and surface waters are noteworthy 

for generally elevated concentrations of dissolved uranium 

(34–256 μg/L) when compared to the U.S. Environmental 

Protection Agency drinking-water standard of 30 μg/L 

(U.S. Environmental Protection Agency, 2001). This suite 

includes seven samples collected upstream from the Fry Canyon 

site (W1–W7; 44–58 μg/L) and is presumed to represent local 

baseline values. High natural baseline concentrations of dissolved uranium in oxygenated surface water and groundwater 

are expected in this setting that includes numerous local uranium mines, prospects, and radioactive anomalies (Thaden and 

others, 1964). However, aerosol sand, silt, dust, and salts from 

close and distant sources can also contribute major, minor, and 

trace elements to soils and subjacent groundwater. Thick sections of eolian sediment are present here. The high concentrations of dissolved uranium (380–578 μg/L) in three monitoring 

wells (W13, 14, 20) are clearly anomalous compared to baseline 

values and are highly suggestive of variable contamination from 

the Fry Canyon project site.

In contrast to uranium, concentrations of dissolved 

copper are generally less than 20 μg/L— the result of solubility control by insoluble copper hydroxides and carbonates 

or strong sorptive uptake by ferric oxyhydroxides (Hem, 

1985). One exception is plume well W17, which contained 

200 μg/L copper and anomalous concentrations of manganese 

(1,460 μg/L) and zinc (590 μg/L) (table 2). This well water 

was identified as metal-rich in previous sampling (Wilkowski 

and others, 2002). Water collected from this well contained 

abundant suspended oxyhydroxides that are efficient sorbents 

for trace metals and probably are not completely removed during filtration through a 0.45-mm filter membrane.

Excluding the equivocal data from plume well W17, dissolved concentrations of most other measured trace elements 

(manganese excluded) were less variable than uranium and were 

less obviously elevated in the remaining plume wells (W15, W16, 

W18) compared to other water samples. Concentrations also 

generally fell below comparative benchmarks such as drinkingwater standards or aquatic-life standards (U.S. Environmental 

Protection Agency, 2006a, 2006b). A few arsenic concentrations 

slightly exceeded the current drinking-water standard of 10 μg/L. 

A few concentrations of selenium and copper slightly exceeded 

a value of 5 μg/L, which may be harmful to some forms of 

aquatic life.

Table 2. Chemical and isotopic composition of surface water, seeps, springs, and wells, Fry Canyon, Utah.—Continued

NAD27 CONUS, North American Datum 1927 Continental United States; Spec. cond., specific conductance; TDS, total dissolved solids; μS/cm, microsiemens 

per centimeter; °C, degrees Celsius; mg/L, milligram per liter; μg/L, microgram per liter; km, kilometer; ft, feet; Est., estimated; <, less than]

Sample

ID

Temp.

°C pH

Spec.

cond.

(μS/cm)

TDS

mg/L

(calc.)

SiO2

(mg/L)

Na

(mg/L)

K

(mg/L)

Ca

(mg/L)

Mg

(mg/L)

Fe

(mg/L)

Cl

 (mg/L)

SO4

(mg/L)

HCO3

(mg/L)

07FC-W1 15 8.30 2,400 1,438.58 14.9 453 9.6 35.8 45.0 <0.05 135 428 675

07FC-W2 15 8.55 1,450 964.79 12.7 266 5.8 36.6 55.4 <0.05 68 201 675

07FC-W3 17 7.60 1,200 822.15 16.1 232 4.6 35.5 35.9 <0.05 62 184 545

07FC-W4 10 7.90 1,200 907.34 12.3 260 5.7 39.8 34.4 <0.05 75 220 555

07FC-W5 14 7.65 1,450 964.68 15.9 272 5.4 38.6 40.7 <0.05 84 251 555

07FC-W6 15 8.05 1,400 937.47 10.4 262 5.7 38.5 41.5 <0.05 77 233 570

07FC-W7 18 8.15 1,200 843.99 14.6 238 5.3 28.5 36.1 <0.05 70 210 520

07FC-W8 11 7.85 1,700 1,152.84 15.7 352 7.7 41.9 35.3 <0.05 101 266 710

07FC-W9 20 8.00 1,500 1,000.01 12.9 281 7.2 40.1 40.3 <0.05 83 283 540

07FC-W10 25 8.50 1,750 1,150.32 4.6 353 14.7 23.4 41.2 <0.05 109 361 505

07FC-W11 21 8.45 2,000 1,316.20 4.3 395 13.9 32.0 45.3 <0.05 131 436 535

07FC-W12 15 8.65 1,950 1,275.04 3.4 387 13.5 27.8 41.8 <0.05 130 433 493

07FC-W13 11 7.55 1,400 1,042.14 11.3 273 4.5 47.4 39.9 <0.05 90 329 525

07FC-W14 11 7.40 1,400 1,080.72 11.9 297 5.5 48.4 42.1 <0.05 93 324 550

07FC-W15 13 7.00 2,800 2,801.40 7.8 26.5 9.7 580 184 <0.05 0.5 1,906 193

07FC-W16 12 7.10 1,600 1,155.80 10.2 277 5.1 67.3 58.6 <0.05 92 366 590

07FC-W17 13 6.75 1,900 1,483.67 8.5 251 5.0 133 101 <0.05 93 600 610

07FC-W18 12 7.10 1,980 1,390.17 9.0 262 5.6 139 64.6 <0.05 92 554 555

07FC-W19 12 7.60 1,490 962.31 17.6 267 4.4 37.8 41.3 <0.05 82 255 558

07FC-W20 10 7.50 1,650 1,033.08 11.7 279 4.7 46.6 40.5 <0.05 87 317 525
Geology, Geophysics, and Geochemistry 21

Table 2.—Continued

[NAD27 CONUS, North American Datum 1927 Continental United States; Spec. Cond., specific conductance; TDS, total dissolved solids; μS/cm, microsiemens 

per centimeter; °C, degrees Celsius; mg/L, milligram per liter; mg/L; microgram per liter; km, kilometer; ft, feet]

Sample

ID

As

(μg/L)

B

(μg/L)

Ba

(μg/L)

Cu

(μg/L)

Li

(μg/L)

Mn

(μg/L)

Mo

(μg/L)

Ni

(μg/L)

Se

(μg/L)

Sr

(μg/L)

V

(μg/L)

Zn

(μg/L)

U

 (μg/L)

234U/238U

Activity

ratio

δ34S

(permil)

07FC-W1 12 130 97 9 198 1 42 4 5 950 5 3 58 1.229±.011 –5.4

07FC-W2 8 92 97 16 150 2 23 4 3 1,210 6 3 45 1.089±.005 –2.4

07FC-W3 5 72 50 7 127 0 19 3 3 990 3 17 47 1.279±.005 –3.1

07FC-W4 5 75 50 5 128 0 26 2 6 990 6 2 58 1.223±.007 –3.2

07FC-W5 4 82 49 4 127 0 25 2 11 1,090 9 2 58 1.271±.001 –3.4

07FC-W6 3 77 41 4 128 0 19 2 5 1,080 6 3 58 1.283±.003 –3.3

07FC-W7 7 84 85 5 134 1 23 2 4 910 5 1 44 1.270±.002 –3.3

07FC-W8 13 85 149 8 157 3 16 5 4 960 6 2 34 1.150±.005 1.8

07FC-W9 6 88 92 8 140 1 24 3 5 1,020 7 3 152 1.064±.003 –2.8

07FC-W10 10 105 83 13 167 2 32 2 6 840 10 3 199 1.048±.003 –2.8

07FC-W11 10 94 111 15 191 3 37 3 6 1,010 9 18 255 1.050±.005 –2.7

07FC-W12 10 98 110 16 182 2 37 3 6 880 10 7 256 1.052±.001 –2.9

07FC-W13 3 69 26 8 142 245 32 4 3 920 1 3 578 0.985±.002 –3.4

07FC-W14 2 76 24 7 141 112 28 6 5 1,040 2 7 380 1.012±.004 –3.5

07FC-W15 1 63 15 13 177 2 17 25 17 3,100 0 25 18,700 0.939±.005 –13.3

07FC-W16 2 83 25 7 148 40 4 17 8 1,340 0 18 770 0.954±.006 –3.1

07FC-W17 2 104 16 200 226 1,460 3 79 4 1,070 0 590 2,160 0.932±.005 –1.2

07FC-W18 2 73 28 6 157 210 3 13 4 1,470 0 6 2,070 0.930±.003 –1.5

07FC-W19 3 81 30 4 125 2 20 2 11 1,130 6 2 70 1.282±.004 –4.0

07FC-W20 3 70 28 4 126 372 29 5 3 950 1 4 429 0.985±.004 –3.4

Other trace elements sought but below 10 μg/L include Ag, Al, Be, Bi, Cd, Cr, Pb, Sb, and Tl.

Figure 14. Pie diagrams showing the relative percentages of major cations and anions (on a milliequivalent basis) in well W15 from 

the center of the contaminant plume and well W16, which is more representative of other contaminated water samples collected in 

this study.

EXPLANATION

Na+K

Ca

Mg

HCO3

SO4

Cl

Plume Well W15 Plume Well W16
22 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

Figure 15. Plot showing the relative abundance of major dissolved 

U(VI) species as a function of pH in waters of this study. Calculations 

were assigned an oxidizing Eh of +0.4 volt.

Aqueous Geochemistry of Uranium

In oxygen-bearing surface waters and shallow groundwaters of this study, uranium is oxidized to soluble U(VI) 

and occurs as a variety of soluble species, depending upon pH. 

Under acid-oxidizing conditions, U(VI) occurs primarily as 

the uranyl cation (UO2

+2), whereas under alkaline-oxidizing 

conditions of this study, U(VI) forms highly stable anionic 

complexes with dissolved carbonate that enhance its solubility (Langmuir, 1978). Speciation of dissolved U(VI) in each 

of the sampled waters was calculated using the computer code 

PHREEQC (Parkhurst, 1995), utilizing the WATEQ4F thermodynamic database (Ball and Nordstrom, 1991). For these 

calculations an oxidation potential (Eh) of +0.4 volt was used 

to simulate an oxygenated aqueous environment. For most 

waters of this study, uranyl tricarbonate [UO2(CO3)

–4] complex is dominant, and uranyl dicarbonate [UO2

(CO3)

2

–2] is of 

minor to submajor importance (fig. 15). Uranyl ion also forms 

a complex with dissolved phosphate at circumneutral pH 

(Langmuir, 1978), but very low concentrations of dissolved 

phosphate in most natural waters probably limit the contribution of this complex.

The PHREEQC computer code also permits calculation of the degree of saturation of waters with respect to a 

variety of minerals, including uranium minerals. Results for 

each mineral are expressed as a saturation index defined as 

the logarithm of the ratio of the ion activity product (IAP) 

divided by the equilibrium solubility product (KSP). These 

100

80

60

40

20

0

6.5 7 7.5 8 8.5 9

DISSOLVED URANIUM SPECIES,

IN PERCENT

pH

UO2CO3

UO2

(CO3)2

–2

UO2

(CO3)

3

–4

thermodynamic-based calculations assume mineral/

solution equilibria and, because reaction kinetics are not 

considered, are best interpreted as potentials for mineral 

dissolution (undersaturated condition) or mineral precipitation (oversaturated condition). Accuracy depends on the 

quality of the chemical analyses and the accuracy and internal consistency of the thermodynamic database. A value of 

zero for the saturation index indicates equilibrium saturation, positive values indicate oversaturation, and negative 

values undersaturation. Results for the sampled waters 

(fig. 16) indicate slight undersaturation or larger oversaturation with respect to quartz, calcite, dolomite, and ferrihydrite 

and undersaturation with gypsum and representative copper 

minerals malachite [Cu2(CO3)(OH)2] and tenorite [CuO]. 

All waters are highly undersaturated with the reduced U(IV) 

minerals uraninite (UO2) and coffinite [U(SiO4)1–x(OH)4x] 

and also with all U(VI) minerals in the PHREEQC database. 

Additional saturation indices for uranyl vanadate minerals 

were calculated using the thermodynamic database attached 

to the MINTEQA2 computer code (Allison and others, 1991). 

The U(VI) minerals include carnotite [K2(UO2)2(VO4)2

.

3H2O], 

schoepite [(UO2)4O(OH)6 

.

6H2O)], rutherfordine [(UO2)CO3], 

tyuyamunite [Ca(UO2)2(VO4)2

.

5-8H2O], and uranophane 

[Ca(UO2)2(SiO3)2(OH)2

.

5H2O]. U(VI) minerals show closest 

approach to saturation in the most uranium-rich water from 

plume well W15 but are still an order of magnitude undersaturated, considering the logarithmic scale of figure 16.

At the concentration of dissolved uranium in these waters 

(and most natural waters), uranium solubility is most likely 

limited by sorptive processes rather than uranium mineral 

saturation (Langmuir, 1978). The most likely sorbents for uranium at the site are ubiquitous secondary iron oxides that coat 

many grains and impart a reddish color to local sediments. 

Sorptive uptake of dissolved uranium by these phases is 

inhibited, however, by the formation of highly stable carbonate complexes, by the alkaline pH, and by local evaporative 

conditions that can produce elevated salinity in pore waters 

(Hsi and Langmuir, 1985; Ho and Miller, 1986).

 Considering the above discussion, the oxic near-surface 

environment surrounding the Fry Canyon project site offers 

little to impede the solubility and mobility of uranium. Minimal sequestration of dissolved U(VI) in the local environment dictates use of permeable reactive barriers that employ 

efficient sorbents or surface complexers of U(VI), or chemical reductants that convert U(VI) to highly insoluble U(IV) 

(Wilkowski and others, 2002). Calculations with PHREEQC 

indicated that precipitation of uraninite from uranium-rich 

water of well W15 composition requires Eh values lower than 

0.15 volt. Eh values well below 0.15 volt are reported in pore 

waters of the PRB-containing reductant of zero-valent iron 

(Wilkowski and others, 2002).
Geology, Geophysics, and Geochemistry 23

Figure 16. Plot showing degree of saturation of sampled waters 

with respect to a variety of minerals, including uranium minerals. 

An Eh of +0.4 volt was assigned to these oxygen-bearing waters. 

Most waters are undersaturated with respect to most minerals, 

as indicated by plotted positions below the equilibrium saturation 

reference line. IAP, ion activity product; Ksp, equilibrium 

saturation product.

Figure 17. Plot of dissolved uranium concentration as a function 

of sampling-site location (fig. 2) along the main stem of Fry Creek. 

The location of the Fry Canyon project site is shown for reference 

as is the USEPA drinking-water standard of 30 micrograms per liter.

Equilibrium saturation

Quartz

Calcite

Dolomite

Ferrihydrite

Gypsum

Tenorite

Malachite

Carnotite

Schoepite

Rutherfordine

Tyuyamunite

Uranophane

Uraninite

Coffinite

MINERAL

SATURATION INDEX = log(IAP/Ksp)

4

2

0

–2

–4

–6

–8

–10

–12

–14

–16

–18

–20

300

250

200

150

100

50

00 1 2 3 4 5

W11 W12

W10

W9

W1

W2

W4,5,6

W3

W7

W8 USEPA Drinking-Water Standard

Fry Canyon tailings site

DOWNSTREAM IN FRY CREEK,

IN KILOMETERS

Seeps and Surface Waters

URANIUM,

IN MICROGRAMS PER LITER

Spatial Distribution of Dissolved Uranium

Dissolved uranium concentrations in seeps and surface 

waters of Fry Creek ranged from 40 to 60 μg/L upstream from 

the Fry Canyon project site but increased abruptly to 150 μg/L 

at the first stream location (W9) sampled downstream from 

the site (fig. 17). Dissolved uranium concentrations continued 

to increase in a downstream direction and plateau at values of 

approximately 250 μg/L. These observations indicate that sitederived uranium is contributing to uranium load in the stream 

and that uranium stored in downstream sediments may be an 

additional source of dissolved uranium. Uranium isotopes 

(see subsequent discussion) can be used to identify contributions of natural and site-derived uranium in these more 

downstream waters.

An additional possibility is that downstream concentrations of uranium from all sources are increased by evaporative concentration in places where surface flow is sluggish 

or where stream water infiltrates the shallow (less than 1 m) 

alluvium. This hypothesis is supported by the greater dissolved-solids content (approximately 30 percent) in downstream waters (table 2) and by observed efflorescent crusts 

of “white alkali” salts in dry or slightly moist portions of the 

streambed (fig. 18). These salts are brought to the surface 

by capillary action during evaporation from a shallow water 

table and consist predominantly of highly soluble sodium 

sulfate and sodium-magnesium sulfates. Dissolution of these 

salts from stream sediments or local soils likely influences 

the major-ion chemistry of both surface water and shallow 

groundwater (table 2).

Uranium Isotopes

The 234U/238U activity ratios (AR) of seven baseline 

samples (W1–W7) collected upstream from the Fry Canyon 

project site had a mean value of 1.235±0.069 (table 2). Values 

of AR greater than the radioactive equilibrium value of 1.0 are 

common in surface waters and result from preferential leaching and decay-induced recoil of 234U during slow weathering 

of uranium-bearing rocks and minerals (Osmond and Cowart, 

1976). In contrast, four stream waters collected downstream 

from the site (W9–W12) all have AR values in the narrow 

range of 1.048–1.064, suggesting that any added site-derived 

uranium had an AR value less than 1.05 (fig. 19). Persistence 

of this isotopic composition in downstream samples indicates 

that at the time of sampling, additional mixing with isotopically distinct sources of “natural” uranium of AR~1.2–1.3 

was minimal.
24 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

Figure 19. Plot of 234U/238U activity ratio (AR) of water as a function 

of sampling-site location (fig. 2) along the main stem of Fry Creek. 

The location of the Fry Canyon project site is shown for reference.

W3

W5,6,7

W1

W4

W8

W2

W9

W10 W11 W12

0 1 2 3 4 5

DOWNSTREAM IN FRY CREEK,

IN KILOMETERS

Fry Canyon tailings site

1.3

1.25

1.2

1.15

1.1

1.05

1

Seeps and Surface Waters

234U/238U ACTIVITY RATIO

The four contaminant plume wells (W15–W18) had 

a mean AR of 0.939±0.011 (table 2). Values of AR<1.0 in 

the contaminant plume result from aggressive leaching of 

mined Cu-U ores and host rock by sulfuric acid in the heapleach pile. Rapid and nearly quantitative removal of uranium 

minimizes fractionation of uranium isotopes and produces 

AR values in leachates that mimic AR values of the original 

ore/rock. A plot of AR compared to 1/U (fig. 20) indicates 

that three monitoring wells in the cottonwood well field 

(W13, 14, 20) located approximately 0.5 km downgradient from the Fry Canyon project site (fig. 2, table 2) have 

AR values that fall on a linear mixing trend line connecting 

the average AR of contaminant plume wells (0.939) and the 

AR for the upstream Fry Spring well (1.282). Site-derived 

uranium was expected in the monitoring wells considering 

their relatively high concentrations of dissolved uranium 

(380–578 μg/L, table 2). Simple isotope mass-balance calculations using the end member AR values cited previously 

indicate that approximately 78–87 percent of uranium in the 

monitoring wells is site-derived. Similar mixing proportions 

based on chemical mass balance can be calculated using 

assumed average uranium concentrations in the end members, 

but because uranium concentrations are more temporally variable than uranium isotopic ratios, the isotope-based approach 

is more robust. As remediation activities progress on the site, 

uranium isotopes will continue to indicate mixing proportions 

in these wells, even as concentrations decrease to near-baseline levels.

The four surface-water samples collected downstream 

from the Fry Canyon site also fall on the mixing trend line 

and indicate consistently high percentages (about 67 percent) 

of site-derived uranium. Horizontal scatter of these points 

about the mixing line is probably caused by evaporation that 

Figure 18. Photograph of view upstream from water-sampling 

site W1 in Fry Creek. Deposits of white sodium sulfate and 

sodium-magnesium sulfate salts form evaporative crusts in the 

dry streambed.

affects uranium concentration but not isotopic composition. 

Likewise, predominantly horizontal scatter of most plotted values for upstream baseline samples indicates variable 

dilution of a composition similar to the Fry Spring well. One 

stream sample (W8) collected adjacent to the Fry Canyon 

project site plots to the right of the mixing line, indicating that 

it has too low a uranium concentration for its AR. This sample 

is a mixture of bank seepage from the site plus streamflow 

and was collected from stagnant water containing abundant 

organic debris. Some dissolved uranium may have been 

removed by local reducing conditions within the adjacent bank 

or in the streambed. In addition, complex organic compounds 

were used as frothing agents in processing ores at the site. 

Biodegraded remnants of these compounds occur in sediment 

in the pits and may be present in these waters and act as additional reductants.

Although not a major process affecting the sampled 

waters, chemical reduction of dissolved uranium has the same 

effect on plotted points as dilution; AR values remain effectively unchanged as uranium concentration decreases (1/U 

increases). Pore waters within the zero-valent iron PRB should 

therefore plot within a broad horizontal field delimited in the 

vertical dimension by AR values similar to the contaminant 

plume wells. Mixing relationships between such pore waters 

of variable and low uranium concentration and local waters 

would generate a cloud of plotted points on the right half of 

figure 20.
Geology, Geophysics, and Geochemistry 25

Figure 20. Plot of 234U/238U activity ratio (AR) compared to 

dissolved uranium concentration in waters of this study. AR values 

of low-uranium waters collected upstream from the Fry Canyon 

project site are greater than 1.0, whereas AR values of well 

waters from the uranium-rich contaminant plume are all less than 

1.0. Most other sampled waters lie along a mixing line connecting 

these two end-member types.

Figure 21. Plot of δ34S of dissolved sulfate compared to dissolved 

sulfate concentration in waters of this study. Most waters plot in 

a narrow range of values that includes uncontaminated waters 

collected upstream from the Fry Canyon project site. Exceptions 

include chemically distinct, sulfate-rich water from the center of 

the contaminant plume (W15) and one stream water (W8) possibly 

affected by sulfate reduction.

Sulfur Isotopes

The sulfur isotopic composition (δ34S) of sulfate in most 

of the measured waters plots in the narrow range of –2.4 to 

–5.4 per mil (fig. 21). This range includes all of the upstream 

(baseline) waters (table 2) and indicates that at the time of 

sampling, dissolved sulfate in most of the measured waters 

was dominantly of natural origin. Local dissolved sulfate is 

derived by solution of sparingly soluble gypsum and more 

soluble “white alkali” salts in colluvium, alluvium, and 

eolianite. The original source of sulfur is sulfide minerals 

present in Paleozoic and Mesozoic sedimentary rocks that 

underlie the region and are exposed on mesas that provide 

topographic relief.

An important exception to sulfur isotopic uniformity is 

plume well W15, which has δ34S of –13.3 per mil. This composition may represent another component of sulfate derived 

from the heap leach pile. Sources of sulfur in the heap-leach 

pile include sulfide and sulfate minerals in the various Cu-U 

ores transported to the site, and sulfur in the applied sulfuric 

acid. Other plume well waters of somewhat elevated dissolved 

sulfate concentration do not lie along a mixing trend line 

anchored by W15 (fig. 21). Instead, they trend in the opposite 

direction toward less negative δ34S values. At times of higher 

water levels, the plume wells near W15 may be more influenced by natural sulfate derived from the host stream terrace. 

The bench also hosts a series of ponds that were formerly settling ponds used in the uranium upgrading operations (figs. 3 

and 5). Ponds were supplied with local sulfate-bearing water 

that underwent evaporative concentration and percolated into 

the underlying bench sediments. During drier periods when 

the contaminant plume is a bigger contributor to a thinner 

saturated zone, wells near W15 may be more influenced by 

heap-leach or tailings-derived sulfate (Naftz and others, 2006). 

Another exception is stream water W8 collected adjacent 

to the Fry Canyon project site and exhibiting δ34S of +1.8 per 

mil. This isotopically heavier composition could result from 

local sulfate-reducing conditions in the streambank or streambed that favor the lighter 32S isotope and therefore enrich 

remaining dissolved sulfate in 34S. Note that this same water 

had unusually low uranium concentration for its AR value, 

suggestive of chemical reduction of dissolved uranium.

Sulfur isotope measurements indicate two isotopically distinct sources of sulfate in plume wells, but this is not the case for 

dissolved uranium. The extremely large contrast in uranium concentration (about 400×) between the contaminant plume composition (W15) and natural waters produces a wider halo of dominant 

uranium contamination in the network of plume wells.

1.3

1.25

1.2

1.15

1.1

1.05

1

0.95

0.9

0 0.005 0.01 0.015 0.02 0.025 0.03

1/U

234U\238U ACTIVITY RATIO

URANIUM,

IN MICROGRAMS PER LITER

1,000 200 100 66.6 50 40 33.3

Fry Spring Fry Spring well

Stream

above site

Seep Seep

Upstream bed storage

Stream at site

Seep

Seep 50:50 mix

Downstream surface waters

Mixing

Dilution Evaporation

Downstream wells

Contaminant plume wells

SULFATE,

IN MILLIGRAMS PER LITER

1,000 500 333 250 200 167

W8

Sulfate reduction

Native sulfate field

Mixing line

W15 contaminant plume

0 0.001 0.002 0.003 0.004 0.005 0.006

1/SO4

δ34S (PER MIL)

2

0

–2

–4

–6

–8

–10

–12

–14
26 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

Sediment Chemistry and Mineralogy

Two 60- to 120-mesh size fractions collected from the slope 

of tailings adjacent to Fry Creek (T1, T2, fig. 2, inset; also fig. 3) 

are obviously enriched in uranium (100×) and copper (130–180×) 

compared to the same size fraction from “baseline” stream 

sediment sample S1 (fig. 2, inset; table 3). Other trace elements 

showing lesser enrichments in tailings include lead (4×), zinc 

(10×), and arsenic (6–9×). Chemical indications of tailings contributions to sediments S2–S7 located downstream from the site 

are primarily based on enrichments compared to S1 and are most 

obvious for copper in S2 (2×), which is approximately 0.1 km 

downstream from the tailings (fig. 2). Smaller apparent enrichments (1.15–1.35×) of uranium, lead, and zinc in S2 are too small 

to confidently exceed (by 2 standard deviations) the mean of their 

concentrations in more downstream samples. Copper concentration in sample S5 (13.4 μg/g) is anomalously high compared to 

most of the sediment samples but not compared to S1. Concentrations in S7 are probably influenced by additional detritus contributed by tributary drainages to Fry Creek (fig. 2).

Sulfide grains in the magnetic fraction of tailings sample T1 identified under reflected light illumination (fig. 22 A–F) 

were predominantly pale brassy yellow chalcopyrite [CuFeS2], 

with lesser amounts of beige-white pyrite [FeS2] and much rarer 

grains of peacock-blue bornite [Cu5FeS4] (fig. 22C ). Pyrite is 

nonmagnetic, but magnetic properties could result from partial 

alteration to various secondary iron oxides (observed), formation of composite grains of pyrite with chalcopyrite (observed), 

or incorporation of some copper in the pyrite structure. Chalcopyrite and pyrite grains showed variable amounts of alteration to 

secondary iron oxides that coat grains, fill fractures, or replace 

original sulfide. In addition, many chalcopyrite grains showed 

uneven, pitted polishing surfaces perhaps caused by chalcopyrite growth as pore fillings around other, now-absent phases. 

The distinctive large and highly reflective grains of chalcopyrite constitute perhaps 10 percent of the grains in the magnetic 

concentrate from the tailings. A few grains in the T1 concentrate 

contained rounded forms of framboidal pyrite enclosed by nonreflective matrix that is probably partly degraded organic matter 

(fig. 22B). Rare pale green grains or grain coatings observed 

under a binocular microscope in the T1 magnetic concentrate 

are probably fine-grained malachite [Cu2(CO3)(OH)2] or azurite 

[Cu3(CO3)

2

(OH)2]. Specimens of these brightly colored copper 

minerals can be found at scattered locations throughout the Fry 

Canyon site.

The thin section of magnetic minerals from baseline 

sediment S1 contained numerous grains coated by, or altered to, 

secondary iron oxides that appear in various shades of gray, bluegray, or blue-white under the immersion oil and reflected light 

illumination. Some of these grains may be former sulfide minerals of natural origin that have completely altered during their 

prolonged history of oxidative weathering, transport, and withinstream reworking. A few rare grains contained occasional tiny 

inclusions of relict pyrite of probable natural origin. 

The most downstream sediment sample, S7, had no 

sulfide grains in thin section. The other magnetic mineral 

concentrates of sediment samples S2–S6 contained from 

1–9 grains of tailings-derived sulfides in thin section. As 

expected, the number of tailings-derived sulfides in thin 

sections tended to decrease with increasing (downstream) 

distance from the tailings source [S2(9), S3(6), S4(2), S5(7), 

S6(1)], but limited sample size and rarity of target sulfide 

grains precludes strict quantitative comparisons. Temporal 

and spatial variations in stream-channel morphology influence 

flow patterns and can concentrate heavy minerals in small 

areas of streambed that may not be uniformly sampled. Sampling of such an area could explain the relatively large number 

of sulfide grains (7) in sample S5 (fig. 22G–K), collected 

approximately 1.3 km downstream from the tailings source.

Backscatter electron image and X-ray intensity maps 

for copper, iron, and sulfur generated by electron microprobe 

scans of thin section T1 (fig. 23) confirmed relatively abundant chalcopyrite (CuFeS2

) compared to pyrite (FeS2) and also 

identified rare grains of a more copper-rich sulfide (bornite?). 

Other grains containing lower concentrations of copper probably are chalcopyrite, now variably altered to iron oxides. 

Many grains of low iron content seen on the iron map are 

other minerals coated by iron oxides.

Table 3. Concentrations of selected trace elements (μg/g) in the 60–120 mesh size fraction of tailings and stream sediments, 

Fry Canyon, Utah.

[μg/g, microgram per gram; **, probably enriched; *, possibly enriched]

Sample Copper Uranium Lead Zinc Chromium Vanadium Arsenic Manganese

Tailings T1 1,890 89 16 104 5.7 11.3 22.7 166

Tailings T2 2,690 124 21 104 5.5 12.5 29.6 135

Sed 1 ( baseline) 14.5 1.0 5.3 11.2 5.2 11.4 3.9 526

Sed 2 27.2** 1.3* 6.1* 14.8* 5.1 14.9 4.0 231

Sed 3 11.9 1.1 5.5 10.7 5.2 14.3 3.2 243

Sed 4 8.4 1.1 5.1 10.1 4.0 11.1 2.3 254

Sed 5 13.4* 1.1 5.5 13.7 5.6 14.5 3.1 250

Sed 6 9.2 1.2 5.9 13.3 4.8 12.6 2.4 262

Sed 7 3.0 0.9 5.4 12.7 5.5 11.7 2.2 222
Geology, Geophysics, and Geochemistry 27

100 micrometers

100 micrometers

100 micrometers

100 micrometers

100 micrometers

100 micrometers

Figure 22. Photographs of variably altered pyrite and chalcopyrite grains in the magnetic fraction of the 60–120 mesh 

size fraction of tailings sample T1 (A–F ), and in downstream sediment S5 (G–K), and S6 (L). Note scale bars for reference. 

(A) Pitted chalcopyrite (left) and more altered pyrite (?) (right) showing a rim and fracture fillings of iron oxides, (B) pyrite 

framboids variably altered to iron oxides and suspended in a matrix of quartz and organic matter, (C) rare bornite grains 

showing characteristic blue color under reflected light, (D) pyrite cemented by iron oxides and quartz, (E) cluster of pitted 

chalcopyrite grains including one composite grain (left) containing pyrite inclusions, (F ) cluster of chalcopyrite grains, 

(G) angular grain of chalcopyrite, (H) pyrite grain showing extensive replacement by iron oxides, (I ) chalcopyrite with a 

thick rim of banded silica and iron oxide, (J, K) relatively unaltered chalcopyrites, (L) organic-bearing grain with abundant 

rounded microinclusions of pyrite.
28 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

100 micrometers

100 micrometers

100 micrometers

100 micrometers

100 micrometers

100 micrometers

Figure 22—Continued. Photographs of variably altered pyrite and chalcopyrite grains in the magnetic fraction of the 

60–120 mesh size fraction of tailings sample T1 (A–F ), and in downstream sediment S5 (G–K), and S6 (L). Note scale bars for 

reference. (A) Pitted chalcopyrite (left) and more altered pyrite (?) (right) showing a rim and fracture fillings of iron oxides, 

(B) pyrite framboids variably altered to iron oxides and suspended in a matrix of quartz and organic matter, (C) rare bornite 

grains showing characteristic blue color under reflected light, (D) pyrite cemented by iron oxides and quartz, (E) cluster of 

pitted chalcopyrite grains including one composite grain (left) containing pyrite inclusions, (F ) cluster of chalcopyrite grains, 

(G) angular grain of chalcopyrite, (H) pyrite grain showing extensive replacement by iron oxides, (I ) chalcopyrite with a 

thick rim of banded silica and iron oxide, (J, K) relatively unaltered chalcopyrites, (L) organic-bearing grain with abundant 

rounded microinclusions of pyrite.
Summary and Conclusions 29

Summary and Conclusions 

Geologic mapping, cross sections, and resistivity profiles 

at the Bureau of Land Management Fry Canyon project site in 

San Juan County, southeastern Utah, show the following:

1. Bedrock is composed of thick eolian sandstone beds and 

interbedded thinner, fine-grained sandstones and siltstones 

of the Cedar Mesa Sandstone Member of the Permian 

Cutler Formation.

2. Thick beds of sandstone form stairstep bedrock ledges on 

the flanks of the valley of Fry Creek; ore-processing companies used these ledges for siting operations. Some ledges 

are buried beneath unconsolidated valley-floor deposits.

3. Bedrock is mantled by late Quaternary to Holocene 

reddish-brown deposits of eolian sand and silty sand, 

which commonly contain thin lenses of colluvium derived 

locally from exposed, weathered ledges of the Cedar 

Mesa sandstone.

4. Along the valley bottom through the study area, older 

alluvial gravels intertongue with eolian sand deposits and 

coluvium adjacent to the modern channel of Fry Creek; 

these sediments fill a paleochannel as much as 1–2 m 

deeper than the modern channel of Fry Creek.

5. The paleochannel seems to be configured as portrayed 

in figure 24 based on exposed bedrock outcrop along the 

modern channel, drilling data, and geophysical profiles.

Figure 23. Backscatter electron image (BSE) (upper left) and corresponding X-ray intensity maps for copper, 

sulfur, and iron for a portion (8 square millimeters) of thin section T1 containing magnetic minerals from the 

tailings location. The X-ray intensity maps are displayed on a color scale: low-intensity pixels are represented 

by blue, and highest intensity areas are represented by red to pink.
30 Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah

6. In the vicinity of the ore-processing site, the modern 

channel of Fry Creek is narrower than this paleochannel; 

Fry Creek flows on bedrock only locally and alternately 

follows and crosses the trace of the paleochannel.

7. For at least 0.5 mi (0.8 km) upstream to the south of the 

Highway 95 bridge, the paleochannel deposits are eroded 

completely and the modern stream and its thin alluvium 

rest on bedrock; the northern limit of the paleochannel 

was not delineated in this study, but it lies north of geophysical profile FC–4.

8. Five of the ponds at the project site sit on a bench 

composed of eolian sand, colluvium, and gravels of 

the paleochannel.

9. Groundwater contamination from the ponds and other 

operations at the site appears to follow the paleochannel 

and geophysical surveys indicate that the paleochannel 

extends north to the location of FC–4; however, contamination in paleochannel groundwater may be substantially 

diluted to the north by influxes of fresher water associated with the modern channel or springwaters along the 

FC–4 profile.

Figure 24. Map of the Fry Canyon project study area showing modern channel and possible 

position of the paleochannel along the floor of Fry Creek. The light-gray shaded area may 

include a lower paleochannel and a higher, older paleochannel. This area needs to be tested 

for sediment thickness and the presence of contaminated groundwater. The older paleochannel 

north of the barn may contain substantial fresh groundwater.

10. An older, higher paleochannel marked by high-standing 

gravels is present along part of the stream valley but does 

not seem to carry contaminated groundwater as it is not in 

contact with water in the stream or the paleochannels. North 

of the ranch and barn at the location of FC–4, this channel 

may contain springwater derived from local bedrock.

11. Groundwater, some of it likely contaminated, has moved 

into fractured bedrock at selected localities.

Well-water sample W15 collected from the center of the 

contaminant plume has a distinctive Ca-Mg-SO4-dominant 

chemistry that indicates major sourcing of dissolved solids from 

the heap-leach pile. Other distinctive characteristics of this water 

include highest dissolved uranium concentration (18,700 μg/L) 

and markedly more negative δ34S composition (–13.3 per mil), 

the latter indicating distinctive sources of sulfur provided by the 

heap-leached Cu-U ores and(or) the sulfuric acid leachate.

The 234U/238U activity ratios (AR) of uranium in W15 water 

and nearby well waters influenced by the contaminant plume 

are all less than 1.0, the result of aggressive, sulfuric acid-based 

leaching of uranium from Cu-U ore in the heap leach pile. In 

contrast, the AR values of uranium in waters collected upstream 

0 400 METERS

0 300 600 900 1,200

100 200 300

1,500 FEET

N

Paleochannel: zone with 

documented contamination

Paleochannel: possible contamination

Ranch 

house

Tailings

Ponds

 Active 

channel

 Fry 

Spring

Paleochannel:

 baseline water 

 quality

 Active 

channel

Cottonwood

Paleochannel: 

possible 

contamination

Well field

Barn

Radium King Road

?

?
References Cited 31

from the Fry Canyon project site are all greater than 1.0 and result 

from natural weathering and dissolution of uranium by local 

waters. This isotopic contrast can be used to identify and quantify 

the amount of site-derived uranium in well water and surface 

water collected downstream from the site. Uranium isotopic data 

provide particularly useful confirmation of uranium contamination in water that has marginally elevated uranium concentrations 

compared to natural baseline values.

 Analysis of copper in the 60- to 120-mesh size fraction of 

stream sediments provided chemical indications of the downstream dispersion of contaminant chalcopyrite grains. Modern 

analyses by ICP–MS are highly sensitive and precise, but chemical detection of added chalcopyrite is limited by large dilution 

factors and natural variability in baseline copper concentrations. 

In Fry Creek the chemical data confidently indicated addition of 

chalcopyrite particles at a location 0.1 km downstream from the 

tailings (S2) but not at 0.4 km downstream (S3).

Optical microscope observations or measurements with 

the electron microprobe or scanning electron microscope can 

be used to identify distinctive tailings-derived chalcopyrite 

grains in thin sections of magnetic mineral concentrates. Chalcopyrite identifications in stream sediments provide a sensitive 

qualitative indication of downstream dispersion of contaminants, but tracking of rare sulfide grains over large distances is 

hampered by large dilution factors and nonuniform sampling 

of stream sediments. In Fry Creek the tailings-derived sulfide 

particles are greatly diluted by resuspended sediment and 

sediment newly added during floods. Despite this dilution, 

tailings-derived sulfide particles were confidently detected at a 

location (S5) 1.3 km downstream from the streamside tailings.

Use of 234U/238U activity ratios (AR) to identify uranium 

contamination in water should be generally applicable at other 

sites of uranium mining, milling, or processing provided that 

there is good contrast between the uranium isotopic composition of site-derived uranium and local dissolved uranium. At 

Fry Canyon and elsewhere, tracing of distinctive site-derived 

particles such as ore sulfides in stream sediments (or air samplers) is possible by bulk chemical analysis or individual particle identification, but the general success of these methods 

will depend upon the amount of particle dilution as a function 

of downstream (or downwind) distance.

Acknowledgments

B.R. Lewis of the Bureau of Land Mangement encouraged USGS involvement in this study and provided background 

information, advice, and logistical support. C.A. Rosson and 

associates at SAIC Engineering, Inc., provided three well-water 

samples (W18, 19, 20). Uranium isotope data were provided 

by Professor M.E. Ketterer of Northern Arizona University. 

Sulfur isotope determinations were by C.A. Johnson; chemical 

analyses of waters and sediments were by J.H. Bullock, Jr.; and 

electron microprobe measurements were by H.A. Lowers, all of 

the USGS. Other USGS employees who contributed technical 

advice or analytical support are R.L. Driscoll, N.S. Fishman, 

D.L. Naftz, D.R.Van Sistine, and R.B. Wanty.

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Appendixes

Appendix 1. Description of Disturbed Areas 35

Appendix 1. Description of Disturbed Areas

Disturbed Area at the Ore-Processing Site

Activities at the Fry Canyon site produced an irregular 

disturbed area (shaded and labeled “d”, fig. 5) about 900 by 900 ft 

(275 by 275 m). The disturbed area includes the following (locations with number and letter designations shown in fig. 5):

• Six tailings ponds (nos. 1–6), tailings, and contaminated 

fill that rest on a bench (Qeb) adjacent to Fry Creek;

• One large heap-leach pile (hlp), which apparently rests 

on thin Qec;

• Substantial areas of slope wash from the eroding banks 

of the heap-leach pile (marked by arrows);

• Several piles of copper ore that rest on thin Qec or 

sandstone (“ore” and “ore piles”);

• Several concrete leach vats and other metal recovery 

features (f) that rest on sandstone ledges;

• Large bulldozed areas where native soils are disturbed 

(d) and sandstone bedrock (ss) is commonly exposed;

• Ponded stream sediment (ps, upslope side of access road);

• Radioactive slime pile (s);

• Linear pile of bulldozed sandstone rubble (r);

• Pile of rusted scrap iron (m);

• Erosional gullies (two arrowed lines); and

• Other small ponds (nos. 7, 8, 9).

Most of the listed features show varying amounts of 

radioactivity, each above the background levels observed at 

the site (1.5–2.5 mR/hr (microroentgen per hour) for units Pcc 

and Pcb, and 2.5–4.0 mR/hr for unit Qec).

Other Disturbed Areas

West of the access road to the site and just west of the 

ore-processing area is a large pile of debris that includes 

remnants of trailers, old equipment, and other waste (j, fig 5). 

To the northeast of Fry Creek, opposite the main area of 

disturbance, is a “cowboy” shack (cs, fig. 5) and an old foundation (f, fig. 5). Remnants of roads and the foundation of a 

smaller structure (not mapped) are in this area. No anomalous 

radioactivity was noted at these sites. The northwest-trending 

linear map area of unit Pcb, surrounded by unit Qeb to the 

northeast and across the creek from pond 5, has several piles 

of radioactive ore and slimes sitting on the sandstone bald.

A substantial disturbed area, located around the ranch 

north of the project site, is associated with the access roads to 

the ranch house, a car shed, a barn, and a bulldozed area (rh, 

cs, b, and d, fig. 4). The area around the barn is fenced (dashdot line, fig. 4), and the bench (Qeb) surface that extends 

southeast of this fenced area almost to a large cottonwood tree 

is also fenced (not shown).

Two berms along the stream bottom form small ponds for 

stock use (w, fig. 4) adjacent to the barn. Five areas with piles 

of uranium ore or remnants of such piles are located adjacent 

to road surfaces just to the southwest of the ranch house (ore, 

fig. 4). Some of this material washes across the main entry 

road surface (mer, fig. 4). The piles range from a few hundred 

to more than 5,000 mR/hr (limit of the instrument), thereby 

posing some hazard to local residents and visitors.

In the Fry Spring area south of the project site (fig. 6), a 

road provides access to the spring (FS, fig. 6), which is on a 

stream terrace on the west side of Fry Creek. The spring was 

developed by digging a rectangular pit with a backhoe into the 

stream terrace alluvium to depths below the water table. The 

stream terrace contains a substantial zone of groundwater seeps, 

and there is a small natural spring in the bottom of a small 

wash at the southern end of this stream terrace. Groundwater at 

this locality is believed to be derived from the area of mapped 

upland Qec that lies west and south of the stream terrace. A 

large disturbed area (d, fig. 6) lies on the east side of the creek 

on a bench formed by a ledge of sandstone. A pit and trench (t) 

are located west of Fry Spring (fig. 6), and other features, such 

as a dugout and building foundations (not shown), are located 

on Qeb and sandstone ledges west and northwest of Fry Spring. 

An old road extends back to the ore-processing site from the Fry 

Spring access road near the spring to the northwest.

Appendix 2. Apparent-Resistivity Pseudosections and Inversion Results 37

Appendix 2. Apparent-Resistivity Pseudosections and Inversion Results 

for The Fry Canyon Resistivity Lines

Figures 25–28 in this Appendix provide further information regarding the four geophysical profiles in figures 10, 11, 

12, and 13, respectively. The data plots are in EarthImager 2D 

format (Advances Geosciences Inc., 2003). Each plot has three 

panels. The top panel shows the measured apparent-resistivity 

pseudosection and data points. The middle panel shows the 

calculated apparent-resistivity pseudosection, based on the 

Figure 25. Supporting information for direct-current resistivity profile FC–1. See figure 10 and explanation of the panels in the section 

on direct-current resistivity surveys.

inversion results. The bottom panel shows the topographycorrected, inverted resistivity section. Note the color scale varies from plot to plot, and the horizontal and vertical scales are 

significantly different. Gaps in the subsurface data are shown 

by missing points in the first two panels. Cross-section areas 

with substantial data gaps result in poorly constrained model 

resistivity values in the final figures.
38 Geology, Geochemistry, and Geophysics of the Fry Canyon Project Uranium/Copper Site, Southeastern Utah

Figure 26. Supporting information for direct-current resistivity profile FC–3. See figure 11 and explanation of the panels in the section 

on direct-current resistivity surveys.

Figure 27. Supporting information for direct-current resistivity profile FC–2. See figure 12 and explanation of the panels in the section 

on direct-current resistivity surveys.
Appendix 2. Apparent-Resistivity Pseudosections and Inversion Results 39

Figure 28. Supporting information for direct-current resistivity profile FC–4. See figure 13 and explanation of the panels in the section 

on direct-current resistivity surveys.

Publishing support provided by:

Denver Publishing Service Center, Denver, Colorado

Manuscript approved for publication, April 3, 2010

For more information concerning this publication, contact:

Center Director, USGS Central Energy Resources Science Center

Box 25046, Mail Stop 939

Denver, CO 80225

(303) 236-1647

Or visit the Central Energy Resources Science Center Web site at:

http://energy.cr.usgs.gov/

This publication is available online at:

http://pubs.usgs.gov/sir/2010/5075/
Otton and others—Geology, Geochemistry, and Geophysics of the Fry Canyon Uranium/Copper Project Site, Southeastern Utah—USGS/SIR 2010–5075

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