U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 2010–3050

January 2011

Breccia-Pipe Uranium Mining in Northern Arizona—

Estimate of Resources and Assessment of Historical Effects

findings will be used in an environmental 

assessment process to examine the potential effects of future mining activities. This 

fact sheet summarizes USGS research 

completed through December 2009 and 

presented in USGS Scientific Investigations Report 2010-5025 (Alpine, 2010; 

http://pubs.usgs.gov/sir/2010/5025/).

Background

Some of the highest grade uranium 

ore in the United States occurs in breccia 

pipes scattered across the Grand Canyon 

region (fig.1). These breccia pipes, named 

for their vertical, pipe-like shape and the 

broken rock, or breccia, that fills them, 

range from 300 to 500 ft in diameter at 

depth. They were formed millions of years 

ago when groundwater dissolved carbonate rock and created vertical cavities into 

which surrounding rock collapsed. Later, 

highly mineralized groundwater from 

overlying or underlying rocks, moving vertically through the porous breccia, deposited ore minerals—including 

uranium—in some of the pipes. When 

exposed to the atmosphere, either naturally 

through erosion or by mining, these minerals may be dissolved or broken down and 

dispersed by wind and water.

Uranium mining in the Grand Canyon region peaked in the 1980s. However, 

there is now renewed interest in the exploration and mining of breccia pipes in the 

region—uranium prices have increased, 

and concerns about clean energy and 

energy independence also have focused 

attention on uranium and nuclear energy. 

Currently, there are 104 U.S. nuclear 

reactors, which annually consume about 

27,500 tons of uranium oxide, the primary 

constituent of the fuel rods that power 

them. Each year, about 1,750 to 2,250 

tons of uranium oxide are mined domestically. The remainder of the uranium oxide 

needed to fuel U.S. reactors comes from 

foreign sources, primarily Canada, and the 

U.S. utility inventory. 

Increased mining in northern Arizona could help meet the U.S. demand for 

uranium but could also increase the amount 

of uranium and other trace elements in 

the local surface water and groundwater 

About 1 million acres of Federal land in the Grand Canyon region 

of Arizona were temporarily withdrawn 

from new mining claims in July 2009 by 

the Secretary of the Interior because of 

concern that increased uranium mining could have negative impacts on the 

land, water, people, and wildlife. During 

a 2-year interval, a Federal team led 

by the Bureau of Land Management is 

evaluating the effects of withdrawing 

these lands for extended periods. As part 

of this team, the U.S. Geological Survey 

(USGS) conducted a series of short-term 

studies to examine the historical effects 

of breccia-pipe uranium mining in the 

region. The USGS studies provide estimates of uranium resources affected by 

the possible land withdrawal, examine 

the effects of previous breccia-pipe 

mining, summarize water-chemistry data 

for streams and springs, and investigate 

potential biological pathways of exposure to uranium and associated contaminants. This fact sheet summarizes results 

through December 2009 and outlines 

further research needs.

Introduction

Citing concerns that uranium mining could have adverse effects on the 

Grand Canyon watershed, its people, and 

wildlife, on July 21, 2009, Secretary of 

the Interior Ken Salazar withdrew about 1 

million acres of Federal land near Grand 

Canyon from new mining claims for 2 

years. Mining of uranium can release 

toxic and hazardous substances to the 

environment. These include uranium 

itself, which is a toxic chemical and can 

pose a radiation hazard, and arsenic and 

other toxic trace metals. At the Secretary’s request, the U.S. Geological Survey 

(USGS) conducted a series of short-term 

studies to examine the effect of brecciapipe uranium mining in the region. USGS 

Figure 1.  The Kanab North Mine is one of several breccia-pipe uranium mines in northern Arizona.

USGS scientists conducted field assessments at this mine, where operations are currently on

standby (USGS photo by Don Bills).
Bright Angel

Creek

Cataract Creek

Havasu Creek

Little Color a do River

Kanab Creek

Virgin River

Col o rado River

Colorado River

U.S. Bureau of Land Management

U.S. Forest Service

Tribal land

National Park Service

State land

Private land

Flagstaff

Phoenix

NEVADA

CALIFORNIA ARIZONA

UTAH

COLORADO

NEW MEXICO

Index map

EXPLANATION

Segregation area—Boundary

National Monument—Boundary

Washington

St. George

Littlefield

Peach Springs

Valle

Tusayan

Marble

Canyon

Lees

Ferry VERMILLION CLIFFS

NATIONAL

MONUMENT

Jacob

Lake

Kanab

Fredonia

PIPE SPRING NM

KAIBAB -

PAIUTE

RESERVATION

Colorado City

Big Water

Supai Village North Rim

HAVASUPAI

RESERVATION

NORTH

SEGREGATION

AREA

Hack Canyon

EAST

SEGREGATION

AREA

HUALAPAI

RESERVATION

GRAND CANYON NATIONAL PARK

GRAND CANYON - PARASHANT

NATIONAL MONUMENT

KAIBAB NATIONAL FOREST

NAVAJO

RESERVATION

LAKE MEAD

NRA

GRAND STAIRCASE ESCALANTE

NATIONAL MONUMENT

LAKE

MEAD

NRA

114°00' 113°30' 113°00' 112°30' 112°00' 111°30'

37°00'

36°30'

36°00'

35°30'

UTAH

ARIZONA

0 25 50 MILES

0 25 50 KILOMETERS

Data provided by U.S. Geological Survey and 

Bureau of Land Management.

Map created on 11/10/09 by K.M. Brown

Map revised on 5/24/10 by T. Arundel

SOUTH

SEGREGATION

AREA

flowing into Grand Canyon National Park 

and the Colorado River. Deep mining 

activities could allow uranium and other 

trace elements to be mobilized by water 

and transported into perched water-bearing 

zones and the regional aquifer, which are 

sources of water for local communities and 

feed springs used by recreationists, fish, 

and other wildlife. Additionally, waste rock, 

ore, and dust from mined areas, if not properly managed, could be transported away 

from the mines by wind and flood events.

The Secretary of the Interior cited 

such concerns when he withdrew Federal 

land near Grand Canyon from new mining 

claims for 2 years. The land proposed for 

withdrawal comprises three parcels(fig.2) 

—two parcels managed primarily by the 

Bureau of Land Management (BLM) to 

the north of Grand Canyon (North and 

East Segregation Areas) and one parcel 

managed by the Forest Service on the 

Kaibab National Forest south of Grand 

Canyon (South Segregation Area).

At the Secretary’s request, the USGS 

began a series of short-term studies to provide (1) estimates of the uranium resource 

located on Federal lands proposed for 

withdrawal and those previously withdrawn 

from mineral mining, (2) an examination of 

surface contamination resulting from historical (1980s) mining, (3) analyses of surface 

water and groundwater to determine if 

previous mining has affected water quality, 

(4) compilation of the available information on exposure pathways and biological 

effects of uranium and associated contaminants for plants and animals, and (5) a 

geological map of the House Rock Valley 

area (East Segregation Area), Coconino 

County, Arizona, with detailed stratigraphic 

and structural information (published 

Figure 2.  Map of northwestern Arizona showing land ownership and the lands proposed for withdrawal from mining (the three Segregation Areas).
36%

12%

53%

Federal lands proposed for 

withdrawal on July 21, 2009

Federal lands withdrawn before 2009

(Grand Canyon National Park, national 

monuments, a game preserve, and Tribal lands)

Federal, State, and

private lands available

for mineral development 

separately). Results of those studies are 

presented in Alpine (2010), and items 1 to 4 

are summarized in this fact sheet.

Uranium Resource Availability

In 1990, the USGS estimated that 

northern Arizona breccia pipes contained 

a mean undiscovered uranium endowment of 1.3 million tons of uranium oxide 

(Finch and others, 1990). This estimate, 

which is an average of high (2.8 million 

tons) and low (339,000 tons) probability 

estimates, is about three times the total 

current uranium reserves in the rest of 

the United States (445,000 tons uranium 

oxide), as estimated in December 2003 

by the U.S. Energy Information Administration. In northern Arizona, the combined uranium production for mines in 

the North and South Segregation Areas 

through 1994 was 11,650 tons.

In 2009, the USGS examined how 

much of the northern Arizona uranium 

endowment was made unavailable for 

exploration, development, or mining by 

previous withdrawals of Federal land 

and by the proposed withdrawal (Alpine, 

2010, chapter A). Areas excluded from 

mining before July 2009—including 

the national park, two national monuments, a game preserve on forest lands, 

and Tribal lands—contain an estimated 

466,384 tons of uranium oxide, or about 

35 percent of the total uranium endowment estimated for northern Arizona. The 

2009 estimate for the North, South, and 

East Segregation Areas is 162,964 tons 

of uranium oxide, or about 12 percent of 

the total uranium endowment estimated 

for northern Arizona. Combined, these 

three parcels and previously withdrawn 

areas contain about 48 percent of the 

total estimated uranium endowment in 

northern Arizona (fig. 3). However, the 

1990 USGS report estimated that most 

of northern Arizona’s uranium resources 

occur in a “most favorable area”—the 

area defined by Finch and others (1990) 

as potentially most productive for 

uranium resource development—that 

includes all the lands already withdrawn 

or proposed for withdrawal. Those lands 

combined would represent 69 percent of 

the 910,000 tons of uranium oxide estimated to occur in that favorable area.

Effects of 1980s Uranium Mining

In August and October 2009, USGS 

scientists conducted field assessments in 

and around several reclaimed or inactive 

breccia-pipe uranium mines on BLM 

lands in the Kanab Creek area north of 

Grand Canyon National Park. Surface 

soil, sediment, and mined waste-rock 

samples were collected at six different sites that represent various stages of 

mining—mined and reclaimed, partially 

mined and on standby, and mineralized 

and explored by drilling but not mined—

and at an undisturbed area.

Samples taken at breccia-pipe mine 

sites were analyzed to determine historical dispersion of uranium and other trace 

elements by wind and water. Some samples were leached to simulate the potential mobility of uranium and other trace 

elements during weathering. Findings 

were compared to existing data for the 

region. For example, previous research 

indicated that naturally occurring levels 

of as much as 5.6 parts per million (ppm) 

uranium and 39 ppm arsenic can be present in undisturbed soil and sediment; the 

average soil uranium concentration in a 

regional survey was 2.4 ppm. Radioactivity surveys were also conducted in 2009 

to determine the levels of exposure to 

radioactivity at each site. 

Results of these studies included the 

following (Alpine, 2010, chapter B): (1) 

Uranium and arsenic were consistently the 

most abundant trace elements of concern 

at mined sites—the combined mean concentrations for the five mining sites evaluated were 9 ppm uranium and 18 ppm 

arsenic. The undisturbed area had uranium 

and arsenic values at or below the natural 

background. (2) Waste rock and ore at one 

mine in Hack Canyon have been washed 

downstream by flash floods during mining 

operations and again after reclamation. 

(3) Wind dispersion of uranium-rich 

dust was evident at three sites. Soil 

contamination was greatest adjacent 

to a mine on standby status, where ore 

and waste rock have been at the surface 

for about 20 years. (4) Experimental 

data indicated that uranium solubility 

increases with increased weathering and 

that leached trace-element concentrations 

derived from waste rock or ore can be 

very high. However, the dilution factors 

during flood events are also very high. 

(5) Finally, there was evidence of 

elevated but highly variable radioactivity 

at all mine sites.

Water Chemistry of Wells, 

Perennial and Intermittent 

Streams, and Springs

To understand how water quality may 

be affected by uranium mining activities, 

USGS scientists evaluated both historical water-chemistry data and analyses of 

groundwater samples collected in 2009 

(Alpine, 2010, chapter C). Historical 

data for 1,014 samples from 428 sites 

in the Grand Canyon region, including 

wells, streams, and springs, indicated 

that 95 percent of samples had concentrations of dissolved uranium less than 

30 micrograms per liter (μg/L), the U.S. 

Environmental Protection Agency (EPA) 

maximum contaminant level for drinking water. Sixty-six percent of samples 

contained dissolved uranium concentrations of 5 μg/L or less and were classified as low concentrations for the Grand 

Canyon region on the basis of historical 

data. Samples of surface water from the 

Colorado River in the Grand Canyon 

region typically contained less than 5 μg/L 

dissolved uranium. However, about 70 of 

the 428 sites exceeded the EPA’s primary 

and secondary maximum contaminant 

levels for drinking water for a few major 

Figure 3.  Pie diagram showing percentages of the total estimated mean uranium deposit in

northern Arizona for lands proposed for withdrawal from new mining on July 21, 2009, for lands

withdrawn from mining before July 21, 2009, and for lands available for new mineral development.
ions and trace elements, such as arsenic, 

iron, lead, and sulfate. 

Historical samples from about 120 

springs and 32 streams in the region 

showed dissolved uranium concentrations 

greater than 5 μg/L but less than 30 μg/L; 

those concentrations are thought to be the 

result of natural dissolution and erosion 

of mineralized ore deposits. Samples 

from 15 springs and 5 wells in the region 

contained dissolved uranium concentrations greater than the 30-μg/L limit. These 

sites are close by or in direct contact with 

mineralized ore bodies, and the elevated 

concentrations may be related to natural 

processes, mining, or both.

In August and September 2009, 

groundwater samples were collected from 

24 sites (springs and wells; fig. 4) in the 

study area to supplement the historical 

dataset and evaluate the impacts of legacy 

mining. Analysis of this limited dataset 

showed that concentrations of dissolved 

uranium and arsenic were not significantly 

different between mined and unmined 

areas. Dissolved uranium concentrations in samples collected from wells and 

springs that discharge from perched waterbearing zones were higher than 5 μg/L but 

still below the EPA limit.

Biological Pathways of Exposure 

for Uranium and Associated 

Radioactive Contaminants

Various species of plants and animals 

found on the lands proposed for withdrawal 

are considered species of concern by State 

and Federal agencies. Previous studies 

have reported that uranium and associated 

radioactive contaminants, or radionuclides, 

can affect the survival, growth, and reproduction of plants and animals. Exposure to 

chemical and radiation hazards is influenced by life history and surrounding environment. For example, the use of burrows 

in uranium-rich areas by some species of 

reptiles, amphibians, birds, and mammals is 

of particular concern.

USGS scientists examined known 

chemical and radiation hazards associated with uranium and developed possible 

exposure pathways and a food web that is 

specific to the lands considered for withdrawal (Alpine, 2010, chapter D). Overall, 

USGS scientists found only limited chemical toxicity data available for plants and 

animals of concern. In addition, measured 

tissue concentrations of uranium and other 

radionuclides were available for only two 

species of concern in the Grand Canyon 

region. This lack of information makes it 

difficult to conduct a meaningful ecological 

risk assessment without further research. 

In the absence of such data, understanding 

the pathways by which plants and animals 

may be exposed to uranium and associated 

contaminants is critical to minimizing risk.

Future Research

The results of these short-term studies 

by the USGS underscore data and information gaps that make it difficult for resource 

managers and decisionmakers to fully 

evaluate uranium mining impacts in northern Arizona. For example, detailed data 

on uranium isotope geochemistry could be 

used to help differentiate between natural 

and mining-derived sources of uranium. 

Similarly, chemical data for the sediment 

of the Colorado River and its tributaries 

could provide information about the source 

and mobility of uranium and other associated metals. Additional wells distributed 

throughout the region would help improve 

the understanding of groundwater movement and potential risks to the region’s 

water from uranium mining. Information 

on the sensitivity of the region’s plants and 

animals to uranium and on present uranium 

concentration in their tissues is essential for 

evaluating the risks to species of concern.

The USGS continues to assist the 

BLM with the environmental impact 

statement process to assess the proposed 

withdrawal. USGS scientists will be evaluating additional sources of data, collecting 

and evaluating additional water samples 

to determine if high concentrations of dissolved uranium detected in the historical 

record persist, and establishing monitoring 

sites to evaluate past, current, and future 

mining impacts. 

Donald J. Bills, Kristin M. Brown,

Andrea E. Alpine, James K. Otton,

Bradley S. Van Gosen, Jo Ellen Hinck,

and Fred D Tillman

References Cited

Alpine, Andrea E., ed., 2010, Hydrological, 

geological, and biological site characterization 

of breccia pipe uranium deposits in northern 

Arizona: U.S. Geological Survey Scientific 

Investigations Report 2010–5025, 353 p., 1 pl., 

scale 1:375,000.

Finch, W.I., Sutphin, H.B., Pierson, C.T., McCammon, R.B., and Wenrich, K.J., 1990, The 1987 

estimate of undiscovered uranium endowment 

in solution-collapse breccia pipes in the Grand 

Canyon region of northern Arizona and adjacent Utah: U.S. Geological Survey Circular 

1051, 19 p.

For more information contact:

John Hoffmann

U.S. Geological Survey

Arizona Water Science Center

520 N. Park Ave., Suite 221

Tucson, AZ, 85719

520-670-6671 (ext. 222)

This Fact Sheet and any updates to it are available

online at http://pubs.usgs.gov/fs/2010/3050/

Figure 4.  USGS scientists taking a water sample at Buck Farm Spring, which was 1 of 20 springs

sampled as part of new research to investigate possible impacts of uranium mining in northern

Arizona. Sites selected for sampling were designed to fill gaps in historical water-chemistry data in

the region. (USGS photo by Nancy Hornewer.)