Breccia-Pipe Uranium Mining in Northern Arizona—Estimate of Resources and Assessment of Historical Effects

Breccia-Pipe Uranium Mining in Northern Arizona— Estimate of Resources and Assessment of Historical Effects

bout 1 million acres of Federal Aland in the Grand Canyon region of Arizona were temporarily withdrawn from new mining claims in July 2009 by the Secretary of the Interior because of concern that increased uranium mining could have negative impacts on the land,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 Figure 1. The Kanab North Mine is one of several breccia-pipe uranium mines in northern Arizona. the possible land withdrawal, examine USGS scientists conducted field assessments at this mine, where operations are currently on the effects of previous breccia-pipe standby (USGS photo by Don Bills). mining, summarize water-chemistry data for streams and springs, and investigate findings will be used in an environmental exposed to the atmosphere, either naturally potential biological pathways of expo- assessment process to examine the poten- through erosion or by mining, these miner- sure to uranium and associated contami- tial effects of future mining activities. This als may be dissolved or broken down and nants. This fact sheet summarizes results fact sheet summarizes USGS research dispersed by wind and water. completed through December 2009 and Uranium mining in the Grand Can- through December 2009 and outlines presented in USGS Scientific Investiga- yon region peaked in the 1980s. However, further research needs. tions Report 2010-5025 (Alpine, 2010; there is now renewed interest in the explo- http://pubs.usgs.gov/sir/2010/5025/). ration and mining of breccia pipes in the Introduction region—uranium prices have increased, Background and concerns about clean energy and Citing concerns that uranium min- energy independence also have focused ing could have adverse effects on the Some of the highest grade uranium attention on uranium and nuclear energy. Grand Canyon watershed, its people, and ore in the United States occurs in breccia Currently, there are 104 U.S. nuclear wildlife, on July 21, 2009, Secretary of pipes scattered across the Grand Canyon reactors, which annually consume about the Interior Ken Salazar withdrew about 1 region (fig.1). These breccia pipes, named 27,500 tons of uranium oxide, the primary million acres of Federal land near Grand for their vertical, pipe-like shape and the constituent of the fuel rods that power Canyon from new mining claims for 2 broken rock, or breccia, that fills them, them. Each year, about 1,750 to 2,250 years. Mining of uranium can release range from 300 to 500 ft in diameter at tons of uranium oxide are mined domesti- toxic and hazardous substances to the depth. They were formed millions of years cally. The remainder of the uranium oxide environment. These include uranium ago when groundwater dissolved carbon- needed to fuel U.S. reactors comes from itself, which is a toxic chemical and can ate rock and created vertical cavities into foreign sources, primarily Canada, and the pose a radiation hazard, and arsenic and which surrounding rock collapsed. Later, U.S. utility inventory. other toxic trace metals. At the Secre- highly mineralized groundwater from Increased mining in northern Ari- tary’s request, the U.S. Geological Survey overlying or underlying rocks, mov- zona could help meet the U.S. demand for (USGS) conducted a series of short-term ing vertically through the porous brec- uranium but could also increase the amount studies to examine the effect of breccia- cia, deposited ore minerals—including of uranium and other trace elements in pipe uranium mining in the region. USGS uranium—in some of the pipes. When the local surface water and groundwater

U.S. Department of the Interior USGS Fact Sheet 2010–3050 U.S. Geological Survey January 2011 flowing into Grand Canyon National Park land near Grand Canyon from new mining withdrawal and those previously withdrawn and the Colorado River. Deep mining claims for 2 years. The land proposed for from mineral mining, (2) an examination of activities could allow uranium and other withdrawal comprises three parcels (fig.2) surface contamination resulting from histor- trace elements to be mobilized by water —two parcels managed primarily by the ical (1980s) mining, (3) analyses of surface and transported into perched water-bearing Bureau of Land Management (BLM) to water and groundwater to determine if zones and the regional aquifer, which are the north of Grand Canyon (North and previous mining has affected water quality, sources of water for local communities and East Segregation Areas) and one parcel (4) compilation of the available informa- feed springs used by recreationists, fish, managed by the Forest Service on the tion on exposure pathways and biological and other wildlife. Additionally, waste rock, Kaibab National Forest south of Grand effects of uranium and associated con- ore, and dust from mined areas, if not prop- Canyon (South Segregation Area). taminants for plants and animals, and (5) a erly managed, could be transported away At the Secretary’s request, the USGS geological map of the House Rock Valley from the mines by wind and flood events. began a series of short-term studies to pro- area (East Segregation Area), Coconino The Secretary of the Interior cited vide (1) estimates of the uranium resource County, Arizona, with detailed stratigraphic such concerns when he withdrew Federal located on Federal lands proposed for and structural information (published

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NORTH Jacob Kanab Creek Lake SEGREGATION EAST AREA SEGREGATION KAIBAB NATIONAL FOREST AREA Hack Canyon 36°30'

NAVAJO GRAND CANYON NATIONAL PARK RESERVATION GRAND CANYON - PARASHANT NATIONAL MONUMENT Havasu Creek LAKE Colorado River MEAD LAKE MEAD North Rim NRA NRA Supai Village HAVASUPAI L Creek i RESERVATION Bright Angel t tl

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Peach Springs 35°30' Data provided by U.S. Geological Survey and 0 25 50 MILES Bureau of Land Management. Map created on 11/10/09 by K.M. Brown Map revised on 5/24/10 by T. Arundel 0 25 50 KILOMETERS

NEVADA UTAH EXPLANATION COLORADO

U.S. Bureau of Land Management National Park Service

Flagstaff U.S. Forest Service State land CALIFORNIA ARIZONA NEW MEXICO Tribal land Private land Phoenix

Segregation area—Boundary Index map National Monument—Boundary

Figure 2. Map of northwestern Arizona showing land ownership and the lands proposed for withdrawal from mining (the three Segregation Areas). separately). Results of those studies are Federal lands proposed for presented in Alpine (2010), and items 1 to 4 withdrawal on July 21, 2009 are summarized in this fact sheet. 12% Uranium Resource Availability Federal lands withdrawn before 2009 In 1990, the USGS estimated that 36% (Grand Canyon National Park, national northern Arizona breccia pipes contained 53% monuments, a game preserve, and Tribal lands) a mean undiscovered uranium endow- Federal, State, and private lands available ment of 1.3 million tons of uranium oxide for mineral development (Finch and others, 1990). This estimate, which is an average of high (2.8 million Figure 3. Pie diagram showing percentages of the total estimated mean uranium deposit in tons) and low (339,000 tons) probability northern Arizona for lands proposed for withdrawal from new mining on July 21, 2009, for lands estimates, is about three times the total withdrawn from mining before July 21, 2009, and for lands available for new mineral development. current uranium reserves in the rest of the United States (445,000 tons uranium oxide), as estimated in December 2003 and around several reclaimed or inactive contamination was greatest adjacent by the U.S. Energy Information Adminis- breccia-pipe uranium mines on BLM to a mine on standby status, where ore tration. In northern Arizona, the com- lands in the Kanab Creek area north of and waste rock have been at the surface bined uranium production for mines in Grand Canyon National Park. Surface for about 20 years. (4) Experimental the North and South Segregation Areas soil, sediment, and mined waste-rock data indicated that uranium solubility through 1994 was 11,650 tons. samples were collected at six differ- increases with increased weathering and In 2009, the USGS examined how ent sites that represent various stages of that leached trace-element concentrations much of the northern Arizona uranium mining—mined and reclaimed, partially derived from waste rock or ore can be endowment was made unavailable for mined and on standby, and mineralized very high. However, the dilution factors exploration, development, or mining by and explored by drilling but not mined— during flood events are also very high. previous withdrawals of Federal land and at an undisturbed area. (5) Finally, there was evidence of and by the proposed withdrawal (Alpine, Samples taken at breccia-pipe mine elevated but highly variable radioactivity 2010, chapter A). Areas excluded from sites were analyzed to determine histori- at all mine sites. mining before July 2009—including cal dispersion of uranium and other trace the national park, two national monu- elements by wind and water. Some sam- Water Chemistry of Wells, ments, a game preserve on forest lands, ples were leached to simulate the poten- and Tribal lands—contain an estimated tial mobility of uranium and other trace Perennial and Intermittent 466,384 tons of uranium oxide, or about elements during weathering. Findings Streams, and Springs 35 percent of the total uranium endow- were compared to existing data for the To understand how water quality may ment estimated for northern Arizona. The region. For example, previous research 2009 estimate for the North, South, and be affected by uranium mining activities, indicated that naturally occurring levels USGS scientists evaluated both histori- East Segregation Areas is 162,964 tons of as much as 5.6 parts per million (ppm) of uranium oxide, or about 12 percent of cal water-chemistry data and analyses of uranium and 39 ppm arsenic can be pres- groundwater samples collected in 2009 the total uranium endowment estimated ent in undisturbed soil and sediment; the for northern Arizona. Combined, these (Alpine, 2010, chapter C). Historical average soil uranium concentration in a three parcels and previously withdrawn data for 1,014 samples from 428 sites regional survey was 2.4 ppm. Radioactiv- areas contain about 48 percent of the in the Grand Canyon region, including ity surveys were also conducted in 2009 total estimated uranium endowment in wells, streams, and springs, indicated to determine the levels of exposure to northern Arizona (fig. 3). However, the that 95 percent of samples had concen- radioactivity at each site. 1990 USGS report estimated that most trations of dissolved uranium less than Results of these studies included the of northern Arizona’s uranium resources 30 micrograms per liter (µg/L), the U.S. following (Alpine, 2010, chapter B): (1) occur in a “most favorable area”—the Environmental Protection Agency (EPA) Uranium and arsenic were consistently the area defined by Finch and others (1990) maximum contaminant level for drink- most abundant trace elements of concern as potentially most productive for ing water. Sixty-six percent of samples at mined sites—the combined mean con- uranium resource development—that contained dissolved uranium concentra- includes all the lands already withdrawn centrations for the five mining sites evalu- tions of 5 µg/L or less and were classi- or proposed for withdrawal. Those lands ated were 9 ppm uranium and 18 ppm fied as low concentrations for the Grand combined would represent 69 percent of arsenic. The undisturbed area had uranium Canyon region on the basis of historical the 910,000 tons of uranium oxide esti- and arsenic values at or below the natural data. Samples of surface water from the mated to occur in that favorable area. background. (2) Waste rock and ore at one Colorado River in the Grand Canyon mine in Hack Canyon have been washed region typically contained less than 5 µg/L downstream by flash floods during mining dissolved uranium. However, about 70 of Effects of 1980s Uranium Mining operations and again after reclamation. the 428 sites exceeded the EPA’s primary In August and October 2009, USGS (3) Wind dispersion of uranium-rich and secondary maximum contaminant scientists conducted field assessments in dust was evident at three sites. Soil levels for drinking water for a few major 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 move- ment 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 Figure 4. USGS scientists taking a water sample at Buck Farm Spring, which was 1 of 20 springs evaluating the risks to species of concern. sampled as part of new research to investigate possible impacts of uranium mining in northern The USGS continues to assist the Arizona. Sites selected for sampling were designed to fill gaps in historical water-chemistry data in BLM with the environmental impact the region. (USGS photo by Nancy Hornewer.) statement process to assess the proposed withdrawal. USGS scientists will be evalu- ions and trace elements, such as arsenic, are considered species of concern by State ating additional sources of data, collecting iron, lead, and sulfate. and Federal agencies. Previous studies and evaluating additional water samples Historical samples from about 120 have reported that uranium and associated to determine if high concentrations of dis- springs and 32 streams in the region radioactive contaminants, or radionuclides, solved uranium detected in the historical showed dissolved uranium concentrations can affect the survival, growth, and repro- record persist, and establishing monitoring greater than 5 µg/L but less than 30 µg/L; duction of plants and animals. Exposure to sites to evaluate past, current, and future those concentrations are thought to be the chemical and radiation hazards is influ- mining impacts. result of natural dissolution and erosion enced by life history and surrounding envi- of mineralized ore deposits. Samples ronment. For example, the use of burrows Donald J. Bills, Kristin M. Brown, from 15 springs and 5 wells in the region in uranium-rich areas by some species of Andrea E. Alpine, James K. Otton, contained dissolved uranium concentra- reptiles, amphibians, birds, and mammals is Bradley S. Van Gosen, Jo Ellen Hinck, tions greater than the 30-µg/L limit. These of particular concern. and Fred D Tillman sites are close by or in direct contact with USGS scientists examined known mineralized ore bodies, and the elevated chemical and radiation hazards associ- concentrations may be related to natural ated with uranium and developed possible References Cited processes, mining, or both. exposure pathways and a food web that is In August and September 2009, specific to the lands considered for with- Alpine, Andrea E., ed., 2010, Hydrological, groundwater samples were collected from geological, and biological site characterization drawal (Alpine, 2010, chapter D). Overall, of breccia pipe uranium deposits in northern 24 sites (springs and wells; fig. 4) in the USGS scientists found only limited chemi- Arizona: U.S. Geological Survey Scientific study area to supplement the historical cal toxicity data available for plants and Investigations Report 2010–5025, 353 p., 1 pl., dataset and evaluate the impacts of legacy animals of concern. In addition, measured scale 1:375,000. mining. Analysis of this limited dataset tissue concentrations of uranium and other Finch, W.I., Sutphin, H.B., Pierson, C.T., McCam- showed that concentrations of dissolved radionuclides were available for only two mon, R.B., and Wenrich, K.J., 1990, The 1987 uranium and arsenic were not significantly species of concern in the Grand Canyon estimate of undiscovered uranium endowment different between mined and unmined region. This lack of information makes it in solution-collapse breccia pipes in the Grand areas. Dissolved uranium concentra- difficult to conduct a meaningful ecological Canyon region of northern Arizona and adja- tions in samples collected from wells and risk assessment without further research. cent Utah: U.S. Geological Survey Circular 1051, 19 p. springs that discharge from perched water- In the absence of such data, understanding bearing zones were higher than 5 µg/L but the pathways by which plants and animals For more information contact: still below the EPA limit. may be exposed to uranium and associated John Hoffmann contaminants is critical to minimizing risk. U.S. Geological Survey Biological Pathways of Exposure Arizona Water Science Center Future Research 520 N. Park Ave., Suite 221 for Uranium and Associated Tucson, AZ, 85719 The results of these short-term studies 520-670-6671 (ext. 222) Radioactive Contaminants by the USGS underscore data and informa- Various species of plants and animals This Fact Sheet and any updates to it are available tion gaps that make it difficult for resource online at http://pubs.usgs.gov/fs/2010/3050/ found on the lands proposed for withdrawal managers and decisionmakers to fully