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Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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6

Potential Environmental Effects of
Uranium Mining, Processing, and
Reclamation

Key Points

• Uranium mining, processing, and reclamation in Virginia have the potential to affect surface water quality and quantity groundwater quality and quantity, soils, air quality, and biota. The impacts of these activities in Virginia would depend on site-specific conditions, the rigor of the monitoring program established to provide early warning of contaminant migration, and the efforts to mitigate and control potential impacts. If uranium mining, processing, and reclamation are designed, constructed, operated, and monitored according to modern international best practices, near- to moderate-term environmental effects specific to uranium mining and processing should be substantially reduced.

• Tailings disposal sites represent significant potential sources of contamination for thousands of years, and the long-term risks remain poorly defined. Although significant improvements have been made in recent years to tailings management practices to isolate mine waste from the environment, limited data exist to confirm the long-term effectiveness of uranium tailings management facilities that have been designed and constructed accord ing to modern best practices.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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• Significant potential environmental risks are associated with extreme natural events and failures in management practices. Extreme natural events (e.g., hurricanes, earthquakes, intense rainfall events, drought) have the potential to lead to the release of contaminants if facilities are not designed and constructed to withstand such events, or fail to perform as designed.

• Models and comprehensive site characterization are important for estimating the potential environmental effects associated with a specific uranium mine and processing facility. A thorough site characterization, supplemented by air quality and hydrologi-cal modeling, is essential for estimating the potential environmental impacts of uranium mining and processing under site-specific conditions and mitigation practices.

This chapter presents a discussion of impacts of uranium mining and processing operations on air quality, soil, surface water and groundwater, and biota. Much is already known about the environmental impacts of mining, both on-site and off-site, and that body of information provides a basis for this chapter. However, the primary emphasis of the chapter is on the unique impacts caused by uranium mining, processing, and waste management. The committee sought out data from currently operating uranium mining sites, where available, although detailed publicly available environmental effects analyses were limited. As discussed in Chapter 4, the operating practices used in uranium mining and processing have evolved over recent decades, and by definition, there are no retrospective examinations of the environmental impacts of the most current practices. For this reason, this chapter provides a review of the accumulated evidence from prior studies of mining and processing at comparable sites around the world—especially data from several relatively recent decommissionings of uranium mines and processing facilities in Canada. The chapter includes analyses of impacts on surface water, groundwater, soil, and air and the ecological effects of these impacts.

ENVIRONMENTAL EXPOSURE PATHWAYS

Exposure pathways refer to the specific ways in which animals, plants, and people come in contact with environmental agents. In the case of uranium mining, processing, reclamation, and waste handling, exposure pathways to living organisms, including people, may exist for chemical and radiological materials via inhalation, ingestion, absorption through the skin, and gamma radiation

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

exposure. Gamma radiation is different from chemical contaminants because it can travel beyond the source, and direct contact is not necessary for exposure to occur. These pathways may be direct, as when someone breathes air that contains radon gas or dust, or may be indirect, as when a worm absorbs a chemical from the soil and the worm is eaten by another animal, which may eventually be eaten by other animals, including people. Exposures occur by eating, drinking, breathing, skin contact, or from gamma-ray emissions from radionuclides. Gamma rays can travel much farther than alpha or beta particles, and can penetrate the body, potentially exposing all of the organs. Radiation can easily penetrate solid materials such as soils or drums.

The exposure pathways are the same for people and for ecological resources, but different pathways are dominant. The exposures of greatest importance from the human health perspective are occupational exposures that occur within mines and enclosed processing facilities, primarily involving inhalation (see Chapter 5). Human health exposures may also occur in the surrounding communities if contamination travels offsite via air, surface water, or groundwater. Exposures of greatest importance for ecological effects occur outside the enclosed facilities, where radon and gaseous chemicals would quickly dissipate. The most significant exposure pathways for ecological resources are anticipated to occur via surface water because of its accessibility and the numerous potential transport mechanisms for dissolved and particle-associated contaminants (e.g., discharge of treated process water into streams; discharge of contaminated groundwater to streams). Such waters may contain chemicals, metals, and radionuclides higher than background or preconstruction conditions, particularly if treatment or waste containment systems fail to perform as designed. However, ecological exposures also may occur through air (e.g., dust, radon), contaminated soil, sediments, or from gamma radiation given off by radionuclides in contaminated materials.

SURFACE WATER EFFECTS

For purposes of description here, it is convenient to address surface water and groundwater as if they are separate entities, although the committee recognizes that surface water and groundwater are part of a single resource. Water moves between surface water and groundwater, and changes in the quantity and quality of one will affect the same parameters in the other.

Disturbances of the land surface associated with uranium mining in Virginia would be expected to have significant effects on both on-site and downstream surface water conditions. These disturbances affect both surface water quantity and quality. Many of these effects are similar to those encountered in other types of mining, although there are some unique risks posed by uranium mining and processing due to the presence of radioactive substances, and co-occurring chemicals such as heavy metals.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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Impacts on Surface Water Quality

The disturbance of the land surface by mining, the temporary storage of ores and mining and processing wastes on-site, dewatering of mine workings/pits, and a variety of reclamation activities all have the potential to significantly affect the concentrations and loads of dissolved and suspended materials in surface water off-site. For purposes of this report, the materials of concern include some nonradioactive substances (especially dissolved heavy metals and metalloids), as well as naturally occurring radioactive materials (NORM), technologically enhanced naturally occurring radioactive materials (TENORM), and both solid and liquid tailings from processing operations. Considering Virginia’s relatively wet climate, surface water would provide a principal vector for the off-site transport of contaminants.

Mining and Processing Effects

Acid mine drainage. Acid mine drainage (AMD) has the potential to be one of the most serious environmental problems caused by uranium mining in the Commonwealth of Virginia if it is not appropriately managed and mitigated. AMD is formed through oxidation of metal sulfides (e.g., FeS2) present in the ore or waste materials by a group of acidophilic microorganisms (Campos et al., 2011). Because these bacteria thrive only under acidic conditions, the production of acidity can accelerate and become self-sustaining as long as sulfides and oxygen are available (Drever, 1982). Acidic mine water is more likely to contain heavy metals (e.g., iron, manganese, aluminum, copper, chromium, zinc, lead, vanadium, cobalt, or nickel) or metalloids (e.g., selenium or arsenic) released into solution by oxidation of the sulfide minerals, in addition to radionuclides in the uranium-238 (238U) decay series (i.e., uranium, radium, radon, and thorium). Therefore, the presence of sulfide minerals in the uranium ore is a preexisting condition that promotes the release of radionuclides and toxic heavy metals from uranium mines to the environment. Analyses of the Coles Hill uranium deposit suggest that it is relatively low in sulfide minerals (0.04-0.05 percent; Marline Uranium Corporation, 1983), although other deposits in Virginia may contain higher amounts of sulfide.

Problems with AMD are nearly ubiquitous in the literature for uranium mines around the world, including sites in Australia (Mudd and Patterson, 2010), Germany (Biehler and Falck, 1999), Ontario, Canada (Berthelot et al., 1999), Saskatchewan, Canada (Waite et al., 1988), Portugal (Neves and Matias, 2008), and Brazil (Campos et al., 2011), as well as for virtually all types of mining (e.g., underground mining of high-sulfur coal deposits). It should be emphasized, however, that many of the documented problems with AMD are attributable to mines that operated at a time when environmental impacts were not an important consideration, and mitigation techniques were not widely employed. Yet, some of these sites serve as important examples of the significant surface water impacts

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

that can be caused by uranium mining and processing and of the efficacy of modern mitigation techniques that have been employed for the purpose of rehabilitating AMD-producing sites. In the following sections, several case studies of AMD mitigation from uranium mining operations at comparable sites around the world are examined.

The Rum Jungle uranium and copper mining project in Northern Territory, Australia, operated from 1954 to 1971, is an example of a mining operation that occurred with virtually no concern for environmental impacts. During early years of operation, mine tailings at this site were discharged onto a flat, low-lying area adjacent to the processing facility; about 0.26 million gallons per day (1 million L/day) of liquid tailings wastes were discharged to a nearby river, and the solid tailings proved highly erodible during wet-season rain events. A rehabilitation program from 1982 to 1986 aimed at reducing metal loads to surface waters included backfilling open cuts with tailing wastes, recontouring waste rock dumps, constructing engineered soil covers to limit infiltration and AMD production, and rehabilitating the former processing facility and ore stockpile areas. More than two decades following closure, a field campaign in the 1992-1993 wet season showed that concentrations of arsenic, chromium, copper, nickel, lead, uranium, and zinc still greatly exceeded water quality standards at a river monitoring station located 3.5 mi (5.6 km) downstream of the site. An important conclusion drawn from the field study is that despite extensive remediation efforts, AMD production and leaching of metals from waste rock dumps are a continuing cause of water pollution at this site, which has been attributed, at least in part, to a gradual increase in infiltration of water through dried and cracked clay soil covers over the waste rock dumps and subsequent AMD generation (Mudd and Patterson, 2010).

Mitigation of surface water quality effects from another early uranium mining operation that was active during the same period (1955-1996), at Elliot Lake in Ontario, Canada, had somewhat greater success while providing some important lessons for future uranium mining operations. As in the case of Rum Jungle, the relatively high mineral sulfide content of the ore and tailings at Elliot Lake provide a substrate for AMD production. During early mining operations, sulfide-containing tailings were dumped in a waste management area with no additional treatment. The tailings leachate with low pH and elevated metal and radionuclide concentrations led to declines in fish populations downstream (Clulow et al., 1998). Later, mine operators began using greater quantities of (1) lime to neutralize the acidity of the tailings and (2) barium chloride to precipitate the dissolved radium prior to wastewater discharge. Additionally, decommissioning of the Quirke mine at Elliot Lake in the 1990s employed a large-scale water cover (minimum depth of 0.6 m) over the waste management area to control the rate of sulfide oxidation and AMD formation, and site discharge was subsequently able to meet both Canadian and Ontario mine effluent guidelines. Although the mitigation activities have been deemed successful, one troubling result from a

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

long-term study of surface water contamination at the site is an increase in radium concentrations, which Peacey et al. (2002) attributed to barium-radium-sulfate dissolution. The regulatory authorities most familiar with this site have concluded that the decommissioned Elliot Lake uranium mine tailings “present a perpetual environmental hazard” making it necessary to keep the waste management area flooded and the water impoundment physically secure in perpetuity to prevent exposure of the tailings to oxygen, production of AMD, solubilization of thorium and radium, and release of dissolved radionuclides and various heavy metals to the downstream environment (CEAA, 1996).

Similar experiences occurred in the Athabasca region of Saskatchewan, Canada, associated with mining of the Gunnar uranium deposit in the vicinity of Langley Bay from 1955 to 1964. At this location, tailings were deposited into a small lake adjacent to Langley Bay, but a tailings dam failure in 1960 allowed the tailings to move into Langley Bay—a shallow body of water adjacent to Lake Athabasca—where they formed a deltaic deposit bisecting the bay. Some sampling locations in Langley Bay have consistently exceeded Saskatchewan water quality standards for 226Ra, and further sampling has shown that the primary source of the contamination of the bay is from the periodic release of AMD from the tailings during snowmelt and rainstorm events. The sampling station closest to the tailings exhibited very high concentrations of both uranium and sulfate—consistent with this explanation (Waite et al., 1989).

Campos et al. (2011) has also reported low pH and high dissolved uranium and toxic metals concentrations in mine waters at the Caldas site, Minas Gerais state, Brazil (a pit mine operated from 1982 to 1995). Approximately 2 percent of the 95 million tons of rock removed from the pit were subjected to processing, with the remainder placed in two waste rock piles. In contrast to Rum Jungle, the Caldas mine utilized modern tailings and wastewater treatment facilities to collect and treat AMD from the waste rock piles as well as the acidic tailings; liquid and solid tailings were neutralized to pH 9 using calcium carbonate (CaCO3) and lime (CaO) before being discharged to the tailings facility for solid deposition. Campos et al. (2011) and previous investigators identified the principal source of acid drainage at this site as the mine-waste rock piles, not from the tailings management facility. Campos et al. (2011) reported that following decommissioning, average concentrations of manganese, fluoride, uranium, zinc, and sulfate at several monitoring stations exceeded surface water quality standards. Thus, the authors further concluded that long-term use of the river waters downstream of the site that receive Caldas mine effluent needs to be very carefully evaluated.

Experiences from more recent mining projects demonstrate further improvements in the ability to mitigate surface water contamination from AMD. A decommissioning study of Cluff Lake in Saskatchewan, Canada, documents improved outcomes for a relatively modern uranium mining operation (1980-2002) but also reveals some continued environmental problems attributable, at least in part, to AMD (Box 6.1).

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

Newer mitigation strategies are perhaps best exemplified by tailings management at McClean Lake, Canada. Hydrological interactions between tailings liquid in the JEB tailings disposal pit and the surrounding groundwater system are minimized through the use of tailings compaction and a system of French drains to control groundwater head gradients. AMD formation in the Claude pit is minimized by disposal of AMD rock on a lined pad before it is returned to the flooded pit for disposal. AREVA Resources Canada, Inc. have suggested that the state-of-the-art McClean Lake tailings management facility has been able to maintain groundwater concentrations of dissolved nickel, uranium, arsenic, and radium-226 below regulatory limits.

Depending on their sulfide content, the disposal of mine spoils needs to be handled carefully to control or avoid AMD because the exposure of these materials to oxygen tends to promote acid-generating processes. During active tailings management, oxygen entry can be limited by maintenance of a water cover (Figure 6.2) over the tailings area. Also, liquid tailings and other wastewaters can be treated using lime and barium chloride to neutralize acidity, precipitate radium, and control dissolved metal and uranium concentrations prior to release to the environment. During the decommissioning phase, soil infiltration can be reduced using engineered soil cover materials of low permeability (e.g., clays) that can be riprapped and vegetated to provide protection against physical erosion. However, there are no data that document the long-term performance of these mitigation features.

If surface or underground uranium mining were conducted in Virginia, the extent of surface water contamination, including releases of both radionuclides and toxic metals, would depend on the mineral composition of the ore, the miti-gative steps taken to minimize impacts to downstream receiving waters, and the long-term performance of those mitigative strategies under a variety of climatic conditions. Although the Coles Hill deposit has been reported to be relatively low in sulfide minerals, this may not be the case for all uranium ore deposits in Virginia.

Dewatering effects. To enable a mine to be worked, groundwater needs to be prevented from entering the mine or removed in a process known as dewatering. Groundwater entering the mine can be pumped out and discharged at the surface, or the local water table can be lowered using a number of extraction wells surrounding the mine to prevent water from entering. Mine dewatering activities have the potential to affect surface water quality, particularly if the discharge is not treated. Groundwater will naturally have a composition that reflects the mineralogy of the host rock and depends on many factors. As one example, uranium and 226Ra concentrations in dewatering water from Cameco’s Key Lake operation have ranged from 3 to 314 µg/L and 0.012 to 0.19 Bq/L, respectively, whereas at the McLean Lake mine the concentrations of these constituents have ranged

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

BOX 6.1
Cluff Lake Decommissioning Project

Perhaps the best available data on the environmental effects resulting from a modern uranium mine and processing facility are associated with the former Cluff Lake mine and processing facility, located in the Athabasca Basin of northern Saskatchewan, Canada, that treated high-grade ores ranging from 1 to 30 percent U3O8. Unlike most of the other mining operations that have been discussed in this section, uranium mining and processing at Cluff Lake didn’t begin until the 1980s—an era in which environmental concerns were significantly enhanced and regulations were more stringent than in earlier periods. Two pits at Cluff Lake (“D” and “Claude”) were mined first, followed by an underground mine (“OP/DP”), followed by three other pits (“DJN,” “DJX,” and “DJ”). All mining and processing at Cluff Lake ceased in 2002 after 22 years of operations, and with 62 million pounds of U3O8 produced. In addition to the mill, operational facilities at Cluff Lake also included a tailings management area with a two-stage liquid effluent treatment system and surface water diversion ditches, a residential camp area, and various other site infrastructure. Although tailings management and water treatment strategies have improved since the 1980s, the environmental assessment performed as part of the Cluff Lake decommissioning project provides a glimpse of what could occur if a modern uranium mining and processing operation were sited in Virginia.

A Canadian Nuclear Safety Commission (CNSC) environmental assessment to guide the decommissioning work was completed in 2003 (CNSC, 2003), and actual decommissioning was initiated in 2004. CNSC (2003) concluded that the primary environmental effects on completion of the decommissioning would be the migration of contaminants from existing sources (e.g., tailings and waste rock piles) to both groundwater and surface water. Most surface waters in the vicinity of the former mine/mill complex received no direct discharge and therefore were negligibly or only slightly affected by previous operations. Island Lake, however, was adversely affected because of its location immediately downstream of the mill effluent treatment systems. Measured mean annual concentrations of total dissolved solids, sulfate, chloride, uranium, and molybdenum in Island Lake in 2002 were two or three orders of magnitude higher than during the baseline (i.e., premining) monitoring period.

Acid mine drainage (AMD) from the Claude waste rock pile caused contamination of the Claude pit, resulting in greatly elevated levels of sulfate, total dissolved solids, uranium, nickel, arsenic, and radium-226. The relatively poor water quality of the Claude pit necessitated pumping water from the pit to maintain a water level below that of the adjacent lake to prevent transport of contaminants off-site. Groundwater has been similarly affected by AMD from the Claude waste rock, which has formed a shallow, acidic (pH < 4) groundwater plume with elevated levels of dissolved nickel (>10 mg/L) and uranium (>100 mg/L) migrating away from the waste rock pile.

Additional potential environmental hazards at the Cluff Lake site include the flooded mine workings and the tailings management area (Figure 6.1). The

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

image

FIGURE 6.1 Tailings management area at Cluff Lake in 1999, Saskatchewan, Canada. The tailings are held behind an earthen dam. SOURCE: AREVA Resources Canada, Inc.

from 0.5 to 9.9 µg/L and 0.01 to 0.05 Bq/L.1 Van Metre and Gray (1992) showed that dewatering an underground uranium mine located near Gallup, New Mexico, increased dissolved gross alpha, gross beta, uranium, and radium activities in the Puerco River from 1967 until 1986. Activities of the radionuclides declined rapidly once treatment of the water was initiated in the mid-1970s to bring the watercourses into compliance with the limitations specified by the National Pollutant Discharge Elimination System. Mine discharges into the Puerco River were subsequently treated with a focculant and barium chloride to reduce total suspended solids concentrations and co-precipitate radium; dissolved uranium concentrations were reduced using an ion exchange treatment. To meet water quality standards, modern dewatering of uranium mines would provide for waste-water treatment prior to any release off-site.

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1 See http://www.bape.gouv.qc.ca/sections/archives/oka/docdeposes/documdeposes/DB86.pdf.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

flooded underground mines represent a source of groundwater contamination and, if allowed to overflow, a potential surface water contamination source as well. The tailings management area was constructed as an unlined abovegrade facility, using an earthen dam to retain both solid and liquid tailings and enable chemical treatment of the mill effluent prior to discharge into Snake Creek and Island Lake. The tailings management area represents the principal on-site source of potential long-term environmental effects, although geotechnical evaluations of the earthen dam determined it to be stable, structurally sound, and in compliance with all design specifications. Given its location in a topographic low, constructed surface diversions were employed to isolate the tailings management area from the erosive effects of inflowing surface water.

A variety of mitigation options were considered as part of the environmental assessment process to address the remaining significant environmental issues at Cluff Lake with the explicit goal of minimizing long-term active mitigation activities (e.g., groundwater pumping, water treatment). Preferred mitigation strategies identified included (1) backfilling the pits with waste rock and capping with compacted till, (2) capping the Claude waste rock pile with a dry cover to minimize infiltration and AMD, (3) sealing of surface openings in underground mines to prevent overflows, (4) covering the tailings management area with a secondary layer of till, and (5) allowing natural recovery of Island Lake water quality. Although these options are likely to mitigate the remaining environmental problems at Cluff Lake to a significant degree, experience has shown that the environmental legacy of uranium mining is persistent over long periods of time. Monitoring and assessment (including a structured follow-up program to evaluate the performance of the mitigation strategies) will play an important role in guiding implementation of any additional mitigation at the site (CNSC, 2003).

Waste/Tailings Management

The effects of mine waste and tailings management on surface waters would depend on the amount and composition of the various waste materials, the methods used in processing the uranium ore, the ways in which the various waste materials are stored and disposed, and the steps taken to reduce the impacts on surface water quality. Mine and mill tailings contain all of the naturally occurring non-radioactive and radioactive elements found in uranium ore; these include all of the radionuclides in the uranium decay series, especially those of 238U. Although 90-95 percent of the uranium in the ore is extracted during processing (thus reducing uranium concentrations by at least an order of magnitude), most of the uranium decay products (e.g., 230Th, 226Ra, 222Rn), which may comprise the majority of the total radioactivity of the ore, stay in the tailings (Hebel et al., 1978, Van Metre and Gray, 1992). Because of the lengthy half-life of 230Th (76,000 years), the activity of the tailings will remain essentially unchanged for

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

image

FIGURE 6.2 Waste management in the JEB pit at McClean Lake in Saskatchewan, Canada. SOURCE: AREVA Resources Canada Inc.

many thousands of years (Hebel et al., 1978). The geochemistry and mineralogy of 230Th and 226Ra (1,625-year half-life) are of particular importance from a water quality perspective, given their relatively long half-lives. Thorium is highly insoluble in aqueous solution under slightly acidic to alkaline conditions. The solubility of thorium increases in acidic aqueous solutions, and so tailings solutions can contain very high concentrations of 230Th under acid-generating conditions. Radium in mill tailings can be adsorbed or co-precipitated with Fe-Mn hydrous oxides, gypsum, barite, or amorphous silica under oxidizing conditions, keeping 226Ra concentrations in solution very low (Abdelouas, 2006). Although concentrations are reduced by processing, uranium is more mobile than either thorium or radium at near neutral pH under oxidizing conditions.

Uranium extraction using a strong acid leaching technique also tends to solubilize metals—the same process that occurs in AMD. Therefore, acid-leached tailings need to be carefully managed (e.g., neutralized and/or contained) to minimize the release of acidity, toxic metals, and radionuclides into surface water and groundwater environments. Modern tailings management sites are designed to remain segregated from the hydrological cycle for “1,000 years to the extent reasonably achievable and in any case for at least 200 years” to control mobility of metals and radioactive contaminants (10 CFR Part 40, Appendix A, Criterion 6(1)). If tailings are not emplaced in the mine workings as part of the

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

closure plan, then they are placed in an engineered disposal cell. In a relatively wet climate such as exists in Virginia, it is assumed that tailings would be stored in a saturated condition to minimize oxygen entry, sulfide oxidation, and mobilization of heavy metals and radionuclide elements from the facility (i.e., AMD). As shown at Elliot Lake and elsewhere, lined and capped storage repositories can prevent the spread of tailings by erosion and control contamination of ground-water and surface water systems from seepage (Peacey et al., 2002; Abdelouas, 2006), but no method of isolation is 100 percent effective nor has one been shown to be effective in perpetuity. Moreover, in a hydrologically active environment such as Virginia, with relatively frequent tropical and convective storms producing intense rainfall, it is questionable whether currently engineered tailings repositories could be expected to prevent erosion and surface and groundwater contamination for 1,000 years (Hebel et al., 1978). There are many reports in the literature of releases from improperly disposed tailings (e.g., Waite et al., 1988, 1989; Mudd and Patterson, 2010) and their environmental effects (Van Metre and Gray, 1992).

Full belowgrade disposal of mill tailings (Figure 6.2) is an option that has been developed specifically to eliminate concerns over the release of tailings due to catastrophic failure of a constructed retaining berm or tailings dam (see Box 6.2). Nevertheless, pending detailed site-specific characterization and engineering studies at potential uranium processing facility sites, the use of partially abovegrade tailings facilities cannot be discounted. For example, the Piñon Ridge uranium mill, the first new uranium mill in the United States in a generation, recently received license approval from the state of Colorado.2 At that site, full belowgrade tailings disposal was considered the best option, but a partially abovegrade design with perimeter berms satisfied the relevant regulations and was recommended following detailed site-specific characterization.3 Therefore, the potential hazard of a sudden release resulting from the failure of a constructed retaining berm remains. An aboveground tailings dam failure (e.g., due to liquefaction associated with a seismic event, an exceptionally high rising rate from local precipitation, improper spillway design leading to overtopping) would allow for a significant sudden release of ponded water and solid tailings into receiving waters (see Box 6.2). Such failure could necessitate aggressive remediation strategies, possibly including dredging, containment, and long-term water treatment. However, the committee cannot estimate the scope of possible remediation measures needed, because these would be dependent on site- and event-specific conditions. For more information on the remediation of radioactive wastes in the environment, see NRC (2009a,b, 2010) and USEPA (2008).

One of the most significant, if poorly publicized, tailings dam failures from

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2 See http://www.cdphe.state.co.us/release/2011/030711.pdf; accessed July 18, 2011.

3 See http://www.cdphe.state.co.us/hm/rad/rml/energyfuels/application/licenseapp/tailings/rpt.pdf; accessed July 18, 2011.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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BOX 6.2
The Virginia Beach Study:
A Preliminary Assessment of Potential Impacts of
Uranium Mining in Virginia on Drinking Water Sources

The Coles Hill uranium deposit and a number of other properties with former uranium leases (but unproven potential) are located upstream of Virginia Beach’s drinking water intake, located in Lake Gaston. Lake Gaston is fed from the Kerr Reservoir which, in turn, is fed by the Dan, Bannister, and Roanoke Rivers in the Roanoke River Basin. The city of Virginia Beach commissioned a study (Baker, 2010) by the Michael Baker Corporation to “model and estimate the water quality impacts from a storm-based breach of a uranium mill tailings confinement structure, which results in a large release of mill tailings downstream to the Banister or Roanoke rivers” (Leahy, 2011). Notably, the statement of task did not ask the study to address the likelihood of such an event; it asked only for an analysis of the outcome assuming it did occur. Virginia Beach representatives made clear that the study simulated a “rare event that regulations are supposed to prevent” (Leahy, 2011). Although the Coles Hill property is encompassed by the study extent, the study was not specific to Coles Hill.

The final report, released in February 2011, summarized the results of nearly 200 model simulations. The scenarios differ by varying one of five primary input variables: tailings volume, sediment concentration by weight of the tailings, tailings particle size distribution, radioactivity level of the tailings, and flood hydrograph of the receiving surface water body. Both “sunny day” and extreme stream discharge scenarios were considered. Model parameter values were determined by researching the available literature because of the shortage of site-specific data for the area of interest. In particular, the authors relied on a study of tailings dam failures (Rico et al., 2008) and the empirical relationships derived therein to estimate outflow volume, run-out distance, and peak discharge. A comprehensive summary of the study is beyond the scope of this report but the key findings include:

• A tailings dam failure could significantly increase the radioactivity in the river-reservoir system for extended periods of time.

• Under such an event as simulated, the gross alpha concentration in Kerr Reservoir could remain above the USEPA maximum contaminant level (MCL) for several months or more.

• The model estimates that the majority of radioactivity entering the river-reservoir system remains in bed sediments over the simulation period of 1 year after failure. The remainder passes over Kerr Dam into Lake Gaston.

• Under such an event as simulated, uranium concentrations in the water column in Kerr Reservoir may temporarily reach or exceed the MCL of 30 µg/L.

• Reservoir operations affect the arrival and residence times of radioactivity in Kerr Reservoir.

Virginia Uranium, Inc. (VUI) commissioned KleinfelderWest, Inc. to review the Virginia Beach study (Baker, 2010) and made the results of that review available

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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to the committee in late June 2011. It was Kleinfelder’s opinion that Baker did use appropriate methods and models in their study, but they questioned some of the assumptions of the study. Kleinfelder’s largest criticism is that the initial assumption of a tailings dam failure as dictated by the statement of work is incorrect because (i) they estimate the probability of such a failure to be remote, and (ii) USNRC guidelines for disposal cell siting and design discourage abovegrade or partially abovegrade tailings disposal, while acknowledging that VUI is considering partially abovegrade disposal. As noted above, Colorado (an agreement state, see Chapter 7) recently approved and licensed a partially abovegrade tailings disposal design for the Piñon Ridge uranium mill even though fully belowgrade disposal was considered the best option.

a uranium mine/mill complex in the United States occurred near Church Rock, New Mexico, in June 1979. A breach of an earthen dam containing solid and liquid tailings caused the release of 1,100 tons of radioactive mill waste and 95 million gallons of mine effluents. It has been estimated that the breach allowed the release of 46 Ci of radiation—more than three times the release from the nuclear accident at Three Mile Island (Brugge et al., 2007). This spill illustrates the significant potential impacts from failure of an abovegrade tailings dam, reinforcing the desirability of belowgrade emplacement of tailings noted in Chapters 4 and 8, and in IAEA (2010).

Based on studies conducted at Elliot Lake, Canadian regulatory authorities identified several key factors that affect the capacity to adequately contain tailings waste in perpetuity4 in modern tailings facilities (CEAA, 1996). These factors, which are highly relevant to uranium mining in Virginia, include drought episodes that could cause wastes to be exposed to oxygen; erosive effects of intense rainfall and flood events on dams, berms, or other physical impoundment structures; seepage and groundwater flow between the waste management area and the surrounding geological strata; and other natural disasters. Based on factors such as these, the Elliot Lake Environmental Assessment Panel concluded: “No containment system can totally preclude some release of contaminants” although the panel asserted that the Elliot Lake mitigative strategies “can hold the rate of release within acceptable limits” (CEAA, 1996).

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4 The government of Saskatchewan has established the Institutional Control Program for postclosure management of decommissioned mine and mill properties that requires “a detailed monitoring and maintenance plan for the management of the site in perpetuity … to ensure the site continues to meet the conditions specified at the time of entry into the Institutional Control Registry” (Saskatchewan Ministry of Energy and Resources, 2009).

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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The committee did not conduct a risk assessment for uranium mining in Virginia because a detailed site-specific analysis is beyond the committee’s charge. The first step in assessing the risks associated with the release of contaminants from the uranium mine and mill would be to conduct a vulnerability analysis for security events and a risk analysis for natural disasters and other accidents. The consequences are not determined by the initiating event—they are determined by the design of the facility and whether the facility has appropriate spill prevention, containment, and countermeasures. The potential for long-term environmental effects requires a probabilistic risk assessment, driven in part by the inherent risks posed by the uranium mining, processing, and waste handling, but mitigated by the pollution prevention measures. A comprehensive risk assessment, including accident and failure analyses, is an essential step in any site-specific permitting decision. On the basis of an examination of published studies, the committee concludes that best practices, if properly implemented in association with rigorous monitoring, should address or allow the site operator to take action to mitigate the majority of short-term environmental effects from routine uranium-specific mining and processing activities. However, until site-specific risk and vulnerability assessments are conducted, the short-term risks associated with natural disasters, accidents, and spills remain poorly defined. If a major failure of waste containment facilities occurs, due either to extreme natural events or inadequate design, construction, or maintenance of such facilities, the potential long-term environmental effects are likely to be more than trivial. Temporary storage of mill tailings can pose greater short-term environmental risks, unless these facilities are also designed and constructed to contain the waste and treat all effluent under extreme climatic variability.

As discussed previously, waste rock piles, composed primarily of overburden or low-grade ore from either deep and/or surface mining operations, can also contribute to degradation of surface water quality (e.g., Rum Jungle, Cluff Lake). The disposal of waste rock is an issue in mining in general, because the volume of the mine voids cannot contain the entire volume of material removed during a mining operation; waste rock is typically stored in aboveground piles near a mine to minimize handling and disposal costs. Management of waste rock piles at uranium mines has evolved from the realization that all waste rock does not behave the same geochemically. The presence of metal sulfide minerals in portions of the waste rock is a cause of particular concern because of the possibility of AMD, and so proper characterization of the chemical properties of waste rock throughout the mining process is an important first step in addressing this potential hazard. Exposure of fresh mineral surfaces to oxygen during mining makes the waste rock more chemically reactive. Modern mitigation techniques for waste rock disposal would also include (1) careful siting of waste rock piles and construction of drainage ditches to facilitate collection of leachates; (2) isolation and burial of waste rock with high potential for contamination in low permeability strata to minimize interactions with water and air; and (3) if warranted, chemical

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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treatment of drainage water collected from waste rock piles. During decommissioning, soil covers can be used to control infiltration and production of leachate from waste rock piles.

General Mining Effects

Land disturbance by modern surface mining activities would be expected to increase the concentrations and loads of many dissolved and suspended non-radioactive substances in surface water, including some that are particularly important for water quality and aquatic biota: sediment, phosphorus, nitrate, metals, metalloids, and strong acidity. Elevated sediment loads are virtually ubiquitous in disturbed watersheds. In one of the most complete experimental studies in the literature, Bonta (2000), working on three surface-mined watersheds in Ohio, showed that sediment yields during active mining and reclamation activities increased by factors of between 46 and 1,310 relative to premining conditions. Use of diversions to reduce overland flow actually increased sediment loads because water that was concentrated in inadequately protected channels caused channel erosion or in other cases overtopped the diversions, causing rill and gully erosion. Reducing bare-soil exposure times reduced sediment yields, and sediment concentrations over the full range of measured flows were restored to undisturbed levels when diversions either were not used during reclamation or had been removed. In a comparative study of a reclaimed mineland and a forested control watershed in western Maryland, Simmons et al. (2008) showed that the mean sediment concentration from reclaimed mineland was approximately threefold higher than from forested watersheds. Comparable increases in sediment loads would be expected from surface mining for uranium in Virginia, but underground mining would not be expected to cause such impacts.

Concentrations and loading rates of many dissolved nonradioactive constituents in surface water (particularly sulfate) have been shown to increase as a result of surface mining of coal and subsequent reclamation (Bonta and Dick, 2003). Increases in the extent of surface runoff contribute to increases in constituent loads (load is the product of concentration and hydrological flux). The initial phases of mine reclamation can include additions of fertilizer, herbicides, and soil amendments that can also contribute to the contaminant runoff of the surface waters. Simmons et al. (2008) showed that the annual load of total phosphorus was a factor of 1.5 times larger from reclaimed mineland compared with forested watersheds.

Surface Water Quantity

Lands used for either underground or surface mining of uranium in Virginia would be expected to periodically discharge water off-site. The rates of discharge would be controlled by (1) precipitation inputs (e.g., rainfall intensity),

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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(2) antecedent moisture conditions, (3) land surface properties (e.g., soil infiltration capacity), (4) available water storage (e.g., detention ponds, pit storage), and (5) intentional releases of water from mining operations. Relative to unmined lands covered by native second-growth forests, surface runoff from lands disturbed by mining would likely be greater on-site. The relative increase in runoff would also cause increases in stream discharge in downstream receiving waters, although the percentage increase would be reduced with distance from the mines. The following sections explore the various impacts on surface water quantity from modern uranium mining and processing. These impacts per unit area disturbed would be comparable to those observed for other types of mining in Virginia, although the surface water quantity effects from tailings management could be greater.

Mining Effects

On-site and downstream surface runoff effects would be expected to vary depending upon whether mining is underground, surface, or some combination of the two. As a result of its smaller land surface footprint, underground mining would have the advantage of causing lesser impacts on surface water hydrology both off-site and downstream. The specific impacts associated with underground mining of uranium in Virginia are

• disruption (or total cessation) of spring flows and stream baseflow on-site due to blasting of rock (with decreased flows propagated to receiving waters downstream), depending on local geology, and

• increased flows in receiving streams owing to mechanical pumping of groundwater from underground mine workings (with increased flows propagated to receiving waters downstream).

Surface mining, on the other hand, would be expected to produce significant increases in surface runoff (especially stormflow) on-site relative to the unmined condition. Several field and modeling studies of surface mining for coal in the Appalachian Mountains of the United States have shown that rates of storm runoff generally increase (relative to a forested reference basin) with increasing mining activity in a watershed. Based on a field study of surface mining in Ohio in which both storm rainfall and runoff were measured, Bonta et al. (1997) showed that the “curve number” (a term describing the potential for surface runoff, with higher numbers reflecting greater runoff potential; NRCS, 2010) increased from a value of 76 for a premining condition to 87 during a period of active mining. As an example, for a 10-year, 24-hour event in Virginia that produces 6.0 inches of rainfall (Hershfield, 1961), this difference in curve numbers translates to a 36 percent increase in storm runoff (from 3.3 in to 4.5 inches of runoff) that is attributable to mining. However, caution is needed when extrapolating from coal

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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mining studies, because surface uranium mines are generally less extensive operations compared with surface coal mines.

Increased stormwater runoff on-site due to mining is mostly attributable to decreases in interception storage by vegetation and soil infiltration capacity because vegetation and soils are removed prior to mining of the rock (Ritter and Gardner, 1993; Bonta et al., 1997; Negley and Eshleman, 2006), although some additional effects are expected from road construction. Increases in stormflow could be modulated to some degree by utilizing the mining pit for temporary water storage, but typical sediment detention ponds provide little in the way of stormflow attenuation, particularly for extreme events. Stormflow increases would be expected to propagate to receiving streams downstream (with the local increase gradually attenuated farther downstream). Bonta et al. (1997) used flow-duration analysis to demonstrate that surface mining can also cause significant changes in baseflow levels in streams, but the changes were variable among the watersheds examined and a responsible mechanism could not be determined.

Numerous studies have shown that reclamation of a mine site does not dramatically reduce storm runoff (Ritter and Gardner, 1993; Bonta et al., 1997; McCormick and Eshleman, 2011). Negley and Eshleman (2006) showed that a reclaimed coal mine in western Maryland produced, on average, higher mean peak storm discharges and storm runoff depths by about a factor of 2-2.5 relative to a nearby forested reference watershed, despite the fact that only about 50 percent of the reclaimed watershed had been mined and reclaimed. Soil compaction resulting from the use of heavy, earth-grading equipment during the reclamation process dramatically reduces soil infiltration capacity and increases storm runoff. McCormick et al. (2009) and Ferrari et al. (2009) showed that local increases in storm runoff attributable to spatially distributed surface mining and reclamation in the Appalachian Mountains are propagated to receiving rivers downstream.

Waste/Tailings Management

The effects of the mine and mill tailings disposal on surface water hydrology would be similar to those associated with mining itself: greater storm runoff from disturbed land, including land previously mined and used for tailings disposal. Closed tailings ponds, however, would be expected to produce much greater storm runoff per unit surface area (because of the placement of impervious caps) than the forested land that they replace. Depending on the scale of the tailings management area, properly engineered, sited, and constructed tailings disposal areas would not be expected to significantly affect surface water hydrology. A tailings dam failure, however, would allow for a significant sudden release of ponded decant water into receiving waters, as discussed in the previous section (see Box 6.2).

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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GROUNDWATER EFFECTS

Groundwater fills the fractures in rocks and openings between mineral grains beneath the land surface and supplies wells, springs, and seeps (see also Chapter 2 and Figure 2.4 for a discussion of Virginia’s groundwater resources and its use by Virginia residents). Numerous National Research Council reports detail the enormous challenges and remaining technological gaps associated with remediating groundwater contaminated with metals and radionuclides (NRC, 2008a, 2009a,b, 2010). Therefore, the design and use of effective mitigation measures to prevent contamination are preferred over relying on groundwater cleanup after contamination has occurred. In this section the potential effects of modern uranium mining practices on groundwater quantity and quality are discussed.

Groundwater Quality

Groundwater in contact with aquifer solids will attain a chemical composition that reflects the composition of the host rock through geochemical reactions. The extent of these reactions, and therefore the chemical composition of the water, depends on a number of geochemical and hydrogeological factors including but not limited to the mineralogy of the host rock, the mineral grain size, the chemical composition of the water passing through the aquifer, the residence time of the water in the aquifer, and flow pathways (e.g., fracture flow versus flow through granular porous media) (Cameron, 1978, 1980; Langmuir and Chatham, 1980; Rose and Wright, 1980; Giblin and Dickson, 1992; Leybourne and Cameron, 2006; Birke et al., 2009, 2010). Mining activities can alter several of these variables, consequently changing the quality of the groundwater. A carefully developed groundwater monitoring program with sufficient baseline data would be necessary to distinguish the effects of mining activities from existing groundwater conditions and naturally occurring concentrations of trace elements and radionuclides (discussed later in this chapter).

Exploration and Mining Effects

Uranium exploration efforts via systematic drilling to better define subsurface deposits has the potential to affect water quality, depending in part on the local setting, drilling methods, and how the boreholes are handled after completion. Installation of the borehole itself can alter the local geochemistry leading to the undesirable increased solubility and mobility of some elements. For example, introduction of oxygen into wells in eastern Wisconsin led to sulfide mineral oxidation and consequent decreased groundwater pH and increased concentration of sulfate, nickel, manganese, zinc, and arsenic (Schreiber et al., 2000; Gotkowitz et al., 2004). Similarly, introduction of oxygen into boreholes could oxidize poorly soluble reduced uranium(IV) minerals generating soluble and more mobile

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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oxidized uranium(VI) species. These effects are frequently limited to the local vicinity of the borehole itself.

Artificially connecting separate aquifers by drilling through confining layers or installing wells with long well screens can mix chemically distinct waters, which could result in the undesirable enhanced solubility and transport of elements that previously had been poorly soluble and immobile. Leakage of lower pH, oxygenated water from an unconfined upper aquifer into higher pH anoxic water in a lower confined aquifer through multiaquifer wells has been implicated as the primary cause for elevated uranium concentrations in a public supply well in York, Nebraska (Clark et al., 2008; Landon et al., 2008). Drill holes and mine shafts can serve as pathways for the upward migration of deeper saline water. Deep groundwater in some areas of Virginia is saline and, if under artesian pressure, would naturally flow upward to shallower depths if a conduit for flow were present. To protect groundwater quality, it is common practice for exploratory boreholes not completed as wells to be plugged with an acceptable material and abandoned, and Virginia exploration licenses typically require description of these actions by the applicant.

Many of the same potential impacts to groundwater quality described for drilling apply to underground exploration and mining; in particular, the effects of direct introduction of oxygen into the subsurface that can mobilize uranium and form acid mine drainage (as discussed previously), and the artificial connection of separate aquifers. Neves and Matias (2008) investigated groundwater quality in the vicinity of the abandoned Cunha Baixa uranium mine in central Portugal. Groundwater in wells downgradient from the abandoned mines showed degraded quality with elevated concentrations of uranium, copper, nickel, total dissolved solids, aluminum, manganese, iron, and zinc, which are characteristic of acid mine drainage. These processes have the potential of increasing the concentration of groundwater constituents above primary, secondary, or aesthetic standards (see Chapter 7).

Processing

Failures in on-site storage or accidents in the loading or transportation of chemicals used in the extraction process could result in a spill that infiltrates into the groundwater, resulting in groundwater contamination. Appropriate mitigation measures to minimize the impacts of such an event include administrative and engineering controls (e.g., access control, lock-out/tag-out procedures, secondary containment) and treatment, testing, and recycling of mill effluents prior to release to the environment. Treated effluent from operating Canadian uranium mills is below the screening objective of 100 µg/L uranium, with most below 10 µg/L (CNSC, 2010).

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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Waste/Tailings Management

Tailings from ore processing contain residual uranium, radionuclides from the uranium decay chain, and other chemical constituents associated with the ore or possibly with the milling process. Threats to groundwater quality related to modern tailings management originate from two sources: (1) failure of the structures designed to limit the movement of contaminants from the tailings into surrounding groundwater (e.g., tailings retaining structures, failure of the liners(s) and leak collection systems), and (2) inadequate hydraulic isolation in belowgrade disposal facilities (e.g., pump failure in active isolation, inadequate understanding of site hydrogeology, inadequate compaction of tailings in passive hydraulic isolation). Tailings disposal cells may be constructed specifically for that purpose or may be located in previously mined-out areas. As noted previously in this chapter, after uranium processing, the majority of the original radioactivity remains in the mill tailings after extraction of the uranium. The solid-phase concentrations of the radionuclides and co-occurring potential contaminants of concern (e.g., vanadium, arsenic) in the mill tailings will depend on the ore grade, site-specific mineralogy, and uranium extraction process (acid versus alkaline leaching). Additionally, the concentration they achieve in the tailings fluid will depend on water-mineral kinetic and thermodynamic constraints; changes to the chemistry of the tailings water can alter dissolved contaminant concentrations. Both dissolved and solids-associated contaminants in the tailings present a hazard to groundwater but the risk can be mitigated by recycling and treating water in tailings management facilities (see Chapter 4).

The method of tailings disposal will also influence the potential impacts of uranium mining and processing. Belowgrade disposal in a pit or abandoned mine workings would have the benefit of minimizing radon release and acid formation because the tailings could be covered with water. Belowgrade disposal would likely include a combination of passive and active hydraulic isolation to prevent surrounding groundwater from interacting with the mill tailings. Passive hydraulic isolation employs materials of contrasting permeability to direct water flow around rather than through the tailings. Active hydraulic isolation, similar to mine dewatering, uses a series of actively pumped wells to lower the local water table and maintain groundwater flow into rather than through or out of the tailings. If active hydraulic isolation is used, an important step would include sending the water for treatment at an on-site water treatment facility prior to releasing it to the environment.

Design for a tailings holding cell would include multiple barriers to minimize the risk of groundwater contamination. These barriers likely would include compacted clay overlain by two synthetic liners with a leak collection system placed between them, and engineering design criteria for tailings management would presumably be set forth in state regulations. Failure of the liner system could lead to large volumes of liquid lost relatively slowly over time without notice

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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unless or until detected in monitoring wells around the site. As discussed previously, tailings could be stored aboveground, partially aboveground, or entirely belowground. In the case of an aboveground or partially aboveground tailings facility, a tailings dam failure could lead to significant release of contaminated water. The fraction of water released that would recharge the aquifer and contaminate groundwater (as opposed to discharging to surface waters) would depend on several factors including topography, soil type, and antecedent soil moisture conditions.

To date, modern tailings disposal cells have been effective at preventing groundwater contamination (USDOE, 2010, 2011). Nevertheless, it should be stressed that currently none of these cells exceed 25 years in operational lifetime. So, while it is reassuring that the engineering designs have performed to expectation in the very near term, predictions on their behavior for the next 175 to 975 years have a high degree of uncertainty due to a lack of long-term performance data (NRC, 2007). In light of this uncertainty it is difficult to gauge the long-term risk associated with disposal cell leakage.

Groundwater Quantity

Operation of a uranium mine could be expected to affect groundwater quantity at the mine site with potential effects propagating off-site. Early phases of uranium mining (exploration and construction) would have negligible effects. However, during active mine operations, there could be significant effects on groundwater quantity.

Mining Effects

By lowering the water table to facilitate mining, mine dewatering can lower the groundwater levels in surrounding wells, possibly causing some nearby wells to go dry. Affected households would have to either drill deeper wells or find an alternate source of water. The extent of lowering of the water table is related to the volumetric rate of water withdrawn, aquifer permeability, and area ground-water recharge features (e.g., surface streams that recharge groundwater). This dewatering effect is greatest near the mine (or the dewatering wells) and diminishes with increasing distance. However, it is important to note that the effect can differ with direction from the well because of anisotropy in aquifer permeability (Figure 6.3). Under drought conditions, the difference between the water table at the mine site and unaffected groundwater levels decreases, because groundwater levels are lowered overall, reducing dewatering demands.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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image

FIGURE 6.3 Measured potentiometric surface of the Sinnipee aquifer, southwest Wisconsin, during active dewatering of underground zinc-lead mines. Mines are located in proximity to the starred location in the left-center portion of the figure. The elliptical shape of the contours reflects anisotropic (direction-dependent) preferential flow along the diagonal from lower left to upper right. SOURCE: Modified from Toran and Bradbury (1988).

Reclamation and Postclosure

At mine closure, dewatering typically stops and mine workings are allowed to flood and groundwater and local water table levels will begin to rise. It could be many years to decades before water levels return to premining levels (Toran and Bradbury, 1988; Adams and Younger, 2001; Banks et al., 2010; Martinez and Ugorets, 2010; Caine et al., 2011). Additionally, because of mine construction disturbance to the aquifer, local groundwater flow patterns may be permanently altered, which could affect water supply for nearby domestic supply wells, although this effect is likely to be minor overall. Local groundwater recharge rates are also likely to be reduced as discussed previously in the section on surface water runoff. Finally, the decision to allow the mine to flood at closure, and under what conditions, needs to be carefully evaluated to prevent unintentional contamination

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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of groundwater. For example, backfilling the mine with low-permeability material prior to flooding can minimize groundwater flow though the abandoned mine works.

SOIL EFFECTS

Mining activity involves the removal of soil and overburden, which directly affects the physical, chemical, and biological properties of soil. The most common effects are loss of pore space due to compaction and changed soil structure, loss of permeability, changes in the ability of the soil to provide moisture for plant growth, loss of living organisms vital to healthy soils (e.g., microorganisms and earthworms), loss of viable seed bank with extended storage, loss of soil organic matter and nitrogen, and accelerated erosion. These impacts are not unique to uranium mining but are common to modern mining operations and large-scale industrial disturbance in general. These primary impacts are largely contained within the mining site, and the extent of soil impacts resulting from mining activities depends on the type of mining adopted. In the case of underground mining, impacts to soil are at a minimum because the surface disturbance is restricted to the relatively small underground entrances. In contrast, for open-pit mining the amount of disturbed soil is at a maximum. In addition, secondary effects, such as increased water runoff due to soil compaction, described previously in this section, can impact offsite conditions.

During mine site reclamation, topsoil that had been stockpiled during the mining process is replaced on the land. Reclaimed soils, however, are fundamentally different from natural soils in their physical, chemical, and biological properties, and some of these differences can take as little as 20 years or more than 1,000 years to recover. For example, stripping, stockpiling, and replacing the topsoil erases the natural soil horizons that develop over hundreds to thousands of years. Stockpiled topsoil deteriorates because of changes in the physical, chemical, and biological characteristics resulting from compaction, leaching, and degradation of the nutrients. Williamson and Johnson (1990) concluded that the nitrogen reserves in topsoil that was stockpiled and subsequently replaced were wasted because of changes in nitrogen cycling in those soils while they were stockpiled. Additionally, there were long-term changes to the microbial community (bacterial and fungal) of stockpiled soils that altered their function when used to restore mine sites relative to premining conditions or unmined areas (Johnson et al., 1991; Williamson and Johnson, 1991).

Reclaimed soils also tend to be compacted with an accompanying decrease in permeability and increased runoff (Marashi and Scullion, 2004). Sinclair and Dobos (2006) found that seven of eight reclaimed soils, varying in age from 6 to 17 years, had a lower land capability classification (LCC) relative to their premined condition. The primary factor responsible for the lower LCC in each case was a decrease in the soil’s available water capacity—a measure of the

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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water a soil holds in a form available to plants. This suggests that reclaimed soils have degraded water capacity for long periods. Changes to the soil water capacity, coupled with changes to the chemical and microbiological properties of the reclaimed soil suggest that these soils would have lower long-term crop yields. Additionally, moisture stress will be a major factor dictating which plants will be successful on reclaimed soil. These differences in reclaimed versus pre- or unmined soils suggest that different soil management strategies for reclaimed soils would need to be in place for an extended period of time.

AIR EFFECTS

Citizens expressed concern about the air pollution and particulate matter that could be generated by a uranium mining and processing operation, and mobilization of contaminants by airborne mechanisms. Off-site transport of particulate matter causes nuisance effects, such as impaired visibility and dust accumulation on cars and houses. However, exposure to particulate matter can also lead to increased asthma, as documented by increased visits to emergency rooms, and even to death from heart or lung disease (Pope et al., 2009; Anenberg et al., 2010). People with increased susceptibility include infants, children, and adolescents; the elderly; people with respiratory conditions such as asthma, bronchitis, or emphysema; people with heart disease; and people with diabetes. The human health effects of airborne particulate exposures are described in Chapter 5; in this chapter, the committee describes the potential for off-site transmission of contaminants and air pollution effects on the environment at modern uranium mining and processing facilities.

Environmental and human health effects depend on a number of factors, including the chemical composition of the particles, the concentration, particle size and shape, and exposure time (IAEA, 2008). Distance of travel will be dependent on meteorological factors, particle size, and site conditions, among other factors. Depending on the size of the site and the dust control procedures implemented, there may or may not be off-site impacts. Large particles (>10 microns) settle out quickly from the air. However, to determine off-site human health and environmental exposure potential from dust (and particle-associated contaminants), meteorological modeling is essential. Modeling can be used to make estimates of the extent of particle transport under typical wind speeds and direction, as well under extreme weather conditions.

Uranium Mining and Processing

Mining Effects

Much of the dust caused by mining operations consists of fine particles that are generated from the mechanical disturbance of rock and soil, bulldozing, blasting,

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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and vehicles traveling on dirt roads. Particles can also be mobilized by wind blowing over ore stockpiles. Radioactivity monitoring at the fenceline, as well as at selected off-site locations can be used to verify the modeling predictions about off-site contamination. The Mine Safety and Health Administration (MSHA) requires radon monitoring of exhaust air from underground uranium mines for the purpose of estimating worker exposure, but these measurements have application for offsite exposure assessments as well. Continuous monitoring for air emissions at the fenceline, including dust, radon, and radon progeny, is an accepted practice by industry (see Chapter 8 for a discussion of monitoring best practices).

Processing Effects

Breaking the uranium ore into finer particles can occur as part of the mining or the processing. Processing will take place in a building, and significant controls can be in place to keep emissions to a minimum. Radioactive effluents that could be airborne include particles and gases. Control measures include enclosure of dusty operations, dust collection systems, dust suppression systems, spraying or wetting dust, ventilation systems specific to conveyor belts and other rock moving systems (see also Chapter 8 for best practices). Models can be used to predict off-site exposure to radon vented from the mining and processing operations.

Chemicals used as part of the processing operations, such as anhydrous ammonia or sulfuric acid used in leaching, could have significant off-site human health impacts under catastrophic accidental releases. Thus, facilities that store significant quantities (i.e., greater than 10,000 lbs) need to meet proper handling requirements, including safety equipment (e.g., devices preventing releases if hoses are severed, remotely operated shutoff valves) and training for employers and employees.5 If more than 10,000 pounds of anhydrous ammonia are stored on-site, facilities are subject to additional regulatory controls (see Chapter 7).

Other chemicals that could be used in the processing operations include sulfuric acid, solvents such as high-purity kerosene, and peroxide. To minimize off-site impacts, air pollution controls need to be matched to the anticipated airborne effluents and appropriate scrubbing employed, with stack-based and off-site air quality monitoring to confirm proper equipment functioning (see Chapter 8).

Waste/Tailings Management Effects

Large amounts of rock are removed during the mining process that contain measurable quantities of uranium but are not economically viable for uranium production (also called protore). Therefore, large quantities of waste rock at a mining operation will emit radon and may generate wind-blown particulates if dust controls are not in place. Evaporation ponds and tailings impoundments are

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5 See http://www.osha.gov/dts/shib/shib120505.html.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

another potential source of radon and airborne particulate radionuclides. Particular attention should be paid to dewatering activities of the waste or tailings because this may increase the rate of airborne contamination. Although protore and waste tailings may not contain enough uranium for processing to be cost-effective, there is still measureable radioactivity, which has off-site exposure potential.

If appropriately designed, capping of the waste storage pile can prevent airborne reentrainment of fine particles. Cap maintenance activities, however, will need to continue for thousands of years (potentially the responsibility of the U.S. Department of Energy Office of Legacy Management; see Chapter 7). Additionally, periodic inspection of the cap and repairs, as necessary, are essential to ensure that burrowing animals, erosion, or other weathering effects do not decrease the effectiveness of the cap in minimizing air pollution impacts.

General Mining-Related Concerns

During construction, exhaust from construction equipment, soil entrainment, and fugitive dusts will be generated, as at any construction site. Control measures would include dust suppression systems, spraying or wetting dust, and washing construction equipment before it leaves the site. Construction equipment and transport vehicles are powered by diesel engines, which generate diesel fumes.

Open-pit and subsurface mines have different air impacts. Open-pit mines generate dust directly to the air through blasting, loading into transport vehicles, and transport to the processing facility. Subsurface mines require ventilation systems to protect the workers, but vented dust will enter the ambient air. Air pollution controls, however, can be installed on the vents to decrease particulates.

ECOLOGICAL EFFECTS

Many of the ecological impacts of uranium mining and processing will be similar to other forms of hard-rock mining, in that both physical impacts and chemical impacts may occur. Physical impacts may include increased sediment loads and habitat disturbance, whereas chemical impacts may include emissions from diesel equipment or contaminated water from mine pits. The principal features that are specific to uranium mining will be the toxicity of radioactive materials and those materials co-occurring with uranium and the toxicity of chemicals specific to uranium processing. Therefore, this section begins with an overview of uranium-mining-specific effects, followed by a discussion of general mining effects.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

Uranium Mining and Processing

Uranium mining and processing pose ecological risks beyond typical mining operations, particularly if the site is not managed using internationally accepted best practices. Past uranium mining activities in many parts of the world that were not in accord with modern best practices continue to require expensive remediation to clean up contaminated areas (see, e.g., Box 6.3). Modern mines treat the water from all mine operations, including the mine, processing facility, and tailings impoundment, prior to discharge and aim to control fugitive dust. Modern uranium processing operations are designed, constructed, and intended to be operated in a clean environment in which all materials are accounted. In such an ideal modern facility, fugitive emissions will be monitored and largely captured and not released into the environment. Under those circumstances, ecological risks from uranium mining and processing derive primarily from two categories: loading and transportation of the uranium product and chemicals used in the processing operations; and accidents or natural disasters, or management oversight failures that impair the normal operations of the processing, tailings management, or water treatment facilities.

Ecologically significant exposures primarily involve (1) spills, leaching, and surface runoff reaching streams and other aquatic environments; and (2) uptake of dissolved chemicals by plant roots. For these pathways, the most important radionuclides and chemicals are those that are water-soluble or are adsorbed to particles that can be suspended and transported by surface runoff and streamflows.

Radiological Effects

Ionizing radiation—specifically, α, β, and γ particles released through the decay of radionuclides—causes ecological effects via damage to biological tissues in exposed organisms. The effects of radiological exposure are related to the total amount of energy deposited, expressed in units termed Gray (Gy) per unit time (the radiological dose rate). This dose rate is the sum of doses from all sources, including natural background radiation, and includes both internal and external exposures. The International Atomic Energy Agency (IAEA, 1992) proposed guideline dose rates below which effects on plant and animal populations would be unlikely. These values are 400 µGy/hr for aquatic animals and terrestrial plants and 40 µGy/hr for terrestrial animals. These same values were used by the U.S. Department of Energy (USDOE, 2002) in its guidance on evaluating radiation doses to aquatic and terrestrial biota present at USDOE facilities. These limits are intended for application to long-term average exposures. Dose limits for episodic exposures to biota have not been promulgated, however, and any such limits would be expected to be higher than limits established for long-term exposures.

Internal doses result from uptake of radionuclides principally through inhalation and ingestion. Ingestion-related pathways can include consumption of

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

BOX 6.3
Uranium Site Cleanup to Mitigate Ecological Impacts in France

Uranium mining and associated operations in the vicinity of Limousin, France, began in 1947, with numerous orebodies being discovered and mined in peraluminous leucogranites. In 1993, the discovery that sediments and aquatic plants downstream from the Puy de l’Age mine were contaminated with radioactive waste raised concerns about public health and environmental hazards in the area and led to a sustainable redevelopment by the site owner, AREVA NC (formerly Cogema). By 1998, progress had been made in site cleanup and redevelopment, but several health and environmental concerns remained, including high contamination of river sediments and the presence of radioactive mud inside the mine basin. Nevertheless, in 1999 the local administration agreed with AREVA that the radiological situation at the Puy de l’Age mine was “normal” and that further water treatment and environmental monitoring was unnecessary. The last uranium mine in the area was closed in 2001.

In 2006, French authorities—including the Ministers of Ecology, Industry, and Health, as well as the President of the Nuclear Safety Authority—commissioned the Groupe d’Expertise Pluraliste sur les sites miniers d’uranium du Limousin (GEP; [Multidisciplinary Experts Group for the Uranium Mines of Limousin]) to evaluate recent progress made in the management of former uranium mining sites in France, both at the local level in Limousin as well as at the national level. The team conducted a thorough investigation of the risks and potential impacts to human health and the environment posed by these sites, examined the options for future site management and monitoring, and recommended best practices for improving management to reduce both current and long-term impacts. The GEP’s final report was released in September 2010.

The GEP found that, although good progress has been made and should be continued in the management of former uranium mining sites, there were several key problem areas:

• Lack of an institutional body specifically responsible for directing activities at former uranium mining sites

• Lack of a timetable and specified process for transferring site-management responsibility from the company to public authorities

• Need for a systematization of site inventory and characterization tasks

• Insufficient research on and understanding of radioactive wastes on and around sites

• Limited range and scope of radiological impact evaluations

• Incompatibility of site monitoring devices with regulatory requirements

• Unreliability of existing safety systems in the long term

• Lack of information and public participation in sustainable site management

The GEP found that although current remediation measures have helped to control certain risks, there remain opportunities to increase the effectiveness of these measures in the near and long term. Their report called for the development of a strategy to integrate the technical, institutional, and social problems related to site management and the establishment of a program to address those problems. The report described a framework of recommendations based on the need for such a comprehensive program. As envisioned, the program would improve

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

research efforts on sites, reinforce information collection and sharing and dialogue among stakeholders, and guide a range of other activities undertaken by the site owner and other relevant local and national government organizations.

The GEP offered a variety of recommendations for the sustainable management of former uranium mining sites. The recommendations are divided into six major areas:

1. Institutional perspective and regulatory body: The GEP proposed the establishment of an organization that is dedicated specifically to the affairs of former uranium mining sites. It also recommended the continued development of a legal framework that is adapted to current site-related risks.

2. Research efforts to improve knowledge: The GEP recommended systematizing the characterization of sites to acquire better knowledge of potential sources of pollution. Current site characterization should be continued, but a strategic research program should also be developed to strengthen the understanding of key phenomena (hydrogeology, hydrochemistry, emission and transfer of radon, accumulation of radioactivity in the processing residues, etc.) as well as the knowledge regarding the toxicity of these substances.

3. Impact evaluations and public health policies: The GEP found that impact evaluations to date have been mostly limited to public radiological exposures. It therefore recommended further development of the dosimetric evaluation method, which offers a more reliable estimation of the radiological doses from sites to the various exposure pathways. The GEP also emphasized the need for better evaluations of chemical impacts on humans, in addition to new evaluations of both the radiological and chemical impacts on ecosystems. This would require development of new monitoring tools and additional health monitoring in affected zones, accompanied by policies to protect the public against exposure to ionizing radiation.

4. Site surveillance systems: The GEP found that devices deployed at certain sites are often incompatible with regulatory requirements. It recommended development of site surveillance systems that are better adapted to current knowledge of the potential risks and impacts related to site development. This should be accompanied by increased monitoring of the effects on local ecosystems, habitats, and the environment.

5. Robust safety systems to address long-term risks: The GEP determined that existing safety systems on certain sites are unreliable in the long term, because they function on measures—such as land-use restrictions—that may degrade over time. Stakeholders should consider technical and social issues, in addition to a broad range of scenarios, to reinforce the long-term robustness of existing safety systems. This would involve preparing and formalizing a decision-making process to implement long-term management options.

6. Information and participation in sustainable site management: The GEP found that current efforts to address the lack of information and participation in sustainable site management are inadequate. It recommended expanding efforts to collect site information and share it with the local population. Local-scale site management will require additional support from the local Commissions of Information and the creation of feedback mechanisms around the sites. The GEP emphasized the importance of maintaining a dialogue between the local and national levels to reinforce information sharing and follow up on actions.

SOURCE: GEP (2010).

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

contaminated water or food, and incidental ingestion of soil or sediment that contain radionuclides. External doses result from decay of radionuclides present in environmental media in the immediate vicinity of an organism. The amount of external radiation absorbed by an organism from a particular decay event depends on the type of radiation released (only β particles and γ rays can penetrate the skins or external membranes of organisms), the distance between the organism and the source, and the size and external geometry of the organism. An aquatic plant will receive a different external dose from the same radiation source than will an invertebrate feeding on the plant or a fish that consumes the invertebrate.

Although these exposure pathways are complex, radiation biologists have developed models to quantify them. The USDOE (2002) guidance document contains models for quantifying total dose rates for aquatic animals, riparian zone animals, terrestrial animals, and terrestrial plants. The models are radionuclide-specific, and include models for 238U and daughter products, including all of the decay chains discussed in Chapter 5 (see Figure 5-1). The guidance provides methods for using these models to calculate biota concentration guides (BCGs), which are concentrations of specific nuclides in environmental media that would produce a dose exactly equal to the recommended dose limit, considering all environmental pathways and both external and internal exposures. These BCGs can be used to identify thresholds of concern in environmental media.

Chemical Toxicity

Uranium toxicity. Under oxidizing conditions, uranium in aquatic environments is generally present in the hexavalent state (U6+), although the aqueous species will depend on a variety of factors, including pH, alkalinity, and complexing agents, such as dissolved organic matter or phosphate). The speciation and complexation affect the toxicity of uranium in the environment. The most bioavailable and toxic form present under typical environmental conditions is the divalent uranyl (UO22+) ion (Cheng et al., 2010). A wide variety of uranium toxicity studies have been performed using terrestrial plants, soil invertebrates, soil microorganisms, aquatic invertebrates, fish, and mammals. Uranium toxicity to fish is hardness-dependent (with toxicity being inversely related to hardness), although hardness does not affect the toxicity of uranium to other aquatic organisms. Sheppard et al. (2005) reviewed the toxicity literature for uranium and derived the predicted no-effect concentrations (PNECs), which are concentrations of uranium in water or soil below which no adverse effects on exposed organisms are anticipated to occur:

• Terrestrial plants, 250 mg U/kg (dry soil)

• Other soil biota, 100 mg U/kg (dry soil)

• Freshwater plants, 0.005 mg U/L

• Freshwater invertebrates, 0.005 mg U/L

• Freshwater benthos, 100 mg U/kg (dry sediment)

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

• Freshwater fish in very soft water (hardness of <10 mg CaCO3/L), 0.4 mg U/L

• Freshwater fish in soft water (hardness of 10-100 mg CaCO3/L), 2.8 mg U/L

• Freshwater fish in hard water (hardness of >100 mg CaCO3/L), 26 mg U/L

Considering all types of aquatic organisms, Mathews et al. (2009) calculated a PNEC of 3.2 µg/L (0.0032 mg/L) for freshwater ecosystems.6 The various PNEC values calculated for uranium indicate that uranium is similar in toxicity to metals such as copper and cadmium.

Some authors have suggested that chemical toxicity of uranium is usually more important than radiological toxicity, but Mathews et al. (2009) found that this is not the case for all of the exposure scenarios evaluated. Mathews et al. (2009) recommended that ecological risk assessments for uranium should consider both chemical toxicity and radiological toxicity, including the radioactivity associated with the decay of uranium daughter products.

Toxicity of other radionuclides. Chemical toxicity of uranium daughter products has not been considered a significant issue in uranium mining or processing. Thorium is of potential interest because it may occur in higher concentrations than uranium in typical uranium ores and typically occurs in higher concentrations in the waste rock and tailings. Two published studies (Correa et al., 2008; Kochhann et al., 2009) investigated the uptake and toxicity of a soluble form of thorium (thorium nitrate) to the silver catfish (Rhamdia quelen). Both studies demonstrated the uptake of thorium by fish tissue, especially the gill, and skin, and also demonstrated biochemical and histological changes resulting from thorium exposure. However, no effects on growth or survival (Correa et al., 2008), which are more ecologically relevant effects, were found, and the chemical form of thorium used in the experiments is not a form in which thorium would typically be found in the environment. Carvalho et al. (2007) found elevated concentrations of uranium, radium, and polonium in fish collected from rivers affected by historical mining operations in Portugal. Thorium was retained in riverbed sediments and was detected only at very low levels in fish. Hence, information currently available suggests that no radionuclide other than uranium is of environmental concern due to chemical toxicity.

Toxicity of nonradiological chemicals. Toxicity information for those chemicals and other water quality characteristics associated with uranium mining and processing that are most likely to be of greatest ecological significance are briefly summarized in Boxes 6.4 and 6.5. These include substances potentially present in mine water or treated effluent (e.g., dissolved salts), substances potentially

_________________

6 For comparison, reported surface water concentrations of uranium downstream of the Rum Jungle mine in Australia, which operated in the 1950s and 1960s with little concern for environmental impacts, ranged from 6 to 63 µg/L (mean of 33 µg/L) in 1992-1993 (Mudd and Patterson, 2010).

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

leached from waste rock or tailings (e.g., selenium, vanadium, nickel, copper, aluminum, iron; see Box 6.4), and chemicals potentially released during spills (e.g., sulfuric acid, sodium hydroxide, carbonate, ammonia, decanol, kerosene; see Box 6.5).

Ecological Monitoring at Uranium Mine Sites

The committee was able to locate ecological monitoring data for only a few uranium mining sites, and these data show that adverse impacts sometimes occur, but do not always occur when facilities are properly managed. At the Ranger Mine in Australia, biological monitoring has revealed no significant changes to aquatic biota or fish communities downstream from the mine, and no significant bioaccumulation of mining-related contaminants in fish or shellfish (Supervising Scientist, 2008). However, biological monitoring in Island Lake downstream from the Cluff Lake mining and processing operation in Canada showed shifts in benthic invertebrate communities to more metal-tolerant species. Moreover, bioaccumulation of uranium, selenium, and radium was observed in fish tissues (CNSC, 2003).

Selenium in particular has been identified as a contaminant of concern at two modern uranium mining and processing operations in Saskatchewan—Key Lake (Wiramanaden et al., 2010) and McClean Lake (Muscatello and Janz, 2009a). At both of these sites, selenium was found to accumulate in the tissues of aquatic biota, even though concentrations of dissolved selenium in the water column were low. The environmental transformations and transfer pathways responsible for this accumulation appear to be quite complex. Wiramanaden et al. (2010) found that selenium accumulated in benthic invertebrates in Fox Lake, downstream from the treated effluent discharge from the Key Lake Mill. The authors concluded that inorganic selenium was being adsorbed by phytoplankton in Fox Lake, settling to the bottom sediments, being converted to organic forms by microorganisms present in the sediment, and being transferred to benthic invertebrates that feed on organic detritus present in the sediment. The authors also found that the rate at which selenium is removed from the water column and transferred to sediment and biota is influenced by both water chemistry and sediment characteristics, especially sediment total organic carbon. Similarly, Muscatello and Janz (2009a) found selenium accumulation in phytoplankton, benthic invertebrates, and fish in Vulture Lake, which receives treated effluent from the McClean Lake mine site. The highest concentrations were observed in fish, although Muscatello and Janz (2009b) found no overt effects of selenium exposures on adult spawning northern pike and white sucker fish or on the eggs and larvae compared with those in a nearby uncontaminated lake.

As discussed previously in this chapter, acidic surface water and ground-water have been found at uranium sites in Brazil, Portugal, Australia, and Canada. The chemical and biological processes responsible for this acidification, and associated mobilization of toxic metals such as copper and zinc, are the same

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

BOX 6.4
Ecological Effects of Key Substances Potentially Present in Mine or Tailings Discharge

This box discusses the ecological effects of key constituents with significant ecotoxicity that are likely to be present at some level in uranium mine or tailings discharge. The concentration and exposures ultimately affect the extent of ecological effects. Acid mine drainage conditions can lead to particularly elevated concentrations of these constituents.

Many metals and metalloids are substantially more toxic to aquatic biota than to humans. Table 6.1 compares, for those constituents for which water quality criteria have been promulgated by the Virginia Department of Environmental Quality, the criteria for aquatic life protection and the criteria for drinking water. The likelihood of environmental risk from these various constituents depends on their concentration in the orebody and the host rock. For example, arsenic and selenium have been found associated with uranium at ore deposits in Canada, but they are not present in significant concentrations in the Coles Hill, Virginia, deposit. Nevertheless, arsenic and selenium may be present in other uranium ore deposits in Virginia.

Dissolved salts. High concentrations of dissolved salts can be toxic to freshwater aquatic organisms (e.g., Sarma et al., 2005). Both mine water and treated processing effluents often contain high concentrations of salts. Salinity is frequently measured in terms of electrical conductivity, and the appropriate inland freshwater conductivity has been determined to lie between 150 and 500 µsiemens/cm.

Acidity. Streams affected by acid mine drainage have degraded benthic invertebrate communities and much lower densities of fish than do streams that have not been affected (Earle and Callaghan, 1998). It is difficult to identify the specific causes of these effects because the low pH and the high concentrations of metals present at low pH are toxic to aquatic biota. Neutralization of acidic waters through mixing with unpolluted ambient water can result in precipitation of iron, aluminum, and other metals. These precipitates coat the substrate and cause additional biological degradation.

Selenium. Selenium is a potentially hazardous substance that interacts with different compounds and can behave differently depending on these interactions and environmental conditions. Selenium can accumulate and biomagnify, and exposure to high concentrations can cause reproductive failure and birth defects (USEPA, 2004; Lenntech, 2011b). The USEPA (2004) has published a draft water quality criterion of 7.91 µg/g dry weight expressed as a concentration in fish tissue.

Copper. Copper can be toxic to both aquatic biota and terrestrial plants. Reduced growth or photosynthesis in algae and teratogenic effects in sensitive species or fish amphibians have been seen in environments with copper concentrations as low as 5-10 ppb (Maag et al., 2000). The presence of copper has been shown to reduce macroinvertebrate survival as well as contribute to adverse structural and functional effects of fish nervous systems. Exposure to high concentrations

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

of copper can also cause gill tissue damage and even lead to death (USEPA, 2007).

Aluminum. Aluminum can accumulate in plants, affecting enzyme systems important for the uptake of nutrients. In addition, aluminum contamination can cause adverse health impacts to animals that consume these plants. In aquatic environments, aluminum ions react with proteins in the gills of fish and the embryos of frogs, resulting in impaired gas exchange, which can be particularly severe in low-pH waters (Dietrich and Schlatter, 1989). Aluminum contamination can also cause adverse effects on birds and other animals that eat contaminated fish and insects, such as eggshell thinning and low birth weights of chicks (Lenntech, 2011a).

Vanadium. Vanadium bioaccumulation has resulted in pervasive elevated concentrations in a variety of plant and animal species. Ecological exposures may lead to neurological and reproduction complications, breathing disorders, and liver and kidney problems (Lenntech, 2011b).

Iron. Ferric hydroxide and iron-organic matter precipitates in surface waters disturb the metabolism and osmoregulation of organisms. In addition, these precipitates change the structure and quality of benthic habitats and food resources, which decrease the species diversity and abundance. Ferric iron also lowers the pH when it hydrolizes in water (Vuori, 1995).

TABLE 6.1 Comparison Between Virginia DEQ Water Quality Criteria for Aquatic Life Protection and for Public Drinking Water

Aquatic Life (μg/L)

Freshwater

Saltwater

Chemical

Acute

Chronic

Acute

Chronic

Public Water Supply(pg/L)

Aluminuma

750

87

Arsenic

340

150

69

36

10

Cadmium

3.9

1.1

40

8.8

5

Copper

13

9.0

9.3

6.0

1,300

Lead

120

14

15

Nickel

180

20

610

Selenium

20

5.0

170

Vanadium

280

19

90

81

Zinc

120

120

7,400

aApplicable at pH 6.5-9.0.
NOTE: Dashes indicate that no criteria have been established.
SOURCE: Virginia Department of Environmental Quality Regulation 9VAC-260-140: Criteria for Surface Water.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

BOX 6.5
Ecological Effects Possible from Chemical Spills

The following chemicals used in uranium processing have the potential to affect ecological health if significant quantities are spilled:

Sulfuric acid. Sulfuric acid poses moderate acute and chronic toxicity to aquatic life. Exposure may cause superficial burns and lesions on animals. Although small quantities may be neutralized, larger amounts may affect water pH levels, causing acidic conditions. Acidic conditions may promote leaching of other compounds, such as aluminum and iron, from soils (DSEWPC, 2011).

Sodium hydroxide. Although sodium hydroxide is not directly toxic to aquatic life, large enough amounts may cause water pH to rise above the tolerance limits of some freshwater aquatic species (California EPA, 2003).

Carbonate and bicarbonate. Carbonate and bicarbonate are not inherently toxic compounds, but elevated levels may cause indirect negative effects on an aquatic system by raising water pH (Lottermoser, 2010).

Ammonia. At a low pH and temperature, ammonia combines with water to produce ammonium and a hydroxide ion, which is nontoxic. Above pH 9, unionized ammonia is predominant and can readily cross cell membranes, allowing ammonia to accumulate in organisms. Exposure to ammonia at high levels may cause increased respiratory activity and increased heart rate in fish. In addition, exposure can lead to reduction in hatching success, reduced growth and morphological development, and injury to gill tissue, liver, and kidneys. Impacts such as hyperplasia of the gill lining in salmon fingerlings and bacterial gill disease have been seen at even slightly increased levels of ammonia (0.002 mg/L for 6 weeks). Various fish species can die at concentrations of 0.2 to 2.9 mg/L, with trout being the most susceptible and carp the least (CSREES NCWQP, 1976).

Decanol. Decanol biodegrades readily and is expected to adsorb to suspended solids in water and sediment. There is a moderate potential for decanol to bioconcentrate in aquatic organisms. Decanol poses a slight to moderate toxicity to freshwater fish and a moderate toxicity to saltwater fish.

Kerosene. Kerosene spills could result in potential acute toxicity to some forms of aquatic life. The lighter, more volatile compounds of kerosene, such as benzene, toluene, and xylene, could cause long-term contamination hazards to the groundwater. The polycyclic aromatic hydrocarbon compounds in kerosene may be translocated and accumulated in plants. Chronic effects of exposure to some constituents in kerosene include changes in liver; harmful effects on kidneys, heart, lungs, and nervous system; increased rates of cancer; and immunological, reproductive, fetotoxic, and genotoxic effects (Irwin et al., 1997).

processes responsible for acid mine drainage from coal mines in the eastern United States. Biological data are not available for most of these sites. However, information on the effects of acid drainage on stream fish communities and on the recovery of fish communities following remediation is available from studies performed at the Rum Jungle uranium mine site in Australia. The Rum Jungle

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

mine released untreated mine waters into the Finniss River during the 1950s and 1960s. Biological studies performed in the 1970s showed that during low flow periods the abundance and diversity of fish and decapod crustaceans in the Finniss River immediately downstream from the discharge were substantially reduced. Significant fish kills were observed when low flows in the Finniss River coincided with moderate inflows from the mine site (Jeffree and Williams, 1980). Elevated concentrations of cobalt, nickel, copper, zinc, and manganese occurred as far as 30 km downstream from the mine site. Fish kills were associated with pulses of highly contaminated water released during the onset of the rainy season. Following remedial actions performed in the 1980s, both the average metal concentrations and the magnitudes of seasonal pulses were greatly reduced. A fish community study performed during the 1990s (Jeffree et al., 2001) showed that the fish community present in the Finniss River immediately downstream from the inflow from the mine was similar to the community present at unaffected sites. No fish kills were observed. The adverse effects observed downstream from the mining and processing operations described above have been attributed to chemical toxicity, rather than to radiological exposures. There is no evidence that radiological dose limits for aquatic or terrestrial biota were exceeded in any of these cases.

General Mining-Related Ecological Effects

Many of the sources of stress to ecological systems are not specific to uranium mining, but may be associated with any mining activities or substantial ground-clearing development. The effects of mining can be divided into on-site ecological effects from the significant disruption of the land surface in the mined area and off-site effects.

On-site Effects

The principal ecological impacts during the construction phase derive from the ground disturbance associated with excavation and construction, operational emissions from construction equipment, and increased human presence in the area. The process of constructing buildings, roads, and the site preparation will eliminate the soil habitat on the immediate footprint of all permanent site features. This loss will have long-term ecological effects in cases where woodlands or forests are removed and not restored, although it may be possible to restore grasslands following site closure. Revegetation with native plants, however, can be a challenge because of changes in soil quality and pressures from invasive species. A significant indirect impact on habitat will be the consequences of loss of shade trees. Shade trees provide both habitat for various species as well as modulation of temperature, wind, and rainfall. Shade trees also lower air and surface soil temperatures and water temperatures of adjacent streams.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×

Off-site Effects

Sediment. Construction and ground-disturbing activities often cause soil erosion and increased stormwater runoff. State and local regulations and ordinances require erosion and sediment control measures such as retention ponds, straw bales, and earthen berms, termed best management practices. These practices seldom, if ever, prevent erosion and sedimentation entirely, although the problem may be mitigated. Excess sediment is recognized as a principal cause of impairment to freshwater streams and creeks nationwide and throughout Virginia (Suren, 2000; USEPA, 2010). Replacing sand or gravel surfaces with silt and fine sediment can make the habitat unsuitable for indigenous flora and fauna. Sediment also can clog the gills of many aquatic animals, leading to impaired growth and physiological function and sometimes death. Excess sediment is also a leading cause of water quality impairment in the Chesapeake Bay and coastal North Carolina embayments into which most Virginia surface waters drain. In these coastal waters, waterborne sediment blocks sunlight and coats plant surfaces, both of which limit the ability of underwater grasses to photosynthesize, reducing growth and causing mortality. These underwater grass beds are an important habitat that has been reduced over time and are the target of significant restoration efforts (Batuik et al., 2000).

Major mining operations could require increased transportation infrastructure in Virginia, meaning more roads or improved roadways. Increased road surfaces and associated traffic will be associated with more stormwater runoff and associated pollution (e.g., nitrogen, sediment, organic chemicals, heavy metals). New roadways and railways that disturb forestland may have the consequence of bisecting and disturbing habitat.

Other chemicals. Sediment and water discharged off-site could contain a wide variety of ecologically hazardous materials, depending on the chemical composition of the ores being mined. Elevated concentrations of salts and other dissolved materials (total dissolved solids or TDS) caused by mining and processing activities can affect the health of freshwater biota. Depending on water chemistry (especially pH), a variety of metals and metalloids, including copper, iron, aluminum, vanadium, and selenium can be released in high quantities. Releases of water containing high concentrations of dissolved metals are typically associated with acid mine drainage, as discussed previously in this chapter. Discussion on specific ecological effects of these constituents is provided in Box 6.3.

ENVIRONMENTAL MONITORING

A well-designed and executed environmental monitoring plan is an essential component of any uranium mining and processing operation. In this section, the goals and key components of a monitoring program are discussed. Additionally,

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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the section discusses ways to engage stakeholders in the development and implementation of the monitoring plan.

Monitoring Goals

A monitoring strategy will need clear goals and a feasible strategy by which those goals can be achieved. The major purposes of an environmental monitoring and assessment program include:

Determining and demonstrating compliance. A monitoring program is frequently used to assess whether the facility is in compliance with environmental and worker-safety regulations. An equally important aspect is assessing the attainment of best-practice discharge targets, which may be significantly lower than regulatory limits.

Triggering corrective actions. Monitoring data can guide facility operators to implement corrective actions (e.g., improved engineering controls or management procedures) when predetermined trigger points are exceeded. A well-constructed monitoring and assessment plan can enable early detection of system failures (whether caused by natural events, human error, or criminal acts), thereby preventing more widespread contamination.

Fostering transparency. Providing timely and readily accessible information to stakeholders about measured environmental contaminant levels and doses to persons can provide assurances to the community that they are not subject to adverse impacts that are unseen and unmeasured. Thus, monitoring can foster a broadly informed local community and bridge the gap of mistrust of the regulatory process. Transparent monitoring also ensures that personal and community interests are protected during the facility operation and after closure.

Enhancing site-specific understanding. Knowledge gained through baseline and operational monitoring can be used to improve the understanding of site-specific hydrogeology and contaminant transport pathways. This knowledge can be used to refine site-specific conceptual models or validate and refine numerical models of the site, such as hydrologic, contaminant transport, and air dispersion models. Information gained from monitoring can also provide the basis for evaluating the monitoring plan itself and making improvements as needed.

Additionally, facilities may use other on-site monitoring to aid in documentation of material control and security, through material balances (see also NCRP, 2011)

In the long term, robust monitoring should also lead to better-informed operational, management, public policy, and regulatory decisions. One of the keys to any environmental and public health protection program is an environmental monitoring strategy that is designed to inform these decisions. This strategy would include (1) determinations of the types environmental measurements (e.g.,

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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biological, water, air, soil), their spatial distribution, and their temporal frequency necessary to adequately inform regulatory and operational decision making and address community concerns; (2) policy and regulatory decisions on how change in the environment will be detected, measured, and qualified; and (3) how much change from the baseline is of regulatory and operational significance.

Key Aspects of Monitoring

Monitoring occurs during all phases associated with uranium mining. A well-designed monitoring program is based on a set of agreed-upon goals, as discussed in the previous section, rather than a set of proscribed practices (e.g., number, location, and depth of wells). This monitoring program would begin well in advance of site operations (i.e., baseline monitoring) and continue during operations, reclamation, and well after closure and decommissioning.

Baseline Monitoring

Comprehensive baseline surveys of environmental characteristics are conducted prior to the start of mining and processing operations to provide an understanding of premining and processing conditions. These data are essential for comparing environmental conditions after the onset of construction and operations against background contaminant levels. Baseline data will also provide a basis for returning the land to unrestricted use after the operations cease. Finally, baseline data will be useful during emergency response for surveying contamination in the event of an unplanned release.

Baseline characterization includes, at minimum, chemical, physical, and radioactive elements of the water, air, and soil; biological indices (e.g. benthic index); habitat characterization; and identification of species or communities of special interest that could be affected by construction or facility operation. The spatial extent of baseline monitoring would need to encompass the mine site and offsite areas with potential for environmental impacts, with particular attention paid to downgradient groundwater resources and downstream water resources that could be affected by water pollutants released from the mining operations. The length and frequency of baseline monitoring would need to be sufficient to capture the natural inter- and intraannual variability. The measurements of radio-nuclides and other chemicals of concern in environmental media (i.e., air, water, vegetation, and representative fauna) should be obtained for a minimum of 1 full year, but ideally would take place over several years. The selection of measurement methods with adequate sensitivity is critical.

Ideally, a group of stakeholders would be assembled to design the baseline monitoring program. This could include managers of the facility, support staff, technical experts, regulatory officials, potentially exposed residents nearby, and public interest groups. This core group should then develop a mechanism for

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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soliciting the input of a wider and more diverse group including chemists, engineers, dose modelers, statisticians, technical project managers, community representatives, immediate neighbors, data users, public officials, and decision makers. A detailed description of the process is outlined in NCRP (2011) for reference. Based on the use of the data, the monitoring program can be designed to include the frequency, sample size, location, and parameters that are of interest.

Baseline data collection would represent one aspect of a more comprehensive site characterization effort, from which site-specific conceptual and numerical models would be generated to integrate the data collected into a system-level understanding. Conceptual models are diagrams or narrative descriptions that synthesize complex data and concepts regarding potential exposures and site-specific transport processes into an accessible format that offer an important tool for communicating with public stakeholders, regulators, and risk assessors (Suter, 1999; Cygan et al., 2006). Numerical models are mathematical tools that use equations to describe the relationships among system components and can be used to make quantitative predictions. A model (or models) developed for a uranium mining/processing project should include all significant environmental pathways linking potential sources of radionuclides and nonradiological contaminants to human and nonhuman receptors. Key pathways would likely include surface water, groundwater, and atmospheric emissions, as well as direct gamma-ray exposure. These tools would also be essential to the development of contamination response plans.

Operational Monitoring

Like the baseline data collection, operational monitoring programs (i.e., frequency, sample size, location, and parameters) ideally would be developed with substantial stakeholder input, so that the monitoring data can be used to inform decision making among various stakeholders. An operational monitoring strategy would likely continue the baseline monitoring, perhaps with altered temporal sampling as appropriate to address the decision needs of regulators, facility managers, and the public. This monitoring would be used to determine (1) failures of engineered control strategies, (2) actual or potential adverse impacts upon public health and/or the environment, or (3) breaches in regulatory requirements. The optimum time interval between sampling events would depend on the potential hazards and the remedial action options (including natural attenuation), considering contamination scenarios that could occur over the time period between sampling events.

Environmental radiation monitoring for uranium mines (whether open-pit or underground) would include three levels of monitoring. Real-time radiation monitoring (e.g., ion chambers and gamma-ray spectrometers) can provide instantaneous readings that would be relevant in an emergency. Integrated monitors assess radiation exposure over a period of time (e.g., 2 weeks), which provides a

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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greater sensitivity but no instantaneous readings. For example, thermoluminescent detectors could be installed in concentric rings around the facility to detect high levels of airborne radioactivity. Finally, a program of measurement of radiation in biota is needed to determine whether the bioaccumulation of radionuclides is occurring within the food chain (NCRP, 2011).

Regular assessments of all monitoring data, including trend analyses, are important to test the accuracy of predictions and, if necessary, to modify the mitigation and remediation practices. The determination that contamination has occurred is based on comparison of data from upgradient and downgradient wells against a comprehensive preoperation baseline. This, in conjunction with a robust statistical analysis plan, will help to determine a true contamination event from a false positive or an observation within natural variability. True exceedances would trigger the need for corrective actions. A clear process is needed for reviewing monitoring data, including an annual independent review of monitoring data, and adjudicating data discrepancies. The operational monitoring plan is best developed and updated in close cooperation with facility design and operations staff to adapt to changes in operations (e.g., relocated facilities, changes to process chemicals used).

Operational monitoring strategies need to be based upon the best available understanding of the regional hydrogeology, atmospheric conditions, and biosphere. Monitoring data and new science may improve the existing understanding of potential contaminant release or transport pathways. Thus, although initial monitoring objectives are identified for each of the chosen environmental compartments, the monitoring strategy needs to be adaptable to respond to new knowledge. To ensure that the monitoring plan and site conceptual and numerical models are appropriate and reflect the latest scientific understanding, the monitoring plan and site models should be reviewed annually by an independent group of qualified experts. Ideally, such a review panel would include experts nominated by public stakeholders and regulators. The results of the monitoring and model review, including recommendations for improvements, would be released to the public and submitted to the relevant authorities in a timely fashion.

Decommissioning Monitoring

The purpose of environmental monitoring during decommissioning is to evaluate the potential doses to members of the general public and demonstrate compliance with regulatory requirements because activities associated with site remediation can pose different environmental concerns than those encountered during operations. For instance, a uranium mill tailings impoundment that is partially covered with water during facility operation may be dewatered and dried prior to covering. This could increase the potential for radon or particulate emissions. Therefore the environmental monitoring program in place during operations would not be sufficient during decommissioning to account for this

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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situation. The Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) provides the methodology for developing a site decommissioning survey (USEPA et al., 2000). The intended use of the manual is to demonstrate that the site is sufficiently remediated to meet the decommissioning criteria. A separate document, the Multi-Agency Radiological Survey and Assessment of Materials and Equipment (MARSAME) Manual7 has been prepared to provide guidance for documentation of monitoring required before release of expensive heavy equipment (i.e., bulldozers) or transport of waste to off-site locations.

Data Quality

Guidance on data quality objectives for monitoring data are described in the Multi-Agency Radiological Laboratory Analytical Protocols (MARLAP) Manual (USEPA et al., 2004). The MARLAP Manual was prepared to address the need for a nationally consistent approach to producing radioanalytical laboratory data that meet a project’s or program’s data requirements and is considered to be the definitive guide for sampling and analysis. Data quality objectives are discussed extensively in the manual detailing the laboratory procedures for analyzing samples.

The decision about which devices to deploy, where they would be located, and how frequently samples would be taken, would be dictated by the objectives of the monitoring strategy, including the precision, accuracy, and uncertainty that are determined to be acceptable. The quality assurance project plan is the place where all of these decisions are documented so that the objectives are clear to the staff executing the monitoring plan, as well as regulatory officials and the public.

Finally, a data management plan will need to be developed to (1) ensure that all monitoring data and associated metadata are archived and (2) facilitate easy retrieval of the data and metadata by interested parties (public, regulators). A publicly accessible scientific data clearinghouse would provide transparency and common ground for public policy and regulatory debate.

Multistakeholder Environmental Monitoring Infrastructure Approach

A multistakeholder environmental monitoring strategy is an effective approach to address multiple concerns in crafting the monitoring program and to maintain trust among a diversity of stakeholders. The “first line” of monitoring could involve direct efforts by the facility operator or by monitoring performed under contract to the owner by local research institutions or private consultants. This first line of monitoring could also include separate monitoring efforts operated solely by state or federal regulatory authorities. A second line of monitoring could be managed by a local community group through a community technical assistance grant (TAG) with funds from the facility operator. Through this effort,

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7http://www.epa.gov/rpdweb00/marssim/marsame.html.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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community members, with assistance from independent scientific experts, would identify monitoring needs of particular importance and contract for sampling and analysis by infrastructure different from that of the mine operator. A third line of monitoring could involve local authorities such as cities, municipal water purveyors, or local air pollution control districts, who could identify monitoring strategies focused on their specific jurisdictions. Funding for this third line could be derived from the “mill tax” on per kilowatt of energy derived from the mined uranium. Like that for the community TAG effort, analysis of these samples would be done by laboratory entities different from that of the mine operator. All monitoring described above would need to be conducted according to quality assurance/quality control specifications determined by the relevant regulator.

FINDINGS AND KEY CONCEPTS

The committee recognizes that mining, processing, and reclamation, by nature, can cause long-term impacts to habitats (on the order of decades to centuries), hydrological alterations, and adverse changes to water quality. Virginia has extensive experience with mining and its impacts, and thus the primary focus of this chapter is on the specific environment impacts of uranium mining. The committee arrived at the following findings regarding the environmental impacts that might occur if the moratorium on uranium mining in Virginia were to be removed:

Uranium mining, processing, and reclamation in Virginia have the potential to affect surface water quality and quantity, groundwater quality and quantity, soils, air quality, and biota. The impacts of these activities in Virginia would depend on site-specific conditions, the rigor of the monitoring program established to provide early warning of contaminant migration, and the efforts to mitigate and control potential impacts. A substantial literature exists that describes the environmental hazards resulting from past uranium mining that was largely conducted using standards of practice generally not acceptable today. Documented impacts include water quality effects (e.g., elevated concentrations of trace metals, arsenic, and uranium) caused by acid mine drainage or oxidation of groundwater, localized reduction of groundwater levels, off-site dust transport, and impaired populations of aquatic and terrestrial biota. If uranium mining, processing, and reclamation are designed, constructed, operated, and monitored according to modern international best practices (see Chapter 8), the committee anticipates that the near- to moderate-term environmental effects specific to uranium mining and processing should be substantially reduced. Nevertheless, studies at relatively modern uranium mines have documented acid mine drainage associated with waste rock piles and effects on aquatic biota from selenium and metals derived from treated effluent.

Tailings disposal sites represent potential sources of contamination for thousands of years, and the long-term risks remain poorly defined. In recent

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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years, significant improvements have been made to tailings management practices to isolate mine waste from the environment, and belowgrade disposal practices have been developed specifically to address concerns regarding tailings dam failures. However, the short period of monitoring data at these sites provides insufficient information from which the committee can judge the long-term (200- to 1,000-year) effectiveness of modern uranium tailings management facilities in preventing groundwater and surface water contamination. The potential long-term environmental effects posed by uranium mining and processing waste (e.g., wide-spread groundwater and surface water contamination) are likely to be more than trivial if waste management facilities fail to perform as designed. Major failures would necessitate aggressive remediation strategies and possibly long-term active site management to limit off-site migration and restore the affected area.

Significant potential environmental risks are associated with extreme natural events and failures in management practices. Extreme natural events (e.g., hurricanes, earthquakes, intense rainfall events, drought) have the potential to lead to the release of contaminants if facilities are not designed and constructed to withstand such events, or fail to perform as designed. The failure of a tailings facility is one example of a design failure that could have widespread human health and environmental effects. Extreme weather events are not rare in Virginia, and need to be carefully and appropriately considered in facility design, management, and maintenance. Management issues or human error, as well as criminal acts such as intentional release, could lead to large-scale environmental contamination by hazardous materials or radionuclides used or stored on-site. The empowerment of all regulatory and mine- and processing-site staff to report and address deficiencies can reduce such occurrences or minimize their impacts. Thoughtful environmental monitoring design can also lead to early detection of contamination caused by management failures, thereby lessening the extent of any offsite remediation that might be required. Until comprehensive site-specific risk and vulnerability assessments are conducted, including accident and failure analyses, the short-term risks associated with natural disasters, accidents, and spills remain poorly defined.

Models and comprehensive site characterization are important for estimating the potential environmental effects associated with a specific uranium mine and processing facility. A thorough site characterization, supplemented by air quality and hydrological modeling, is essential for estimating the potential environmental impacts of uranium mining and processing under site-specific conditions and mitigation practices. Ongoing water and air quality monitoring are necessary to confirm model predictions and provide the basis for updating and revising these models as additional site-specific data become available.

Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
×
Page 221
Suggested Citation:"6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation." National Research Council. 2012. Uranium Mining in Virginia: Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia. Washington, DC: The National Academies Press. doi: 10.17226/13266.
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Page 222
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Uranium mining in the Commonwealth of Virginia has been prohibited since 1982 by a state moratorium, although approval for restricted uranium exploration in the state was granted in 2007. Uranium Mining in Virginia examines the scientific, technical, environmental, human health and safety, and regulatory aspects of uranium mining, milling, and processing as they relate to the Commonwealth of Virginia for the purpose of assisting the Commonwealth to determine whether uranium mining, milling, and processing can be undertaken in a manner that safeguards the environment, natural and historic resources, agricultural lands, and the health and well-being of its citizens. According to this report, if Virginia lifts its moratorium, there are "steep hurdles to be surmounted" before mining and processing could take place within a regulatory setting that appropriately protects workers, the public, and the environment, especially given that the state has no experience regulating mining and processing of the radioactive element. The authoring committee was not asked to recommend whether uranium mining should be permitted, or to consider the potential benefits to the state were uranium mining to be pursued. It also was not asked to compare the relative risks of uranium mining to the mining of other fuels such as coal. This book will be of interest to decision makers at the state and local level, the energy industry, and concerned citizens.

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