Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 178
Uranium Mining in Virginia 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.
OCR for page 179
Uranium Mining in Virginia • 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
OCR for page 180
Uranium Mining in Virginia 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.
OCR for page 181
Uranium Mining in Virginia 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
OCR for page 182
Uranium Mining in Virginia 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
OCR for page 183
Uranium Mining in Virginia 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).
OCR for page 184
Uranium Mining in Virginia 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
OCR for page 185
Uranium Mining in Virginia 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
OCR for page 186
Uranium Mining in Virginia 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. _________________ 1 See http://www.bape.gouv.qc.ca/sections/archives/oka/docdeposes/documdeposes/DB86.pdf.
OCR for page 187
Uranium Mining in Virginia 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
OCR for page 188
Uranium Mining in Virginia 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
OCR for page 212
Uranium Mining in Virginia centrations 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 Aqualic Lifeug/D Freshwater Saltwater Acute Chronic Public Water Supply(ngZL) Chemical Acule Chronic Acule Chronic Aluminuma 750 87 â€” â€” â€” Arsenic 340 150 69 36 in Cadmium 3.9 1.1 40 8.8 5 Copper 13 9.0 9.3 6.0 1,300 Lead 120 1- â€” â€” 15 Nickel 180 20 â€” â€” 610 Selenium 20 5.0 â€” â€” 170 Vanadium 280 19 90 81 â€” Zinc 120 120 â€” â€” 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.
OCR for page 213
Uranium Mining in Virginia 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
OCR for page 214
Uranium Mining in Virginia 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.
OCR for page 215
Uranium Mining in Virginia 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,
OCR for page 216
Uranium Mining in Virginia 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.,
OCR for page 217
Uranium Mining in Virginia 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
OCR for page 218
Uranium Mining in Virginia 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
OCR for page 219
Uranium Mining in Virginia 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
OCR for page 220
Uranium Mining in Virginia 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, _________________ 7 http://www.epa.gov/rpdweb00/marssim/marsame.html.
OCR for page 221
Uranium Mining in Virginia 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
OCR for page 222
Uranium Mining in Virginia 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.