Uranium Mining in Virginia Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia (2012) / Chapter Skim
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6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation
6 Potential Environmental Effects of Uranium Mining, Processing, and Reclamation
Pages 178-222
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From page 178... ...
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 according to modern best practices.
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From page 179... ...
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 analy ses of impacts on surface water, groundwater, soil, and air and the ecological effects of these impacts.
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From page 180... ...
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)
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From page 181... ...
, and both solid and liquid tailings from processing operations. Considering Virginia's relatively wet cli mate, surface water would provide a principal vector for the off-site transport of contaminants.
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From page 182... ...
of liquid tailings wastes were discharged to a nearby river, and the solid tailings proved highly erodible during wet-season rain events. A reha bilitation 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.
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From page 183... ...
(2011) reported that following decommissioning, average concentrations of manganese, fluoride, uranium, zinc, and sulfate at several monitoring stations exceeded surface water quality standards.
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From page 184... ...
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.
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From page 185... ...
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 strat egies 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.
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From page 186... ...
Mine discharges into the Puerco River were subsequently treated with a flocculant 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 wastewater treatment prior to any release off-site.
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From page 187... ...
. 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.
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From page 188... ...
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)
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From page 189... ...
. As shown at Elliot Lake and elsewhere, lined and capped storage repositories can prevent the spread of tailings by erosion and control contamination of groundwater and surface water systems from seepage (Peacey et al., 2002; Abdelouas, 2006)
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From page 190... ...
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.
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From page 191... ...
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.
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From page 192... ...
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)
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From page 193... ...
General Mining Effects Land disturbance by modern surface mining activities would be expected to increase the concentrations and loads of many dissolved and suspended nonradioactive 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.
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From page 194... ...
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.
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From page 195... ...
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)
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From page 196... ...
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 composi tion that reflects the composition of the host rock through geochemical reactions.
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From page 197... ...
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.
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From page 198... ...
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.
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From page 199... ...
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)
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From page 200... ...
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 contami
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From page 201... ...
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.
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From page 202... ...
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)
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From page 203... ...
. 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.
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From page 204... ...
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.
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From page 205... ...
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)
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From page 206... ...
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.
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From page 207... ...
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.
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From page 208... ...
The USDOE (2002) guidance document contains models for quantifying total dose rates for aquatic animals, riparian zone animals, terrestrial animals, and terrestrial plants.
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From page 209... ...
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)
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From page 210... ...
As discussed previously in this chapter, acidic surface water and groundwater 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
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From page 211... ...
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.
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From page 212... ...
Iron. Ferric hydroxide and iron–organic matter precipitates in surface waters disturb the metabolism and osmoregulation of organisms.
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From page 213... ...
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.
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From page 214... ...
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.
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From page 215... ...
Sedi ment also can clog the gills of many aquatic animals, leading to impaired growth and physiological function and sometimes death. Excess sediment is also a lead ing cause of water quality impairment in the Chesapeake Bay and coastal North Carolina embayments into which most Virginia surface waters drain.
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From page 216... ...
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.
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From page 217... ...
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.
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From page 218... ...
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.
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From page 219... ...
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.
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From page 220... ...
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.
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From page 221... ...
, the commit tee 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.
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From page 222... ...
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., widespread groundwater and surface water contamination)
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