Rare Earth Elements: A Review of Production, Processing ...

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Rare Earth Elements Review Section 3 – Life-Cycle Stages of Rare Earth Elements Mines mining method needed to obtain adequate quantities of the ore; the processing steps required (see Section 4); and the volumes of wastes that must be managed. The location of both hardrock and placer deposits in the conterminous United States and Alaska was discussed in Section 2, along with the more common REE-minerals (i.e., bastnasite and monazite). The REE-containing minerals in a hardrock or placer deposit may or may not be viable for mining due to various reasons, including economic, technical, and environmental reasons, stemming from the concentration of the REE-bearing minerals in the host rock. The definition of an “ore” for the purposes of this document is as follows: “. . . a mineral source from which a valuable commodity (e.g., metal) is recovered. The term ore implies economic viability, given the concentration of metal in the host rock, the costs of extraction, processing and refinement, waste management, site restoration, and the market value of the metal” (U.S. EPA, 2008). As the definition implies, the potential environmental impacts from all stages of a mine must be considered in evaluating the feasibility of the mine start-up—including the costs of mine restoration—to determine if a REE deposit represents an ore from which REOs and then REMs can be recovered economically. 3.3 Mine Permitting and Life-Cycle Four life-cycle stages of a mine are generally recognized. These life-cycle stages include exploration, mine development, ore extraction and processing, and mine closure. Additional steps or phases are also incorporated within each stage. The activities associated with each stage can be considered as generally linear, but overlap is common. The time needed to complete each of the steps for mine startup depends on many factors and can potentially require many years before the mine is in full production. 3.3.1 Permitting Requirements for New Rare Earth Mines A discussion of applicable mining regulatory policy and permitting requirements developed to manage the environmental impacts from mining operations is beyond the scope of this document. A detailed summary of applicable federal regulations can be found in the agency document EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska (January 2003: http://yosemite.epa.gov/R10/WATER.NSF/840a5de5d0a8d1418825650f00715a27/e4ba15715e97ef21882 56d2c00783a8e/$FILE/Maintext.pdf). In general, projects with potential to have significant environmental impact are regulated under federal or state permitting programs. Mines developed near tribal lands require consultation with tribal leadership, especially if the mining activity or associated operations could impact the community or subsistence resources. As mentioned, mining operations on the scale that would be expected for recovery of REE minerals would potentially require large areas to accommodate an individual mine and its associated support facilities (e.g., waste material management areas and tailings ponds). This need for large areas of land often means that the land occupied by a mine is of mixed ownership and includes a combination of federal and private lands (National Academy of Sciences, 1999). If a mining project is located on, adjacent to, or requires access and egress through federally managed lands, or has planned discharges to surface waters, then the permitting process is implemented under Section 102 of the National Environmental Policy Act (NEPA) [42 U.S.C. 4321 et seq.]. The life-cycle paradigm is typically used in the development of environmental impact statements (EIS) under NEPA for assessing the environmental impacts of a proposed mining activity on federal lands and this perspective will generally serve to frame the following discussion, which describes the mining life-cycle. The NEPA 3-4
Rare Earth Elements Review Section 3 – Life-Cycle Stages of Rare Earth Elements Mines process is not described in detail within this document, but can be found in EPA’s Hardrock Mining Source Book (2003). For general reference, known REE deposits that are located on or near federally managed lands are presented in Figure 2-2 and are tabulated in Appendix B. States may also apply a NEPA-type process for permitting mining operations located within their boundaries, regardless of whether the mine property is located on federally managed lands. 3.3.2 Mining Life Cycle Whether the environmental impact evaluation is performed under NEPA, state agencies, or through due diligence by the mining company, four life-cycle stages of the mine are generally recognized. These lifecycle stages are exploration, development (includes development planning, permitting, and construction), ore extraction and processing, and mine closure (includes shutdown, reclamation, and long-term monitoring). There are a number of steps that can be included within each of these mining stages that are briefly described below. However, the remainder of this section generally discusses the mining life-cycle stages, focusing on exploration and development phases and then ore extraction (i.e., mining) activities to remove rock or unconsolidated or semi-consolidated sediments (i.e., placers) containing the REE-mineral ores. Processing of REE-mineral ores and associated wastes is discussed in Section 4. It is important to recognize that there are not specific starting or ending points, or limitations, for these associated activities. Mining stages at a particular site can be cyclic and recur as mining operations progress. Exploration activities, for example, initially occur to evaluate the economic feasibility of the deposit, but then in-mine exploration generally continues once mining commences. Exploration activities may continue for less than a year, or may extend over a several years at a site until the economic viability of the deposit is determined. Once mining is underway, exploration work may progress beyond the mine, or in a near-mine area, to trace the extension and continuity of the ore deposit as the ore body is exposed during the mine advance. Reclamation activities are another example of how some mining operations are recurring during the life of the mine. These activities are also very site-specific and occur at various scales at the same site. Although areas of impact and the mass of earth materials resulting from exploration activities that require management are small in comparison to subsequent mine stages, some reclamation is often needed. Reclamation activities may be completed at the end of the exploration activity; occur intermittently as long-term exploration or mine advance continues; may not occur until mining is completed; or be initiated only after mining activities have ceased. While the mining life-cycle is commonly discussed as definitive stages of activities inferring a linear temporal scale encompassing the life span of the mine, the previous examples illustrate how activities may occur and recur as phases or be on-going operations during the life of a mine. It is also important to understand that activities to prove a deposit or develop a mine may respond to external drivers, and that an active mine may stop operations for short or extended periods. Intermittent operations may be in response to seasonal conditions when the mine site is inaccessible due to weather extremes, or mine production may exceed the capacity of the processors to accept ore feed stock. Temporary stops in work (long and short term) may occur due to economic fluctuation in the price of the commodity, engineering failures associated with the mine or equipment, or technological issues (e.g., difficulty in controlling ground water infiltration; encountering complex geologic structure such as faults; and excessive depth of deposit). If mining activities are suspended, the permits and leases are often maintained in anticipation of resuming activities and operations at a later time. Mine sites generally close and are reclaimed only if pressured by the local community (e.g., due to poor safety or environmental record), the ore body has been exhausted, or if, due to technological issues, mining is no longer possible. 3-5
Page 1 and 2: EPA 600/R-12/572 | December 2012 |
Page 3 and 4: Foreword The U.S. Environmental Pro
Page 5 and 6: Abstract Rare earth elements (REEs)
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