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Environmental regulation of the mining sector has been presented with several unique challenges. Some are inherent in the nature of the activity: the need to extract large quantities of material from the earth, and to recover the desired product, often present at relatively low concentrations, in a rich enough form that it is economical to transport. Other challenges are rooted in the regulatory framework itself, and in the political context in which it has evolved.
Two themes in particular may be found threading through this analysis. The first is the impact of quantity, rather than intensity, on overall risk. The second is a somewhat unexpected lesson that attempts to deal with mining wastes may provide for the way we deal with industrial wastes in general.
Environmental impacts and risks
Quantitative impact data
Effects of existing and future regulations on impacts
The U.S. Census Bureau's 1997 Economic Census for the mining sector distinguishes three major subcategories of mining under NAICS code 212, tabulated below together with a few selected measures of their relative sizes:
|2122||Metal ore mining||$11,204,250,000||493||45,467|
|2123||Nonmetallic mineral mining and quarrying||$16,621,381,000||5,344||95,887|
Facilities within each of these subcategories carry out operations which are conveniently classified into three levels:
This analysis will concentrate on the first two types of operation, since extraction and on-site beneficiation include aspects unique to the mining sector, while manufacturing operations, even when they occur near the mine site, would appear to have more in common with general manufacturing facilities regardless of location. (Additional analyses for the cement and for the iron and steel sectors cover aspects of the downstream manufacturing operations in those particular subsectors.)
There are three basic extraction methods:
After the ore containing the desired material has been brought to the surface, it is generally necessary to separate the wanted from the unwanted constituents, and to create a more uniformly sized material for subsequent processing. Such operations, collectively referred to as beneficiation, are often carried out near the extraction point, to minimize transport of low-value materials.
Beneficiation processes primarily directed toward resizing include:
Beneficiation processes carried out with the object of removing impurities or concentrating desired material include:
The scheme presented above is intended to provide a convenient framework for evaluating environmental impact. It should be noted that "beneficiation" is defined in the Code of Federal Regulations (40 CFR 261.4) using somewhat different nomenclature and categorization. The purpose of the CFR definition is to exclude specifically certain types of solid waste from being classified as hazardous wastes. As such, it probably is more indicative of a process of negotiation than of analysis. However, the list of beneficiation processes called out in 40 CFR 261.4 is reproduced in the section on regulation below because of its regulatory significance.
The mining sector is served by numerous trade organizations, some general in purpose and membership, and many specific to materials or geographical regions. A sampling includes:
Seventeen states have formed an organization of their own, the Interstate Mining Compact Commission, to represent "the natural resource interests of its member states".
As far as the impacts of extraction are concerned, surface mining is inherently more disruptive than underground mining, since it involves not only the displacement of the ore body itself, but of the entire overburden as well. The effects of underground mining can be further mitigated by returning waste rock to the mine. In isolated cases, subsidence of mined out areas can create serious surface impacts. But in general the environmental impacts of underground mining are secondary effects of material removed from the mine, rather than effects of the mining operation itself. (Health and safety considerations for mine workers are, of course, another matter.)
In contrast, the impacts of beneficiation processes are conditioned more by the material properties of the desired product than by the geological properties of the ore body and its surroundings.
Many metals are high-value materials present in their ores at relatively low concentrations. Large quantities of ore may be processed near the mine site, generating commensurately large quantities of waste (tailings). Metal ions are soluble in acid, and many beneficiation processes for metallic ores involve leaching by acidic solutions. Disposal of spent leaching solutions after metal ion recovery may present wastewater problems.
Non-metals, such as quarried stone, limestone, sand and similar materials may be more directly usable as extracted. Materials separation is less of an issue, but sizing may be important. The impact of grinding and sorting operations carried out in these types of materials is more likely to be associated with air quality (airborne particulates) than with solid waste (tailings piles).
Beneficiation of coal is advantageous in producing a higher value and cleaner burning product, but the benefits on the consumption end must be weighed against the impacts associated with the beneficiation process.
Wet processes in general, even those without chemical additives such as washing, may also be associated with environmental impacts involving the discharge of wastewater. Solvent extraction processes may present even more difficult challenges in minimizing the release or disposal of spent solvents.
General Environmental Impacts
Air emissions data for certain key criteria pollutants (ozone precursors) are available from the National Emission Trends (NET) database (1999), and hazardous air pollutant emissions data are available from the National Toxics Inventory (NTI) database (1996 is the most recent year for which final data are available). For the SIC codes 10xx (Metal mining) and 12xx (Coal mining), the total emissions for volatile organic compounds (VOC), nitrogen oxides (NOx) and hazardous air pollutants (HAPs) are as follows (in tons per year):
|1031||Lead And Zinc Ores||10||3||2|
|1061||Ferroalloy Ores Except Vanadium||80||9||2|
|1099||Metal Ores Nec||147||442||11|
|Total, all metal mining subsectors||2,109||45,341||1,959|
|1211||Bituminous Coal And Lignite(1977)||283||1,855|
|1221||Bituminous Coal & Lignite - Surface||1,065||1,588||22|
|1222||Bituminous Coal & Lignite - Underground||720||1,007||0|
|1241||Coal Mining Services||92||247|
|Total, all coal mining subsectors||2,160||4,700||22|
These quantities are, for the most part, relatively small, in comparison with the more significant of the manufacturing sectors. The excess HAP over VOC quantities reported for gold ores is presumably due to cyanide. The high NOx value for iron ore is presumably due to process heat requirements. Downstream manufacturing processes involving iron ore (blast furnaces and steel mills) have NOx emissions about three times the size of the contribution of the mining sector.
Starting with the 1998 reporting year, the metal and coal mining sectors became for the first time responsible for supplying Toxics Release Inventory data. Data from 1999 are available.
Not surprisingly, the total of on-site land releases for the metal mining sector towers above that of all other sectors combined. The following figures appear in the 1999 TRI Executive Summary:
On site land releases
|All SIC 20-39 industries||20,698||323,667,851|
|Metal mining (SIC 10)||108||3,394,845,946|
|Coal mining (SIC 12)||50||9,608,323|
The smaller figure for coal mining presumably reflects the greater proportion of product to waste extracted from coal deposits over metallic ores.
The number of active mine facilities reporting TRI data should not be taken to be historically representative of the industry. An EPA report has estimated that there are about 200,000 abandoned mine sites in the United States. Because mining necessarily involves disturbing previously stable formations, and may involve exposing large quantities of material to weathering processes, the environmental effects of mining activities can continue long after operations have ceased.
While the quantity of solid waste generated by mining operations is huge, much of the waste poses little direct risk from a toxicity standpoint. There are significant exceptions, such as high levels of arsenic and lead in some ores, cyanide discharges from gold beneficiation processes, and radionuclide emissions from uranium often found in the vicinity of copper deposits. There are also indirect effects, such as acid runoff. But apart from these exceptional cases, typical mining waste is relatively benign in terms of the standard hazardous waste characteristics.
On the other hand, the effects of quantity itself poses risks peculiar to the sector. Acid runoff and wind-blown dust from large piles can pose widespread risk of adverse health effects and land and water resource degradation. Large piles often involve large water impoundments, which can be unstable, causing disastrous flooding. And the need for large scale land restoration, always an imperfect process, can lead to significant habitat destruction.
Regulation of active surface mines (as well as remediation of abandoned mines) is primarily the responsibility of the Office of Surface Mining, in the Department of Interior, in partnership with the states. Regulation of the environmental consequences of mining activities, such as the effects of surface water runoff and the designation of Superfund sites, can still fall under the purview of the EPA.
In 1980, mining wastes were excluded by an act of Congress from RCRA Subtitle C regulations. Some observations on the implications of this unique approach to the regulation of an industry sector are set forth below.
Effluent Limit Guidelines (ELG) applicable to the sector include:
Amendments to the effluent limit guidelines and new source performance standards for coal mining were proposed in 2002.
A major rulemaking effort (termed the "3908 rules", after 40 CFR 3908) was undertaken in 1997, and published in November 2000. The new rules were to go into effect on the final day of the Clinton administration, but they have since been suspended by the Bush administration. The new rules would have several environmental consequences, including extension of liability to parent corporations, application of cyanide leaching and acid mine drainage regulations to surface mining, and creation of new outcome-based performance standards. The industry has mounted a vigorous challenge to these rules.
A visitor from Mars might be forgiven for being bewildered by the framework that the nation has evolved for environmental regulation of the solid waste generated by the mining sector. After all, the amount of waste material generated by mining activities dwarfs that of any other industrial sector. Depending on the nature of the ore being mined and the characteristics of the deposit, waste can constitute anywhere from ten percent to 99.99 percent of the material extracted from the earth. Much of it is returned, and much of the disturbed land is restored. But much remains all too visible, and all too problematic.
This fact alone would seem to invite robust regulatory supervision. Instead the mining sector is, from an environmental standpoint, the least regulated of any comparable industry sector. This is no chance oversight, but is the result of specific legislation (the Bevill Amendment of 1980) exempting the mining sector from the solid waste rules under which most manufacturing enterprises in the U. S. must operate.
In developing its initial response to the exclusion of mining wastes from RCRA (in a Regulatory Determination published in 1986), the EPA acknowledged that the sheer quantity of mining wastes renders application of the RCRA rules problematic. (This may call to mind the old observation that if you owe ten thousand dollars, the bank owns you, but if you owe ten million, you own the bank.) The agency has since revisited the question in a document, Risks Posed by Bevill Wastes, published in 1998. The document examines in detail a large number of risks posed by wastes generated under the Bevill exemption. They range from runoff from piles and acid mine drainage through collapse of clay ponds created during phosphate mining.
The greatest wonder for our extraterrestrial observer might be that, with no one watching the store, the environmental impact of solid waste from mining is not worse than it is. There are several mitigating factors. First, although mining wastes are excluded from regulation under RCRA, water runoff from the wastes still falls under provisions of the NPDES system. Mine sites can still be declared Superfund sites under CERCLA. Mines that impact wetlands (including many phosphate mines) are still subject to regulation by the Army Corps of Engineers. And mine operators are mindful of potential liability from non-regulatory directions, including damage awards, citizen environmental lawsuits, unfavorable publicity, and the rest of the panoply of non-regulatory motivators.
The Bevill Amendment and its consequences provides an interesting test case highlighting how regulation proceeds in the absence of statutory authority for the use of one of its standard tools, and how non-regulatory factors come into play when regulation is partially fettered. But it may also be instructive to turn the matter around and ask if this situation tells us anything about some possible inherent limitations built into the framework of assumptions within which RCRA was devised.
The original goal of RCRA was primarily to keep the increasing volumes of wastes being generated by the nation's manufacturers from becoming human health and environmental problems. The mechanism used was to separate waste generation from waste disposal, and to regulate the latter more strictly. Manufacturers could still generate waste with little restriction (other than increased compliance costs), as long as they disposed of it properly. Waste designated as "hazardous" had to be treated under special rules. Since a small quantity of hazardous material was sufficient to cause a large quantity of waste that included it to be deemed "hazardous", and since generators could not treat waste on site (including separating out the hazardous fraction) without coming under the stricter rules, the framework created a substantial volume of waste, much of it posing a relatively low degree of environmental risk, that had to be treated as hazardous. The net result was to concentrate the continually increasing mass of waste into fewer and larger piles, and to breathe life into a service sector devoted to the transportation of waste from the generator to the landfill.
In its 1986 Regulatory Determination in response to the Bevill amendment, the EPA recognized that imposing the RCRA regime on mining wastes, even if their potential to cause environmental degradation was every bit a great as comparable manufacturing wastes, was impractical. The specter of convoys of trucks or railcars hauling huge waste piles from one hole in the ground to another was sufficiently absurd to justify putting mining wastes into a special category.
But we are on a slippery slope. Exactly what is it that differentiates mining waste from manufacturing waste and qualifies it for an exemption? Is it sheer quantity? Then at what point would a manufacturing waste become sufficiently voluminous to qualify for an exemption of its own? Does this give a large manufacturer an incentive to create a big enough waste pile to become exempt from RCRA rules? Surely quantity should entail more regulatory constraints, not fewer. Are some mining wastes less hazardous than manufacturing wastes? Then they can qualify for delisting under the same rules as any other waste -- no special exemption is necessary.
One way to resolve the question would be simply to charge the exclusion of mining wastes up to politics, and to consider it the exception that proves the rule. All the problems that now beset the environment downgradient of mining activities simply underscore how valuable RCRA, with all its flaws, has been in regulating how the nation has dealt with its manufacturing wastes for the past quarter century.
Yet this may not satisfy our Martian visitor, who is presumably less attuned to, and perhaps less sympathetic to, our political and short-term economic constraints. If moving a waste pile from one hole to another makes no sense for mining wastes, why does it make more sense for manufacturing wastes? The idea of RCRA is to get wastes out of the way, and into a safe repository. Yet this is at best a stopgap measure. Eventually, as the scale of industrial activity increases, moving manufacturing wastes to landfills will come to seem as futile as moving mining wastes seems now. To be sure, we have come a long way since RCRA was enacted in 1976. The advantages of pollution prevention are clearly understood, and industry is increasingly putting pollution prevention measures into practice. The national waste pile is not growing nearly as fast as it would be otherwise. But it is still growing.
So perhaps our Martian might be forgiven for coming up with a radical suggestion: Take a lesson from the mining wastes situation. The problem with "Bevill wastes" would not be solved by subjecting mining wastes to RCRA. Doing so would in fact compound the problem. The problem with mining wastes needs to be solved at the mine site. Perhaps the same is true with manufacturing wastes. RCRA avoids problems by separating the responsibility for generating wastes from the responsibility for dealing with them. But that may be shortsighted. Perhaps we need to get better at dealing with wastes at the point where they are produced. Suppose that manufacturers were responsible for dealing with waste on site -- that they were in fact discouraged from being able to offload the problem. That might, for one thing, be the single greatest incentive to pollution prevention yet devised. Yes, it would require every manufacturer to develop many of the same capabilities that we now require of treatment, storage, and disposal facilities, at least as far as their particular wastes are concerned. But perhaps, in the long view, an environmentally rational manufacturing system needs that capacity built into every manufacturing facility. Cleanup is part of the job.
The beneficiation processes specifically called out in 40 CFR 261.4 whose waste products are to be excluded from classification as hazardous waste are:
calcining to remove water and/or carbon dioxide
autoclaving and/or chlorination
in preparation for leaching (except where the roasting (and/or autoclaving
and/or chlorination)/leaching sequence produces a final or intermediate
product that does not undergo further beneficiation or processing)
US Economic Census Data, mining sector, 1997 http://www.census.gov/prod/ec97/97n21-gs.pdf
TRI data, 1999 http://www.epa.gov/tri/tri99/index.htm
EPA-OECA has created sector notebooks for:
Bevill amendmentOther documents of interest from EPA :