DOE/WIPP-95-2129 @ON'- 9'6 0 7LI- - 1

UNDERGROUND MINING AND DEEP GEOLOGIC DISPOSAL - TWO COMPATIBLE AND COMPLEMENTARY ACTIVITIES

N. T. REMPE WIPP - Westinghouse Electric Corporation, NM, USA

ABSTRACT

The belief that deep geologic waste repositories should ideally or only be located in areas with low potential for mineral resource exploration and production warrants critical scrutiny. Current guidance on the subject by the U. S. Environmental Protection Agency seems to contradict its own early research .

Active and mature underground mining districts offer conditions quite favorable to deep geologic disposal because (a) their geology is known in more detail than that of most virgin ground; (b) the technical and environmental feasibility of underground excavations has already been demonstrated; (c) mining leaves distinctive footprints and records that alert subsequent generations to the anthropogenic alterations of the underground environment; and (d) subsequent exploration and production proceeds with great care and accuracy to locate and generally to avoid old mine workings.

The compatibility of mining with deep geologic waste disposal has been proven by decades of experience with safe storage and disposal in former mines and in the mined-out areas of still active mining operations. Mineral extraction above, below, iri, and around an intended repository before decommissioning reduces, if not eliminates, the incentive for hture disturbance, intentional or not. Incidental features of mineral exploration and extraction such as lost circulation zones, allochthonous backfill, and permanent surface markers can likewise deter fbture intrusion into a repository. Thus, the exploration for and production of mineral resources should be considered eminently compatible with, and indeed complementary to, deep geologic waste disposal.

1. INTRODUCTION .Y

A superstition is growing among regulators and operators of prospective deep geologic repositories. It finds its perhaps strongest expression in proscriptions issued by the United States Environmental Protection Agency (EPA) [l], but other countries appear poised to succumb to the same spell [2]. Succinctly stated, this superstition amounts to the belief that the selection process for deep geologic repository sites should avoid areas containing identified or inferred mineral resources. Underlying that belief is the fear that the presence of natural resources a) increases the risk of inadvertent human intrusion into' a decommissioned repository and therefore b) decreases the probability permanent

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This mixture of fear and superstition surrounding repositories that are still under development contrasts sharply with the theory and practice of repositories that are already serving their intended purpose. Operating facilities for deep geologic disposal of ecotoxic waste in Germany, the country with the most extensive experience in the field, use active and inactive underground mines without exception. The principal, non-negotiable aspect of any mine is, of course, the presence of natural resources in economic concentrations and quantities. Therefore, the country that Pioneered the disciuline and the technolow of deeo geologic disuosal has already demonstrated that the presence of and the underground minins for mineral resources are eminentlv compatible with and complementary to such disposal. Ironically, about two decades ago, the EPA concurred with that assessment [3], a quite sensible attitude which the same agency ignores completely in a recent regulatory interpretation [4].

This discussion therefore presents arguments in support of not only the peacefbl coexistence but, indeed, the symbiotic relationship between deep mining and disposal, and of the continued validity of the early EPA assessment.

2. THE MINING AND DISPOSAL CYCLE

Deep geologic disposal is the logical conclusion of the sequence of activities ranging from mining through refining, use, and recycling. Just as nature returns all matter to its origin through the hydrologic and rock cycles, so does deep geologic disposal return matter to the ground whence it came. Disposal by man has the advantage over nature by being highly localized, planned, and organized. Storage in or near the biosphere provides only a short-term solution. Matter in direct contact with the atmosphere and hydrosphere remains easily susceptible to mobilization and transportation. Fairly rapid and random disposal into, and contamination of, the biosphere are almost inevitable.

Contrast the short material cycles in atmosphere, hydrosphere, and pedosphere (soil) with the very long material cycles in the deeper lithosphere. That is why wastes with high and long-term ecotoxic potential need to be placed in underground repositories in suitable (deep and dry) formations. These formations are subject to the very slow material cycles that provide long-term, for all practical purposes permanent, isolation from the biosphere [5 ] . Mined openings in such formations can therefore provide excellent disposal space.

3. U.S. DISPOSAL CAPACITY NEEDS

Relying on EPA estimates, the Hazardous Materials Control Resources Institute reports that the U.S. generates some 150 million tons of hazardous waste each year. More than 75 percent is treated, less than 2 percent is incinerated, and less than 1 percent is recycled. The remaining 20-odd percent or 30 million tons ends up in landfills or is disposed of by similar methods that, for the most part, do not ensure permanent isolation. "Poor containment, flooding, leaching, or other disturbances can allow substances once labeled "disposed" to become new or different disposal problems ... Our current methods of storing hazardous wastes

must include the possibility that fences will not keep out vandals, that liners will not prevent leaching, and that containers or treatment systems will fail or perform badly." [6]

Chemotoxic hazardous waste is only one of several waste categories in need of safe, permanent disposal. The U.S. Department of Energy (DOE) has estimated [7] that it alone is responsible for the final disposition of radioactive and mixed (radiotoxic and chemotoxic) waste to the tune of

0.75 million m3 stored waste 3.1 1 -100

million m3 buried waste, and million m3 cleanup waste.

The amount of cleanup waste to be generated during the remediation of contaminated DOE sites will depend on the cleanup levels demanded by regulatory standards, which in turn may be based on the final use of the remediated sites.

4. GERMANY - THE PRACTICAL EXAMPLE

Excerpts from a presentation in late 1994 to the U.S. National Academy of Sciences [SI offer a glimpse at the current practice of deep geologic disposal in Germany:

a) Since 1972, Germany has disposed of more than 12 million t of non-radioactive hazardous wastes in underground mines. Operating and depleted salt and potash mines are preferred sites. These non-radioactive waste repositories are privately owned and operated and are licensed by their respective state (not federal) authorities.

b) The first and largest repository, part of the largest German potash mine, has disposed of more than 1.5 million t of chemotoxic waste since 1972. Shaft dimensions limit current emplacement capacity to 180 000 to 200 000 t/a, while available underground space in this mine alone would permit disposal of 5-8 million t/a.

c) Total underground space available in active and inactive German mines amounts to 300 million m3, of which 140 million m3 could be used in the near fiture. That volume grows by 25 million m3/a, with the largest share being contributed by salt and potash mines.

d) Germany expects 740 000 t/a of hazardous wastes to be generated by the year 2000. 400 000 t of those wastes will be residues from domestic rehse incinerators.

e) In contrast to the prescriptive disposal standards applied in the U.S., the German regulatory fiamework employs a more risk-based

strategy. That approach attempts to identify the optimum balance between environmental and economic risk, benefit, and cost.

German authorities had already decided in the 1960s to dispose of all types of radioactive wastes in deep geologic formations. West Germany launched the practice with experimental emplacement in the Asse former salt mine between 1967 and 1978. The late East German government then operated a repository in the Morsleben former salt mine from 1978 until 1990. The unified Germany resumed operations at Morsleben in 1994. Disposal will continue at least until 2000, when a new license is required for either hrther operation or decommissioning [9].

5. FACETS OF MINING CONDUCIVE TO DISPOSAL

In excess of half a century of cumulative experience with deep geologic disposal in operating and idle mines supports an already strong case for the safety and success of the practice. Active and mature underground mining districts offer conditions quite favorable to waste disposal and permanent isolation for a variety of reasons [lo]:

a) Geology and resource potential are usually known in far more detail in a mining district than in virgin territory.

Technical and environmental feasibility of excavating underground space have already been proven.

Exploration and development use far greater care in a developed and mature mining district than in untested ground.

Mine planning and design can make disposal an integral part of the multiple - use concept.

Mining leaves distinctive records and footprints.

Mining, in conjunction with deep geologic disposal, can incorporate appropriate measures to deter or prevent inadvertent human intrusion.

Assertions a) through c) are self-evident, but arguments d) through f> need additional justification:

Most geologic waste repositories, two exceptions being the Swedish and Finnish installations, use underground space not originally intended for disposal. That purpose was an afterthought, i.e., serendipity has so far been the primary selection factor. Incorporating the secondary use of mined excavations into the earliest mine planning will undoubtedly result in even better assurance and safety for hture repositories.

Indications of mining activities have been preserved for centuries and even millennia [lo]. Even in the absence of specific markers designed to inform and warn future generations, mining itself invariably leaves distinct signatures such as tailing piles, mine portals, and surface infrastructure. Concealed evidence of previous mining, such as an unexpected loss-of-circulation zone, further reduces the chances for inadvertent disturbance. On the whole, traces left by mining either act as disincentives to later efforts, or they cause special precautions to be taken.

Emplacing an appropriate allochthonous backfill in mined openings above a repository could reduce or prevent inadvertent disturbance ofthe disposed waste underneath. We can minimize the chances for intrusion even further by exact superposition of mine and repository patterns.

None of these individual factors guarantees absolute, long-term, undisturbed isolation, but in combination they give a clear advantage to a resource-rich candidate area over an unknown.

6. BENEFITS OF DISPOSAL TO MINING

Owners of mined underground space benefit from deep geologic waste disposal in several ways. Waste used as backfill can support the roof, increase the general stability of underground workings, and minimize eventual surface subsidence. A good example is the Kochendorfsalt mine in southwestern Germany. Mining at shallow depth (ca. 180 m), under only thin salt cover, resulted in a host of problems that required frequent, sophisticated, and expensive remedial measures. In one instance, it took two years (1986 to 1988) to seal a water inflow [ 111. Other concerns included 43 roof falls of various dimensions in four years [ 121. To prevent firther deterioration and to ensure long-term stability, the regional mining authority ordered the entire mine, 12 million m3, to be backfilled. Expert consultants advised the company on the design of a pilot project which demonstrated that:

a) flue gas scrubber residues from domestic refbse incinerators can attain the desired rock mechanical properties, and

b) properly selected transportation and emplacement techniques will not compromise employee safety.

More than two years of pilot experience proved the feasibility, environmental compatibility, and safety of the waste backfill technology. The company is now engaged in fill-scale disposal while at the same time investigating additional waste forms for their suitability as backfill.

Underground mines also benefit from financial compensation in the form of disposal fees charged per unit of weight or volume of waste. Fees at the Herfa repository for highly toxic chemical waste in central Germany, for example, increased from DM 123/t in 1972 to DM 440 ($315)/t in 1993. Although competition for low- to moderate toxicity waste has depressed disposal fees for those categories in recent years, disposal operations have become a steady source of moderate profits for several German mines [13].

7. UNDERGROUND DISPOSAL IN U.S. MINES

Deep geologic disposal in the U.S. is bogged down in a morass of regulations proliferating out of control, of know-nothing opposition coupled with deliberate obstructionism, and of capricious interpretation of frequently inconsistent and contradictory rules by regulators and courts. The only bright spot in that gloomy picture is the DOE'S Waste Isolation Pilot Plant (WIPP). The WIPP is a specifically excavated repository - not a former or current mine - for radioactive waste, located in thick salt beds near Carlsbad, New Mexico. This facility has been technically ready since late 1988 to receive waste. Current plans envision the first waste to arrive almost ten years late, in 1997 or 1998.

Commercial U.S. facilities analogous to those already operating in Germany are still only gleams in the eyes of tenacious promoters [14]. Successful commercial deep geologic disposal in the U.S. hinges to a large extent on the record of the WIPP. Whether that is a blessing or a curse remains to be seen.

In contrast to the situation in Germany, the U.S. has no current estimate of its inventory of mined underground space available for waste dispo,sal. But some candidates come readily to mind. The continental U.S. contains a wealth of salt and potash mines, active and abandoned. Upon close inspection, some of them are bound to qualifjr. But even if that were not the case, new panels and new mines, e.g., Retsof, could be designed for deep disposal as their integral secondary function. If deep geologic disposal in mines can succeed in a small, densely populated country - half the size of Texas, with one-quarter the population of the U.S. - then it can certainly become reality in the U.S.

8. CONCLUSION

Regulatory prejudice notwithstanding, underground mining and deep geologic waste disposal are two very compatible and complementary activities. Apparent conflicts dissolve upon closer examination, to be replaced by mutual benefit and support. Theoretical arguments west of the Atlantic are bolstered by reference to decades of practical experience under less favorable conditions east of it. The often heard assertion that mining is intrinsically harmful to the environment [15] is flat wrong. To the contrary, a proper symbiosis between underground mining and deep geologic waste disposal not only solves our surface disposal problems, but also improves our environment and enhances the life, health, and safety of this and future generations.

REFFXENCES

U.S. EPA (Environmental Protecti n Agency), 'I 40 CFR (Code f Federal Regulations) Part 191: Environmental Standards for the Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes; Final Rule", Federal Register, Vol. 50, No. 182,38066-38089, 1985.

GRIMWOOD, P.D., and SMITH, G. M., "Human Intrusion: Issues Concerning its Assessment", in: Risks Associated with Human Intrusion at Radioactive Waste Disposal Sites, Proceedings of an NEA Workshop, Paris, June 5 -7, Nuclear Energy Agency, Organization for Economic Co- operation and Development, 21-30, 1989.

STONE, R.B., AAMODT, P.L., ENGLER, M.R., AND MADDEN, P., "Evaluation of Hazardous Waste Emplacement in Mined Openings", EPA- 600/2-75-040, December 1975, U.S. Environmental Protection Agency, Cincinnati, OH, 1975.

U.S. EPA (Environmental Protection Agency), "40 CFR (Code of Federal Regulations) Part 194: Criteria for the Certification and Re-Certification of the Waste Isolation Pilot Plant's Compliance with the 40 # CFR Part 191 Disposal Regulations", Federal Register, Vol. 61, No. 28, 5224-5245, 1996.

BRASSER, T., BREWITZ W., et al., "Aspekte der untertaegigen Ablagerung von Abfaellen (Aspects of Underground Waste Disposal)", Erich Schmidt Verlag, Berlin, 1991.

MARTIN, E.J., "The Issues of Emotional Fears and Technical Reality - Incineration Works", Proc. Waste Management '95, Tucson, AZ, 1995.

U.S. DOE (Department ofEnergy), Closing: the Circle on the Sditting: of the Atom, DOEEM-0266, Office of Environmental Management, Washington, DC, January 1996.

ROETHEMEYER, H., BRENNECKE, P., KRAUS, W., AND MAGER, D., "An Overview of the Waste Disposal Situation in Europe and of Uranium Mine and Mill Remediation Activities in Germany", Academy of SciencesDJational Research Council's Committee on Environmental Management Technologies (CEMT) on 6 December 1994, Washington, D.C., 1994.

REWE, N.T., "Deep Geological Disposal in Germany-Models for Mixed Waste Disposal in the U.S.", Proc. Third Biennial Mixed Waste Symposium, Baltimore, MD, 11.6.1 - 11.6.10, 1995.

[lo] MMPE, N.T., "Checking Our Premises for Reducing the Risk of Inadvertent Human Intrusion", Proc. Waste Management '95, Tucson, AZ, 1995.

[ 1 11 BOHNENBERGER, G., " E r f h n g e n mit der Deponie und dem Versatz von Reststoffen in den Salzbergwerken Heilbronn und Kochendorf (Experience with the repository and the backfilling of residues in the Heilbronn and Kochendorf salt mines)", in: Deponietechnik, Entsorgungsbergbau und Altlastensanierung, HENGERER & WOEBER, eds., Bakema, Rotterdam, 18 -190, 1994.

[ 121 HEINTZE, P., "Sicherungsmassnahmen im Steinsalzbergwerk Kochendorf (Remedial measures in the Kochendorf salt mine)", Heitkamp-Mitteilungen (service company newsletter), 1995.

[ 131 REMPE, N.T., "Waste Disposal in Underground Mines - A Technology Partnership to Protect the Environment", Preprint No. 96-43, Society of Mining, Metallurgy, and Exploration, Inc., Littleton, COY 1996.

[ 141 F"DERBURK, R., "Salt Formations Offer Disposal Alternative", Hazmat World, June 1990.

[ 151 CROWDER, A.A., RIPLEY, E.A., and REDMAFIN, RE., "Environmental Effects of Mining,", St. Lucie Press, Delray Beach, Florida, 1995 (announcement flyer).

Processing and final preparation of this report was performed by the Waste Isolation Pilot Plant Management and Operating Contractor for the U.S. Department of Energy under Contract No. DE-AC04-86AL3 1950.

D0En;VlPP-95-2 129

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom- mendation, or favoring by the United States Government or any agency thereof. The Views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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