CHAPTER 2 Need and potential for underground disposal – survey of underground mines in Europe D. Kaliampakos1, A. Mavropoulos2 & M. Menegaki1 1School of Mining & Metallurgical Engineering, National Technical University of Athens, Greece. 2EPEM, Greece. Abstract This chapter considers the need as well as potential for disposal of hazardous waste in underground mines and provides a comparison between surface and under- ground hazardous waste disposal including typical costs. A survey on underground mines in Europe is provided including some that are currently used or considered for disposal of hazardous waste in the future. The survey shows that the number of deep mines that are suitable for disposal of hazardous waste is large in Europe, especially considering that a certain number of currently used mines are expected to cease their operation in the near future. In particular, 15 EU countries are included in this survey: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Portugal, Spain, Sweden, Netherlands and UK. This does not mean that the number of suitable mines in other European coun- tries is negligible, but it only indicates that at this moment there is no sufficient data to report. It is expected that the number of suitable underground mines for hazardous waste disposal in Eastern European countries would be quite high, which offers an alternative and affordable way of dealing with hazardous waste in these countries. 2.1 Surface vs. underground hazardous waste disposal facilities Underground hazardous waste disposal facilities present some significant advan- tages compared to the respective surface installations, which can be summarized WIT Transactions on State of the Art in Science and Engineering, Vol 26, © 2006 WIT Press www.witpress.com, ISSN 1755-8336 (on-line) doi:10.2495/978-1-85312-750-2/02 34 DISPOSAL OF HAZARDOUS WASTE IN UNDERGROUND MINES as follows [1]: • Underground facilities take advantage of the protection, isolation and security of the site. Proper design and geological siting can provide very low pro- babilities of hazardous substances leakage and of any such leakage to the sur- face environment. • Underground structures are naturally protected from severe weather (hurri- canes, tornadoes, thunderstorms, and other natural phenomena). Underground structures can also resist structural damage due to floodwaters, although spe- cial isolation provisions are necessary to prevent flooding of the structure itself. Moreover, underground structures have several intrinsic advantages in resisting earthquake motions and they tend to be less affected by surface seismic waves than surface structures [2]. • An underground hazardous waste disposal facility eliminates substantially the visual impacts, which can be of major concern in a surface structure adjacent to residential areas. • Environmental monitoring is limited mainly to air quality within the working area. Other needs for monitoring (e.g. groundwater quality) can be deter- mined during risk assessment. • Long-term and after-care monitoring are usually not necessary since the main protection is provided by the geologic medium. On the contrary, in a surface hazardous waste disposal facility the protection measures have limited life- time. Thus the landfill should be always monitored for possible leaks, even after the end of operation. • During the operation of a surface hazardous waste disposal facility, the main cost drivers are monitoring, wastewater treatment and financial insurance. According to the above-mentioned characteristics of the underground space, operational cost is expected to be cheaper in the case of underground hazard- ous waste disposal. • Moreover, in the case of an existing underground space, as it is an abandoned underground mine, there are some additional benefits that strengthen hazard- ous waste underground disposal, with the most important being the land cost and construction savings. A more detailed comparison between surface and underground hazardous waste disposal facilities is given in Tables 2.1 and 2.2, while in Table 2.3 an indi- cative sealing cost for a surface installation, as well as the respective cost for an underground hazardous waste disposal facility are presented. It should be noted that with the use of the techniques selected for the Low- RiskDT Project, the difference between surface and underground disposal of hazardous waste would increase. 2.2 Survey of underground mines in Europe The economic growth that has been observed in all developed European coun- tries since the industrial revolution relied largely on mining activity. This activity WIT Transactions on State of the Art in Science and Engineering, Vol 26, © 2006 WIT Press www.witpress.com, ISSN 1755-8336 (on-line) W w w I T w Table 2.1: General and construction issues in surface vs. underground hazardous waste disposal facilities. T . w r a i t n p s r a Surface HW disposal facility Underground HW disposal facility e c s t s i . o c n o s m General issues o , n I StateoftheArtinScienceandEngineering, Vol26, S Availability of space Limited Hundreds of abandoned underground mines S N may be suitable. 1755-8336 (on-line) Sitting Very difficult due to technical and Easier social issues. N Licensing Difficult Depends on country. EED AND Construction issues 5 m artificial geological barrier or Necessary Not necessary, the use of artificial barriers is P equivalent barrier (99/31 EC) limited and it depends on risk assessment. OTENTIAL FOR below the waste body Leachate collection Necessary, because rainfall creates huge Not necessary if water does not enter the system (LCS) quantities of polluted leachate. Normally waste body. A kind of LCS should be LCS constitutes of extended piping and constructed for potential leaks. U NDERGROUND © drainage layer. 2006 WITPress Wastewater treatment Necessary. Treatment level depends on Most of the time, negligible or no wastewater local conditions and potential impacts is generated. Safe storage of wastewater and at water tables and most of the times transfer to wastewater treatment D should be a third level one. facilities is an indicated solution. ISPOSAL Storm water management Necessary, one of the basic components Depends on the underground mine of design and construction. conditions – may also be negligible. 35 36 Table 2.2: Operational and cost issues in surface vs. underground hazardous waste disposal facilities. D W w w I ISPOSAL OF T w Surface HW disposal facility Underground HW disposal facility T . w r a i t n p s r a Operational issues e c s t s i . o c Stability Crucial point for the waste body formulation. Crucial point for the underground space. n o s H m o , Environmental impacts of High impacts to water and ground/soil. Limited or no impacts to water and ground/soil AZARDOUS n I StateoftheArtinScienceandEngineering, Vol26, S S possible major accidents Toxic gases emissions are considered system. Toxic gases emissions may create N 1755-8336 (on-line) (SEVESO) as a high level hazard. problems to workers. Environmental monitoring Extended monitoring is necessary, especially Monitoring is limited to air quality, within the for water and air quality. The sensitivity working area. Risk assessment determines other W ASTE IN of the surrounding ecosystem and natural needs for monitoring. resources determines more specific areas U that should be monitored. NDERGROUND In situ treatment options Easier More difficult due to space limitations. Long-term–after-care All the protection measures have limited The main protection is provided by the use of monitoring life-time, thus the landfill should be always underground space – the deeper the better. monitored for possible leaks, even after the After-care monitoring is not necessary. M end of operation. INES © 2006 WITPress Cost issues Construction cost Artificial barriers, wastewater treatment, The components may be the same, but they will leachate collection system, gas collection probably be cheaper due to limited water entry and treatment system, storm water and utilization of already available space. management and excavations are the main components. Operational cost Monitoring, wastewater treatment and financial It is expected to be cheaper. insurance, are the main cost drivers. NEED AND POTENTIAL FOR UNDERGROUND DISPOSAL 37 Table 2.3: Typical sealing cost in surface and underground hazardous waste disposal facilities. Cost per Thickness unit Cost per 2 (m) Quantity Unit (euros) m (euros) Bottom layer for surface installations Clay barrier (hydraulic 5 8.5 m3 10 85 conductivity < 10–9 m/s) Geotextile – 1 m2 2 2 HDPE geomembrane 0.002 1 m2 6 6 (hydraulic conductivity < 10–9 m/s) Geotextile – 1 m2 2 2 Drainage layer 0.5 0.5 m3 5 2.5 Total cost 97.5 Sealing for underground facilities HDPE geomembrane 0.002 1 m2 15 15 Shotcrete 0.1 1 m2 32 32 Total cost 47 was reflected in a large number of mining exploitations, many of which were underground mines. However, the decline of the mining industry during the last decades has led to the closure of many mining sites throughout most European countries. As a result, there are many abandoned underground mines which most of the times remain inactive and practically useless. In addition, due to the continuous decline of the mining industry, a large proportion of the remaining underground mines are expected to cease their operation in the near future [3, 4]. These mines could also be considered as potential disposal sites. A profile of the mining activity has been formulated for all the 15 EU coun- tries [5]. The profile consists of some general data concerning mining activities, active mines and mineral production, active and inactive mines etc. Special emphasis has been given to identify the underground mines in order to look for more details. More than 70 underground mines were registered and their main characteristics were recorded. Most mines are located in Germany, Sweden, Finland, and the UK, as expected due to the intense mining activity in these countries (Fig. 2.1). In addition, an inventory of inactive underground mines, presently used as waste disposal sites, has been carried out.