Technischer Bericht NTB 14-02/VII

SGT Etappe 2: Vorschlag weiter zu untersuchender geologischer Standortgebiete mit zugehörigen Standortarealen für die OberflächenanlageGeologische GrundlagenDossier VII:Nutzungskonflikte

Dossier VII: Conflicts of use

Dossier VII on conflicts of use discusses whether resources that are commercially exploitable either from a present-day viewpoint or in the foreseeable future (e.g. salt, hydrocarbons, coal), mineral and thermal water sources, geothermal resources, raw materials for the construction industry, ores, etc. occur within, above or below the host rock and to what extent conflicts of use could arise.

A conflict arises when the use of resources is made more difficult or impossible by a deep geological repository (including its underground access structures) or when there is a significant likelihood of unintentional human intrusion into the repository. Whether the exploitation and use of raw materials could have an adverse effect on the barrier function of the effective containment zone (host rock and confining units) is also discussed; this could occur either through direct penetration into the effective containment zone or the repository itself by exploratory boreholes or indirectly due to induced movement along faults (subsidence of the bedrock, induced seismicity).

With the decision of the Federal Council of 30th November 2011 to adopt the siting regions proposed by Nagra in Stage 1 into the Sectoral Plan process, it was also decided that the Cantons would be responsible for checking, in the case of drilling permits or concessions, whether the proposed activities could present a risk to the barrier function of the effective containment zone. These checks are based on documentation provided by ENSI and a report prepared by Nagra with maps showing protection zones.

Potential conflicts of use within, and in the close vicinity of, the geological siting regions were analysed for the raw materials and types of usage mentioned above. The results are summarised below.

  • Hydrocarbons, coal: Potential conflicts of use in terms of mining and conveying of fossil hydrocarbon resources (natural gas, oil) and coal are complex in nature. They relate to exploration, conveying methods and the consequences of the mining activities.

No deposits of fossil raw materials are known in the four host rocks proposed in Stage 1 of the Sectoral Plan process and none of them has the potential for exploitation of shale gas.

Evaluation of the possible occurrence of raw materials beneath the host rock shows that only the Zürich Nordost siting region shows no potential for fossil raw resources over large areas. There is a potential for natural gas in the tight rocks of the Permo-Carboniferous (so-called tight gas plays) in the whole of the Jura Ost siting region. The same applies for the Nördlich Lägern siting region; the north-western boundary of this region also lies in an area with other potential types of deposit but these are outside the disposal perimeter. There is a speculative potential for natural gas in the tight gas plays of the Permo-Carboniferous in the Jura-Südfuss and Südranden regions, as well as coalbed methane in the carboniferous coals. The data on the deep underground (> 2 km) in the Wellenberg siting region are insufficient to allow the potential for natural resources to be assessed. However, because deep boreholes would be drilled from the valley floor there are no indications that there would be a conflict of use.

The volumes of potential energy resources based on hydrocarbons and coal are considerable, but costly exploration work would be necessary to demonstrate this potential and its economic significance.

With regard to exploration of the largely speculative hydrocarbon and coal reserves, no concrete conflicts of interest are expected because of the small footprint of a geological repository. Exploratory boreholes could be drilled outside the potential disposal perimeters (with appropriate safety distances) without any significant loss of relevant information. A repository would not be adversely affected by geophysical exploration campaigns such as reflection seismics and gravimetric surveys, although appropriate safety distances should be observed.

  • Salt: The information on salt deposits in Northern Switzerland was updated for Stage 2 of the Sectoral Plan process. Rock salt is mined exclusively by the leaching extraction process using boreholes. The salt deposits in the vicinity of the siting regions are generally so deep that they do not come into question for commercial exploitation today, or there are indications that they are very small or even completely absent. Salt extraction would only come into question in the very northern and western parts of the Jura Ost siting region if future boreholes indicated a commercially viable thickness of the deposits. However, these areas would lie clearly outside the HLW and L/ILW disposal perimeters.
  • Stone and earth, ores: The collective term stone and earth (also 'inorganic non-ores') includes various non-metallic mineral raw materials such as stone and earth mined for the building industry. For commercial reasons, these materials are extracted only close to the surface, mostly through open-pit mining and rarely in near-surface caverns. Potential adverse effects on a deep geological repository would be conceivable if extensive, deep extraction of mineral resources were to take place directly above the disposal perimeter. This would lead to decompaction of the rock and a corresponding increase in the hydraulic conductivity of the effective containment zone.

In recent years, there has been a public debate in the Jura Ost siting region regarding a large-scale limestone/marl quarrying project. In the extreme case, this project would have reached dimensions that could have had an influence on the definition of the disposal perimeter. However, plans for the project have been withdrawn, meaning that there are presently no such concrete projects for the Jura Ost region. In the meantime, the protection zones for deep geological repositories have also been defined.

Commercial extraction of ores in the geological siting regions is thus considered to be unlikely.

  • Mineral and thermal waters: Mineral and thermal water resources are exploited at several locations in Northern Switzerland and in neighbouring southern Germany. The groundwaters typically originate from deep flow systems and it therefore has to be considered whether the accesses to the deep repository (host rock) would influence these uses. Because of the very low hydraulic conductivity of the host rock, any influence from structures in the host rock itself can be ruled out.

Use of mineral and thermal waters could be influenced during the phase of constructing or operating the accesses to the repository if a hydraulic connection is established between these uses and the areas passed through by the repository access infrastructure. Extensive investigations carried out by Nagra over many years have provided a wealth of information on the flow conditions of deep groundwaters; this knowledge provides the basis for evaluating potential conflicts of use associated with mineral and thermal waters.

In most cases, an influence of the underground access structures on mineral and thermal waters can be ruled out because the relevant hydrogeological units mostly lie beneath the Opalinus Clay and are not passed through. Considered overall, there is only one case where an influence from the underground access structures cannot be completely ruled out, namely the thermal water borehole (artesian outflow) at Lottstetten-Nack (Germany) which has a small delivery into a well. In this case, appropriate preventive and monitoring measures would have to be taken when passing through the Malm aquifer if the underground access structures are constructed in the Südranden and Zürich Nordost siting regions.

There are no uses of mineral or thermal waters in the Wellenberg siting region and its surroundings.

  • Geothermal energy (particularly deep uses): Potential conflicts of use with respect to deep geothermal energy sources depend to a large extent on the type of use (hydrothermal, petrothermal), the geological target structures and target depth and the technology being used (type of stimulation).

The sites for geothermal installations listed by the Swiss Association for Geothermal Energy indicate that there are presently no direct conflicts of use between existing and currently planned geothermal projects and a deep geological repository.

A potential target area for future deep hydrothermal installations is the peripheral faults of the Northern Swiss Permo-Carboniferous Trough. These peripheral faults were deliberately avoided when defining the disposal perimeters in the siting regions and boundary zones of the Trough reactivated after the Palaeozoic were designated as tectonic zones to be avoided for several reasons, i.e. there are no disposal perimeters directly above such geothermal target areas. In the siting regions Zürich Nordost, Nördlich Lägern and Jura Ost, the disposal perimeters are partly bounded by fault zones at the Trough periphery.

If a geothermal project were to be initiated in peripheral fault zones of the Trough in the future, a safety distance would have to be respected in these areas and monitoring programmes put in place to rule out any adverse effects on the repository due to induced movements along faults and seismic activity.

According to a recent assessment by a group of experts, petrothermal systems are the most promising option in terms of successful long-term development of Swiss geothermal resources. However, due to existing technical problems, development of these systems is not yet sufficiently advanced to make them viable on the market.

In contrast to hydrothermal systems, petrothermal systems use large-scale heat anomalies deep underground and can be set up practically anywhere. For this reason, there are many opportunities to avoid potential conflicts of use with geological repository projects.

  • Natural gas storage: Research into storage possibilities in the wider surroundings of the geological siting regions proposed by Nagra has not identified any formations that would be suitable for large-scale storage of natural gas.
  • CO2 storage: A recent study by the Swiss Federal Office of Energy (SFOE) shows that most of the siting regions in Northern Switzerland lie outside zones that are potentially suitable for CO2 storage. The Jura-Südfuss siting region is the only one that is located at the edge of the zone designated as suitable in the SFOE study. However, because a geological repository has only a small footprint, the authors of the study consider the potential for conflict of use in this case to be negligible.