Major accident prevention: In brief

Handling hazardous substances or organisms entails the risk of major accidents. Today, safety and control measures greatly reduce the risk of accidents occurring in the vicinity of establishments with a major accident potential. However, as a result of settlement development around establishments with a major accident potential, the risks are likely to rise again. An updated planning guide shows how this development can be counteracted with good coordination between spatial planning and accident prevention.

1. Hazard potential on roads, railways and pipeline installations and in industrial plants (drivers) 

According to the Major Accidents Ordinance (MAO), the possible originators of major chemical or biological accidents are the following:

  • establishments that handle large quantities of dangerous chemical substances or carry out dangerous activities involving organisms.
  • transport routes (rail, road and shipping) on which hazardous goods are transported.
  • high-pressure natural gas and oil pipelines (since April 2013).

According to the latest survey conducted in 2021, 1,094 establishments, around 12,200km of transport routes (1,700km of railways, 10,500km of roads, 11km of the Rhine shipping route) and 2,142km of high-pressure gas pipelines and 165km of oil pipelines are subject to the Major Accidents Ordinance.

While the number of establishments is declining, the figures for transport routes and pipelines have remained stable in recent years. The facilities in question are distributed throughout Switzerland but are mainly concentrated in the industrial areas around Geneva, Basel, Zurich and in the Central Plateau.

Settlements will continue to expand and, more importantly, densify in the future. Road and rail traffic will also increase. Consequently, more people may potentially be affected by major accidents.

2. Major chemical and biological accidents (pressures)

Major chemical accidents can occur in facilities in which large quantities of dangerous substances, preparations or hazardous waste are handled. For example, Visp in the canton of Valais was convulsed by the explosion of a large storage tank on 22 February 2004.

Major biological accidents can occur during the course of activities involving medium- to high-risk pathogens. If such pathogens are released and spread beyond the premises in question, they could constitute a serious threat to the population and the environment. Although there have been several mishaps and incidents in recent years, no major accident has occurred in a biotechnology facility to date.

Major accidents involving dangerous goods can also occur on transport routes such as roads, railways or pipeline installations, for example during the transport of flammable solvents, acids, alkalis or pressure-liquefied toxic gases. For instance, a tank wagon containing 25,000 litres of heating oil overturned on the N4 motorway near Risch in the canton of Zug on 6 June 2001: 7,500 litres of oil were spilled, part of which reached Lake Zug.

3. Potential risks, frequency and extent of major accidents (state)

Scenarios can be used to identify the facilities that are likely to cause serious damage in the event of a major accident. The authorities responsible for implementing the MAO require the owners of such facilities to conduct a quantitative risk assessment using scenarios to determine the probability of a major accident occurring and the possible consequences.

A total of 147 facilities were obliged to conduct and update a risk assessment in 2021. The facilities concerned were primarily the following:

  • chemicals wholesalers
  • facilities that produce chemical preparations, and
  • large public facilities (swimming pools and artificial ice skating rinks).

The risk associated with the transport by rail of hazardous goods has fallen overall since 2014. This is particularly true of the transport of chlorine, where a coordinated approach adopted by all stakeholders has been successful (see Dossier ‘Measures for better security in transporting chlorine’).

No sections of the railway network pose an unacceptable level of risk to the population. Risks in relation to groundwater or surface waters have been identified for 34km of railway line in total, but these have yet to be assessed in greater detail.

The situation regarding the risks of transporting hazardous goods by road changed very little between the surveys in 2017 and 2021. The risk to the population was found to be unacceptable on 8km of the national road network, and on 5km of roads under cantonal supervision.

The almost 11km section of the Rhine on which hazardous goods are transported does not present an unacceptable risk to the population. Regarding the environment, there are no measures that could be taken to eliminate the remaining unacceptable risk that would not involve disproportionate expenditure.

For gas and oil pipelines, the owners submitted their risk reports – known as 'screenings' – for assessment up until April 2018. The initial assessment of pipeline installations will be completed in 2022.

4. Serious consequences for human beings and the environment (impact)

If human beings or the environment are affected by a major accident involving dangerous substances or goods, this can lead to fatalities or injury and to serious damage to surface waters and groundwater. Corrosive and volatile chemicals, for example, can cause serious damage to the airways.

If human beings or the environment are affected by a major accident involving dangerous organisms, this can lead to diseases or even the death of humans, animals or plants. Such dangerous organisms include, for example, tuberculosis pathogens and anthrax bacteria, the bird flu virus, and the foot-and-mouth viruses which pose a severe threat to ungulates.

5. Personal responsibility of owners, control of personal responsibility by the authorities, and spatial planning (responses) 

The owners of facilities that are subject to the Major Accidents Ordinance are obliged to undertake all necessary safety measures as a matter of personal responsibility. These measures must

  • reduce the potential risk
  • prevent major accidents
  • and limit the impact of major accidents outside the company premises or on and near the transport route or pipeline system.

The authorities monitor compliance with this duty of precaution.

Examples of safety measures implemented to prevent major accidents include:

  • retention devices for liquids that pose a threat to water (if released during a major accident)
  • detectors for the measurement of concentrations of toxic gases and
  • the coordination of company and communal fire-fighting services.

Construction activity and changes to zoning plans can have considerable impacts on the population density in the vicinity of a plant or facility that is subject to the Major Accidents Ordinance and lead to an unintentional increase in risk. A planning guide for the authorities, updated in 2022, shows how settlement development can be ensured while taking public safety into account. The basis for this is the revised article in the Major Accidents Ordinance on the coordination of spatially effective activities with major accident prevention, which has been in force since November 2018. Since 2016, the risks associated with the transport of chlorine gas by rail have been significantly reduced due to a joint declaration by the industry, railway companies and the federal government. Further implementation steps are planned until 2025.

In the case of high-pressure gas and oil pipelines for which the likelihood of a major accident is not considered to be sufficiently low, those responsible must draw up a detailed risk report evaluating the additional safety measures required to reduce the risks to an acceptable level.

Internationally, Switzerland maintains an exchange with the relevant experts from the EU and the OECD in the area of major accident prevention. It has agreed to prevent industrial accidents with transboundary effects, lower the risks and minimise their consequences through the Convention on the Transboundary Effects of Industrial Accidents of the UN Economic Commission for Europe (UNECE).

Further information

Last modification 30.11.2018

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