Is your company subject to OPAM?
A company is subject to OPAM when the maximum quantity of a substance, preparation or special waste present on its premises exceeds the quantity threshold set by the Federal Office for the Environment (FOEN).
The maximum quantity adds up all possible partial quantities, according to production steps and capacities. A substance kept on site for more than 24 hours at least once a month counts as stored.
As soon as a threshold is exceeded, the holder must submit a short report to the cantonal authority.
- The substance inventory and classification
- The calculation of maximum quantities
- The comparison with FOEN quantity thresholds
- Exceptions (fuels, heating oil, etc.)
- The consequences for your project or building permit
Four steps, from threshold to decision.
Threshold check
Substance inventory, maximum quantities and comparison with FOEN thresholds.
Short report
Description of the site and of the worst-case scenarios, according to FOEN guidance. Only passive protection measures are taken into account. We model the consequences and estimate the major accident index.
Risk study
If serious damage cannot be ruled out: isolatable sections, leak sizes, failure frequencies, bow-tie analysis, site weather data and day and night population.
Assessment and measures
Cumulative curve compared with the assessment criteria, then risk reduction measures until an acceptable level is reached following the ALARP principle.
When is a risk study required?
The short report estimates the extent of damage for each scenario and converts it into a major accident index. From an index of 0.3, the damage is considered serious under OPAM and a risk study must be carried out.
| Damage indicator | Threshold (index 0.3) | Typical cases |
|---|---|---|
| Population, fatalities | More than 10 fatalities | Toxic dispersion, fire, explosion |
| Population, injuries | More than 100 injured | High-activity substances |
| Surface water | More than 1 million m³ of polluted water | Spills, firefighting water |
Modelling with recognised software under unfavourable weather conditions, with recognised Probit functions for toxic, thermal and overpressure effects.
From OPAM short report to risk study
The short report identifies hazards and major accident scenarios. When the authority cannot rule out serious damage, it requires a risk study. The risk study follows the logic of a quantitative risk assessment (QRA). The result is a cumulative curve, compared with the FOEN assessment criteria. Where needed, risk is reduced following the ALARP principle.
Proportionate measures, following the ALARP principle.
When risk lies in the intermediate zone, the authority weighs the interests involved. We quantify each measure on the cumulative curve, so you invest where the safety gain is real.
Reduce the hazard at source
Limiting quantities, substituting a product or moderating operating conditions. This is often the most effective measure.
Reduce severity
Limiting the extent of a release and its consequences for the population and the environment.
Reduce frequency
Lowering scenario frequencies through technical and organisational barriers.
A clear file, ready for the authority.
- Emergency plans based on the study scenarios
- New projects and new products: impact on the overall risk
- Coordination between land-use planning and OPAM for projects near an installation
OPAM study: your questions
When is an OPAM short report required?
As soon as the maximum quantity of a substance, preparation or special waste on site exceeds the FOEN quantity threshold. A short report is also required in building permit procedures for an installation subject to OPAM.
What is the difference between a short report and a risk study?
The short report estimates the extent of damage for worst-case scenarios, taking into account only passive protection measures such as fire walls or retention basins. If the major accident index reaches 0.3, the authority requires a risk study, which also quantifies scenario frequencies and expresses risk as a cumulative curve.
Which tools do you use for modelling?
We use EFFECTS (Gexcon), a recognised consequence modelling software, with Probit functions for toxic, thermal and overpressure effects, and failure frequency data from international references.
When must the report be updated?
When installations or quantities change, new products are introduced, the site is extended, or the population density around the site changes.
What if the risk is not acceptable?
We identify risk reduction measures, starting at source (quantities, substitution), then severity and frequency, and show their effect on the cumulative curve until an acceptable level is reached.
Do you work outside Switzerland?
Yes. We also work under the EU Seveso III directive, which pursues objectives comparable to OPAM.
An OPAM report to prepare or update?
Tell us which substances and quantities are involved. We will tell you which steps apply and how we can help.