Process safety in Europe is managed under the Seveso-III Directive. This demands that “the operator of an upper-tier establishment produce a safety report for the purposes of:
- demonstrating that … possible major-accident scenarios have been identified and that the necessary measures have been taken to prevent such accidents and to limit their consequences for human health and the environment.
i.e. human health and the environment are on an equal footing. The Buncefield report proposed a methodology using LOPAs for environmental risks from tank overfills but the definitions of harm were qualitative and open to different interpretations between operators and the regulator.
The Chemicals Downstream Oil Industry Forum (CDOIF) is a joint effort of industry and the authorities. A working group with members from UK refineries, chemical and petrochemical plants, tank storage, the HSE, the Environmental Agency and the Scottish Environmental Protection Agency followed up on the Buncefield Report to define an approach to define whether environmental risks are tolerable and/or ALARP, i.e.:
- define all “receptors” that could be affected by an incident
- define all scenarios where threats could lead to major accidents affecting any of the different receptors and the size of the consequence. Then, using LOPA,
- estimate initiating event frequencies and the probability of failure on demand of each of the barriers preventing the consequences thereby estimating the probability of affecting the receptors
For humans the UK-HSE’s guidance defines “intolerable” as the probability of a fatality exceeding 10-4/yr. (i.e. > one fatality per 10,000 years). What then is the environmental equivalent of a fatality? For the environment, the tolerability criteria are defined in terms of extent of damage and duration of harm to the receptor. This means that different criteria apply to each receptor but is does provides a “simple” technique, using LOPA, to determine whether the risks from the site are tolerable. Cost-benefit analysis is then needed to determine whether the outcome is ALARP or if addition barriers are needed.
The Freedom Industries incident provides a real test for the approach. In 2014 a leak through a tank floor led to contamination of the Kanawha River, in Charleston, West Virginia with 7,500 US gallons of 4-methylcyclohexanemethanol (MCHM). 170 people were treated, 14 people hospitalised and 300,000 people were without potable water for 5 days. Had West Virginia demanded risk assessments following the CDOIF approach then the risks from Freedom Industries would have be identified as “intolerable”, i.e. demanding improvements in the facilities or shutting it down.
See more of this Group/Topical: Global Congress on Process Safety