The environmental consequences of major accidents and the connection between failures in process safety systems and environmental damage are getting increased focus under COMAH Regulations. Whilst there is an obvious link in principle between incidents and environmental consequence, there has been relatively limited work done to prioritise planning and preventative expenditure that reflects environmental, as well as safety, outcomes.
Restitution of environmental damage under the Environmental Liability Directive may require the provision of off-set land of equal value to the land that has been impacted. Therefore given the number of bulk storage vessels and the volumes of hazardous materials stored at individual COMAH sites, the risks associated with these assets can be significant. Coupled with this the drive for engineering improvement often overlooks the specific risk drivers for environmental impact.
Process safety management, on the other hand, routinely employs quantitative risk assessment to understand and help prevent and manage the risk of intrinsically highly unlikely events (major accidents), with the incorporation of steps to mitigate consequences if an event was actually to occur. Effective management of environmental risks can learn from this approach by considering what measures may limit adverse effects from unlikely, but major events, prior to an event occurring. This approach is applicable to individual assets such as bulk storage tanks or for entire sites.
One of the greatest challenges in transferring process safety approaches to the environmental risks is considering proportionality in equating human life to environmental impact. Process safety assessment is familiar with the concept of a tolerable worker or societal risk, but what is a corresponding environmental consequence which warrants the same degree of investment in prevention or mitigation? In the UK, the original Department of Environment Transport and Regions (DETR) guidance on Major Accident to the Environment (MATTE) (DETR, 1999) outlined a range of potential environmental impacts which would be considered to be intolerable. Much of the work required to assess whether a particular major accident scenario could generate such levels of impact were subjective with little effort applied to assess whether, for instance, a tank release could actually contaminate a particular extent of a protected site or area of groundwater.
The historical approach of selecting ‘representative’ scenarios for analysis of environmental risks is no longer an accepted approach for the Competent Authority when enforcing the COMAH Regulations. With the introduction of the Containment Policy and the realisation of the potentially significant cost implications to meet compliance, there has been a shift towards a risk based approach to demonstrating tolerability of potential environmental impacts. COMAH registered sites are required to complete a screening level assessment to assess the current tolerability of risk, which now looks holistically at all of the risks at a site and at the potential impacts to each of the potentially affected receptors. The aim of this approach is to identify areas of intolerable risk and to assess appropriate measures to lower that risk. The approach, can, however, also present significant benefits to non-COMAH sites when it comes to prioritising investment in site upgrades on the basis of actual risk rather than perceived benefit.
With improvements to site infrastructure to manage impact being both costly and disruptive, the ability to reduce their need is a clear imperative. A clear and robust framework which takes account of actual risk will allow expenditure to be focused, such that areas of pollution risk rather than areas with pollution potential, can be addressed and relevant improvements made where need is greatest.
Want to know more?
For further information contact Simon Gibbons, Technical Director, Contaminated Site Management Practice