Risk Classification Matrices - Viridor

1 Risk Classification Matrices For there to be an environmental liability, there must be a source something capable of causing pollution or harm, a receptor and a viable pathway between them, a pollutant linkage. If one of these elements is missing, there can be no significant risk. If all are present, then the magnitude of the risk is a function of the toxicity and mobility of the pollutant, the sensitivity of the receptor and the nature of the migration pathway. The potential risk is assessed based upon the severity of the potential consequence and the probability of it occurring. Following guidance provided in CIRIA document C552 (Contaminated land risk assessment. A Guide to Good Practice) a summary of the risk Classification process is presented below. Consequence of Risk Being Realised (based on C552 CIRIA, 2001). Consequence of risk being realised Classification Category Definition Examples Short-term (acute) risk to human High concentrations of cyanide health likely to result in significant Humans on the surface of an informal harm as defined by the Environment recreation area.

2 Protection Act 1990, Part 2A. Short-term risk of pollution (note: Controlled Water Resources Act contains no Major spillage of contaminants Severe Waters scope for considering significance of from site into controlled water. pollution) of sensitive water resource. short-term (acute) risks Explosion causing building only Catastrophic damage to collapse (can also equate to a Property buildings/property. short-term human health risk if buildings are occupied. A short-term risk to a particular Ecological ecosystem, or organism forming part System of such ecosystem. Chronic damage to Human Health Concentrations of a contaminant Humans ( significant harm as defined in Defra from site exceed the generic, or Medium 2006). site-specific assessment criteria chronic (long- Pollution of sensitive water resources term) risks ; Controlled (note: Water Resources Act contains Leaching of contaminants from a significant Waters no scope for considering significance site into a major or minor aquifer.))

3 Harm of pollution). Ecological A significant change in a particular Death of a species within a System ecosystem designated nature reserve. Consequence of risk being realised Classification Category Definition Examples Controlled Pollution of non-sensitive water Pollution of non-classified Waters resources. groundwater. Mild Significant damage to buildings, structures and services ( significant Damage to building rendering it chronic (long- harm as defined in Circular on unsafe to occupy ( , term) risks ; less Property Contaminated Land, Defra, 2006). foundation damage resulting in sensitive Damage to sensitive instability). receptors buildings/structures/services Ecological Significant damage to crops. Damage System to the environment. Harm, although not necessarily Financial / significant harm, which may result in project a financial loss, or expenditure to resolve. Minor Non-permanent health effects to The presence of contaminants at chronic (long- human health (easily prevented by such concentrations that Humans term) risks ; mild means such as personal protective protective equipment is required clothing, etc).

4 During site works. The loss of plants in a Easily repairable effects of damage to Property landscaping scheme. buildings, structures and services Discolouration of concrete. Probability of Risk Being Realised (C552 CIRIA, 2001). Probability of risk being realised Classification Definition There is a pollution linkage and an event that either appears very likely in the short term and High almost inevitable over the long term, or there is evidence at the receptor of harm or Likelihood pollution. There is a pollution linkage and all the elements are present and in the right place, which Likely means that it is probable that an event will occur. Circumstances are such that an event is not inevitable, but possible in the short term and likely over the long term. There is a pollution linkage and circumstances are possible under which an event could Low Likelihood occur. However, it is by no means certain that even over a longer period such event would take place, and is less likely in the shorter term.

5 There is a pollution linkage but circumstances are such that it is improbable that an event Unlikely would occur even in the very long term. Risk Classification Matrix (C552 CIRIA, 2001). Risk Classification matrix (CIRIA C552, 2001, Consequence page 82) Severe Medium Mild Minor High Moderate/. Very High High Moderate Likelihood Low Probability Moderate/. Likely High Moderate Low Low Low Moderate/. Moderate Low Very Low Likelihood Low Moderate/. Unlikely Low Very Low Very Low Low Risk Classification Definitions (C552 CIRIA, 2001). Risk Classification definitions There is a high probability that severe harm could arise to a designated receptor from an identified hazard, OR, there is evidence that severe harm to a designated receptor is currently Very High happening. This risk, if realised, is likely to result in a substantial liability. Urgent investigation (if not undertaken already) and remediation are likely to be required.

6 Harm is likely to arise to a designated receptor from an identified hazard. Realisation of the risk is likely to present a substantial liability. Urgent investigation (if not undertaken already) is High required and remedial works may be necessary in the short term and are likely over the longer term. It is possible that harm could arise to a designated receptor from an identified hazard. However, it is either relatively unlikely that such harm would be severe, or if any harm were to occur it is Moderate more likely that the harm would be relatively mild. Investigation (if not already undertaken) is normally required to clarify the risk and to determine the potential liability. Some remedial works may be required in the longer term. Moderate /. Low It is possible that harm could arise to a designated receptor from an identified hazard, but it is Low likely that this harm, if realised, would at worst normally be mild.

7 There is a low possibility that harm could arise to a receptor. In the event of such harm being Very Low realised it is not likely to be severe.