Environmental Risk Assessment is a technique that has been created to help in understanding and addressing some of the key environmental  issues. Environmental Risk is a measure of potential environmental risks that combines the probability that an occurrence may result in environmental degradation. Environmental Risk Assessment is an important technique for analyzing the probable environmental repercussions of a particular action or activity and for making educated judgments about the amount of environmental risk.
Environmental Risk Assessment (ERA) enables a proactive approach to environmental management rather than a reactive one focused solely on corrective actions. ERA is now widely regarded as a critical tool for firms looking to incorporate environmental concerns into their operations.

The Environmental Risk Assessment is carried out in order to,

• Identify and address any dangers primarily caused by the proposal.
• Determine the likelihood of relevant potential direct and indirect outcomes of the listed dangers.
• Quantify and classify risks in order to identify the important environmental challenges that require further evaluation and to offer a method for focusing on a variety of management solutions to appropriately manage those risks.
• Determine the amount of uncertainty in risk estimates and the efficacy of risk controls in risk mitigation.
• Identify stakeholders who may experience residual risks.
• Provide visible and auditable assistance in mitigation prioritizing and escalation decision making.
• Show that the proposal represents best practical technology by incorporating Best Practice Measures and industry standards, where applicable.

ENVIRONMENT RISK ASSESSMENT FRAMEWORK

Environmental Risk Assessment necessitates a systematic framework to enable frequently complicated analyses to be carried out in a consistent and proportionate manner to the amount of risk.

The framework's primary aspects are described in the following sections of this Guideline. It is critical to remember the following basic principles:

• The need to correctly define the problem at the outset.
• The need to screen and prioritise all risks before quantification.
• The need to consider risks of different options.
• The iterative nature of the risk assessment process.

THE THREE TIERS OF RISK ASSESSMENT

Each of the three tiers of risk assessment illustrated in Figure 2.1 includes five stages:

• Stage 1: Hazard Identification
• Stage 2: Identification of Consequences
• Stage 3: Magnitude of Consequences
• Stage 4: Probability of Consequences
• Stage 5: Significance of Risk

The components of each of these stages are described below,

Stage 1: Hazard Identification

A hazard is defined as a property or situation that, under certain conditions, might cause injury. The identification of risks at each step of the risk assessment process is critical in determining the final assessment's scope. It is also critical to identify both major and secondary dangers during the procedure.

Stage 2: Identification of Consequences

The potential repercussions of a certain danger are determined by  inherent nature of the hazard. At this point, the whole spectrum of potential outcomes should be assessed, without regard to the likelihood (probability) of these events. This enables for an initial examination of a broad range of potential environmental repercussion, even if some may be regarded as insignificant owing to low probability.

Stage 3: Magnitude of Consequences

A particular hazard's repercussions may include current or prospective harm to human health, property, or the natural environment. The scale of repercussions may be assessed in a variety of ways, depending on whether they are examined as part of a risk screening process or a full risk assessment. The following concerns must be considered at any level of the process.

• Spatial scale of the consequences
• Temporal scale of the consequences.
• The time of onset of the consequences.

The geographical scope of environmental harm will frequently extend beyond the boundaries of the hazard's source. This must also be considered during the risk assessment, or else the entire scope will be too limited.
Environmental damage can range from temporary to permanent. It is therefore important to define the chronological scale of any impacts in order to identify importance.

It is also critical to determine the period of beginning of the repercussions, since certain environmental effects may not appear for years after the damaging occurrence. For example, a hydrocarbon or hazardous chemical spill on the ground may gradually contaminate an underground aquifer. This, however, will not be obvious until the pollutants have percolated.

It is also critical to determine the period of beginning of the repercussions, since certain environmental effects may not appear for years after the damaging occurrence. For example, a hydrocarbon or hazardous chemical spill on the ground may gradually contaminate an underground aquifer. This will not be obvious until the toxins have percolated into the earth, which might take some time. In such circumstances, modelling of pollutant transmission routes is essential to develop a measurable foundation for risk assessment.

Stage 4: Probability of Consequences

The probability of a particular consequence being realised has three components:

1. The probability of the hazard occurring: - Assigning probability is as easy as utilising expert opinion on a scale of 0 (No Impact) to 5 (High Impact) (Critical). On the other hand, more complicated circumstances may necessitate a more sophisticated strategy, such as the use of probability distributions. Monitoring data or 'worst case' scenarios can also be used to evaluate probability.
2. The probability of sensitive receptors being exposed to the hazard: It is critical to determine whether a pathway exists between the source of the hazard and a receptor. A danger exists only if there is a connection between the three elements: Source-Pathway-Receptor. If routes exist between the source and the receptor, the degree of exposure of the receptor must be quantified. External variables such as the time of year, current climatic conditions, local geological/hydro-geological conditions, and so on can all have an impact on exposure.

3. The probability of harm resulting from exposure to the hazard- The probability of a receptor being harmed is determined by the receptor's sensitivity to the specific hazardous substance and the duration of exposure. Because information on the dose/response relationship for specific receptors is not always readily available it is often necessary to take a simplistic and pragmatic approach to assigning harm probability. Individuals who are required to carry out probability assessments should be suitably experienced and competent to do so.

Stage 5: Significance of Risk

After determining the probability and degree of the outcomes that may occur as a result of a certain hazard, the risk must be contextualized using value judgments. This might be accomplished, for example, by referring to environmental quality standards or toxicological thresholds. When there are no quantitative limitations of acceptability, such as the inherent biological importance of a specific area, assessing significance becomes extremely challenging.

Appraisal of Options

After determining the magnitude and relevance of the risk posed by particular hazards, the next step is to develop risk management strategies. The options that will typically have to be considered are:

• Exploring with stakeholders the acceptability or otherwise of the risk.
• Reducing the hazard through use of technology.
• Mitigating the effects through environmental management.
• The remaining sections of this Guideline provide further details on the structured risk assessment methodology described above

Risk Ranking

• Risk ranking is a useful strategy for prioritising and comparing both measurable and non-quantifiable hazards. It essentially provides a weighting to the various dangers under consideration and listing choices based on their risk score. A probability versus consequence matrix

Table 4 presents a summary of the impacts significance rating.When the effect is classified High (Red), an alternate location or technology should be considered, or preventative and control measures should be integrated into the project design if none are available.

Environmental control and/or management measures would be required in the project design and execution plan for impacts graded Medium (Yellow). The effectiveness of these measures would be evaluated as part of the project Environmental Management Plan's impact monitoring strategies.

For the effects of a Low (Blue) rating, environmental management measures (e.g. internal processes, staff training) and continuous improvement would be the ideal solution.