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Chapter 9: Prediction and Evaluation of Environmental Effects

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Content

Part 1 - Introduction

Part 2 - Legislative requirements

• The relevant statutory provisions

Part 3 - Prediction and evaluation of environmental effects

• What is being assessed?
• Predicting an environmental effect
• Evaluating an environmental effect
• Issues in prediction and evaluation

Part 4 - Annex: Alternatives

Part 5 - Annex: Significance

Part 6 - Annex: PPS Hierarchy

Part 1 - Introduction

9.1.1 The focus of the Environmental Assessment (Scotland) Act 2005 ('the Act') is on the assessment of significant effects on the environment arising from implementing a plan, programme or strategy ( PPS). There are two key steps in this assessment. The first is prediction, i.e. the identification of an impact and its magnitude. The second is evaluation, i.e. reaching a judgement on the significance of the identified impact: does it matter?

9.1.2 Some level of prediction takes place at all stages of the SEA process, as follows:

• Screening: at the screening stage the potential for significant effects on the environment from implementing the PPS are a factor in determining whether it qualifies for SEA. The Responsible Authority will therefore need an understanding of the potential impacts to make this determination ( Chapter 4).
• Scoping: the scoping stage considers the potential effects of the PPS when deciding whether environmental components should be scoped in or out of the assessment.
• Environmental Report: at this stage the potential impacts of the PPS and its alternatives are assessed, i.e. identified, described, evaluated and, as far as possible, mitigated.
• Monitoring: the requirement to monitor significant environmental effects after adoption is based on the assessment reported in the Environmental Report.

9.1.3 The purpose of this chapter is to help Responsible Authorities and other interested parties to understand how to predict and evaluate environmental effects.

Part 2 - Legislative requirements

The relevant statutory provisions

9.2.1 Sections 14(1) and (2) of the Act require the Responsible Authority to assess the likely significant effects of a PPS and its alternatives on the environment and to provide the results in an Environmental Report. The information to be provided in Environmental Reports is set out in Section 14(3) and Schedule 3 and guidance is provided in Chapter 6. The characteristics of the effects to be reported include:

• short, medium and long-term effects;
• permanent and temporary effects;
• positive and negative effects; and
• secondary, cumulative and synergistic effects.

9.2.2 Effects on the environmental components identified in Schedule 3 (Paragraph 6) should be assessed, unless scoped out at the scoping stage ( Chapter 5).

Part 3 - Prediction and Evaluation of Environmental Effects

What is being assessed?

9.3.1 Assessing a PPS usually involves breaking it down into its constituent parts, i.e. its aims and objectives, its policies, and its proposals. The Act also requires the assessment of alternatives to the PPS.

9.3.2 The place of a PPS in the PPS hierarchy will affect the level of detail in the assessment and the assessment methods used. For example, the assessment of a high-level policy is likely to be undertaken at a more broad-brush level than a PPS which includes locational proposals. Advice on hierarchy is provided in Part 6 of this chapter.

9.3.3 To reach a view on whether a PPS is likely to have significant environmental effects it is important to, firstly, predict the effects of the PPS and its reasonable alternatives and, secondly, to evaluate the significance of those effects.

Predicting an environmental effect

9.3.4 Prediction of effects involves:

• Identifying the changes to the environmental baseline which are predicted to arise from implementing the PPS, including its alternatives. These changes are identified ( i.e. predicted) by considering the key elements of the PPS against a set of assessment criteria. These criteria are often in the form of SEA objectives (described in Chapter 10), or could include those used in developing GIS constraints maps.
• Describing these changes in terms of their magnitude, i.e. their nature and scale. This is usually described in terms of their geographical scale, the time period over which they will occur, whether they are direct or indirect, permanent or temporary, positive or negative, probable or improbable, frequent or rare, and whether or not there are secondary, cumulative and/or synergistic effects.

9.3.5 Predictions do not have to be expressed in quantitative terms. Hard data may enable Responsible Authorities to make quantitative predictions, and this can be particularly useful where the effects of a PPS are close to a threshold, or cumulative. However, quantification is not always practicable, and broad-based and qualitative predictions are equally valid and appropriate. These may be expressed in easily understood terms such as "moving towards or moving away from" the SEA objectives or on a scale from >> (very positive) to (neutral) to << (very negative). It is suggested that predictions are linked to specific SEA objectives, e.g. "will the PPS promote change in a desired direction?" (see Chapter 10).

9.3.6 These predicted effects can be compared with one another, and with the "no PPS" or "business as usual" scenarios. Note that "no PPS" and "business as usual" scenarios can still involve changes to the baseline. In this context "business as usual" would mean no change to current practices.

9.3.7 The following list of illustrative questions may assist in taking forward prediction:

• Is the PPS/alternative distinct and clearly presented?
• Are they likely to have any adverse effects?
• Can these be reduced, prevented, reduced or as fully offset as possible?
• Can positive effects be enhanced?
• Can any of the effects be quantified in a meaningful way?
• Are any effects of the alternatives unclear or ambiguous?

Evaluating an environmental effect

9.3.8 Evaluation involves forming a judgement on whether or not a predicted environmental effect will be significant. The criteria set out in Schedule 2 of the Act will be useful when considering the likely significance of these effects, in terms of the magnitude of effects and the nature and sensitivity of the receiving environment.

9.3.9 When evaluating significance it may help to use a checklist of questions. The following are illustrative of the type of questions and are not exhaustive:

• How sensitive is the receiving environment?
• Which communities are affected?
• Would the impact establish a precedent?
• Are environmental limit values or targets being threatened?
• Are designated/protected areas or species adversely affected?
• Is an appropriate assessment under the Habitats Directive required? ¹
• Can the impact be mitigated? What is the potential cost of mitigation?
• What is the magnitude of impact? ( i.e. scale, duration, reversibility)

Issues in prediction and evaluation

9.3.10 When presenting the results of the assessment the following are useful points to bear in mind:

• Is it clear exactly what is proposed, and how the alternatives differ from each other or relate to the PPS as a whole?
• Is each PPS/alternative assessed likely to have a significant adverse effect in relation to each of the SEA objectives?
• If so, can the effect be prevented or its severity reduced and/or as far as possible offset?
• If the effect cannot be prevented, e.g. by conditions or changes to the way it is implemented, can the alternative be changed or eliminated?
• If its effect is uncertain, or depends on how the PPS is implemented, how can this uncertainty be reduced?

The most familiar forms of SEA prediction and evaluation are broad brush and qualitative, using professional judgement (supported where available by data) to identify whether a PPS is moving towards or away from each SEA objective. In some cases, specific data may be available to allow quantitative assessment.

9.3.11 In considering the effects of a PPS, some useful points to consider may be:

• When using symbols or other ways of presenting information regarding the likely effects ( e.g. positive, negative, uncertain, not significant), always explain and justify the choice of symbol.
• Focus on the significant effects.
• Where possible, use the assessment of effects to improve the environmental performance of individual policies as well as the PPS as a whole.
• Concentrate on the effects of the PPS, rather than other factors that may influence the achievement of the SEA objective - it is the influence of the PPS that is being assessed.
• Consider only effects that are likely to result from the influence of the PPS - discount those changes which would have happened anyway, irrespective of the PPS.
• Consider whether the effect is likely to be permanent or temporary, and the timescale over which the effect is likely to be observed.
• Provide detailed and quantitative predictions where possible but avoid using spurious measurements which are not grounded in evidence.
• Consider the effects of displacement of environmental problems to other areas as a result of the PPS.
• If there are risks or uncertainties attached to the assessment, these should be clearly stated.
• It is not desirable to use elaborate scoring or weighting in assessments or to "add up" scores across an assessment.

Examples of presentational tables are included overleaf for illustration; more examples are provided in the SEA Templates.

Part 4 - Annex: Alternatives

9.4.1 It is normal practice when developing a PPS to propose different ways of fulfilling its objectives. In the UK the term "options" is often used. Alternatives are thus developed as part of the PPS-making process; however, they may be amended or added to as a result of SEA. It is not the purpose of SEA to decide the alternative to be chosen for the PPS. This is the role of the Responsible Authority preparing the PPS or the decision-makers who have to make choices on the PPS to be adopted. The SEA simply provides information on the relative environmental performance of alternatives, and can make the decision-making process more transparent.

9.4.2 Alternatives should be sufficiently distinct in order to highlight the different environmental implications of each, allowing meaningful comparisons to be made at a strategic level. A hierarchy of alternatives is illustrated in Figure 9.1.

9.4.3 Some alternatives are discrete. These are often the broad options considered early in the PPS preparation. Other alternatives can be combined in various ways. Groups of policies that make up a PPS are often alternatives of this type. Alternatives may be grouped into scenarios, for instance rapid economic growth, low growth, "most sustainable" option, etc.

9.4.4 The alternatives identified should be appropriate to the remit of the PPS. For instance, demand reduction measures are often outside the control of the Responsible Authority. Some alternatives may not be practical, or within a Responsible Authority's powers, while others may not be appropriate to a particular stage or level of the PPS. A wider range of alternatives will be available at a regional level than at a local level, and decisions made at the "higher" level will close off some alternatives. Nevertheless, a Responsible Authority should consider and outline in the Environmental Report the relationship with higher level PPS, as this could suggest a wider, and more sustainable, range of alternatives than hitherto considered.

9.4.5 Stakeholders may usefully be involved in the generation and assessment of both strategic and more detailed alternatives through consultation. Demonstrating that there are choices to be made is a way of engaging stakeholders in the process. The alternatives considered throughout the process should be documented and reasons given to why they are or are not taken forward (Schedule 3 of the Act).

Part 5 - Annex: Significance

Significance in effect prediction and evaluation

9.5.1 The SEA Practical Guide ( ODPM et al, September 2005) distinguishes between impact prediction and impact evaluation (Figure 9.5):

• Prediction involves identifying the changes to the environmental baseline which will arise from the PPS, and describing these changes in terms of their magnitude, i.e. geographical scale, time period over which they occur, whether they are permanent or temporary, positive or negative, probable or improbable, frequent or rare, and whether or not there are secondary, cumulative and/or synergistic effects.
• Evaluation involves forming a judgment on whether or not a predicted effect will be significant. This judgment typically takes into account the magnitude of the potential effect, and the value and sensitivity of the receiving environment.

Figure 9.5 Significance in prediction, evaluation and mitigation (adapted from Therivel, 2004)

9.5.2 It is not the purpose of this guidance to establish a single method for determining significance. Such guidance would constrain the assessment inappropriately in that it could not possibly take account of key factors such as the context and nature of individual PPS. Instead, the following principles are intended to offer direction to those defining significance in the context of their own PPS:

• Impact evaluation involves a systematic and transparent approach covering all SEA issues ², and both positive and negative effects;
• It is not appropriate to offset negative and positive effects in order to determine likely significance;
• Where significance is uncertain, more rather than less significance should be assumed for negative effects, and less rather than more significance should be assumed for positive effects, in accordance with the precautionary principle;
• Expert judgement is acceptable, and often inevitable, given the challenge in finding appropriate methods and measurements, as well as the fact that data may not always be available. Where expert judgement is key to a determination of significance the source and nature of that expert judgement must be made clear. Data gaps should be commented on, and if possible they should be addressed;
• If established criteria or quantitative standards are in place then they should be used if they can be properly applied in the context of the PPS. Often, however, a qualitative statement will be needed. It should always be clear exactly what expert judgment was used to set the qualitative standard and the method used for measuring it.

9.5.3 Figure 9.6 shows how impact magnitude and environmental sensitivity come together to identify significance. A given PPS will clearly have a more significant impact if it affects a highly vulnerable area, or one that is closer to its environmental threshold/capacity, than one that is less so. Value and sensitivity can be determined from, for instance:

• Designations ( e.g. National Park);
• Other measures of value, e.g. areas that are heavily used by people, habitats that support rare species, buildings that are particularly sensitive to disturbance ( e.g. hospitals);
• Environmental standards and thresholds ( e.g. air or water quality standards, information about water supply v. demand). The closer that an environmental component is to its threshold, the more significant an impact on it will be;
• Public, stakeholder, and/or expert views on environmental aspects that they consider to be important or vulnerable.

Figure 9.6 - Identifying impact significance (based on Therivel, 2004)

Part 6 - Annex: PPS Hierarchy

From SEA to EIA - hierarchies of plans, programmes, strategies ( PPS) and projects

If an SEA has been carried out on a high level or "parent" PPS, is one required for PPS at lower tiers or later stages?

9.6.1 Section 14(3)(d) of the Act provides for avoidance of duplication between PPS in hierarchies. In practice the extent of assessment needed will often depend on the relationship between the PPS concerned. "Lower level" PPS are generally more detailed and location-specific than those at higher tiers, and an SEA may therefore be needed to assess effects not previously covered in the necessary detail. Avoidance of duplication is important but it is still important to make clear links to earlier Environmental Reports that contain relevant information. If re-using information the Responsible Authority should ensure that the information remains up to date and accurate. Figure 9.7 demonstrates that many PPS will have an inter-relationship and may offer opportunities to share assessment data.

9.6.2 Where a PPS includes proposals for individual projects, these need to be assessed at a sufficient level of detail to enable significant environmental effects to be broadly predicted. This is particularly helpful where the PPS sets the context for decision-making on whether to proceed with the proposal, or where alternatives are excluded or significantly reduced at that stage. The EIA Directive does not require consideration of alternatives, although if developers have considered alternatives they are required to report on this. Where EIA is needed later for a project, it is likely to be informed by the findings of the SEA, but it will not usually be appropriate to provide the level of detail needed for EIA in the context of the PPS³.

Figure 9.7 2005 EIA/ SEA Complex Relationships but Clear Boundaries
(Based on a table developed by Paul Tomlinson TRL Limited 2005)

If an SEA has been done, is EIA still needed at a later stage?

9.6.3 The Act does not dis-apply EIA Regulations and therefore does not remove the need to carry out EIA. In practice an SEA will typically be concerned with the significant environmental effects of broad strategic proposals and alternatives. EIA is project-specific and will require detailed information on the effects of a particular proposal on the environment in a particular location. The Environmental Report produced through SEA may well help with the preparation of an EIA by providing valuable data and analysis but will not remove the need for one.

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