QMark: Cumulative impacts – what is a reasonably foreseeable action?

22nd February 2016

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  • Business & Industry ,
  • Built environment ,
  • Construction ,
  • Planning ,
  • Management



Gavin Winter, chartered town planner at Spawforths, considers what can be considered as 'reasonably forseeable' in an environmental statement.

Spawforths dealt with a case in which an objector to a scheme argued that a number of new business opportunities it was planning should be included in a cumulative impact assessment.

The objector did not submit any evidence to suggest that the planned business opportunities would definitely come to fruition since he had not submitted a planning application for them, nor did he provide any other details on the plans.

We then assessed the legal context before analysing whether the cumulative impacts of a proposed development should be assessed within an environmental statement (ES) and if it was reasonably foreseeable.

European Community Directive 85/337/EEC, as amended, requires the assessment of cumulative effects at a project level within an EIA. This legislation has been transposed in the UK through schedule 4, part 1 of the EIA regulations.

The directive includes a test of reasonableness which is allied to the state of knowledge and availability of information. The legislation does not stipulate any particular methodology for assessing cumulative impacts, nor is there any specific guidance on the meaning of ‘reasonably foreseeable’. However EU guidelines published in 1999 set several methods that can be used.

The guidance defines cumulative impacts as ‘impacts that result from incremental changes caused by other past, present or reasonably foreseeable actions together with the project. For example, incremental noise from a number of separate developments or the combined effect of individual impacts, such as noise, dust and visual from one development.’

Several developments may not have significant impacts individually, but could have a cumulative effect when considered together. For example, the development of a golf course may have an insignificant impact, but when considered with several nearby golf courses there could be a significant cumulative impact on local ecology and landscape.

The following guidance is also provided in relation to scoping in paragraph 4.2.1 of the guidance:

‘There are limitations in defining the area and time boundary that would be affected by the project. For example, it is only reasonable to consider current events and those that will take place in the foreseeable future. Furthermore, the assessment can only be based on the data that is readily available. There needs to be a cut-off point at which it can be said that the impacts cannot be reasonably attributed to the project. This should be established. For example this may establish the point beyond which there can no longer be any reasonable mitigation.'

Combined effect of the directive, the regulations, guidance and case law

The requirement to assess the cumulative impact of a development with other developments is subject to the availability of information and to the test of reasonableness.

There is relatively limited judicial guidance on this point. However, of direct relevance is the decision of the High Court in Louise Bowen-West v Secretary of State for Communities and Local Government, Northamptonshire County Council or Augean Plc (2011). The court accepted in this case that the inspector and the secretary of state were entitled to find that a particular proposal need not be assessed as a cumulative effect because it was a future proposal that lacked detail. That was treated as a ‘rational conclusion germane to the overall judgement made by the secretary of state’.

Overall, the courts’ approach to EIA and whether or not its content is adequate including its assessment of cumulative effects is to ask whether the approach adopted by the statement is sufficient on Wednesbury principals. This means considering whether the authority, in accepting the ES, has behaved in a way that no reasonable planning authority could, in other words, if it has behaved in a way which is so unreasonable as to amount to perverse.


Based on interpretation and application of the directive, regulations, guidance and case law, any assessment of cumulative impacts should be based on the test of reasonableness allied to the state of knowledge and availability of information.

If a project would not in its own right come under the directive or the regulations, or does not have the requisite degree of certainty, clarity and availability of information, it should not be a reasonable requirement to include it as part of cumulative impact assessment.

Based on the facts presented and by applying the interpretations and tests that the courts would apply to any ES, it was reasonable and rational for the local planning authority not to ask for the cumulative impacts to be included in the environmental statement.


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