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An overview of Environmental Impact Assessment

EIA: what it is, when it’s needed, the processes involved and tips for reviewing reports.

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Last updated: 2 July 2025

What is Environmental Impact Assessment?

EIA is a tool that is used to assess the potential impacts of a development on the environment. It only applies to certain development proposals which are likely to have significant environmental effects due to their type or scale (eg a new power station, large housing development, major roads) or is located within a sensitive area (eg, a Site of Special Scientific Interest or a Special Protection Area). 

The EIA process allows for any significant effects on the environment, and any measures to avoid, reduce and compensate for such effects, to be identified early on in the planning process so they are properly understood by the applicant, public and the decision maker. Where the EIA procedure shows that a development will have significant adverse effects on the environment, this does not automatically mean that planning permission must be refused. It remains the role of the local planning authority (LPA) to judge each planning application on its merits within the context of the development plan, taking account of all material considerations, including the environmental impacts.  

The requirement for EIA in Wales is set out in the Town and Country Planning (Environmental Impact Assessment) (Wales) Regulations 2017. Different EIA regulations apply in England, Northern Ireland and Scotland, as well as for marine and forestry developments. 

When is an EIA required?

EIA may be necessary for any planning application whose location, scale or nature are likely to have significant effects on the environment. 

The EIA Regulations 2017 set out types of development and thresholds to help developers and LPAs determine whether an EIA is required. These thresholds are set out in Schedule 1 and 2 of the EIA Regulations.  

The types of development that will always require an EIA, such as airports, motorways, and nuclear power stations, are listed in Schedule 1 of the EIA Regulations. Development that could require EIA, if it is located within a sensitive area or exceeds certain thresholds and is likely to have significant effects on the environment, is set out in Schedule 2 (eg a housing development providing more than 150 homes). 

What is the EIA process?

Screening

To confirm whether an EIA is required or not for a Schedule 2 development, an applicant can request a ‘screening opinion’ from the LPA. The LPA will require an EIA if the development proposal falls within certain guidelines, as outlined above.  

The applicant must submit certain information to allow this screening decision to be made, such as the location of the site, a description of the proposed development and description of the aspects of the environment likely to be significantly affected. Special consideration should be given to proposals potentially affecting sensitive areas.. The developer is unlikely to have all the information about the proposal at this stage, but it should be enough for the LPA to take a view.  

If an applicant does not request a screening opinion but submits an application that is a Schedule 2 development, then this needs to be screened for EIA at the application stage. If the LPA decides that EIA is needed, they cannot determine the application before an EIA is carried out. 

Scoping

If the proposed development requires an EIA, the issues to be considered in the assessment need to be determined. This is known as the ‘scoping’ stage. An applicant can ask the LPA for its opinion on what information needs to be included (a ‘scoping opinion’) but this isn’t compulsory.  

When it is very likely that an EIA is required for a development proposal, screening and scoping requests/opinions may be dealt with together. 

The LPA has three weeks to make a decision on screening requests and eight weeks to issue a scoping opinion unless a longer period is agreed with the applicant.  

Requests for a screening or scoping opinion are separate applications that generally precede the submission of a planning application for an EIA development. They are not subject to the same public consultation as a planning application, so no site notice needs to be displayed and neighbours are not notified. However, LPAs must make all screening and scoping applications available for public inspection for two years, so they can be viewed on the online planning register via the LPA’s website. 

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Top tip

To find out about EIA applications, including screening and scoping requests/opinions, you can register with Planning Alerts – a free service that sends you email alerts about planning applications in your local area.

At present, the service only covers nine local authority areas in Wales but their aim is to cover the whole of the UK.   

Check the screening and scoping applications (note that they will have a different reference number to the related planning application) to find out if the applicant and LPA consider the proposal to be an EIA development, and which factors they think should be assessed.

If you disagree with anything, make your views known by submitting comments to the LPA.  

Environmental Statement

Where EIA is required, the report that is produced and submitted with the planning application is called an Environmental Statement (ES). It is the applicant's responsibility to prepare the ES and submit it with their planning application.  

The ES must be published for consultation with the other planning application documents. The statutory consultation bodies eg Natural Resources Wales (the Welsh Government's statutory nature conservation advisor) and the public must be given 30 days to give their views about the proposed development and the ES.  

A planning application proposing EIA development has a determination period of 16 weeks, in which the LPA should make a decision on the application. This should give all interested parties more time to consider the impacts of the proposal. However, it is not unusual for complex cases to take longer than this, and the LPA can agree with the applicant that a longer period of time will be taken to issue a decision. 

What should an EIA application include?

An EIA application must be accompanied by an ES that includes certain information outlined in Regulation 17 of the EIA Wales Regulations 2017.  

Schedule 4 of the Regulations states that an ES must include the likely significant effects (direct and indirect) of a development on the environment, specifically the following factors:   
 

  • Population and human health   

  • Biodiversity  

  • Land, soil, water, and climate  

  • Material assets (eg built and natural assets such as energy infrastructure, transport, flood protection and amenity spaces), cultural heritage and the landscape  


An EIA therefore covers much more than an ecological assessment, which solely focuses on species and habitats (an assessment of ecological impact will make up the biodiversity section of an ES). Factors to be included within an EIA will vary depending on the individual development proposal.   

Who is qualified to carry out an EIA?

The applicant must ensure that the ES is prepared by competent experts and is accompanied by a statement outlining their relevant expertise, or qualifications, sufficient to demonstrate that this is the case. Most such professionals will also be members of a relevant accrediting body, such as the Chartered Institute of Ecology and Environmental Management (CIEEM), which is a good indication of the standard of their expertise. Surveyors or other report authors will usually list their accreditations, along with any other relevant academic qualifications (such as a Master of Science (MSc) degree), after their name.  

Pied Flycatcher
Top tip 

If a planning application hasn’t undergone EIA and you believe that it should have, you should raise your concerns with the LPA and specifically with the Planning Officer dealing with the case.

You should also alert relevant statutory consultees, such as Natural Resources Wales and the community council, who may be able to support and amplify your concerns and make representations to the LPA.  

What to look out for when reviewing EIAs

If you’re reviewing an EIA scoping report, make sure that it has identified all of the important wildlife you know to be present on the site or immediate surrounding area. For example: 
 

  • Does the scoping report identify all of the protected sites (such as local wildlife sites or nationally designated sites such as Sites of Special Scientific Interest) in the area potentially affected?   

  • Have all important species you know to use the site or immediate surrounding area been identified for impact assessment? (our How to record wildlife guide will give you an idea of which species are likely to carry most weight – see link in the Find out more section below)  

  • Are the timings and methods of any proposed surveys suitable for the species you know to be present eg, ensure wintertime surveys are proposed if you know the site is important for wintering birds.   

  • Have all existing sources of data that you know of been identified? If you have collected any wildlife records yourself that could be relevant, it is always best to ensure that these are made available to the applicant or their consultants as early as possible in the process – you can always agree terms for their use of the data.   

  
If you are reviewing the final Environmental Statement (ES), you should recheck the above points, even if you have already made comments on any of these at the scoping stage. In addition, you may wish to consider the following:  
 

  • Has the ES thoroughly assessed all of the possible impacts that could arise both during construction and longer-term use/operation of the new development? For example, if the proposed development is for new housing, has the report included assessment of the ‘indirect effects’ arising from occupants of the new houses, such as recreational disturbance to nearby wildlife sites?  

  • In your view, is the predicted scale of the likely impacts appropriately assessed (based on your knowledge or, better still, published research you are aware of) and is the assessment sufficiently precautionary where effects are harder to predict (such as where published research to show likely behavioural responses of the species concerned is lacking)?  

  • Where mitigation or compensation measures are proposed to protect wildlife or other interests, are these appropriate and likely to be effective based on your local knowledge of the species or habitats concerned (or based on experience from elsewhere)? If long term management or monitoring is needed, is it clear who will undertake this, for how long, and how will it be secured and funded?   

  
If you’re unsure about the conclusions of an ES on wildlife, you can always seek advice from a local wildlife expert (eg local branches of the Wildlife Trust or the Mammal Society, some of whom may already have been consulted on the development by the LPA) who may be able to help confirm or alleviate your concerns. However, do bear in mind that these organisations often have limited time and resources, so it’s best to ask them specific questions rather than to ask them to read whole chapters of the ES or other related documents.   

Finally, if you think that any part of the EIA is inadequate – object! Make it clear in your objection why you feel the assessment isn’t fit for purpose and send it to the LPA within the consultation deadline. If the LPA agrees, the applicant may be required to provide further information to satisfy the requirements of the EIA Regulations, which will be considered as part of the application process.  

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