Thought Leadership

Navigating the Environmental Impact Assessment (EIA) Process in the UK

city landscape with green environment
Environmental Impact Assessment (EIA) Process

By Stefan Astley, RWDI, Senior Project Manager

New residential developments, commercial buildings, schools, hospitals, greenfield developments, high-density urban developments, as well as a wide range of other projects in the built environment, all have impacts on the surrounding natural and built environment. Additionally, as a society we are now increasingly concerned about the impact new developments can have on the environment and local community.   

As a result, most local planning authorities in the United Kingdom require the completion of environmental impact assessments (EIAs) for projects that are expected to have a certain level of influence over their surrounding environment. Let’s explore what you need to know when navigating EIAs and how a more holistic approach to technical services and studies can help streamline the process for your EIA management partner.

What is an Environmental Impact Assessment?

An environmental impact assessment (EIA) is a set of analyses and other inputs used to examine the potential effects of a project proposal on the surrounding environment. The assessments that make up an EIA help ensure that those making decisions as part of the project take the time to consider the potential environmental effects prior to making a decision – as well as aim to reduce those effects where needed.

In the United Kingdom, EIAs are designed to provide the local planning authority and public with the necessary information about the environmental effects of a project to aid in the decision about whether to grant planning permission. 

What is the Legislation in the UK? 

The process and requirements surrounding environmental impact assessments in the UK are detailed in the Town and Country Planning (Environmental Impact Assessment) Regulations 2017. Under this legislation, there are several components to the EIA process:

Components of the EIA process

Generally, separate consultants undertake the technical assessments that feed into each of the EIA components and chapters using traditional tools and approaches. This can, in some instances, lengthen the planning process due to increased communication needed to ensure all necessary sections are adequately represented in the EIA.

EIA Planning Policies in the UK

When completing an EIA in the UK, various policies must be considered. These policies come in at several levels: national, regional, local, and specialist. In addition to the various steps involved in the EIA planning process, the policies can also present a navigation challenge.

National Policy

Two policies at the national level feature in the EIA planning process:

  • National Planning Policy Framework (NPPF): Provides a detailed outline on the government’s planning policies for England and how they are to be applied. It is intended to help contribute to sustainable development, including residential, commercial, and infrastructure, in the country.
  • National Planning Policy GuidanceProvides detailed guidance separated by sector (categories), including noise and air quality.


Regions throughout the UK also have their own planning policies in place, which often provide increased detail for projects that will be specific to their area. One such example is the London Plan, which is also known as the spatial development strategy for Greater London and provides a framework for the way in which London will develop over the next 20 to 25 years.

aerial view of the city of London

This plan, as part of London’s statutory development plan, contains policies that are intended to inform planning application decisions. Any local plans – those for individual London boroughs – must conform, in general, with the London Plan’s requirements to reflect continuity for sustainable development.

Local Policy

Local policies, such as the London Borough of Tower Hamlets Local Plan, outline how growth will be managed in the area, including policies regarding environmental protection. This is precisely where EIAs can come into play, such as with the local plan requirements surrounding air quality, to help communities move in the right direction.

Specialist or Dedicated Policies

When it comes to the EIA planning process, there can also be various specialist or dedicated policies or guidance to consider. Examples of these include the City of London Microclimate GuidelinesCity of London Thermal Comfort GuidelinesLondon Air Quality Positive Guidance, and Leeds Wind and Microclimate Toolkit.

The specialist policies and guidance assess how the project can influence a specific area of focus (e.g., thermal comfort) in a defined location. These policies often provide guidance and requirements projects must follow as part of their EIA planning application.

Technical Considerations in EIA Planning

Different projects can have a wide range of varying effects on the environment – and these effects can be further varied based on the stage of the project’s development. For instance, the construction of a new motorway may cause noise impacts and after completion, an influence on surrounding air quality due to a higher traffic volume in the area.

The nature of the project will also determine which aspects of technical analysis require consideration. Infrastructure has different requirements than buildings, for example. EIAs address this, but since there can be varying environmental effects, the EIA process can be quite complex and often requires input from a variety of experts and stakeholders. To that end, we are going to explore some of the technical considerations in EIA planning.

Planning and Noise

The way in which noise behaves both in and around a project has a significant influence on the character and comfort of the project site as well as the surrounding area. Most projects that have a noise component to their EIA application must avoid the noise causing a significant adverse impact on the health or quality of life of those living, working, or passing through the area. They must also minimize potential other health and quality of life impacts resulting from new development noise.

rail construction noise

With respect to noise, an EIA can ultimately result in the need for passive interventions throughout a building, structure, or infrastructure. Tests and practices that can contribute to the noise component of an EIA planning application include:

  • Scoping,
  • Establishing the baseline,
  • Predicting noise levels,
  • Assessment,
  • Mitigation, and 
  • Reporting and monitoring.

Many policies rely upon specialist input to ensure the guidance is interpreted and transferred appropriately to a particular project. This includes ensuring projects adhere to applicable noise limits.

Planning and Air Quality

Air quality can have not only a significant impact on health, but also an individual’s experience in or around a building, structure, or outdoor space. Even individuals living nearby certain project types, such as construction sites, can be affected by air quality.

When it comes to air quality, many regulations surrounding EIA planning applications outline the limits that must not be exceeded regarding local air quality impacts as well as national and even regional objectives regarding pollutants. In some cases, regulations also provide frameworks on improving air quality in relation to new developments.

air quality construction

Air quality monitoring helps evaluate levels of potential air pollutants near emissions sources and whether they are under air quality limits or otherwise within an acceptable range based on relevant air quality standards. 

Specialist input can help direct appropriate action, from source testing and ambient monitoring to air quality dispersion modeling to inform ventilation design and to show compliance with EIA planning application requirements. They can also advise on mitigation measures to meet regulations where necessary – including recommendations for design schemes to minimize emissions and their impacts. Some of the regulations that can play a role in EIA planning with respect to air quality include BREEAM for Indoor Air Quality and Air Quality Positive Guidance.

Planning and Wind

Many guidelines and regulations, such as the NPPG, look at the potential for buildings and structures, including tall buildings, to affect the wind microclimate and surrounding environment. Wind considerations are a major part of the City of London Wind Microclimate Guidelines, which offer specific requirements for the studies required as part of EIA planning applications.

wind microclimate

The major aim of wind assessments for an EIA, whether they be wind tunnel tests or CFD simulations, is to ensure the safety of pedestrians passing by a building or structure as well as those who use it. This is because building elements can redirect wind to where pedestrians are, including locations sensitive to high winds that can make pedestrians especially vulnerable. Thus, the precise tests can vary based on the project at hand and often require specialists to guide the appropriate testing for EIAs as well as the recommended mitigation measures. 

When it comes to mitigation measures, wind assessments can help recommend the types of measures that involve subtle design choices and other methods of intervention. The subtle mitigation measures offer a smoother experience for pedestrians as well as holistically assist in making the specified area a more pleasant place to be. They also ensure the wind environment of the area meets EIA requirements and matches the intended use of the space.

Planning and Sun/Glare

For issues related to sun and glare, policies and guidance aim to ensure projects:

  • avoid glare that may adversely impact on quality of life and safety due to the new development,
  • minimize the risk of excessive loss of daylight and sunlight to existing public spaces and residences, and
  • comply with regulatory limits regarding levels of acceptable solar glare and shadowing.
The Shard Glare

The way a project interacts with the sun will vary depending on several factors, which means input from specialists is still crucial to ensure guidance is appropriately interpreted and applied to projects.

Indeed, shadows and reflections are not always detrimental. New buildings, for instance, can leverage reflectivity to direct sunlight into enclosed courtyards and plazas that would not have otherwise had access to natural light and a measure of shadow can help keep spaces cool in the summer. The key in an EIA is to thoroughly understand how a project interacts with the sun to avoid issues such as distracting or blinding drivers on nearby roadways and excessive shadowing. 

Simulation techniques such as daylight modeling studies and glare analysis can help provide this understanding. These tools not only help inform the EIA and design mitigation measures to ensure compliance with local requirements but can also provide valuable insights into other aspects of building design like renewable energy potential and internal solar heat gains.

Planning and Thermal Comfort

Although thermal comfort does not feature as a dedicated chapter of the Environmental Statement of EIAs as of early 2024, considering it is quite beneficial, and is therefore increasing in frequency. The City of London is leading the way in considering thermal comfort with its guidelines. It brings together two EIA disciplines that are traditionally evaluated separately: daylight/sunlight/overshadowing (DSO) and wind.

thermal comfort patio

The holistic approach thermal comfort assessments provide can be quite valuable. For instance, a wind assessment may indicate a particular location will be too windy for pedestrians to have a comfortable experience in the development’s surroundings. However, if that location is also sunny, then a thermal comfort study will acknowledge the counterbalancing effect of the sun on one’s overall comfort. The reverse is also true – an overshadowed space could still be thermally comfortable if the winds are low.

This provides a more nuanced approach to discussing outdoor comfort and can reveal locations that are reasonably comfortable despite being a bit windy on some days. This can help developers avoid unnecessary mitigation designed to produce low wind speeds or avoid shadows that would have been otherwise mandated if the wind microclimate or DSO study was considered in isolation.

Moving Forward with a Holistic Approach to EIA Planning

With EIAs encompassing a number of climate-related elements, like air quality, wind, sun, glare, noise, and thermal comfort, it is unsurprising that often these components influence one another. For example, wind and sunlight have a direct impact on the thermal comfort of a project.

While individually addressing each is necessary to meet legislative requirements, taking a holistic approach by centralizing as many technical services and studies as possible under one consultative partner provides many benefits. These include integrating information into all necessary components of an EIA, streamlining planning to support EIA management partners, and getting to the submission phase faster. Further, the result can often produce a high-performing space that creates a better human experience.  

Streamline your EIA planning process