Environmental · Mandatory · Pre-Construction

Contaminated Land Risk Assessment

A risk assessment evaluating contamination in soil and groundwater on a development site.

Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. EPA 1990 / EA Guidance remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.

Legal basis	Environmental Protection Act 1990 Part IIA + Environment Agency Land Contamination Risk Management (LCRM) Guidance
Status	Mandatory on brownfield sites
Prepared by	Environmental Consultant
Two-phase approach	Phase 1 desk study followed by Phase 2 intrusive investigation
Methodology	Source-Pathway-Receptor model — contamination risk only exists where all three elements are present

1. Contaminated Land Risk Assessment — Essential on Any Previously Used Site

Any site that has been previously developed or used for industrial, commercial, or agricultural purposes carries a risk of ground contamination. A contaminated land risk assessment is the process by which that risk is identified, characterised, and evaluated so that informed decisions can be made about the suitability of the land for its proposed use. Under Part IIA of the Environmental Protection Act 1990, local authorities have a duty to identify contaminated land in their areas, and the planning system requires developers to demonstrate that sites are suitable for their proposed end use.

The risk assessment follows a cost-effective two-phase approach. Phase 1 is a desk study and site walkover that gathers historical information about the site's past uses, reviews geological and hydrogeological data, and identifies potential sources of contamination without any intrusive investigation. If the Phase 1 study identifies plausible contamination risks, a Phase 2 intrusive investigation is carried out, involving soil sampling, groundwater monitoring, and laboratory analysis to determine the nature, extent, and concentration of any contaminants present. This phased approach ensures that intrusive investigation is targeted and proportionate to the identified risks.

The Environment Agency's Land Contamination Risk Management (LCRM) guidance provides the framework for assessing contaminated land risks. The assessment is built on the Source-Pathway-Receptor model: contamination risk only exists where a source of contamination, a pathway by which it can migrate, and a receptor that could be harmed are all present and linked. If any one of these three elements is absent, the risk is broken. The risk assessment must consider human health receptors, controlled waters, ecological receptors, and building materials.

Unexpected contamination during construction

Discovery of unexpected contamination during excavation must be immediately reported to the LPA and EA — work should stop until assessed. The presence of unexpected contamination can change the risk profile of the entire site and may require additional investigation, revised remediation strategies, and updated regulatory approvals before construction can safely resume.

2. Key Components

The following table sets out the key components that a contaminated land risk assessment must address. Each element contributes to building a complete picture of the contamination risk and the measures needed to make the site suitable for its intended use.

Component	What it covers
Site description	Current site layout, boundaries, surrounding land uses, topography, surface features, and the proposed development. The description must be sufficiently detailed to allow a reader unfamiliar with the site to understand its physical context.
Desk study sources	Historical Ordnance Survey maps, historical land use records, Environment Agency data (landfill locations, pollution incidents, abstraction licences), British Geological Survey data, local authority records, and any previous site investigation reports. The desk study must trace the site's history back to its earliest recorded use.
Geology and hydrogeology	Geological strata beneath the site, superficial deposits, solid geology, groundwater vulnerability, aquifer designations, source protection zones, and nearby surface water features. This information determines the pathways by which contaminants could migrate.
Potential contaminants	Identification of contaminants that may be present based on the site's historical uses. Former industrial uses may have left heavy metals, hydrocarbons, solvents, asbestos, acids, or other hazardous substances in the ground. Agricultural uses may have introduced pesticides, herbicides, and nitrates.
Source-pathway-receptor	A conceptual site model identifying all plausible contaminant linkages — each linkage requires a source of contamination, a pathway by which it can reach a receptor, and a receptor that could be harmed. Receptors include human health (future site users, construction workers), controlled waters, ecosystems, and building materials.
Risk assessment	Qualitative or quantitative assessment of the risks posed by each identified contaminant linkage. Phase 1 assessments are typically qualitative. Phase 2 assessments compare laboratory results against published screening values (such as Category 4 Screening Levels) and may include detailed quantitative risk assessment (DQRA) where generic assessment criteria are exceeded.
Conclusions	Summary of identified risks, whether further investigation or remediation is required, and any recommendations for construction phase controls such as watching briefs, materials management plans, or verification testing. The conclusions must clearly state whether the site is suitable for its proposed use or what further work is needed.
Prepared by	Name, qualifications, and professional memberships of the environmental consultant who prepared the assessment. The consultant should be a member of a relevant professional body such as the Society of Brownfield Risk Assessment (SoBRA), the Chartered Institute of Environmental Health (CIEH), or hold Specialist in Land Condition (SiLC) status.

3. Common Mistakes

Not conducting Phase 1 before groundworks

Commencing groundworks without first completing a Phase 1 desk study is a serious and costly error. The desk study identifies potential contamination risks that must be understood before any excavation takes place. Without this information, workers may be exposed to hazardous substances, contaminated material may be spread across the site or removed without appropriate controls, and the project may face regulatory enforcement action. The Phase 1 study is a relatively low-cost exercise that provides essential information for managing contamination risks safely and in compliance with planning conditions.

Not investigating historical uses back far enough

A desk study that only reviews recent site history will miss contamination from earlier industrial or agricultural uses. Many brownfield sites have complex histories spanning over a century, and the most significant contamination sources may relate to uses that ceased decades ago. Historical Ordnance Survey maps, trade directories, and local authority records must be reviewed back to the earliest available records. A site that appears to have been open land in recent decades may have been used as a gasworks, tannery, or chemical works in the nineteenth century.

Not protecting workers during investigation

Phase 2 intrusive investigation involves drilling boreholes, excavating trial pits, and handling potentially contaminated soil and groundwater. Workers carrying out the investigation must be adequately protected with appropriate PPE, health surveillance, and welfare facilities. COSHH assessments must be in place for the contaminants that may be encountered. Failure to protect investigation workers is a breach of the Control of Substances Hazardous to Health Regulations 2002 and the Construction (Design and Management) Regulations 2015.

Not including contamination contingencies

Even where a Phase 1 desk study and Phase 2 investigation have been completed, there is always a possibility that unexpected contamination will be encountered during construction. The project programme and budget must include contingencies for dealing with unexpected contamination, including additional investigation, revised remediation, regulatory liaison, and potential delays. Projects that do not allow for contamination contingencies are vulnerable to significant cost overruns and programme delays when unexpected contamination is discovered.

4. Frequently Asked Questions

What is Part IIA of the Environmental Protection Act 1990?▾

Part IIA of the Environmental Protection Act 1990 is the primary statutory regime for dealing with land contamination in England and Wales. It was inserted into the EPA 1990 by the Environment Act 1995 and came into force in 2000. Under Part IIA, local authorities have a duty to inspect their areas to identify contaminated land, and the Environment Agency has responsibility for special sites (those affecting controlled waters or involving the most serious contamination). Land is determined as contaminated land under Part IIA if it is causing, or there is a significant possibility of it causing, significant harm to human health or significant pollution of controlled waters. The regime operates on a risk-based approach using the Source-Pathway-Receptor model. Part IIA is a regulatory backstop — the planning system is the primary mechanism for ensuring that land is made suitable for its proposed use through the development control process, where contaminated land risk assessments are required as a condition of planning permission on brownfield sites.

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