Why Do You Need a Phase 1 Environmental Assessment for Planning?

Planning Risks and Environmental Uncertainty

In the UK, planning applications are often held up by one common issue: uncertainty about land contamination. Whether you’re developing on a brownfield site, converting an existing building, or even extending residential property, Local Planning Authorities (LPAs) want confidence that your scheme will not pose risks to people, buildings, or the environment.

The first stage in assessing contaminated land risk is a Phase 1 Environmental Assessment (also known as a Desk Study or Preliminary Risk Assessment). It demonstrates that environmental, geotechnical and contaminated land risks have been considered, that further investigation will be undertaken where necessary, and that these risks are properly accounted for in the site design and planning process. By providing this clarity, a Phase 1 helps planning applications progress smoothly and reduces the chance of costly delays later on.

What Is a Phase 1 Environmental Assessment?

A Phase 1 Assessment is a preliminary, non-intrusive investigation. It gathers and interprets information about a site to identify potential contamination risks.

The process includes:

• Review of historical land use – old maps, aerial photographs, planning archives.
• Regulatory and environmental database searches – records of pollution incidents, landfills, industrial licences, and abstractions.
• Site walkover survey – a visual inspection to spot evidence of contamination, such as tanks, staining, or asbestos.
• Conceptual Site Model (CSM) – a structured framework showing possible pollutant linkages (sources, pathways, receptors).

The output is a formal report that highlights risks and provides clear recommendations for the planning process.

Why Is a Phase 1 Environmental Assessment Required for Planning?

1. Planning Application Validation

Many Local Authorities will not validate or determine an application until a Phase 1 report has been submitted. It demonstrates compliance with the National Planning Policy Framework (NPPF) requirement to ensure new development is suitable for its location, taking account of ground conditions and land contamination.

2. Discharge of Planning Conditions

Where contamination is suspected, LPAs routinely attach conditions to approvals. A Phase 1 is required to discharge those conditions before works can start.

3. Environmental Due Diligence

Developers and funders need early visibility of risks. Identifying contamination at Phase 1 avoids expensive surprises later and helps shape design, costing, and construction programmes.

4. Regulatory Alignment

The Environment Agency’s Land Contamination Risk Management (LCRM) framework makes the Phase 1 Preliminary Risk Assessment the mandatory first stage in contaminated land management.

What Risks Does A Phase 1 Environmental Assessment Consider?

A Phase 1 highlights issues that could impact planning, project viability, the environment or human health, including:

Historic industrial uses

Past land uses often leave behind a legacy of contamination. Former gasworks, metal foundries, tanneries, chemical plants, and petrol filling stations amongst other industrial and commercial uses can all be sources of hazardous substances. Understanding this history is essential for protecting future occupiers and meeting planning requirements.

Made ground and landfills

Areas of infilled ground, quarry backfill, or historic landfills may contain construction rubble, ash, or organic waste. These materials can generate hazardous ground gases (e.g. methane, carbon dioxide), which pose risks of explosion, asphyxiation, or structural damage.

Asbestos in soils or structures

Asbestos it is frequently found in soils as a result of demolition, fly-tipping, or historical industrial activity. Buried asbestos-containing materials (ACMs) can present significant risks to human health during groundworks. A Phase 1 flags the potential for asbestos, ensuring safe investigation, appropriate waste classification, and compliance with the Control of Asbestos Regulations.

Hydrocarbon or solvent contamination

Leaks and spills from underground storage tanks (USTs), pipelines, or industrial processes can lead to soil and groundwater contamination with petroleum hydrocarbons (diesel, petrol, oil) or solvents. These pollutants can migrate off-site, affect controlled waters, and create vapour intrusion risks inside new buildings.

Conceptual Site Models and Pathways to Sensitive Receptors

A risk only exists where there is a complete source–pathway–receptor linkage. Sensitive receptors include future site users, construction workers, neighbouring residents, buildings and services, surface waters, and aquifers. Phase 1 Assessments define these linkages through a Conceptual Site Model (CSM), guiding whether further site investigation is needed.

What are the Benefits of a Phase 1 Environmental Assessment for Developers and Planners

A well-executed Phase 1 Assessment provides clear commercial and planning advantages:

• Faster approvals – reduces queries and objections from planning officers and environmental health.
• Cost certainty – flags abnormal costs early, avoiding disruption to budgets later in the project.
• Design efficiency – informs foundation design, drainage, and the need (or not) for gas protection systems.
• Investor and lender confidence – demonstrates responsible risk management and strengthens funding applications.
• Reduced liability – protects developers from unforeseen contamination claims.

Where Does a Phase 1 Fit in the Wider Process?

A Phase 1 Environmental Assessment is the gateway into the contaminated land risk management framework set out in the UK’s Land Contamination: Risk Management (LCRM) guidance. It provides the foundation for understanding whether land contamination could affect a proposed development, and what further action is required.

The process typically follows these stages:

Phase 1 Desk Study (Preliminary Risk Assessment)

• Gathers historic mapping, aerial photographs, regulatory records, geological and hydrogeological data, and observations from a site walkover.
• Builds a Conceptual Site Model (CSM), showing potential contaminant sources, migration pathways, and receptors.
• Identifies whether there are potential pollutant linkages that warrant further investigation.

Phase 2 Intrusive Site Investigation (if required)

• Where Phase 1 identifies risks, intrusive works such as boreholes, trial pits, gas and groundwater monitoring, and laboratory testing are commissioned.
• This stage provides site-specific data to confirm or rule out contamination, refine the CSM, and quantify risks.
• The scope of Phase 2 is targeted, avoiding unnecessary cost by focusing only on the linkages identified in Phase 1.

Remediation or Mitigation Strategy (if required)

• If unacceptable risks are confirmed, a Remediation Strategy is developed.
• This may include soil excavation, treatment, or capping; groundwater remediation; or installation of protective measures such as ground gas membranes or venting layers.
• Importantly, this strategy is aligned with both planning conditions and future site use (residential, commercial, or mixed-use for example).

Verification & Long-Term Monitoring (if needed)

• Verification demonstrates that remediation or mitigation has been installed and is performing as designed.
• For example, photographic records and integrity testing of gas membranes, or laboratory testing confirmation that soils meet agreed clean-up criteria.
• Some sites also require post-construction monitoring, such as ongoing ground gas or groundwater sampling, to provide confidence to regulators and future occupiers.

Not all sites progress beyond Phase 1. In fact, for many developments, the Phase 1 concludes that contamination risks are low or negligible. In these cases:

• No further investigation is necessary.
• Planning conditions can often be discharged with the Phase 1 alone.
• Developers benefit from cost savings and reduced delays, with environmental liabilities addressed early and efficiently.

By contrast, where risks are identified, having a clear and framework ensures that issues are managed in a proportionate way. This prevents over-design, avoids unnecessary remediation, and provides confidence to both planners and investors that the site is suitable for its intended use.

Conclusion & Next Steps

A Phase 1 Environmental Assessment provides the foundation of a smooth, cost-effective development process. By identifying risks early and presenting them clearly to planners, investors, and regulators, you protect your project’s timeline, budget, and reputation.

If you’re preparing a planning application, speak to Clear Environmental today. Our team provides fast, reliable, and commercially aware Phase 1 Environmental Assessments that give you and your stakeholders complete confidence.