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 fist 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.
When a Phase 1 Desk Study identifies potential environmental risks, the next step is a Phase 2 Site Investigation, also called an intrusive investigation. This critical stage gathers real-world data to confirm or rule out contamination, protecting your project from unforeseen costs, planning delays, or environmental liabilities.
In this guide, we break down:
- How Phase 2 builds on Phase 1.
- The different investigation techniques (and when to use each).
- Typical timescales.
- How laboratory testing refines the site’s risk profile.
- What to expect at the end of a Phase 2 investigation.
How Phase 2 Builds on Phase 1
While a Phase 1 is based on desk research and a site walkover, a Phase 2 collects physical evidence through soil, groundwater, and ground gas sampling.
In short:
Phase 1 = Identify Potential Risks.
Phase 2 = Confirm or Dismiss Risks with Hard Data.
The findings from Phase 2 enable:
- Quantitative Risk Assessments (QRA) based on actual contamination levels.
- Decisions about whether remediation is necessary.
- Planning condition discharge if no unacceptable risks are found.
Phase 2 Site Investigation Methods
Different methods are used depending on the site, the anticipated risks, and the required depth of investigation:
- Best For: Shallow contamination, made ground assessment, visual soil profiling, locating foundations.
- Typical Depths: Up to 4 metres.
- Equipment: Mechanical excavator or hand-dug.
- Best For: Shallow contamination, installation of ground gas and groundwater wells, restricted access sites, cost-effective sampling.
- Typical Depths: Generally 5–6 metres, but can extend up to 10 metres depending on ground conditions.
- Equipment: Window sampling rig (tracked or towed).
- Best For: Deeper soils, groundwater sampling, ground gas monitoring, and collecting geotechnical data.
- Typical Depths: Up to 30 metres or more.
- Equipment: Cable percussion drilling rig.
- Best For: Hard ground, bedrock investigations, and installation of deep groundwater wells.
- Typical Depths: Up to 100 metres or more.
- Equipment: Rotary drilling rig (open hole, cored, or augered).
Tip: On smaller development sites, a combination of trial pits and window sampling often provides excellent coverage at a cost-effective price.
Types of Laboratory Testing During Phase 2
After sampling, the materials collected are sent for laboratory analysis to determine contamination levels:
- Soil Testing:
- Heavy metals (e.g., lead, arsenic)
- Hydrocarbons (TPH, PAHs)
- Asbestos in soil
- Emerging contaminants (e.g., PFAS)
- Groundwater Testing:
- Soluble contaminants (e.g., hydrocarbons, BTEX, solvents)
- Metals in solution
- PFAS detection
- Ground Gas Monitoring:
- Methane, carbon dioxide, oxygen concentrations
- Flow rates (for CS classification)
The results are then compared against appropriate assessment criteria to determine whether remediation is needed.
What Happens After Phase 2 Sampling?
1. Data Analysis and Quantitative Risk Assessment (QRA):
Risk to human health, controlled waters, or property assessed.
2. Conceptual Site Model Update:
Confirmed pollutant linkages mapped and risk-ranked.
3. Decision Point:
No significant risks: Reporting and planning condition discharge.
Significant risks: Recommend remediation (Phase 3).
Phase 1 vs Phase 2 - Quick Comparison Table
FAQs About Phase 2 Site Investigations
What happens if contamination is found in a Phase 2?
If contaminants exceed safe levels, a Remediation Strategy (Phase 3) will be needed to outline how risks will be managed.
Can a Site Investigations rule out the need for remediation?
Yes — many sites require no further action after a properly scoped Phase 2 investigation.
Is ground gas monitoring always required during a Phase 2?
Not always. It depends on the site's history, geology, and desk study findings.
Why a Clear Phase 2 Strategy Matters
A well-designed Phase 2 Site Investigation provides confidence, clarity, and control.
It ensures you're fully informed about site risks, avoids unnecessary remediation, and moves your project efficiently through planning.
At Clear Environmental, we tailor Phase 2 investigations to your site. No over-scoping, no hidden costs, just clear advice.
If your Phase 2 results raise concerns, understanding how to move forward with proportional, commercially realistic remediation is crucial.
To learn what happens next from Phase 2 to Remediation Click Here.
Related Services
What is a Phase 1 Desk Study (Preliminary Risk Assessment)?
A Phase 1 Desk Study (Preliminary Risk Assessment) is an initial environmental assessment that researches a site’s history and conditions to identify potential contamination risks.
Whether you're planning to develop land, submit a planning application, or purchase a brownfield site, understanding environmental risks early is essential.
A Phase 1 Desk Study (also called a Preliminary Risk Assessment, Contaminated Land Assessment or Land Quality Report) is the first critical step in managing those risks efficiently, helping avoid costly surprises later in your project.
This guide explains exactly what a Phase 1 involves, why it’s required, and what you can expect from the process.
What is a Phase 1 Desk Study?
A Phase 1 Desk Study is a preliminary environmental assessment that evaluates the potential for land contamination based on historical and current land uses.
It is called a “desk study” because it mainly relies on reviewing existing records and data sources, alongside a site visit.
It does not involve any intrusive ground investigation, that's reserved for Phase 2 Site Investigation if risks are identified.
In simple terms:
A Phase 1 identifies if there’s a potential problem — before you commit to site purchase, design, or construction.
Why is a Phase 1 Desk Study Needed?
A Contaminated Land Report is often required to:
- Support planning applications (especially brownfield or previously developed sites).
- Satisfy lender due diligence for property transactions.
- Manage liability and avoid unexpected abnormal costs.
- Confirm if further investigations (Phase 2) are needed.
Without a Phase 1, local authorities, insurers, and funders may refuse to progress development or financing.
Key Components of a Phase 1 Desk Study
A thorough Phase 1 typically includes:
What Does a Phase 1 Report Contain?
A typical Phase 1 Desk Study Report will include:
- Executive Summary (key findings and recommendations).
- Site location and description.
- Historical land use review (maps and aerial photography).
- Environmental setting (geology, hydrology, groundwater).
- Regulatory database review (permits, enforcement notices, pollution incidents).
- Walkover survey findings (including annotated site photos).
- Preliminary Conceptual Site Model (CSM).
- Risk assessment and clear conclusions.
- Next steps, if further investigation is needed.
At Clear Environmental, our Phase 1 reports are concise, commercially-focused, and designed to satisfy planning authorities and lenders without unnecessary complexity.
How Long Does a Phase 1 Desk Study Take?
Most Phase 1 assessments can be completed within 10 Days.
We also offer fast-track services if you’re working to tight planning or transaction deadlines.
Phase 1 Desk Study vs. Environmental Search: What's the Difference?
Key point: An Environmental Search is not a substitute for a Phase 1 — it’s simply a basic desktop screening.
Why Clear Environmental for Your Phase 1?
A Phase 1 Desk Study isn’t just a box-ticking exercise, it’s your first opportunity to manage risks, reduce abnormal development costs, and protect your investment.
At Clear Environmental, we combine technical expertise with commercial insight to deliver Phase 1 Reports that meet planning, legal, and financial requirements quickly and clearly.
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FAQs About Phase 1 Environmental Desk Studies
When should I commission a Phase 1 Environmental Report?
Ideally before site acquisition or at the earliest planning stage, so risks and costs are identified early.
Will a Phase 1 Desk Study always recommend a Phase 2 Site Investigation?
No — many sites with clean histories and no risk linkages can be signed off at Phase 1.
Who needs a Phase 1 Environmental Desk Study?
Developers, property investors, planners, architects, solicitors, and lenders commonly require Phase 1 studies.
Will the council accept my Phase 1 report for planning?
Yes — provided it follows UK guidance (such as EA Land Contamination Risk Management (LCRM)) and is prepared by qualified specialists.
What happens if my Phase 1 shows contamination risks?
We’ll outline the recommended Phase 2 site investigation scope and cost early, so you remain in control.
FAQs About Contaminated Land Assessments
What is a contaminated land assessment?
A contaminated land assessment identifies whether land poses environmental or health risks, helping manage liabilities before development or purchase.
What is the difference between Phase 1 and Phase 2?
Phase 1 is a desktop and site walkover study identifies potential risks. Phase 2 collects soil, water, and gas samples to confirm actual contamination.
How long does a Phase 1 Environmental Report and Phase 2 Site Investigation take?
A Phase 1 takes 10 days. A Phase 2 takes 4-6 weeks depending on complexity.
What happens if contamination is found during a Site Investigation?
A remediation strategy is developed to remove or manage the risks to acceptable levels.
Do I always need a Phase 2 investigation?
Not always — if Phase 1 finds no significant risks, Phase 2 may not be necessary.
FAQs About Contaminated Land Assessments
What’s a Ground Gas and Vapour Strategy (GGVS)?
A GGVS is a targeted investigation to assess the presence and risk of gases such as methane, carbon dioxide, and vapours. It typically involves installing monitoring wells, conducting several monitoring visits, and using standards like CIRIA C665 and BS8485 to determine whether protection is needed.
Do I need gas monitoring for a small extension in RBKC?
Not necessarily. If the Phase 1 Ground Gas Risk Assessment confirms no credible risk — for example, if the site is underlain by intact London Clay with no Made Ground — monitoring may not be needed. In low-risk situations, RBKC may accept the installation of basic gas protection measures with a verification statement instead.
How long does a ground gas investigation take from start to finish?
The monitoring phase typically requires 3 - 6 visits spread over a few weeks, depending on site complexity and weather pressure conditions. Including report preparation, the whole process can take around 6 - 12 weeks.
Can I reuse historical ground gas data for planning?
Yes — provided the data is recent, reliable, and representative of current conditions. Clear Environmental reviews historic site investigation records early to help reduce costs and avoid unnecessary repeat monitoring.
What happens if gas risks are confirmed?
If gas concentrations exceed safe thresholds, you’ll need to install mitigation measures such as membranes, venting layers, or structural barriers. Clear Environmental will design a practical, proportionate solution and prepare the necessary Remediation and Verification reports.
What should be included in the Ground Gas Verification Report?
The Verification Report must include photographic evidence, product specifications, a signed statement of installation quality, and confirmation that gas protection was installed in accordance with RBKC expectations. For some projects, additional tracer gas testing may be required.
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