Phase 1 Desk Studies: What Planners and Developers Expect
Planning & Risk Assessment | January 2025
A Phase 1 Desk Study is often the first environmental assessment required to support planning and redevelopment. While it is a well-established process, expectations from planners and regulators have become more defined in recent years, particularly around the quality of risk assessment and clarity of reporting.
This article explains what a Phase 1 Desk Study involves, why it is required, and how a proportionate, risk-based approach can support efficient decision-making and reduce uncertainty early in a project.
What Is a Phase 1 Desk Study?
A Phase 1 Desk Study is a non-intrusive assessment that identifies potential contamination risks associated with a site. It brings together historical land use information, environmental data and site observations to develop an initial understanding of ground conditions.
The assessment typically includes:
Review of historical maps and aerial photographs
Assessment of geology, hydrogeology and hydrology
Review of environmental datasets and regulatory records
A site walkover survey, where required
Development of a preliminary Conceptual Site Model (CSM)
Identification of potential pollutant linkages
The outcome is a Preliminary Risk Assessment (PRA) that informs planning decisions and determines whether further investigation is required.
Why Do Planners Require a Phase 1 Desk Study?
Planning authorities require Phase 1 Desk Studies to:
Ensure land is suitable for its proposed use
Identify potential risks to human health and controlled waters
Determine whether intrusive investigation is necessary
Support compliance with planning policy and guidance
A well-prepared Phase 1 Desk Study provides the evidence base planners need to assess land quality and manage environmental risk at an early stage.
What Planners and Regulators Expect to See
1. A Clear, Site-Specific Risk Assessment
Generic reports are increasingly challenged. Planners expect:
A site-specific assessment based on credible data
Clear identification of potential contaminant sources
Logical assessment of pathways and receptors
The Conceptual Site Model should be clear, coherent and directly linked to the site context.
2. Proportionate Conclusions
A Phase 1 Desk Study should clearly justify whether:
No further work is required, or
A Phase 2 Site Investigation is necessary
Unnecessary recommendations for intrusive investigation can delay projects and increase costs, while insufficient assessment can result in planning refusal or additional conditions.
3. Transparent and Accessible Reporting
Reports should be:
Clearly structured and easy to follow
Written in plain, accessible language
Supported by clear figures and plans where appropriate
Planners and non-technical stakeholders should be able to understand the conclusions without specialist interpretation.
How a Risk-Based Approach Adds Value
A proportionate, risk-based Phase 1 Desk Study:
Reduces uncertainty early in the project
Supports efficient planning decision-making
Helps avoid unnecessary investigation or remediation
Provides a clear foundation for any subsequent works
By focusing on credible risks rather than hypothetical scenarios, early assessments can protect both programme and budget.
Common Issues That Lead to Delays
Some common reasons Phase 1 Desk Studies are challenged include:
Out-of-date or incomplete data sources
Lack of a clear Conceptual Site Model
Ambiguous or overly cautious conclusions
Poor linkage between assessment and recommendations
Addressing these issues at the outset helps prevent delays later in the planning process.
How Terra Environmental Delivers Phase 1 Desk Studies
Our Phase 1 Desk Studies are undertaken in accordance with recognised UK guidance, including CLR11, BS10175 and the National Planning Policy Framework.
Our approach focuses on:
Structured, evidence-based assessment
Clear identification of credible risks
Proportionate, defensible recommendations
Reporting designed to support planning and regulatory review
Each assessment is tailored to the site and proposed development, ensuring risk is properly understood and managed.
Need a Phase 1 Desk Study for Your Project?
If you are preparing a planning application or assessing a site for redevelopment, Terra Environmental can provide clear, regulator-ready Phase 1 Desk Studies to support informed decision-making.