Preliminary Risk Assessment for Development Sites
Phase 1 Desk Study
Phase 1 desk studies for planning applications, contaminated land conditions and foundation design, prepared in line with the Environment Agency’s Land Contamination Risk Management guidance.
What Is a Phase 1 Desk Study?
A Phase 1 desk study is the first stage of looking at a site before it is developed. It brings together the site’s history, geology, groundwater and the land around it to judge whether the ground could be contaminated or difficult to build on, without digging any holes.
Under the Environment Agency’s Land Contamination Risk Management guidance, known as LCRM, it is the preliminary risk assessment: the first tier of stage 1. It is also the desk study described in BS 10175, the code of practice for investigating potentially contaminated sites, and the starting point for a ground investigation under BS 5930.
One Stop Consult coordinates experienced geotechnical and environmental specialists for desk studies on houses, housing sites and commercial land, and can arrange the next stage if the site needs one.
LCRM Stage 1
What a Phase 1 Desk Study Includes
LCRM says a preliminary risk assessment should include a desk study and site walkover, an initial conceptual site model and the potential contaminant linkages. In practice that means these parts.
Site History
Historical maps and records of what the site and its surroundings have been used for, such as industry, fuel storage, filled ground or landfill.
Geology and Groundwater
The expected soils and rock, groundwater, and nearby rivers or ponds that contamination could reach.
Environmental Records
Landfill and waste sites, pollution incidents, permits and other records on and around the site.
Site Walkover
A visit to look for signs of contamination, tanks, waste or filled ground, and to check access for any later investigation.
Conceptual Site Model
How harm could happen on the site: the possible sources, the routes they could take and the people, buildings or water they could reach.
Conclusions
Whether the risk is low enough to stop there, or whether a Phase 2 investigation is needed and what it should look at.
BS 10175 was revised in 2026, its first full revision since 2011.
Desk Study With or Without a Site Walkover
LCRM’s preliminary risk assessment is a desk study and a site walkover together. Government planning guidance says that where contamination is suspected, an applicant may be required to provide at least the report of a desk study and site walkover.
A desk-only report, with no visit, can still help early on, for example when you are deciding whether to buy a site. It cannot see what is on the ground today, such as tanks, stained ground, dumped waste or recent filling, so it leaves more uncertainty.
Planning Conditions
Will the Council Accept It?
National planning policy says a site should be suitable for its proposed use, taking account of ground conditions, including land instability and contamination, and that adequate site assessment information, prepared by a competent person, should be available. That is why councils ask for desk studies.
With the Application
Where contamination is suspected, the council may ask for the desk study before it decides the planning application.
Through a Condition
Contaminated land conditions usually work in stages: finding out about the site, agreeing a remediation scheme, then carrying it out and checking it. The desk study is the first part.
Who Decides
The council decides whether the report is enough, often on the advice of its environmental health or contaminated land officer.
What Helps
Send us the exact condition wording, so the report deals with each part of it.
No one can promise that a council will accept a report, but a desk study prepared in line with LCRM and BS 10175 is what the guidance asks for. Need help with the rest of the condition? See discharge of planning conditions.
Two Purposes
Geotechnical or Geo-Environmental Desk Study?
The two look at different questions, and many sites need both.
Geo-Environmental
Looks at contamination and ground gas, to protect people, water and buildings. This is the LCRM preliminary risk assessment the council usually asks for.
Geotechnical
Looks at how the ground will behave: soils, shrinkable clay, filled ground, groundwater, slopes and past mining. It helps plan the ground investigation and the foundations.
Combined
One desk study can cover both, which suits most new-build sites where the council asks about contamination and the engineer needs ground information. For the ground investigation itself, see geotechnical site investigation.
Other Site Risks
Coal Mining, Radon and Flood Checks
A desk study can screen for these and point out where a separate report is needed.
Coal Mining
All land in the coalfield is in the Mining Remediation Authority’s Development High Risk Area or Development Low Risk Area. Most planning applications in the High Risk Area need a Coal Mining Risk Assessment. See our coal mining reports.
Radon
Approved Document C says new buildings, extensions and conversions may need protection against radon. Radon-affected areas are mapped, and BR 211 sets out the basic and full protective measures.
Flood Risk
The Environment Agency’s flood map for planning shows whether a site is in Flood Zone 1, 2 or 3. A flood risk assessment is needed in Zones 2 and 3, on sites of 1 hectare or more in Zone 1, and in some other cases. See our flood risk assessments.
The Mining Remediation Authority is the new name of the Coal Authority, since November 2024.
What Happens If a Phase 2 Is Needed?
If the desk study finds a possible risk, the next step is a Phase 2 intrusive investigation: trial pits, boreholes or window samples, with soil, water and gas testing planned around the conceptual site model. Under LCRM this is the generic and, where needed, detailed quantitative risk assessment.
If the Phase 2 confirms an unacceptable risk, a remediation strategy is agreed with the council and carried out, and a verification report then shows it was done properly.
See our site investigation and contamination reports pages for the later stages.
Information Required for a Quotation
The site address and a plan showing the boundary.
Existing and proposed plans, and what the site will be used for.
The planning reference and the wording of any condition.
Any earlier reports on the site.
Who has asked for the desk study: the council, your engineer, lender or warranty provider.
Related Services
Other Services Your Project May Require
Important Desk Study Information
A desk study is based on available records and a visual walkover. It cannot confirm the ground conditions, which only an intrusive investigation can do. Planning requirements vary between councils, and the council decides whether a report is enough to meet a condition. One Stop Consult provides consultancy and coordination support through its specialist network.
Frequently Asked Questions
Phase 1 Desk Study FAQs
What is a Phase 1 desk study?
It is a report on a site’s history, ground and surroundings, made from records, maps and a site walkover, to judge whether the ground could be contaminated or difficult to build on. It is the first stage before any digging or testing.
Is a Phase 1 Desk Study the same as a preliminary risk assessment?
Yes. Under the Environment Agency’s LCRM guidance, the preliminary risk assessment is the first tier of stage 1, and it is made up of a desk study and a site walkover with an initial conceptual site model.
Does a Phase 1 Desk Study involve digging or soil testing?
No. It uses records, maps and a visual walkover only. Trial pits, boreholes and laboratory testing belong to a Phase 2 investigation, if one is needed.
Do I need a site walkover?
If the report is for planning, yes in most cases. LCRM’s preliminary risk assessment includes a walkover, and government planning guidance says an applicant may be required to provide at least the report of a desk study and site walkover.
Will the council accept a Desk Study for a contamination condition?
The council decides, often on the advice of its contaminated land officer. A desk study in line with LCRM and BS 10175 that answers each part of the condition is what the guidance asks for. If the desk study finds a possible risk, the council will usually want the next stage before the condition is discharged.
Do I need a Phase 1 before a Phase 2?
Usually, yes. LCRM starts with the preliminary risk assessment, and the Phase 2 is planned from its conceptual site model, so the testing is aimed at the real risks on the site.
Does a Desk Study cover coal mining and radon?
It can screen for them. If the site is in the Mining Remediation Authority’s Development High Risk Area, most planning applications also need a separate Coal Mining Risk Assessment. Radon protection for new buildings is covered by Approved Document C.
What is the difference between a geotechnical and a geo-environmental desk study?
A geo-environmental desk study looks at contamination and ground gas, usually for the planning condition. A geotechnical desk study looks at how the ground will behave under the building, to help plan the ground investigation and foundations. One report can cover both.
How much does a Phase 1 Desk Study cost?
There is no fixed price. It depends on the size and history of the site and what the report is for. Send us the address, a site plan and any condition wording for a free quote.
Request Your Free Phase 1 Desk Study Quote
Complete the form below with the site address, proposed development and the reason the desk study is needed. Upload a site plan, your proposed drawings and any planning condition wording so our team can prepare an accurate quotation.
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