A Phase 1 Preliminary Risk Assessment — often called a Phase 1 desk study — is usually the first step in dealing with land contamination for a planning application. It establishes whether a site might be affected by contamination and whether any further investigation is needed, without any drilling or digging.
What a Phase 1 PRA actually is
Under the UK's Land Contamination Risk Management (LCRM) framework, the Preliminary Risk Assessment is the desk-based first stage. It gathers and reviews information about a site's history, setting and surroundings to build an initial picture of risk, and produces a conceptual site model.
What is included
- Historical map review: Ordnance Survey maps going back to the 1800s to identify former industrial uses, infilled ground, tanks, pits and other potential sources.
- Environmental and geological data: published geology, hydrogeology, licensed discharges, landfills, pollution incidents and groundwater vulnerability — usually from an environmental database report.
- Site walkover: a visual inspection recording current conditions, evidence of contamination, made ground, storage, odours or staining.
- Conceptual site model (CSM): the central output, drawing it all together.
Source, pathway, receptor
The conceptual site model is built around pollutant linkages: a source of contamination, a pathway by which it can travel, and a receptor it could harm (future residents, controlled waters, buildings or ecology). A risk only exists where all three are present and connected. Identifying — or ruling out — these linkages is the core purpose of the Phase 1.
What the assessment concludes
A Phase 1 PRA ends with one of two broad outcomes: either the risk is low enough that no further work is needed and the contamination condition can be discharged, or potential pollutant linkages exist and a Phase 2 intrusive investigation is recommended to test them. A well-evidenced Phase 1 keeps any recommended Phase 2 focused only on what the evidence actually justifies.
When you need one
A Phase 1 is commonly required for residential development, schools, nurseries, allotments and other sensitive uses, for brownfield or former industrial sites, and wherever a planning condition on land contamination has been attached to a consent.
Read next: Do I need a contaminated land assessment? or see our Phase 1 desk study service.
FAQs
Does a Phase 1 involve any digging or boreholes?
No. A Phase 1 Preliminary Risk Assessment is entirely desk-based plus a site walkover. Intrusive sampling only happens at Phase 2, if it is needed.
How long is a Phase 1 report valid?
There is no fixed expiry, but authorities may question a report that is several years old or where site conditions have changed, so it is best commissioned close to your application.
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