Phase I Environmental Desk Studies

Phase I Environmental Desk Studies

Identify Potential Sources Of Contamination, Teceptors, & Pathways

The purpose of a Phase I Environmental Desk Study is to identify any potential sources of contamination, the pathways by which the potential contamination can move around the site under investigation and those receptors that can be impacted by the potential contamination.

The relationship between a source, a pathway and a receptor is known as a pollutant linkage.

The driver behind all this is the Environmental Protection Act (1990), or more importantly Part 2A of the Act and how it has filtered down to the planning process via the National Planning Policy Framework (NPPF), Guiding Principles for Land Contamination (GPLC) 1 – 3 and Land Contamination Risk Management (LCRM).  This last one is quite important, LCRM replaced CLR11 (Contamination Land Report no.11), which was formally withdrawn in October 2020, but many consultants and Local Authorities still refer to it.

Under LCRM, an environmental desk study, preliminary environmental risk assessment, or many of the other names it can be given, which generally has the term Phase I (PI) attached to it has several elements that have to be considered.

These include, but are not limited to:

  • History of the site and its surroundings
  • History of the industrial activity in the vicinity of the site
  • Local pollutant incidents
  • Coal mining
  • Local geology
  • Local hydrology
  • Local hydrogeology
  • Regulatory held information and concerns
  • What is going to happen to the site (development plans)
  • A site reconnaissance (walkover)


Under LCRM, whilst not explicitly part of the Phase I report, consideration should also be given to unexploded ordnance (UXO) and invasive plants (Japanese Knotweed, Himalayan Balsam, Giant Hogweed, etc.).

More details of what should be included in a PI report can be found on the government website, and can be accessed via the link:

LCRM: Stage 1 risk assessment – GOV.UK (

The aim of a Phase I report is to determine a Conceptual Site Model (CSM).  Quite often this is described as a Preliminary CSM, as is based on sourced data as opposed to actual site data gained through intrusive investigations.  A CSM identified the Pollutant Linkages associated with the site under investigation and allocates a risk rating to each linkage.  GES achieves these risk ratings by applying the protocols within CIRIA Report C552 as updated by the NHBC R&D66 document which uses a risk assessment matrix of probability (likelihood) and consequence.

The majority of Phase I reports are commissioned under planning requirements and are usually conditioned under planning approvals.

This is because the NPPF says’

The minimum requirement that should be provided by an applicant is the report of a Preliminary Risk Assessment and site reconnaissance (walk-over). This will, in some cases, be sufficient to develop a conceptual model of the source of contamination and pathways by which it might reach vulnerable receptors as well as the means by which the identified pollutant linkages can be broken”. Where development is proposed, the developer is responsible for ensuring that development is safe and suitable for use for the purpose for which it is intended. The developer is thus responsible for determining whether land is suitable for a particular development or can be made so by remedial action.

However not all PI reports are commissioned via the planning process, they are also a very useful document in property transactions, site condition reporting and Due Diligence, where a basic environmental understanding of the site will assist in making a financial decision regarding a given site.

Equally, not all PI Reports are limited to environmental matters, Phase I geotechnical reports are gaining importance in determining the geotechnical suitability of a site for its development in terms of foundation suitability.

Another type of Phase I report is that of a preliminary Coal Mining Risk Assessment (CMRA) where the historical impacts of coal mining are investigated for either or both environmental and geotechnical reasons. CMRA’s are discussed separately.



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