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Phase One – Desk Study and Walkover Survey
A F Howland Associates recommend that a Phase One desk study and walkover survey is carried out prior to development of any site. This consists of a review of existing geological and hydrological mapping, register searches, past editions of Ordnance Survey maps and other information systems, including Local Authority and Environment Agency records, fully supported by any anecdotal evidence. Potential hazards from ground instability, landfill activities, and historical and contemporaneous potentially contaminative activities, are also recorded. This is considered to be current best practice and the approach seeks to ensure that aspects of contamination, which are not associated with the present activities, are not overlooked.
A walk-over study would then establish the present character and condition of the area. It would be used to identify any existing features that can be correlated with past activity.
This information is collated to provide a ‘Preliminary Conceptual Model’. This establishes the potential for contamination and the risk to a range of ‘targets’ by using the ‘source-pathway-receptor’ principle outlined in Planning Policy Statement 23 (PPS23). This principle allows a qualitative risk assessment to be carried out for the site and is essential when designing a site specific, Phase Two, intrusive investigation which may be warranted where the site is identified as potentially contaminated by the Phase One investigation.
Current legislation requires Phase One surveys to be completed for many developments as part of the planning process. The Local Planning Authorities (LPAs) have a duty under Part 2A of the Environmental Protection Act of 1990 to identify, investigate and acquire remediation of sites within their area if it is considered potentially contaminated.