The Phase 1 Desk Study is an initial risk assessment based on BS10175:2011 and CLR 11. The report may be referred to as a desk study, preliminary investigation, preliminary risk assessment or contaminated land – risk assessment. They’re all essentially the same thing and form Phase 1 of the ‘Phased Approach to Land Contamination.’ We call it a Phase 1 Preliminary Risk Assessment.
The main purpose of a Phase 1 Preliminary Risk Assessment is to collect information to enable the development of an initial conceptual site model. The conceptual model is based on the source-pathway-receptor model; where, for example, the source of contamination may be arsenic, the pathway could be ingestion of homegrown produce, and the receptor could be the inhabitant of the new dwelling. The conceptual model compares the likelihood of the source reaching the receptor, against the consequence. From this, a risk rating can be assigned which is used to determine the need for further investigation.
Information collected includes historical maps (dating back to the late nineteenth century), the geology, geochemistry, hydrogeology and hydrology of the site, current usage of the site and surrounding area, and previous site investigations pertaining to the site.
A walkover survey or ‘site reconnaissance’ also forms part of the Phase 1 Preliminary Risk Assessment and involves a visual inspection of the site to record any obvious signs of contamination (i.e. leaking oil tanks, asbestos etc). Photographs will be taken and included within the Phase 1 Preliminary Risk Assessment.
The report will make recommendations for any further investigations that may be deemed necessary as a result of the findings, and will be suitable for submission to local authority planning officers as part of the planning application for the site.