Phase I – desk study
Apple Environmental can assist in undertaking soil contamination and land contamination assessments. A contaminated land investigation may start or end with a desk top study, or continue on into a complete contaminated land survey with soil sampling investigation.
The main objectives of a Phase I environmental report should be to obtain information in order to:
assess the likelihood of finding contamination, its nature and extent; evaluate the environmental setting of the site and to identify sensitive receptors;
provide information from which likely contaminant-pathway-receptor relationships can be identified; and
determine the need or requirements for further investigation, by means of generic or site-specific risk assessment.
Our report therefore aims to identify any potential pollutant linkages at the site based upon current and historical use of the land and its immediate surroundings, and if appropriate, propose a sampling strategy for additional assessment or a Phase II site investigation.
The reports include:
analysis of historical mapping and archives to identify past contaminative activity and recent mapping to identify current contaminative developments;
analysis geological and hydrological mapping of the area to assess the hydrogeology beneath the site and the sites proximity to surface water;
analysis of Ordnance Survey mapping to ascertain the proximity of environmentally sensitive and protected habitats;
A site walkover to look for surface evidence of past contaminative use;
A conceptual model describing potential sources, pathways and receptors.
Risk assessment – conceptual models
The definition of what is to be regarded as being contaminated land is found in s.78 of the Environmental Protection Act 1990. There is a risk-based approach to determining whether or not land will be designated as being contaminated. In order to assess ‘risk’ we use the ‘pathway linkage concept’. This involves the requirement of a source, pathway, and receptor, where:
a source is the contamination;
a receptor is a potential target such as future users of the site, environmentally sensitive habitats, controlled waters or even a building; and
a pathway is a linkage through which a source can reach the receptor, for example windblown soil-dust linking soil contaminants to a human receptor.
Contaminated land will be defined as land where a pollutant is identified and that the pollutant has the potential to cause significant harm to receptors via a pathway. If no pathway is present linking the source to a receptor then the land is not classed as contaminated.
The ‘risk’ to a potential receptor is shown to be dependent upon is the likelihood of the occurrence multiplied by the potential hazard as is dependent upon;
- the probability of the occurrence;
- the frequency of the occurrence;
- the magnitude of the consequences; and
- the sensitivity of the receptors.
If a Phase I report identifies a potential source pathway receptor linkage, a Phase II intrusive investigation will be required.