A Phase 2 Intrusive Site Investigation is usually undertaken when information gathered from a Phase 1 Desk Study indicates that there is a potential for contamination to be present at a site.
The site investigation will usually consist of undertaking boreholes and/or trial pits in order that the soil conditions at the site can be assessed. Depending on the required depth, the boreholes will normally be undertaken using a drilling rig but can also be undertaken by hand. Soil and sometimes groundwater samples will be collected and sent to a laboratory for chemical analysis. Depending on the previous uses of the site and surrounding area, monitoring wells may be installed in order to monitor whether underground gases could present a problem to any proposed new developments at the site.
In order to decide whether the soils at the site are suitable for the proposed site end use or whether remediation is required, the results of soil analysis will be compared to Generic Assessment Criteria (GAC). GAC are concentrations of various contaminants that have been assessed as not being detrimental to health. There are specific GACs for each different type of land use (i.e. residential, commercial, industrial etc).
The results of ground gas and groundwater monitoring, if undertaken will also be assessed to determine whether remedial action is required.