Phase 2 Site Investigation
An intrusive ground investigation that collects soil, groundwater, and gas samples to characterise contamination identified in a Phase 1 desk study and inform remediation decisions.
A Phase 2 site investigation (also called a Phase 2 intrusive investigation or Phase 2 ground investigation) is the second stage of contaminated land assessment under the LCRM framework. It follows a Phase 1 desk study where potential contamination risks have been identified.
The purpose of the Phase 2 investigation is to obtain measured data from the ground to confirm or refute the pollutant linkages identified in the Phase 1 Conceptual Site Model (CSM). The investigation typically includes:
- Exploratory holes: Trial pits (typically excavated by machine to 3-4m depth) and boreholes (window sampling or cable percussion to greater depths) positioned to target areas of potential contamination identified in the desk study
- Soil sampling: Collection of soil samples from each exploratory hole for chemical analysis. Samples are collected at specific depths and from observed horizons of interest (e.g., made ground, natural ground interface, zones of discolouration or odour)
- Groundwater sampling: Installation of monitoring wells in boreholes to allow groundwater sampling. Wells are typically left for a period of equilibration before sampling
- Ground gas monitoring: Installation of gas monitoring points and repeat visits (typically 6 visits over 3 months) to measure methane (CH4), carbon dioxide (CO2), oxygen (O2), and volatile organic compounds (VOCs)
- Laboratory analysis: Submission of samples to UKAS-accredited laboratories for chemical testing against appropriate analytical suites
Results are assessed against Generic Assessment Criteria (GACs) such as those published by LQM/CIEH, or Site-Specific Assessment Criteria (SSACLs) where appropriate. The CSM is updated with measured data, and risk is reclassified.
Where contamination exceeds acceptable thresholds, the Phase 2 report will recommend a remediation strategy — which may include excavation and disposal, in-situ treatment, capping, or institutional controls.
Aegaea designs and delivers Phase 2 investigations as part of our contaminated land service, integrating contamination and geotechnical data to provide a complete picture of ground conditions.