The standardised three-phase investigation framework used to identify, characterize, and remediate contaminated sites. Phase I is records review and reconnaissance; Phase II is intrusive sampling and analysis; Phase III is delineation and remedial design or implementation.
Phase I Environmental Site Assessment is non-intrusive: historical records, regulatory database review, aerial photography, site reconnaissance, and interviews to identify Recognized Environmental Conditions (RECs) per ASTM E1527 in the U.S. or CSA Z768 in Canada. A clean Phase I supports innocent-purchaser defences and most lending due diligence. A Phase I that finds RECs almost always triggers a Phase II.
Phase II is intrusive: boreholes, monitoring wells, soil and groundwater sampling, and laboratory analysis to confirm or refute the suspected contamination. Where vapour intrusion is a suspected pathway, Phase II scope extends to sub-slab soil gas probes and indoor air sampling, since solvents and petroleum vapours beneath occupied buildings are now treated as an urgent exposure question at many sites. Phase III, sometimes called Remedial Investigation/Feasibility Study (RI/FS) in the CERCLA context, delineates contamination extent and develops the remediation plan.
How each phase works. Phase I answers whether there is reason to suspect contamination; its output is a list of potential concerns. Phase II answers whether contamination is actually there and how it compares with the applicable standards; its output is lab data and a first site model. Phase III answers how much there is, where, and what to do about it; its output is a delineated site model, a remediation plan and, after the work, verification sampling.
In Canada, CSA Z768 sets out the Phase I approach and CSA Z769 the Phase II approach. Provinces add their own rules: Alberta uses its Tier 1 and Tier 2 guidelines, British Columbia uses the Contaminated Sites Regulation, and federal sites follow FCSAP and CCME guidance. In the United States, ASTM E1527 and E1903 cover Phase I and Phase II.
Each phase gates the next, so a disciplined Phase I and well-placed Phase II sampling keep the remediation plan focused. Nelson comes in at Phase III and remediation: the assessment data decide whether soil is treated on site by the mobile thermal fleet, treated in place with in-situ systems, or excavated and moved by Earthworks.
Also known as: ESA, Phase I ESA, Phase II ESA, Phase III ESA, environmental site assessment, phase 1 environmental site assessment, phase 2 environmental.
A Phase I ESA is a non-intrusive review of a property's environmental history: records, regulatory databases, aerial photos, site walkover, and interviews. It identifies Recognized Environmental Conditions under ASTM E1527 and is the standard due-diligence step for property transactions and lending.
Phase I is desktop research and site reconnaissance with no sampling. Phase II is intrusive: drilling, soil and groundwater sampling, and laboratory analysis to confirm whether contamination identified as a risk in Phase I is actually present.
It can and increasingly does. When volatile contaminants such as TCE, PCE, or petroleum hydrocarbons are suspected near occupied buildings, Phase II scope is extended to sub-slab soil gas probes and indoor air sampling to evaluate the vapour intrusion pathway.
Under ASTM E1527, a Phase I ESA is generally considered current for 180 days, and can be used up to one year if specific components (interviews, records review, site reconnaissance) are updated. Lenders and regulators typically require a report within these windows.
The regulatory metric for thermal destruction performance, expressed as the percentage of a target contaminant destroyed across the system. Common permit thresholds range from 99.99 percent for general hazardous organics to 99.9999 percent (six nines) for PCBs, dioxins, and PFAS.
The duration that gas, vapor, or solids remain inside the heated zone of a thermal treatment unit; together with temperature and turbulence, one of the three governing parameters of complete contaminant destruction.
Liquid that has percolated through contaminated soil, waste, or stockpiles, dissolving and carrying contaminants downward to groundwater or to a collection system. The principal migration pathway for PFAS, dissolved metals, salts, and hydrocarbons from impacted sites.
Laboratory method that oxidizes PFAS precursors in a sample into measurable perfluoroalkyl acids, then quantifies the difference against a pre-oxidation baseline. Reveals the hidden precursor mass that targeted PFAS analysis alone misses.