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Industry Perspective · 2026
By
, Nelson Team
October 28, 2026
EXECUTIVE SUMMARY
A Phase II environmental site assessment measures what a Phase I assessment identified as potential concerns. Boreholes, monitoring wells and laboratory analysis establish which contaminants are present, at what concentrations and across what extent. Those findings are the foundation the remediation plan stands on.
Gaps in a Phase II scope surface later as re-mobilization and resampling, so the assessment deserves the same scrutiny as the treatment it precedes. This guide explains what a Phase II program includes, how findings become a remediation plan, and what to assemble before treatment options are requested.
A Phase I environmental site assessment is a records review, site reconnaissance and interview process that identifies recognized environmental conditions without collecting samples. It can show that a property hosted a fuel outlet, a dry cleaner or an industrial operation, but it cannot say what remains in the ground or at what concentration.
A Phase II assessment follows up with intrusive investigation. Drilling and sampling programs put instruments and laboratory analysis against the specific areas of concern, and the measured results either confirm the concerns, bound them or clear them. That measured picture is what the remediation decision actually rests on.
Boreholes and monitoring wells placed against the conceptual site model and suspected source areas.
Field screening during drilling to guide sample selection and delineation.
Laboratory analysis using methods and detection limits matched to the criteria that will govern closure.
Groundwater levels and chemistry where groundwater is part of the exposure pathway.
Soil vapor sampling where volatile contaminants or vapour intrusion concerns exist.
A data quality review and a clear statement of what the sampling did and did not establish.
Detection limits deserve particular attention. If the laboratory methods cannot report below the criteria the closure process will apply, the findings leave the remediation decision ambiguous no matter how many samples were collected. Confirm the analytical methods and reporting limits before the drilling starts, not after the results arrive.
The Phase II findings feed a remediation plan in three steps. First, a conceptual site model organizes the results: sources, media, migration pathways and receptors. Second, measured concentrations are compared against the applicable jurisdictional criteria for the intended land use. Third, the areas and media above those criteria define the treatment or management scope.
Criteria basis: which jurisdictional framework and land use assumptions govern the cleanup targets.
Extent confidence: whether delineation is sufficient to estimate affected volumes, or further investigation is needed first.
Media scope: soil, groundwater, vapor and any residuals, each with its own management route.
Options: treatment onsite, treatment at an authorized facility, disposal, or risk management, compared against the same treatment boundary.
Verification: the sampling, monitoring and documentation the closure process will require.
Choosing a treatment approach
Soil remediation methods: choosing a site-specific approach
In-situ thermal remediation: heating contamination in place
Contaminated soil treatment with thermal desorption
Several Phase II gaps turn into project problems after mobilization. Insufficient delineation leaves volume estimates uncertain, which unprices excavation, transport and treatment scope. Missing co-contaminants surface when treatment or disposal criteria reject material that was scoped for one contaminant class. Unknown soil texture and moisture affect treatment performance and material handling.
Unaddressed waste classification is the most common late surprise. The receiving destination depends on the full analytical profile, not the headline contaminant, and acceptance criteria differ across facilities. Resolve classification and destination questions while the assessment is still open, using the contaminated soil disposal checklist as a working list.
In Alberta, the criteria comparison comes from the applicable Tier 1 or Tier 2 framework, with land use, soil texture and exposure pathways shaping the objectives. Oilfield-waste obligations can add separate requirements where the site history involves upstream petroleum activity, and closure runs through the remediation and reclamation certificate processes. Canadian projects in other provinces follow their own frameworks, so confirm the criteria source before scoping treatment.
Regional planning
Alberta Tier 1 and Tier 2 remediation guide
Alberta hydrocarbon remediation and Acheson-based planning
In the United States, All Appropriate Inquiries establishes the investigation standard behind landowner liability protections, and state cleanup programs set their own entry criteria and closure documentation. At underground storage tank sites, corrective-action planning evaluates treatment options against the EPA's alternative cleanup technologies guidance. Cleanup criteria and treatment operating requirements come from separate approval processes, so each needs its own evidence.
A remediation-ready scope package contains the Phase II results with detection limits, estimated affected volumes by media, soil conditions, site access constraints, the applicable criteria and the closure documentation the jurisdiction expects. With that package, treatment options can be assessed and quoted against real numbers instead of assumptions.
Nelson plans treatment scope from the site's own evidence. The Tioga pipeline spill and Bear Hills projects both show treatment following characterization: the analytical record defined the scope, and the treatment and verification followed it. Share what your assessment shows and the scope can be reviewed against it.
Procurement and next steps
Preparing a soil remediation quote request
Environmental remediation RFP guide
Contaminated soil disposal and material-management checklist
US thermal remediation and soil-management guide
Environmental remediation services across Canada and the US
Discuss the evidence and scope for your site
HOW WE KNOW THIS
This guide combines Nelson's approved service and project material with public environmental assessment guidance. It is a planning guide, not a regulatory determination, an assessment protocol or a prediction of performance. Confirm current local requirements and engage qualified environmental professionals for assessment work.
U.S. Environmental Protection Agency. All Appropriate Inquiries. https://www.epa.gov/brownfields/all-appropriate-inquiries
U.S. Environmental Protection Agency. How to evaluate alternative cleanup technologies for underground storage tank sites. https://www.epa.gov/ust/how-evaluate-alternative-cleanup-technologies-underground-storage-tank-sites-guide-corrective
Canadian Council of Ministers of the Environment. Contaminated sites guidance. https://ccme.ca/en/current-activities/contaminated-sites
Government of Alberta. Part one: Soil and groundwater remediation. https://www.alberta.ca/part-one-soil-and-groundwater-remediation
FAQ
What is a Phase II environmental site assessment?
How is a Phase II assessment different from a Phase I?
Does a Phase II report include treatment recommendations?
How many samples does a Phase II assessment need?
What should be ready before requesting remediation quotes?Current analytical results with detection limits, estimated affected volumes, soil conditions, site access constraints, applicable criteria and the closure documentation expected by the jurisdiction.
Selection and procurement
Landfill or treat on siteShould contaminated soil go to landfill or be treated on site?
Writing the specificationHow do you write a specification that requires a permanent outcome?
Alberta Tier 1 complianceWhat does Alberta Tier 1 compliance require of a vendor?
Brownfield remediationHow does a contaminated property get ready for reuse?
Read Next
Industry Perspective•2026Alberta Tier 1 Soil Remediation: Compliance and Vendor Selection
Industry Perspective•2026European BAT for Thermal Remediation: The Global Reference Standard
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A Phase II assessment collects physical samples, typically soil, groundwater and sometimes soil vapor, to confirm whether the concerns raised in a Phase I assessment are present, at what concentrations and across what extent.
A Phase I is a records review and site reconnaissance without sampling. A Phase II involves intrusive investigation, laboratory analysis and interpretation of measured concentrations against applicable criteria.
It can, but the strength of a Phase II is measurement: what is present, where and how much. Treatment selection is a separate step that weighs the findings, criteria, site constraints and verification requirements.
There is no universal number. Sampling design follows the conceptual site model, the suspected source areas, soil and groundwater conditions, and the confidence the closure process will require.