What Is a Phase II ESA? Scope, Sampling, and What to Expect

Overview

A Phase II Environmental Site Assessment (ESA) is a subsurface investigation conducted to evaluate recognized environmental conditions (RECs) identified during a Phase I ESA. Where the Phase I is a records review and site inspection, the Phase II involves actually collecting soil, groundwater, and sometimes soil gas or indoor air samples to determine whether contamination is present and at what concentrations.

Phase II ESAs are conducted under ASTM E1903, Standard Practice for Environmental Site Assessments: Phase II Environmental Site Assessment Process. The standard provides a framework for the investigation but does not prescribe specific sampling methods, sample counts, or cleanup standards - those decisions are made by the environmental professional based on site conditions, the RECs identified, and the applicable regulatory context.

When a Phase II Is Triggered

A Phase II ESA is typically recommended when the Phase I ESA identifies one or more RECs that cannot be resolved through records review alone. Common triggers include:

• Underground storage tanks - current or former USTs identified through records, site inspection, or historical aerial photos
• Dry cleaners - current or historical dry cleaning operations (chlorinated solvent concerns)
• Auto repair and service facilities - hydraulic lifts, floor drains, waste oil storage, parts washing
• Industrial operations - manufacturing, metal finishing, chemical storage, printing
• Soil staining or distressed vegetation observed during the Phase I site inspection
• Proximity to known contamination - adjacent sites with documented releases, Superfund sites, BUSTR or VAP sites
• Fill material of unknown origin - especially at redevelopment sites

The decision to conduct a Phase II is usually driven by the Phase I consultant’s recommendation, but the client (buyer, lender, or property owner) may also adjust the scope based on their risk tolerance, transaction timeline, or regulatory requirements.

Scoping the Investigation

Starting from the Phase I

The Phase I ESA is the foundation for Phase II scope development. The RECs identified in the Phase I define what potential contaminants to investigate, where to sample, and what media (soil, groundwater, soil gas) to target. A well-written Phase I makes Phase II scoping straightforward. A vague Phase I with poorly defined RECs makes it difficult to design an efficient investigation.

Review the Phase I thoroughly before developing the Phase II work plan. Key information from the Phase I that directly informs Phase II scope:

• Location and nature of each REC
• Historical use of the property and surrounding properties
• Known regulatory status (BUSTR releases, VAP enrollments, DERR sites)
• Building age and construction type (relevant for asbestos, lead paint, vapor intrusion)
• Utility locations (important for drilling clearance)
• Geologic and hydrogeologic setting

What Gets Investigated

The investigation scope is driven by the RECs, but the environmental professional must use judgment about what contaminants are likely present based on the identified sources. Common contaminant-source relationships:

• Gas stations/USTs: BTEX, MTBE, naphthalene, TPH, PAHs, lead (older stations)
• Dry cleaners: PCE, TCE, other chlorinated solvents
• Auto repair: VOCs, metals (lead, chromium), used oil constituents, glycols
• Manufacturing: Site-specific, depends on operations. May include metals, solvents, PCBs, acids
• Fill material: Metals, PAHs, VOCs, asbestos (demolition debris)
• Agricultural land: Pesticides, herbicides, arsenic (historical arsenical pesticide use)

Client Input

The client may adjust the Phase II scope based on factors outside the Phase I findings:

• Transaction deadlines may limit the investigation to the most critical RECs
• Lender requirements may specify certain sampling standards or reporting formats
• Planned site use may dictate which exposure pathways matter (residential vs. commercial development)
• Budget constraints may require phased investigations - addressing the highest-priority RECs first

Sampling Approach

How Many Samples

There is no universal rule for sample count in a Phase II. ASTM E1903 does not specify minimum numbers. The appropriate number of samples depends on:

• The number and spatial extent of RECs being investigated
• The size of the property
• The complexity of the contamination scenario
• Whether the goal is screening (determining if contamination exists) or delineation (defining the extent)

For a screening-level Phase II at a former gas station, a typical approach might include 3-5 soil borings in the area of the former USTs and dispensers, with samples collected at multiple depth intervals and analyzed for the appropriate petroleum parameters. For a large industrial property with multiple RECs, the investigation may require dozens of borings across the site.

The goal is to collect enough data to make a defensible determination about whether contamination is present at concentrations that exceed applicable standards. If the initial screening identifies contamination, additional delineation sampling may be needed.

Soil Sampling

Soil samples are collected from borings advanced using Geoprobe (direct push), hand auger, or hollow-stem auger methods. Samples are typically collected at multiple depth intervals to characterize vertical contaminant distribution. Follow the sampling procedures appropriate for the analytes being investigated - VOC samples require special handling to minimize volatile loss, metals samples should avoid contact with metal equipment, and so on.

Field screen all samples with a PID (photoionization detector) to guide which samples are submitted to the laboratory. Visual observations (staining, odor, soil type changes) should also be documented.

Groundwater Sampling

Groundwater sampling is conducted when a REC involves a contaminant that is likely to have reached the water table, or when the applicable regulatory framework requires groundwater data. Not every Phase II requires groundwater sampling - if contamination is limited to shallow soil and the water table is deep, soil data alone may be sufficient.

When groundwater data is needed, the consultant may install:

• Temporary wells - installed during the boring program and sampled the same day or within a short window. These are common for Phase II ESAs in Ohio, especially for Ohio EPA-directed investigations. They provide screening-level groundwater data without the cost of permanent well installation, development, and multiple sampling events.
• Permanent monitoring wells - installed when long-term groundwater monitoring is anticipated or when the regulatory program requires it (e.g., BUSTR corrective action, VAP groundwater assessment). Permanent wells must be developed before sampling and require a stabilization period between development and the first sampling event.

Soil Gas and Indoor Air

If vapor intrusion is a potential concern (chlorinated solvents, petroleum VOCs near occupied buildings), soil gas or sub-slab soil gas sampling may be included in the Phase II scope. Indoor air sampling may also be warranted in some situations. These are specialized sampling methods with their own protocols and quality control requirements.

Analytical Program

The analytical methods and parameters are selected based on the contaminants of concern for each REC. Common Phase II analytical programs include:

• Petroleum sites: VOCs (EPA 8260), PAHs (EPA 8270), TPH by carbon range (EPA 8015), metals (EPA 6010/6020)
• Chlorinated solvent sites: VOCs (EPA 8260), with potential for 1,4-dioxane (EPA 8270 SIM)
• Metals sites: RCRA 8 metals or full TAL metals (EPA 6010/6020), hexavalent chromium (EPA 7196)
• Pesticide sites: Organochlorine pesticides (EPA 8081), herbicides (EPA 8151)
• Fill material: VOCs, SVOCs, metals, possibly PCBs (EPA 8082) and asbestos

All samples should be submitted to a laboratory accredited for the specific analytical methods being used.

Comparing Results to Standards

Phase II results must be compared to applicable regulatory standards to determine whether contamination exists at concentrations of concern. Which standards apply depends on why the Phase II is being conducted:

• BUSTR-regulated UST site: Compare to BUSTR closure action levels or corrective action levels
• VAP property: Compare to Ohio VAP generic numerical standards (CIDARS)
• CERCLA/Superfund screening: Compare to EPA Regional Screening Levels (RSLs)
• General due diligence: Compare to the most applicable standards for the site’s regulatory context. Many consultants use EPA RSLs as a screening benchmark when no specific regulatory program applies.
• State-directed cleanup (DERR): Compare to standards specified in the Director’s Final Findings and Orders

In Ohio, the choice of standards depends on the regulatory path the property will follow. A Phase II conducted for a real estate transaction may compare to both VAP standards and RSLs. A Phase II at a BUSTR site will use BUSTR action levels.

When multiple standards could apply, the Phase II report should clearly state which standards are being used for comparison and why.

The Phase II Report

The Phase II report documents the investigation findings and provides conclusions about whether the identified RECs represent actual environmental impacts. A complete report typically includes:

• Site background - property description, history, and summary of Phase I findings driving the investigation
• Scope of work - what was investigated, why, and how
• Field activities - boring logs, sample locations, field screening results, well construction details
• Analytical results - tabulated data with comparison to applicable standards
• Site geology and hydrogeology - soil descriptions, depth to water, groundwater flow direction (if wells were installed)
• Figures - site map with sample locations, boring log details, analytical data maps, potentiometric surface map (if applicable)
• Conclusions - whether contamination was identified, at what concentrations, in what media, and whether it exceeds applicable standards
• Recommendations - whether additional investigation, remediation, or regulatory enrollment is warranted

The Phase I ESA is a valuable reference throughout the Phase II report. Use it for site history, surrounding property information, regulatory database findings, and context for the RECs being investigated.

What Happens After the Phase II

No Contamination Found

If analytical results are below applicable standards for all media and all RECs investigated, the Phase II concludes that the identified RECs do not represent environmental impacts requiring further action. This is often sufficient to satisfy lender requirements and allow a transaction to proceed.

Contamination Found Below Action Levels

If contamination is detected but at concentrations below applicable standards, the report documents the findings and may recommend monitoring or institutional controls depending on the regulatory context and planned property use.

Contamination Found Above Action Levels

If contamination exceeds applicable standards, the report should outline the options:

• Additional investigation to delineate the extent of contamination
• Regulatory enrollment (BUSTR corrective action, VAP, DERR) depending on the source and type of contamination
• Remediation to reduce concentrations before or after property transfer
• Risk management through engineering controls, use restrictions, or environmental covenants

For real estate transactions, contamination findings affect property value, transaction terms, and allocation of cleanup responsibility between buyer and seller. The Phase II findings become the basis for negotiating environmental provisions in purchase agreements.

Source

ASTM E1903: Standard Practice for Environmental Site Assessments: Phase II Environmental Site Assessment Process. ASTM E1527-21: Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessment Process.