Environmental due diligence is a key part of buying, selling, financing, or developing commercial property. A Phase I Environmental Site Assessment (ESA) helps identify environmental conditions that could create future costs or liability.
The ASTM Phase I standard, ASTM E1527-21, was developed to make these assessments clearer and more consistent.
Although it is often called the new ASTM standard for Phase I ESA, ASTM E1527-21 was approved in 2021. As of 2026, it remains the active ASTM standard for Phase I Environmental Site Assessments. The U.S. Environmental Protection Agency (EPA) also recognizes ASTM E1527-21 as consistent with its All Appropriate Inquiries requirements.
So, what actually changed, and why does it matter for commercial real estate?
Who Should Read This Guide?
This guide may be useful for:
● Commercial property buyers and sellers
● Real estate investors
● Developers
● Banks and commercial lenders
● Attorneys involved in property transactions
● Property managers
● Companies planning mergers or acquisitions involving real estate
If environmental risk could affect your transaction, understanding the new ASTM standard can help you make better decisions.
What Is ASTM E1527-21?
ASTM E1527-21 is the current standard practice used for conducting many Phase I Environmental Site Assessments in the United States.
The main goal of a Phase I ESA is to identify Recognized Environmental Conditions, commonly called RECs, connected with a property.
The assessment may include:
● A review of the property’s historical uses
● A review of environmental databases and government records
● Interviews with owners, occupants, or other relevant parties
● A site inspection
● Review of nearby properties
● Identification of potential environmental concerns
The standard is also designed to support compliance with the EPA’s All Appropriate Inquiries (AAI) requirements. Meeting AAI requirements before purchasing a property can be important when seeking certain protections from liability under CERCLA.
What Changed Under the New ASTM Phase I Standard?
The changes under ASTM E1527-21 are not a complete redesign of the Phase I ESA process. Instead, they make several important parts of the assessment clearer.
- Clearer Definitions of Environmental Conditions
One of the biggest changes involves the way environmental conditions are classified.
The standard provides clearer guidance for:
● Recognized Environmental Conditions (RECs)
● Controlled Recognized Environmental Conditions (CRECs)
● Historical Recognized Environmental Conditions (HRECs)
These changes were made to reduce differences in how environmental professionals classify contamination and previous cleanup activities. ASTM also added guidance and examples to help professionals decide which classification is appropriate.
For buyers and lenders, this can make Phase I ESA conclusions easier to understand. - Stronger Historical Property Research
Historical research has always been an important part of a Phase I ESA.
Under the new ASTM standard for Phase I ESA, the requirements around reviewing historical information are clearer. Environmental professionals must make a stronger effort to understand how both the subject property and surrounding properties were used in the past.
This matters because a property may look clean today while still having environmental concerns linked to an older industrial or commercial use.
For example, a site that is now an office building may once have contained a dry cleaner, repair facility, manufacturing operation, or fuel storage area.
Better historical research can help uncover these hidden risks before a transaction closes. - More Detailed Site Reconnaissance
ASTM E1527-21 also strengthens expectations for the physical inspection of the property.
Environmental professionals should document relevant conditions found during the site visit. The updated reporting requirements also call for site photographs and a site map.These details make the final Phase I ESA easier for buyers, lenders, and other users to review. - Significant Data Gaps Are Easier to Identify
Sometimes important information cannot be found.
For example, historical records may be missing, access to part of a property may be restricted, or key people may not be available for interviews.
ASTM E1527-21 formally defines the concept of a significant data gap. This helps distinguish a normal lack of information from missing information that could affect the environmental professional’s ability to identify a REC.
For property buyers, this is important because not every missing record carries the same level of risk.
Phase I ESA Timing Is Now Clearer
Another important part of the new ASTM Phase I standard relates to how long a Phase I ESA remains valid.
A common mistake is assuming that the report date alone determines whether an ESA is still current.
Under ASTM E1527-21, a Phase I ESA is generally presumed viable when conducted within 180 days before the property acquisition or transaction.
Certain assessment components must be completed or updated within that 180-day period, including:
● Interviews
● Environmental cleanup lien searches
● Government record reviews
● Site and adjoining property inspections
● The environmental professional’s declaration
Other AAI components may remain usable for up to one year. This means transaction parties should look at the dates of individual assessment activities, not only the date printed on the final report.
If a real estate closing is delayed, an update may therefore be needed.
What Does the New Standard Mean for Property Buyers?
For buyers, the updated standard can improve the quality of environmental due diligence.
More consistent REC classifications and stronger documentation can make it easier to understand whether a property has:
● Current contamination concerns
● Previous contamination that has been addressed
● Ongoing environmental restrictions
● Gaps that require further investigation
● Conditions that may lead to a Phase II ESA
A Phase I ESA does not guarantee that a property is contamination-free. However, a properly completed assessment provides important information before a buyer takes ownership.
That information can influence negotiations, financing, insurance, redevelopment plans, and the decision to move forward with the transaction.
What About PFAS?
Emerging contaminants have become increasingly important in environmental due diligence.
ASTM E1527-21 discusses emerging contaminants within its broader guidance on environmental risks. Since the standard was issued, EPA has also designated PFOA and PFOS, two widely used PFAS chemicals, as hazardous substances under CERCLA.
Because ASTM E1527-21 covers CERCLA hazardous substances, environmental professionals may now need to consider potential PFOA or PFOS concerns when the history and use of a property suggest they may be relevant.
This is especially important for properties linked to certain manufacturing processes, firefighting foam use, waste handling, or other activities involving PFAS.
Why the New ASTM Standard Matters
Environmental risks are not always visible during a property tour.
Contaminated soil, groundwater impacts, underground storage tanks, past chemical releases, or nearby sources can create major financial problems after a transaction closes.
The new ASTM standard helps create a more consistent process for finding and reporting these concerns.
For investors and developers, that means better information before committing capital.
For lenders, it means clearer environmental risk documentation.
And for property owners, it can provide a better starting point for deciding whether additional investigation is necessary.
How SKA Environment Can Help
Environmental due diligence should do more than meet a lender’s checklist. It should give you useful information about the property you are considering.
SKA Environment provides Phase I Environmental Site Assessment services to help property owners, buyers, developers, and lenders identify potential environmental concerns before completing a transaction.
Our team can review property history, regulatory records, current site conditions, and surrounding environmental risks while following current ASTM Phase I ESA requirements.
If an assessment identifies concerns that require further investigation, we can also help determine the appropriate next steps.
Planning a commercial property transaction? Contact SKA Environment to discuss a Phase I ESA before you buy, finance, or develop the property.
Frequently Asked Questions
The current standard is ASTM E1527-21, Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessment Process. ASTM currently lists E1527-21 as the active version.
Not every transaction is legally required to use ASTM E1527-21. However, it is widely used for commercial real estate environmental due diligence and may be used to satisfy EPA All Appropriate Inquiries requirements.
Certain Phase I ESA components must generally be completed or updated within 180 days before acquisition. Other components may be up to one year old. The timing of the individual assessment activities is important, not simply the report date.
Usually, no. A standard Phase I ESA mainly involves records research, interviews, and visual inspection. Soil, groundwater, or other environmental sampling is generally associated with further investigation, such as a Phase II ESA.
A REC does not automatically mean a property should not be purchased. It indicates a potential environmental concern that needs to be understood. Depending on the finding, additional research, testing, risk management, or a Phase II ESA may be recommended.