Debating “Adjoining” vs. “Adjacent” in an ASTM E1527-21 Phase I ESA
 

In the Phase I Environmental Site Assessment (ESA) community, which consists of users, producers, and others with an interest in ASTM International’s E1527 standard practice, there is general agreement on the definition of “contiguous” properties (as defined by the U.S. EPA’s CERCLA statute), but there has historically been some debate over the selection and use of the term “adjoining” vs. “adjacent” when referring to sites that may have impacted a subject property.

By common definition, "adjoining" implies a shared boundary or direct physical connection, while "adjacent" means nearby or next to something. In essence, adjacent things are close, but may not touch, while adjoining things always share a border or physical contact.

Within the context of E1527-21, the term “adjoining” is defined, while “adjacent” is not.

• 3.2.4 adjoining properties, n—any real property or properties the border of which is contiguous or partially contiguous with that of the subject property, or that would be contiguous or partially contiguous with that of the subject property but for a street, road, or other public thoroughfare separating them.

Within the body of the standard (excluding appendices), the defined term “adjoining” is used 26 times, and the undefined term “adjacent” is used only 5 times. The use of the undefined term “adjacent” in each of these 5 instances refers to public thoroughfares, roads, waterways, and buildings that are in proximity to but are not on the subject property. 

•  (3.2.97) “…Wastewater does not include water originating on or passing through or adjacent to a site, such as stormwater flows….”
• (9.2.5) “Adjoining properties and the surrounding area shall be observed during observation of the periphery of the subject property, from public thoroughfares adjacent to or traveled on the way to the subject property….”
• (9.2.6) “Limiting Conditions—General limitations and basis of review, including limitations imposed by physical obstructions such as adjacent buildings, bodies of water, asphalt, or other paved areas, and other physical constraints (for example, snow, rain, flooding, etc.) shall be noted….”
• (9.2.2) “Exterior…The subject property shall also be viewed from all adjacent public thoroughfares….”
• (9.4.8) “Roads—This includes roads, streets, and parking facilities on the subject property, and public thoroughfares adjacent to the subject property.”

Phase I ESAs often include references to "adjacent sites" when referring to off-site sources of releases, such as a dry cleaner, gas station, or industrial site, that may affect the subject property. In these cases, the concern is typically the release and its potential migration to the subject property, regardless of the underlying legal parcel boundaries. E1527 does not specifically address this use case for the term, but it logically falls into the same common use case as those cited above.

In 2018, the ASTM E50.02 task group responsible for the 2021 revision of the standard formed an "adjoining properties" focus group to discuss the uses of "adjoining," "contiguous," "adjacent," and "surrounding areas." The basis of the discussion was that the definition of "adjoining property" can change over time as boundaries, roads, or features change, such that sites that were historically in a "surrounding area" could become adjoining or contiguous. One suggestion from the group was to combine the concepts of adjoining and adjacent, but they quickly concluded that such a change could conflict with EPA's CERCLA landowner liability protections (including those for contiguous property owners), so it was abandoned. During an E50.02 subcommittee vote on the E1527-21 revision, a negative vote was cast to contend that the revised historical research requirements, to include historical research on the "surrounding area" and "adjacent properties" in addition to the subject property, were an overreach. Ultimately, sufficient examples were provided to support the conclusion that "surrounding" sites should be included as part of the research of the subject property, and a consensus was reached through the ASTM process.

In short, when distinguishing between contiguous, adjoining, or adjacent properties, consider a hypothetical hazardous release site. A property that directly shares a lot line, fence or wall with the hazardous release site would be considered contiguous or adjoining. The property across the street would still be considered adjoining because it shares a common street as a boundary, even though it is not in direct contact. A property a few blocks away but with the potential to affect the subject property could be considered adjacent or part of the “surrounding area” because it is nearby but not immediately touching or adjoining. 

If you have strong opinions on this topic and feel that the E1527 standard should be revised for content or clarity, then I invite you to join the new E1527 revision task group that is forming this year to deliberate on the next revision, scheduled for 2029. Contact me for more details at jim.bartlett@bureauveritas.com.