How long is a Phase I valid?

Under ASTM E1527-21 and the AAI rule, a Phase I supports CERCLA liability protection when its information was collected or updated within one year before acquisition, and five components must be no older than 180 days at closing:

1. Interviews
2. Searches for recorded environmental cleanup liens
3. Government records review
4. Site reconnaissance (the visual inspection)
5. The environmental professional's declaration

In practice the 180-day clock on those components is the binding constraint, and it runs from when each task was performed, not from the report date. A report older than 180 days but younger than one year can typically be updated by refreshing the five components rather than redone from scratch.

Deal implication: order the Phase I early enough to act on it, but mind the closing date. A report commissioned at LOI for a deal that closes nine months later will need an update. Lenders typically enforce their own currency requirements at or inside the ASTM windows, and a report that goes stale between commitment and closing is a routine, avoidable source of delay.