NPL (National Priorities List)

The NPL is EPA's list of the nation's most serious known or threatened releases of hazardous substances, the sites commonly called Superfund sites. Sites most commonly reach the NPL by scoring high enough on the Hazard Ranking System after investigation under CERCLA; a state top-priority designation or a health-advisory pathway can also list a site. Listing makes it eligible for federally financed long-term remedial action.

In a Phase I ESA

ASTM E1527-21 (Table 2) requires review of NPL sites within 1.0 mile of the subject property. Of the mileage-based search distances in Table 2, only two may not be reduced by the environmental professional: this one and the federal RCRA TSD list. (Subject-property-only searches are separately non-reducible under 8.1.2.1.)

A hit within the radius does not by itself make a REC. What matters is whether the listed site could affect the subject property: distance, gradient and groundwater flow direction, the contaminants involved, and remedy status. A cross-gradient NPL site 0.9 miles away and a subject property sitting on top of an NPL groundwater plume both show up as one NPL hit in a database report. They mean very different things.

If the subject property or an adjoining property is on the NPL, the regulatory file review consideration in ASTM 8.2.3.1 applies.

Related listings

• Delisted NPL: sites removed from the NPL after cleanup objectives were met (0.5 mile search).
• SEMS: the broader EPA inventory, including sites evaluated but never listed.
• Proposed NPL: sites in the rulemaking pipeline. Data vendors typically report these with active NPL sites.

Where the data lives

EPA publishes the NPL and site profiles (documents, remedy status, contaminants) on its Superfund site search. The underlying inventory is SEMS. Data vendors resell the list geocoded in radius reports.