What a Superfund site near you actually means

Superfund is the federal programme created by CERCLA in 1980 to clean up the country's worst contaminated sites and to decide who pays. The National Priorities List (NPL) is the register of sites that scored high enough on EPA's Hazard Ranking System to qualify for federally led, federally funded cleanup.

There are roughly 1,340 sites on the final NPL today, with about 460 more deleted after cleanup and a few dozen proposed. Beyond the NPL sits a much larger inventory of about 15,000 sites in EPA's Superfund enterprise system, which includes everything the agency assessed, whether or not it ever qualified for listing.

That distinction matters when reading any environmental record. A site in the wider inventory records that EPA had reason to look. A site on the NPL records that EPA looked and found something serious.

• Proposed NPL site: EPA has published its intent to list and is taking public comment. Investigation is usually still under way.
• NPL site (final): listed, and cleanup is either planned or in progress. Sites can stay in this state for decades.
• Construction complete: the engineered remedy is physically built and operating. The site stays listed while monitoring confirms the remedy works, which is why a site can be 'construction complete' and still on the NPL.
• Deleted NPL site: EPA finished the planned actions, reviewed them, and removed the site from the list. Deletion ends the federal project.

The last one is the most commonly misread. Deletion does not mean the land was restored to its original condition. It means the specific actions in the cleanup plan were completed to EPA's satisfaction. Many deleted sites carry permanent institutional controls: deed restrictions, prohibitions on digging, bans on groundwater wells, or limits on residential use.

Proximity alone tells you little, because contamination does not travel as a circle. Groundwater moves in a direction determined by geology and hydraulic gradient, so a property a mile down-gradient can be affected while one a quarter mile up-gradient is not.

Vapour intrusion changes the calculation again. Volatile compounds such as TCE and PCE can migrate through soil into buildings, and vapour issues are assessed building by building rather than by radius.

This is why any radius-based report, including ours, is a screening tool. It tells you what exists nearby and where to read further. It cannot tell you whether a specific property is affected, and no report priced for consumers can.

Every NPL site has an EPA progress profile page and a listing narrative, both linked from that site's page here. The narrative is the most useful document most people never read: it says in plain terms what the contamination is, how it got there, and what EPA found.

Look for four things. What the contaminants of concern are, because the health question is entirely different for lead than for TCE. Whether groundwater is affected and in what direction it moves. Whether a vapour intrusion pathway was evaluated. And whether institutional controls apply to the parcels around the site.

Five-year reviews are the other document worth finding. EPA revisits completed remedies on a five-year cycle, and those reports say candidly whether the remedy is still protective.

Research on proximity to contaminated sites generally finds measurable price effects that shrink with distance and fade substantially after remediation is complete and publicised. The effect is real but it is neither uniform nor permanent.

Disclosure obligations vary by state and are usually framed around what the seller actually knows, not what is discoverable in a federal database. In California, the statutory Natural Hazard Disclosure regime plus common practice means buyers routinely receive a hazard report; in most states no equivalent exists and the buyer's own diligence is the only diligence.

For a residential purchase, reading the site file and testing the specific things that apply (well water if there is a well, radon in any case, vapour if the site involves volatiles and the property is close) covers the practical ground. For a commercial purchase, the instrument is an ASTM Phase I Environmental Site Assessment performed by an environmental professional, and it is the only route to CERCLA's innocent landowner protections.