TankCheck / Guides

Guide 03 — Neighbors

Leaking underground storage tank next door: what it means for your property

You ran a screening and found an orange dot — a reported leak, maybe two, near your address. Before you panic (or shrug), here is how these cases actually behave, and the difference between the ones that matter and the ones that are history.

First, read the status

Every leak record in the EPA/state data carries a cleanup status, and it changes everything. "No Further Action" (NFA) or "Closed" means the state investigated, any required cleanup was done, and the file was closed — for most purposes, this is history, not hazard. An open case means investigation or cleanup is still underway: there may be monitoring wells in the sidewalk, a defined plume map, and a responsible party paying consultants. Roughly three-quarters of the half-million releases reported nationally since 1984 have been cleaned up and closed; the open ones are where your attention belongs. (Background: what a LUST site is.)

How far contamination actually travels

Petroleum releases are not radiation; they are plumes of liquid and dissolved fuel that move with groundwater and biodegrade as they go. National studies of thousands of plumes have found that most dissolved gasoline plumes stabilize within a couple hundred feet of the source, and comparatively few extend beyond about 500 feet. That is why distance bands dominate any honest screening: a leak 200 feet upgradient is a real question; the same leak 2,000 feet away rarely is. Direction matters too — groundwater flows downhill toward streams and rivers, and a plume travels with it, not against it.

The three exposure paths that matter

• Private wells. If you drink from a well and there is an open petroleum case within a quarter mile, ask the state case manager whether your well is inside the survey area, and consider testing for BTEX and MTBE (a $150–$400 lab panel). Municipal water users can generally skip this worry — utilities test constantly.
• Vapor intrusion. Petroleum vapors can migrate through soil into basements within roughly 100 feet of a source, though oxygen in the soil breaks most of it down. States screen for this in open cases; if your home is within 100 feet of an active release, ask whether a vapor assessment was done.
• Your soil, at digging depth. Relevant mainly if you are excavating — additions, pools, geothermal. Contractors hitting petroleum-stained soil must handle it as regulated waste, which turns a $10,000 dig into a $30,000 one.

Get the file — it is public

Every case in the registry has a state file: site assessments, plume maps, monitoring-well data, correspondence. It is public record, and the state UST program (contact list here) will provide it, often through an online document portal. The single most useful page is the most recent groundwater monitoring map — it shows exactly where the plume is and which direction it is moving. If your property sits outside the plume and downgradient monitoring wells are clean, you have your answer in one exhibit.

Property value and disclosure

Studies of gas-station leak sites generally find single-digit percentage impacts on nearby residential values while a case is open, fading substantially after closure. The bigger practical issue is transactional: when you sell, a diligent buyer will run the same screening you just did, so it is better to hold the NFA letter or plume map and present it than to be surprised at attorney review. Most states' seller-disclosure forms ask about known environmental conditions — a leak on a neighboring parcel that you know affects your soil or groundwater is generally disclosable; a closed case next door that never reached you generally is not. Ask your attorney, not the internet, for the line in your state.

If the case is open and close: your checklist

1. Call the state case manager (the file lists them) and ask: where is the plume, which way is groundwater flowing, is my parcel in the survey area?
2. If on well water, test it; the responsible party sometimes pays for neighbor sampling.
3. Within 100 feet? Ask about the vapor-intrusion screen.
4. Keep every letter. Documentation is worth real money at your next sale.

Frequently asked questions

Does a leaking tank next door lower my property value?

While a case is open, studies of comparable sales typically show impacts in the low single digits for nearby homes, concentrated within a few hundred feet — and the effect largely dissipates after the state closes the case. Documentation is the antidote: an NFA letter or a plume map showing your parcel clear answers the question before a buyer asks it.

Should I test my water?

If you are on municipal water, your utility already tests for petroleum compounds. If you are on a private well within about a quarter mile of an open petroleum release — especially downgradient — a BTEX/MTBE panel ($150–$400) is cheap certainty, and the state case manager can tell you whether the responsible party is funding neighbor sampling.

The leak was reported in 1989 and says 'No Further Action.' Do I care?

Mostly no. NFA means the state reviewed the case to its standards and closed it. Older closures used the standards of their day, which is worth knowing if you plan deep excavation on the boundary, but for everyday ownership and resale a decades-old closed case is background history — and very common near any commercial corridor.