# Oil Tank Decommissioning in Seattle

> Oil tank decommissioning in Seattle: removal or fill in place under SFD permit 6103 by ICC-certified decommissioners, records and PLIA timing. Plan the tank.

URL: https://seattleheatpumpco.com/oil-tank-decommissioning/

Updated: 2026-10-21

Oil tank decommissioning in Seattle is required once a heating oil tank has been out of service for a year or more, and it means either removing the tank or abandoning it in place under a Seattle Fire Department permit. [The Seattle Heat Pump Company](https://seattleheatpumpco.com/) coordinates tank decommissioning as part of oil-to-heat-pump projects; the decommissioning itself is performed by ICC-certified underground storage tank decommissioners, as the fire code requires.

The tank is usually the last piece of an [oil to heat pump conversion](https://seattleheatpumpco.com/oil-to-heat-pump-conversion/), and it carries more risk and paperwork than its price suggests. The method, the timing and the records all matter later, especially when the house is sold.

## What the tank assessment covers

The assessment happens alongside the [heat pump assessment](https://seattleheatpumpco.com/tools/heat-pump-assessment/) and answers four questions.

**Where is the tank, and what is it?** Basement tanks are obvious. Buried tanks usually show only a fill pipe and a vent pipe near the foundation. Seattle's fire department defines a residential heating oil tank as one of 1,100 gallons or less serving a one- to four-unit residential building, and most are far smaller.

**Has it been dealt with before?** Many houses have had more than one tank. A new tank may have replaced a buried one decades ago, and the older one may or may not have been decommissioned. The records check below answers that, and the [older homes page](https://seattleheatpumpco.com/heat-pump-older-homes/) covers the other surprises a century-old house can hold.

**Is there oil left, and any sign of a leak?** Remaining oil gets pumped out regardless. Signs worth noting include oil odor in the basement or soil, a sheen on standing water, water in the tank and unexplained jumps in oil use. None of these proves a leak by itself, which is why a suspected leak changes the method rather than the diagnosis being guessed.

**What is the access?** A tank under a lawn is a different job from one under a deck, a driveway, a side path a few feet wide or a neighbor's fence line. Access mostly matters if the tank is coming out.

## Removal or abandonment in place

Seattle's fire code allows two methods, and both are compliant.

**Abandonment in place** leaves the tank in the ground. The remaining oil and sludge are pumped out, the inside is triple rinsed, and the tank is filled with an inert solid such as sand, concrete slurry or foam. The fill and vent pipes are cut and capped. It is quicker, causes little disruption and costs less.

**Removal** takes the tank out. After pump-out, the tank is made inert so vapors cannot ignite, often with dry ice, then the piping is disconnected and drained, the soil is excavated, the tank is lifted out and hauled away, and the hole is backfilled and the surface restored. Utilities are located before any digging.

Seattle's permit records show which way owners go. Of the roughly 6,900 residential decommissioning permits issued since 2021, about 60% were abandonments in place and about 24% were removals, with the rest missing a completed report. Permits have run at about 1,000 to 1,400 a year over that period, with 1,088 in 2025. Census data puts the most oil-heated households in [West Seattle](https://seattleheatpumpco.com/service-areas/west-seattle/) and [Northeast Seattle](https://seattleheatpumpco.com/service-areas/northeast-seattle/), while permits since 2021 cluster most heavily in north Seattle ZIP codes 98115 and 98117.

The fire department's guidance shapes the choice. Tanks suspected of leaking should be removed rather than filled, and a tank abandoned in place now may later have to be removed at additional cost. Removal also exposes the soil, so it can be inspected and sampled directly. Filling in place makes sense for a sound tank in a spot where digging would mean tearing up a driveway or undermining a foundation.

## How Seattle's permit 6103 works

The decommissioning permit is Seattle Fire Department permit 6103, $184 per tank. Its rules are specific, and a decommissioner who skips them leaves you without a valid record:

- The permit is issued to the person doing the work, not the homeowner, unless the homeowner is a certified decommissioner.
- Work cannot start until the application is stamped Approved to Proceed. No permit is issued after the work is done.
- The work must be performed or directly supervised by someone certified by the International Code Council as an underground storage tank decommissioner, with a current certificate on file with the fire department, and that person must be on site for the whole operation.
- The decommissioner returns a decommissioning report to the fire department within 30 days, and you get a copy within 30 days.

The heat pump side has its own permits, covered in the [Seattle heat pump permit guide](https://seattleheatpumpco.com/guide/seattle-heat-pump-permit/). Keep the stamped tank permit, the report, receipts and photos together. Those documents are what a buyer, an inspector or a lender will ask for.

## Looking up a property's tank records

Seattle publishes its residential tank decommissioning permits as open data, searchable by address, from 1996 onward. Each record shows the permit date, the tank size where reported, the decommissioning date, the method and the company that did the work. Three things to know when reading them:

- A tank decommissioned before 1996 may have no city record at all.
- A record with incomplete tank information means the fire department never received the decommissioning report.
- More than one record at an address usually means more than one tank.

Outside Seattle, Shoreline Fire holds residential tank records for its area from January 2004 onward; earlier records sit with the cities of Shoreline, Lake Forest Park or Kenmore.

## Soil sampling, leaks and who pays

The Seattle Fire Code does not require soil samples or a site plan for either method. That surprises people, because buyers and lenders often ask for sampling. Environmental rules are separate from the fire code: if a tank has leaked, state reporting and cleanup standards can apply regardless of how the tank is decommissioned. Sampling is priced from the number of samples, the lab analysis and how the soil is reached, and is easier to do during a removal. For reference only, Oregon's Department of Environmental Quality, an out-of-state official source, cites about $200 to $300 for a residential soil test beneath a tank.

If you discover or suspect a leak, the City of Seattle advises reporting it within 24 hours to 1-800-OILS-911 and stopping any automatic oil deliveries. Cleanup is where costs become open-ended: the City of Seattle says it can exceed $10,000, and PLIA says most completed cleanups exceed $60,000.

### State insurance has ended; PLIA is the successor

Washington's no-cost heating oil insurance is closed. The policy expired June 30, 2025, and no new claims are accepted for releases reported after that date. The successor is the Pollution Liability Insurance Agency's Heating Oil Loan and Grant Program, which offers up to $75,000 per project, including grants for tank removal and cleanup and loans for heat conversion or decommissioning. It is not income-limited, but the applicant must own the property, and PLIA must approve the work before it starts. It does not reimburse completed work, so decommissioning first forfeits the money. Applications open in a limited window each year, usually in late fall, and PLIA notes longer processing times than usual. The [PLIA grant window post](https://seattleheatpumpco.com/blog/plia-heating-oil-grant-window/) tracks the dates.

## Selling a house with an oil tank

Washington's seller disclosure statute, RCW 64.06, asks whether there are substances on the property that may be environmental concerns, naming fuel or chemical storage tanks and contaminated soil or water. The same statute requires sellers to make available a notice that no-cost insurance may be available from PLIA for oil-heated properties, wording that predates the program's closure. In practice, buyers ask about tanks early. A stamped permit, the decommissioning report and photos answer most questions, and after a cleanup, a PLIA No Further Action letter can help with a future sale.

## What decommissioning costs

Filling a tank in place on a clean site typically runs about $700 to $3,000, plus the $184 Seattle Fire Department permit per tank, as, a budgeting range, not a quote. Removal is priced from the site: tank depth and size, access for excavation, what sits on top of it, disposal, backfill and restoration. Contamination found during the work changes the job entirely. The [oil conversion cost guide](https://seattleheatpumpco.com/guide/oil-to-heat-pump-conversion-cost/) shows how the tank fits into the whole project budget, and the [Seattle rebate guide](https://seattleheatpumpco.com/guide/heat-pump-rebates-seattle/) covers Clean Heat, which requires the tank to be decommissioned under fire department rules.

## Tanks outside Seattle

Suburbs run their own permits. [Bellevue](https://seattleheatpumpco.com/service-areas/bellevue/) requires a site-specific permit and an ICC-certified decommissioner, with the same removal-or-fill choice and no soil sampling requirement in its fire code guidance. Everett issues its own fire permit and also expects the report within 30 days. In [Shoreline and Lake Forest Park](https://seattleheatpumpco.com/service-areas/shoreline-lake-forest-park/), Shoreline Fire's Fire Marshal's Office issues residential tank decommissioning permits. For [Burien](https://seattleheatpumpco.com/service-areas/burien/) and unincorporated King County, the permitting authority should be confirmed with the local fire district before work is scheduled. The [heat pump versus oil furnace guide](https://seattleheatpumpco.com/guide/heat-pump-vs-oil-furnace/) helps if you are still deciding whether to convert at all.

## What's included

- Records check for earlier tank permits at the address
- Tank location, access and condition noted at the assessment
- Removal versus fill in place explained for your site
- Work performed by an ICC-certified decommissioner under SFD permit 6103
- Pump-out and disposal of remaining oil and sludge
- Cut and capped fill and vent pipes
- Decommissioning report filed with the fire department, copy to you
- Scheduling around the heat pump so the house stays heated
- Rebate and PLIA timing checked before work starts

## Removal or abandonment in place

|  | Abandon in place (fill) | Removal |
| --- | --- | --- |
| What happens | Tank pumped out, triple rinsed, filled with sand, concrete slurry or foam; pipes cut and capped | Tank pumped out, made inert, dug up and hauled away; hole backfilled and the surface restored |
| When it fits | Sound tank, no sign of a leak, hard-to-reach location | Suspected leak, a buyer or lender asks for it, or the space is needed |
| Soil visibility | Soil under the tank stays out of view | Soil around the tank can be seen and sampled |
| Price picture | About $700 to $3,000 on a clean site, plus the $184 permit | Priced from depth, size, access and restoration; no published range used here |

## Questions

### Is soil testing required when I decommission an oil tank in Seattle?

Not by the Seattle Fire Code. Soil samples and a site plan are not required for either removal or abandonment in place. Separate environmental rules can still apply if a tank has leaked, and a buyer or lender may ask for sampling, so many owners choose it. Removal makes sampling straightforward because the soil is exposed.

### Should I remove my oil tank or fill it in place?

Both are code-compliant in Seattle. Filling in place costs less and avoids digging, which suits a sound tank under a hard-to-reach spot. The fire department says suspected leaking tanks should be removed, and a tank filled now may need removal later at extra cost if a leak turns up.

### How do I find out whether my oil tank was already decommissioned?

Seattle publishes its residential tank decommissioning permits from 1996 onward, searchable by address. A record with missing details means the follow-up report was never filed. A tank decommissioned before 1996 may have no record, and Shoreline Fire holds records for its area from 2004 onward.

### Does Washington's oil tank insurance still cover leaks?

No, not for new claims. The state's heating oil insurance policy expired June 30, 2025, and no new claims are accepted for releases reported after that. Its successor is PLIA's Heating Oil Loan and Grant Program, which can fund cleanup and related work but must approve it before work starts.

### Can the tank be decommissioned before my heat pump goes in?

It can, but it is usually the wrong order. Decommissioning before PLIA approves a funded project forfeits that funding, and pumping out the oil early leaves the house without heat until the heat pump is running. Most conversions install the heat pump first, then retire the furnace and the tank.