Washington Department of Ecology

State of Washington Department of Ecology

The Washington Department of Ecology does not regulate the use or operation of residential heating oil tanks, like the State of Oregon does. However, some local governments may have different requirements or guidelines that may apply to residential storage tanks. Regulations and policies vary from place to place and may change from time to time.

Are there specific concerns I should have as a homeowner if I have an abandoned oil tank on my property?

  • Tanks can develop holes and release heating oil into the soil. The released oil can contaminate groundwater, surface water, storm sewers, and cause vapor problems in nearby buildings. Under the state Model Toxics Control Act, the tank owner may be held liable for damage caused by a leaking tank.
  • Corrosion can cause underground tanks to deteriorate, making cave-ins a possibility. The homeowner could be held liable for injuries caused by a cave-in.
  • Before finalizing the sale of a house, lending institutions and home buyers may want sellers to remove or “close” unused heating oil tanks. To “close” a heating oil tank, the homeowner has the tank cleaned out and filled. The tank is then left buried in the ground.
Washington Department of Ecology

Washington Department of Ecology – tank found within a backyard in Vancouver, vent pipe can be found running along the side of the house to the left of the window. The sampling of this tank resulted in a Risk Based Clean-Up.

How does Ecology prefer decommissioning take place?

Ecology recommends that the tank is removed with proper soil samples taken, and remediation, if necessary. However, decommissioning the tank in-place is also acceptable, as long as soil samples take place and remediation is completed, if necessary.

Can I decommission my tank as a homeowner?

There is no law prohibiting homeowners from doing their own decommissioning. Although, Ecology does not recommend doing the tank work yourself because of the potential safety risks. Hiring an experienced contractor is advised, as working on an underground storage tank can be dangerous. Under certain conditions, tanks can explode. Working in the excavation pit, cutting open or handling heavy tanks, and using power equipment also pose risks to the homeowner. Ecology recommends that homeowners hire an experienced contractor to perform decommissioning work.

Leaking tanks and the State of Washington Department of Ecology

What if a tank has leaked?

Knowingly using a leaking tank is negligence. If you discover that your tank is leaking you must take immediate action to stop the leak. In most cases where a tank has leaked, only the soil near the tank is affected. Sometimes, however, the heating oil may also have contaminated groundwater or surface water. It is the homeowners or contractors responsibility to:

  • Evaluate the extent of contamination caused by the leak
  • Evaluate the extent of the contamination caused by the leak
  • Determine if it is a threat to human health and the environment
  • Clean-up any contamination caused by the leak

Should I report the leak to Ecology?

Minor Leaks or Spills that affect only the soil near the residential heating oil tank do not have to reported to the Department of Ecology.   However, if the minor leak was discovered during the process of the tank being decommissioned, Ecology does recommend reporting the minor spill through the ERTS program.

Contaminated Soil above 2000 PPM does need to be reported to the Department of Ecology. Any groundwater, surface water, free product or vapor intrusion should also be noted during the reporting process.

How do I report a leak to Ecology?

All confirmed releases must be reported to the Washington Department of Ecology within 24 hours to the ERTS SYSTEM. A leak can be reported via a phone call or through the online reporting system.

Should I clean-up contamination?

Absolutely, and the Department of Ecology recommends that homeowners hire a qualified clean-up contractor to perform the remediation. When the clean-up has been completed, the contractor should give the homeowner a copy of the clean-up report. Clean-up reports of minor leaks do not need to be sent to Ecology, as they do not track or report on these clean-ups. Clean-up reports on more extensive leaks do need to be sent to the Ecology regional office, as they do keep track of and report on these sites. All reports should be kept by the homeowner for their records and the remaining life of the property.

Does the Department of Ecology have a LUST list like the State of Oregon?

Yes, it is called the Confirmed and Suspected Contaminated Site List (CSCSL). However, the majority of the sites on this list are large properties, with larger leaks (i.e. gas stations). It is extremely rare when a residential property does appear on this list, reasons that a site would appear on CSCSL is as follows:

  • When a property has been reported, but after 90 days, no closure and/or continued work to complete the remediation has taken place.
  • If groundwater has been encountered, the property automatically gets put on the CSCSL. The homeowner/contractor then has to go through the voluntary clean-up to get taken off the list. Ecology then works with the homeowner/contractor to get off the list by providing opinions on the work being completed and to verify if meets the status of no further action.

Additional Website Links:

Risk-Based Clean-Up

Risk-Based Clean-Up

Risk-Based remediation addresses the highest level of contamination from a leaking underground storage tank, with levels reported above 10,000 PPM. According to the DEQ, a risk-based clean-up offers the greatest amount of flexibility and adaptability to site-specific conditions. However, it is also the option that might require collecting additional site data and evaluation of more alternatives than a soil matrix or generic remedy clean-up. Risk-based clean-ups are the most rigorous option, with the collection of several soil samples to determine the magnitude and depth of contaminated soil, as well as how far the contamination has spread. The most important aspect of a risk-based clean-up is the evaluation of current and reasonably likely future risks to human health and the environment.

A risk-based remediation involves a soil investigation, which examines the pathways the contamination has likely spread. This pathway evaluation determines where the contaminants were released, how the contaminants can be transported to new locations and the reasonably likely ways that people may come into contact with them. Tests need to be conducted on enough samples to determine the lateral extent, as well as the depth of the petroleum contamination.

There are three investigative phases of concern while conducting a risk-based clean-up, phase two and three may not be necessary if the area of contaminated soil is limited enough in extent. Below are the steps, in order, that are required by the DEQ in order to close a risk-based clean-up:

Risk-Based Clean-Up and Free Product, Groundwater and Soil Vapor Gas

Petroleum Contaminated Soil (PCS) and/ or Free Product:

Up to seven (7) soil samples are taken to establish a representative sample and delineate the vertical and lateral extent of the pocket of petroleum-impacted soil, and potential or actual groundwater impacts. If it is determined that there is free product or large volumes of heavily contaminated soil, from which product may continue to migrate, mitigating the risk by excavation and off-site removal would be required, to the maximum extent practicable.

Risk-Based Clean-Up

Petroleum Contaminated Soil (PCS) seen during an excavation. The PCS is pictured here in the greyish color.

Risk-Based Clean-Up

The side view of the PCS, here you can see the coloration difference between the contaminated and the native soil.

Risk-Based Clean-Up

Free Product refilling into a sample boring hole

Risk-Based Clean-Up

Free Product within a sampling tube

Groundwater:

Has groundwater at the site at risk or has it been impacted by the diesel contamination?

In order to determine if groundwater has been or could be potentially encountered, a 10’ separation is required by the DEQ between the vertical extent of the contaminated soil and any potential shallow groundwater.

If there is no impact or potential impact to groundwater?

The groundwater investigation is now completed, no further action would be required.

If groundwater has been or has the potential to be impacted, what are the next steps?

A representative well will be installed in the source area to determine if groundwater has been impacted by the release. The installation of the representative well is designed to obtain a groundwater sample to measure, if any, the water level elevation in the contaminated water or soil.

If the samples in the representative well have detections that exceed the DEQs Ingestion and Inhalation from Tap Water Risk-Based Clean-Up levels, a groundwater investigation is necessary. The groundwater investigation determines the extent of the contaminated groundwater, and whether it is limited only to the property of the leaking UST or if extends to neighboring properties.

If the samples in the representative well meet the DEQ Ingestion and Inhalation from Tap Water Risk Based Clean-Up levels, no further action would be required.

The 10’ separation boring cannot be obtained due to site conditions, what happens to the investigation?

If a 10’ separation boring cannot be completed due to examples like refusal (rocky soil, etc.) or if the tank is too deep, per the DEQ a Beneficial Well Survey would need to be conducted.

A Beneficial Well Survey determines if a release of hazardous substances has impacted or has the potential to impact groundwater or surface water, through contaminant migration. These determinations will be used for evaluating exposure pathways in human health and ecological risk assessment; for identifying hot spots of contamination; and for selection or approval of remedial actions at hazardous substance clean-up sites.

The DEQ requires the survey to identify all properties that are in proximity to the site with the leaking underground storage tank, which may be utilizing a water supply well. The well may be used for drinking water, irrigation, etc. DEQ regulations considers that any well on a property that is for domestic use, be accounted for. These surveys can and are conducted within and outside city limits.

Grd Water

Groundwater encountered within an opening within an underground storage tank.

Vapor Intrusion from soil or groundwater:

Vapor intrusion is the migration of Volatile Organic Compounds (VOCs) from the subsurface into buildings. Per the DEQ, vapors released from volatile substances can be slowly released from underground spills. These volatile constituents move upward through the pores in the soil, when the soil is exposed during excavation, as well as, from contaminated groundwater. The DEQ requires Soil Vapor Gas sampling (SVGs) to assess the potential of carcinogenic vapors entering residential buildings. When certain constituents of interest, such as benzene, ethylbenzene and naphthalene concentrations exceed the DEQ Vapor Intrusion into Residential Buildings Standards, soil vapor gas sampling would be required.

To assess the potential cancer risks from vapor intrusion into homes, soil vapor gas sampling is triggered if any of the following variables apply:

  • The plume of contamination exceeds 65 cubic yards
  • There are, or likely to be, buildings within 30 feet of Volatile Organic Compounds (VOCs)
  • A 10’ separation cannot be established between the vertical extent and any potential shallow groundwater

Due to site specific factors, the number and sample locations may vary. Sampling may be conducted within the home or on the exterior of the building, either through the sub-slab and/or the soil.

Risk-Based Clean-Up

Soil Vapor Gas Sampling at the exterior of the property

Risk-Based Clean-Up

Sub-Slab Sampling, in the interior of the building

For a more in-depth overview of the DEQs requirements and standards regarding Risk-Based Clean-Up and leaking tanks, please visit their Leaking Underground Storage Tank Program (LUST site) DEQ LUST Site.

UST Soil Sampling

UST Soil Sampling Common Questions

Whether a tank search has resulted in a UST being discovered or if there is an in-service tank on the property, EcoTech highly recommends soil sampling be completed around the tank.

If you are a buyer, it is imperative for you to obtain soil samples on the underground storage tank, as once you purchase the property, you have now purchased the UST and if it is leaking, are now responsible for the clean-up.

If you are a seller or a homeowner thinking about selling, and you know you have an UST on your property, preemptive soil samples will allow you prepare for pre-inspection complications.

For more information on underground storage tanks and real estate transactions, please see the DEQ Buying or Selling guide for helpful tips DEQs Buying or Selling a Home with a UST

What if a UST is found?

Soil Samples are recommended. Per Oregon DEQ, the best way to determine if a UST has leaked, is to have soil samples collected from under each end of the tank and have the samples analyzed for diesel and heavy oil. Each sample should be analyzed at an independent laboratory that is DEQ certified.

UST Soil Sampling

UST Soil Sampling – Rendition of technician taking soil samples 12-24″ beneath an underground storage tank.

UST Soil Sampling

UST Soil Sampling – Sampling tubes filled with soil from around an underground storage tank. The soil is then placed in a jar and sent to the lab for testing.

There is an in-service tank, should I perform soil samples?

As a prospective buyer, it is essential to test a tank before purchasing the property to determine if it has leaked or is currently leaking. The current property owner is responsible for any necessary contamination clean-up from a leaking underground storage tank. Purchasing a property without testing a tank makes you, as the new property owner, liable for a prior or currently leaking UST.

I’m selling my home and the buyer has found a tank, what are the next steps for me?

EcoTech recommends that you decommission the tank and register it with DEQ. Although, through our experience, buyers and their agents will require at a minimum proof of clean soil samples.

Types of Soil Samples

What are the type of UST soil samples? 

There are three different categories that sample results can be placed into:

Non-Detect (ND)

In-service tank: samples that were analyzed have come back as non-detect and no further tests are necessary. EcoTech does recommend that the decades old tank be decommissioned and a new heat source chosen, as soon as it is practical, before the tank does leak.

Out-of-service tanks: samples that were analyzed have come back as non-detect and no further tests are necessary. EcoTech does recommend that the out-of-service tank be decommissioned within 90 days of the soil samples and registered with DEQ.

*For both the in-service and out-of-service non-detect samples that were taken from each end of the UST, does not rule out the possibility of contamination underneath the soils of the tank, that is why EcoTech recommends decommissioning of the UST.*

50 PPM (parts per million) or less

In-service tank: samples that were analyzed indicate that a leak is present. Although this is a low detection and it is not reportable to DEQ, it indicates a leak has started and should be a concern. EcoTech highly recommends that the tank be taken out-of-service and decommissioned and registered with the DEQ.

Out-of-service tank: samples that were analyzed indicate that a leak is present. Although this is a low detection and it is not reportable to DEQ, it indicates a leak has started and should be a concern. EcoTech recommends that the out-of-service tank be decommissioned and registered with DEQ.

50.1 PPM or Greater

In-service or out-of-service tanks: “The OR DEQ requires that any site where a soil sample analysis shows petroleum concentrations of 50 PPM or greater, must be reported to the DEQ within 72 hours. Remediation will be determined based on the extent of the contamination.” Simply put, the tank is leaking above the reporting limit, EcoTech is required to report the leak to the DEQ, corrective action is now needed to clean-up the site.