Environmental Series: Underground Storage Tanks for Heating Oil

An Underground Oil Tank Could be an Economic Liability for the Property Owner at the Time it is Discovered

By Jeff Sorg, OnlineEd Blog

(July 13, 2017)

canstockphoto17488720inground oil tank

There are many problems associated with underground storage tanks (USTs) for heating fuel. In the past, heating oil tanks (HOTs) were installed underground, outside and above ground or above ground in basements.

As the popularity of oil as a heating fuel decreased, so did the use of HOTs. Today, homebuilders usually don’t install oil-burning furnaces as a heat source, opting instead for natural gas or electricity to heat their homes.

In the past, unused HOTs were abandoned when a new heat source using a different fuel was installed into the home. Most of the above ground HOTs were removed and scrapped, but the majority of underground storage tanks were left in the ground to rot. Many of these abandoned USTs also contained unused heating oil.

When a UST decays, any oil left inside will leak out and contaminate the surrounding soil, surface water, and where the water table is high, the groundwater.

Underground storage tank problems become evident when a homeowner becomes aware of some heating related problem such as inconsistent or no furnace ignition that can be caused by water entering the tank and mixing with the oil. Another example of an adverse tank condition would be having to fill the tank up with fuel more often. Both of these examples mean that if water is entering the tank, then oil is likely being released from the tank.

Here are some easy things to do to investigate the possibility of a UST:

  • Look for an oil tank fill cap.
  • Look for a vent pipe.
  • Look for oil lines or signs of oil lines.
  • Contact the gas or electric company to get the start date of service for the house. If the date coincides with the date of construction, there might not be a home heating oil tank on the premises. If the date of service does not coincide with the date of construction, further research may be necessary.
  • Contact the local fire department.
  • Contact a professional locator company. A locator company will use various techniques to determine if a large metal object is present in the ground, such as the use of a metal detector.

If it is determined a tank is in use or has been abandoned, soil testing should be the next step in the investigation process. The results of the soil test will determine if an existing tank should be decommissioned and whether ground contamination cleanup will be necessary. If decommissioning is required, it will be accomplished by one of the following methods:

  • Decommission by Removal – This option requires a complete pumping out of any remaining fuel in the tank. After this step is completed, the tank may be dug up and removed. It must be disposed of in an approved disposal site. The hole will then be backfilled to grade with sand or gravel. The native soil will be placed on top of the backfill material until the hole is filled to grade. The vent pipe is removed.
  • Decommission the tank in place with Sand or P-gravel (DIP) – Tanks located under concrete, asphalt, or more than 24 inches of soil may make this method impractical. This option requires the complete pumping out of any remaining fuel in the tank. The ground is removed to the top of the tank and the top cut off. The inside of the tank is then cleaned and visually inspected for leakage. If there is no leakage, the tank will be filled with sand or p-gravel, the top then replaced, and the hole backfilled to grade. The vent pipe and fill pipe will be removed, and a certificate of decommissioning will be mailed to the owner. If there are visible signs of leakage, the homeowner will be notified.
  • Decommission in place with slurry (SLURRY) – This option requires the complete pumping out of any remaining fuel. Since an inspection of the tank is impossible with this method, soil samples should be taken to determine if there has been leakage. If there has been leakage, the remediation process should be implemented. If the tank has not leaked, then after it is empty of oil, a slurry mixture is pumped into the tank. Slurry is a sandy, ashy type of concrete. Once the tank is filled with slurry, the fill cap and vent pipe are removed.

A UST could prove to be an economic liability for the owner of the property at the time it is discovered.

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Jeff Sorg

About the Author

Jeff Sorg is a co-founder of OnlineEd®, a Web-based vocational school founded in 1997 where he also serves as Corporate Secretary, Chief Operating Officer, and School Director. Sorg holds vocational instructor licenses in Oregon, Washington, California, and Nevada and has authored numerous pre-licensing and continuing education courses. Sorg was awarded the International Distance Education Certification Center's CDEi Designation for distance education in 2008. OnlineEd® provides real estate, mortgage broker, insurance, and contractor pre-license, post-license, continuing education, career enhancement, and professional development and designation courses over the Internet.