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Underground Home Heating Oil Tanks - A Citizens Guide

There are two basic types of home heating oil tanks, above ground storage tanks (AST) and underground storage tanks (UST). AST's are visible and when a leak or spill occurs it is apparent. This is not always true with UST's. Typically, these tanks are constructed of steel and can range in size from 50 gallons to 20,000 gallons. One of the greatest misconceptions is that residential heating oil UST's are regulated the same way gasoline station tanks are regulated.  Actually, home heating oil UST's are exempt from technical requirements. This means that home heating oil UST's do not have to install a leak detection device, corrosion protection or spill and overfill prevention. Owners of underground home heating oil tanks are not required to sample the soil when the system is closed out. In fact, unless there is a spill or release from the home heating oil UST, there are no reporting requirements.  

How do you know if your home has or has had a home heating oil UST?
Many times the fill cap and or the vent pipe will stick-up out of the ground. If this is not the case, you can do some investigating to determine if your home used an UST as a source of energy for heating the home. If it is a basement home, or if pipes are exposed under the home, you can follow any unknown pipes leading from the home to see if they "dead end" through an outside wall.  You can then examine the area on the outside of the home near the location of any unknown piping to see if a fill cap can be located. Fill caps are usually flush with the ground, so you may have to get your hands dirty looking for this.  Sometimes the ground is uneven in the area of UST's, either forming a depression or hump in the ground. If you are still suspicious of an area, but no fill cap can be located, you can always rent a metal detector to try and locate the tank.

What should you do with a home heating oil tank once it is located?
Home heating oil tanks are exempt from the State regulatory closure requirements. Even though a homeowner is not required to close an UST, a tank owner is advised to remove any product from the tank once it is no longer in use in order to limit the chances of a leak or spill.  It is also recommended that the tank is removed from the ground or that it is abandoned in place. A complete tank removal will give you peace of mind that impacts to the environment are no longer possible. If you select to abandon the UST in place, filling the UST with inert material such as sand, cement or foam will bind any petroleum sludge in the bottom of the tank. This will also add stability to the tank system so it will not collapse. Filling the UST with inert material will also prevent it from floating to the surface of the ground if the soil around the tank becomes unstable (such as during heavy rains or flooding).
 
What are signs of a leaking UST?
Typical signs of a spill from an UST include stains on the soil, strong petroleum odors, puddles of oil and dead vegetation around the fill or vent pipes.  This can occur when water has entered an UST. Oil is lighter than water and will float on top of the water until it exits the tank through the fill or vent pipe. 
 
Typical signs of a leak from an UST include discolored soil (greenish gray), strong petroleum odors and dead vegetation. This can occur when the metal tank corrodes and oil leaks out of the tank into the surrounding soil.  Rain water soaks into the soil. Oil is lighter than water and will float on top of the water. If the ground becomes saturated the oil may reach the surface of the ground and look very much like a spill. 
 
If you discover signs of a leak, spill or soil contamination, you are required to contact the North Carolina Department of Environment and Natural Resources (NCDENR) regional office in Mooresville, NC at (704) 663-1699.  Many spills go undetected until the removal of the tank.  
 
Why should you bother with the cost and hassle of properly abandoning a home heating oil UST system after it is no longer needed?
The cost of preventing soil and groundwater contamination is small compared to the cost of cleaning up a leak or spill from a UST. Also, lending institutions may not be willing to lend money with the property as collateral if the home heating oil UST system is not closed out properly. Lastly, real estate transactions become problematic when an old improperly abandoned UST is found on site.   If you are buying a home with a UST, check with your lending institution to see if they have additional requirements.
 
Why do UST's leak?
Typically it is a result of the steel tank or piping corroding with time. Once the steel has been corroded, the break in the system allows product to exit. Another common problem occurs when the fill pipe has been broken off. Many times this happens after it has been run over by a lawn mower or other yard equipment; other times the cap to the fill pipe has been  removed. When the fill pipe is broken or left open, rain water can enter the UST system causing the heating oil to float on the water and eventually flow out of the fill pipe to the surface of the ground. Remember, it is the homeowner's responsibility to report the spill to NCDENR.
 
If a leak occurs, who is responsible for cleaning up the contamination around the UST?
If the UST has been used on or after November 8, 1984 then the current property owner is the tank owner. If the UST was taken out of use before November 8, 1984 then the last person to use the UST is considered the tank owner. There is financial assistance for the tank owner through the North Carolina Noncommercial Leaking Petroleum UST Cleanup Fund that will pay up to one million dollars for reasonable and necessary costs directly related to the cleanup of a petroleum release from your UST, but the fund will not pay for attorney fees, tank removal costs or excessive or unnecessary work. It is important to work closely with the NCDENR regional office in Mooresville to ensure that the work is within the cleanup fund guidelines. Unfortunately leaks or spills from aboveground storage tanks are not covered by the noncommercial leaking UST cleanup fund.
 
If you are responsible for cleaning up a leak or spill from a home heating oil UST, what should you do?
First, report the contamination to the NCDENR Mooresville Regional Office at (704) 663-1699.  Soil samples may need to be taken to determine how much contamination is present. Typically, these samples need to be analyzed for total petroleum hydrocarbon concentration. Groundwater samples may also need to be taken if the water table is close to the contaminated soil. These samples must be analyzed by a certified laboratory to ensure that the sampling is completed according to NCDENR guidelines. It is recommended that a professional consultant be retained. Depending on the concentration and the extent of contamination, further assessment of the site may be necessary. The NCDENR Regional Office in Mooresville will be helpful in determining what further steps are needed. If further action is required, you will likely have to hire a professional to assess the site and clean up the contamination.
 
Where can I get more Information?
The following links can also provide useful information concerning UST's:
 


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