Underground Storage Tanks

There are several issues surrounding underground fuel oil storage tanks (USTs) environmental, safety, economic and legal. Such issues have increased concerns among homeowners, home buyers, lenders and real estate agents. Among the more pressing issues involving USTs are: soil and groundwater contamination; fire risk and tank collapse; high maintenance costs; contamination cleanup; and third party damages.

The USTs that were installed in the 1970s and 1980s had been installed using old technology and with less concerns about installation and environmental issues.  Present day concerns, such as contaminated soil, may have never been anticipated. In fact, many tanks are not designed to be stored underground. Consequently, many tanks encountered today are defective by modern standards.

Leaks in USTs can be attributed to improper installation, corrosive soils, and tank and piping defects. In addition, if tanks are not carefully lowered into an excavated hole, they are susceptible to damage if they are dropped or pushed. Today, USTs generally have a corrosion-resistant exterior as well as components that deter the effects of pressure, vibration and movement.

Inside the tank, moisture in the oil encourages tank failure by enhancing corrosive action. The moisture joins with sulfur and other components in the oil to become acidic and corrosive. Water can enter the tank from an improperly sealed fill box, a missing fill pipe or vent pipe caps, loose pipe fittings, water delivered with fuel from an improperly maintained bulk storage facility and ground water seeping through a damaged tank wall.

Should I test the oil tank?

Before purchasing a home, it is strongly recommended that buried tanks be tested. The liability surrounding a leaking tank becomes the responsibility of the new owner after the property is purchased. The cost for testing a residential tank generally ranges from $350 to $500.

Vacuum based non-volumetric precision testing. EPA third party certified.

Some of the tanks testing companies utilize an EZY 3 Locator Plus. This is an ultrasonic/acoustic probe based system. All volumetric and mass measurement technology must deal with a variety of variables that do not affect this non-volumetric ultrasonic/acoustic system. The tank probes will detect any leaks or change of the static level in the tank to determine the integrity of the tank. The EZY 3 Locator Plus is capable of detecting intrusion in the liquid portion of the tank, intrusion in the area of the tank not containing liquid and intrusion into the entire tank system. Tanks are not required to have specific levels of oil, so even empty tanks can be tested. The EZY 3 Locator Plus will not damage the tank or heating system. This is not a pressure test. After a stabilization period, the ultrasonic/acoustic probe, which is set in the tank at an elevation above the liquid level, monitors the tank for indications of loss of liquid and/or a breach of integrity above the liquid level. For the customer's convenience, test results are available immediately after testing with a written report being issued the same day.

Underfilled Volumetric/Ultrasonic Testing

This test occurs with product in the tank. Testing using the underfill volumetric test pressurizes the tank with 2 psi. of compressed nitrogen. However, pressure of any nature may result in a small hole leaking in greater volume with the chance that the leak will not be detected by the test.

Volumetric Precision Testing

The oil tank is filled to 100% capacity and monitored for level changes that are adjusted for temperature induced volume changes.  The pass/fail criterion is too broad for the test results to be usable. (A leak could be present yet still fall into the acceptable range) This test is susceptible to vapor pockets which distort data and may give false results. A leak in the tank cannot be distinguished from a leak in the piping.

Tracer Tank Testing

A method where an inert gas is injected into the tank and samples of the air surrounding the tank are taken to be analyzed for the presence of the inert gas. Ten to fourteen day wait for test results. Ineffective for high water tables. Cannot distinguish a leak in the tank from a leak in the piping. Requires two visits to the property to conduct test. Test protocol has been changed numerous times to increase the reliability of the test results.

Components of Residential Underground Systems

Tank: Underground Fuel Oil Storage Tanks (USTs) are typically used in the northern regions of the nation to hold home heating fuel oil underground and out of sight.  The typical residential storage tank can hold up to 1,000 gallons and is commonly buried within 4 to 8 feet of the home's foundation walls.  Most underground tanks are typically constructed of steel. The primary concern with steel tanks is deterioration, leakage, and soil contamination surrounding the tank.

Fill Pipe: The fill pipe is the access by which the underground tank is filled with fuel oil.  The fill pipe is generally located directly above the tank.

Vent Pipe: The vent pipe provides a means for air to escape the tank when it is being filled with fuel oil.  If the tank were air tight, then it would not accept additional product.  The vent pipe may be further from the tank than the fill pipe, but usually at a location near a building where it can be supported as it is extended above ground.  The vent pipe should have a cap or some other means to prevent rainwater from entering the tank.

Supply Line: The supply line is the copper tube, which delivers the fuel oil from the underground tank to the furnace.  The supply line may run through the wall or under and up through the floor to the furnace.

What does a soil test involve?

UST Soil Test: The Underground Storage Tank (UST) soil evaluation is designed to test for total petroleum hydrocarbons (TPH) in the soil surrounding an abandoned or in-use underground oil tank.  Most states do not have regulations governing residential underground oil tanks. The evaluation is not exhaustive, and is only intended to determine if petroleum has contaminated the surrounding soil at the time of the evaluation. In instances where soil contamination has been confirmed, proper abandonment or removal of the underground tank would be needed. Removal and disposal of all contaminated soil is also paramount. A proper abandonment procedure involves pumping out any remaining fuel oil, confirming that there has been no leakage, cleaning the tank, and filling the tank with approved filler, or removing it entirely.  The only underground storage tanks that are typically recommended for abandonment in place are tanks that are under a structure or would endanger a structure if removed.

How do I know if an oil tank still exists underground?

Locating an underground oil tank is beyond the scope of a home inspection. Checking with the municipal records is the first step. If the town records state that the home was always fueled by gas, in most cases no further action would be needed. If there is no evidence of an oil tank in the records, then it would be wise to conduct an oil tank sweep of the property. Specialized companies will search or sweep the property and visually inspect the home for any signs of an oil tank.

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