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N.C. Department of Environment and Natural Resources

NC Department of Environment and Natural Resources
Environmental Assistance and Customer Service - Spills

Environmental Assistance and Customer Service

Aboveground Storage Tanks

This website on aboveground storage tanks (ASTs) is designed to address the issues of small tanks, defined as having a capacity of less than 550 gallons, that are used to hold oil products for farms, small businesses and residential heating and cooking.

Click here to read our AST fact sheet!

A spill of only one gallon of oil can contaminate one million gallons of water.

 Common Causes of Spill and Leaks

Storms

High winds and rising water from hurricanes and other storms can cause tanks to move off their support pad, or otherwise be separated from the fuel line, causing spills.

Prevention Tip

Properly locate tanks away from flood plains and install tank tie-downs. Especially in coastal areas, ensure the system chosen is sufficient to hold the tank in place, or contact a certified vendor for assistance.

Improperly Secured Tanks

ASTs that are improperly secured to their foundations and mounts can slowly turn or roll. A wedge or block is not adequate support.

Prevention Tip

Make sure ASTs are secured to the stand or foundation with proper tie-downs. Do not lean or stack materials against a tank. Avoid locations that might experience heavy vibrations from nearby traffic.

Tank Failure

Condensation and bacteria inside a tank can corrode the tank, causing leaks or tank failure.

Prevention Tip

Condensation can be minimized by keeping the tank full and painting exterior tanks a light color to reflect the sun and prevent overheating. This has the added benefit of minimizing emissions. Commercial fuel treatments are available to reduce tank corrosion. Regularly inspect ASTs for leaks and replace ASTs as needed. New types of approved corrosion-proof ASTs are on the market today. A tank that is more than 25 years old is a candidate for replacement.

Tank Support Failure

Tanks can topple over or collapse due to rust, loose fittings and nuts, or poor tank foundations that have eroded or settled. In basements, moisture, such as condensation, can rust metal legs or rot wood supports.

Prevention Tip

Simple periodic inspections can ensure the integrity of the AST. Check to ensure the stand, slab and foundation are still in good condition and can support weight.

Equipment Failure

Settling of a tank or its foundation can bend the tank or fuel line.

Prevention Tip

Well-designed ASTs use gravity feed and have shutoff valves at the tank or in the fuel line. Fuel lines and any associated pumps or valves should be included in all tank inspections. AST shutoff valves should be located where they can be easily found and used in an emergency or for maintenance.

Spills and Overfills

Spills often occur during the filling process. Overfilling can causeproduct loss through the safety valve as the product expands onwarm days. Overfills need to be contained and cleaned up as soon as possible to prevent contamination.

Prevention Tip

A simple tank overfill alarm can prevent overfilling. Keep the AST easily accessible and clear of obstructions for the delivery truck operator.

Buried Feed Lines

AST fuel lines are commonly buried in or under cement floors and foundations. The lime from cement can chemically react with copper lines and deteriorate over time. AST leaks under cement floors are difficult to detect and expensive to fix.

Prevention Tip

Consider replacing any copper fuel lines that are in contact with cement with lines that are in a protective sleeve, or relocate the lines above ground where leaks can be more easily detected.

Accidents

ASTs can be damaged when bumped by a vehicle or by vibrations from heavy foot or vehicle traffic. Heavy items stored near a tank could shift and cause damage. Vandalism can also be a concern.

Prevention Tip

Crash posts or earthen berms can prevent vehicle accidents. Areas around USTs should be kept clear and protected to allow regular inspections and prevent accidents or vandalism.

A single pint of oil released into a water body can cover an acre of surface area and seriously damage aquatic habitats.

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