Special Topics in Environmental Management

No Joke! 5 Things You Don’t Know About ASTs

The majority of aboveground storage tanks (ASTs) contain petroleum products (e.g., motor fuels, petroleum solvents, heating oil, lubricants, and used oil). Oil storage facilities with ASTs are typically found in marketing terminals, refineries, and fuel distribution centers. Storage tanks may also be found in airports, school bus barns, hospitals, automotive repair shops, military bases, farms, and industrial plants. Discharges of chemicals, petroleum, or nonpetroleum oils from storage tanks can contaminate source water. Product spilled, leaked, or lost from storage tanks may accumulate in soils or be carried away in storm runoff.

#2 State AST regulations may be more stringent than federal requirements.

State AST regulations may be more stringent or differ in other ways from the federal requirements. You must check with local regulatory authorities to make sure which ASTs are subject to what requirements.


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#3 A spill of only 1 gallon of oil can contaminate 1 million gallons of water.

Some of the causes for storage tank releases are holes from corrosion, failure of piping systems, and spills and overfills, as well as equipment failure and human operational error. The Spill Prevention Control and Countermeasures (SPCC) regulations require owners or operators of certain aboveground oil storage facilities to prepare and comply with written, site-specific, spill prevention plans:

  • Facilities with a total aboveground oil storage capacity of more than 1,320 gallons; and/or
  • Facilities with a combined underground oil storage capacity greater than 42,000 gallons.

#4 If a tank is not used for more than 1 year it is possible your state may require you to declare it as "Out of Service."

If an AST has remained out of service for a year or more, many states require owners to maintain and monitor the tank, declare the tank inactive, or remove it. If the tank is declared inactive, remove all substances from the AST system (including pipes) and completely clean the inside. Secure tanks by bolting and locking all valves, as well as capping all gauge openings and fill lines. Clearly label tanks with the date and the words “Out of Service.” Samples may be required when removing tanks to determine if any contamination has occurred. Most states require out-of-service tanks to be inspected and meet leak detection requirements before they are put back into service.


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#5 ASTs should have a secondary containment area to contain spills.

Follow standard tank filling practices when filling tanks to prevent spills and overfills. Furthermore, all ASTs should have a secondary containment area that contains spills and allows leaks to be more easily detected. The containment area surrounding the tank should hold 110 percent of the contents of the largest tank plus freeboard for precipitation. Secondary containment for ASTs must be impermeable to the materials being stored. Methods include berms, dikes, liners, vaults, and double-walled tanks. A manually controlled sump pump should be used to collect rainwater that may accumulate in the secondary containment area. Any discharge should be inspected for petroleum or chemicals before  being dispensed.

Routinely monitor ASTs to ensure they are not leaking. An audit of a newly installed tank system by a professional engineer can identify and correct problems such as loose fittings, poor welding, and poorly fit gaskets. After installation, inspect the tank system periodically to ensure it is in good condition. Depending on the permeability of the secondary containment area, more frequent containment area checks may be necessary. Areas to inspect include tank foundations, connections, coatings, tank walls, and the piping system. Integrity testing should be done periodically by a qualified professional and in accordance with applicable standards.

See tomorrow’s Advisor for additional AST prevention measures beyond secondary containment.