Aboveground Storage Tanks (ASTs)

Above Ground Storage Tank Image

General Description

Storage tanks that are aboveground, regardless of whether they are used for to store petroleum products, hazardous waste, or other hazardous material.

Summary of Federal Requirements

Aboveground storage tanks (ASTs) used for the store of petroleum products is regulated primarily under 40 CFR 112. The regulation does not actually use the terms "aboveground storage tank." Instead the term "bulk storage container" is used and is defined as "any container used to store oil. These containers are used for purposes including, but not limited to, the storage of oil prior to use, while being used, or prior to further distribution in commerce. Oil-filled electrical, operating, or manufacturing equipment is not a bulk storage container."

A bulk storage container is 55 gal. or greater and may be aboveground, partially buried, bunkered, or completely buried. "Bunkered tanks" are defined as "a container constructed or placed in the ground by cutting the earth and re-covering the container in a manner that breaks the surrounding natural grade, or that lies above grade, and is covered with earth, sand, gravel, asphalt, or other material. A bunkered tank is considered an aboveground storage container for purposes of 40 CFR 112"


A container (i.e. storage tank) cannot be used for the storage of oil unless its material and construction are compatible with the material stored and conditions of storage such as pressure and temperature.

All bulk storage container installations must be constructed so a secondary means of containment is provided for the entire capacity of the largest single container and sufficient freeboard to contain precipitation. Diked areas must be sufficiently impervious to contain discharged oil. While dikes, containment curbs, and pits are commonly employed for this purpose, an alternative system consisting of a drainage trench enclosure that must be arranged so that any discharge will terminate and be safely confined in a facility catchment basin or holding pond may also be used.

Each bulk storage container installation must be engineered or updated in accordance with good engineering practice to avoid discharges, including at least one of the following devices:

  • high liquid level alarms with an audible or visual signal at a constantly attended operation or surveillance station (NOTE: In smaller facilities an audible air vent may suffice.)
  • high liquid level pump cutoff devices set to stop flow at a predetermined container content level
  • direct audible or code signal communication between the container gauge and the pumping station
  • a fast response system for determining the liquid level of each bulk storage container such as digital computers, telepulse, or direct vision gauges (NOTE: If you use this alternative, a person must be present to monitor gauges and the overall filling of bulk storage containers.)


Control leakage through defective internal heating coils is by monitoring the steam return and exhaust lines for contamination from internal heating coils that discharge into an open watercourse, or pass the steam return or exhaust lines through a settling tank, skimmer, or other separation or retention system.

The drainage of uncontaminated rainwater is not allowed from the diked area into a storm drain or discharge of an effluent into an open watercourse, lake, or pond, bypassing the facility treatment system unless the facility:

  • normally keeps the bypass valve sealed closed
  • inspects the retained rainwater to ensure that its presence will not cause a discharge
  • opens the bypass valve and reseals it following drainage under responsible supervision
  • keeps adequate records of such events, for example, any records required under permits (i.e., NPDES).


Each aboveground container must be tested for integrity on a regular schedule, and whenever material repairs are made. The frequency of and type of testing must take into account container size and design (such as floating roof, skid-mounted, elevated, or partially buried). In July 2012 EPA released a helpful fact sheet on bulk storage container inspections.

The facility must combine visual inspection with another testing technique such as hydrostatic testing, radiographic testing, ultrasonic testing, acoustic emissions testing, or another system of non-destructive shell testing. Comparison records must be kept and the container's supports and foundations also inspected. Personnel must frequently inspect the outside of the container for signs of deterioration, discharges, or accumulation of oil inside diked areas.

Liquid level sensing devices must be regularly tested to ensure proper operation.

Effluent treatment facilities should observed frequently enough to detect possible system upsets that could cause a discharge.

If field-constructed aboveground containers undergo a repair, alteration, reconstruction, or a change in service that might affect the risk of a discharge or failure due to brittle fracture or other catastrophe, or has discharged oil or failed due to brittle fracture failure or other catastrophe, the container is evaluated for risk of discharge or failure due to brittle fracture or other catastrophe and appropriate actions taken.

Mobile/Portable AST

Mobile or portable oil bulk storage containers must be positioned or located to prevent a discharge and furnished with a secondary means of containment, such as a dike or catchment basin, sufficient to contain the capacity of the largest single compartment or container with sufficient freeboard to contain precipitation.

Regulatory Applicability

40 CFR 112 applies to petroleum oils and non-petroleum oils, animal fats and oils and greases, and fish and marine mammal oils; and vegetable oils (including oils from seeds, nuts, fruits, and kernels).

40 CFR 112 also applies to any owner or operator of a non-transportation-related onshore or offshore facility engaged in drilling, producing, gathering, storing, processing, refining, transferring, distributing, using, or consuming oil and oil products, which due to its location, could reasonably be expected to discharge oil in quantities that may be harmful, into or upon the navigable waters of the United States or adjoining shorelines, or into or upon the waters of the contiguous zone, or in connection with activities under the Outer Continental Shelf Lands Act or the Deepwater Port Act of 1974, or that may affect natural resources belonging to, appertaining to, or under the exclusive management authority of the United States (including resources under the Magnuson Fishery Conservation and Management Act) that has oil in:

  • any aboveground container
  • any completely buried tank (see definitions)
  • any container that is used for standby storage, for seasonal storage, or for temporary storage, or not otherwise "permanently closed" (see definitions)
  • any "bunkered tank" or "partially buried tank" (see definitions), or any container in a vault, each of which is considered an aboveground storage container for purposes of 40 CFR 112.)

For a PDF version of the EPA's SPCC Field Inspection and Plan Review Checklist for Onshore Facilities, click here.

Hazardous Materials Storage in ASTs

Depending on the type and amount of hazardous materials (i.e., gasoline, diesel fuel, other liquids) stored and/or used at the facility, EPA reporting requirements may apply. The regulatory impacts of hazardous materials being stored and/or used at facilities are outlined in the Laboratories -> Hazardous Materials Storage section of the Facility Regulatory Tour.

Summary of State Requirements

ASTs are primarily regulated by states. The requirements can usually found in environmental regulations and/or the fire code. There may be a requirement to paint the tank, or a fill pipe, a certain color to identify its contents, provide alarms in addition to those Federally required, and registration of the tank.

Laws and Statutes

The Clean Water Act

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