Aboveground storage tanks (ASTs)

Scope

Most regulations concerning ASTs are at the state level, so facilities must be sure to consult state and local agencies and regulations to ensure compliance with any unique rules regarding storage, labeling, recordkeeping, registration, and/or training. At the federal level, it is necessary to look in several different places for requirements that apply to ASTs, dependent on their function.

Regulatory citations

• 29 CFR 1910.106 — Flammable liquids.
• 40 CFR 112 — Oil Pollution Prevention
• 40 CFR 260 — Hazardous Waste Management System: General

Key definitions

• Aboveground storage tank (AST): The definition of an AST may vary depending on the federal or state regulations that apply. Federal regulations include several different descriptions of ASTs. For the purposes of waste management and/or storage, an AST is a device meeting the definition of “tank” in 40 CFR 260.10 and that is situated in such a way that the entire surface area of the tank is completely above the plane of the adjacent surrounding surface and the entire surface area of the tank (including the tank bottom) is able to be visually inspected. As it relates to the oil spill prevention regulation at 40 CFR 112, an AST may also be referred to as a “bulk storage container,” a “bunkered tank,” or a “partially buried tank,” each of which are defined in detail below.
• Bulk storage container: Any container used to store oil, including ASTs. 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. Note that oil-filled electrical, operating, or manufacturing equipment is not a bulk storage container.
• Bunkered tank: 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 (essentially, an AST) for purposes of 40 CFR 112.
• Double-walled tank: Essentially a tank within another tank, equipped with an interstitial (i.e., annular) space and constructed in accordance with industry standards. The inner tank serves as the primary storage container while the outer tank serves as secondary containment. The outer tank of a double-walled tank may provide adequate secondary containment for discharges resulting from leaks or ruptures of the entire capacity of the inner storage tank. Note: Double-walled tanks with fittings or openings (e.g. a manway) located below the liquid level of the container may require additional secondary containment to conform with industry standards and/or local codes. Moreover, a double-walled tank does not provide adequate secondary containment to address transfer-related overfills from the tank vent; therefore, secondary containment measures may be necessary to contain overfills from vents associated with transfer operations.
• Freeboard: Capacity of a secondary containment meant to hold precipitation above and beyond the capacity intended for a discharge from the largest single container. Note: Whether freeboard is “sufficient” is a matter of engineering practice that may depend on local precipitation conditions, height of the containment wall, size of the tank or container, safety considerations, and frequency of the secondary containment drainage and inspection.
• Hazardous waste: A solid waste, or combination of solid wastes, which because of its quantity, concentration, or physical, chemical, or infectious characteristics may:
  • Cause, or significantly contribute to an increase in mortality or an increase in serious irreversible, or incapacitating reversible, illness; or
  • Pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, or disposed of, or otherwise managed.
• Oil: A term that refers to oil of any kind or in any form, including, but not limited to: fats, oils, or greases of animal, fish, or marine mammal origin; vegetable oils, including oils from seeds, nuts, fruits, or kernels; and, other oils and greases, including petroleum, fuel oil, sludge, synthetic oils, mineral oils, oil refuse, or oil mixed with wastes other than dredged spoil.
• Operational life: The period beginning when installation of the tank system has commenced until the time the tank system is properly closed.
• Partially buried tank: A storage container that is partially inserted or constructed in the ground, but not entirely below grade, and not completely covered with earth, sand, gravel, asphalt, or other material. A partially buried tank is considered an aboveground storage container (essentially, an AST) for purposes of 40 CFR 112.
• Secondary containment: Temporary containment of a discharge if the primary container fails. Secondary containment gives a facility time to abate the source of the discharge and remove the accumulated chemical to prevent it from reaching waterbodies.
• Spill Prevention, Control, and Countermeasure (SPCC) Plan: The document required by 40 CFR 112.3 that details the equipment, workforce, procedures, and steps to prevent, control, and provide adequate countermeasures to a discharge of oil.

Summary of requirements

Because of the patchwork nature of federal regulation surrounding ASTs, the requirements for a given facility are highly dependent on the specific purpose(s) for that facility’s ASTs. Here are the primary requirements for common uses:

• Concerning the storage of hazardous waste in ASTs, you must look in the hazardous waste regulations (40 CFR 260 through 268) to determine what is required. Parts 262, 264, and 265 of the Resource Conservation and Recovery Act (RCRA), Subtitle C, also impact ASTs as these requirements apply to hazardous waste generators and treatment, storage, and disposal facilities. Some key things to remember:
  • For hazardous waste purposes, an AST’s entire surface area (including the tank bottom) must be able to be visually inspected.
  • Containers of hazardous waste much be clearly labeled with the words “Hazardous Waste,” a description of the contents/hazards, and the date of first accumulation.
  • Specific requirements regarding storage, recordkeeping, and training are dependent on a facility’s generator category (i.e., Very Small Quantity Generator (VSQG), Small Quantity Generator (SQG), or Large Quantity Generator (LQG)).
• If you store oil in an AST, you may be regulated under the Spill Prevention, Control and Countermeasure (SPCC) regulations at 40 CFR 112. The SPCC regulations establish procedures to prevent the discharge of oil into navigable waters. Keys to remember include:
  • Facilities covered under 40 CFR 112 have a total aggregate capacity of either 1) Aboveground oil storage greater than 1,320 gallons in containers 55 gallons or greater; or 2) Completely buried storage tanks greater than 42,000 gallons in containers 55 gallons or greater.
  • Under the oil spill prevention standards, “bulk storage containers,” “bunkered containers,” and “partially buried tanks” may be considered ASTs.
• Some ASTs fall under OSHA requirements at 29 CFR 1910.106 if they contain flammable or combustible liquids. In this case, the objective of the regulations is to protect workers from fires, rather than protecting the environment from spills. Key items to remember:
  • The rules apply to liquids with flashpoints below 200° F.
  • The distance between any two flammable liquid storage tanks shall not be less than 3 feet.
  • Every AST must have some form of construction or device that will relieve excessive internal pressure caused by exposure fires.
• Since the majority of regulations affecting ASTs are found at the state and local level, be sure to check with your state and local environmental and safety agencies to see if there are more stringent AST requirements that you need to follow.