by Larry Bily, CHMM

On October 11, 2000, several new requirements went into effect for both Small and Large Aboveground Storage Tanks. These requirements affect ASTs that store more than 250 gallons of regulated substances - e.g. mixtures or solutions that when released into the environment, present a substantial danger to the public health, welfare or the environment.


Existing Requirements

Prior to the new requirements, operators of a Small AST (21,000 gallons or less) had to comply with the following existing requirements:

Monthly leak detection
Appropriate security
Tank system labeled or marked
Monthly maintenance and operations check (documented and retained for 12 months)

New Requirements

The following additional requirements for Small ASTs went into effect on October 11th:

  • Emergency containment - the tank must have an emergency containment system that will be capable of retaining the total volume of the release for a minimum of 72 hours, and until the release can be detected and recovered.
  • The emergency containment system is most often met with a diking system or with a fabricated tank containment system.
  • The suitability of the emergency containment system will depend on how often the containment is checked for a release and on the facility’s response capabilities.
  • A certified DEP inspector shall perform an inspection of the containment system when an in-service inspection is required on the AST.

An in-service inspection is required on tanks greater than 5,000 gallons, or on tanks greater than 1,100 gallons that store a highly hazardous substance, according to the following schedule:

  • Existing tanks installed between 10/11/87 and 10/11/97 - within ten years after installation or 10/13/02, whichever is later.  
  • Existing tanks installed before 10/11/87 - by 10/11/02.  

New tanks installed after 10/11/97 - within ten years

In the future, Small ASTs will be required to have secondary containment for leak detection by October 11, 2007.


Existing Requirements

Before October 11th, operators of a Large AST (more than 21,000 gallons) had to comply with the following requirements:

Spill Prevention Response Plan
Monthly leak detection
Appropriate security
Tank system labeled or marked
Written maintenance and operations
Maintenance of required records
In-service inspection at least every five years or less based on corrosion rates

New Requirements

The following additional requirements for Large ASTs went into effect on October 11th

The tank shall have a gauge or monitoring device which must:

  • Clearly and accurately show the level in the tank;
  • Be visible to the person responsible for product deliver; and
  • Be installed, calibrated and maintained according to manufacturer's specifications.

Perform an out-of-service inspection for tanks over ten years old with unknown corrosion rates.

Future additional requirements for Large ASTs are not associated with specific dates, but are to be implemented in conjunction with major repair work:

  • Install a high-level alarm with either an automatic or a manual product shutdown at the next out-of-service inspection or major tank modification.
  • Provide emergency containment meeting regulatory technical requirements by the next out-of-service inspection.
  • Install secondary containment under the tank when the floor is replaced.
  • Complete an additional out-of-service inspection within 1/2 of the tank’s corrosion rate life, with a maximum inspection interval of twenty years.


None of the previously discussed requirements apply to several categories of storage tanks. The most common exemption is for tanks that store heating oil used on the premises. There are several types of heating oil, but the key factor is that the delivery ticket MUST say "heating oil".

Another exemption is for tanks with a capacity of 1,100 gallons or less which store motor fuels for non-commercial purposes (not for resale).


The DEP’s Bureau of Watershed Conservation released an interim policy for implementing their permit strategy for ASTs. The focus of this policy is the General Operating Permit process for large ASTs and small ASTs with capacities greater than 1,100 gallons containing highly hazardous substances.

The Division of Storage Tanks will provide written notices to owners of large ASTs who DEP records indicate have facilities that have incomplete information or lack inspection information in the DEP data system. The General Operating Permit program will be implemented over the next 18 months and will provide information the DEP needs to determine compliance with the upgrade, inspection and operational requirements.

Planned Implementation Priority

DEP plans to use the following categories to prioritize policy implementation:

  • Facilities with ASTs larger than 1,000,000 gallons. 
  • Facilities with 12 or more ASTs. 
  • Facilities with large hazardous substance ASTs. 
  • Large AST terminal facilities.  
  • Non-responders to AST notice letters. 
  • Highly hazardous substance ASTs.  All other AST facilities.

The process will continue until all 570 facilities requiring permits have been permitted.

if you have any questions, please call Larry Bily at 610-265-1510.