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Automatic Tank Gauging Systems

How does the release detection method work?

This method uses automated processes to monitor product level and inventory control. A probe permanently installed in the tank is connected to a monitor to provide information on product level and temperature. These systems calculate changes in product volume that can indicate a leaking tank. Automatic tank gauging systems (ATG systems) operate in one of two modes: inventory mode and leak detection mode. In the leak detection mode, ATG systems can be set manually or automatically to perform a leak test. Manual leak tests are in-tank static tests and automatic leak tests are continuous in-tank leak detection tests. When we refer to ATG systems we are referring to testing performed in the in-tank static test mode. ATG systems operating in continuous in-tank leak detection test mode are covered under Continuous In-Tank Leak Detection.

Features of ATG systems include:

What are the regulatory requirements?

The ATG system must be able to detect a leak no larger than 0.2 gallon per hour with certain probabilities of detection and false alarm. Some ATG systems can also detect a leak of 0.1 gallon per hour with the required probabilities.

Beginning on October 13, 2018 you must perform the following, as applicable, on your release detection equipment annually to make sure it is working properly:

Testing must be performed in accordance with manufacturer’s requirements; a nationally recognized code of practice; or requirements determined by your implementing agency to be no less protective of human health and the environment.

Will it work at your site?

ATG systems have been used primarily on tanks containing gasoline or diesel. If considering using an ATG system for larger tanks or products other than gasoline or diesel, discuss its applicability with the manufacturer or installer.

Anything else you should consider?

Will you be in compliance?

For USTs installed April 11, 2016 owners and operators may use ATG systems as their primary method of release detection. When installed and operated according to the manufacturer's specifications, ATG systems meet the federal release detection requirements. USTs installed or replaced after April 11, 2016 may no longer use ATG systems (used solely for in-tank release detection) as the primary method of release detection. USTs must be secondarily contained and use interstitial monitoring.

View EPA's publication, Automatic Tank Gauging Systems for Release Detection: Reference Manual for Underground Storage Tank Inspectors, for information on evaluating how well UST owners and operators are using their ATG systems to comply with release detection requirements.

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