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Detecting UST Releases

Why is release detection crucial?

All regulated tanks and piping must have release detection so that releases are discovered quickly before contamination spreads from the UST site. You must provide your UST system with release detection (often also called leak detection) that allows you to meet three basic requirements:

  1. You can detect a release from any portion of the tank or its piping that routinely contains petroleum;
  2. Your release detection is installed and calibrated in accordance with the manufacturer's instructions; and
  3. Your release detection meets the performance requirements described in the federal regulations (sections 280.43, 280.44, or subpart K as applicable).
The release detection requirements are summarized in the table below:

Notes: Release detection requirements for previously deferred UST systems are discussed here. We use the term monthly (month). This term means at least once every 30 days.

Release Detection Requirements
UST System Component Release Detection Method
Tanks
2 Choices for tanks installed on or before April 11, 2016
  1. Monthly Monitoring*; or
  2. Monthly Inventory Control and Tank Tightness Testing Every 5 Years. Few tanks can use this option. Tanks installed on or before October 13, 2015 may be able to use this option for 10 years after installing a new UST or upgraded UST with corrosion protection. After this 10 year period, monthly monitoring is required.
Tanks installed or replaced after April 11, 2016

Secondary Containment with Interstitial Monitoring

Pressurized Piping
Choice of one from each set A & set B for piping installed on or before April 11, 2016:

Set A. Use an automatic line leak detector that:

  1. Shuts Off Product Flow -or-
  2. Restricts Flow -or-
  3. Triggers Audible Or Visual Alarm
-AND- Set B.
  1. Annual Line Testing -or-
  2. Monthly Monitoring* (except automatic tank gauging systems)
Pressurized Piping installed or replaced after April 11, 2016:

Use an automatic line leak detector that:

  1. Shuts Off Product Flow -or-
  2. Restricts Flow -or-
  3. Triggers Audible Or Visual Alarm

-AND-

Secondary Containment with Interstitial Monitoring

Suction Piping
3 Choices for piping installed on or before April 11, 2016
  1. Monthly Monitoring* (except automatic tank gauging); or
  2. Line Testing Every 3 Years; or
  3. No Requirements IF the following characteristics are readily determinable:
    • Below-grade piping is sloped so that its contents will drain back into the storage tank if the suction is released.
    • Each suction line has only one check valve which is located directly below the suction pump.
    • System must operate at less than atmospheric pressure.
Suction Piping installed or replaced after April 11, 2016
  1. Secondary containment with interstitial monitoring; or
  2. No Requirements IF the following characteristics are readily determinable:
    • Below-grade piping is sloped so that its contents will drain back into the storage tank if the suction is released.
    • Each suction line has only one check valve which is located directly below the suction pump.
    • System must operate at less than atmospheric pressure.

*Monthly Monitoring Choices in the table above include:

Special note for tanks 2,000 gallons or less in capacity: Tanks 2,000 gallons and smaller may be able to use manual tank gauging to meet release detection requirements (be sure you read the information carefully to make sure you meet all the requirements of this method).

What release detection methods can you use to detect leaks from tanks?

Owners and operators of petroleum USTs installed on or before April 11, 2016 must use at least one of the release detection methods below, or other methods approved by their implementing agency.

For USTs installed or replaced after April 11, 2016 owners and operators must use secondary containment with interstitial monitoring.

  1. Secondary containment with interstitial monitoring
    This involves placing a barrier between the UST and the environment. The barrier provides secondary containment and can be a vault, liner, or the outer wall of a double-walled structure. Interstitial monitoring methods range from a simple dip stick to automated vapor or liquid sensors permanently installed in the system. All USTs holding hazardous substances must use this method. More detailed information on secondary containment with interstitial monitoring.
  2. Automatic tank gauging (ATG) systems
    ATG systems use monitors permanently installed in the tank. These monitors are linked electronically to a nearby control device to provide information on product level and temperature. The gauging system can automatically calculate the changes in product volume that can indicate a leaking tank. 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. This method does not work on piping. More detailed information on automatic tank gauging systems.
  3. Continuous in-tank leak detection (CITLD)
    CITLD encompasses all statistically based methods where the system incrementally gathers measurements on an uninterrupted or nearly uninterrupted basis to determine a tank’s leak status. There are two major groups that fit into this category: continuous statistical release detection (also referred to as continuous automatic tank gauging methods) and continual reconciliation. Both groups typically use sensors permanently installed in the tank to obtain inventory measurements. They are combined with a microprocessor in the ATG system or other control console that processes the data. Continual reconciliation methods are further distinguished by their connection to dispensing meters that allow for automatic recording and use of dispensing data in analyzing tanks’ leak status. More detailed information on continuous in-tank leak detection.
  4. Statistical inventory reconciliation (SIR)
    SIR uses sophisticated computer software to determine whether a tank system is leaking. The computer conducts a statistical analysis of inventory, delivery, and dispensing data collected over a period of time and provided by the operator to a vendor. SIR methods process data on a periodic basis involving a separate analysis that is performed either by a SIR vendor or SIR software. CITLD in comparison, processes data on an uninterrupted or nearly uninterrupted basis. More detailed information on statistical inventory control.
  5. Groundwater monitoring
    Groundwater monitoring devices sense the presence of liquid product floating on the groundwater. This method requires installation of monitoring wells at strategic locations in the ground near the tank and along the piping runs. To discover if leaked product has reached groundwater, these wells can be checked periodically by hand or continuously with permanently installed equipment. This method is effective only at sites where groundwater is within 20 feet of the surface. More detailed information on groundwater monitoring.
  6. Vapor monitoring
    Vapor monitors sense and measure either: product vapor in the soil around the tank and piping (sometimes called passive monitoring) or a tracer compound (sometimes called active monitoring) to determine the presence of a leak. This method requires installation of carefully placed monitoring wells. Vapor monitoring can be performed periodically using manual devices or continuously using permanently installed equipment. More detailed information on vapor monitoring.
  7. Manual tank gauging
    Manual tank gauging can be used only on tanks 2,000 gallons or smaller. This method does NOT work on tanks larger than 2,000 gallons or on piping. This method requires taking the tank out of service for at least 36 hours each week to take measurements of the tank's contents. Tanks 1,000 gallons or less can use this method alone. Tanks from 1,001 to 2,000 gallons can use this method only when it is combined with periodic tank tightness testing and only for 10 years after installing a new UST or upgrading an UST with corrosion protection. After 10 years, these USTs must use one of the release detection methods listed above in 1-6. More detailed information on manual tank gauging.

    The additional method below can be used temporarily at petroleum UST sites:

  8. Tank tightness testing and inventory control
    This is a combination of two methods. Tank tightness testing requires periodic tests conducted by vendors who temporarily install special equipment that tests the soundness of the tank. Inventory control requires taking daily accurate measurements of the tank's contents and performing monthly calculations to prove that the system is not leaking. Tank tightness testing and inventory control can be used only for 10 years after installing a new UST or upgrading an UST with corrosion protection. After 10 years, these USTs must use one of the leak detection methods listed above in 1-6. Inventory control must be used in combination with tank tightness testing. More detailed information on tank tightness testing combined with monthly inventory control.

What release detection methods can you use to detect releases from piping?

Pressurized piping installed on or before April 11, 2016 must meet the following requirements:

If your UST has suction piping that is installed on or before April 11, 2016 your release detection requirements will depend on which type of suction piping you have.

Piping installed or replaced after April 11, 2016 must have secondary containment with interstitial monitoring, except suction piping that has characteristics listed above. In addition, pressurized piping must have a device that automatically shuts off or restricts flow or triggers an alarm that indicates a leak.

Why might you fail to be in compliance even if you have the required release detection equipment or method?

It takes more than equipment to be in compliance and to have a safe facility. You must operate and maintain this equipment properly over time or you will not benefit from having the equipment or using an approved release detection method. Most importantly, you must be sure you successfully use the method at least once every 30 days to determine if the UST system has released any of its contents.

Failure to operate and maintain equipment and methods can lead to new releases. For example, a poorly functioning ATG system will provide inaccurate data that will be useless in detecting leaks. A manual vapor or groundwater monitoring device that doesn't work properly means you have no reliable release detection system. Inaccurate data from poorly operated and maintained measuring devices can make SIR methods unable to usefully detect leaks in a timely manner. If your release detection fails, you may incur fines or penalties for noncompliance, as well as an expensive cleanup at your UST site.

What additional operation and maintenance activities will you need to do for your release detection?

For tank release detection:

Beginning on October 13, 2018 as part of the walkthrough inspection requirement, at least every 30-days, you must:

Annually, you must:

Beginning on October 13, 2018 you must annually test operability of mechanical and electronic release detection equipment such as your automatic tank gauge, probes and sensors, and make sure it is working properly. Information on the minimum equipment that must be tested is provided in the more detailed information links associated with the individual release detection methods above.

For piping release detection:

Beginning on October 13, 2018 as part of the walkthrough inspection requirement and at least every 30 days, you must:

Annually, you must:

Beginning on October 13, 2018 you must annually test operability and determine devices you are using to automatically shut off or restrict flow or triggers an alarm to indicate a leak in your piping meet the 3 gallons per hour at 10 pounds per square inch line pressure within one hour performance standard by simulating a leak. Operability of mechanical and electronic components such as suction pumps of suction systems must also be tested annually to ensure they are operating as required.

Are reporting and recordkeeping necessary?

If operation of the release detection method indicates a possible release, UST owners and operators need to report the potential release to the regulatory authority. UST owners and operators must keep records on release detection performance and upkeep. These include the previous year's monitoring results, the most recent tightness test results, performance claims by the release detection device's manufacturer, and records of recent maintenance and repair.

What additional records will you need to keep?

Beginning on October 13, 2018, you must also keep these records:

Click here for more information on compatibility requirements.

What will you have to do to meet the release detection requirements for previously deferred UST systems?

The 2015 UST regulation removes the deferral for UST systems that store fuel solely for use by emergency power generators (emergency generator tanks); field-constructed tanks (FCTs); and airport hydrant fueling systems (AHSs). Owners and operators of these systems must meet release detection requirements described below within the time-frames stated for each type of UST system.

Emergency generator tanks

These UST systems must meet release detection requirements as follows:

Field constructed tanks (FCTs) and airport hydrant systems (AHSs)

A general outline of the release detection requirements for FCTs and AHSs is provided below. Owners and operators must meet release detection requirements identified below.

FCTs and AHSs installed on or before October 13, 2015, must have release detection by October 13, 2018. FCTs and AHSs installed after October 13, 2015 must meet all release detection requirements at installation. Tanks and some piping installed after April 11, 2016 must be secondarily contained and use interstitial monitoring. Owners and operators may use single walled piping when installing or replacing piping associated with UST systems with field-constructed tanks greater than 50,000 gallons and piping associated with airport hydrant systems.

What are the piping release detection requirements?

Underground piping associated with FCTs less than or equal to 50,000 gallons must use the conventional piping release detection options described above. Remember, piping associated with these size FCTs installed after April 11, 2016 must be secondarily contained and use interstitial monitoring.

Underground piping associated with all AHSs and those FCTs greater than 50,000 gallons must meet release detection requirements by using either the conventional piping release detection options described above (except underground piping using conventional groundwater and passive vapor monitoring must combine that method with inventory control as described below); or one of these four alternatives:

What are the tank release detection requirements?

Underground storage tanks associated with AHSs and FCTs with a capacity less than or equal to 50,000 gallons must be monitored using any of the conventional tank release detection options described above. Remember, tanks less than or equal to 50,000 gallons installed after April 11, 2016 must be secondarily contained and use interstitial monitoring.

FCTs with a capacity greater than 50,000 gallons must be monitored either using any of the conventional tank release detection methods above or use one of the alternatives listed below. An exception is that underground storage tanks using conventional groundwater and passive vapor monitoring must combine that method with inventory control as described below:

How can publications on release detection help you?

To assist owners and operators in conducting proper release detection, EPA developed several publications that are available on our website for viewing, downloading, printing, or ordering. These publications present release detection requirements to UST owners and operators:

You may also want to use the following resources:

Many other publications are also available for viewing, downloading, printing, or ordering at EPA's underground storage tanks program's publications page.

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