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Underground Storage Tanks (USTs)

Release Detection for Underground Storage Tanks (USTs)

Introduction

Because detecting UST systems releases quickly helps stop contamination before it spreads from UST sites, EPA requires owners and operators detect releases from their UST systems. EPA allows three categories of release detection: interstitial, internal, and external. These three categories include seven release detection methods.

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Why is release detection crucial?

All regulated tanks and piping must have release detection so that leaks 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 leak from any portion of the tank or its piping that routinely contains petroleum; and
  2. Your leak detection is installed and calibrated in accordance with the manufacturer's instructions.

The leak detection requirements are summarized in the table below:

Notes: Release detection requirements for previously deferred UST systems are discussed here.  Monthly 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:

  • Interstitial method – secondary containment with interstitial monitoring; secondary containment and under-dispenser containment
  • Internal methods – automatic tank gauging (ATG) systems; statistical inventory reconciliation (SIR); continuous in-tank leak detection
  • External method – monitoring for vapors in the soil; monitoring for liquids on the groundwater
  • Other methods approved by the implementing agency

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 leak detection requirements (be sure you meet all the requirements of this method).

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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 these leak detection methods, or other methods approved by their implementing agency.

Interstitial Method

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

Internal Methods

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

External Methods

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What release detection methods can you use to detect leaks 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.

  • If you can show that your suction piping has characteristics listed below, your piping will not need release detection.
    • Below-grade piping operating at less than atmospheric pressure is sloped so that the piping's contents will drain back into the storage tank if the suction is released.
    • Only one check valve is included in each suction line and is located directly below the suction pump.
  • Suction piping that does not exactly match the characteristics noted above must have release detection, either monthly monitoring (using one of the monthly methods noted above for use on pressurized piping) or tightness testing of the piping every 3 years.

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.

What are the regulatory requirements for suction piping?

  • No leak detection is required if the suction piping has the following characteristics:
    1. the piping has enough slope so that the product in the pipe can drain back into the tank when suction is released, and
    2. the piping has only one check valve, which is as close as possible beneath the pump in the dispensing unit.
    3. if a suction line is to be considered exempt based on these design elements, there must be some way to check that the line was actually installed according to these plans, that is those elements of #1 and #2 must be easily discernable.
  • If a suction line does not meet all of the design criteria noted above, one of the following leak detection methods must be used:
    • A line tightness test at least every 3 years; or
    • Monthly interstitial monitoring; or
    • Monthly vapor monitoring; or
    • Monthly groundwater monitoring; or
    • Monthly statistical inventory reconciliation.

The line tightness test must be able to detect a leak at least as small as 0.1 gallon per hour with certain probabilities of detection and of false alarm.

Interstitial monitoring, vapor monitoring, groundwater monitoring, and statistical inventory reconciliation have the same regulatory requirements for piping as they do for tanks. See the Leak Detection Requirements Table for more information.

What are the regulatory requirements for pressurized piping?
Each pressurized piping run must have one leak detection method from each set (A and B) below:

A. An Automatic Line Leak Detector:

  • Automatic flow restricter; or
  • Automatic flow shutoff; or
  • Continuous alarm system.

B. And One Other Method:

  • Monthly interstitial monitoring; or
  • Monthly vapor monitoring; or
  • Monthly groundwater monitoring; or
  • Monthly statistical inventory reconciliation; or
  • Annual tightness test.
  • The automatic line leak detector (LLD) must be designed to detect a leak at least as small as 3 gallons per hour at a line pressure of 10 pounds per square inch within 1 hour by shutting off the product flow, restricting the product flow, or triggering an audible or visual alarm.
  • The line tightness test must be able to detect a leak at least as small as 0.1 gallon per hour when the line pressure is 1.5 times its normal operating pressure. The test must be conducted each year. If the test is performed at pressures lower than 1.5 times operating pressure, the leak rate to be detected must be correspondingly lower.
  • Automatic LLDs and line tightness tests must also be able to meet the federal regulatory requirements regarding probabilities of detection and false alarm.
  • Interstitial monitoring, vapor monitoring, groundwater monitoring, and statistical inventory reconciliation have the same regulatory requirements for piping as they do for tanks. See the Leak Detection Requirements Table for more information.

How do the release detection methods for pressurized piping work?

Automatic line leak detectors (LLDs)
  • Flow restrictors and flow shutoffs can monitor the pressure within the line in a variety of ways: whether the pressure decreases over time; how long it takes for a line to reach operating pressure; and combinations of increases and decreases in pressure.
  • If a suspected leak is detected, a flow restricter keeps the product flow through the line well below the usual flow rate. If a suspected leak is detected, a flow shutoff completely cuts off product flow in the line or shuts down the pump.
  • A continuous alarm system constantly monitors line conditions and immediately triggers an audible or visual alarm if a leak is suspected. Automated interstitial line monitoring system can be set to operate continuously and sound an alarm, flash a signal on the console, or even ring a telephone in a manager's office when a leak is suspected.
  • Both automatic flow restrictors and shutoffs are permanently installed directly into the pipe or the pump housing.
  • An automated interstitial monitoring system can be combined with an automatic shutoff system so that whenever the system detects a suspected release, the product flow in the piping is completely shut down.  Under other methods in 40 CFR § 280.43(i)(2), EPA recognizes such a setup would meet the monthly monitoring requirement as well as the automatic line leak detector requirement.  The following conditions must be met:
    • Sump sensors used for piping interstitial monitoring must remain as close as practicable to the bottom of interstitial spaces being monitored.
    • Monthly monitoring records must be maintained for at leaset one year.
    • Electronic and mechanical components of the system, including shutoff devices, sensors, pressure or vacuum monitors, ust be tested annually for proper operation  Records of the test mush be maintained for three years.
    • Containment sumps that are part of the piping interstitial monitoring system must be tested at least once every three years for liquid tightness.

Line tightness testing

  • Tracer methods do not measure pressure or flow rates of the product. Instead they use a tracer chemical to determine if there is a hole in the line. With tracer methods, all of the factors below may not apply.
  • The line is taken out of service and pressurized, usually above the normal operating pressure. A drop in pressure over time, usually an hour or more, suggests a possible leak.
  • Suction lines are not pressurized very much during a tightness test (about 7 to 15 pounds per square inch).
  • Most line tightness tests are performed by a testing company. You just observe the test.
  • Some tank tightness test methods can be performed to include a tightness test of the connected piping.
  • For most line tightness tests, no permanent equipment is installed.
  • In the event of trapped vapor pockets, it may not be possible to conduct a valid line tightness test. There is no way to tell definitely before the test begins if this will be a problem, but long complicated piping runs with many risers and dead ends are more likely to have vapor pockets.
  • Some permanently installed electronic systems (such as some Automatic Tank Gauging Systems) can meet the requirements of a line tightness test.

Secondary containment with interstitial monitoring

  • A barrier is placed between the piping and the environment. Double walled piping or a leakproof liner in the piping trench can be used.
  • A monitor is placed between the piping and the barrier to sense a leak if it occurs. Monitors range from a simple stick that can be put in a sump to see if a liquid is present, to continuous automated systems, such as those that monitor for the presence of liquid product or vapors.
  • Proper installation of secondary containment is the most important and the most difficult aspect of this leak detection method. Trained and experienced installers are necessary.
  • See the information on secondary containment for additional information. Secondary containment for piping is similar to that for tanks.

Vapor or ground water monitoring

  • Vapor monitoring detects product that leaks into the soil and evaporates.
  • Groundwater monitoring checks for leaked product floating on the groundwater near the piping.
  • A site assessment must be used to determine monitoring well placement and spacing.
  • UST systems using vapor or groundwater monitoring for the tanks are well suited to use the same monitoring method for the piping.
  • See the information on vapor monitoring and groundwater monitoring for more information. Use of these methods with piping is similar to that for tanks.

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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 acceptable leak detection method. Most importantly, you must be sure you successfully use the method at least once a month 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 leak 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 leak detection fails, you may incur fines or penalties for noncompliance, as well as an expensive cleanup at your UST site.

Please review and use the information on our Resources for Owners and Operators Web pages.

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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:

  • Check to make sure the release detection equipment is operating with no alarms or other unusual operating conditions present; and
  • Ensure records of release detection testing (includeds monthly monitoring) are reviewed and current.

Annually, you must:

  • Check hand held release detection equipment such as tank gauge sticks and ground water bailers for operability and serviceability.

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:

  • Check to make sure the devices you are using that automatically shut off or restrict flow of product or triggers an alarm to indicate a leak are operating with no alarms or other unusual operating conditions present; and
  • Ensure records of testing these devices are reviewed and current.

Annually, you must:

  • Visually check containment sumps with interstitial monitoring for damage, leaks to the containment area, or releases to the environment;
  • Check double walled sumps with interstitial monitoring for a leak in the interstitial area.

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.

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Are reporting and recordkeeping necessary?

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

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What additional records will you need to keep?

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

  • Operation and maintenance walkthrough inspections that are required for periods of at least every 30 days and annually for one year;
  • Release detection equipment that is tested annually to ensure proper operation for three years; and
  • If you store regulated substances containing greater than 10 percent ethanol or greater than 20 percent biodiesel, or any other regulated substance identified by the implementing agency, you must keep records demonstrating compatibility of the release detection components in contact with the regulated substances, for as long as the UST system stores the regulated substance.

Click here for more information on compatibility requirements.

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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:

  • Systems installed on or before October 13, 2015 have three years to use any of the applicable release detection methods listed above.
  • Systems installed between October 13, 2015 and April 11, 2016 must use any of the applicable release detection methods listed above at installation.
  • Systems installed or replaced after April 11, 2016 must meet secondary containment requirements with interstitial monitoring.

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.

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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:

  • Line tightness testing (at varying leak rates based on line segment volume)
    • Perform a semiannual or annual line tightness test at or above operating pressure according to a maximum leak detection rate per test section volume.
    • Leak detection rates range from 0.5 to 1.5 gallons per hour (gph) for annual line tightness test; and 1.0 to 3.0 gph for semiannual line tightness test.

Piping segment volumes greater than or equal to 100,000 gallons not capable of initially meeting the 3 gallons per hour leak rate for semiannual testing may be tested at a leak rate up to 6 gallons per hour leak rate for a limited time. The first test, at a leak rate up to 6.0 gph, must be conducted not later than October 13, 2018. The second test, also at a leak rate up to 6.0 gph, must be conducted between October 13, 2018 and October 13, 2021. The third test, at a leak rate up to 3.0 gph, must be conducted between October 13, 2021 and October 13, 2022. Subsequent tests after October 13, 2022 would be performed semiannually or annually at the appropriate leak rates according to line segment volumes.

  • Active vapor monitoring (using chemical tracers)
  • Inventory control with biennial tightness testing, or groundwater or passive vapor monitoring (monitoring stored regulated substance)
  • Another method approved by the implementing agency

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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:

  • Tank tightness testing
  • ATG systems with tank tightness testing (two options)
  • Active vapor monitoring (using chemical tracers)
  • Inventory control with biennial tightness testing, or groundwater or passive vapor monitoring (monitoring stored regulated substance)
  • Another method approved by the implementing agency

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How can publications on release detection help you?

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

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Secondary Containment with Interstitial Monitoring

EPA allows owners and operators to use this interstitial method – secondary containment with interstitial monitoring – for detecting releases from their UST systems. 

This method detects leaks in the space between the UST and a second barrier. The federal UST regulations describe general performance requirements for interstitial monitoring with double walled USTs, USTs fitted with internal liners, and USTs using interception barriers.

On this page:

Secondary Containment

  • Secondary containment provides a barrier between the tank and the environment. The barrier holds the leak between the tank and the barrier so that the leak is detected. The barrier is shaped so that a leak will be directed towards the interstitial monitor.
  • Barriers include:
    • Double walled or jacketed tanks, in which an outer wall partially or completely surrounds the primary tank;
    • Internally fitted liners (bladders); and
    • Leakproof excavation liners that partially or completely surround the tank.
  • Clay and other earthen materials cannot be used as barriers.

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Interstitial Monitors

  • Monitors are used to check the area between the tank and the barrier for leaks and alert the operator if a leak is suspected.
  • Some monitors indicate the physical presence of the leaked product, either liquid or gaseous. Other monitors check for a change in condition that indicates a hole in the tank, such as a loss of vacuum or a change in the level of a monitoring liquid between the walls of a double walled tank.
  • Monitors can be as simple as a dipstick used at the lowest point of the containment to see if liquid product has leaked and pooled there. Monitors can also be sophisticated automated systems that continuously check for leaks.

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What are the regulatory requirements?

  • The barrier must be immediately around or beneath the tank.
  • The interstitial monitor must be checked at least once every 30 days.
  • A double walled system must be able to detect a release through the inner wall.
  • An excavation liner must:
    • Direct a leak towards the monitor;
    • Not allow the specific product being stored to pass through it any faster than 0.000001 cm/sec;
    • Be compatible with the product stored in the tank;
    • Not interfere with the UST's cathodic protection;
    • Not be disabled by moisture;
    • Always be above the groundwater and the 25-year flood plain; and
    • Have clearly marked and secured monitoring wells, if they are used.
  • Beginning on October 13, 2018 you must either test your containment sumps used for interstitial monitoring at least once every three years to ensure the equipment is liquid tight by using vacuum, pressure, or liquid testing or use a double-walled containment sump where the space between the sump is periodically monitored.

    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.
  • 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:

For hand held non-electronic equipment:

  • Keep records of these checks for one year
  • Check for operability and serviceability (includes dipsticks)

For other equipment:

  • Verify the system configuration of the controller
  • Test alarm operability and battery backup
  • Inspect sensors for residual build-up
  • Ensure sensor communication with controller
  • Keep records of these tests for three years

These activities 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.

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Will it work at your site?

In areas with high groundwater or a lot of rainfall, it may be necessary to select a secondary containment system that completely surrounds the tank to prevent moisture from interfering with the monitor.

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Anything else you should consider?

This method works effectively only if the barrier and the interstitial monitor are installed correctly. Therefore, trained and experienced installers are necessary.

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Will you be in compliance?

USTs installed or replaced after April 11, 2016 must be secondarily contained and use interstitial monitoring.

When installed and operated according to the manufacturer's specifications, secondary containment with interstitial monitoring meets the federal leak detection requirements for new and existing USTs. Operation of the monitoring device at least once each month fulfills the requirements for the life of the tank. Secondary containment with interstitial monitoring can also be used to detect leaks from piping.

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Internal Methods

EPA allows owners and operators to use these internal methods – automatic tank gauging, manual tank gauging, statistical inventory reconciliation, and tank tightness testing with inventory control – for detecting releases from their UST systems. 

On this page:

Automatic Tank Gauging

How does the leak detection method work?

Overfill alarmAutomatic tank gauging system

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:

  • The product level and temperature in a tank are measured and recorded by a computer, this saves labor and time.
  • In the inventory mode, the ATG system replaces the use of the gauge stick to measure product level and perform inventory control. This mode records the activities of an in-service tank, including deliveries.
  • In the leak detection mode (in-tank static test), the tank is taken out of service and the product level and temperature are measured for at least one hour.
  • Note: Some systems, known as continuous ATG systems, do not require the tank to be taken out of service to perform a test. This is because these systems can gather and analyze data during many short periods when no product is being added to or taken from the tank. These systems are discussed under Continuous In-Tank Leak Detection.

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:

  • Verify the system configuration
  • Test alarm operability and battery backup
  • Inspect probes and sensors for residual build-up
  • Ensure floats move freely, the shaft is not damaged, and cables are free of kinks and breaks
  • Keep records of these tests for three years

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?

  • Detecting water in the tank is important. Water around a tank may mask a hole in the tank or distort the data to be analyzed by temporarily preventing a release. To detect a release in this situation, check for water at least once a month. Depending upon the product in the tank, detecting water may be difficult to do, but not impossible. Products such as ethanol-based fuels may not form a water bottom. An unexplained presence of water in the tank is considered an unusual operating condition. If you find water in your tank you must investigate and correct the source of the water. Suspected releases must be reported to the implementing agency within 24 hours, or period specified by the implementing agency.
  • The ATG system probe is permanently installed through an opening (not the fill pipe) on the top of the tank. Each tank at a site must be equipped with a separate probe. The ATG system probe is connected to a monitor that displays ongoing product level information and the results of the monthly test. Printers can be connected to the monitor to record this information.
  • ATG systems are often equipped with alarms for high and low product level, high water level, and theft.
  • ATG systems can be linked with computers at other locations from which the system can be programmed or read.
  • For ATG systems that are not of the continuous type, no product should be delivered to the tank or withdrawn from it for at least 6 hours before the monthly test or during the test (which generally takes 1 to 6 hours).
  • An ATG system can be programmed to perform a test more often than once per month (a recommended practice).

Will you be in compliance?

For USTs installed on or before 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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Manual Tank Gauging

How does the leak detection method work?

This method involves keeping the tank undisturbed for at least 36 hours each week, during which the tank's contents are measured, twice at the beginning and twice at the end of the test period. Manual tank gauging can be used as the sole method of leak detection for the life of the tank only for tanks up to 1,000 gallons. Tanks between 1,001 and 2,000 gallons can use this method only in combination with tank tightness testing. This combined method, however, can be used only during the first 10 years following tank installation.

The features of manual tank gauging are:

  • Four measurements of the tank's contents must be taken weekly, two at the beginning and two at the end of at least a 36-hour period during which nothing is added to or removed from the tank (see Table of Test Standards for Manual Tank Gauging).
  • The average of the two consecutive ending measurements are subtracted from the average of the two beginning measurements to indicate the change in product volume.
  • Every week, the calculated change in tank volume is compared to the standards shown in the Table of Test Standards for Manual Tank Gauging at the end of this page. If the calculated change exceeds the weekly standard, the UST may be leaking. Also, monthly averages of the four weekly test results must be compared to the monthly standard in the same way.

What are the regulatory requirements?

  • Liquid level measurements must be taken with a gauge stick that is marked to measure the liquid to the nearest one-eighth of an inch.
  • Manual tank gauging may be used as the sole method of leak detection for tanks with a capacity of 1,000 gallons or less for the life of the tank. Tanks between 551 and 1,000 gallons have two testing standards based on their diameter (see table). These tanks may use a combination of manual tank gauging and periodic tank tightness for the life of the tank (see table for testing standards).
  • For tanks with a capacity of 1,001-2,000 gallons, manual tank gauging must be combined with periodic tightness testing. New tanks must be tightness tested every 5 years for 10 years following installation. Upgraded existing tanks must be tightness tested every 5 years for 10 years following upgrade. (Upgraded tanks have spill, overfill, and corrosion protection.) Existing tanks that have not been upgraded must be tightness tested every year until 1998. See Tank Tightness Testing for details on this method.
  • Unless the tank is 1,000 gallons or less, this combined method will meet the federal requirements only temporarily (as explained above). You must eventually have another monitoring method that can be performed at least once a month.
  • Tanks greater than 2,000 gallons in capacity may not use this method of leak detection to meet these regulatory requirements.
  • 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:

For hand held non-electronic equipment (such as tank gauge sticks):

  • Check for operability and serviceability
  • Keep records of these checks for one year
  • 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?

Manual tank gauging is inexpensive and can be an effective leak detection method when used as described above with tanks of the appropriate size.

Anything else you should consider?

You can perform manual tank gauging yourself. Correct gauging, recording, and interpretation are the most important factors for successful tank gauging. The accuracy of tank gauging can be greatly increased by spreading product-finding paste on the gauge stick before taking measurements.

Will you be in compliance?

Note: Manual tank gauging can only be used for smaller tanks. Tanks 1,000 gallons or less can use this method alone, but tanks from 1,001-2,000 gallons can only use manual tank gauging when it is combined with tank tightness testing. Manual tank gauging cannot be used for tanks over 2,000 gallons. When performed according to recommended practices, manual tank gauging meets the federal leak detection requirements for USTs with a capacity of 1,000 gallons or less for the life of the tank.

USTs installed or replaced after April 11, 2016 may no longer use manual tank gauging as the primary method of release detection. USTs must be secondarily contained and use interstitial monitoring.

More Information On Manual Tank Gauging

EPA's Publication, Manual Tank Gauging: For Small Underground Storage Tanks, clearly explains how to do manual tank gauging with simple step-by-step directions. The booklet also includes standard forms used to record inventory data.

Table of Test Standards for Manual Tank Gauging

Tank Size Minimum
Duration of Test
Weekly Standard
(1 test)
Monthly Standard
(4-test average)
up to 550 gallons 36 hours 10 gallons 5 gallons
551-1,000 gallons (when
tank diameter is 64")
44 hours 9 gallons 4 gallons
551-1,000 gallons (when
tank diameter is 48")
58 hours 12 gallons 6 gallons
551-1,000 gallons
(also requires periodic
tank tightness testing)
36 hours 13 gallons 7 gallons
1,001-2,000 gallons
(also requires periodic
tank tightness testing)
36 hours 26 gallons 13 gallons

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Statistical Inventory Reconciliation (SIR)

How does the leak detection method work?

For statistical inventory reconciliation (SIR), a trained professional uses sophisticated computer software to conduct a statistical analysis of inventory, delivery, and dispensing data, which you must both collect and supply to the vendor on a regular basis.

SIR methods are distinguished from continuous in-tank leak detection methods by how inventory, delivery, and dispensing data are processed and provide a determination of the release status of the tank (or piping). SIR data are processed on a periodic basis involving a separate analysis that is performed either by a SIR vendor or SIR software. Continuous statistically based in-tank release detection methods process data on an on-going basis occurring in an uninterrupted or nearly uninterrupted manner.

The features of SIR are:

  • SIR analyzes inventory, delivery, and dispensing data collected over a period of time to determine whether or not a tank system is leaking.
  • Each operating day, the product level is measured using a gauge stick or other tank level monitor. You also keep complete records of all withdrawals from the UST and all deliveries to the UST. After data have been collected for the period of time required by the SIR vendor, you provide the data to the SIR vendor.
  • The SIR vendor uses sophisticated computer software to conduct a statistical analysis of the data to determine whether or not your UST may be leaking. The SIR vendor provides you with a test report of the analysis.

What are the regulatory requirements?

  • To be allowable as monthly monitoring, a SIR method must be able to detect a leak at least as small as 0.2 gallons per hour or a release of 150 gallons within a month and meet the federal UST requirements regarding probabilities of detection and of false alarm. SIR methods must use a threshold that does not exceed one-half the minimum detectible leak rate. Data must be submitted at least monthly.
  • To be allowable as an equivalent to tank tightness testing, a SIR method must be able to detect a leak at least as small as  0.1 gallons per hour and meet the federal regulatory requirements regarding probabilities of detection and of false alarm.
  • The individual SIR method must have been evaluated with a test procedure to verify  that it can detect leaks at the required level and with the appropriate probabilities of detection and of false alarm.
  • If the test report is not conclusive, you must take the steps necessary to find out conclusively whether your tank is leaking. Because SIR requires multiple days of data, you will probably have to use another method.
  • You must keep on file both the test reports and the documentation that the SIR method used is valid for your UST system.
  • 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:

For hand held non-electronic equipment:

  • Check for operability and serviceability (includes dipsticks)
  • Keep records of these checks for one year

For other equipment:

  • Verify the system configuration of the controller
  • Test alarm operability and battery backup
  • Inspect sensors for residual build-up
  • Ensure sensor communication with controller
  • Keep records of these tests for three years
  • 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?

  • Generally, few product or site restrictions apply to the use of SIR.
  • SIR has been used primarily on tanks no more than 18,000 gallons in capacity. If you are considering using a SIR method for larger tanks, discuss its applicability with the vendor.

Anything else you should consider?

  • Detecting water in the tank is important. Water around a tank may mask a hole in the tank or distort the data to be analyzed by temporarily preventing a release. To detect a release in this situation, check for water at least once a month. Depending upon the product in the tank, detecting water may be difficult to do, but not impossible. Products such as ethanol-based fuels may not form a water bottom. An unexplained presence of water in the tank is considered an unusual operating condition. If you find water in your tank you must investigate and correct the source of the water. Suspected releases must be reported to the implementing agency within 24 hours, or period specified by the implementing agency.
  • Data, including product level measurements, dispensing data, and delivery data, should all be carefully collected according to the SIR vendor's specifications. Poor data collection produces inconclusive results and noncompliance.
  • The SIR vendor will generally provide forms for recording data, a calibrated chart converting liquid level to volume, and detailed instructions on conducting measurements.
  • SIR should not be confused with other release detection methods that also rely on periodic reconciliation of inventory, withdrawal, and delivery data. Unlike manual tank gauging or inventory control, SIR uses a sophisticated statistical analysis of data to detect releases. This analysis can only be done by competent, trained practitioners.

Will you be in compliance?

For USTs installed on or before April 11, 2016 owners and operators may use SIR as their primary method of release detection. When installed and operated according to the manufacturer's specifications, SIR meets the federal release detection requirements as follows:

  • SIR with a 0.2 gallon per hour leak detection capability meets the federal requirements for monthly monitoring for the life of the tank and piping.
  • SIR with a 0.1 gallon per hour leak detection capability meets the federal requirements as an equivalent to tank tightness testing.
  • SIR can, if it has the capability of detecting even smaller leaks, meet the federal requirements for line tightness testing as well.

USTs installed or replaced after April 11, 2016 may no longer use SIR as the primary method of release detection. USTs must be secondarily contained and use interstitial monitoring.

Additional Information on SIR

EPA developed two publications that more fully explain SIR:

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Continuous In-Tank Leak Detection

How does the release detection method work?

Continuous in-tank leak detection (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.

What are the regulatory requirements?

  • CITLD operates on an uninterrupted basis or operates within a process that allows the system to gather incremental measurements to determine the release status of the tank at least once every 30 days.
  • CITLD must be able to detect a leak at least 0.2 gallon per hour with a probability of detection of at least 95 percent and a probability of false alarm of no more than 5 percent. Some CITLD methods can also detect a leak of 0.1 gallon per hour with the probabilities listed above.
  • 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:
    • Verify the system configuration of the controller
    • Test alarm operability and battery backup
    • Inspect probes and sensors for residual build-up
    • Ensure floats move freely, the shaft is not damaged, and cables are free of kinks and breaks
    • Keep records of these tests for three years

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?

Continuous in-tank leak detection methods may allow for monitoring larger tank capacities and higher system throughputs. However, these methods have limitations as well. Check the capabilities of any method you use to ensure your system meets all regulatory performance requirements.

Anything else you should consider?

Detecting water in the tank is important. Water around a tank may mask a hole in the tank or distort the data to be analyzed by temporarily preventing a release. To detect a release in this situation, check for water at least once a month. Depending upon the product in the tank, detecting water may be difficult to do, but not impossible. Products such as ethanol-based fuels may not form a water bottom. An unexplained presence of water in the tank is considered an unusual operating condition. If you find water in your tank you must investigate and correct the source of the water. Suspected releases must be reported to the implementing agency within 24 hours, or period specified by the implementing agency.

Will you be in compliance?

For USTs installed on or before April 11, 2016 owners and operators may use CITLD as their primary method of release detection. When installed and operated according to the manufacturer's specifications, CITLD meets the federal release detection requirements. CITLD can also be used to detect leaks in piping. USTs installed or replaced after April 11, 2016 may no longer use CITLD as the primary method of release detection. USTs must be secondarily contained and use interstitial monitoring.

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Tank Tightness Testing with Inventory Control

When performed according to the manufacturer's specifications, periodic tank tightness testing combined with monthly inventory control can temporarily meet the federal leak detection requirements for tanks (this method does not detect piping leaks). Inventory control alone does not meet the federal requirements for leak detection for tanks.

Tightness testing (if conducted at least every 3 years) is also an option for underground piping.

Tank Tightness Testing

How does tank tightness testing work?

Tightness tests include a wide variety of methods. Other terms used for these methods include precision, volumetric, and nonvolumetric testing.

The features of tank tightness testing are:
  • Many tightness test methods are volumetric methods in which the change in product level in a tank over several hours is measured very precisely (in milliliters or thousandths of an inch).
  • Other methods use acoustics or tracer chemicals to determine the presence of a hole in the tank. With such methods, all of the factors in the following bullets may not apply.
  • For most methods, changes in product temperature also must be measured very precisely (thousandths of a degree) at the same time as level measurements, because temperature changes cause volume changes that interfere with finding a leak.
  • For most methods, a net decrease in product volume (subtracting out volume changes caused by temperature) over the time of the test indicates a leak.
  • The testing equipment is temporarily installed in the tank, usually through the fill pipe.
  • The tank must be taken out of service for the test, generally for several hours, depending on the method.
  • Many test methods require that the product in the tank be a certain level before testing, which often requires adding product from another tank on-site or purchasing additional product.
  • Some tightness test methods require all of the measurements and calculations to be made by hand by the tester. Other tightness test methods are highly automated. After the tester sets up the equipment, a computer controls the measurements and analysis.
  • A few methods measure properties of the product that are independent of temperature, such as the mass of the product, and so do not need to measure product temperature.
  • Some automatic tank gauging systems are capable of meeting the regulatory requirements for tank tightness testing and can be considered as an equivalent method. Check with your implementing agency.

What are the regulatory requirements for tank tightness testing?

  • The tightness test method must be able to detect a leak at least as small as 0.1 gallon per hour with certain probabilities of detection and of false alarm.
  • Tightness tests must be performed periodically. UST systems installed on or before April 11, 2016 must have tank tightness tests every 5 years for 10 years following installation. After the applicable time period noted above, you must have a monitoring method that can be performed at least once every 30 days.
  • Beginning on October 13, 2018, you must test your release detection equipment annually to make sure it is working properly:
    • Tank tightness testing is typically performed by a qualified testing company. Therefore, this requirement may not be applicable. If your implementing agency allows use of ATG systems for tank tightness testing, you must follow the testing procedures required for ATG systems.

Anything else about tank tightness testing that you should consider?

  • For most methods, the test is performed by a testing company. You just observe the test.
  • Tank tightness testing has been used primarily on tanks no more than 15,000 gallons in capacity containing gasoline and diesel. If you are considering using tightness testing for larger tanks or products other than gasoline or diesel, discuss the method's applicability with the manufacturer's representative.
  • Manifolded tanks generally should be disconnected and tested separately.
  • Procedure and personnel, not equipment, are usually the most important factors in a successful tightness test. Therefore, well-trained and experienced testers are very important. Some implementing agencies have tester certification programs.

Inventory Control

How does inventory control work?

Inventory control requires daily measurements of tank contents and mathematical calculations that let you compare your stick inventory (what you've measured) to your book inventory (what your recordkeeping indicates you should have). If the difference between your stick and book inventory is too large, your tank may be leaking.

EPA's booklet, Doing Inventory Control Right, explains how to do inventory control with simple step-by-step directions. The booklet also includes standard forms used to record inventory data.

The features of inventory control are:
  • UST inventories are determined daily by using a gauge stick and the data is recorded on a form. The level on the gauge stick is converted to a volume of product in the tank using a calibration chart, which is often furnished by the UST manufacturer.
  • The amounts of product delivered to and withdrawn from the UST each day are also recorded. At least once every 30 days, the gauge stick data and the sales and delivery data are reconciled and the month's overage or shortage is determined. If the overage or shortage is greater than or equal to 1.0 percent of the tank's flow-through volume plus 130 gallons of product, the UST may be leaking.

What are the regulatory requirements for inventory control?

  • Inventory control must be used in conjunction with periodic tank tightness tests.
  • The gauge stick should be long enough to reach the bottom of the tank and marked so that the product level can be determined to the nearest one-eighth of an inch. A monthly measurement must be taken to identify any water at the bottom of the tank.
  • Product dispensers must be calibrated to the local weights and measures standards.
  • 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:

For hand held non-electronic equipment (such as tank gauge sticks):

  • Check for operability and serviceability
  • Keep records of these checks for one year
  • 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.

Anything else about inventory control that you should consider?

  • Inventory control is a practical, commonly used management tool that does not require closing down the tank operation for long periods.
  • The accuracy of tank gauging can be greatly increased by spreading product-finding paste on the gauge stick before taking measurements (or by using in-tank product level monitoring devices).
  • If your tank is not level, inventory control may need to be modified. You will need to get a corrected tank chart.

Are there time restrictions on the use of this combined method?

USTs installed on or before April 11, 2016 may use this method for 10 years after the date the tank was installed or upgraded with corrosion protection. Note that the end date is based on the compliance status of the tank only, not the entire UST system. As a result, some USTs may not be able to use this combined method for as long as 10 years. At the end of the valid period, you must use one of the monthly monitoring release detection choices described herein.

USTs installed or replaced after April 11, 2016 may no longer use inventory control combined with periodic tank tightness testing as the primary method of release detection. USTs must be secondarily contained and use interstitial monitoring.

External Methods

EPA allows owners and operators to use these external methods – groundwater monitoring and vapor monitoring – for detecting releases from their UST systems. 

On this page:

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Monitoring for Liquids on the Groundwater

How does the leak detection method work?

This method monitors the groundwater table near an UST for the presence of released free product on the water table. Monitoring wells near the UST are checked frequently to see if petroleum can be detected. The federal UST regulation describes several requirements for use of this method. For example, this method cannot be used if the water table is more than 20 feet below the surface of the ground.

Features of groundwater monitoring are:

  • Groundwater monitoring involves the use of permanent monitoring wells placed close to the UST. The wells are checked at least monthly for the presence of product that has leaked from the UST and is floating on the groundwater surface.
  • The two main components of a groundwater monitoring system are the monitoring well (typically a well of 2-4 inches in diameter) and the monitoring device.
  • Detection devices may be permanently installed in the well for automatic, continuous measurements for leaked product.
  • Detection devices are also available in manual form. Manual devices range from a bailer (used to collect a liquid sample for visual inspection) to a device that can be inserted into the well to electronically indicate the presence of leaked product. Manual devices must be operated at least once a month.
  • Before installation, a site assessment is necessary to determine the soil type, groundwater depth and flow direction, and the general geology of the site. This assessment can only be done by a trained professional.
  • The number of wells and their placement is very important. Only an experienced contractor can properly design and construct an effective monitoring well system. A minimum of two wells is recommended for a single tank excavation. Three or more wells are recommended for an excavation with two or more tanks. Some state and local agencies have developed regulations for monitoring well placement.

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What are the regulatory requirements?

  • Groundwater monitoring can only be used if the stored substance does not easily mix with water and floats on top of water.
  • If groundwater monitoring is to be the sole method of leak detection, the groundwater must not be more than 20 feet below the surface, and the soil between the well and the UST must be sand, gravel or other coarse materials.
  • Monitoring wells must be properly designed and sealed to keep then from becoming contaminated from outside sources. The wells must also be clearly marked and secured.
  • Wells should be placed in the UST backfill so that they can detect a leak as quickly as possible.
  • Product detection devices must be able to detect one-eighth inch or less of leaked product on top of the groundwater.
  • Beginning on October 13, 2018 you must keep records of a site assessment for as long as you use this method, showing that the monitoring system is set properly. If you do not have a site assessment, you will need to have one conducted.
  • Site assessments conducted after October 13, 2015 must be signed by a licensed professional.
  • 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:

For hand held non-electronic equipment (such as groundwater bailers):

  • Check for operability and serviceability
  • Keep records of these checks for one year

For other equipment:

  • Verify the system configuration of the controller
  • Test alarm operability and battery backup
  • Inspect well probes and sensors for residual build-up
  • Test manual electronic devices (such as portable probes)
  • Keep records of these tests for three years

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.

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Will it work at your site?

In general, groundwater monitoring works best at UST sites where:
  • Monitoring wells are installed in the tank backfill; and
  • There are no previous releases of product that would falsely indicate a current release.

A professionally conducted site assessment is critical for determining these site-specific conditions.

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Will you be in compliance?

For USTs installed on or before April 11, 2016 owners and operators may use groundwater monitoring as their primary method of release detection. When installed and operated according to the manufacturer's specifications and in accordance with the site assessment, groundwater monitoring meets the federal release detection requirements. Operation of the groundwater monitoring system at least once each month fulfills federal regulatory requirements. Groundwater monitoring can also be used to detect leaks in piping. USTs installed or replaced after April 11, 2016 may no longer use groundwater monitoring as the primary method of release detection. USTs must be secondarily contained and use interstitial monitoring.

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Monitoring for Vapors in the Soil

How does the leak detection method work?

This method samples for either: product vapors in the soil gas surrounding the UST (sometimes called passive monitoring) or presence of a tracer compound introduced into the UST system (sometimes called active monitoring). Leaked petroleum produces vapors that can be detected in the soil gas. The federal UST regulation describes several requirements for using this leak detection method. For example, this method requires using porous soils in the backfill and locating the monitoring devices in these porous soils near the UST system.

Features of vapor monitoring systems are:

  • Passive vapor monitoring senses or measures fumes from leaked product in the soil around the tank to determine if the tank is leaking.
  • Active vapor monitoring senses or measures a tracer compound leaked in the soil around the tank to determine if the tank is leaking.
  • Fully automated vapor monitoring systems have permanently installed equipment to continuously or periodically gather and analyze vapor samples and respond to a release with a visual or audible alarm.
  • Manually operated vapor monitoring systems range from equipment that immediately analyzes a gathered vapor sample to devices that gather a sample that must be sent to a laboratory for analysis. Monitoring results from manual systems are generally less accurate than those from automated systems. Manual systems must be used at least once a month to monitor a site.
  • All vapor monitoring devices should be periodically calibrated according to the manufacturer's instructions to ensure that they are properly responding.
  • Before installation, a site assessment is necessary to determine the soil type, ground water depth and flow direction, and the general geology of the site. This can only be done by a trained professional.
  • The number of wells and their placement is very important. Only an experienced contractor can properly design and construct an effective monitoring well system. Vapor monitoring requires the installation of monitoring wells within the tank backfill. A minimum of two wells is recommended for a single tank excavation. Three or more wells are recommended for an excavation with two or more tanks. Some state and local agencies have developed regulations for monitoring well placement.

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What are the regulatory requirements?

  • The UST backfill must be sand, gravel or another material that will allow the vapors to easily move to the monitor.
  • The backfill should be clean enough that previous contamination does not interfere with the detection of a current leak.
  • The substance stored in the UST must vaporize easily so that the vapor monitor can detect a release.
  • High groundwater, excessive rain, or other sources of moisture must not interfere with the operation of vapor monitoring for more than 30 consecutive days.
  • Monitoring wells must be secured and clearly marked.
  • Beginning on October 13, 2018, you must keep records of a site assessment, for as long as you use this method, showing that the monitoring system is set properly. If you do not have a site assessment, you will need to have one conducted.
  • Site assessments conducted after October 13, 2015 must be signed by a licensed professional.
  • 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:

For hand held non-electronic equipment:

  • Check for operability and serviceability
  • Keep records of these checks for one year

For other equipment:

  • Verify the system configuration of the controller
  • Test alarm operability and battery backup
  • Inspect sensors for residual build-up
  • Test manual electronic devices (such as photoionization detectors)
  • Keep records of these tests for three years

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.

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Will it work at your site?

Before installing a vapor monitoring system, a site assessment must be done to determine whether vapor monitoring is appropriate at the site. A site assessment usually includes at least a determination of the groundwater level, background contamination, stored product type, and soil type. This assessment can only be done by a trained professional.

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Will you be in compliance?

For USTs installed on or before April 11, 2016, owners and operators may use vapor monitoring as their primary method of release detection. When installed and operated according to the manufacturer's specifications and in accordance with the site assessment, vapor monitoring meets the federal release detection requirements. Vapor monitoring can also be used to detect leaks in piping. Operation of the vapor monitoring system at least once each month fulfills federal release detection requirements. USTs installed or replaced after April 11, 2016 may no longer use vapor monitoring as the primary method of release detection. USTs must be secondarily contained and use interstitial monitoring.

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