&EPA
United States
Environmental Protection
Agency
UPDA1I D2016
Release Detection For Underground
Storage Tanks And Piping:
Straight Talk On Tanks
»w Printed on Recycled Paper
EPA 510 K 16 003
May 2016
-------
EPA wrote this booklet for owners and operators of underground storage tanks (USTs).
This booklet describes the 2015 revised federal UST regulation. Many states and territories
(referred to as states in this booklet) have state program approval from EPA. To find a list of states
>rosrams.
If your UST systems are located in a state with state program approval, your requirements may be
different from those identified in this booklet. To find information about your state's UST
regulation, contact your implementing agency or visit its website. You can find links to state UST
websites at
If your UST systems are located in a state without state program approval, both the requirements
in this booklet and the state requirements apply to you.
If your UST systems are located in Indian country, the requirements in this booklet apply to you.
Free Publications About UST Requirements
Download or read Release Detection For Underground Storage Tanks And Piping: Straight Talk On
Tanks on EPA's underground storage tank (UST) website at vv . Order printed
copies of many, but not all, of our documents from the National Service Center for Environmental
Publications (NSCEP), EPA's publication distributor: write to NSCEP, Box 42419, Cincinnati, OH
45242; call NSCEP's toll-free number 800-490-9198; or fax your order to NSCEP 301-604-3408.
Image credits:
New Hampshire Department of Environmental Services (electronic line leak detector on cover and
in page 33 header)
Tanknology (UST testing on cover and in page 19 header)
Highland Tank & Manufacturing Company (steel tanks on cover and in headers)
©iStock.com/bisell - Not For Reuse (fiberglass tanks on cover and in headers)
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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Contents
Do You Have Questions About Release Detection? 1
An Overview Of Release Detection Requirements 2
Secondary Containment With Interstitial Monitoring 7
Automatic Tank Gauging Systems 10
Continuous In-Tank Leak Detection 13
Statistical Inventory Reconciliation 15
Tank Tightness Testing With Inventory Control 19
Manual Tank Gauging 24
Groundwater Monitoring 27
Vapor Monitoring 30
Release Detection For Underground Piping 33
Links For More Information , ,.., ,.., 37
Disclaimer
This document provides information about the 2015 federal
underground storage tank (LIST) system requirements. The
document is not a substitute for U.S. Environmental Protection
Agency regulations nor is it a regulation itself it does not
impose legally binding requirements.
For regulatory requirements regarding LIST systems, refer to the
federal regulation governing LIST systems (40 CFR part 280).
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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Do You Have Questions
About Release Detection?
As an owner or operator of underground storage tanks
(USTs) storing petroleum:
Do you understand the basic release detection
requirements for USTs?
Do you need help choosing the best release detection
method for your USTs?
These are important questions, because your UST and its
underground piping must have release detection in order to
comply with federal law.
This booklet begins with an overview of the federal
regulatory requirements for release detection. Your
implementing agency may have additional regulations, which
apply to your system. Check your implementing agency
requirements to ensure you are in compliance.
Throughout this document, bold type and orange updated
boxes indicate new requirements in the 2015 UST regulation.
Each following section focuses on one release detection
method for tanks or the requirements for piping. You will
find answers in this booklet to many basic questions about
how release detection methods work and which methods are
best for your UST site.
Why Is Release Detection Important?
As of September 2015, over 528,000 UST releases were
confirmed since the UST program was implemented. At sites
without release detection, contamination can spread
undetected, requiring difficult and costly cleanups.
If you have effective release detection, you can respond
quickly to signs of releases. You can minimize the extent of
or eliminate potential for environmental damage and the
threat to human health and safety. Early action also protects
you from high costs that can result from cleaning up
extensive releases and responding to third-party liability
claims.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
An Overview Of Release
Detection Requirements
All federally regulated USTs must have a release detection
method, or combination of methods, that:
Can detect a release from any portion of the tank and
the connected underground piping that routinely
contains product, and
Is installed and calibrated according to the
manufacturer's instructions.
Tanks and piping installed or replaced after April 11,
2016 must be secondarily contained and use interstitial
monitoring, except for suction piping that meets
requirements discussed on page 33.
All UST owners and operators must monitor their tanks and
piping at least once every 30 days. This booklet may use the
terms monthly or month and annually or annual. These terms
mean at least once every 30 days and not to exceed 365 days,
respectively.
For tanks installed on or before April 11, 2016, you can use
any of these release detection methods:
Secondary containment with interstitial monitoring
Automatic tank gauging systems (performing in-tank
static tests)
Continuous in-tank leak detection
Statistical inventory reconciliation
Tank tightness testing with inventory control
Manual tank gauging
Groundwater monitoring
Vapor monitoring
Other methods meeting performance standards or
approved by implementing agency
For underground piping installed on or before April 11, 2016,
you may use any of the release detection methods listed
above that are appropriate for piping or conduct periodic line
tightness testing. See page 33 for piping release detection
requirements.
All pressurized underground piping connected to your USTs
must also have automatic line leak detectors.
For Owners Of Field-
constructed Tanks Or Airport
Hydrant Systems
The 2015 UST regulation
removes the deferral for
field-constructed tanks and
airport hydrant systems,
making them subject to the
UST requirements. These
systems are not covered in
this booklet due to their
uniqueness. For information
on the requirements for
field-constructed tanks and
airport hydrant systems, see
EPA's website at
www.eoa.gov/ust/field-
constructed-tanks-and-
airaort-hvdrant-svstems-
2015-reauirements.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
UPDATED
UPDATED
UPDATED
UST systems that store fuel solely for use by emergency power
generators must meet release detection requirements as
follows:
Systems installed on or before October 13, 2015 must
use any of the applicable release detection methods
listed above no later than October 13, 2018.
Systems installed between October 13, 2015 and April
11, 2016 must use any of the applicable release detection
methods listed above beginning at installation.
Systems installed or replaced after April 11, 2016 must
meet secondary containment requirements with
interstitial monitoring as release detection.
To make sure your release detection equipment is working
properly, you must begin doing the following no later than
October 13,2018:
Test your release detection equipment annually.
Conduct walkthrough inspections every 30 days to
visually check your release detection equipment and
maintain applicable records of those checks.
Conduct annual walkthrough inspections to visually
check containment sumps and hand-held release
detection equipment, such as tank gauge sticks and
groundwater bailers.
EPA revised the definition of release detection in the 2015 UST
regulation. The definition clarifies that regulated substances
entering into the interstitial space are leaks instead of releases.
According to the 2015 UST regulation, a release always reaches
the environment.
The revised definition allows continued use of the term release
detection as it applies to both releases and leaks. More
importantly, the 2015 secondary containment with interstitial
monitoring requirement makes it necessary to clarify how the
terms release and leak are used, because product escaping the
primary containment may not necessarily reach the
environment.
Releases and leaks have different investigation and reporting
requirements. For information on addressing suspected
releases, see EPA's Musts for USTs at www.epa.gov/ust/musts-
usts.
EPA's Operating and
Maintaining Underground
Storage Tank Systems at
>nk-
system al-help-and-
provides
additional information about
operation and maintenance.
Release means
any spilling, leaking,
emitting, discharging,
escaping, leaching or
disposing from an UST into
groundwater, surface water,
or subsurface soils.
Release detection means
determining whether a
release of a regulated
substance has occurred from
the UST system into the
environment or a leak has
occurred into the interstitial
space between the UST
system and its secondary
barrier or secondary
containment around it.
Look For Proof That Performance Requirements Are
Met
The federal UST regulation requires that your release detection
equipment meet specific performance requirements. Performance
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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claims and means by which performance was determined must be
described in writing by either the equipment manufacturer or
installer. At the request of equipment manufacturers, most release
detection equipment and methods available in the United States
have been evaluated by a third party, who is independent of the
manufacturer or vendor of the release detection system. The
evaluation shows that a release detection system can work as
designed. Evaluations follow recommended evaluation procedures
and testing and often take place at a testing facility. EPA and third
parties developed evaluation procedures for all release detection
methods.
Although not mandated by federal UST requirements, many
implementing agencies prefer, and some require, third party
evaluation of release detection equipment and methods. Check
with your implementing agency to determine what is acceptable.
Although an evaluation and its resulting documentation are
technical, you should be familiar with the evaluation's report and
its results form. You may obtain this documentation from the
release detection manufacturer and should keep it on file. Whether
by the manufacturer, installer, or third party evaluation,
performance claims determinations contain a signed certification
that the system performed as described, as well as documentation
of proper monitoring or testing procedures and any limitations of
the system. This information is important to your compliance with
UST requirements. For example, if a tank tightness test was
evaluated and you have documentation only for tests taking two
hours or more, then your UST must be tested for at least two hours
or it would fail to meet the release detection requirements.
The National Work Group on Leak Detection Evaluations
(NWGLDE) - an independent group - maintains a list of release
detection equipment whose third-party-conducted documentation
has been reviewed by the group. The list contains a detailed
summary of specifications for over 390 release detection systems.
Although you can use the list to help select systems and determine
their compliance or acceptability, it does not consist of approved
release detection systems. Approval or acceptance of release
detection systems rests with your implementing agency, which in
most cases is your state environmental agency. See NWGLDE's
list at www.nwglde.org.
Required Probabilities For Certain Release Detection
Methods
The federal UST regulation requires that release detection methods
be able to detect certain leak rates consistently. Methods must
detect the specified leak rate with a probability of detection of at
least 95 percent and a probability of false alarm of no more than 5
percent. This means that, of 100 tests of USTs leaking at the
You may use any technology,
as long as it meets a
performance standard of
detecting a leak of 0.2
gallons per hour with a
probability of detection of at
least 95 percent and a
probability of false alarm of
no more than 5 percent.
Implementing agencies can
approve another method if
you demonstrate that it
works as well as one of the
methods listed in this booklet
and you comply with any
condition the agency
imposes.
Perform release detection
according to documented
procedures.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
specified rate, at least 95 of them must be correctly detected. It
also means that, of 100 tests of non-leaking USTs, no more than 5
can be incorrectly called leaking.
Keep Release Detection Records
For each release detection method you use, you must keep these
written records:
Proof that performance claims are met and the means by
which performance was determined by either the
equipment manufacturer or installer and probabilities of
detection and false alarm are met. Retain these records for
five years or another period determined by your
implementing agency.
Results of any sampling, testing, or monitoring. Retain
these results for one year or another period determined by
the implementing agency. Retain tank tightness test results
until the next test is conducted.
All calibration, maintenance, and repair of release detection
equipment permanently located on-site. Retain records for
one year after servicing work is completed or another
period determined by your implementing agency.
Schedules of required calibration and maintenance
provided by equipment manufacturers. Retain the
schedules for five years from the date of installation.
Other records may be required and are discussed, as
applicable, for individual release detection methods.
Not all release detection
methods must meet required
probabilities. The
requirement applies to all
tank release detection
methods except for
secondary containment with
interstitial monitoring and
groundwater and vapor
monitoring. It also applies to
automatic line leak detectors
and line tightness testing.
UPDATED
Keep Records Demonstrating Compatibility
The 2015 UST regulation includes additional requirements to
help owners and operators demonstrate that each UST system
is compatible with certain regulated substances before storing
them. If you store regulated substances containing greater
than 10 percent ethanol or greater than 20 percent biodiesel, or
any other regulated substance identified by your implementing
agency, you must keep records demonstrating compatibility of
the UST system, including release detection equipment, for as
long as the UST system stores the regulated substance. For
more information on compatibility requirements, see EPA's
UST System Compatibility With Biofuels at
www.epa.gov/ust/ust-system-compatibilitv-biofuels.
Make sure your UST system is
compatible with the
substance it stores.
Responding To Alarms And Other Suspected Releases
Alarms associated with release detection monitoring may indicate
a release has occurred. An alarm incident does not necessarily
have to be reported. In the event of an alarm, you must investigate,
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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determine, and correct the source of the alarm. Suspected releases
must be reported to your implementing agency within 24 hours or
another period specified by your implementing agency. Check
with your implementing agency to determine whether the alarm
incident must also be reported.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
Secondary Containment
With Interstitial
Monitoring
Secondary containment uses a barrier, an outer wall, or a
liner around the UST or piping to provide secondary
containment. Tanks can also be equipped with inner bladders
that provide secondary containment.
Tanks and piping installed or replaced after April 11,
2016 must be secondarily contained and use interstitial
monitoring. This applies to UST systems containing
petroleum or hazardous substances.
Will You Be In Compliance?
When installed and operated according to the manufacturer's
specifications, secondary containment with interstitial
monitoring meets the federal release detection requirements
for USTs. You must test for a release at least once every 30
days. Secondary containment with interstitial monitoring can
also be used to detect leaks from piping. See release
detection for piping requirements on page 33.
How Does The Release Detection Method Work?
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 toward 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, such as bladders; and
Leak proof excavation liners that partially or
completely surround the tank.
Clay and other earthen materials are not considered
acceptable secondary barriers.
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
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
loss of vacuum or pressure, or a change in the level of a monitoring
liquid, such as a brine or glycol solution, 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.
What Are The Regulatory Requirements?
You must check for a release at least once every 30 days.
The barrier must be immediately around or beneath the tank.
A double-walled system must be able to detect a leak through the
inner wall.
An excavation liner must:
Direct a leak toward the monitor;
Prohibit the specific product stored to pass through it no
faster than 10"6 centimeters per second;
Be compatible with the product stored in the tank;
Allow the UST's cathodic protection to work unaffected;
Withstand moisture;
Always be above the groundwater and the 25-year flood
plain; and
Have clearly marked and secured monitoring wells, if they
are used.
No later than October 13, 2018, you must begin performing the
following on your release detection equipment annually to
make sure it is working properly.
For hand held non-electronic equipment (including dipsticks):
Check for operability and serviceability
Keep walkthrough inspection records 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
These activities must be performed according to
manufacturer's requirements; a nationally recognized code of
practice; or requirements determined by your implementing
A bladder must be
compatible with the product
stored and must be equipped
with an automatic
monitoring device.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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agency to be as protective of human health and the
environment.
An unexplained presence of liquid in the interstitial space of
secondarily contained systems is considered an unusual operating
condition. Except if the liquid in the interstitial space is used as
part of the interstitial monitoring method, for example brine, if you
find liquid in the interstitial space of secondarily contained
systems, you must investigate, remove the liquid, and correct the
source of the liquid.
Anything Else You Should Consider?
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.
This method works effectively only if the barrier and the interstitial
monitor are installed correctly. Therefore, trained and experienced
installers are necessary.
You must investigate and
remove any liquid in the
interstitial space of
secondarily contained
systems, unless the liquid is
part of the release detection
method.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
UPDATED
Automatic Tank
Gauging Systems
In an automatic tank gauging (ATG) system, 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. ATG systems operate in one of two
modes: inventory mode and leak detection mode. In the leak
detection mode, ATG systems can be set to perform a leak
test on either a periodic basis or continuous basis. Leak tests
set to run on a periodic basis are referred to as in-tank static
tests and require the system to be taken off-line typically for
between one to six hours. Leak testing set to run on a
continuous basis is referred to as continuous in-tank leak
detection and operates on an uninterrupted or nearly
uninterrupted manner.
Will You Be In Compliance?
When installed and operated according to the manufacturer's
specifications, ATG systems meet the federal release
detection requirements for tanks installed on or before April
11, 2016. A leak test performed at least every 30 days is
required for the tank. This method does not detect piping
leaks. For piping, see release detection requirements for
piping on page 33.
How Does The Release Detection Method Work?
In the inventory mode:
The product level and temperature in a tank are
measured and recorded by a computer.
ATG systems replace 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 for in-tank static testing:
The tank is taken out of service and the product
level and temperature are measured for at least
one hour.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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Note: When referring to ATG systems in this booklet, we
mean a system performing in-tank static testing while
operating in the leak detection mode. See continuous in-
tank leak detection on page 13 for ATG systems
performing continuous in-tank leak detection testing while
operating in the leak detection mode.
In the leak detection mode for continuous in-tank leak
detection:
Some systems, known as continuous ATG systems, do
not require the tank 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.
Other systems combine aspects of automatic tank
gauges with statistical inventory reconciliation.
Note: Both of these methods fall under continuous in-tank
leak detection because they operate on an uninterrupted
basis or pause for milliseconds to gather and record data
for continual analysis of the tank's leak status. See page 13
for more information about these methods.
What Are The Regulatory Requirements?
ATG systems must be able to detect a leak of 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 ATG
systems can also detect a leak of 0.1 gallon per hour with the
probabilities listed above.
-im No later than October 13, 2018, you must begin performing the
following 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
These activities must be performed according to
manufacturer's requirements; a nationally recognized code of
practice; or requirements determined by your implementing
agency to be as protective of human health and the
environment.
An unexplained presence of water in the tank is considered an
unusual operating condition. If you find water in your tank, you
You must obtain a conclusive
pass or fail result within the
30 day monitoring period. If
the test report is
inconclusive, you must use
another method of release
detection for that 30 day
monitoring period. An
inconclusive result means
you have not performed
release detection for that 30
day period.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
must investigate and correct the source of the water. Suspected
releases must be reported to your implementing agency within 24
hours or another period specified by your implementing agency.
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 on
the product in the tank, detecting water may be difficult, but it
is possible to do. Products such as ethanol-based fuels may not
form a water bottom
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 equipment manufacturer or installer. Check
the method's documentation to confirm that it will meet regulatory
requirements and your needs.
With the exception of some continuous ATG systems evaluated to
perform on manifolded tanks, each tank at a site must be equipped
with a separate probe. Check the method's documentation to
determine if the ATG system can be used with manifolded tanks.
For more information, see continuous in-tank leak detection
requirements on page 13. The ATG system probe is connected to a
console that displays product level information and the results of
the monthly test. Printers can be connected to the console to
record this information.
ATG systems are often equipped with alarms for high and low
product level and high water level.
For ATG systems used for static release detection testing, no
product can be delivered to the tank or withdrawn from it for one
to six hours before the monthly test or during the test, which
generally takes one to six hours. These times vary depending on
the specific ATG system model. Check with your equipment
manufacturer or installer. You may also find information on your
ATG system on NWGLDE's list of release detection evaluations at
www.nwglde.org.
An ATG system can be programmed to perform a test more often
than once every 30 days. EPA recommends this practice.
Some ATG systems may be evaluated to test at relatively low
capacities, for example, 25 percent or 30 percent. Although the
product level at such capacities may be valid for the test
equipment, it may not appropriately test all portions of the tank
that routinely contain product. The ATG leak test must be run and
tank tested at the capacity to which it is routinely filled.
The ATG system probe is
installed through an
opening, which is different
than the fill pipe, on the top
of the tank.
ATG systems can be linked
with computers at remote
locations, from which the
system can be programmed
or read.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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Continuous In-Tank
Leak Detection
UPDATED
The 2015 federal UST regulation added continuous in-
tank leak detection (CITLD) as a release detection
method and establishes requirements for its operation
and maintenance. 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.
Will You Be In Compliance?
You can use CITLD methods for tanks installed on or before
April 11, 2016. The system incrementally gathers
measurements to determine a tank's leak status within the 30-
day monitoring period. Some methods address pipelines and
have been verified to meet pipeline performance standards.
These methods are capable of meeting the pipeline release
detection requirements. See release detection requirements
for piping on page 33.
How Does The Release Detection Method Work?
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 by
allowing the system to gather incremental measurements to
determine the release status of the tank at least once every 30
days.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
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UPDATED
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.
No later than October 13, 2018, you must begin performing the
following 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
These activities must be performed according to
manufacturer's instructions; a nationally recognized code of
practice; or requirements determined by your implementing
agency to be as protective of human health and the
environment.
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 your implementing agency within 24
hours or another period specified by your implementing agency.
You must obtain a conclusive
pass or fail result within the
30 day monitoring period. If
the test report is
inconclusive, you must use
another method of release
detection for that 30 day
monitoring period. An
inconclusive result means
you have not performed
release detection for that 30
day period.
SeeNWGLDEat
rg, which is a
source for check ing whether
your CITLD method meets
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 on
the product in the tank, detecting water may be difficult, but it
is possible to do. Products such as ethanol-based fuels may not
form a water bottom.
CITLD methods may allow for
monitoring larger tank
capacities and higher system
throughputs. However, these
methods have limitations as
well.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
The 2015 federal UST regulation added statistical
inventory reconciliation (SIR) as a release detection
method. For this method, a trained professional uses
sophisticated computer software to conduct a statistical
analysis of inventory, delivery, and dispensing data, which is
gathered periodically and supplied regularly to the vendor.
Will You Be In Compliance?
SIR, when performed according to the vendor's
specifications, meets federal release detection requirements
for USTs and piping installed on or before April 11, 2016.
SIR with a 0.2 gallon per hour release detection capability
meets the federal requirements for monthly monitoring for
tanks. SIR with a 0.1 gallon per hour release detection
capability meets the federal requirements as an equivalent to
tank tightness testing. If it has the capability of detecting
even smaller leaks, SIR meets the federal requirements for
line tightness testing as well. See release detection
requirements for piping on page 33.
How Does The Release Detection Method Work?
SIR analyzes inventory, delivery, and dispensing data
collected over a period of time to determine whether or not a
tank or piping is leaking a regulated substance.
Each operating day, the product level is measured using a
gauge stick or other tank level monitor. You must 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 conducts a statistical analysis of the data to
determine whether or not your UST system is leaking. The
SIR vendor provides you with a test report of the analysis.
Alternatively, you can purchase SIR software, which
performs this same analysis and provides a test report from
your own computer.
Some methods combine aspects of automatic tank gauges
with statistical inventory reconciliation. In these methods,
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
UPDATED
sometimes called hybrid methods, a gauge provides liquid level
and temperature data to a computer running SIR software, which
performs the analysis to detect leaks.
SIR methods are distinguished from continuous in-tank leak
detection methods by how inventory, delivery, and dispensing data
are processed; they provide a determination of the release status of
the tank or piping. SIR data is 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,
uninterrupted or nearly uninterrupted manner.
What Are The Regulatory Requirements?
SIR methods must report a quantitative result with a calculated
leak rate, be able to detect a leak at least 0.2 gallons 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 SIR methods can also
detect a leak of 0.1 gallons per hour with the probabilities listed
above.
No later than October 13, 2018, you must begin performing the
following 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 walkthrough inspection records for one year
For other equipment:
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
These activities must be performed according to
manufacturer's instructions; a nationally recognized code of
practice; or requirements determined by your implementing
agency to be as protective of human health and the
environment.
The SIR method must use a threshold that does not exceed
one-half the minimum detectable leak rate (MDL). Pd is the
probability of detection and Pfa is the probability of false
alarm in a normal probability distribution. SIR data is
typically analyzed through the calculation of the reportable
EPA's Introduction To
Statistical Inventory
Reconciliation For
Underground Storage Tanks
at
explains how
to do statistical inventory
reconciliation.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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values of MDL and the leak declaration threshold T are related
as follows:
MDL is always greater than T
Pd = (1 - Pfa), then MDL = 2 times T (that is, the
threshold is equal to 1A MDL)
Any analysis of data indicating a threshold value greater than
one-half MDL should be appropriately investigated as a
suspected release.
You must keep on file for one year the test reports. You must also
keep on file for five years documentation that the SIR method used
for your system is capable of detecting a leak rate of 0.2 gallons
per hour with a probability of detection of 95 percent and
probability of false alarm.
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 your implementing agency within 24
hours or another period specified by your implementing agency.
Documentation on the
method's capability of
meeting performance
requirements must reflect
the way the method is used in
thefleld.
UPDATED
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 on
the product in the tank, detecting water may be difficult, but it
is possible to do. Products such as ethanol-based fuels may not
form a water bottom.
If you are considering using a SIR method, check the method's
documentation to confirm that it will meet regulatory requirements
and your specific UST system needs.
A SIR method's ability to detect releases declines as throughput
increases. If you are considering using a SIR method for high
throughput UST systems, check the method's documentation to
confirm that it will meet regulatory requirements and your needs.
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 can produce
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.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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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.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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Tank Tightness Testing
With Inventory Control
This method combines periodic tank tightness testing with
monthly inventory control. Inventory control involves taking
measurements of tank contents and recording amount
received and pumped each operating day, as well as
reconciling all this data at least once every 30 days. Every
five years, this combined method must also include a
tightness test, which is a sophisticated test performed by a
trained professional.
Will You Be In Compliance?
When performed according to the manufacturer's
specifications, periodic tank tightness testing combined with
monthly inventory control can temporarily meet the federal
release detection requirements for tanks installed on or
before April 11, 2016. This method does not detect piping
leaks. This combined method can be used only for 10 years
after the tank was installed.
These two release detection methods must be used together
because inventory control alone does not meet the federal
requirements for monthly release detection for tanks. Line
tightness testing, a separate type of tightness testing, is also
an option for underground piping; see release detection
requirements for piping on page 33.
We discuss both tank tightness testing and inventory control
below. We discuss tank tightness testing first, followed by
inventory control. Tank tightness testing is also used in
combination with manual tank gauging as described on page
24. In addition, tank tightness testing may be used to
investigate a suspected release.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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Tank Tightness Testing
How Does The Release Detection Method Work?
Tightness tests, also referred to as precision tank tests, include a
variety of methods. These methods are divided into two
categories: volumetric and nonvolumetric.
Volumetric test methods generally involve precisely measuring in
milliliters or thousandths of an inch the change in product level in
a tank over time. Additional characteristics of this category of tank
tightness testing include:
Changes in product temperature also must be precisely
measured in thousandths of a degree at the same time as
level measurements, because temperature changes cause
volume changes that interfere with finding a leak.
The product in the tank must be at a certain minimum level
before testing. This often requires adding product from
another tank on site or purchasing additional product.
A net decrease in product volume, which you find by
subtracting out volume changes caused by temperature,
over the time of the test indicates a leak.
A few of these methods measure properties of product that
are independent of temperature, such as mass, and so do not
need to measure product temperature.
There are many nonvolumetric test methods. These methods can
be distinguished by what they test or which areas of the UST
system they test. The methods:
Involve acoustics that interpret an ultrasonic signal.
Use vacuum or pressure decay with gain or loss of
pressure, respectively, to determine whether there is a hole
in the tank.
Test either the wetted portion of the tank, which contains
product, or the ullage, which is the unfilled portion of the
tank.
Involve tracer compounds circulated through the UST
system, which test strategically placed sampling ports
outside the UST system.
Except for tracer compounds used for both volumetric and
nonvolumetric test methods, the following generally apply:
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.
Some tightness test methods require the tester measure and
calculate by hand. Other tightness test methods are highly
Although not typically done,
you may use tank tightness
testing to meet the monthly
release detection
requirement. This test must
meet performance standards
of 0.1 gallon per hour leak
rate with probability of
detection at least 95 percent
and probability of false
alarm not to exceed 5
percent.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
automated. After the tester sets up the equipment, a
computer controls the measurements and analysis.
Some ATG systems are capable of meeting the regulatory
requirements for tank tightness testing and may be
considered an equivalent method. Check with your
implementing agency.
What Are The Regulatory Requirements?
The tightness test method must be able to detect a leak at least 0.1
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.
No later than October 13, 2018, you must begin testing your
release detection equipment annually to make sure it is
working properly.
Tank tightness testing is typically performed by a qualified
testing company. Qualified testing companies periodically
calibrate and maintain their equipment according to
applicable standards. If your implementing agency allows use
of ATG systems or other system controllers for tank tightness
testing, you must follow the testing procedures required for
ATG systems. See page 10.
You must perform a tightness test at least every 5 years. You may
use this combination method temporarily for up to 10 years after
the UST was installed. After 10 years, you must use a different
release detection method.
Anything Else You Should Consider?
For most methods, a testing company performs the test. You
should observe the test.
Depending on the method, tank tightness testing can be used on
tanks of varying capacity and tanks containing gasoline and diesel.
Many test methods have limitations on the capacity of the tank or
the amount of ullage, which is the unwetted portion of the tank that
should not be exceeded. Methods that use tracer chemical analysis
do not have limitations on tank capacity. If you are considering
using tightness testing for products other than gasoline or diesel,
discuss the method's applicability with the manufacturer's
representative. Check the method's documentation to confirm that
it will meet regulatory requirements and your specific UST system
needs.
Manifolded tanks generally should be isolated and tested
separately.
Procedure and personnel, not equipment, are usually the most
important factors in a successful tightness test. Therefore, well-
Under the federal UST
regulation, this combination
method can only be used for
10years after the tank was
installed. However, most
states have secondary
containment with interstitial
monitoring requirements.
Therefore, you may not be
able to use this combination
method. Check with your
implementing agency.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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trained and experienced testers are very important. Some
implementing agencies have tester certification programs.
UPDATED
Inventory Control
How Does The Release Detection Method Work?
Inventory control requires frequent measurements of tank contents
and math calculations that let you compare your stick inventory,
which is what you measured, to your book inventory, which is
what your recordkeeping indicates you should have. Some people
call this process inventory reconciliation. If the difference between
your stick and book inventory is too large, your tank may be
leaking.
UST inventories are determined each operating day by using a
gauge stick and recording the data 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 operating 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 percent of the tank's flow-
through volume plus 130 gallons of product, the UST may be
leaking.
What Are The Regulatory Requirements?
Inventory control must be used in combination with tank tightness
testing performed at least every 5 years to meet the monthly
release detection requirement. This combination method can only
be used for up to 10 years after the tank was installed. This
method may not be used for UST systems installed after April 11,
2016.
The gauge stick must reach the bottom of the tank and be 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 in the tank.
Product dispensers must be calibrated to the applicable weights
and measures standards.
No later than October 13, 2018, you must begin performing the
following on your release detection equipment annually to
make sure it is working properly.
EPA's Doing Inventory
Control Right at
www. eoa, ao v/ust/doin a-
inventorv-control-riaht-\
underground-storage-tanks
explains how to do inventory
control. The booklet also
contains standard
recordkeeping forms.
You may need to get a
corrected tank chart if your
tank is not level.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
For hand held non-electronic equipment, such as tank gauge
sticks:
Check for operability and serviceability
Keep walkthrough inspection records for one year
These activities must be performed according to
manufacturer's instructions; a nationally recognized code of
practice; or requirements determined by your implementing
agency to be as protective of human health and the
environment.
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 your implementing agency within 24
hours or another period specified by your implementing agency.
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 on
the product in the tank, detecting water may be difficult, but it
is possible to do. Products such as ethanol-based fuels may not
form a water bottom.
Inventory control is a practical, commonly used management
practice that does not require closing down the tank operation for
long periods.
The accuracy of tank
gauging can be increased by
spreading product finding
paste on the gauge stick
before taking measurements
or by using in tank product
level monitoring devices.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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Manual Tank Gauging
Manual tank gauging requires keeping the tank undisturbed
for at least 36-58 hours each week, during which the contents
of the tank are measured twice at the beginning and twice at
the end of the test period. At the end of each week, you
compare the results to the standards shown on page 25 to see
if your tank is leaking.
Will You Be In Compliance?
Manual tank gauging can be used only on tanks containing
2,000 gallons or less. Tanks containing 1,000 gallons or less
can use this method alone, if they meet specified diameter
requirements discussed below. Tanks from 1,001 to 2,000
gallons, and tanks between 551 and 1,000 gallons that do not
meet the specified diameters, can temporarily use manual
tank gauging when it is combined with tank tightness testing.
Under the federal UST regulation, this combined method can
be used only for 10 years after the tank was installed. This
method may not be used for UST systems installed after
April 11,2016.
Manual tank gauging detects leaks only from tanks; this
method does not detect piping leaks. For requirements for
piping, see release detection requirements for piping on page
33.
How Does The Release Detection Method Work?
You must take four measurements of the tank's contents, two
at the beginning and two at the end of a 36-58 hour period,
during which nothing is added to or removed from the tank.
See the table on page 25.
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, you compare the calculated change in tank
volume to the standards shown in the table on page 25. If the
calculated change exceeds the weekly standard, the UST may
be leaking. Also, you must compare the averages of the four
weekly test results to the monthly standard in the same way.
See the table below.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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What Are The Regulatory Requirements?
You must take liquid level measurements with a gauge stick that is
marked to measure the liquid to the nearest one-eighth of an inch.
No later than October 13, 2018, you must begin performing the
following 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 walkthrough inspection records for one year
You must perform these activities according to manufacturer's
instructions; a nationally recognized code of practice; or
requirements determined by your implementing agency to be
as protective of human health and the environment.
Manual tank gauging may be used as the sole method of release
detection for tanks with a capacity of 550 gallons or less and
capacities between 551 and 1,000 gallons with a 48 inch or 64 inch
diameter. All other tanks using manual tank gauging must
combine the method with tank tightness testing. These tanks may
use the combined method for up to 10 years after installation.
After 10 years, you must use another release detection method.
See the other sections of this booklet for allowable monthly
monitoring methods.
Table Of Test Standards For Manual Tank Gauging
Minimum Weekly Monthly
Tank Size Duration Standard ,7j »
Of Test (1test) J£*
Up to 550 gallons
551-1,000 gallons
(when tank diameter
is 64")
551-1,000 gallons
(when tank diameter
is 48")
551-1,000 gallons
(also requires
periodic tank
tightness testing)
1,001 -2,000 gallons
(also requires
periodic tank
tightness testing)
36 hours
44 hours
58 hours
36 hours
36 hours
10 gallons
9 gallons
12 gallons
13 gallons
26 gallons
5 gallons
4 gallons
6 gallons
7 gallons
13 gallons
Under the federal UST
regulation, you may only use
this combination method for
10years after the tank was
installed. However, most
states have secondary
containment with interstitial
monitoring requirements.
Therefore, you may not be
able to use this combination
method. Check with your UST
implementing agency.
An unexplained presence of water in the tank is considered an
unusual operating condition. If you find water in your tank, you
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
must investigate and correct the source of the water. You must
report suspected releases to your implementing agency within 24
hours or the period specified by your implementing agency.
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 on
the product in the tank, detecting water may be difficult, but it
is possible to do. Products such as ethanol-based fuels may not
form a water bottom.
You can perform manual tank gauging yourself. Correct gauging,
recording, and correct math are the most important factors for
successful tank gauging. The accuracy of manual tank gauging
can be increased by spreading product-finding paste on the gauge
stick before taking measurements.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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Groundwater monitoring detects the presence of liquid
product floating on the groundwater near the tank and along
the piping runs. To discover if released product has reached
groundwater, these wells can be checked periodically using
hand-held equipment or continuously with permanently
installed equipment.
UPDATED
Will You Be In Compliance?
When installed and operated according to the manufacturer's
instructions, a groundwater monitoring system can meet the
federal release detection requirements for USTs and piping
installed on or before April 11, 2016. Monitoring of a
groundwater monitoring system is required at least once
every 30 days for the tank.
No later than October 13, 2018, if you use groundwater
monitoring, you must begin keeping records of a site
assessment, for as long as you use this method, showing
that the monitoring system is installed properly. Site
assessments performed after October 13, 2015 must be
signed by a licensed professional.
How Does The Release Detection Method Work?
Groundwater monitoring involves the use of permanent
monitoring wells placed close to the UST, with the wells
extending below the groundwater level. The wells are
checked at least every 30 days for the presence of product
that has leaked from the UST and is floating on the
groundwater.
The two main components of a groundwater monitoring
system are the monitoring wells, which are typically at least
4 inches in diameter, and the monitoring device.
Electronic detection devices may be permanently installed in
the well for automatic, continuous measurements for released
product.
Manual devices range from a bailer, which collects a liquid
sample for visual inspection, to a device that can be inserted
into the well to electronically indicate the presence of leaked
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
product. Manual devices must be used to check each monitoring
well at least once every 30 days.
Before installation, a site assessment is necessary to determine the
soil type, groundwater depth and flow direction, and the general
geology of the site. A trained professional must perform this
assessment.
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
implementing agencies have developed rules for monitoring well
placement.
What Are The Regulatory Requirements?
Groundwater monitoring can only be used if the stored substance
does not mix with water and floats on top of water.
If groundwater monitoring is used as the sole method of release
detection, the groundwater must be less than 20 feet below the
surface, and the soil between the well and the UST must be sand,
gravel, or other coarse materials.
Product detection devices must be able to detect one-eighth inch or
less of leaked product on top of the groundwater.
Monitoring wells must be properly designed and sealed to keep
them from becoming contaminated from outside sources.
Wells should be placed in the UST backfill so they can detect a
leak as quickly as possible.
Monitoring wells must be secured and clearly marked.
No later than October 13, 2018, you must begin performing the
following 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 walkthrough inspection records 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
No later than October 13,
2018, if you use vapor
monitoring or groundwater
monitoring, you must begin
keeping records of a site
assessment, for as long as
you use these methods,
showing that the monitoring
system is set up properly. If
you do not have a site
assessment for your vapor
monitoring or groundwater
monitoring,you will need to
have one conducted. Site
assessments conducted after
October 13,2015 must be
signed by a licensed
professional.
Groundwater at times may
be more than 20 feet from
the ground surface, due to
seasonal water table
variations. This can result in
the depth to groundwater
requirement not being met.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
UPDATED
Ensure floats move freely, the shaft is not damaged, and
cables are free of kinks and breaks
Test manual electronic devices, such as portable probes
Keep records of these tests for three years
These activities must be performed according to
manufacturer's requirements; a nationally recognized code of
practice; or requirements determined by your implementing
agency to be as protective of human health and the
environment.
Anything Else You Should Consider?
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.
Some states may allow you to use groundwater monitoring
wells to perform vapor monitoring. Check with your
implementing agency to determine what is acceptable. If
allowed, unless an analysis is performed and valid
documentation regarding use of the wells for vapor monitoring
during low water table conditions is identified in the site
assessment, the wells will be restricted for groundwater
monitoring only.
In the event of a confirmed release at an UST site,
groundwater monitoring is no longer acceptable to meet the
release detection requirement unless the site is remediated and
a new site assessment is conducted.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
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Vapor Monitoring
UPDATED
Vapor monitoring measures either product vapors in the soil
around the UST, referred to as passive monitoring, or special
tracer chemicals added to the UST, referred to as active
monitoring.
Will You Be In Compliance?
When installed and operated according to the manufacturer's
instructions, vapor monitoring can meet the federal release
detection requirements for tanks and piping installed on or
before April 11, 2016. Monitoring of a vapor monitoring
system at least every 30 days is required for the tank.
No later than October 13, 2018, if you use vapor
monitoring you must begin keeping records of a site
assessment, for as long as you use this method, showing
that the monitoring system is installed properly. Site
assessments performed after October 13, 2015 must be
signed by a licensed professional.
How Does The Release Detection Method Work?
Vapor monitoring can be categorized into two types: active
monitoring and passive monitoring. Active monitoring is
also referred to as chemical marker monitoring or as tracer
compound analysis.
Passive monitoring detects or measures vapors from released
product within monitoring wells placed in the soil around the
tank to determine if the tank is releasing regulated
substances.
Active monitoring samples for the presence of a tracer
compound outside the UST system that was introduced in the
tank or underground piping.
Fully automated vapor monitoring systems have permanently
installed equipment to continuously or periodically gather
and analyze vapor samples and activate a visual or audible
alarm when a release is detected, independent of actions by
an UST system operator.
Active monitoring requires the installation of monitoring
wells or sampling points strategically placed in the tank
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
May 2016
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UPDATED
backfill or along pipe runs to intercept special chemicals that, in
the event of a release, are detected in the sampling points.
Manually operated vapor monitoring systems range from
equipment that immediately analyzes a gathered vapor sample to
devices that gather a sample, which must be sent to a laboratory for
analysis. Manual systems must be used at least once every 30 days
to monitor a site. If active monitoring is performed, it must be
done at least every 30 days by qualified technicians.
Before installation of any vapor monitoring system for release
detection, a site assessment is necessary to determine the soil type,
groundwater depth and flow direction, and the general geology of
the site. Only a trained professional can do this.
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
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 implementing agencies
have developed requirements for monitoring well placement.
What Are The Regulatory Requirements?
The UST backfill must be sand, gravel, or another material that
will allow petroleum vapors or tracer compound to easily move to
the monitor.
The backfill must be clean enough that previous contamination
does not interfere with detecting a current release.
The substance stored in the UST must vaporize easily so that the
vapor monitor can detect a release. For example, some vapor
monitoring systems do not work well, if at all, with diesel fuel.
High groundwater, excessive rain, or other sources of moisture
must not interfere with operation of vapor monitoring for more
than 30 consecutive days.
Monitoring wells must be secured and clearly marked.
No later than October 13, 2018, you must begin performing the
following 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 walkthrough inspection records for one year
For other equipment:
To ensure they are properly
operating, vapor monitoring
devices must be periodically
calibrated according to the
manufacturer's instructions.
No later than October 13,
2018, if you use vapor
monitoring or groundwater
monitoring, you must keep
records of a site assessment,
for as long as you use these
methods, showing that the
monitoring system is set up
properly. If you do not have
a site assessment for your
vapor monitoring or
groundwater monitoring,
you will need to have one
conducted. Site assessments
conducted after October 13,
2015 must be signed by a
licensed professional.
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
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UPDATED
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
These activities must be performed according to
manufacturer's instructions; a nationally recognized code of
practice; or requirements determined by your implementing
agency to be as protective of human health and the
environment.
Anything Else You Should Consider?
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.
In the event of a confirmed release at an UST site, vapor
monitoring is no longer acceptable to meet the release
detection requirement unless the site is remediated and a new
site assessment is conducted.
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Release Detection For
Underground Piping
Owners and operators of federally regulated UST systems
must have a release detection method, or combination of
methods for connected underground piping that routinely
contains product.
UPDATED
Will You Be In Compliance?
When installed and operated according to the manufacturer's
specifications, the release detection methods discussed here
meet the federal regulatory requirements for underground
piping systems. Your UST may have suction or pressurized
piping, which are discussed below.
Piping installed or replaced after April 11, 2016 must
have secondary containment with interstitial monitoring,
except for suction piping that meets requirements
discussed below. In addition, pressurized piping must
have an automatic line leak detector.
What Are The Regulatory Requirements For
Suction Piping?
No release detection is required if the suction piping system
has these characteristics: below-grade piping that operates
under atmospheric pressure; enough slope so that the product
in the pipe can drain back into the tank when suction is
released; and only one check valve, which is located as close
as possible beneath the pump in the dispensing unit. If a
suction line is to be considered exempt based on these
characteristics, there must be some way to verify that the line
actually has these characteristics.
Suction piping installed on or before April 11, 2016 that does
not have all of the characteristics noted above must use one
of the following release detection methods:
A line tightness test at least every three years
Monthly interstitial monitoring
Monthly vapor monitoring
Monthly groundwater monitoring
Monthly statistical inventory reconciliation
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
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UPDATED
UPDATED
Continuous in-tank leak detection only for methods that
include pipelines
Other monthly monitoring that meets performance
standards or approved by your implementing agency
Suction lines are not pressurized very much during a tightness test
of 7 to 15 pounds per square inch.
Interstitial monitoring, vapor monitoring, groundwater monitoring,
continuous in-tank leak detection, and statistical inventory
reconciliation have the same regulatory requirements for piping as
they do for tanks. See earlier sections of this booklet for
information on those methods.
Suction piping installed or replaced after April 11, 2016 that
does not meet all of the design standards above must have
secondary containment with interstitial monitoring.
What Are The Regulatory Requirements For Pressurized
Piping?
Pressurized piping installed on or before April 11, 2016 must have
an automatic line leak detector (ALLD) that:
Shuts off flow, or
Restricts flow, or
Triggers an audible or visual alarm
The ALLD must be designed to detect a release at least 3 gallons
per hour at a line pressure of 10 pounds per square inch within 1
hour, with a probability of detection of at least 95 percent and a
probability of false alarm of no more than 5 percent.
You must also use one of these other methods:
Annual line tightness test
Monthly interstitial monitoring
Monthly vapor monitoring
Monthly groundwater monitoring
Monthly statistical inventory reconciliation
Continuous in-tank leak detection, only for methods
that include pipelines
Other monthly monitoring that meets performance
standards or approved by your implementing agency
The line tightness test must be able to detect a leak at least 0.1
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
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
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
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UPDATED
pressures lower than 1.5 times operating pressure, the leak rate to
be detected must be correspondingly lower.
Interstitial monitoring, vapor monitoring, groundwater monitoring,
continuous in-tank leak detection only for methods that include
piping, and statistical inventory reconciliation have the same
regulatory requirements for piping as for tanks. See earlier
sections of this booklet for information on those methods.
Pressurized piping installed or replaced after April 11, 2016
must have secondary containment with interstitial monitoring.
No later than October 13, 2018, you must begin annual
operability testing of ALLDs to determine they are capable of
detecting a leak of 3 gallons per hour at 10 pounds per square
inch line pressure within 1 hour by simulating a leak at or
below this leak rate. You must keep records of these tests for 3
years.
The test must be performed according to manufacturer's
instructions; a nationally recognized code of practice; or
requirements determined by your implementing agency to be
as protective of human health and the environment.
How Do The Release Detection Methods Work?
If your implementing agency
allows an ALLD to meet other
aspects of the pressurized
piping dual release detection
requirement (that is,
monthly monitoring or line
tightness testing), the annual
operability test must be
conducted to ensure the
applicable performance
standard can be met.
Simulating a leak at 0.2 gph
for monthly monitoring or
0.1 gph for line tightness
testing is one way to ensure
this.
UPDATED
ALLDs
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 release is detected, a flow restrictor keeps the
product flow through the line well below the usual flow rate. If a
suspected release is detected, a flow shutoff completely cuts off
product flow in the line or shuts down the pump.
Both automatic flow restrictors and shutoffs are permanently
installed directly into the pipe or the pump housing.
A continuous alarm system constantly monitors line conditions and
immediately triggers an audible or visual alarm if a release is
suspected. An automated interstitial monitoring system can be set
to operate continuously independent of an operator and sound an
alarm, flash a signal on the console, or even ring a telephone in a
manager's office when a release is suspected.
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 §
All mechanical and electronic
ALLDs must meet the annual
testing requirement.
A self diagnostic system does
not meet the annual testing
requirement, unless the
system performs a simulated
leak test.
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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
least one year.
Electronic and mechanical components of the system,
including shutoff devices, sensors, pressure or vacuum
monitors, must be tested annually for proper operation.
Records of the test must 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. Keep the
results for at least three years.
Line Tightness Testing
During a line tightness test, the line is taken out of service and
usually pressurized 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 of 7 to 15 pounds per square inch.
Most line tightness tests are performed by a testing company. You
should 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 be impossible 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, which often
include electronic line leak detectors connected to an ATG system,
may meet the requirements of monthly monitoring or a line
tightness test.
Check with your implementing agency to determine what is
allowed.
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Government Links
U.S. Environmental Protection Agency's Office
of Underground Storage Tanks:
www.epa.gov/ust. EPA's UST compliance
assistance: www.epa.gov/ust/resources-owners-
and-operators
State UST program contact information:
www. epa. gov/ust/underground-storage-tank-ust-
contacts#states
Tanks Subcommittee of the Association of State
and Territorial Solid Waste Management Officials
(ASTSWMO): www.astswmo.org
New England Interstate Water Pollution Control
Commission (NEIWPCC): www.neiwpcc.org
Industry Codes And Standards
www.epa.gov/ust/underground-storage-tanks-usts-laws-
regulations#code
Other Organizations To Contact For UST
Information
http://nwglde.org/
Release Detection For Underground Storage Tanks And Piping: Straight Talk On Tanks
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SERA
United States
Environmental Protection
Agency
United States Environmental Protection Agency
5401R
Washington, DC 20460
EPA 510-K-16-003
May 2016
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