United States
Environmental Protection
Agency
Solid Waste and Emergency
Response
(OS-420 WF)
EPA510-F-93-004
April 1993
&EPA UST Program Facts
Detecting Leaks:
Technical Regulations
U.S. Environmental Protection Agency
(EPA) regulations
EPA designed the technical regulations for
underground storage tanks (USTs) to reduce
the chance of releases from USTs, increase
the likelihood of finding releases quickly
when they do occur, and secure prompt
cleanup. Owners and operators are
responsible for detecting, slopping, and
cleaning up leaks and spills.
Leak detection requirements for existing
USTs (installed before 1988)
In addition to meeting 1998 requirements for
upgrading (see Leak Prevention fact sheet in
this series), owners and operators of USTs
installed before 1988 must use one of the
leak detection methods described below to
detect leaks from both tanks and piping.
Deadlines for compliance with the leak
detection requirements have been phased in
based on the tank's age. (See chart.)
Leak detection requirements for new
USTs (installed after 1988)
Owners and operators of USTs installed
after 1988 also must use one of the leak
detection methods described below to detect
leaks from tanks and piping. (See chart.)
Leak detection methods
Experts have developed several methods to
help UST owners ascertain whether their
tanks arc tight. Owners and operators must
choose a leak detection method that is listed
in the regulations, meets a performance
standard described in the regulations, or
is approved by their state agency as
being at least as stringent in detecting
leaks as the methods and standards in the
regulations.
The choice of a method is important
because of the inherent problems in
monitoring a tank: the UST is emptied
and refilled periodically; the product
level underground is not visible to the
eye; and factors such as temperature can
affect measurement.
• Internal types.
Tank tightness testing does not
require permanent installation of
equipment or large capital
expenditures. Line tightness
testing is a similar method for
checking the UST's connective
pipes for leaks.
Tank tightness testing must be
used in conjunction with
inventory control. Inventory
control is an ongoing accounting
system, like a checkbook, that
owners have typically used as a
business practice to keep track of
their product and to detect leaks.
This method, tank tightness
testing and inventory control, can
only be used on USTs installed
or upgraded within the last 10
years.
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Leak Detection Requirements For USTs
Type of Tank
or Piping
New tanks
(installed after
December 1988)
Existing tanks
Pressurized piping
Suction piping
Minimum Requirements
Monthly monitoring* or monthly inventory
control and tank tightness testing every 5
years.**
Monthly monitoring* or monthly inventory
control and annual tank tightness testing
(only permissible until December 1998) or
monthly inventory control and tank
tightness testing every 5 years.** Very
small tanks may be able to use manual
tank gauging.
Automatic line leak detector and either
annual line testing or monthly monitoring*
(except automatic tank gauging).
Monthly monitoring* (except automatic tank
gauging) or line testing every 3 years.
There are no requirements if the system
has the characteristics known as "safe
suction" described in the final regulations.
Deadlines
At installation
If installation
date unknown:
If installed
before 1965:
1965-1969:
1970-1974:
1975-1979:
1980-1988:
• Existing piping
• New piping
• Existing piping
• New piping
December 1 989
December 1989
December 1990
December 1991
December 1992
December 1993
December 1 990
At installation
Same as
existing tanks
At installation
'Monthly monitoring includes automatic tank gauging, vapor monitoring, interstitial monitoring, groundwater monitoring,
and other approved methods.
"For new tanks, permissible only for 10 years after installation; for existing tanks, permissible only for 10 years after
adding corrosion protection and spill/overfill prevention or until December 1998, whichever date is later.
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Automatic tank gauging
systems are permanently installed
in USTs and provide automated,
accurate inventory information
and leak testing. Among the
more expensive methods, they
require minimal operator
involvement, cause few service
interruptions, and are relatively
precise and sensitive. They do
not check piping and may not
work on very large tanks.
Manual tank gauging, an easy
and inexpensive release detection
method only for small USTs, can
detect leaks as small as 0.2
gallons per hour. It requires
shutting down tanks and does not
check piping.
Statistical inventory
reconciliation is a newer method
that uses sophisticated computer
software to determine whether a
tank system is leaking. The
computer conducts a statistical
analysis of inventory, delivery,
and dispensing data collected
over a period of time and
provided by the operator to a
vendor.
External types.
Soil vapor monitoring is a
release detection method that is
used primarily for petroleum
UST systems. As petroleum
leaks from a tank or its
connective pipes, some of the
liquid evaporates and spreads into
the surrounding soil, where it can
be detected by a vapor sensor.
Groundwater monitoring
utilizes permanent observation
wells placed close to the tank
system. They must be checked
periodically for evidence of
leaking material floating on the
groundwater. This method is
effective only at sites where
groundwater is within 20 feet of the
surface.
Secondary containment and
interstitial monitoring involves
placing a barrier outside the primary
tank and a release detection device
between the inner and outer barriers
- a space called the interstitial
space. Either vapor or liquid
monitors may be used, and the
system detects leaks in tanks and
piping. New USTs holding
chemicals must use this method.
Reporting and record-keeping
requirements for all tanks
In general, UST owners and operators need
to report to the regulatory authority only at
the beginning and end of the UST system's
operating life. Reportable information
includes data about the type of UST,
certification of correct installation, and
description of the leak detection device.
Owners and operators also must report to
the regulatory authority suspected and
confirmed releases, as well as follow-up
actions planned or taken to correct damage
caused by the leaking UST.
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 if an owner or operator can't
afford to comply with leak detection
requirements?
The cost of complying with prevention and
other requirements will be a burden to some
owners and operators, especially those with
older tanks. Seventeen states have
established financial assistance programs
that serve to mitigate the overall economic
impact of the UST regulatory program. In
six of those states, owners and operators are
eligible to receive grants or low-interest
loans to put leak detection methods in place.
Detecting Leaks: Technical Regulations ix one
in a series of fact sheets about underground
storage tanks (USTs) and leaking USTs. The
series is designed to help EPA, other federal
officials, and state authorities answer the most
frequently asked questions about USTs with
consistent, accurate information in language the
layperson can understand. Keep the fact sheets
handy as a resource. This fact sheet addresses
federal regulations. You may need to refer to
applicable state or local regulations, as well.
For more information on UST publications, call
the RCRAISuperfund Hotline at 800 424-9346.
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