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RISK BULLETIN
UNDERGROUND STORAGE TANK MANAGEMENT
Leak Detection and Integrity Testing
Introduction
Underground storage tanks (USTs) are widely used across
the nation. Their types and usage vary dramatically from
storage of fuel to explosive gases. It has been estimated
that there are more than 660,000 operating USTs
regulated by USEPA and state agencies. Of these tanks,
USEPA has estimated that approximately 35% are not in
operational compliance with both release detection and
release prevention requirements. Although there has been a
marked decrease in failure rates of USTs and reports of
leaking USTs since enactment of USEPA’s UST regulations,
according to industry statistics an approximate 1% to 1.5%
of operating USTs will fail in a given year.
Effective leak detection and
integrity testing procedures are the cornerstone of UST
management programs. Without proper leak detection and/or
integrity testing, tank failures have the potential to go
undetected and result in extensive remediation. Sites
contaminated by leaking USTs also have the potential to
result in costly bodily injury, property damage, and legal
defense claims.
Understanding UST leak detection and
integrity testing requirements applicable to your facility
requires knowledge of UST regulations, tank construction
and features, approved leak detection methods, and
approved tank testing methods. This knowledge should be
incorporated into a comprehensive UST management program
that is implemented to minimize environmental risks.
UST
Regulations
Federal and state regulations
To gain an understanding of the
requirements of UST owners in selecting and maintaining
leak detection and integrity testing systems, it is
important to understand the regulatory requirements.
Unfortunately, there is no single government regulation
which governs all USTs. Most of the regulations concerning
USTs are contained in USEPA’s UST technical standards in
40 CFR Parts 280 and Part 281 and individual state and
territorial program standards in 40 CFR Part 282.50 –
282.105.
UST systems are defined as ”a tank
and any underground piping connected to the tank that has
at least 10% of its combined volume underground”. Tanks
are typically regulated by their contents. In general,
regulated USTs include those containing petroleum products
and hazardous substances listed in 101(14) of CERCLA and
listed in 40 CFR 302. Additionally, USTs may be regulated
if they contain RCRA hazardous waste as characterized by
USEPA in 40 CFR 261.
Exclusions to federal UST compliance
requirements are provided in 40 CFR 280 including, but not
limited to:
- farm and
residential tanks of 1,100 gallons or less holding motor
fuel used for non-commercial purposes;
- tanks storing heating oil used on
the premises where it is stored;
- tanks on or above the floor of
underground areas such as basements or tunnels;
- septic tanks and systems for
collecting stormwater and wastewater;
- flow-through process tanks; and
- emergency spill and overfill
tanks.
Although unregulated, these tanks
have the potential to release their contents to the
environment if not managed properly. As such, it is
considered an industry best practice to develop a formal
tank management program for these tanks including periodic
integrity testing.
All regulated USTs and piping must
have corrosion protection for metallic components; spill
protection; and overflow prevention. Other USEPA
requirements include financial responsibility,
recordkeeping, notification of releases, corrective
action, and UST closure. Financial responsibility
mechanisms are required for owners or operators of USTs
containing petroleum products to ensure adequate funding
or insurance is available for corrective action or
closure. It is important to note that USTs containing
hazardous substances are required to meet the same
physical requirements, but not the financial
responsibility clause.
States may be approved by USEPA to
establish UST programs and manage compliance efforts.
Currently, more than 30 States are USEPA-approved to
administer UST programs. This means that owners and
operators of USTs in these states do not need to comply
with two sets of regulations (state and federal) that may
be conflicting. Once their programs are approved, states
have the lead role in UST program enforcement. In states
without an approved program, USEPA works with state
officials to coordinate UST enforcement actions.
Industry codes and standards
It is also important to note the role
of industry codes and standards with regard to UST
construction, leak detection and integrity testing.
Federal UST regulations often require that industry codes
and standards be followed (where applicable) to ensure
that UST systems work properly. For example, all UST
systems must be designed, constructed, and protected from
corrosion in accordance with a code of practice developed
by a nationally recognized association or independent
testing laboratory. USEPA has also included the use of
industry codes for other sections of the rule, such as
upgrading, repairing, and closing USTs.
Industry codes and standards provide
a means for improving methods, developing alternative
methods, and updating standards for UST system management
in a timely manner. Examples of organizations and
standards referenced by USEPA include:
- American National Standards
Institute (ANSI),
- American Petroleum Institute
(API),
- American Society for Testing and
Materials (ASTM),
- National Association of Corrosion
Engineers (NACE),
- National Fire Protection
Association (NFPA), and
- National Leak Prevention
Association (NLPA)
- National Work Group on Independent
Leak Detection Evaluations (NWGLDE).
Emerging Regulations and
Requirements
The Energy Policy Act of 2005
included significant amendments to Subtitle I of RCRA
known as the Underground Storage Tank Compliance Act of
2005 (USTCA). USTCA compliance became effective in 2007
and imposed provisions that were expected to have
significant impacts on owners and operators of USTs and
USEPA and States regulating USTs including:
- requiring that States inspect all
USTs at least every 3 years,
- requiring that USEPA publish
training guidelines for UST operators,
- requiring UST facilities to have
tank and piping secondary containment to protect
groundwater, including new USTs located near potable
public water supply systems
- providing evidence of manufacturer
and installer financial responsibility (in each state
receiving federal UST funding),
- requiring States to establish UST
installer certification/licensing (for certain projects)
- prohibiting use of MTBE in motor
vehicle fuel no later than December 31, 2014 (in states
electing to eliminate MTBE use), and
- requiring the establishment of UST
recordkeeping systems and making them available to the
public.
Tank Construction And Features
UST systems consist of a number of
key components in addition to the tank itself. These
components include, the tank, piping, pumps, dispensers,
overfill protection, leak detection, access ports, vents,
and corrosion protection. Depending upon tank usage, there
may be other components as well. Most of the tank system
components are potential leak sources, and must be
maintained and treated as critical system parts. UST
systems may also be comprised of external components such
as groundwater or vapor monitoring systems installed
nearby to meet leak detection regulatory requirements.
Tanks themselves are made from a
variety of materials including steel, clad steel, jacketed
steel, and fiberglass. UST sizes typically range from a
small 250 gallon tank weighing about 3,000 pounds up to a
20,000 gallon storage tank which can be 50 or 60 feet long
and weigh in excess of 75,000 pounds. Tank features which
assist in the prevention, identification, and release of
tank contents include:
-
secondary containment outside of the tank to physically
contain released materials
- level alarms to prevent tank
overfills;
- interstitial monitoring between
the primary tank and/or piping wall and a secondary
wall;
- vapor recovery systems to prevent
the atmospheric release of volatile emissions;
- piping release detection including
release alarms, shutoff devices, and flow restrictors
It is critically important that all
components of the tank system be well maintained. Many
tank failures occur in the piping or dispensing systems
where extensive use may cause stress and wear in joints,
gaskets, etc.
Leak Detection
For assessment purposes, USEPA
considers USTs to fall into three main categories:
operating, closed, and abandoned. All operating, regulated
USTs are required to have leak detection. USEPA provides
guidance for leak detection, tank testing and monitoring
on their website and in various guidance documents. Many
state agencies provide guidance as well.
In USEPA’s basic tank testing
handbook (http://www.epa.gov/swerust1/index.htm)
there are dozens of methods listed for testing and
monitoring. USEPA does not endorse any particular method,
but provides details on techniques they believe will meet
environmental regulatory requirements when applied
properly. USEPA also references the National Work Group on
Leak Detection Evaluations (NWGLDE) (http://www.nwglde.org/),
which is comprised of USEPA and State UST regulators that
independently evaluate leak detection methods for
conformance to regulatory requirements.
Leak detection methods fall into four
general categories: internal (tank liquid level
measurements), external (installed outside the tank
system), interstitial (monitoring area between UST and
secondary containment) and piping (line-leak detectors or
integrity testing). USEPA outlines the following basic
leak detection methods in 40 CFR 280:
- Automatic tank gauging
- Interstitial monitoring
- Groundwater monitoring
- Vapor monitoring
- Inventory control and tank
tightness testing
- Manual tank gauging only
- Manual tank gauging and tank
tightness testing
- Statistical inventory
reconciliation and
- Other methods (typically require
agency approval)
As noted, these methods and various
other methods used alone or in combination are acceptable
for regulatory compliance.
The technology associated with these
four general categories of leak detection and the various
USEPA approved methods can be further subdivided into
three broad categories: Electronic Leak Detection (ELD);
Line Leak Detection (LLD) and Mechanical Leak Detection (MLD).
ELD methods are used to detect
changes in pressure or volume automatically. These units
are often self-calibrating, making calculations of
pressure and temperature unnecessary. The units are
connected to electronic recording devices or computers to
keep track of changes which could indicate a potential
leak. ELDs are highly accurate and can detect very small
leaks. LLD is a variation of ELD, and uses similar
technology and methods applied to UST piping and lines.
MLD is a general term for a large
variety of testing methods, including those conducted
external to the UST system. Typically MLD consists of a
sensor device that is located within the interstitial
space between a tank and its secondary containment, or
within an overflow area, or within the tank itself. This
generalized sketch of a UST system shows where a sensor
might be located. This sensor can vary in type and
sensitivity and is generally linked to a computerized
monitor that registers continuous or peak readings.
Figure 2: Generalized Sketch of a UST System
Another commonly used MLD method
relies on a gauging stick calibrated to tank
specifications. This method is not sensitive enough to
detect small leaks, is generally acceptable for small
tanks (<2,000 gallons), and is used in conjunction with
other methods such as inventory control and tank tightness
testing.
Inventory control is a MLD method
comprised of continually comparing the product volume
dispensed from a tank to the volume received over a set
period of time. Discrepancies indicate that a leak is
likely. This method also has low sensitivity – about 0.1
gallons per hour. It is used together with tank tightness
testing and tank gauging.
Tank Tightness Testing
Tank tightness testing is only
required upon the installation of a new tank and when used
in combination with inventory control methods for
compliance with leak detection requirements as per 40 CFR
280. However, periodic tank tightness testing is
considered a best management practice for
unregulated/exempt USTs. This is typically the only
definitive way to ascertain the integrity of an
unregulated UST system that is not equipped with leak
detection. The frequency of unregulated tank integrity
testing depends on a company’s risk tolerance, but annual
testing is a common benchmark for proactive tank owners.
Tightness testing protocols must meet
certain sensitivities specified in 40 CFR 280 and/or as
certified by NWGLDE. These methods consist of a variety of
volumetric testing to determine leak rate or nonvolumetric
testing that may include: pressure (air) testing,
hydrostatic (water) testing, ultrasonic (acoustic)
testing, or colorimetric (dye/tracer) testing.
A common volumetric tank tightness
testing method is to observe a tank and its contents
undisturbed for a period of at least 36 hours. A net
decrease over time indicates a potential leak. It is
important to take temperature and pressure considerations
into the calculation since these greatly affect volume
readings. It should also be noted that overfill methods
are far more accurate than partial fill methods. In
overfill, the volume change is easier to gauge since the
contents are measured in the fill neck of the tank. With
the small diameter of the neck, a small volume change
produces a relatively large depth change – thus making
readings more accurate.
UST Management Programs
Developing an operation and
maintenance (O&M) plan is critical to maintaining and
monitoring an UST system in accordance with regulations
and most importantly, a program that prevents releases and
reduces impacts to human health and the environment. An
effective plan includes: a description of the equipment
located onsite (including release detection, spill and
overfill protection, and corrosion protection); inspection
procedures, including the frequency of inspections and
required elements; and an outline of response actions to
be taken in the event of an identified or suspected
release.
An UST management program for larger
companies with multiple locations should include a tank
schedule for each site that outlines tank age, content,
construction details, and monitoring requirements. An
effective program should identify responsible parties and
training requirements. A tracking system combined with an
auditing program should be implemented to ensure ongoing
regulatory requirements and best management practices are
fulfilled.
USEPA has developed a guide entitled
“Operating and Maintaining Underground Storage Tank
Systems” to assist tank owners with development of a
management program (http://www.epa.gov/oust/pubs/ommanual.htm).
Conclusion
The storage of material within
underground tanks is convenient and allows for more
efficient use of commercial space. However, failure to
manage risks associated with material stored in UST
systems may result in severe impacts to human health and
the environment. Understanding UST leak detection,
integrity testing requirements, and management practices
is essential in preventing or minimizing bodily injury and
property damage claims, remediation expenses, and legal
defense expenses. Tank owners should ensure leak detection
compliance in accordance with federal and state
requirements, implement a proactive integrity testing
program for unregulated UST systems, and implement
comprehensive UST Management Programs that ensure proper
operations, maintenance and emergency response.
References
1.
USEPA list of UST publications with executive
summaries - http://www.epa.gov/swerust1/pubs/
2.
ISOnet - Engineering and Safety On-Line –
Liability: Underground Storage Tanks, LB-50-40.
3.
http://info.iso.com/
4.
40 CFR Part 280 Technical Standards and
Corrective Action Requirements for Owners and Operators of
Underground Storage Tanks (UST)
5.
40 CFR Part 281 Approval of State Underground
Storage Tank Programs
6.
40 CFR Part 282 Approved Underground Storage
Tank Programs
7.
40 CFR Part 261 Identification and Listing of
Hazardous Waste
Information accurate as of July, 2008..
No part of this publication may be
reproduced without permission of the XL Insurance
companies. This publication is intended for general
information purposes only. Contents should not be
construed or used as legal advice or opinion.
XL Insurance • Risk Control Division • 520 Eagleview
Boulevard, PO Box 636, Exton, PA 19341 • Phone:
800-327-1414 • Fax: 610-458-7285 • www.xlinsurance.com/environmental
© 2008, X.L. America, Inc. All rights reserved.
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