United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-91/037 Sept. 1991
EPA Project Summary
Chemicals Stored in USTs:
Characteristics and Leak
Detection
Joseph W. Maresca, Jr., and Robert W. Hillger
The regulations Issued by the U. S.
Environmental Protection Agency
(EPA) In 1988 require, with several ex-
ceptions, that the Integrity of under-
ground storage tank (UST) systems
containing petroleum fuels and haz-
ardous chemicals be routinely tested.
The regulatory standards for leak de-
tection In tanks containing hazardous
chemicals are more stringent than for
those containing petroleum motor fu-
els. The report summarized here de-
scribes (1) the regulatory standards
for leak detection In tanks containing
hazardous chemicals, (2) the types of
chemicals being stored, (3) the char-
acteristics of the tanks In which these
chemicals are stored, (4) the effective-
ness of tank tightness tests and auto-
matic tank gauging systems for
detection of leaks In tanks containing
chemicals other than petroleum, and
(5) the approaches to leak detection
that are being Implemented by tank
owners and operators.
This Project Summary was devel-
oped by EPA's Risk Reduction Engi-
neering Laboratory, Cincinnati, OH, to
announce key findings of the research
project that la fully documented in •
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
On September 23, 1989, EPA issued
technical standards and corrective action
requirements (40 CFR 280) for owners
and operators of USTs that are used for
petroleum products and hazardous chemi-
cal substances. (A hazardous chemical is
any substance defined by the Comprehen-
sive Environmental Response, Compen-
sation, and Liability Act.) Section 280.42 of
the regulations presents the requirements
for storing hazardous substances. There
are five options for release detection in
new tank and pipeline systems used to
store hazardous substances. Four of these
options require some form of secondary
containment and periodic monitoring or leak
detection within the secondary containment.
The fifth option allows for leak detection
without secondary containment safeguards
providing that (1) the method or system is
at least as effective as the ones allowed
for use in petroleum USTs in Section 280.43
(b) through (h) of the regulations; (2) infor-
mation is provided about the chemical and
physical properties of the stored substance,
the health risks associated with the sub-
stance, the characteristics of the site, and
corrective action technologies that can be
used in case of a release; and (3) approval
from the implementing agency is received
before installation and operation of the
UST system. Existing USTs dp not have to
meet these requirements until 1998. Until
that date, existing USTs need only meet
the requirements for petroleum UST sys-
tems given in Section 280.41. After 1998,
all existing USTs containing hazardous
substances will be subject to the same
requirements as new tanks.
Tank tightness tests and automatic
tank gauges (ATGs) are the two most
frequently used release detection meth-
ods for petroleum USTs. Either one, when
used in conjunction with monthly inven-
tory reconciliation, is acceptable as the
Printed on Recycled Paper
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fifth option and thus will satisfy the require-
ments delineated in the regulations. (This
option should not be used, however, If an
accidental release cannot be environmen-
tally tolerated even though detection may
be immediate). The release detection re-
quirements for tank tightness tests and
ATGs are given in Section 280.43 (c) and
(d) of the regulations. Tank tightness tests
must be capable of detecting a 0.1-gal/hr
leak with a probability of detection of 0.95
and a probability of false alarm of 0.05,
and ATGs must be capable of detecting a
leak of 0.2 gal/hr with the same probabili-
ties of detection and false alarm as a tank
tightness test. Because an ATG conducts
tests more frequently, its performance re-
quirement is not as stringent as that of a
tank tightness test.
Over the next 8 yr, owners and opera-
tors of existing hazardous-substance USTs
will be using volumetric leak detection sys-
tems (for example, tank tightness tests)
that were developed primarily for use with
petroleum products. As noted above, own-
ers/operators may continue to use these
systems after 1998 if the requirements
specified in the fifth option are met. ft is
therefore critical to determine whether volu-
metric leak detection systems can be re-
lied on when used on tanks containing
nonpetroleum chemicals. The performance
requirements that were developed for tank
tightness tests and ATGs were based on
extensive measurements in underground
storage tanks containing petroleum motor
fuels such as gasoline and diesel. Hazard-
ous substances can differ from these fuels
in density, coefficient of thermal expan-
sion, viscosity, and vapor pressure. More-
over, since the list of hazardous substances
is extensive, the variability of these proper-
ties is expected to extend over a broad
range. The effects of these properties on
volumetric testing, and therefore on the
performance of tank tightness tests and
ATGs, have not been fully assessed. Such
assessment must be done if the owners
and operators of existing hazardous sub-
stance USTs are to have any assurance
that they can depend on tank tightness
tests and ATGs to guard against acciden-
tal releases.
Objectives
The objectives of this project were (1)
to identify the chemicals being stored in
USTs and the characteristics of the tank
systems used to store these chemicals; (2)
to assess the influence of the physical
properties of the stored products on the
performance of volumetric leak detection
systems; and (3) to identify, as weH as
determine the effectiveness of, the ap-
proaches to release detection that owners
and operators of tanks containing hazard-
ous chemicals are taking to achieve com-
pliance with the regulations.
Report Organization
The work done in fulfilling these objec-
tives was presented in three technical pa-
pers [1-3]. These are included as
Appendices A, B, and C of the full report
summarized here. Each paper addressed
one objective of the project. The main
conclusions and recommendations derived
from this work are summarized below.
Conclusions
Characteristics of Tanks
Containing Nonpetroleum
Chemicals
A survey of the registered tanks con-
taining chemicals other than petroleum was
conducted [1]. The following states partici-
pated in the survey: California, Delaware,
Florida, Illinois, Indiana, Maine, Massa-
chusetts, Minnesota, Missouri, Montana,
New York, Ohio, Texas, Virginia, and Wis-
consin. This survey enlarged on earlier
work [4] analyzing data provided by New
York, California, and the Chemical Manu-
facturers Association (CMA).
The results of the present survey sug-
gest that tanks containing hazardous and
nonhazardous chemicals comprise up to
2% of the total UST population nationwide.
Of the chemical tanks surveyed, approxi-
mately 50% contained hazardous sub-
stances and the remaining 50% contained
chemicals that are not regulated. The most
striking feature to emerge from the survey
of chemical tanks is the wide variety of
substances that are stored. Analysis of the
survey data indicates, however, that roughly
80% to 90% of the stored hazardous chemi-
cals are organic solvents, and, of these,
the most common are acetone, toluene,
xylene, methanol, and methyl-ethyl ketone.
These five chemicals account for the con-
tents of approximately 49% of the tanks
containing hazardous materials.
Not only were the most commonly
stored substances assessed, but also the
ranges of tank capacity, age, and con-
struction materials. The average tank ca-
pacity was approximately 7,200 gal, with
over 27% of the tanks having capacities of
10,000 gal or more. The mean age of the
tanks was roughly 18 yr, and over 86%
were fabricated from steel. In view of the
survey's findings, it can be expected that
substantial upgrading of tank installations
will occur over the next 8 yr.
Analysis of the Applicability of
Volumetric Leak Detection
Systems to Tanks Containing
Hazardous Chemicals
The performance of volumetric leak
detection systems that could be used to
meet the tank tightness testing and the
ATG release detection option was ana-
lyzed [2]. The results show that (1) how
well the volumetric leak detection system
works is directly related to the coefficient of
thermal expansion of the stored product
and (2) the waiting period required for the
effects of structural deformation to subside
is essentially the same for all values of
density of the stored fluid (even though
higher densities produce greater deforma-
tion-induced volume changes immediately
after any product-level change). When a
leak detection system is used with a chemi-
cal having a coefficient of thermal expan-
sion higher than that of the product used in
the evaluation of the system, the system's
performance will be lower than it was in the
evaluation. Because gasoline has a higher
coefficient of thermal expansion than that
of many chemicals, a system evaluated
with a gasoline product can be used with
such chemicals and still maintain a similar
level of performance. (This may not be
true, however, if the system was evaluated
with diesel, which has a coefficient of ther-
mal expansion 35% less than that of gaso-
line.)
For a large portion of the tank popula-
tion, internal leak detection methods such
as tank tightness tests and ATGs are a
viable approach to testing tank integrity.
The physical properties of the most com-
monly stored chemicals are generally simi-
lar to those of unleaded gasoline, upon
which the quantitative performance stan-
dards in the regulations are based. In addi-
tion, the size and construction of a majority
of chemical tanks closely approximate
those from which the data used to support
the regulations were developed. Assum-
ing, therefore, that practical details of ma-
terial compatibility and safety have been
addressed, it would seem that only mini-
mal extrapolations of current knowledge
are needed for volumetric leak detection
systems to be applied to storage tanks
containing chemicals.
Currently Used Approaches to
Leak Detection
Two types of organizations were infor-
mally surveyed by telephone: those that
own and operate tank systems containing
hazardous substances and those that pro-
vide tank testing services to such organi-
zations [3]. The object of the survey was to
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determine the type and effectiveness of
the leak detection systems and the inven-
tory control practices being used to test
tank systems.
Even though a diverse cross section of
organizations was contacted, the responses
obtained during the telephone survey
should not be interpreted quantitatively.
Because the number of organizations was
very limited and the survey was not statis-
tically designed or statistically analyzed,
the results should be interpreted cautiously.
The temptation to generalize, particularly
about the status of regulatory compliance,
should be avoided unless additional data
are gathered. The following observations
are noteworthy, however, either because
the response was overwhelming or be-
cause it was ambiguous.
Based on the discussions conducted
during the course of the survey, one would
tend to conclude that most owners and
operators of chemical tanks are actively
involved in upgrading their tank systems to
minimize the liability associated with any
accidental releases. Most organizations
said that they were replacing their under-
ground storage tanks with aboveground
tanks whenever possible. When this was
not possible, tank and piping systems with
secondary containment, primarily double-
wall tanks and piping, were being used;
none of the organizations contacted was
considering the use of single-wall tanks or
piping in conjunction with the release de-
tection option. What is not dear from the
survey is how much time will be required
for those organizations currently upgrad-
ing their tank systems to complete the
process. If the time required for upgrading
a tank system exceeds 1 yr, the regula-
tions require that the tank system be tested
in the interim by means of methods com-
monly used on tanks containing petroleum.
None of these organizations used in-
ventory control as a means of leak detec-
tion. It also appears that this method of
leak detection would be difficult to apply
because of the lack of metering devices or
the lack of accuracy in the metering de-
vices being used.
The tank testing firms indicated that
approximately 5% of their tests were con-
ducted on tanks containing hazardous
chemicals, a figure that is slightly higher
than the estimated percentage of such
tanks in the United States. This response
is inconsistent with that obtained from the
13 tank-owning organizations responding
to the survey; none of these indicated that
they were using or planning to use such
services. This inconsistency is probably
due to the small size of the survey.
Recommendations
Although the number and volume of
LIST systems containing hazardous chemi-
cals is small, it is important to ensure that
good leak detection practices—ones that
are in compliance with state and federal
regulations—are being used.
This project made no attempt to assess
the status of regulatory compliance by own-
ers and operators of UST systems contain-
ing hazardous chemicals.
The principal recommendation of this
project is that a survey be conducted (1) to
assess the level of compliance on the part
of owners and operators and (2) to deter-
mine whether guidance documents in sup-
port of compliance efforts are needed and
would be effective.
The full report was submitted in fulfill-
ment of Contract No. 68-03-3409 by Vista
Research under the sponsorship of the
U.S. Environmental Protection Agency.
References
1. R. W. Hillger, J. W. Starr, and M. P.
MacArthur. Characteristics of Under-
ground Storage Tanks Containing
Chemicals. Accepted for publication
by ASTM. April 1991.
2. J. W. Starr. R. F. Wise, J. W.
Maresca, Jr., R. W. Hillger, and A. N.
Tafuri. Volumetric Leak Detection in
Underground Storage Tanks Contain-
ing Chemicals. Accepted for publica-
tion in Proceedings of the 84th Annual
Meeting and Exhibition of the Air and
Waste Management Association,
Vancouver, B.C., Canada (15-17
June 1991).
3. R. F. Wise, J. W. Starr, J. W.
Maresca, Jr., R. W. Hillger, and A. N.
Tafuri. Leak Detection in Under-
ground Storage Tanks Containing
Hazardous Chemicals. Accepted for
publication in Proceedings of the 17th
Annual Research Symposium, Risk
Reduction Engineering Laboratory,
Off ice of Research and Development,
U.S. Environmental Protection
Agency, Cincinnati, Ohio (3-5 April
1991).
4. I. Lysyj, R. W. Hillger, J. S. Fartow.
and R. Field. A Preliminary Analysis
of Underground Storage Tanks Used
for CERCLA Chemical Storage. Pro-
ceedings of the Thirteenth Annual
Research Symposium, Hazardous
Waste Engineering Research Labo-
ratory, Office of Research and De-
velopment, U.S. Environmental
Protection Agency, Cincinnati, Ohio
(July 1987).
ifV.S. GOVERNMENT PRINTING OFFICE: 1991 - 548-028/40M*
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Joseph W. Maresca, Jr., is with Vista Research, Inc., Mountain View, CA 94042; and the
EPA author Robert W. Hlllger (also the EPA Project Officer, see below) is with the
Risk Reduction Engineering Laboratory, Edison, NJ 08837.
The complete report, entitled "Chemicals Stored in USTs: Characteristics and Leak
Detection' (Older No. PB91-219592/AS; Cost: $17.00, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Edison, NJ 08837
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
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Penalty for Private Use $300
EPA/600/S2-91/037
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