United States
                Environmental Protection
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

                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

                   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

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.

   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.


Characteristics of Tanks
Containing Nonpetroleum
   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-
   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

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.
   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.

 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
 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*

    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
Center for Environmental Research
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300