OSWER 9380.0-24
EPA 540/R95/041
PB95-963538
United States Environmental Protection Agency
EPA LINER STUDY
Report to Congress
Section 4113(a) of the Oil Pollution Act of 1990
May 1996
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TABLE OF CONTENTS
Page
ACRONYMS . . . ; v
t
EXECUTIVE SUMMARY vii
PURPOSE '. vii
SCOPE OF THE STUDY vii
SUMMARY OF FINDINGS - viii
Universe of Facilities viii
Evidence of Spills ix
Technical Feasibility x
RECOMMENDATIONS . . .' , xii
1. INTRODUCTION 1
(
1.1 PURPOSE 1
1.2 BACKGROUND ..... - 1
-1.3 STUDY APPROACH .' 2
1.4 ORGANIZATION OF REPORT , 3
2. BACKGROUND ON ASTs 5
2.1 PROFILE OF AST FACILITIES AND ASTs 5
2.1.1 'Profile of AST Facilities 5
2.1.2 Profile of ASTs .' 9
2.2 OIL DISCHARGES FROM ASTs 11
2.3 STATUS OF ASTs NATIONWIDE 15
2.3.1 Federal Reporting Requirements 17
2.3.2 Discharges from ASTs . . .~ .- 18
2.3.3 Age Profile of ASTs 19
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TABLE OF CONTENTS (Continued)
3. EXISTING REGULATIONS AND INDUSTRY PRACTICES FOR LINER
SYSTEMS , 25
^ i
3.1 REVTEW OF FEDERAL AND STATE AST REGULATIONS 25
3.1.1 Federal Regulations ....,..,.. :....:. 25
3.1.2 State Regulations . V. 26
3.2 INDUSTRY PRACTICES AND STANDARDS 33
3.3 ESTIMATE OF THE NUMBER OF FACILITIES ALREADY
USING LINERS OR RELATED SYSTEMS 34
4. TECHNICAL FEASIBILITY AND UNIT COST OF LINERS AND
RELATED SYSTEMS 37
4.1 OVERVIEW 37
4,2 DESCRIPTION OF MODEL FACILITIES .. 37
4.3 LINER SYSTEM DESIGNS AND PRACTICES 48
4.3.1 Liner Materials Currently in Use .'.... 50
4.3.2 Cost of Liners ,...., ' 50
4.3.3 Liner Use Practices 50
4.3.4 Liner Effectiveness 51
4.3.5 Liner Designs Used in this Study 52
4.4 LINER FEASIBILITY EVALUATION 59
4.4.1- Protection of the Environment and Construction Ease 61
4.4.2 Estimated facility Costs 62
4.5 LEAK DETECTION METHODS 67
5. RECOMMENDATIONS . 69
REFERENCES '. . . ; . . 73
APPENDIX A: STATE REGULATIONS ; 75
APPENDIX B: MODEL FACILITIES . . 79
n
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LIST OF EXHIBITS
Title
Exhibit 2-1:
Exhibit 2-2:
Exhibit 2-3:
Exhibit 2-4:
Exhibit 2-5:
Exhibit 2-6:
Exhibit 2-7:
Exhibit 3-1:
Exhibit 3-2:
Exhibit 4-1:
Exhibit 4-2:
Exhibit 4-3:
Exhibit 4-4:
Exhibit 4-5:
Exhibit 4-6:
Exhibit 4-7:
Exhibit 4-8:
Page
Estimated Number of Facilities Meeting the
SPCC Storage Capacity Thresholds .- 7
Distribution of ASTs by Age Category ' 12
Distribution of ASTs by Storage Capacity Tier 13
Distribution of ASTs by Storage Capacity by Data Source .... 14
(
Case Studies 16
Percentage of ASTs by Age Category 20
Percent Corrosion Failure in Each Age Group 22
Summary of State Regulatory Review for the Nine States .... 27
Estimated Number of Facilities Not Currently
Required to Install Liners 35
Model Facility 1: Small End User - Supply 39
Model Facility 2: Small End User - Storage/Motor Fuel 40
Model Facility 3: Small Bulk Storage - Distribution 41
Model Facility 4: Medium Bulk Storage - Distribution 42
Model Facility 5: Large Bulk Storage - Distribution 43
Model Facility 6: Large Oil Terminal - Distribution 44
Summary of Characteristics of Model Facilities 45
Categorization of Facilities Not Currently Required
to Install Liners 47
m
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LIST OF EXHIBITS (Continued)
Title
Exhibit 4-9:
Exhibit 4-10:
Exhibit 4-11:
Exhibit 4-12:
Exhibit 4-13:
Exhibit 4-14:
Exhibit 4-15:
Exhibit 4-16:
Exhibit 4-17:
Exhibit 4-18:
Exhibit A-l:
Exhibit B-l:
Exhibit B-2:
General Schematic: Aboveground Storage Facility 53
Details: Containment Dike and Liner 54
Details: Liner at Base of Vertical Tank ,55
Details: Foundation Penetration 56
Details: Access Road ' _ 57
Details: Undertank Containment System 58
Comparative Analysis of Liners for Environmental
Protection and Construction Ease
60
Comparative Cost Analysis of Liner Materials by
Model Facility 1 63
Annual Operation and Maintenance Costs 64
Estimated Liner Capital Cost Per Gallon of
Storage Capacity 66
State Regulations ; 76
Typical Storage Capacities for Facilities from
Previous EPA Analysis 79
Categorization of Facilities Not Currently
Required to Install Liners
80
IV
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ACRONYMS
API American Petroleum Institute
AST Aboveground Storage Tank
CERCLA Comprehensive Environmental Response, Compensation,
and Liability Act
CFR Code of Federal Regulations
CWA Clean Water Act
DOT Department of Transportation
EPA Environmental Protection Agency
ERNS Emergency Response Notification System
GCS Ground Water Characterization Study
HDPE , High Density Polyethylene
HMTA Hazardous Materials Transportation Act
HWST Federal Hazardous Waste Storage Tank
MMS Minerals Management Service
NFPA National Fire Protection Association's Flammable and
Combustible Liquids.Code
NRC National Response Center
ODCP Oil Discharge Contingency Plan
OPA Oil Pollution Act '
OSC On-Scene Coordinator
PVC Polyvinyl chloride
RCRA Resource Conservation and Recovery Act
SPCC Spill Prevention, Control, and Countermeasures
SIC Standard Industrial Classification
UST Underground Storage Tank
VADEQ Virginia Department of Environmental Quality
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EXECUTIVE SUMMARY
EIPOSE
Section 4113(a) of the Oil Pollution Act of 1990 (OPA) requires that: "The
sident shall conduct a study to determine whether liners or other secondary means of
tainment should be used to prevent leaking or to aid in leak detection at onshore
lities used for the bulk storage of oil and located near navigable waters." In
cutive Order 12777, the President delegated authority to the U.S. Environmental
tection Agency (EPA) to conduct this study.
EPA investigated the nature and magnitude of leaking oil at onshore facilities with
veground storage tanks (ASTs) that are used for the bulk storage of oil and that are
ited near navigable waters. The Agency also assessed the technical feasibility of using
rs and related systems to detect leaking oil and to prevent leaking oil from
laminating soil and, by way of ground-water pathways, navigable waters. This report
Congress, which presents the findings and recommendations of EPA's study, fulfills the'
uirements of Section 4113(a) of the OP A.
M>E OF THE STUDY
After the OPA became law, EPA staff from the Offices of Emergency and
nedial Response and Congressional Liaison met with Congressional staff to discuss
scope of the study toibe conducted under OPA Section 4113(a). Based on these
ussions, the Agency decided that the study would focus on the feasibility of using
rs and related systems to address oil leaking from ASTs to secondary containment
ctures (e.g., berms, dikes) and to soil underneath ASTs. An assessment of the
iibility of using liners to address oil leaking from other parts of AST facilities, such as
c truck transfer racks and underground piping, was not specifically addressed during
study. However, because underground piping was identified as a significant potential
rce of leaking oil at AST facilities, the Agency's recommendations also address this
rce of contamination.
- / * '
For this study, EPA defined a liner as an engineered system that makes secondary
tainment structures more impervious. EPA assessed the technical feasibility of
ailing liners made from synthetic materials as well as earthen materials within
mdary containment structures and under ASTs (i.e., undertank liners). EPA also
:ssed the feasibility of installing double bottoms on vertical ASTs as "other secondary
ms of containment," which could be used in place of undertank liners. The Agency
examined other technologies to aid in leak detection and looked at available data on
r costs.
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EPA evaluated the effectiveness of liners and double bottoms in reducing the
potential for leaking oil to reach soil and navigable ^waters (i.e., surface waters) via
ground-water pathways. Oil discharges to unlined secondary containment systems, such
as episodic spills, and continuous leaks from the bottoms of ASTs may contaminate soil
and have the potential to be transported downward to ground water. Because ground
water often is hydrologically connected to surface water, a ground-water oil plume has
the potential to migrate and contaminate surface water. Furthermore, oil that repeatedly
contaminates soil as a result of frequent spills may form oil-saturated soil zones, which
have the potential to contaminate surface water when precipitation migrates through soil
to surface-water bodies. Based on these considerations, EPA assessed the suitability of
using liner systems to protect ground water and, in turn, navigable waters by evaluating
the effectiveness of these systems in preventing discharged oil from contaminating soil
and ground water.
SUMMARY OF FINDINGS
.Universe of Facilities
EPA estimates that 502,000 onshore facilities have ASTs and store significant
quantities of oil in bulk. Approximately 435,000 of these facilities are required by EPA's
Oil Pollution Prevention regulation (40 CFR Part 112) to develop written plans to
prevent and control oil discharges and install secondary containment systems for ASTs.1
EPA estimates that the number of ASTs located at these 502,000 onshore facilities is
about 1.8 million. A separate study conducted for the American Petroleum Institute
(API) estimates that about 700,000 ASTs are used at facilities in the production, refining,
transportation, and marketing sectors of the petroleum industry.2
In general, there are two categories of ASTs: (1) vertical ASTs, which are
mounted such that the tank bottom rests'" on a foundation at ground level; and (2),
horizontal ASTs, which are supported in saddles such that the tank is suspended above
the ground or floor of a secondary containment structure. The storage capacity of
horizontal ASTs typically ranges from a few hundred gallons up to 20,000 gallons, while
the storage capacity of vertical ASTs typically ranges from several thousand gallons to
1 The Oil Pollution Prevention regulation (40 CFR Part 112) was initially promulgated on December
11, 1973. After passage of the OPA, two sets of revisions to the regulation were,developed. The first set
of revisions was proposed on October 22, 1991 (56 FR 54612) in order to clarify the applicability of the
regulation. The second set of revisions was promulgated on July,!, 1994 (59 FR 34070) to establish
requirements for the development of facility response plans (FRPs). The requirements to develop SPCC
plans and to install secondary containment, as referenced in this document, are included in the original
regulation. For information on state regulations for liners, see Chapter 3 and Appendix A of this
document.
? American Petroleum Institute (API), "Aboveground Storage Tank Survey," prepared by Entropy
Limited, April 1989. This study did not include ASTs at end-user facilities.
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over 10 million gallons! All ASTs have the potential to leak oil, presenting the threat of
environmental contamination.
Evidence of Spills
EPA searched for existing data to estimate the number of leaking ASTs, volume
discharged, and resulting environmental damage. The Agency found that comprehensive
data do not exist to adequately quantify the extent to which the nation's AST inventory is
leaking. Existing Federal regulations require facility owners and operators to report oil
discharges only if they trigger the reporting thresholds of Clean Water Act (CWA)
regulations. Consequently, some leaking oil that contaminates soil and ground water may
not be reported to Federal authorities and, therefore, may not be recorded in national
spill data bases, such as EPA's Emergency Response Notification System (ERNS).
Existing sources of information evaluated by EPA, however, do indicate that a
significant number of ASTs may be leaking or spilling oil. For example, analysis of
ERNS data indicate that about 30 percent of all reported oil discharges from onshore
facilities, or approximately 1,700 spills annually, are to secondary containment areas,
many of which are believed to be unlined. The results of a recent API survey indicate
that 85 percent of refineries, 68 percent of marketing facilities, and 10 percent of
transportation facilities have known-ground-water contamination near their facilities."
Some of these facilities store millions of .gallons of oil in ASTs. A preliminary report
issued by the Virginia Department of Environmental Quality containing statistics on 88
facilities that have 1 million gallons or more of aboveground storage capacity indicates
that 88 percent of these facilities reported ground-water contamination.4 It is not clear
from these data whether this oil contamination js caused by past practices or is
continuing to occur at these facilities. For example, the results of the API survey
referenced above indicate that changes in operation practices, upgraded standards,,and
improved equipment have significantly reduced reported petroleum spills and accidental
releases from ASTs. Spill data also do not allow EPA to determine the extent of oil
contamination caused by different sizes or types of facilities. Furthermore, the data are
not sufficiently detailed to determine whether the contamination is caused by oil
discharging from ASTs or from other areas of the facility. EPAibund during the course
of this study that underground piping located at onshore facilities also is a potentially
significant source, of leaking oil. As one indicator of the number of ASTs that could be
leaking oil and the corresponding volume discharged, EPA obtained data on AST age
and examined the potential relationship between AST age and corrosion rates to
estimate the likelihood that ASTs will develop leaks as "a function of tank age.
3 American Petroleum Institute (API), "A Survey of API Members' Aboveground Storage Tank
Facilities," prepared by API Health and Environmental Affairs Department, July 1994.
4 Virginia Department of Environmental Quality (VADEQ), "The Virginia DEQ Aboveground
Storage Tank Regulations," April 4, 1994.
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Technical Feasibility
EPA investigated the technical feasibility of liner systems, including double
bottoms, by examining the effectiveness of different liner materials and designs for
protecting the environment from oil discharges and evaluating the construction feasibility
of liner systems. The technical feasibility and unit-cost analysis are based on alternative
liner designs for six "model" facilities used to represent the diverse universe of facilities
potentially benefitting from liner system installation. These model facilities ranged from
small end-user facilities with one horizontally mounted 2,000-gallon AST to a large
petroleum bulk terminal with several vertical ASTs with a combined storage capacity of
about 50 million gallons. For these model facilities, 'the alternative designs considered
and evaluations of their effectiveness were based largely on discussions with EPA On-
Scene Coordinators and owners and operators of facilities using, handling, and storing oil
and petroleum products. ,
For the model facilities with vertical ASTs, EPA developed several technically
feasible approaches for installing liners and double bottoms. These approaches include:
Retrofitting the bottom of an AST with a second steel plate (i.e., installing
a double bottom), an interstitial geosynthetic liner on top of the original
bottom, and a leak detection system (e.g., a tell-tale drain);
* Installing a.liner within the secondary containment system around the AST;
Installing a liner, within the secondary containment system around the AST
and retrofitting the bottom of the AST with a second steel plate, an
interstitial geosynthetic liner, and leak detection system; and
Installing a liner within the secondary containment system and installing an >
undertank liner with a leak detection system during construction of a new
AST.
For horizontally mounted tanks, the only option considered was the installation of a liner
throughout the entire secondary containment system. During development of these
options, EPA considered a range of AST sizes and secondary containment systems, such
as structures with pipe penetrations through side walls and those built to accommodate
vehicle access.
EPA evaluated four types of liner materials soil (e.g., clay), concrete,
, geomembranes, and steel - that could be integrated into secondary containment
structures. All four liner materials provide roughly equivalent protection provided that
they are properly installed and maintained. The cost of liners for secondary containment
areas around ASTs varies significantly by material. Although steel and coated concrete
liners were found to provide excellent protection and durability, these systems generally
are considerably more expensive than soil or geomembrane liners.
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Based on the technical feasibility and unit-cost analysis of different liner designs at
model facilities, EPA determined that for large facilities it may be less expensive to
install a complete liner system at a new facility than to retrofit an existing facility.
Depending on the liner type, the cost to install a complete liner system at a new large
bulk terminal can be 30 to 50 percent less than the cost to retrofit liners and double
bottoms at an existing facility. For example, at a new large bulk petroleum terminal
(with about 50 million gallons of storage capacity), a complete liner system is estimated
to cost between $.03 and $.08 per gallon of storage capacity, or roughly between $1.5
million and $4 million. In contrast, the cost to retrofit an existing large bulk terminal
with a complete liner system is estimated to cost between $.07 to $.11 per gallon, or
approximately $3.5 million to $5.5 million. However',, for small end-user facilities,^ the
retrofit costs at existing facilities may not be significantly different from installation costs
at new facilities. For example, depending on the liner type, the estimated-cost to install'a
liner system at an existing small end-user facility (with one horizontally mounted 2,000-
gallon tank) ranges from $2.00 to $4.50 per gallon of storage capacity, or $4,000 to $9,000
on a facility basis, while the estimated liner costs for a new small end-user facility range
from $1.50 to $4.00 per gallon of storage capacity, or $3,000 to $8,000.
The approaches presented above for installing liners and double bottoms at AST
facilities essentially provide two types of protection in preventing leaking oil from
reaching unprotected soil and ground water: protection underneath an AST and
protection within the secondary containment area around the AST. For example,
installing ,a liner only within the secondary containment area around the AST will prevent
oil discharged from the tank into the secondary containment area (e.g., a leak from the
side of the tank) from contaminating soil. However, this system will not detect
discharged oil nor prevent oil from leaking through a corroded AST bottom and reaching
soil, ground water, or surface water. Alternatively, installing a double bottom or
undertank liner with a leak detection system beneath an AST will detect leaking oil and
prevent oil from reaching soil, but will not prevent discharged oil that fills up an unlined
secondary containment system from contaminating soil and possibly ground water. A key
issue related to the effectiveness of liner systems is the extent to which liners are
properly maintained. The relationship between liner effectiveness and maintenance, and
the costs of that maintenance, can vary greatly depending on the purpose and nature of
the liners and the inspection and maintenance requirements. Many AST facility owners
and EPA personnel expressed concern that although certain types of liners require
periodic maintenance to perform effectively, some facility owners may not currently
allocate sufficient resources to liner maintenance activities.
5 In general, the cost to install liner systems at facilities would be better represented in dollars per
gallon of throughput rather than dollars per gallon of storage capacity since throughput is a more accurate
measure of the economic value of the AST; however, EPA lacks sufficient data on average throughput to
present costs on this basis.
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RECOMMENDATIONS
The recommendation of this Rep'ort to Congress is based primarily on the results
of EPA's study of liners as well as insights the Agency has gained over the past 20 years
into the problems posed by onshore AST facilities. As a first step toward addressing the
potential risks to public health and the environment as a result of contamination from
AST facilities located near navigable waters,1 the Agency recommends initiating, through
a Federal Register notice or stakeholder workgroups, a process involving broad public
participation to develop a voluntary program. This process would give stakeholders the
opportunity to share new or additional data and information' to characterize the sources,
causes, and extent of soil and ground-water contamination and efforts underway to
address contamination at AST facilities nationwide. Such data are critical to determining
the most appropriate and effective means to reduce contamination.
As envisioned by EPA, the voluntary program would be designed to encourage
facility owners or operators, through incentives such as technical assistance, cost savings,
and public recognition, to identify and report contamination, take actions to prevent leaks
and spills, and remediate soil and ground-water contamination. This program would
complement the Agency's efforts to develop cleaner, cheaper, and smarter approaches to
environmental problems through innovative solutions that depart from the traditional
regulatory approach. The Agency favors a voluntary; rather than regulatory, approach at
this time in order to provide greater flexibility in addressing contamination at the vast
range of oil storage facility types, sizes, and locations. A voluntary program could focus
more directly on facilities that may pose the greatest hazard to public health and the
environment. For example, the program may initially focus on larger, older facilities, and
facilities located near waters, sensitive areas, or populations. In addition, a voluntary
approach could allow implementation of the most appropriate prevention and cleanup .
activities for each facility. The program would look for incentives for industry to
implement reasonable and cost-effective measures to address existing problems and help
prevent future ones. - .
EPA views such a program as a cooperative effort among EPA, State
governments, industry, and environmental groups. Based on this study's findings, EPA
believes the program should include commitments from facilities to:
Address known contamination and to assure that existing contaminatiori will
, not be allowed to migrate offsite;
Report to appropriate government agencies the status of facility
contamination and actions underway to address any problems;
Adopt the most protective appropriate prevention standards and upgrade
equipment as necessary- and
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* Monitor and/or implement leak detection to ensure that new leaks are
addressed.
Provided stakeholders commit to the voluntary approach, a successful program will entail
the identification of specific actions for participating facilities to undertake and include
means for objectively measuring results.
EPA has evaluated the feasibility of conducting a voluntary program to address
the problem of AST releases arid concluded that a voluntary program is worth pursuing.
Factors that support development of a voluntary program include: (1) the universe of
large AST facilities is easily defined and represented by several large trade associations;
(2) the voluntary program is consistent with the Agency's goal of developing and
promoting innovative approaches to achieve environmental goals; (3) clear, achievable
overall goals are apparent (i.e., to clean up contamination and prevent future releases);
(4) flexible approaches are available to address the problem, thus allowing participants to
implement the program in a tailored manner appropriate to their circumstances; (5) EPA
is committed to providing technical assistance as well as other incentives; and (6) there
are'established industry and state practices and standards that can be used as a basis for
constructing a comprehensive program. , .
In keeping with the Agency's initiatives to develop innovative, common-sense
approaches to environmental problems, EPA supports a voluntary prevention and
cleanup program as a first step in addressing the environmental problem presented by
contamination irom AST facilities. Industry representatives have expressed their support
for such a program as a more cost-effective, flexible alternative than traditional
regulation. EPA fully supports such an attempt, arid believes it will be successful,
provided that it has the full commitment of those involved. , The Agency believes it is
essential- that stakeholders have the opportunity to participate in the development and
execution of this voluntary program and will establish an open process for public input
into the program's design and implementation.
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1. INTRODUCTION
1.1 PURPOSE
Section 4113(a) of the Oil Pollution Act of 1990 (OPA) requires that: "The
President shall conduct a study to determine whether liners or other secondary means of
containment should be used to prevent leaking or to aid in leak detection at onshore
facilities used for the bulk storage of oil and located near navigable waters." In
Executive Order 12777, the President delegated authority to the U.S. Environmental
Protection Agency (EPA) to conduct this study.
t '
This report to Congress presents EPA's study to assess the extent to which liner
systems should be used with ASTs at onshore facilities to detect leaks and/or prevent
leaks from reaching soil, ground water, and surface water.1 As part of this study, EPA
investigated the nature and magnitude of leaking oil at onshore facilities with ASTs that
are used for the bulk storage of oil. The Agency also assessed the technical feasibility of
using liners and related systems to detect leaking oil, and to prevent leaking oil from
contaminating soil and, by way of ground-water pathways, navigable waters. This report
to Congress, which provides recommendations based on EPA's findings, fulfills Section
4113(a)ofOPA.
1.2 BACKGROUND
Concerns about the environmental hazards posed by onshore oil-storage facilities
have grown in recent years as a result of several widely publicized oil discharges from
such facilities, including significant discharges from tank farms in Fairfax, Virginia, in
1990, and in -Sparks, Nevada, in 1989. Such incidents have the potential to cause
widespread damage, including contamination of soil, ground-water and surface-water
supplies, loss of property, and risks to human health. Because several hundred thousand
onshore facilities with ASTs are located throughout the U.S., many near sensitive
environments (including ground water and surface water), discharges from ASTs
represent a potentially significant environmental hazard.
Oil discharges may originate from many parts of an onshore AST facility, including
tanks, loading/unloading areas where oil 'transfers are conducted between tank trucks or
vessels and ASTs, and when oil is transported in underground and abovegrpund piping.
Although liner systems could be installed at certain types of loading/unloading areas and
.other locations at a facility, EPA decided to focus on the feasibility of using liners and
related systems to address oil leaking from ASTs to secondary containment systems and
to soil underneath ASTs. This decision was made after consultations with Congressional
For purposes of this study, "surface water" and "navigable water" are used interchangeably.
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staff about the intent of OPA Section 4113(a). Although the problems posed by oil
discharges at other parts of the facility (including leaks from underground piping) were
not directly investigated during this study, EPA gained valuable insights into the nature of
these problems.
jf
For this study, EPA defined a liner as an engineered system that makes secondary
containment structures more impervious. EPA assessed the feasibility of installing liners
within secondary containment structures and under ASTs (i.e., undertank liners). EPA
also assessed the feasibility of installing double bottoms on vertical ASTs as "other
secondary means of containment," which could be used in place of undertank liners.
Secondary containment liners used in conjunction with double bottoms or undertank
liners are capable of addressing oil discharges from ASTs into secondary containment
areas and to soil underneath vertical ASTs.
JEPA evaluated the effectiveness of liner systems, including double bottoms, in
reducing the potential for leaking oil to reach soil and surface waters via ground-water
pathways. .Oil discharges to unlined secondary containment systems, such as episodic
spills, and continuous leaks from the bottom of ASTs may contaminate soil and have the
potential to migrate downward to ground water. Because ground water often is
hydrologically connected to surface water, a ground-water oil plume has the potential to
migrate and contaminate surface water. Furthermore, oil that repeatedly contaminates
soil as a result of frequent spills may form subsurface oil plumes, which have the
potential to contaminate surface water when precipitation migrates through soil to
sui face-water bodies. Based on these considerations, EPA assessed the suitability of
using liner systems to protect navigable waters by evaluating the effectiveness of these
systems in preventing discharged oil from contaminating soil and ground water.
For purposes of evaluating the technical feasibility of liner systems at onshore
facilities, EPA included as a basis for 'this study the approximately 500,000 onshore
facilities that meet^the oil storage capacity threshold of the Oil Pollution Prevention '
regulation. These facilities have oil storage capacities ranging between several hundred
gallons to several million gallons and are found in the majority of industry sectors. As a
resultj these facilities constitute a diverse and comprehensive group from which to
evaluate the technical feasibility of installing liner systems.
13 STUDY APPROACH
EPA conducted two principal tasks in preparing this study:
Task 1: Gathered'a range of data and information on leaks and spills from
ASTs, types of liner systems, and their costs; and
2 Throughout this study, "liner system" includes both secondary containment liners, undertank liners,
and double bottoms.
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Task 2: -. Conducted a technical feasibility analysis of liner systems for a range
of typical onshore facilities with ASTs.
EPA gathered data on the number and type of onshore facilities storing oil in
bulk, number and type of ASTs facilities and ASTs, and the number and volume of oil
discharges from ASTs. EPA conducted interviews with facility owners and operators,
manufacturers of liner systems, and Federal and State government personnel about the
characteristics of liners systems, including their cost and effectiveness, as well as
operation and maintenance requirements. This information was used to support the
technical feasibility analysis.
EPA conducted a technical feasibility analysis of liner systems by examining the
effectiveness of different liner materials and designs for protecting the environment from
oil discharges and evaluating the construction feasibility of liner systems. The technical
feasibility and unit-cost analysis is based on alternative liner designs for six "model"
facilities used to represent the diverse universe of facilities that meet the oil storage
capacity threshold of the Oil Pollution Prevention regulation. These model facilities
ranged from small end-user facilities with one horizontally mounted 2,000-gallon AST to
a large petroleum bulk terminal with a mix of horizontal and vertical ASTs with a
combined storage capacity of about 50 million gallons. For these model facilities, the
alternative designs considered and evaluations of their effectiveness were based largely
on discussions with facility owner/operators, liner manufacturers, and government
personnel.
Based on the results of these two tasks, EPA developed recommendations for
minimizing the potential damage to the environment as a result of oil leaking from the
nation's AST inventory.
1.4 ORGANIZATION OF REPORT
The remainder of this report is organized as follows:
Chapter 2 provides background information on AST facilities nationwide
and the general characteristics of ASTs, including oil discharges.
Chapter 3 reviews Federal and State AST regulations and industry
practices and standards, and provides estimates of the number of facilities
already using liner systems.
Chapter 4 describes the technical feasibility analysis of alternative liner
system designs, and presents unit costs for facilities to install these liner
systems.
Chapter 5 presents EPA's recommendations.
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In addition, appendices are included that provide supporting documentation for the
various analyses discussed in the report.
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2. BACKGROUND ON ASTs
This chapter provides information on AST facilities and ASTs and describes the
potential environmental problems they pose. Specifically, Section 2.1 presents
information on the number and type of U.S. facilities with ASTs and the general
characteristics of ASTs nationwide. Section 2.2 describes the types of oil discharges from
ASTs and the potential impacts on soil, ground water, and surface water. Section 2.3
presents information on the status of the U.S. AST inventory and the extent to which
which oil discharges may be occurring at these ASTs:
2.1 PROFILE OF AST FACILITIES AND ASTs
EPA reviewed existing Agency reports, State information, and industry studies to
develop a profile of, the number and type of onshore facilities storing oil in bulk, and the
number and type of ASTs. This information was used to:
Analyze the types and characteristics of facilities with ASTs; and
Develop representative facilities, or model facilities, to serve as the basis
' for developing technically feasible pptions for using liner systems with
ASTs, and determining the corresponding facility costs.
This section provides information on the number and type of AST facilities and the
number and general characteristics of ASTs.
2.1.1 Profile of AST Facilities
Section 4113(a) of OPA did not provide EPA with specific direction on the types
of "onshore facilities used for the bulk storage of oil" that should be examined or the
distance that qualifies a facility as being "located near navigable waters." As a result,
EPA adopted a broad interpretation of this statutory language when preparing this report
to avoid underestimating the number of ASTs that potentially benefit from using liners
systems. Specifically, EPA used the storage capacity thresholds of the Oil Pollution
Prevention regulation as the criteria to define the universe of facilities and ASTs that
would be analyzed in the study because: (1) this regulation affects a diverse population
of facilities from many industry sectors; and (2) the Agency previously conducted a study
that provides estimates of the number and type of these facilities. These findings are
discussed below.
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EPA's "Spill Prevention, Control, and Countermeasures Facilities Study" (hereafter
referred to as the Facilities Study)3 provides estimates of the number of facilities that
meet the storage capacity threshold of the Oil Pollution Prevention regulation because
they have: (1) oil storage capacity greater than 42,000 gallons underground; (2)
combined oil storage capacity greater than 1,320 gallons aboyeground; or (3) greater than
660 gallons in a single tank aboveground. Exhibit 2-1 presents estimates of these
facilities by Standard Industrial Classification (SIC) code category and three storage
capacity tiers: 1,320 to 42,000 gallons; 42,001 to 1 million gallons; and greater than 1
million gallons. For purposes of this report, these facility storage capacity categories are
referred to as small, medium, and large, respectively. EPA estimates that there are
approximately 505,000 facilities that meet the storage capacity threshold of the Oil
Pollution Prevention regulation. About 81 percent of these facilities are small, 18
percent are medium, and 1 percent are large.
This 505,000 estimate overstates the number of onshore facilities where AST liners
systems could be installed because approximately 3,000 of these facilities are offshore oil
production platforms that are currently regulated by the Department of the Interior's
Minerals Management Service (MMS). Furthermore, not all of the remaining facilities
are necessarily located near navigable waters. Specifically, EPA estimates that 435,000 of
the 502,000 facilities (505,000 facilities minus. 3,000 offshore production facilities) have
the potential to discharge oil in harmful quantities into or upon the navigable waters of .
the U.S. or adjoining shorelines. Nevertheless, EPA elected to include facilities not
Jocated near navigable waters in this study because many of these facilities have the
potential to contaminate surface water if they discharge oil to soil and ground water,
which could be hydrologically connected to surface water.
As shown in Exhibit 2-1, facilities that meet the storage capacity threshold of the
Oil Pollution Prevention regulation span many SIC code categories, and include facilities
as diverse as farms, manufacturing facilities, and transportation facilities. Despite this
industry diversity, these facilities may be grouped into three broad categories
corresponding to how oil is used at these facilities. Specifically, oil is consumed or used
as a raw material or end-use product (storage/consumption); marketed, refined, and
distributed as a wholesale or retail good (storage/distribution); or pumped from the
ground as part of oil exploration or production activities (production). Facilities in these
three use categories have different characteristics in terms of basic physical and operating
characteristics, such as the number and type of ASTs, throughput, and number and type
of transfer points. For example, farms that use oil and diesel to heat buildings and
power machinery are likely to have fewer ASTs and ancillary equipment and Jess product
turnover than fuel oil dealers and bulk terminal facilities, which distribute petroleum
3 U.S. EPA, Emergency Response Division, "Spill Prevention, Control, and Countermeasures Facilities
Study," January 1991.
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EXHIBIT 2-1
ESTIMATED NUMBER OF FACILITIES MEETING THE SPCC STORAGE CAPACITY THRESHOLDS
*_ -.
Oil Storage Capacity
Facility Category
Farms,
Coal Mintng/Ncmmetallic Minerals
Mining
Oil Production3'
Contract Construction
Manufacturing:
Food and Kindred Products
Chemicals and Allied Products
Petroleum Refining
Stone, Clay, Glass, and Concrete
Primary Metal Industries
Other Manufacturing-'
Railroad Fueling
Bus Transportation
Trucking and Warehousing/
Water Transportation Services
Air Transportation
Pipelines
Electric Utility Plants
Petroleum Bulk Stations
and Terminals
SIC (where
applicable)
01/02
12/14
131 -
15/16/17
20
28
29
32
33
20 - 39
401
41V413/414/417
42/446
458
46
491
5171
1,321 - 42,000
gallons (above
eronnd only)
137,100 - 138,400
2,500 - 4,500
118,000 -233,000
2,000 - 3,600
3,000 - 3,500
3,000 - 5,500
1,000 - 1,200
1,000 - 8,500
1,000 - 2,000
4,000 - 8,000
0
1,200 - 1,600
3,200 - 3,600
0
0-400
3,700
1,400
42,001 - 1,000,000
gallons
neg. - 1,300 '
500 - 900
41,000 - 82,000
500 - 900
600 - 700
600 - 1,100
800 - 900
200 - 1,700
200 - 400
800 - 1,600
100 - 600
300 - 400
800 - 900
500 - 600
neg. - 300
600
8,800
> 1,000,000
gallons
0
neg. - 200
neg.
0
100
neg. - 100
300 - 400
neg. - 100
'' neg. - 400
100
neg.- 100
0
100
neg.
200 - 300
500
2,200
Total
137,100 - 139,700
3,000 - 5,600
159,000 - 315,000
2,500 - 4,500
3,700 - 4,300
3,600 - 6,700
2,100 - 2,500
1,200 - 10,300
1,200 - 2,800
4,900 - 9,700
100 - 700
1,500 - 2,000
4,100 - 4,600
500 - 600
200 - 1,000
4,800
12,400
"Best
Estimate"
138,400
4,300
237,000
3,500
4,000
5,150
2,300--
5,750,
2,000
7,300
400
1,750
4,350
550
600
4,800
12,400
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EXHIBIT 2-1 (continued)
ESTIMATED NUMBER OF FACILITIES MEETING THE SPCC STORAGE CAPACITY THRESHOLDS
Oil Storage Capacity
Facility Category
Gasoline Service Stations
Fuel Oil Dealers
Vehicle Rental
Commercial and Institutional:
Health Cares' "
Education-
Military Installations
Other Commercial and Institutional
TOTAL
"BEST ESTIMATE"
SIC (where
applicable)
554
5983
751
N/A
N/A
N/A
N/A
1,321 - 42,000
gallons (above
ground only)
0
2,500 - 5,500
0
1,700 - 1,900
"4,900 - 5,000
100 - 200
46.600 - 46',800
337,900 - 478,300
. 408,100
42,001 - 1,000,000
gallons
4,200 - 11,100
100 - 2,800
neg. - 300
V
300 - 1,400
100 - 800
300
1,000 - 1,800
62,300 - 122,200
92,250
> 1,000,000
gallons
neg. - 100
neg. - 300
0
neg. --200
' neg. - 100
100 - 200
neg. -200
3,600 - 5,700
4,650
Total
4,200 - 11,200
2,600 - 8,600
neg. - 300
2,000 - 3,500
5,000 - 5,900
500 - 700
47.600 - 48,800
403,800 - 606,200 ,
"Best
Estimate"
7,700
5,600
150
2,750
5,450
600
48.200
505,000
Note: N/A means not applicable and neg. means negligible {i.e., less than 50). The "best estimate" is the midpoint of the range.
*' This includes the 3,000 offshore facilities currently regulated by the Departmept of the Interior's Minerals Management Service (MMS).
- Other industrial manufacturing establishments in SICs 20 through 39, except SICs 20, 28, 29,32, and 33.
- For the medium and large capacity tiers, data were available only for hospitals (SIC 806), which are included in the Health Care subcategory.
- For the medium and large capacity tiers, data were available only for colleges (SIC 822), which are included in the Education subcategory.
Source: U.S. Environmental Protection Agency, "Spill Prevention, Control, and Countermeasures Facilities Study," January 1991.
8
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products to end-users. This characterization is important for developing model facilities,
which provide the basis for developing technically feasible options for installing liners at
these facilities.
The typical storage capacity of these facilities varies significantly, from several
thousand gallons for farms and small industrial manufacturers to tens-of-millions gallons
for petroleum bulk terminals. Similarly, the number of ASTs at these facilities varies
considerably from one or two per facility to over 100 per facility. The model facilities
discussed in Chapter 4 were developed to represent the range in storage capacity and
number of ASTs at these facilities.
x !.
2.1.2 Profile of ASTs
In general, there are two categories of ASTs: vertical ASTs and horizontal ASTs.
The storage capacity of horizontal ASTs typically ranges from a few hundred gallons up
to 20,000 gallons, while the storage capacity of vertical ASTs typically ranges from several
thousand gallons to over 10 million gallons. Vertical ASTs are mounted such that the
tank bottom rests on a ground-level foundation, such as a concrete pad or ring wall.
Small vertical tanks (e.g., less than 42,000 gallons), which are commonly used in the oil
production industry, often are installed on a concrete pad, which, in addition to the tank
bottom, may serve as a secondary barrier to prevent leaked oil from reaching soil and to.
aid in leak detection by channeling oil to the ^ide of the tank where it may be visually
detected.4
/
As the volume and the tank diameter of vertical ASTs increase, ring-wall
foundations become more economical than concrete pads. Ring walls, normally made of
reinforced concrete, provide a foundation or footing upon which the AST wall rests. The
AST bottom plate typically rests on hard-packed soil, sand, or other fill material. Based
on engineering experience, as ASTs reach 40,000 to 50,000 gallons of storage capacity,
the combination of size and weight considerations are such that ring-wall foundations
become more economical than concrete pads.5 Unlike vertical tanks with concrete
pads, leaks from the bottom side of vertical ASTs with ring walls have the-potential to go
undetected for extended periods of time before oil seeps to the edge of the AST, is
detected during ground-water monitoring operations, or creates a sheen in a nearby
stream or river.
Horizontal ASTs typically are supported in saddles that are bolted to secondary
containment structures, such that tank is suspended above the ground or floor of a
4 Concrete pads used with small ASTs often are manufactured with radial groves that aid in leak
detection by channeling discharge oil to the side of the tank.
5 An analysis of data provided by the Entropy Study (see footnote #9) generally confirms this
experience. Specifically, for the oil production sector, approximately 88 percent of all ASTs with a storage
capacity of less than 42,000 gallons are set on concrete pads.
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secondary containment structure. Leaks from horizontal ASTs are generally easy to
detect because facility personnel ca"n readily see the underside of the tank.
The overwhelming majority of existing ASTs are fabricated using carbon steel,
although stainless steel, reinforced concrete, and fiberglass materials also have been used
for certain AST applications. The wall thickness of vertical ASTs may vary significantly,
from 0.1875 inches for a 10,000-gallon AST to 1.135 inches for a 10 million-gallon tank.
Similarly, the thickness of the annular bottom ring of a vertical AST may vary
significantly. The bottom plates of a vertical AST must be constructed with a minimum
thickness of 0.25 inches, exclusive of any corrosion allowance specified by the
purchaser, while the annular ring supporting the bottom-to-shell weld may be as thick as
0.75 inches for the larger ASTs. The thickness of the bottom is a critical factor in
determining the potential for an AST to develop corrosion-related leaks (as discussed in
Section 2.3.3). ASTs are either erected ,at the site (i.e., field erected) or are shop-
fabricated by a manufacturer and then transported to the site. Virtually all ASTs with
v storage capacity greater than 50,000 gallons are field erected because of transportation
constraints and construction considerations. Because the vast majority of ASTs are
constructed with steel materials and, therefore, are susceptible to corrosion, these ASTs
have the potential to leak oil.
EPA estimates that the number of ASTs at the 502,000 onshore facilities that
meet the storage capacity threshold of the Oil Pollution Prevention regulation is about
1.8 million.7'8 Based on the 1989 API "Aboveground Storage .Tank Survey"9
(hereafter referred to as the Entropy Study)) about 700,000 ASTs are used at facilities in
the production, refining, transportation and marketing sectors of the petroleum industry.
These two estimates differ because the number of ASTs at allfacilities that meet the
storage capacity threshold of the Oil Pollution prevention include ASTs outside the
petroleum industry, such as ASTs at end-user facilities (e.g., farms).
6 When specified by'the purchaser, a minimum nominal thickness of 6 millimeters for all bottom
plates is acceptable.
7 U.S. EPA, Emergency Response Division, "Estimate of the Number of Aboveground Storage Tanks
at Onshore Facilities," October 1994.
8 An alternative order-of-magnitude estimate was developed by-multiplying the number of small,
medium, and large facilities that meet the storage capacity threshold of the Oil Pollution Prevention
regulation (presented in Exhibit 2-1) by the number of ASTs typically found at each of these facility size
categories: two ASTs, seven ASTs and 17 ASTs for small, medium, and large facility categories,
respectively. The estimates of the typical number of tanks was developed based on analysis conducted in
support of revisions to the Oil Pollution Prevention regulation. Based on this approach, the number of
ASTs are estimated to be about 1.5 million..
9 American Petroleum Institute, "Aboveground Storage Tank Survey," prepared by Entropy Limited,
April 1989 (hereafter r-ferred to as the Entropy Study).
10
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Exhibits 2r2 and 2-3 present data on the percentage distribution of ASTs by age
and storage capacity, respectively. Exhibit 2-2 presents the distribution of ASTs by age
for 700,000 tanks, which was obtained from the Entropy Study. About 32 percent of these
ASTs are between 0 to 10 years old, while nearly 27 percent of these ASTs are between
11 to 20 years old. AST age may be a critical factor for determining the likelihood that
leaks will develop as a result of corrosion (as discussed in Section 2.3.3).
Exhibit 2-3 shows the estimated distribution of ASTs by storage capacity (gallons)
based on data provided by New York.10 As shown in the exhibit, the largest
proportion of ASTs have a storage capacity of between 1,000 and 10,000 gallons. This
distribution is similar to the distribution of ASTs by storage capacity in the petroleum
industry. Specifically, in Exhibit 2-4, AST distribution by storage capacity based orj the
New York State data is compared to similar data provided by the Entropy Study. As
shown in the exhibit, both sources of data indicate that most ASTs are less than 21,000
gallons. This comparison suggests that the distribution of ASTs within the petroleum
industry by storage capacity is similar to the overall distribution of ASTs by storage
capacity because the New York State data include ASTs from many industry sectors.
2.2 OIL DISCHARGES FROM ASTs
In general, AST oil discharges may be classified into two broad groups/categories:
leaks and spills. These categories are useful for understanding how oil discharged from
ASTs affects the environment and how different types of liner systems could aid in
detecting discharges or preventing oil from contaminating surface water by way of
tributary ground water.
Leaks typically originate from the bottom of vertical ASTs as a result of
perforations in the bottom plates, which are often caused by corrosion. Leaks also may
originate from the sidewalls of vertical ASTs, as well as any point on the surface of a
horizontal AST. However, such leaks can be detected visually as part of a periodic tank
inspection program and, therefore, may be addressed before significant contamination
occurs. Although the amount of oil discharged per hour (or day) from ASTs as a result
of leaks can be relatively small compared to spills (e.g., a leak rate of one gallon per
hour versus a spill of hundreds or thousands of gallons), substantial volumes of oil may
be discharged to soil underneath an AST over time because leaks may continue
undetected for years. Leaked oil is commonly carried through the soil layer by
precipitation and migrates downward to ground water. In addition, leaked oil may
migrate horizontally to the edge of the AST bottom where it can be visually detected.
10 Under New York State's Environmental Conservation Law, both existing and new facilities with a
combined aboveground and underground storage capacity exceeding 1,100 gallons are required to register
with the State in order to operate. Facilities are required to provide general facility information and
detailed tank-specific information, including the storage capacity of ASTs, to the New York State
Department of Environmental Conservation (NYDEC) by filling out an application form. This
information is entered into a computer data base, which is maintained by the NYDEC.
11
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EXHIBIT 2-2
DISTRIBUTION OF ASTS BY AGE CATEGORY
20.0%
7.6%
6.9%
6.8%
32.1%
Age Category
Oto 10 years
11 to 20 years
21-to 30 years
31 to 40 years
41+years
Unknown
26.6%
12
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EXHIBIT 2-3
DISTRIBUTION OF ASTs BY
STORAGE CAPACITY TIER
19.0%
4.1%
2.4%
Storage Capacity Tier (gallons)
15.6%
Less than/Equal to 1,000
1,001 to 10,000
10,001 to 100,000
S3 100,001 to 1,000,000
H Greater than 1,000,000
58.9%
13
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EXHIBIT 2-4
DISTRIBUTION OF ASTs BY STORAGE CAPACITY BY DATA SOURCE
1
SOURCE OF DATA
New York State
API/Entropy Study
AST STORAGE CAPACITY TIER (Gallons)
less than or
equal to 21,000
90.7%
82.8%
21,'Ofll to
42,000
2.1%
. 6.4%
42,001 to
420,000
3.1%
6.0%
420,001 to
4,200,000.
3.6%
.4.2%
greater than
4,200,000
0.5%
0.6%
Spills are episodic events, whereby potentially significant quantities of oil may be
discharged rapidly into secondary containment areas and beyond. Spills from ASTs may
occur as a result of operator error, for example, during loading operations (e.g., vessel or
tank truck - AST transfer operation), or as a result of structural failure (e.g., brittle
fracture) because of inadequate maintenance of the AST. Oil discharged from spills may
fill up secondary containment structures (e.g., diked areas) that surround ASTs and, if
the secondary containment system i$ unlined, migrate through soil and ground water to
surface water. A range of secondary containment liner systems to address the potential
problems posed by oil spilled into secondary containment areas is discussed in Chapter 4.
Oil discharged from ASTs as a result of either spills or leaks has the potential to
contaminate the environment. Oil spills from ASTs may adversely affect soil, ground
water, surface water, ecosystems, and organisms. Spilled oil can move' over the ground or
through the soil and can be carried along by precipitation. Precipitation that falls on the'
land surface enters into a number of different pathways of the hydrdlogic cycle. Sortie of
the water will drain across the land directly into a stream channel, while some will seep
through the soil and become ground water. Ground water flows through the rock and
soil layers of the earth until it too discharges as a spring or as a seepage into a stream,
lake, or ocean. Soil contamination (e.g., oil spilled onto the ground from an AST) may
therefore be carried down into the ground water by precipitation, and this contamination
may then be discharged into surface water. Such a scenario is specifically contemplated
in EPA's underground storage tank (UST) technical requirements at 40 CFR part 280.
Under the UST regulation, a suspected, tank lealc must be reported if released petroleum
is discovered at the site or in the surrounding area (such as the presence of free product
or vapors in soils, basements^ sewer and utility piping, and nearby surface water).
A great deal of research has already been conducted on the effects of oil on the
environment. Spilled and leaked oil can damage farmland and adversely affect water
supplies by polluting wells or water intakes on surface streams. Soil contamination also
may threaten aquatic or terrestrial wildlife and may contribute to pollution in lakes,
rivers, .freshwater wetlands, estuaries, beaches, and ocean waters (where runoff is a major
14
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source of oil pollution). Oil in sewers, pipeline trenches, or foundation fills can increase '
the risk of fire and explosion. In addition, lethal effects of oil on organisms may include
bird mortality caused by oiled feathers, fish mortality, and egg or larval stage losses.
Sublethal effects of AST oil spills on aquatic .organisms could include stress-related
. disease and disruption in behavior patterns or reproduction.
Various technologies are available to remediate oil-contaminated soil, although
use of these technologies can present site-specific difficulties. For example, incineration
has been demonstrated to achieve remediation cleanup goals, but is relatively costly and
may not be acceptable to the public. Surface-enhanced bioremediation, on the other
hand, is not feasible at all sites; the hydrogeology of the site must not allow for rapid
transport of the contaminants to the ground water, and the soil must be compatible with
the introduction of nutrients.
Similarly, there jare various remediation options to handle 'oil-contaminated ground
water. Most of these options are either containment technologies (e.g., slurry walls) or
some variation of the traditional "pump-and-treat" approach. Ground-water pump-and-
treat systems can be very costly, and treatment goals may take 30 years or longer to
achieve. It should also be noted that for certain stratigraphies (e.g., fractured bedrock or
karst topographies), restoration of contaminated aquifers may not be achievable or
feasible with existing technologies.
Exhibit 2-5 highlights three case studies illustrating the problems posed by AST
facilities and concerns regarding the potential for oil to contaminate soil, ground water,
and surface water.
23 STATUS OF ASTs NATIONWIDE
EPA conducted an extensive data collection effort to estimate the number of
leaking ASTs. Specifically, the Agency investigated Federal government data bases, such
as the Emergency Response Notification System (ERNS), and contacted several States
about data on AST leaks. The Agency found that comprehensive data do not exist to
quantify adequately the extent to which the nation's AST inventory is leaking. Existing
Federal regulations require facility owners and operators to report oil discharges that
reach navigable waters and thereby trigger the reporting thresholds of Clean Water Act
(CWA) regulations. Consequently, AST oil discharges that affect only soil and ground
water and that do not initially reach surface water are generally not reported. Despite
these limitations, existing data sources evaluated by EPA suggest that a significant
number of ASTs may be leaking or spilling oil.
Section 2.3.1 discusses EPA's review of Federal reporting requirements related to
oil discharges. Section 2.3.2 describes the available information on the extent to which
ASTs are leaking oil. Section 2.3.3 provides an age profile of the AST universe and
examines the potential relationship between leak probability and tank age.
15
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EXHIBIT 2-5
CASE STUDIES
Case Study #1:
COLDBROOK ENERGY FACILITY
On April 17,1993, about 35,000 gallons of gasoline spilled from a 6-inch crack in.an AST at the
Coldbrook Energy Facility in Hampden, Maine. The tank was surrounded by an unlined
containment dike that contained the spilled material. Remediation measures employed at the
site included recovery wells and trenches dug into the contaminated soil. Response crews also
deployed sorbent boom along the banks of the nearby Penobscot River as a precautionary
measure. Fortunately, only small amounts leached into the river during periods of low tide,
producing a light sheen ("World Spill Briefs," Golub's Oil Pollution Bulletin, Vol. 5 No. 12, May
1993, p. 7).
Case Study #2:
STAR TANK FARM
At the Star Enterprise Inc. tank farm in Fairfax, Virginia, more than 150,000 gallons of oil is
sitting on ground water beneath the Star site arid a neighboring community. The site was first
investigated in September 1990, after migration of the underground plume produced a light
sheen on a nearby creek. Officials at Star Enterprise acknowledge that a missing overflow
container at the loading area of the tank farm could have allowed thousands of gallons of oil to
seep into the soil and ground water undetected;* it is not clear whether this is the only source of
petroleum discharges at the site, and investigations are continuing.
Case Study #3:
SPARKS BULK FUEL TANK FARM
An example of a larger petroleum spill to land affecting soil and, subsequently, ground water
occurred at a bulk fuel tank farm in Sparks, Nevada. In 1989, a 3- to 5-million-gallon
petroleum plume was discovered extending a mile east of the facility into a gravel pit. The oil
from the plume appeared to be seeping through the gravel pit walls and collecting into a water
pool in the bottom of the pit. The gravel company that owned the gravel pit pumped the
solution out of the pit and into containment ponds for treatment. The pumping action drew
the area ground water down tb the pit bottom, diverting it from its natural flow south into the
Truckee River. Regulators said that if the pumping were to stop, the contaminated ground
water would continue downstream and end up in the river.
16
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23.1 Federal Reporting Requirements
The Hazardous Materials Transportation Act (HMTA), as amended, the CWA,
the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA), and the Resource Conservation and Recovery Act (RCRA) all contain
requirements for reporting releases of hazardous materials to the environment under
certain conditions. For oil discharges, however, these reporting requirements are not
inclusive because releases from ASTs to land that do not directly affect surface water or
that are not related to transportation are generally not covered.
The U.S. Department of Transportation (DOT) maintains several systems for
reporting transportation-related hazardous material. Under the HMTA, as amended,
DOT collects information on releases of hazardous materials, including oil products,
during transport by highway, rail, pipeline, water, or air. In some circumstances,
information regarding spills from ASTs may be included in DOT's systems (e.g^ an oil
release from a tank connected to a pipeline). Many AST discharges, however, are not
transportation-related.
The oil discharge regulations promulgated at 40 CFR part 110 and 33 CFR part
153 under the CWA require that an oil discharge to U.S. waters or adjoining shorelines,
or in ocean waters out to approximately 200 miles from the shore, must be reported
immediately to the National Response Center (NRC) if it meets one of the following
three conditions:
^
Causes a sheen to appear on the surface of the water;
* Violates applicable water quality standards; or
Causes a sludge or emulsion to be deposited beneath the surface of the
water or upon the adjoining shorelines.
Traditionally, the CWA reporting requirements have not been interpreted to encompass
oil discharges to soil that reach ground water, but do not migrate to surface water.
In contrast, CERCLA does require that releases of hazardous substances to land
and ground water be reported to the NRC. However, CERCLA's list of regulated
substances excludes petroleum products unless they are specifically listed. In general,
crude oil and refined petroleum products are not listed under CERCLA. Both CWA
discharges and CERCLA releases reported to the NRC or EPA are contained in ERNS.
Finally, the RCRA Subtitle I requirements cover petroleum releases to land, but
only if they originate from an UST system. The Federal UST regulations (at 40 CFR,
part 280) implement Subtitle I. Such underground stdrage systems are broadly defined to
include tanks (together with underground piping) that have a volume that is 10 percent
or more beneath the ground surface. UST owners and operators must report suspected
17
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releases of any volume of petroleum to the environment, as well as spills or overfills that
exceed 25 gallons (or other amount specified by the implementing agency). ASTs would
be covered only if they fit within the UST definition, and release reports would be
maintained by the iniplementing agency (usually a State agency).
Based on these considerations, EPA believes that shortcomings exist with regard
to requirements for the reporting of discharges of oil from ASTs that initially only affect
soil and ground water, and that further action may be warranted to address this issue.
23.2 Discharges from ASTs
EPA analyzed ERNS data to estimate the number of reported oil discharges that
occur from ASTs annually. The ERNS^data base is the Federal government's central
source of data on reported discharges of oil and hazardous substances. The oil spill data
contained in ERNS include information collected primarily from initial release
notifications received by the NRC, U.S. Coast Guard, and EPA. ERNS data indicate
that roughly 30 percent of reported oil discharges from facilities are to secondary
containment areas. This discharged oil could be addressed by liner systems installed
within secondary containment systems.
Of the States that EPA contacted, only Virginia provided detailed information on
oil discharges from AST facilities. The Virginia Department of Environmental Quality
(VADEQ) recently implemented a regulatory program that requires certain AST facilities
to: (1) register all applicable ASTs with VADEQ; (2) satisfy financial responsibility
requirements; (3) submit an Oil Discharge Contingency Plan (ODCP); and (4) participate
in the AST pollution prevention program. In particular, under the ODGP requirements^
facilities with an aggregate oil storage capacity of greater than 1 million gallons must
submit a Ground Water Characterization Study (GCS).11 This study requires facilities
to monitor ground water for signs of oil contamination. Based on GCSs submitted by 88
facilities to VADEQ as of April 4, 1994, about 88 percent of facilities (77 facilities) '
reported ground-water contamination. The data were not- sufficient to determine
whether this contamination is the result of past practices or is continuing to occur at
these facilities.
API conducted a survey in 1994 to determine the extent to which member
facilities in the refining, marketing, and transportation sectors of the petroleum industry
have ground-water contamination. About 300 facilities, or 85 percent, of 350 API
member facilities completed the survey. The results of the survey indicate that 85
11 Virginia Regulation 680-14-12: Facility and AST Registration Requirements, effective September
22.-1993.
12 American Petroleum Institute, "A Survey of API Members' Aboveground Storage Tank Facilities,"
prepared by API Health and Environmental Affairs Department, July 1994.
18
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percent of refineries, 68 percent of marketing facilities, and 10 percent of transportation
facilities have known ground-water contamination near their facilities. Furthermore, the
majority of these facilities are remediating the contaminated ground water. According to
API, the results of this survey may be extrapolated to all API member facilities. Again, it
is not clear from these data whether this contamination is continuing to occur at these
facilities. However, API reports that improved equipment and operating practices over
the last 5 years have reduced reported petroleum spills and accidental releases. These
improvements include:
In 1991, API published standard 653 as guidance for establishing inspection '
intervals for AST bottoms. This standard also "incorporates an AST
inspector certification program that establishes minimum education and
experience qualifications and provides for the testing of candidates."
* Guidance on the development of an overfill prevention program is
provided in API Recommended Practice 2350.
Systems and operating procedures to remove, recover, or properly handle
tank water-bottoms have been or are being implemented at storagb
facilities.
* Survey results indicate the use. of cathodic protection for buried AST-
associated piping has increased. ,
233 Age Profile of ASTs
EPA obtained data on AST age and examined the potential relationship between
AST age and corrosion rates to estimate the likelihood that ASTs will develop leaks as a
function of tank age.
The most comprehensive data currently available on the age of ASTs are provided
by the Entropy Study. This study provides estimates of the number of ASTs by several
age categories for each industry sector. These data are shown in Exhibit 2-6. As shown
in the exhibit, the distribution of ASTs by age category is roughly similar for the
marketing, refining, and transportation sectors, in that the majority of ASTs within each
of these sectors are over 40 years old. However, in the oil production sector, most ASTs ,
are less than or equal to 10 years of age. Because the number of ASTs in the production
sector is significantly greater than the number of ASTs in the other sectors, the overall
age distribution for ASTs in thepetroleum industry is similar to the age distribution for
ASTs in the production sector.1
13 Specifically, the number of tanks in the production, marketing, refining, transportation, sectors is
estimated by the Entropy Study to be 572,620, 88,529, 29,727, and 9,197, respectively, for a total of 700,073.
About 82 percent of all ASTs are in the production sector.
19 . .
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EXHIBIT 2-6
PERCENTAGE OF ASTS BY AGE CATEGORY
50%-i
40%-
30%-
20%-
10%-
Oto 10 years
11 to 20 years
21 to 30 years
31 to 40 years
40+ years
42.1%
325%
Marketing
Source' Entropy Study
Refining Transportation Production.
Total
20
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EPA investigated the potential relationship between the age of ASTs and failure
rates based on data provided in a study conducted by the Suffolk County Department of
Health Services in 1988 entitled, "Final Report, Tank Corrosion Study" (hereafter
referred to as the Suffolk County^Study). During the 1980s, Suffolk County, New York,
enacted legislation that required all unprotected bare steel USTs to be replaced with
protected storage tanks by 1990 whether or not there was evidence that the USTs
were leaking oil. As a result, this program provided a valuable sample of data to
estimate leak probabilities as a function of age because leaking USTs were included in
the sample along with perfectly functional USTs.
, Hundreds of USTs were inspected as part of this program to determine the extent
to which corrosion caused leaks. A relationship between UST tank age and the
probability that USTs will develop a leak caused by corrosion was identified,14
Specifically, the original design wall thickness appears to be a key factor influencing the
amount of time a bare steel tank will remain free of perforations. USTs with thicker
walls normally will take longer to develop a perforation due to corrosion than USTs with
thinner walls, all other factors being equal (e.g., the acidity of the soil). Because the rate
at which tank walls fail due to corrosion is related to tank age, the age of the tank may
be used as an indicator to predict the likelihood that tank walls will develop perforations.
'Exhibit 2-7 presents the percentage of USTs that would fail due to corrosion by age
category, based on estimates from the results of the Suffolk County Study.
In extrapolating the results of the Suffolk County Study to ASTs, EPA modified
some of the assumptions regarding the relationship between the tank age and the
probability of leaks because of the differences between the nominal wall thickness of
USTs and the nominal thickness of AST bottoms. Specifically, ASTs are generally
constructed using thicker bottoms than are USTs walls as a result of structural
considerations and industry standards. Based on these considerations, EPA assumed
that, on average, ASTs fail as a result of corrosion 10 years later than USTs. This 10-
year estimate was based on the added nominal bottom thickness for ASTs as specified in
current industry standards. Exhibit 2-7 presents EPA's estimates of the percentage of
ASTs that fail due to corrosion by age category.
As shown in the exhibit, ASTs less than 10 years old are assumed not to fail as a
result of corrosion. AST failure due to bottom corrosion is generally greatest for tanks
older than 40 years. Specifically, the likelihood of a corrosion-related failure of the tank
bottom for ASTs in this age category is estimated to be about 22 percent.
14 Other factors that may affect the likelihood of corrosion-related tank failure include: (1) acidity of
the soils; (2) height of the water table; and (3) the presence of tank design features such as baffles or
'deflection plates.
21
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EXHIBIT 2-7
PERCENT CORROSION FAILURE IN EACH AGE GROUP
25% n
20% -
15%-
10%-
0 to 10 11 to 20 21 to 30 31 to 40
40+
Source' Entropy Study
AGE CATEGORIES (YEARS)
22
-------
The probability rates for corrosion-related failure of ASTs estimated here do not
consider the effects of using cathodic protection systems to retard ,corrosion of the
bottom plate of vertical ASTs. Specifically, cathodic protection systems have the
potential to reduce the rate at which the bottoms of ASTs corrode if these systems are
properly maintained. EPA did not adjust the probability estimates as a result of cathodic
protection because data on the use of cathodic protection systems with ASTs are
incomplete and cathodic protection is effective only if it is properly maintained.
23
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3. EXISTING REGULATIONS AND INDUSTRY
PRACTICES FOR LINER SYSTEMS
EPA reviewed Federal and State regulations and industry practices to gather
information on the specifications of liner systems and to estimate the number of AST
facilities currently required to use liners. Section 3.1 discusses the results1 of EPA's
review of Federal and State AST regulations. Section 3.2 summarizes recommended
industry practices Telated to AST liners and double bottoms. Section 3.3 presents EPA's
estimate of the number and type of facilities required to use liner systems as a result of
State regulations.
3.1 REVIEW OF FEDERAL AND STATE AST REGULATIONS
3.1.1 Federal Regulations
In general, existing Federal regulations affecting AST facilities do not explicitly
require the use of liners or double bottoms with ASTs. However, section 112.7(c) of the
Oil Pollution. Prevention regulation, which is the primary Federal regulation addressing
oil discharge control and response equipment and procedures for AST facilities, requires
that "appropriate containment and/or diversionary structures or equipment to prevent
discharged oil from reaching a navigable water course should be provided" and that such
containment be "...sufficiently impervjous to contain spilled oil." This regulatory
requirement could be met by constructing a'secondary containment system, such as a
dike, with materials that have a low permeability (i.e., resist the penetration of-oil
through the material) or by adding a liner to the secondary containment system to
provide this protection. However, this requirement does not specify a permeability
standard, such as how far oil may move through the material per unit time (e.g., 1
millionth of a centimeter per second). Although EPA does not have comprehensive data
on the quality of secondary containment structures at AST facilities nationwide,
information provided by EPA field personnel indicates that the quality of secondary
containment systems (e.g., the permeability of the materials) varies considerably.
The Federal UST regulation under RCRA Subtitle I (at 40 CFR part 280) and
the Federal Hazardous Waste Storage Tank (HWST) regulation under RCRA Subtitle C
(at 40 CFR part 264) require that facility owners and operators consider the installation
of liners as a protective option for USTs and HWSTs. Although the Federal UST and
HWST, regulations do not specify liner materials or designs, these regulations establish
performance criteria for containment materials and structures. For example, the UST
regulation mandates a permeability for liners of 1 x 10"6 centimeters per second (cm/sec).
The HWST regulation requires that external liner systems be capable of preventing
lateral and vertical migration of'the waste if a release from the tank(s) should occur.
25
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Leak detection practices or devices are required by the UST and HWST
regulations. The UST regulation specifies that leak detection equipment must be able to
detect a 0.2 galloh-per-hour leak and that tanks must be inspected monthly. The HWST
regulation requires that leak detection systems be in continuous operation and be capable
of detecting a release within 24 hours or at the earliest practicable time.
In general, ASTs (and associated piping) that have less than 10 percent of their
volume below the ground surface are not subject to the Federal UST regulations. The
HWST regulations affect only ASTs that contain hazardous wastes. Thus, Federal
regulations do not require facilities with ASTs containing off to have liner systems within
secondary containment systems. ,
3.1.2 State Regulations
EPA conducted a review of current and proposed AST regulations for the 50
States to gather information on liner requirements and specifications and to determine
quantitatively the extent to which States require facilities to have liner systems. The
results of this review of regulations for each State is briefly summarized in Appendix A.
EPA identified nine States that have promulgated or have proposed regulations
that specify the use of "impermeable" secondary containment systems, liners, or other
diversionary structures -and systems to prevent discharges of oil from reaching soil,
ground water, or surface water: Alaska, Connecticut, Florida, Maryland, New Jersey,
New York, Rhode Island, South Dakota, and Wisconsin.13 For each of these States,
the following information is provided below and summarized in Exhibit 3-1:
* The applicability of the requirements to different sizes and/or types of
. facilities; and
Specifications that address secondary containment (including liner
specifications) and leak detection procedures and/or equipment.
Alaska (18 ACC 75): Alaska requires that all new and existing crude oil storage
facilities with a total storage capacity of more th'an 5,000 barrels (and non-crude facilities
with a storage capacity of more than 10,000 barrels) locate their tanks within a
"sufficiently impermeable" secondary containment area. Secondary containment under
tanks at new installations must include "impermeable" liners or double bottoms. Liner
and permeability specifications apply to new facilities and new secondary containment
areas only:
13 Connecticut's regulations were proposed at the time of this review.
26
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EXHIBIT 3-1
SUMMARY OF STATE REGULATORY REVIEW FOR THE NINE STATES
REGULATION
Alaska
Connecticut
(proposed)
Florida
Maryland
New Jersey
New York
Rhode Island
South Dakota
Wisconsin
SECONDARY
CONTAINMENT
LINERS
J
/
/
/
/
/
/
/
/
UNDERTANK
LINERS
/
N/A
/
N/A
/
S
/
V
s
LINER
MATERIALS
S*
N/A
S
N/A
S
S
S
S
/
PERMEABILITY
RATE (CM/SEC)
1 x lO'7 V
1 x 10'5
1 x 10'7
Ix 10-"
1 x 10'7
Ix 10"6
Ix 10*
Ix KT*
N/A
LEAK
DETECTION
WITH LINERS*7
,/
/
-
-
-
/
-
S
N/A
Notes:
/ Regulations require these specific provisions
N/A Not applicable; these provisions are not part of the regulation
a' States indicated by a "-" require visual detection. States indicated by S also require additional measures
such as inventory control or automatic leak detection equipment -
ฃ' New facilities are required to have a liner "that has a permeability of 1 x 10"7 cm/sec (layer of manufactured
material in the area under the tank) or 1 x 10"6 cm/sec (layer of natural or manufactured material) for new
secondary containment structures, excluding undertank applications
"Sufficiently impermeable" for new installations consists of a "layer of
natural or manufactured material of sufficient thickness, density, and
composition to produce a maximum permeability for the substance being
contained of 1 x 10"6 cm/sec.11
i
"Impermeable" liners for new installations consist of a "layer of
manufactured material of sufficient thickness, density, and composition to
produce a maximum permeability for the substance being contained of 1 x
10'7 cm/sec."
Alaska requires that each tank at new and existing installations must be equipped with a
leak detection system that can be used externally to "detect leaks in the bottom of the
27
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tank, such as secondary catchment under the. tank bottom with a leak detection sump, a
sensitive gauging system, or another leak detection system approved by the department."
The owner or operator must check for the presence of leaks or spills daily at a staffed
facility and at least once a month at an unstaffed facility.
Connecticut (RSCA proposed 22a 449): The proposed regulations would require
facilities with aggregate storage of more than 1,320 gallons, or that have a single tank of
more than 660 gallons,, to have secondary containment in the form of "impermeable...
dikes" around all tanks. These volume specifications are consistent with the Federal Oil
Pollution Prevention regulation. These regulations would apply equally to both new and
existing facilities.
Dike permeability must be less than 1 x 10"5 cm/sec. The dikes may be
either above or below grade, but the depth of a dike may not exceed 10
feet below the outside finished grade. The diked area must contain at least
100 percent of the volume of the largest enclosed tank.
Proposed leak detection specifications, like those for most of the eight other States, will
require regular visual inspections around tanks and transfer piping. Connecticut also
proposes to mandate weekly inventory measurement/record reconciliation procedures to
detect slow leaks that have the potential to escape visual checks.
Florida (FAC 17-762): Florida law specifies "impervious secondary containment"
systems. The regulations apply to all new facilities with a storage capacity of greater than
550 gallons. All existing facilities with a storage capacity of greater than 550 gallons must
comply with the regulations by the year 2000, except for certain shop-fabricated tank
systems. ' . -
* The liner systems may be synthetic, concrete, or clay-based, and they must
be capable of containing 110 percent of the largest tank enclosed by the'
secondary containment area, unless that tank is itself enclosed^in a concrete
vault, or is double walled.
The definition of "impervious" varies depending on the liner material used.
For synthetic systems, ,it is 1 x 10 cm/sec. Concrete liners must only be
"product tight." Clay-based liner systems must be individually approved by
the Florida Department of Envirpnmental Protection.
-14 Vehicular fuel-storing shop-fabricated systems that store or use 1,000 gallons or less per month or
10,000 gallons or less per year also must comply with these regulations by the year 20QO. Other
abbveground shop-fabricated tanks may be retrofitted with double bottoms rather than an undertank
impermeable liner. All alterations must be installed to regulatory specifications by the year 2000.
28
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Specified leak detection measures consist of visual inspections or other appropriate
measures^ Inspections should be conducted around "tanks and integral piping," and must
be conducted at least once per month-
Maryland (CMR 26:12): Maryland law specifies that secondary containment must
be "capable of effectively holding the total volume of the largest storage container
located within the area enclosed by the dike or wall." The regulations apply to new and
existing facilities with a total storage capacity of greater than or equal to 10,000 gallons.
Facilities with a storage capacity of less than 10,000 gallons, if judged to be a reasonable
threat to State waters, also are subject to the regulations. The regulations prohibit the
construction of tanks, dikes, or walls in wetlands or 100-year floodplains, unless a permit
is obtained.
Liner materials are not .specified, nor are any designs except that the
system must consist of continuous dikes or walls.
The permeability of the system must be 1 x 10 cm/sec or less, for an
unspecified liquid. Provisions for storm water collection/release are not
specified.
Maryland requires visual inspections for leak detection. Areas to be included in each
inspection are "seams, rivets, nozzle connections, valves, pumps, and pipelines directly
connected to aboveground storage tanks." Inspections must be conducted at least once
per month. .
New Jersey (NJAC 7 1E-2): New Jersey requires that "any leak must be
prevented from becoming a discharge." The regulations apply to new and existing "major
facilities" - facilities with a storage capacity of greater than or equal to 200,000 gallons.
However, existing facilities are exempt from the secondary containment liner requirement
if the following conditions are met: (1) the containment system (with a containment
volume at least as large'as the largest tank) can protect ground water for the period of
time needed to clean up and repair or stop the leak; (2) the containment system allows
visual inspection for'leaks; and (3) the containment system is inspected daily.
All secondary containment systems must have a permeability of 1 x 10'7
cm/sec or less.
ซ Dikes, berms, walls, curbing, gutters, ponds, lagoons, and basins are all
listed as acceptable secondary containment designs. The system must be
capable of containing 100 percent of the volume of the largest enclosed
tank, plus have a means for accommodating 6 inches of rainwater.
V
Leak detection is required in the form of visual inspections. Areas that must be
protected include the secondary containment areas and systems, storage tanks,
aboveground pipes, and valves. Secondary containment/storage tank areas must be
29
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inspected at least once per week; secondary containment systems that are not
-impermeable (at existing facilities only) must be inspected daily.
New York (6NYCRR612-614): New York requires a "secondary containment.
system" around all ASTs with a storage capacity of greater than or equal to 10,000
gallons; or any tank that could reasonably be expected to discharge oil to the waters of
the State. The regulations for new facilities are more stringent than the regulations for
existing facilities. For example, owners of new facilities with new stationary tanks must:
(1) install double bottoms on tanks; or (2) install an "impervious barrier" underneath the
tanks.
The secondary containment system may consist of a "combination of dikes,
liners, pads, ponds, impoundments, curbs, ditches, sumps, receiving tanks,
and other equipment capable of containing the product stored."
The system must perform such that "spills of petroleum and chemical
components of petroleum will not permeate, drain, infiltrate, or otherwise
escape to the ground waters or surface waters of the State." If the
secondary containment system is constructed of earthen material, a release
may only result in a "minimal amount of soil contamination." For diked
systems, the regulation specifies the use of the performance design
standards in Section 2-2.3..S of the National Fire Protection Association's
Flammable and Combustible Liquids Code (NFPA 30).
Although the volume of the diked area need only be 100 percent of the
largest tank volume (i.e., no precipitation allowance is stipulated), storm
water collection must be controlled with either a manually operated sump
or siphon, or a storm drain with manually controlled valves.
ซ For new facilities, the imperviousness of the double bottom or undertank
barrier must be 1 x 10"6 cm/sec or better.
Visual inspection and inventory records reconciliation are required. The visual
inspections must concentrate on the exterior surfaces (e.g., valves, pipes, etc.) and leak
detection instruments (e.g., gauges or alarms). Visual inspections must be conducted
monthly, and reconciliation of daily inventory records "must be kept current."
Rhode Island (OPCR 10-11): Rhode Island requires that a secondary
containment system be in place around all oil-storing facilities that have a total storage
capacity of greater than 500 gallons. New (or substantially modified) facilities are
15 New York State provides a guidance document for inspectors and facility owners to aid in
understanding the regulations. This document lists some permeability criteria for certain substances, even
though no permeability rates are specified in the regulation.
, 30 - -
-------
regulated more stringently in that their secondary containment systems must consist of an.
"impermeable barrier" underneath all aboveground tanks. Rhode Island's regulations are
similar to New York State's regulations; in many cases, the language is identical.
Secondary containment may consist of a combination of dikes, liners, pads,
impoundments, curbs, ditches, sumps, receiving tanks, or other equipment.
The secondary containment system must be constructed so that petroleum
spills "will not permeate, drain, infiltrate, or otherwise escape to the ground
water or surface water before clean up can occur." Also, if earthen
materials are used for the secondary containment structure, a spill should
only be able to cause "a minimum amount of soil contamination.11
Dike construction must be in accordance with the standards are specified.
by Section 2-2.3.3 of NFPA 30, except that the capacity of the secondary
containment area must be 110 percent of the largest tank volume.
For new or substantially modified facilities, "impermeable" is defined as a
permeability rate for water of 1 x lO"6 cm/sec or less. The barrier must not
degrade in an underground environment or in the presence of oil. In
addition, the entire secondary containment area (not just the undertank
area) for new facilities must be constructed with a permeability rate for
water of 1 x W6 cm/sec or less.
Regular facility inspections are required to detect potential leaks. The inspections must
focus on all exterior surfaces of tanks, pipes, valves, and other equipment such as gauges,
cathodic protection monitoring equipment, or other warning systems. The inspections
must be conducted so that any potentially severe structural imperfections are identified,
such as cracks, excessive settlement, or corrosion. These inspections must be performed
at least monthly. .
South Dakota (SCAC 74:03:30): The regulations are applied differently to new
and existing facilities and to different sized facilities new, large facilities are regulated
the most stringently. "Small" facilities are those that have a total storage capacity of less
than or equal to 250,000 gallons, and "large" facilities are those that have a total storage
capacity of greater than 250,000 gallons.
The containment system for new, "large" facilities may consist of double-
walled and/or double-bottomed tanks, dikes, liners, pads, impoundments,
curbs, ditches, sumps, receiving tanks, or other equipment capable of
holding the material stored. For all containment designs except double-
walled tanks, the containment volume must be 110 percent of the largest
single enclosed tank. For "new" facilities, the containment structures may
be built with native soils, clays, bentonite, or synthetic materials; however,
31
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the permeability of liquid through the finished floors and walls of the
containment structure must be 1 x 10~6 cm/sec or less.
"Small" new and existing facilities must comply with either: (1) the
secondary containment requirements, as described in the bullet aboye; (2)
the release detection requirements, as described below; or (3) certain tank
performance standards, as outlined in the regulation.
"Large" existing facilities must build a containment structure around all
tanks that is capable of storing 110 percent of the volume of the largest
tank. No permeability standard is provided. "Impermeable" barriers
(defined as a permeability of 1 x 10"6 cm/sec or less for an unspecified
liquid) must be built underneath all aboveground piping, and all piping
must be cathodically protected.
"Large" (new and existing) facilities must perform specified leak detection measures;
"small" (new and existing) facilities are provided with options for implementing leak
detection standards, as described above. Facilities are required to use automatic leak
detection equipment, and workers at the facilities also must conduct regular facility
inspections. Monthly reconciliations of inventory records shall be made with daily
measurements of product storage. Inspections of exterior surfaces of tanks, overfill
devices, release detection devices, valves, gauges, and cathodic protection equipment
must be conducted. Automatic detection systems shall be continuously engaged.
Inspections of equipment must be conducted at least twice per calendar year, not to
exceed 15 months between inspections in consecutive years.
Wisconsin (ILHR AR 10): Wisconsin requires lined secondary containment
systems, which must perform as "impervious barriers" to the product stored for all
aboveground, oil-storing tanks with a storage capacity greater than or equal to 110
gallons at new facilities. Existing facilities are given a choice among various
secondary containment options; in addition, existing facilities with a combined storage
capacity of less than or equal to 5,000 gallons are completely exempt.
The term "impervious" is not defined in the regulations, and permeabilities
for the floors and walls of the secondary containment area are not
specified. *
For new facilities, construction guidelines for dikes are specific: "Dike walls
or floors made of earthen or other permeable materials shall be lined with
asphalt, concrete, a synthetic or manufactured liner, or prefabricated basin."
Dike design must be in accordance with Section 2-2.3.3 of NFPA 30, with
the following additions: (1) the volume of the contained area must be 125
16
For farms, this minimum storage tank capacity is increased to 1,100 gallons.
32
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percent of the largest single tank volume, as opposed to 100 percent as
specified by NFPA 30; (2) the walls and floors of the contained area must
be impervious to the material stored; and (3). provisions must be made for
the removal of collected rainwater.
Existing facilities must comply with one or more of the following by May 1,
2001: (1) all of the secondary containment rules as described above, except
that the containment volume may be either (a) 125 percent of the largest
single enclosed tank volume, or (b) 100 percent of the largest single
enclosed tank volume, with provisions for removal of rainwater (with valves
or a sump); (2) leak detection, in the -form of inventory
control/reconciliation, tank-gauging, tightness testing, vapor monitoring, or
some other approved method; (3) installation of a double bottom on tanks;
or (4) lining of the tank interior with a suitable .product (the lining must
cover the tank's bottom and extend a minimum of two feet up from the
exterior grade, along the inside of the tank and the lining must th,en pass a
series of inspections).
Leak detection is not a requirement for new facilities and is contained in the State
regulations only as an option for compliance for existing AST systems.
3.2 INDUSTRY PRACTICES AND STANDARDS
EPA conducted a review of industry practices and standards related to liner
systems to gather additional information on the technical aspects of these systems and
when these systems are recommended,, EPA found that although many industry
associations have developed detailed standards related to the construction and operation
of ASTs, few industry standards or practices explicitly recommend the use of secondary'
containment liners and/or double bottoms. However, at the time this review was being
conducted, several industry associations, including Underwriters Laboratory and the
International Fire Code Institute, were revising their recommended practices related to
ASTs. API and NFPA recently completed their revisions, and the standards relating to
liner systems are briefly summarized below.
In the July 1993 version of the API's Standard 650, "Welded Steel Tanks for Oil
Storage," API adopted a policy recommending the use of release prevention barriers in
new AST construction. API encourages owners or operators planning to construct new
ASTs to consult this document. Double bottoms and undertank liners are both discussed
as possible release prevention options. In addition, API states that if the tank owner
decides the undertank area is to be constructed for leak detection, then the permeability
of the leak detection barrier shall not exceed 1 x 10"7 cm/sec.
NFPA 30, "Flammable and Combustible Liquids Code" (1993 edition) states that
"Facilities shall be provided so that any accidental discharge-will be prevented from
endangering important facilities, or reaching waterways.11 Specifically, NFPA requires
33
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that discharge prevention measures be used with aboveground secondary containment-
type tanks if they meet any of the following criteria: (1) tank capacity is greater than or
equal to 12,000 gallons; (2) piping connections to the tank are below the normal
maximum liquid level; (3) prevention systems for liquid released from the tank by siphon
flow are not provided; (4) means are not provided for determining the level of liquid in
the tank; (5) an alarm (triggered when the liquid in the tank reaches 90 percent of
capacity) is not provided; (6) a system which automatically shuts off delivery when the
liquid level reaches 95 percent of capacity is not provided; (7) spacing between adjacent
tanks is less than 3 feet; (8) the tank is not capable of resisting damage form the impact
of a motor vehicle, or does not have suitable collision barriers in place; or (9) emergency
venting is not provided between any enclosed interstitial space.
EPA's review of industry standards regarding liner systems indicated that these
standards primarily consist of recommended/suggested practices, and not requirements.
EPA does not have information on the number of facilities that have installed liner
systems due to voluntary compliance with these industry standards.
3.3 ESTIMATE OF THE NUMBER OF FACILITIES ALREADY USING LINERS
OR RELATED SYSTEMS
The total number of facilities that could benefit from using liners, presented in
Chapter 2, was adjusted to account for facilities located in States that already require
liner systems. Specifically, facilities in six States currently must use liner systems that are
comparable to liner systems considered in Chapter 4. EPA estimated the number of
facilities in these six States that meet the storage capacity threshold of the Oil Pollution
Prevention regulation and that are required to comply with State liner requirements.
This estimate was developed for each storage capacity tier and by SIC code, and .was
subtracted from the total number of facilities that meet the storage capacity threshold of
the Oil Pollution Prevention regulation to estimate the number of facilities that currently
do not to use liner systems. The results of this analysis are presented in Exhibit 3-2. The
total number of facilities subject to the six States' liner requirements is estimated to be
83,723. This estimate includes approximately H66,000 "small" facilities, 17,000 "medium"
facilities, and 723 'large" facilities. Therefore, the estimated number of facilities not
using liner systems currently is about 421,000.
17 These six states are: Alaska, Florida, New Jersey, New York, Rhode Island, and South Dakota.
34
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EXHIBIT 3-2
ESTIMATED NUMBER OF FACILITIES
NOT CURRENTLY REQUIRED TO INSTALL LINERS
Facility Type
Farms
Coal Mining/Nonmetal Minerals
Oil Production -
Contract Construction
Manufacturing:
Food and Kindred Products
Chemicals and Allied Products
Petroleum Refining
Stone, Clay, Glass, Concrete
Primary Metal Industries
Other Manufacturing
Railroad Fueling ~ .
Bus Transportation
Trucking/Warehousing/Water
Transportation Services
Air Transportation
Pipelines
Electric Utility Plants
Petroleum Bulk Stations and
Terminals ,
Gasoline Service Stations
Fuel Oil Dealers
Vehicle Rental
Commercial and Institutional^
SIC Code
01/02
12/14
131
15/16/17
20
28
29
32
33
20-39
401
411/413/
414/417
42/446
458
46
491
5171
554
5983
751
N/A
Estimated Number Facilities in each of Three Storage
Capacity Tiers
1,321-42,000
gallons
121,261
3,084
138,950 '
2,670
2,682
3,526'
893
3,932
1,215
4,795
0
1,079 ,,
2,870
0
183
3,339
1,217
0
3,154
0
, 47,183
TOTAL 1 342,033
42,001-1 mill.
gallons
572
616
49,743
668
537
668
690
785
244
959
350
269
717
458
136
-542
7,547
5,967
1,031
119
2,635
75,253
> 1 million
gallons
0
87
0
0
82
38
273
40
155
76
50
0
82
0
227
441
1,887
39
107
0
343
3,927
Totals
121,833
3,787
188,693
3,338
3,301
4,232
1,856
4,757
1,614
5,830
400
1,348
3,669
458
546 '
4,322
10,651
6,006
4,292
119
50,161
421,213
^Includes military installations, health care, education, and other commercial and institutional facilities.
35
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4. TECHNICAL FEASIBILITY AND UNIT COST OF
LINERS AND RELATED SYSTEMS
4.1 OVERVIEW
This chapter presents EPA's evaluation of the technical feasibility of alternative
liner systems and estimates of the unit costs to install secondary containment liners and
tank double bottoms. EPA investigated the technical feasibility of liner systems by
examining the effectiveness of different liner materials and designs for protecting the
environment from oil discharges and evaluating the construction feasibility of liner
systems. The technical feasibility and unit-cost analysis is based on alternative liner
designs for six "model" facilities used to represent the diverse universe of facilities
potentially benefitting from the installation of secondary containment liners and double
bottoms. The alternative designs examined in this analysis and evaluations of their
effectiveness were based largely on discussions with EPA On-Scene Coordinators (OSCs)
and owners and operators of facilities using, handling, and storing oil and petroleum
products.
The characteristics of the model facilities also were used to develop unit-cost
estimates. The estimated costs of installing liners at new facilities and retrofitting liner
systems to existing facilities were based on material, installation, and engineering cost
information provided by liner manufacturers and installers, and are presented in this
chapter in terms of dollars-per-gallon of storage capacity.
The remainder of this chapter is organized as follows. Section 4.2 discusses the six
model facilities used to represent AST facilities that currently do not use liners. Section
4.3 presents an overview of liner materials, costs, and effectiveness; current liner
practices; and the conceptual designs for the liner systems analyzed in this study.
Evaluation of these designs is presented in Section 4.4. Section 4.5 addresses the use of
leak detection methods at ASTs.
4.2 DESCRIPTION OF MODEL FACILITIES
The technical feasibility and estimated cost of liner systems were based on the
characteristics of six "model" facilities intended to represent the universe of facilities
potentially benefiting from the use of liners.18 The "model facility" approach was
selected because the technical feasibility and cost to install and maintain liner systems
varies significantly depending on the specific characteristics of a facility (e.g., the number,
18 The estimated number of facilities not currently using liner systems, is presented in Chapter 3.
37
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size, type, and arrangement of tanks). The model facility approach also is necessary
because the diverse nature of facilities potentially benefitting from liners precludes
developing facility characteristics for each of the 16 industrial categories of facilities with
ASTs. Development of the six model facilities, shown in Exhibits 4-1 through 4-6,
reflects information previously collected about facilities storing, handling, and using oil.
The six model facilities and their principal characteristics that affect liner
installation costs are described below. All of the model facilities are assurned to have ,
secondary containment dikes around their tanks although other forms of secondary
containment, such as directed drainage to collection ponds or sumps, also are possible.
Model Facility 1: Small End User - Heating Oil Supply (Exhibit 4-1) consists of a
one horizontal 2,000-gallon heating oil tank used to supply fuel to a boiler or
furnace for industrial or commercial purposes (e.g., school, hospital, or small
manufacturer).19 The tanks are filled by fuel delivery trucks, and the oil is used
on site.
Model Facility 2: Small End User - Motor Fuel Storage (Exhibit 4-2) is a motor
fueling operation with a total storage capacity of 24,000 gallons (in three 8,000-
gallon horizontal tanks). The tanks are filled by fuel delivery trucks and unloaded
to motor vehicles.
Model Facility 3: Type 1 Bulk Storage - Distribution (Exhibit 4-3) is a small bulk
plant with a combined storage capacity of 45,000 gallons in three 15,000-gallon
shop-fabricated, vertical tanks storing motor fuel and possibly heating oil.
Fuel delivery trucks are loaded and unloaded from a loading rack at the facility.
. Model Facility 4: Type 2 Bulk Storage - Distribution (Exhibit 4-4) has a -
combined storage capacity of 104,000 gallons in six horizontal tanks (three of
10,000-gallon capacity and three of 8,000-gallon capacity) and two shop-fabricated,
vertical tanks (each of 25,OOOTgallon capacity). It also has a loading rack area.
19 Horizontal tanks are cylindrically shaped tanks positioned so that the long axis of the tank is
parallel to the ground. Because of this orientation, horizontal tanks are usually supported off the ground
by concrete or metal "saddles" conformed to the rounded tank bottom. Horizontal tanks are typically less
than 42,000 gallons and are shop-fabricated (i.e., assembled entirely at the place of manufacture).
20 Vertical tanks are cylindrically shaped tanks whose main axis is perpendicular to the ground.
Vertical tanks typically range in size from less than several hundred gallons to over 1 million gallons.
Vertical'tanks may be shop-fabricated if small, or field-erected (i.e., assembled on-site).
38
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EXHIBIT 4-1
MODEL FACILITY 1$ SMALL END USER - SUPPLY
. 39
-------
EXHIBIT 4-2
MODEL FACILITY 2: SMALL END USER - STORAGE/MOTOR FUEL
40
-------
EXHIBIT 4-3
MODEL FACILITY 3: SMALL BULK STORAGE - DISTRIBUTION
41
-------
EXHIBIT 4-4
MODEL FACILITY 4: MEDIUM BULK STORAGE - DISTRIBUTION
42
-------
EXHIBIT 4-5
MODEL FACILITY 5: LARGE BULK STORAGE - DISTRIBUTION
43
-------
. EXHIBIT 4-6
MODEL FACILITY 6: LARGE OIL TERMINAL - DISTRIBUTION
44
-------
Model Facility Si Type 3 Bulk Storage - Distribution (Exhibit 4-5) has a total
storage capacity of 325,000 gallons, including three 25,000-gallon shop-fabricated,
vertical tanks and a 250,000-gallon field-erected vertical tank located on a ring-
wall foundation. Loading rack areas for loading and unloading are also present at
this type of facility.
Model Facility 6: Large Oil Terminal - Distribution (Exhibit 4-6) has a mixture
of nine large-diameter, field-erected, vertical tanks with a combined storage
capacity of 50.5 million gallons. The tanks consist of: four 10-million-gallon tanks
(200-foot diameter); three 3-million-gallon tanks (120-foot diameter); and two
750,000-gallon tanks (80-foot diameter). Product is transferred to the tanks from
barges and/or tankers at off-loading piers and loaded into distribution trucks at
loading racks.
The characteristics of the six model facilities are summarized in Exhibit 4-7.
EXHIBIT 4-7
SUMMARY OF CHARACTERISTICS OF MODEL FACILITIES
Total Capacity
(gallons)
No. of Tanks
Facility Type
Size
MODEL 1
2,000,
1 .
End user
Small
MODEL 2
24,000 .
3
End user
Small
MODEL 3
45,000
3
Distribution
Medium
MODEL 4
104,000
8'
Distribution
Medium
MODEL 5
325,000
4
Distribution
Medium
MODEL 6
50,500,000
9
Distribution
Large
Note: Facility size categories are defined as small being 1,321 to 42,000 gallons; medium being 42,001 to 1
million gallons; and large being greater than 1 million gallons.
EPA then estimated the number of AST facilities represented by each model
facility. For this report, EPA categorized by "size"-and "use" the types of facilities in the
16 industrial sectors identified in Chapter 3 as not currently required to install liners
(presented in Exhibit 3-2). The "size" categories are small, medium, or large, and the
"use" categories (based on how the oil or petroleum products are used at facilities in that
industrial sector) are:
Production, which includes all facilities in SIC code 131 (Oil Production);
Storage/Distribution, which includes all facilities in SIC code 46 (Pipelines),
SIC code 5171 (Petroleum Bulk Stations/ Terminals), SIC code 554
(Gasoline Service Stations), and SIC code 5983 (Fuel Oil Dealers); and
45
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* Storage/Consumption, which includes facilities in all other industrial
sectors.21
Exhibit 4-8 shows the results of this categorization by size and use; for example, 138,950
AST facilities are small production facilities (i.e., have a total storage capacity of between
1,320 and 42,000 gallons).
Next, one or more of the model facilities developed for this report was assigned to
represent all facilities in each size and use category (e.g., small storage/distribution
facilities). This assignment was based on previous analyses conducted by EPA (described
in Appendix B) which developed typical storage capacities for facilities in each size and
use category. For example, a typical small storage/consumption facility is estimated to
have a storage capacity of approximately 2,000 gallons, which is the same as the assumed
storage capacity of Model Facility 1. Consequently, all 198,529 small storage/
consumption facilities that currently are not required to have liners are represented by
Model Facility 1. The results of assigning facilities to the model facilities developed for
this report also are presented in Exhibit 4-8.
Several of this report's model facilities represent facilities from more than one size
and use category. In addition, because the size categories are broad, certain size and use
categories are best represented by more than one model facility. In these cases, the
difference between the typical storage capacity of the facilities in that size and use
category and the storage capacity of the model facilities in this analysis provided the basis
for allocating among two model facilities.22 For example, small storage/distribution
facilities are estimated to typically have a total storage capacity of approximately 10,000
gallons (see Appendix B for a detailed description), for which no single model facility in
this report corresponds closely. Therefore, small storage/distribution facilities are best
represented by a mix of Model Facilities 1 and 2, which are assumed to have 2,000 and
24,000 gallons of storage capacity, respectively. As the "typical" small storage/distribution
facility (10,000 gallons) is closer in storage capacity to that of Model Facility 1 (2,000 .
gallons) than Model Facility 2 (24,000 gallons), a larger percentage of facilities were
allocated to Model Facility 1. Of the estimated 4,554 small storage/distribution facilities,
2,898 facilities are estimated to be best represented by Model Facility 1, -and the
remaining 1,656 facilities are estimated to be best represented by Model Facility 2.
21 These size and use categories were originally developed by EPA for use in estimating the costs of
implementing the requirements of the Oil Pollution Act of 1990 (U.S. EPA, Emergency Response
Division, "Regulatory Impact Analysis of Revisions to the Oil Pollution Prevention Regulation (40 CFR
112) to Implement the Facility Response Planning Requirements of the Oil Pollution Act of 1990", June
1994). See Appendix B of this report for additional information comparing that analysis to the estimates
presented here.
22 An alternative allocation formula was used for medium storage/distribution facilities, as described in
Appendix B.
46 , .
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EXHIBIT 4-8
CATEGORIZATION OF FACILITIES NOT CURRENTLY REQUIRED TO INSTALL LINERS
FACILITY SIZE
AND USE
CATEGORY
Small
Medium
Large
Total
PRODUCTION
138,950 facilities
Model Facilities 2 and 3
49,743 facilities
Model Facility 4
Negligible
Not Applicable
188,693
STORAGE/
DISTRIBUTION
4,554 facilities
Model Facilities 1 and 2
14,681 facilities
Model Facilities 3 and 5
2,221 facilities
Model Facility 6
21,456
STORAGE/
CONSUMPTION
198,529 facilities
Model Facility 1
10,829 facilities
Model Facilities 4 and 5
1,706 facilities
Model Facility 6
211,064
TOTAL
342,033
75,253
3,927
421,213
Note: Size categories are defined as small being 1,321 to 42,000 gallons; medium being 42,001 to 1 million gallons; and large
being greater than-1 million gallons. " .
47
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The estimated total number of facilities represented by each model facility is as
follows:
- Model Facility 1: 201,427
Model Facility 2: 49,296
Model Facility 3: 97,277
Model Facility 4: 55,623
Model Facility 5: 13,663
Model Facility 6: 3.927
Total # Facilities 421,213
43 LINER SYSTEM DESIGNS AND PRACTICES
Liners are engineered systems that enhance the imperviousness of secondary
containment structures that surround ASTs.23 Secondary containment structures vary
greatly depending on the size of. the tanks and the physical characteristics of the facility
and may be constructed of compacted native soil (e.g.; clay), concrete, or other synthetic
material. Secondary containment structures are typically designed to hold the entire
contents of the tank or tank battery within the structure and serve to contain any spilled
oil or product in the event of a leak or sudden discharge. Liners may be installed within
secondary containment structures in several ways. Liners may be placed to cover the
entire interior area of a secondary containment system, including the area beneath any
tanks (i.e., undertank liners). Alternatively, especially for facilities with existing vertical
tanks in direct contact with the ground, liners may be installed throughout the interior
area of the secondary containment except underneath existing vertical tanks. Although it
is technically feasible to move an existing AST temporarily in order to install an
undertank liner beneath its normal resting area, it is usually considerably more expensive
than installing a double bottom, which serves the same purpose of protecting against
leaks from failing tank bottoms. '' _
Double bottoms protect against leaking or failing tank bottoms in vertical tanks.
When in direct contact with the ground, the tank bottom is susceptible to corrosion
(rusting of the metal), which eventually reduces the thickness of the tank bottom,
resulting in the development of perforations (e.g., pinpoint holes) and, if left unrepaired,
rips and tears. In contrast, horizontally mounted tanks are smaller and are much less
susceptible to corrosion because they are typically supported off the ground by concrete
or metal saddles or other platforms. Double-bottom tanks have a second steel surface
above the outer tank bottom or tank foundation to provide additional protection against
23 Secondary containment is a general term that includes all structures designed to channel and contain
a spill or leak from an AST or storage facility. Secondary containment structures may include graded
surfaces leading to a collections pond, diked or bermed areas around tanks, or sumps.
24 Some of these materials''also may be used as liners to secondary containment structures made of
more permeable materials.
48
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leaks in the event of corrosion-induced failure of the bottom surface. Generally, the
interstitial space between the two steel bottoms of the tank includes a geos'ynthetic liner
and a leak detection system. Although, the choice of a second steel bottom may provide
additional opportunity for corrosion, the interstitial leak detection system would alert the
.facility operator to any failure of the system, and the geosynthetic liner would prevent oil
from discharging to the environment until repairs could be made. The space around the
interstitial liner and leak detection system also is filled with concrete or sand to provide
additional structural support to the inner tank bottom. For purposes of this report, EPA
analyzed double bottoms as "other means of secondary containment," which could be
used in place of undertank liners.
EPA analyzed other alternatives to double bottoms, but did not find these options
to be as usable as double bottoms. For example, one of the options considered was the
use of electronic fluid flow indicators in horizontal wells placed beneath ASTs to detect
leaking petroleum products. Although this technology is relatively inexpensive, it detects
a leak only after oil has contaminated the underlying soil. For purposes of this study,
double bottoms are preferred over this option because double bottoms would aid in
detecting a leak before soil contamination could occur.
Another option considered was the installation of a geomembrane liner along the
inside walls and bottom of an AST. .Although this option is not a form of leak detection,
it is a viable method for preventing oil from leaking intq the underlying soil provided that
the product stored in the AST is compatible with the liner material. If it is not,
degradation of the liner could occur. The use of double bottoms, however, would
provide greater flexibility in the type of product that could be stored in the AST.
To gather information on current industry practice relating to liners, EPA
surveyed OSCs (EPA technical staff directly implementing the current SPCC Program),
facility owners and operators, liner manufacturers and installers, and State officials
responsible for AST regulatory programs.25 These interviews were meant to provide a
general assessment of the advantages and disadvantages of various liner designs and
materials from a broad representation of knowledgeable sources. The interviews were
intended to gather background information rather than be a rigorous, scientifically valid
survey. The following section summarizes the information obtained from the interviews
on five topics: the types of liner materials in use, the costs of using liners, liner use
practices, opinions on liner effectiveness, and leak detection practices.
25 OSCs from each of the 10 EPA Regions, 13 facility owners/operators in 10 States, 15 liner
manufacturers, 7 installers, 2 manufacturers of spray-on coatings, and State environmental agency staff in
all 50 States were contacted. Three representatives of the insurance industry were also contacted regarding
the availability of data oh the probabilities and. sizes of discharges from ASTs. However, these insurance
industry contacts were not able to provide any new information beyond that already identified from other
sources. '
49
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43.1 Liner Materials Currently in Use
Impervious soils26 (clay, soil-bentonite mixtures), concrete, bituminous concrete,
geomembranes (polymeric sheets and bentonite mats), and steel 'liner systems are all
used by industry. Spray-on liner systems also are available and tend to be used in
conjunction with concrete secondary containment structures, although some
manufacturers have developed spray-on systems that work with earthen berms (the
material adheres to and seals the surface of the dike wall or berm, preventing product
from permeating through cracks or other imperfections).
Facility owners and operators reported that most secondary containment
structures are made from earthen materials. Five out of 13 facility owners/operator
respondents further indicated that impervious soil was the preferred-liner material. In
contrast, manufacturers and installers reported that synthetics were the most common
materials used for secondary containment liners. The synthetic materials most often cited
by the manufacturer and installer respondents were high density polyethylene (HDPE),
polyvinyl chloride (PVC), XR-5ฎ, Hypalonฎ, and Hytrelฎ.
43.2 Cost ซf Liners
Opinions varied on the cost to install, operate, and maintain liner systems.
Several owners and operators mentioned that, in their experience, maintaining
geomembrane systems is expensive. However, several liner manufacturers asserted that
geomembrane liner systems have low operation and maintenance (O&M) costs following
the initial installation; most of the liner manufacturers and installers interviewed
suggested that the only routine maintenance necessary is a periodic inspection, and repair
if damage is found.
Installed liner cost quotes from different companies varied significantly, even for
identical liner materials. In addition, recommended liner thicknesses also varied
significantly for identical liner materials and applications.
433 Liner Use Practices
In general, liners are not consistently used throughout the industry. Five of the
13 owners/operators-who were contacted said that liners were not used at their facilities.
Four facilities had incorporated liners into new designs and on some retrofitted tanks and
secondary containment structures. OSCs and owners^operators agreed that liner systems
are used primarily at large facilities (i.e., with total storage capacity greater than 1 million
gallons) and that small facilities (i.e., less than 42,000 gallons) usually use liners only
when mandated by State regulations.
26 For purposes of this report, the term "impervious soil" means a naturally occurring or adapted soil
that has a hydraulic conductivity of 1 x 10"6 cm/s or less.
50
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The liner-manufacturer and installer respondents stated that, while some existing
facilities are being retrofitted with new tank bottoms (double bottoms) and liners in
secondary containment areas, it is mostly new facilities that are protected with these
systems. Most respondents agreed that, in general, few existing facilities appear to be
retrofitted with liner systems, except in the States that mandate liners.
i
State regulation of ASTs, including the required use of liners, varies. Twenty-
seven States have adopted, in varying degrees, the National Fire Protection Association
(NFPA) standards or other fire codes related to ASTs. Fifteen States have specific AST
requirements in their regulations; seven States require liners at AST facilities. Of the
seven States that require liners, six specify maximuni permeability liners. Two additional
States are-proposing liner regulations with specific permeability requirements. Four
States specify that AST facilities must adhere to the Oil Pollution Prevention regulation,
while another four States delegate the regulation of ASTs to local agencies. Four States
that currently do not regulate ASTs have proposed or will be proposing AST regulations.
4.3.4 Liner Effectiveness
Liner manufacturers and installers report that the design life of a liner is between
15 and 30 years, except for spray-on liners whose design life is between 8 and 15 years.
These numbers are conservative estimates of the life span of a liner based on the
manufacturer's warranty, which is derived from accelerated tests performed to evaluate .
liner effectiveness and longevity.
Although OSCs have limited experience with liners, those interviewed agree that
with proper installation and maintenance, liners are effective in preventing ground-water
contamination and in detecting leaks from AST bottoms.28 However, facility
owner/operator respondents stated that liner maintenance is not always a high priority,
and poor maintenance can significantly reduce the effectiveness of certain types of liners.
Each type of liner has different requirements with regard to proper maintenance
and repairs, as briefly described below.
Impervious Soil. Some silty clay liners require constant or periodic
hydration using a sprinkler or irrigation system. Facilities also sometimes
apply controls to prevent liner penetration from animal activity or
undesirable vegetation, and regularly inspect the liner for damage from
heavy precipitation, erosion, and settling. If the original soil liner is
damaged, it may need to be completely replaced.
27 See Chapter 3 for a discussion of State regulations and industry practices related to liner systems.
28 OSCs also noted that most spills occur outside of the tank secondary containment areas, such as at
loading racks during product transfer operations. Such spills would not be addressed by liners in tank
secondary containment areas.
51
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Coated or Uncoated Concrete. Some concrete liners may require
evaluation of the expansion/contraction joints. Such an evaluation could
include periodically confirming wall-to-floor integrity, and checking for
cracking. Facilities also typically evaluate the integrity of concrete coatings.
ซ Geomembranes. Routine maintenance of geomembrane liners typically
includes visual inspection of lindr integrity and, in some cases, testing of the
seams. Facilities may also use controls to prevent liner penetration from
animals or vegetation.
43.5 Liner Designs Used in this Study . . ''
' /
For this study, EPA developed representative liner system designs that could be
used at the six model facilities as a basis to evaluate liner system technical feasibility and
installation costs. To provide a visual description of how different types of liner system
designs can be applied at a facility, Exhibit 4-9 shows a general schematic of a generic
AST facility, consisting of a single, large, vertically-mounted AST; a smaller, horizontally
mounted AST; an aboveground piping system; and a lined, diked containment area with
an access road within it.
, Exhibit 4-9 also indicates the areas of the generic facility that are presented in
detail in Exhibits 4-10 through 4-14, as described below. Some designs may be more
suitable than others for various liner applications.
- Exhibit 4-10 presents cross-section details of liner installations in a
containment area using four alternative types of liner materials: an
impervious soil liner, a concrete liner, a geomembrane liner, and a
bentonite mat liner. Although the designs depicted are typical examples,
various designs and installation methods exist for these liner materials.
* Exhibit 4-11 shows details of the liner system at the interface of the vertical
tank (i.e., where the tank base meets the liner material) for the same four
liner materials as shown in Exhibit 4-10. These drawings shpw that liner
systems do not protect against discharges from tank bottoms.
* Exhibit 4-12 details methods for securing liners to tank foundations and
foundations for above-ground piping supports that penetrate the floor of
the secondary containment area.
Exhibit 4-13 presents designs for installing liners where access roads are
entirely within the secondary containment area.
52
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EXHIBIT 4-9
GENERAL SCHEMATIC: ABOVEGROUND STORAGE FACILITY
FOUNDATION PENETRATIONS
(EXHIBIT 4-11)-
FIORIZONTAL
AST
VERTICAL
AST
UNDERTANK CONTAINMENT AND LEAK
DETECTION SYSTEMS (EXHIBIT 4-13)
LINER AT BASE OF
VERTICAL TANK
(EXHIBIT 4-10)
ACCESS ROAD
-(EXHIBIT 4-12)
CONTAINMENT DIKE
AND LINER
(EXHIBIT 4-9)
NOT TO SCALE
53
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EXHIBIT 4-10
DETAILS: CONTAINMENT DIKE AND LINER
VEGETATED OR GRANULAR
- SOIL COVER - 6 INCHES
IMPERVIOUS SOIL
LINER-6 INCHES
A. IMPERVIOUS SOIL LINER
REINFORCEMENT
MESH
EXPANSION
JOINT WITH
SEALANT
REINFORCEMENT BAR
EXPANSION JOINT WITH SEALANT
CONCRETE FLOOH 4 MCHEB
REINFORCEMENT I
OPTIONS
CONCRETE
LINER-4 INCHES
B. CONCRETE LINER
ANCHOR TRENCH USE BACKFILL AND
DEADMAN (OPTIONAL)
GEOMEMBRANE LINER
GEOFABRIC
ANCHOR TRENCH USE BACKFILL AND
DEADMAN (OPTIONAL)
VEGETATED OR GRANULAR
SOIL COVER-6 INCHES-
BENTONITE MAT LINER
SAND BASE -6 INCHES (2 INCHES FOR SPRAY-ON LINER)
C. GEOMEMBRANE LINER
SAND BASE -8 INCHES
D. BENTONITE MAT LINER
NOT TO SCALE
54
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EXHIBIT 4-11
DETAILS: LINER AT BASE OF VERTICAL TANK
VERTICAL
TANK BOTTOM
VEGETATED OR GRANULAR
SOIL COVER -6 INCHES
RING WALL
FOUNDATION
IMPERVIOUS SOIL
LINER-6 INCHES
A. IMPERVIOUS SOIL LINER
VERTICAL
TANK BOTTOM
SEALANT
EXPANSION JOINT
RING WALL
FOUNDATION
CONCRETE LINER
4- 4 INCHES
REINFORCEMENT
MESH
B. CONCRETE LINER
OPTION A
VERTICAL
TANK BOTTOM
BATTEN STRIP WITH
ANCHOR BOLTS
GEOMEMBRANE LINER
GASKET ,
VERTICAL
TANK BOTTOM
SEALANT
VEGETATED OR GRANULAR
SOIL COVER-6 INCHES
RING WALL
FOUNDATION
OPTIONS
OEOMEMiHANEUNEfl
LINER CEMENT
RING WALL
FOUNDATION
BENTONITE
MAT LINER
BENTONITE SEAL
C. GEOMEMBRANE LINER
D. BENTONITE MAT LINER
NOT TO SCALE
55
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EXHIBIT 4-12
DETAILS: FOUNDATION PENETRATION
FOUNDATION
PENETRATION
IMPERVIOUS
SOIL LINER
6 INCHES
VEGETATED OR GRANULAR
SOIL COVER-6 INCHES
A. IMPERVIOUS SOIL LINER
EXPANSION JOINT
WITH SEALANT
REINFORCEMENT
MESH
FOUNDATION
PENETRATION
CONCRETE LINER-
4 INCHES
B. CONCRETE LINER
GASKET
GEOMEMBRANE
LINER
FOUNDATION
PENETRATION
BATTEN STRIP WITH
/ ANCHOR BOLTS
rJf VEGETATED OR GRANULAR
JJ I SOIL COVER - 6 INCHES
BENTONITE MAT WRAPPED
AROUND FOUNDATION
VEGETATED OR GRANULAR
SOIL COVER-6 INCHES
Lry wii
FOUNDATION
PENETRATION
BENTONITE
SEAL
BENTONITE
MAT
LINER
C. GEOMEMBRANE LINER
D. BENTONITE MAT LINER
NOT TO SCALE
56
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EXHIBIT 4-13
DETAILS: ACCESS ROAD
GRANULAR ROAD BED
GEOGRID
IMPERVIOUS SOIL OR BENTONITE MAT LINER
A. IMPERVIOUS SOIL OR BENTONITE MAT LINER
VEGETATED OR GRANULAR
SOIL COVER - 6 INCHES
8* CONCRETE ROADBED
t
B. CONCRETE LINER
GEOGRID
SAND BASE -6 INCHES
C. GEOMEMBRANE LINER
GEOMEMBRANE LINER
NOT TO SCALE
57
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EXHIBIT 4-14
DETAILS: UNDERTANK CONTAINMENT SYSTEM
VERTICAL
I-TANK
BATTEN
UNER LOCK EMBEDDED
-INTO CONCRETE
TANK BOTTOM
SAND BACKFILL
ANODE GRID
OEOMEMBRANE LINER
-RING WALL FOUNDATION
LEAK DETECTION PIPE
A. GEOMEMBRANE UNER (NEW)
'VERTICAL TANK WALL
-NEW TANK BOTTOM
GASKET
SAND BACKFILL
ANODE GRID
GEOMEMBRANE
LINER
EXISTING TANK BOTTOM
BATTEN STRIP WITH
ANCHOR BOLTS
RING WALL FOUNDATION
LEAK DETECTION PIPE
B. GEOMEMBRANE LINER (RETROFIT)
VERTICAL TANK WALL
LEAK DETECTION
CHANNEL CUT INTO CONCRETE
REINFORCEMENT BAR
H- EXISTING
TANK BOTTOM
REINFORCED CONCRETE
FOUNDATION PAD
C. CONCRETE LINER (NEW)
LEAK DETECTION
CHANNEL CUT INTO
. CONCRETE
GASKET
GEOMEMBRANE
UNER
(OPTIONAL)
RING WALL
FOUNDATION
ft- VERTICAL TANK BOTTOM
NEW TANK BOTTOM
CONCRETE
EXISTING
TANK BOTTOM
BATTEN STRIP WITH
ANCHOR BOLTS
D. CONCRETE LINER (RETROFIT)
NOT TO SCALE
58
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* Exhibit 4-14 presents four possible designs for addressing leaks from tank
bottoms of vertical ASTs, which may not be controlled by a secondary
containment liner system. Two designs are for undertank liner systems
installed with new tanks, while the other two are for retrofitting existing
tanks with double bottoms and leak detection systems.
i
4.4 LINER FEASIBILITY EVALUATION
EPA assessed the technical feasibility of liner systems based on the degree of
environmental protection afforded, ease of construction, and cost, as described below.30
Environmental Protection. Environmental protection, constitutes protecting
ground water, aiding in leak detection, and preventing oil spills from
reaching -surface waters. The degree of environmental protection provided
by a liner system depends on its permeability, which is influenced by among
other factors: workmanship in installation; quality and regularity of
upkeep; chemical resistivity; resistance to weathering Caused by ultraviolet
exposure, freeze/thaw cycles, erosion, and wet/dry cycles; and resistance to
other damage caused by vandalism, animal activity, and undesirable
vegetation.
Ease of Construction. Factors that complicate construction include
constrained site conditions, adverse climatic conditions, material availability,
and the skill of the installers.
Cost. Cost includes capital costs for materials and installation, annual
operating costs (e.g., animal and vegetation control, security, and' hydration
of clay-based material) and maintenance costs, such as liner system repairs.
Exhibit 4-15 summarizes the feasibility of using liners at oil-storing AST facilities
for environmental protection and shows the constructibility of liner systems. Liner
systems are rated relative to each other on a scale from 1 to 5, where 1 is distinctively
inferior to other ratings and 5 is distinctively superior.
29 Undertank leaks are often very difficult to detect. The potential damage to the environment from
an undertank leak is decreased greatly when an undertank liner is in place. EPA found that a number of
potential designs are available for undertank containment and leak detection and evaluated two commonly
used designs shown in Exhibit 4-14. Both designs include leak detection, which should be an integral part
of every undertank containment design.
30 Information in this section is intended to provide a general comparison of liner materials and their
relative advantages and disadvantages. This information should not be construed as constituting
governmental approval of any1 specific design or product; EPA does not endorse or recommend specific
products or materials.
59
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EXHIBIT 4-15
COMPARATIVE ANALYSIS OF LINERS FOR ENVIRONMENTAL PROTECTION AND CONSTRUCTION EASE
FEASIBILITY CRITERIA
*
ENVIRONMENTAL PROTECTION
1. Inherent Permeability
2. Workmanship Requirements
3. Chemical Resistivity
4. Resistance to Weathering
Caused by:
ultraviolet exposure
freeze/thaw action
erosion
wet/dry cycles
5. Resistance to Other Damage
Caused by:
. vandalism
animal activity
undesirable vegetation
CONSTRUCTION EASE
1. Adverse Site Conditions^
2 Adverse Climatic Conditions^
3. Material Availability
4. Availability of Skilled Labor
ALTERNATIVE SYStEMS
IMPERVIOUS SOIL
NATIVE
. SILTY
CLAY
3
High
5
'
NA
2
2
2
5
2
- 2
' High
High
2
2
MODIFIED
SOIL
3
High
5
NA
2
2
1
5
2
2
Low
Moderate
3
5
CONCRETE
UNCOATED
<
2
Moderate
5
4
2
4
4
'
5
- >5
3
High
Moderate
'3
4
COATED
4
Moderate
4
f
- 3
3
4
4
3
4
5
High
Low
3
3
GEOMEMBRANES
POLYMERIC
SHEETS
4-
Moderate
2 to 4
3
5
5
5
2
.1
S
Low
High
5
3 to 4
BENTONITE
MAT
4
Low
5
NA
3
3
1
...
5
2
2 ,
Moderate
High
,5
4 '
POLYSULFIDE
SPRAY-ON
5
Moderate
4
3
5
S
5
3
3
5 ii
II
Moderate
Low
5
3
STEEL
5
Moderate
5
-
5
5
5
5
' 4
5
5
'"
. ' Moderate
Moderate
4
2
NOTES: -' "High" indicates that construction of the liner would be difficult under the conditions listed under the Feasibility Criteria. "Moderate" indicates that construction of the
liner would be moderately difficult, and "Low" indicates that construction of the liner would be relatively easy under the conditions listed under the Feasibility Criteria
NA = Not Applicable
Alternatives are rated relative to each other on a scale from 1 tp 5 (inferior to superior)
60
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4.4.1 Protection .of the Environment and Construction Ease
Impervious soil. Impervious soils (see footnote #26) include native silty clay and
soils mixed with bentonite. The inherent permeability of these soils is rated in the mid-
range among the liner materials that were evaluated; however, oil resistivity is high.
Impervious soil liners are susceptible to degradation from-weathering, animal activity, and
vegetation. Construction of liners from impervious soils is relatively simple at new
facilities, but generally more difficult at existing facilities.
Concrete. Concrete is widely used for secondary containment, especially at
smaller facilities. The ability of concrete containment structures to protect the
environment varies depending on the condition of the concrete surface, particularly its
degree of cracking. Uncoated concrete is more permeable than coated concrete, whose
permeability is similar to that of geomembranes, and both coated and uncoated concrete
are highly resistant to oil. Both'coated and uncoated concrete are relatively resistant to
weathering except that uncoated concrete is susceptible to damage from freezing and
thawing especially if the concrete is cracked. Concrete systems are generally easy to
construct in new applications and more difficult for retrofit applications of existing
obstructions such as pumps and pipes.
Geomembranes. A wide range of geomembrahe liner materials are available,
including polymeric sheets, bentonite mats, and spray-on coatings compounded with
polysulfide. The inherent impermeability of liners made from these materials is high, and
oil resistivity is generally good. These protective qualities can be degraded, by weathering
caused by exposure to the sun and, in the case of bentonite mats, cracking caused by
wet/dry cycles. Exposed geomembranes and polysulfide coatings may be susceptible to
damage from vandalism or animal activity. Animal activity and undesirable vegetation
are also of concern with bentonite mats. Repairs to geomembrane liners may be costly
, and must be made promptly upon discovery. The ease of installing geomembrane liners
varies depending largely on the stiffness of the material. Geomembrane liner systems
can be installed in either new or existing facilities.
Steel. Steel liner systems are not widely used, although they are well suited for
small horizontal tanks (up to approximately 20,000-gallon capacity) and when space
limitations require erection of a high vertical wall. Because steel resists all oil products
and is essentially impermeable, it is highly protective of the environment. Compared to
other liner systems, steel liner systems offer the greatest resistance-to weathering and
other damage. Construction of steel liners requires extensive design and planning prior
to installation, and steel liner systems ar6 generally more difficult to install in existing
facilities than in new facilities because of existing obstructions such as pipes and pumps.
Retrofitting existing containment areas may pose safety problems because welding may
be required close to flammable products; as a result, tank contents may have to be
removed and the tank cleaned before the installation can begin. Compared to other
liner systems, steel is not economical for most facilities.
61
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4.4.2 Estimated .Facility Costs
The estimated capital unit costs for both retrofitting existing facilities and for
installing liner systems at new facilities are shown in Exhibit 4-16. O&M costs are
addressed qualitatively in Exhibit 4-17. The cost estimates presented in the exhibits are
meant to be representative estimates based on the characteristics of the model facilities
rather than definitive estimates applicable to a specific type of facility. Capital costs for
existing facilities are based on installing a secondary containment liner system (except
underneath tanks) and installing double bottoms on all vertical ASTs.31 For new
facilities, costs are estimated assuming that undertank liners would be installed along with
the secondary containment liner.
The exhibits do not include steel liners because their cost is prohibitive except in
special circumstances. Costs are presented in 1991 dollars, corresponding to when most
of the information on installation and O&M costs was collected. The cost estimates
presented in the exhibits were developed based on information in the 1991 Means
construction cost data estimating guide, which presents average costs for 30 major
cities.'2 In addition, the cost estimates reflect the following assumptions:
Grubbing, soil excavation, and grading costs are not included in the cost
estimates for new facilities, but are included in the estimates for installation
at existing facilities.
Concrete liners are 4 inches thick.
, Liners comprising polymeric sheets are placed on top of a layer of sand 6
inches deep.
Liners comprising bentonite mats are covered with 6 inches of soil that is
seeded with grass, fertilized, and mulched.
The cost of installing an impervious soil liner involves the material price,
loading, hauling 5 miles one way, dumping, spreading, and compacting.
The liner is assumed to be covered with 6 inches of soil that is seeded with
grass, fertilized, and mulched.
31 Vertical ASTs are assumed to rest on concrete pads that provide protection comparable to a double
bottom. Horizontally mounted tanks are assumed to be supported off the ground by saddles, which allows
installation of the secondary containment liner beneath them.
32 Means Site Work and Landscape Cost Data, llth Edition, R.S. Means Co..
62
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EXHIBIT 4-16
COMPARATIVE COST ANALYSIS OF LINER MATERIALS BY MODEL FACILITY3/
MODEL
FACILITY*'
#1 New Facility
Existing Facility
#2 New Facility
Existing Facility
#3 New Facility
Existing Facility*
#4 New Facility
Existing Facility-'
#5 New Facility
Existing Facility^
#6 New Facility
Existing Facility*'
ESTIMATED LINER CAPITAL COSTS PER MODEL FACILITY*'
IMPERVIOUS SOIL
Native SJlty Clay
$5,000
$6,000
$11,000
$15,000
$18,000
$38,000
$28,000
$50,000
$63,000
$117,000
, $1,606,000
$3.404,000
Modified Soil
$5,000
$5,000
$9,000
. $11,000
$16.000
$36.000
$24,000
$43,000
$64,000
$116.000
$1.568,000
$3,283,000
CONCRETE
Uncoated
$3,000
$4,000
$9,000
$11.000
$17,000
$36,000
$25.000
$43,000'
'$84,000
$134.000
$2.304.000
$3,930,000
Coated
$8,000
$9,000
$22.000
$24,000 ^
$28.000
$56.000
$47.000
$66,000
$141,000 '
$191,000
$4.140,000
$5,767,000
GEOMEMBRANES
Polymeric Sheets
$4,000
$7,000
$13,000
$is,ooo
$20,000
$42,000
$33,000
$56,dOO
$95,000
$150,000
$2,103,000
$3,807,000
Bentonite Mat
$4,000
$4,000
$9,000
$12.000
$17,000
$36.000
$25,000
$43.000
$70,000
$121,000
$1,894,000
$3.569,000
t'orysulfide Spray On
$5,000
$5.000
$12,000
$14,000
$19,000
$39,000
$31,000
$48.000
$97,000
$147.000
$2,575,000
$4,186.000
H In 1991 dollars.
-' The six "model" facilities are summarized in Exhibit 4-7. - "...
- 30-percent contingency included. _ , _
* $27.000 of cost is for double bottom tank retrofit for three 10-foot diameter tanks.
- $23,000 of cost is for double bottom tank retrofit for two 12-foot diameter tanks
$81.000 of cost is for double bottom tank retrofit for three 12-foot diameter tanks and double bottom tank retrofit for one 40-foot diameter tank.
$ $2.534,000 of cost is for double bottom tank retrofit for two 80-foot diameter, three 120-foot diameter, and four 200-foot diameter tanks
Note The retrofit costs for Model Facilities 1 and 2 do not include double bottom retrofit costs because the tanks at these model facilities are horizontal, saddle-mounted tanks (see Exhibits
4-1 and 4-2) ' . ,
63
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EXHIBIT 4-17
ANNUAL OPERATIONS AND MAINTENANCE COSTS
TYPE
Operational
Liner System
Repair
IMPERVIOUS SOIL
Native
Silty
Clay
Low
Low
Modified
Soil
Low
Low
CONCRETE
Uncoated
Moderate
Moderate
Coated
Low
High
GEOMEMBRANES
Polyirtenc
Sheers
Low
High
Bentonite
Mat
Low to High
Moderate
Polysulfide
Spray On
Low
High
Retrofitting of double bottoms occurs during a routine inspection and
maintenance period when the tank has been drained, cleaned, and
temporarily taken out of service.
' Soils with high permeability can be modified to produce an impervious soil
. liner by applying 3 pounds of bentonite to each square foot of soil. The
liner is covered with 6 inches of soil that is seeded with grass, fertilized, and
mulched.
Tank foundation liners are installed at new, large and medium sized
facilities. This involves installation of a HOPE liner, a 2-inch sand layer,
cathodic protection, and an additional. 2-inch sand layer. At existing
facilities, additional equipment such as cranes and temporary tank pads are
required for retrofitting undertank liners.
Large facilities have roads within secondary containment structures.
Crushed stone roads -are constructed over a liner system consisting of a
geomembrane and impervious soil layers. In the case of concrete liners,
the concrete is thickened along the course of the road.
As indicated in Exhibit 4-16, for all liner systems, the cost to retrofit liners is
higher than installing liners at new facilities because of the added difficulty and cost
associated with working around existing tanks and appurtenances (e.g., piping). In
addition, certain general conclusions are apparent from the table:
ซ Coated concrete was the most expensive alternative for all model facilities.
Uncoated concrete, impervious modified soil, bentonite mat, and
polysulfide spray-on liner systems were the least costly for retrofitting of
existing facilities with total storage capacities of less than approximately
100,000 gallons.
64
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For a large facility (e.g., total storage capacity of greater than or equal to 1
million gallons), native soil -and bentonite mat liner systems were the least
costly alternatives.
For all model facilities, the bentonite mat liner system was consistently one
of the least expensive alternatives.
For all mode] facilities, the costs for polymeric sheet liner systems were
similar to the costs of other options; however, polymeric sheets were never
the least expensive alternative.
A range of costs (expressed in dollars per gallon of storage capacity) to install new
and retrofitted liners at the six model facilities is presented in Exhibit 4-18. These ranges
are based on the least and most expensive liner cost estimates presented in Exhibit 4-16.
Generally, the larger the facility, the lower the price per gallon of capacity to construct a
liner system because, for most secondary containment structures of typical proportions,
the volume of the secondary containment structure increases at a faster rate than its
area. Because secondary containment structures are designed to hold the entire contents
of the largest tank or aggregate volume of tanks permanently manifolded together within
the structure, the volume of the structure is typically roughly equivalent to the storage
capacity of the tank or tanks within- that structure. Because the increase in surface area
results in costs roughly equivalent to the incremental material and installation cost of
liners {which cover the surface area of the secondary containment) and the increase in
volume corresponds with the additional amount of available storage capacity, the ratio of
available storage volume to surface area increases with tank size. This, in turn, translates
into declining cost per gallon of- storage capacity. For example, if two facilities have
secondary containment areas of 50,000 square feet, and one has a dike height 6 inches
higher than the other, the difference in height would add very little to the cost of
installing a liner (the increase in lined surface area would be approximately 45 to 50
square yards), but the facility could store as much as 180,000 more gallons of oil.
As shown in Exhibit 4-18, the cost for installing a liner system at an AST with a
nominal capacity at a small end-user facility (Model Facility 1) is estimated to range from
$1.50 to $4.50 per gallon of storage capacity. A liner system at a large oil terminal
facility (Model Facility 6) is estimated to cost approximately $0.03 to $0.11 per gallon of
capacity. In general, the costs to install liner systems at facilities would be better
represented in dollars per gallon of throughput rather than dollars per gallon of storage
capacity since throughput is a better representation of the economical value of the tank;
however, EPA lacks sufficient data on average throughput to present costs in this
manner.
Existing ASTs are assumed to be retrofitted with double bottoms to prevent
undertank discharges. The cost of retrofitting ASTs with double bottoms is proportional
to the area of the tank bottom. These retrofits were found to vary from $15 to $115 per
65
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EXHIBIT 4-18
ESTIMATED LINER CAPITAL COST PER GALLON OF STORAGE CAPACITY
MODEL
FACILITY
1
2
3
4
5
'6
COST FOR RETROFIT
INSTALLATION
(DOLLARS/GALLON)
Low
$2.00
$0.46
$0.80
$0.41
$0.36
$0.07
High
$4.50
$1.00
$1.24
$0.63
$0.59
$0.11
COST FOR NEW
INSTALLATION
(DOLLARS/GALLON)
Low
$1.50
$0.38
$0.36
$0.23
$0.19
$0.03
High
$4.00
$0.92 .
$0.62
$0.45
$0.43
$0.08
square foot, depending on the tank size, with the higher cost per square foot associated
with smaller tanks. New installations of undertank liners can be completed for
approximately $4 to $34 per square foot, depending on tank size.
Annual p&M costs were examined qualitatively in the analysis. They are
generally low for impervious soils and geomembrane liners (except for bentonite mats,
which must be hydrated regularly). Operational costs for coated concrete are lower than
uncoated concrete; however, the costs to repair cracks, deteriorated expansion joints, and
sealants for coated concrete systems are greater. Although liner manufacturers rated
operational costs for bentonite mats as low, facility owners and operators who had
installed these types of liners stated that the operating costs were high. Exposed
geomembrane liners are susceptible to damage from vandalism and accidents, and any
needed repairs may be costly.
EPA determined that there is not sufficient information to quantify the number,
size, and costs associated with releases that liner usage may prevent. However, initial
research does indicate that the cost of remediating oil releases will vary greatly
depending on the characteristics of the oil (e.g., viscosity), characteristics of the soil and
ground-water (e.g., depth to ground water, velocity of flow, depth of saturation, and
effects from nearby pumping), external factors such as weather, and remediation
technique used. Preliminary analysis suggest that remediation costs can range up to
greater than $100 per gallon of oil released.
66
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4.5 LEAK DETECTION METHODS
Current technology has produced a variety of leak detection systems including
alarms, inventory control, acoustic emissions testing, volumetric measurement, and
interstitial space monitoring, and industry is aggressively developing technology to make
leak detection more reliable. EPA has found that leak detection systems are part of an
effective liner system for ASTs, serving to bring a leak or spill to the owner's or
operator's attention while the liner prevents leaks and spills from reaching soil or ground
water.
Leak detection methods are typically classified as either continuous or periodic
systems, although many current technologies may be configured to provide either type of
operation. Continuous leak detection provides uninterrupted monitoring and,
consequently, instant notification of tank failure or an oil discharge. Examples of
continuous systems are overfill alarms, overfill sumps, tell-tale drains, interstitial space
monitors, and horizontal wells with electronic fluid-flow indicators. These systems are
most effective in preventing adverse environmental impacts of discharges when integrated
with leak containment systems because leak detection systems by themselves only alert
facility operators to the existence of the discharge. For example, when used in
conjunction with double tank bottoms, interstitial space monitoring may consist of a
hydrocarbon sensitive tape lying between a tank's external bottom and its internal double
bottom. Use of tell-tale drains on ASTs also is common at facilities that have installed
double bottom retrofits. Tell-tale drains are used to check the integrity of the double
bottom by providing a drain path for any liquid that has accumulated in the space
between the two bottoms. While overfill alarms and sumps are a form of leak defection,
they do not provide notification of tank bottom failure.
Periodic leak detection involves checks or tests at regular intervals to determine
the occurrence of oil discharges or tank bottom'failure. The type of system used
generally depends on the type and size of the tank being monitored. Periodic system's
include: internal/external visual inspections; pressure/vacuum testing of tanks and piping;
volumetric precision testing of the tank; inventory record and measurement
reconciliation; acoustic emissions testing; and chemical gas detection methods. OSCs
agreed that visual inspection is the most common form of leak detection at AST facilities.
When visual leak detection is used, daily records need to be maintained, interpreted, and
reviewed to provide the most sensitive leak detection threshold possible. The most
significant drawback to visually inspecting vertically mounted tanks is the inability to
examine the tank bottom while the tank is in service.
Periodic leak detection systems are generally required in States that regulate
ASTs; however, these methods are not adequate in certain situations. For example,
visual inspections cannot be conducted for the bottom or internal area of vertical ASTs
without the removal of stored product: In such circumstances, other non-invasive
periodic methods (i.e., those that do not require tank entry) such as acoustic emissions
67
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testing and precision volumetric detection, must be used. These methods can have
detection thresholds as low as one gallon of leaking product per hour.
Intrusive methods of leak detection have an extremely high detectability rate
because areas that are suspected to have failed can ฑ>e examined by other means.of
integrity testing (i.e., ultrasonic, radiographic, dye penetrant, magnetic particle, and
vacuum box testing). Internal inspections can be expensive and result in significant tank
down-time; consequently, intervals between tests have historically been as long as 20
years. Internal inspections alone may not be adequate to identify tank bottom failures
because of the long time between bottom failure and leak discovery given the average
time between tests.
Other non-invasive methods of leak detection such as inventory reconciliation can
be useful at detecting large leaks; however, inventory checks may not detect slow,
continuous leaks because of the normal margin of error in making measurements and the
effects of temperature-related expansion of product volume in the tank. Although the
types of systems described in the paragraphs above are effective for detection of smaller
leaks, their expense can be significant.
68
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5. RECOMMENDATIONS
This chapter presents the Agency's recommendations. The recommendation of
this Report to Congress is based primarily on the results of EPA's study of liners as well
as insights the Agency has gained over the past 20 years into the problems posed by
onshore AST facilities. As a first step toward addressing the potential risks to public
health and the environment as a result of contamination from AST facilities located near
navigable waters, the Agency recommends initiating, through a Federal Register notice or
stakeholder workgroups, a process involving broad public participation to develop a
voluntary program. This process would give stakeholders the opportunity to share new
or additional data and information to characterize the sources, causes, and extent of soil
and ground-water contamination and efforts underway to address contamination at AST
facilities nationwide. Such data are critical to determining the most appropriate and
effective means to reduce contamination.
As envisioned by EPA, the voluntary program would be designed to encourage
facility owners or operators, through incentives such as technical assistance, cost savings,
and public recognition, to identify and report contamination, take actions to prevent leaks
and spills, and remediate soil and ground-water contamination. This program would
complement the Agency's efforts to develop cleaner, cheaper, and smarter approaches to
environmental problems through innovative solutions that depart from the traditional
regulatory approach. The Agency favors a voluntary, rather than regulatory, approach at
'this time in order to provide greater flexibility in addressing contamination at the vast
range of oil storage facility types, sizes, and locations. A voluntary program could focus
more directly on facilities that may pose the greatest hazard to public health and the
environment. For example, the program may initially focus on larger, older facilities, and
facilities located near waters, sensitive areas, or populations. In addition, a voluntary
approach could allow implementation of the most appropriate prevention and cleanup
activities for each facility. The program would look for incentives for industry to
implement reasonable and cost-effective measures to address existing problems and help
prevent future ones.
EPA views such a program as a cooperative effort among EPA, State
governments, industry, and environmental groups. Based on this study's findings, EPA
believes the program should include commitments from facilities to:
Address known contamination and to assure that existing contamination will
not be allowed to migrate offsite;
Report to appropriate government agencies the status of facility
contamination and actions underway to address any problems;
69
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Adopt the most protective appropriate prevention standards and upgrade
equipment as necessary; and
* Monitor and/or implement leak detection to ensure that new leaks are .
addressed.
Provided stakeholders commit to the voluntary approach, a successful program will entail
the identification .of specific actions for participating facilities to undertake, and include
means for objectively measuring results.
' /
EPA has evaluated the feasibility of conducting a voluntary program to address
the problem of AST releases and concluded that a voluntary program is worth pursuing
for the following reasons:
-+ The universe of large AST facilities is relatively easy to define and is
represented by several large trade associations.
The program is consistent with the Agency's goal of developing and
promoting innovative approaches to achieve environmental goals.
Clear, achievable goals are apparent (e.g., to mitigate the spread of existing
contamination and to prevent future releases).
Hexible approaches (i.e., numerous technological options and management
practices) are available to address the problem, thus allowing participants
to implement the program in a tailored manner appropriate to their
circumstances.
EPA is committed to providing technical assistance as well as other
incentives.-
There are established industry and state practices and standards that can
be used as a basis for constructing a comprehensive program.
EPA identified several characteristics shared by successful voluntary programs.
These include:
The program must have goals that are clearly defined up front This
assures that participants are working toward the same objectives and
provides a framework that increases efficiency.
The program must have achievable goals The goals of the program must
be realistic in order to ensure widespread participation and avoid wasting
resources. - . '
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The program must offer useful incentives Successful voluntary programs
offer benefits to attract and maintain the interest of participants. Such
incentives have included:
Cost savings/long-term profits/more efficient operations (release
prevention reduces product loss);
Publicity (newsletters, press releases, etc.);
Recognition (certificates of participation and achievement);
Technical assistance (advice and sources of information);
Reducing or eliminating the need for regulations; and
Other types of assistance, such as assistance in identifying
Federal/State/private financial options (i.e., information on insurance
programs, State grant programs, etc.).
EPA will vigorously pursue other incentives, and will work with interested
parties over the coming months to help identify them.
The program must have a structure in place to work with all potentially
affected and interested parties and promote continued participation We
believe it is imperative that a voluntary program ensure broad participation
and be structured so that all involved can affect the decision-making
process.
- The program must effectively track progress and disseminate success stories
Project tracking enables the Agency to determine whether the program
is successful, identify areas where adjustments are needed, resolve issues,
and plan future goals. -Success stories help foster new involvement.
The program must have the support of the lead agency, the public, and
participants For a program to be successful, it needs a real and strong
commitment of those involved.
In keeping with the Agency's initiatives to develop innovative, common-sense
approaches to environmental problems, EPA supports a voluntary prevention and
cleanup program as a first step in addressing the environmental problem presented by
contamination from AST facilities. Industry representatives have expressed their support
for such a program as a more cost-effective, flexible alternative than traditional
regulation. EPA fully supports such an attempt, and believes it will be successful,
provided that it has the full commitment of those involved. The Agency believes it is
essential that stakeholders have the opportunity to participate in the development and
execution of this voluntary program and will establish an open process for public input
into the program's design and implementation.
71
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REFERENCES
American Petroleum Institute (API), "Aboveground Storage Tank Survey," prepared by
Entropy Limited, April 1989.
American Petroleum Institute (API), "A Survey of API Members' Aboveground Storage
Tank Facilities," prepared by API Health and Environmental Affairs Department,
July 1994.
American Petroleum Institute (API), "Welded Steel tanks for Oil Storage," API Standard
650, July 1993.
Means Site Work and Landscape Cost Data, llth Edition, R.S, Means Co., 1991.
National Fire Protection Association (NFPA), Flammable and Combustible Liquids Code
(NFPA 30) Section 2-2.3.3, 1993 edition.
New York State Department of Environmental Conservation, (NYDEC Database).
Office of Management and Budget Circular No. A-94 (57 FR 53519).
Suffolk County Department-of Health Services, "Final Report: Tank Corrosion Study,"
1988.
U.S. Coast Guard and U.S. Department of Transportation, "Control of Pollution by Oil
and Hazardous Substances, Discharge Removal," 33 CFR part 153, 7-1-93 edition.
i
U.S. Environmental Protection Agency, "Discharge of-OH," 40 CFR part 153, 7-1-93
edition.
U.S. Environmental Protection Agency, Emergency Response Division, "Estimate of the
Number of Aboveground Storage Tanks at Onshore Facilities," October 1994.
f
U.S. Environmental Protection Agency, Emergency Response Division, "Investigating the
Risk Posed by Different Sizes of Facilities Potentially Regulated by the Oil
Pollution Prevention Regulation," May 1993.
U.S. Environmental Protection Agency, Emergency Response Division, "Regulatory
Impact Analysis of Revisions to the Oil Pollution Prevention Regulation," Draft
Report, 1991.
73
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U.S. Environmental Protection Agency, Emergency "Response Division, "Regulatory
Impact Analysis of Revisions to the Oil Pollution Prevention Regulation (40 CFR
112) to Implement the Facility Response Planning Requirements of the Oil
Pollution Act of 1990," June 1994.
U.S. Environmental Protection Agency, Emergency Response Division, "Spill Prevention,
Control, and Countermeasures Facilities Study," January 1991.
U.S. Environmental Protection Agency, Emergency Response Notification System,
(ERNS Database).
U.S. Environmental Protection Agency, "Oil Pollution Prevention," 40 CFR part 112, 7-1-
93 edition. ' '
\v
U.S. Environmental Protection Agency, "Oil Pollution Prevention; Non-Transportation-
Related Onshore Facilities," 58 FR 8824, February 17, 1993.
U.S. Environmental Protection Agency, "Standards for Owners and Operators of
Hazardous Waste Treatment, Storage, and Disposal Facilities," 40 CFR part 264,
7-1-93 edition.
U.S. Environmental Protection Agency, "Technical Standards and Corrective Action
Requirements for Owners arid Operators of Underground Storage Tanks (USTs),"
40 CFR part 280, 7-1-93 edition.
Virginia Department of Environmental Quality (VADEQ), "The Virginia DEQ
Aboveground Storage Tank Regulations," April 4; 1994.
Virginia Regulation 680-14-12: Facility and AST'Registration Requirements, effective
September 22, 1993.
"World Spill Briefs," Golub's OU Pollution Bulletin, Vol. 5 No. 12, May 1993, p. 7.
74
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APPENDIX A: STATE REGULATIONS
EPA reviewed current and proposed AST regulations for the 50 States to gather
information on liner systems and to estimate the number of facilities currently required to
use liners as a result of State regulation. Exhibit A-l summarizes the results of this
review. The following components of AST regulatory programs were examined:
Status of AST requirements (i.e., full AST regulations, NFPA or other fire
codes only, proposed AST regulations with NFPA or other fire codes, or
proposed AST regulations only);
Status of liner requirements (current, proposed, or none);
Status of spill data collection (full AST regulations, some spill data
collection, AST data base started but is not extensive or easy to access, or
spill data collected but not required by regulation); and
/ Whether a cost/benefit data analysis was performed.
Section 3.1.2 provides a more detailed discussion of the nine States (AK, CO, FL, MO,
NJ, NY, RI, SD, and WI) that have promulgated or proposed regulations specifying the
use of "impermeable" secondary containment systems, liners, or other diversionary
structures and systems.
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EXHIBIT A-l
STATE REGULATIONS33
STATE
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
BASIS FOR
AST
REQUIRE-
MENTS
1
X
1
X
x
1
1
1
X
1
1
1
1
1
1
1
1
1
LINER
REQUIREMENT
Current
X
>
X
"
Proposed
X
Spill Data
Collected
Some
*
*
*
Some
X
Some
*
*
Cosl/B~n*fit
Ditia
X
Comments
Guidelines available
Liners required at new facilities
only
Working on draft regulations
-
Proposed AST regulations
Proposed AST regulations
j
Began data base in '92; no
regulations; local control
33 Information as of April 1994.
LEGEND
X
1
*
o
AST regulation
NFPA or other fire codes
data base started, but not extensive nor easy to access
spill data is collected, but not required by regulation
proposed AST regulation
76
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STATE
Maine '
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New
Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
BASIS FOR
AST
REQUIRE-
MENTS
1
X
X
1
X
1
1
1
1
1
1
X
1
X
T.
T.
1
1
1
X
LINER
REQUIREMENT
Current
X
X
X
-
Proposed
Spill Data
Collected
0
X
X
*
X
*
X
X
0
'0
0
, o
' *
Cost/Benefit
Data
X
X
X
,
Comments
Some oil terminal regulations,
proposed AST regulations
currently under development
Regulations only cover tanks >
10,000 gallons
No regulations; local control
Cost/benefit data from the failed
Imer requirement available
Requires liners on a case by case
basis
No regulations; local control
-
Proposed regulations currently
under development; no
provisions available
New and retrofit must meet API
standards
LEGEND
X
1
AST regulation
NFP A or other fire codes
data base started, but not extensive nor easy to access
spill data is collected, hut not required by regulation
proposed AST regulation .
77
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STATE
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
BASIS FOR
AST
REQUIRE-
MENTS
X
1
, k
X
1
X
1
1
X
X
1
X
1
LINER.
REQUIREMENT
Current '
X
X
X
Proposed
.
Spill Data
Collected
X
o
<
Cost/Benefit
Data
/
Comments
No regulations; local control
f
Regulation applies to facilities '
with AST capacity in excess of
25,000 gallons of oil. Requires
installation of release prevention
barriers either under or in the
bottom of new or retrofitted
tanks.
Only covers marine terminals
LEGEND
X
1
*
o
AST regulation
NFPA or other fire codes -
data base started, but not extensive nor easy to access
spill data is collected, but not required by regulation
proposed AST regulation
78
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APPENDIX B: MODEL FACILITIES
This appendix describes how EPA used previous analyses to determine how the
model facilities developed for this analysis would represent the diversity of facilities with
ASTs that do not have liner systems in place.
B.I Allocation of AST Facilities into Size and Use Categories
As described in Chapter 2, the universe of AST facilities that currently is
estimated not to have liners was divided into size categories based on their storage
capacity and use categories (see Exhibit 2-6). This classification scheme has been used in
a previous EPA analysis supporting revisions to the Oil Pollution Prevention
regulation.34 EPA's earlier analysis also estimated the storage capacity for typical (i.e.,
representative) facilities in eight of the nine size and use categories. (Because only a
negligible number of large facilities were estimated to exist, no typical storage capacity
was estimated for this category.) The results of the analysis are presented in Exhibit B-l.
EXHIBIT B-l
TYPICAL STORAGE CAPACITIES FOR FACILITIES
FROM PREVIOUS EPA ANALYSIS
Size and Use
Category
Small
Medium
Large
Production
37,800 gallons
96,600 gallons
Not Applicable
Storage/Distribution
10,000 gallons
250,000 gallons
21,400,000 gallons
Storage/Consumption
2,000 gallons
205,000 gallons
4,028,000 gallons
To ensure consistency in its analyses, EPA used the typical storage capacities from
this earlier analysis to determine which model facilities developed in this analysis best
represented each size and use -category. Specifically, EPA compared the typical storage
capacities used in the previous analysis (and presented in Exhibit B-l) with the assumed
storage capacities of the model facilities developed for this report. If a single model
facility from this report closely agreed with the storage capacity from the earlier analysis,
then that model facility was assumed to represent all of the AST facilities that currently
do not have liners in that size and use category (as presented in Exhibit 2-6). For
34 U.S. EPA, Emergency Response Division, "Regulatory Impact Analysis of Revisions to the Oil
Pollution Prevention Regulation (40 CFR 112) to Implement the Facility Response Planning
Requirements of the Oil Pollution Act of 1990", June 1994.
79
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example, Model Facility 1 has an assumed storage capacity of 2,000 gallons, which equals -
the typical storage capacity of small storage/consumption facilities from EISA's earlier
analysis. Consequently, all 198,529 small storage/consumption facilities are considered to
be represented by Model Facility 1.
Where the typical storage capacity of facilities in a size and use category did not
closely agree with a single model facility from'.this report, two model facilities were used
to represent that-size and use category. The allocation of facilities between the two
model facilities generally was based on the difference between the typical storage
category, as presented in Exhibit B-l, and the assumed storage capacities of the model
facilities. For example, small storage/distribution facilities are estimated to typically have
a total storage capacity of approximately 10,000 gallons, for which no single model facility
in this report corresponds closely. Therefore, small storage/distribution facilities are best
represented by a mix of Model Facilities 1 and 2, which are assumed to have 2,000 and
24,000 gallons of storage capacity, respectively, As the "typical" small storage/distribution
facility (10,000 gallons) is closer in storage capacity to that of Model Facility 1 (2,000
gallons) than Model Facility 2 (24,000 gallons), facilities were allocated disproportionately
to Model Facility 1. Of the estimated 4,554 small storage/distribution facilities, 2,898
facilities are* estimated to be best represented by Model Facility 1, and the remaining
1,656 facilities are estimated to be best represented by Model Facility 2. The model
facilities selected to represent each size and use category and the allocation ratios are
presented in Exhibit B-2.
EXHIBIT B-2
CATEGORIZATION OF FACILITIES NOT CURRENTLY REQUIRED
TO INSTALL LINERS
Size and
Use
Category
Small
Medium
Large
Production
Model Facility 2 (34%)
Mode! Facility 3 (66%)
Model Facility 4
(100%)
Not Applicable
Storage/Distribution
Model Facility 1 (64%)
Model Facility 2 (36%)
Model Facility 3 (41%)
Model Facility 5 (59%)
Storage/Con sumption
Model Facility 1
(100%)
Model Facility 4 (54%)
Model Facility 5 (46%)
Model Facility 6 (100%)
In the case of medium storage/distribution facilities, however, an alternative
formula was used. The medium storage/distribution category of facilities includes
gasoline service stations with ASTs. Historically, most gasoline service stations stored
product in USTs; however, where land limitations require or building codes allow, ASTs
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are used at these facilities for product storage. Model 3, with a storage capacity of
45,000 gallons, is an effective representation of such medium-sized gasoline service
stations. As shown in Exhibit 3-2, there are aft estimated 5,967 medium-sized gasoline
service stations. Therefore, 5,967, of the 14,681 medium storage/distribution facilities are
represented by Model 3, and the remaining 8,714 are represented by Model 5, whose
assumed storage capacity of 325,000 gallons is closest to the typical storage capacity of
facilities in this size and use category (i.e., 250,000 gallons).
To determine the total number of facilities that each model facility represents, the
percentages in Exhibit B-2 were multiplied by the estimated number of AST facilities in
the corresponding size and use category in Exhibit 2-6 and the amounts were summed by
model facility:
Model Facility 1: 201,427
Model Facility 2: 49,296
Model Facility 3: 97,277
Model Facility 4: 55,623
Model Facility 5: 13,663
Model Facility 6: 3,927
2,898 small storage/distribution facilities .
All- small storage/consumption facilities
1,656 small storage/distribution facilities
47,640 small production facilities
91,310 small production facilities
5,967 medium storage/distribution facilities
All medium production facilities
5,880 medium storage/consumption facilities
8,714 medium storage/distribution facilities
4,949 medium storage/consumption facilities
All large storage/consumption facilities
421,213 facilities
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