United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/600/R-97/085
September 1997
&EPA
Stata-of-the-Art
Procedures and
Equipment for Internal
Inspection and Upgrading of
Underground Storage Tanks
^™*^ ^^gP
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EPA/600/R-97/085
September 1997
State-of-the-Art Procedures and Equipment
for Internal Inspection and Upgrading
of Underground Storage Tanks
by
Jairus D. Flora, Jr.
G. Joe Hennon
William D. Glauz
Midwest Research Institute
Kansas City, Missouri 64110
Contract No. 68-C2-0108
Work Assignment No. 4-17
Carolyn Esposito
Robert Hillger
Work Assignment Managers
Water Supply and Water Resources Division
National Risk Management Research Laboratory
Edison, New Jersey 08837- 3679
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Edison, New Jersey 08837 - 3679
Printed on Recycled Paper
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DISCLAIMER
The U.S. Environmental Protection Agency through its Office Of Research and
Development funded and managed the research described here under Contract
No. 68-C2-0108 to IT Corporation, it has been subjected to the Agency's peer and
administrative review and has been approved for publication as an EPA document.
Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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The U.S. Environmental Protection Agency is charged by Congress with protecting the
Nation's land, air and waste resources. Under a mandate of national environmental
laws, the Agency strives to formulate and implement actions leading to a compatible
balance between human activities and the ability of natural systems to support and
nurture life. To meet this mandate, EPA's research program is providing data and
technical support for solving environmental problems today and building a science
knowledge base necessary to manage our ecological resources wisely, understand
how pollutants affect our health, and prevent or reduce environmental risks in the
future.
The National Risk Management Research Laboratory is the Agency's center for
investigation of technological and management approaches for reducing risks from
threats to human health and the environment. The focus of the Laboratory's research
program is on methods for the prevention and control of pollution to air, land, water and
subsurface resources; protection of water quality in public water systems; remediation
of contaminated sites and ground water; and prevention and control of indoor air
pollution. The goal of this research effort is to catalyze development and
implementation of innovative, cost-effective environmental technologies; develop
scientific and engineering information needed by EPA to support regulatory and policy
decisions; and provide technical support and information transfer to ensure effective
implementation of environmental regulations and strategies.
This publication has been produced as part of the Laboratory's strategic long- term
research plan. St is published and made available by EPA's Office of Research and
Development to assist the user community and to link researchers with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
II!
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Abstract
This report supplements the previous State-of-the-Art Procedures and Equipment for Internal
Inspection of Underground Storage Tanks published in 1991 by the EPA. The present report
updates and provides descriptions of additional tank inspection technologies, specifically,
noninvasive statistical modeling, remote video inspections, and robotic ultrasonic inspections. A
newly developing technology of thermal waving is also described. In addition, this document
describes the state of the art of methods for upgrading underground storage tanks. Two
established methods of upgrading—tank lining and cathodic protection—are described in addition
to two newer methods—installation of a membrane liner and installation of a rigid internal tank.
This report was submitted in fulfillment of Contract No. 68-C2-0108 by Midwestern
Research Institute, under subcontract to IT Corporation, under the sponsorship of the U.S.
Environmental Protection Agency. This report covers a period from October 1,1993 to
December 31, 1996, and was completed as of November, 1996.
IV
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TABLE OF CONTENTS
Disclaimer ii
Foreword xii
Abstract iv
Table of Contents v
Figures vi
Acknowledgments vii
List of Abbreviations viii
1 Introduction 1
1.1 Background 1
1.2 Purpose 3
1.3 Approach 4
1.4 Selecting an Inspection/Assessment Technology 4
1.5 Selecting an Upgrading Method 5
2 Conclusions 7
2.1 Inspection Techniques 7
2.2 Upgrading Techniques 7
2.3 Vendors 8
3 Recommendations 9
4 Inspection/Assessment Technologies 11
4.1 General Requirements for Three New Inspection Methods 11
4.2 Noninvasive Assessment (Corrosion Rate Modeling) 13
4.3 Robotic Ultrasonic Assessment 17
4.4 Internal Video Camera Assessment 21
4.5 Previously Described Methods 26
4.6 Outmoded Technologies 28
4.7 Emerging Technologies 28
5 Upgrading Techniques 34
5.1 Upgrade by Lining the Tank 34
5.2 Upgrading by Addition of Cathodic Protection (CP) 38
5.3 Updating with Lining and Cathodic Protection 44
5.4 Combinations 45
5.5 Emerging Technologies 46
5.6 Outmoded Methods 52
6 Bibliography 53
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Appendix—Vendors by Type of Method
Figures
1. Robotic Ultrasonic Inspection
2. Remote Video Inspection ...
3. Thermal Wave Images
18
22
30
VI
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Acknowledgments
Many people contributed to the study reported in this document. In particular the authors
would like to thank the vendors of tank inspection methods for helpful descriptions of how their
particular methods work and the applicability of the methods. The vendors of the various tank
upgrading methods were also very helpful in providing information on how each upgrading
system is applied. Carolyn Esposito was the EPA Work Assignment Manager. Anthony Tafuri
and Robert Hillger of EPA NRMRL, and Randy Nelson of EPA Region VIE provided technical
assistance. Jan Martin (Work Assignment Leader) and Robert Amick (Project Director) of IT
Corporation provided project management oversight and technical assistance.
vu
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List of Abbreviations
AC Alternating current
API American Petroleum Institute
ASME American Society of Mechanical Engineers
ASTM American Society for Testing and Materials
CFR Code of Federal Regulations
CP Cathodic protection
DC Direct current
EPA Environmental Protection Agency
ES Emergency Standard
FRP Fiberglass-reinforced plastic
JR. Voltage drop, when used in conjunction with the word, "drop'
mV millivolt
MQ Megohm
NACE National Association of Corrosion Engineers
NLPA National Leak Prevention Association
OSHA Occupational Safety and Health Administration
pH A measure of acidity or alkalinity
RP Recommended Practice
SOTA State-of-the-art (report)
UL Underwriters Laboratories
viii
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UST
Underground storage tank
IX
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Section 1
Introduction
1,1 Background
Underground storage tank (UST) systems have been identified by the United States
Environmental Protection Association (EPA) as a significant source of contamination that impacts
soils and groundwater. The EPA promulgated regulations for UST systems that became effective
in December 1988.(1) These regulations include provisions for monitoring UST systems for leaks
as well establishing standards for new tanks. As part of the phase-in of these regulations, all
existing USTs must be upgraded to meet new tank standards, replaced, or closed by December
1998. Prior to upgrading an existing UST an assessment is necessary to verify that its condition
warrants upgrading.
The Federal Regulations(1) state that steel underground storage tanks must be upgraded by
one of the following methods: (a) internal lining, (b) cathodic protection, or © internal lining
combined with cathodic protection. In addition, any metal piping connected to the tank that
routinely contains regulated substances and is in contact with the ground must be cathodically
protected. Under most circumstances, the tank must have spill and overfill prevention equipment
installed. The new tank standards in the underground storage tank regulations (40CFR Part 280
Subpart B, 280.20(a)) require that:
(a) "Tanks. Each tank must be properly designed and constructed and any portion
underground that routinely contains product must be protected from corrosion, in accordance
with a code of practice developed by a nationally recognized association or independent
testing laboratory as specified below:
(1) The tank is constructed of fiberglass-reinforced plastic; or
(2) The tank is constructed of steel and cathodically protected..."
There are three other alternatives in the regulations that apply in special cases. In addition,
the piping must be protected from corrosion, and in most cases the tank must be equipped with
spill and overfill prevention devices. These requirements imply that only steel tanks need to be
upgraded with corrosion protection (although FRP tanks might be repaired under some
circumstances). Consequently most of the methods described in this report are designed primarily
for assessment of steel tanks prior to upgrading. When a method is also intended for use on FRP
tanks, it will be explicitly noted.
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The requirements for the assessment of a tank prior to upgrading depend on the method of
upgrading that is to be used. Three methods of upgrading tanks are listed in the regulations:
upgrading by addition of cathodic protection, upgrading by internal lining, and combining
cathodic protection and internal lining.
At the tune that the regulations were written, lining a tank referred to application of a
protective material directly to the interior tank surface. Such compounds are typically based on
an epoxy or an isophthalic resin, and are required to be nominally one-eighth inch (0.125 inch)
thick. Since the regulations were written, additional approaches to upgrading have been proposed
by the industry. However, these alternatives have not been recognized as approaches to
upgrading USTs as of this date. One approach involves installation of an internal flexible
membrane liner with an interstitial space between the liner and the tank shell. Another method
involves installation of a rigid internal liner, also providing an interstitial space. Each of these
three methods of tank lining are described in this report. The language of the report follows
industry practice in referring to lining a tank as meaning application of a compound that adheres
to the internal tank surface and that cures in place. The compound that is applied is referred to as
the lining, while a flexible or rigid internal membrane or liner is referred to as a liner.
EPA regulations for upgrading an existing steel tank by cathodic protection require that the
integrity of the tank be ensured prior to upgrading. Inspection methods listed in the regulations
used to meet this requirement are given in consensus standard documents such as American
Petroleum Institute (API) 1631(8) and National Leak Prevention Association (NLPA) 631.(9)
Additionally, some states such as California, specify additional inspection requirements that must
be met to qualify a tank for upgrading in that state.
Upgrading a tank by lining also requires an internal inspection. However, the criteria for
approving a tank for lining differ from those for cathodic protection. Requirements for upgrading
a tank by lining the tank are given in consensus standards such as API 1631 and NLPA 631.
If in the future, upgrading a tank by installation of a flexible membrane liner or a rigid liner
system is accepted by EPA these methods also would require a tank inspection. Since these
methods are currently being developed and the rigid liner is just reaching the market, there are no
national consensus standards for these requirements.
In general, external inspection of an underground tank is not possible without excavation.
Tanks that are below grade, but that are contained in an accessible vault and that can be inspected
visually are not considered to be underground tanks. If a tank is equipped with a manway, manual
internal inspections may be performed. Even if a tank is not equipped with a manway, it may be
possible to cut an opening in the tank to allow access for internal inspection. A manway can then
be installed or the opening in the tank may be closed permanently after the inspection.
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Internal inspections have been used for many years prior to upgrading a tank by lining or
adding cathodic protection. However, this method is inherently dangerous. The interior of any
UST is a confined space, requiring that any person entering the tank have special safety training
and equipment and follow OSHA requirements for entering confined spaces. Prior to entry, the
contents of the tank must first be removed and the tank must then be purged of hazardous gases.
The atmosphere in the tank must be monitored for breathability and combustibility. The inherent
hazards and the difficulty of conducting manual internal inspections make this process both time
consuming and expensive. As a consequence, a number of companies have developed alternative
methods of inspecting USTs that do not require human entry into the tank. Three such methods
have been recognized by the American Society for Testing and Materials (ASTM) in an
Emergency Standard, ES 40-94(2), which describes minimum requirements for conducting these
different types of inspections to qualify a steel tank for the addition of cathodic protection.
Although internal inspections have been used for some time to assess the condition of USTs,
there has been no definitive study of the effectiveness of these inspections. Since only the interior
of the tank can be observed, occasional isolated corrosion pits on the exterior that are deep but
that do not perforate the tank shell would be difficult to detect. Thus, while internal inspections
can effectively detect perforations and significant internal corrosion, the actual condition of tanks
that pass an internal inspection may vary considerably. Concerns exist as to whether the recently
developed inspection methods perform as well as a standard internal inspection.
EPA's National Risk Management Research Laboratory sponsored this project to identify,
catalog, and characterize procedures and equipment used for assessments of USTs. This
document represents a supplement to the previous EPA publication titled "State-of-the-Art
Procedures and Equipment for Internal Inspection of Underground Storage Tanks," January 1991
(EPA/600/2-90/061).(14) It focuses on new methods or changes that have developed since the
publication of the previous document. Existing procedures that remain essentially unchanged
from the description provided in the earlier document are not discussed in detail herein.
Additionally, this report describes the procedures and methods that can be used for upgrading
existing tanks. These procedures are identified and characterized, however a comparison of
methods is not provided. This information is intended to serve as a broad review of current
practices and emerging technologies rather than a detailed evaluation of specific approaches.
1.2 Purpose
The purpose of this report is to provide a compilation and engineering analysis of the
currently available methods for inspecting and upgrading USTs. This document builds upon
EPA's previous SOTA report (EPA/600/2-90/061)(14) but does not reproduce information
contained in that report. The focus of the current effort is on technologies developed or
significantly modified or adapted since 1991. Although the assessment relies on vendor supplied
information, an independent qualitative evaluation of the technologies has been made.
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Subsequent phases of this evaluation will include side-by-side comparative tests conducted on
actual USTs. This field effort was recently completed and is documented in a separate project
report.
1.3 Approach
The research effort documented herein was based on a review of available information
obtained from the literature and directly from vendors. Conversations with manufacturers and
vendors, representatives of trade and professional associations, and independent consultants were
conducted to ensure that the information was current and accurate. To facilitate this effort, a
"sources sought" announcement was published in the Commerce Business Daily and articles were
published in a number of trade journals. These notices were intended to make the industry aware
of this ongoing assessment so that newly developed methods for tank inspection and upgrading
would be identified.
1.4 Selecting an Inspection/Assessment Technology
Before selecting an inspection/assessment technology, the tank owner should check with the
state and local regulators to determine the regulatory requirements in their area. Some states, for
example Kansas and Colorado, accept a visual internal inspection as sufficient testing prior to
upgrading. Others (e.g., California) require an ultrasonic survey of the tank with wall thickness
measurements at least every square foot. The tank owner should check with contractors who do
inspections to ensure that the proposed inspection technology will meet the local regulatory
requirements.
Currently, internal inspection by a trained technician is the accepted standard method of
assessing a tank's condition prior to upgrading. The most basic form of this is the visual
inspection, coupled with hammer testing of any suspect areas. This is also the least expensive
inspection/assessment method. An ultrasonic survey conducted in addition to a visual inspection
adds information about the thickness of the remaining wall and is required in some jurisdictions.
The type of upgrade being considered for a tank is an important consideration in selecting an
inspection/assessment technology. If the tank is to be lined, it must be cleaned, entered, and
abrasively blasted in preparation for lining. In this case, an internal inspection might be the most
cost effective type of inspection. However, if upgrading by adding cathodic protection is planned,
one of the new methods described herein might be more cost effective.
In the future, if upgrading by installation of a flexible membrane liner or a rigid liner is
allowed, the tank must be cleaned and entered. In this case, an internal inspection might be the
preferred choice. If these upgrade methods become accepted, consensus standards that specify
the degree and type of inspection needed will be required.
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Three new methods for assessing a steel tank prior to the addition of cathodic protection
have been recognized by the ASTM in an emergency standard practice.(2) These methods have
advantages over the standard internal inspection as they do not require human entry into the tank
and presumably are less expensive. However, the tank owner should check with the appropriate
regulatory agency to determine the acceptability of these methods. For the most part, these
methods would not be applicable if lining is the intended method of upgrade, because the
necessary tank preparation effort would make an internal inspection the preferred choice.
Remote video inspection techniques do not require confined space entry and provide a
permanent video record of the inspection. It should also be less expensive than an internal
inspection. If the video identifies serious problems with the integrity of the tank, it might indicate
that the tank should be replaced and avoid an internal inspection. If lining the tank is the method
of upgrading that is planned, the remote video would only seem useful as a screening method,
since the tank must be cleaned and prepared for lining, which would allow for an internal
inspection at little additional cost or effort. If cathodic protection is the intended upgrade
method, the remote video inspection might be the preferred choice. Independent information on
the performance of this method is still being developed.
The non-invasive statistical modelling method of assessment has the advantage that it does
not require tank entry and does not take the tank out of service during testing. The use of this
method is associated with upgrading by the addition of cathodic protection. It would not be
useful for tank lining. However, it could serve as a screening method, if the results indicate that
the tank is not suitable for upgrading with cathodic protection, but might be suitable for lining.
Robotic, ultrasonic tank survey is an innovative means of tank inspection/ assessment. When
fully developed, it will not be necessary to remove product from the tank, therefore, it will have
the advantage of less effort for preparation than would be required for the remote video or
internal inspection. It also offers an advantage in that wall thickness measurements would be
determined over a substantial portion (15%) of the tank surface, increasing the probability of
detecting thin areas caused by pitting.
1.5 Selecting an Upgrading Method
The first consideration in selecting an upgrading method is to make sure that the method
meets all regulatory requirements. Requirements are generally set by the state in compliance with
the federal regulations(1), however, some localities, counties or cities impose additional
requirements.
The second consideration is the length of remaining service life planned for the tank. If the
upgrade is contemplated as a temporary measure intended to last only a few years, the cost of the
upgrade may be the primary consideration. However, if the intent is for continued use of the tank
indefinitely, then the life span of the upgrade should be the primary consideration.
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The results of the inspection of the tank may imply that only some methods of upgrade are
feasible. For example, the presence of corrosion holes (perforations) that must be repaired would
imply that cathodic protection alone could not be used. However, the tank could be lined, or a
combination of lining and cathodic protection might be applicable.
Cathodic protection alone is probably the least expensive upgrading method. However, for
tanks less than 10 years old a tank tightness test is required before upgrading with cathodic
protection and six months after the addition of cathodic protection to confirm that the tank is still
tight. Periodic monitoring of the cathodic protection system must also be conducted to ensure
that it remains functional. For a sound tank cathodic protection may be the method of choice,
particularly if the environment is not particularly corrosive. (Cathodic protection of the exterior
of the tank does not prevent corrosion inside the tank.)
Lining a tank is the only allowable method for use in tanks that have corrosion holes. Tank
lining generally provides a minimum 10 year extension to the service life of the tank. After 10
years, the lined tank must be inspected. If the lined tank is structurally sound and the lining still
meets original design specifications, the tank may continue in service with additional inspections
required every five years. (Interior lining does not protect the exterior of the tank from
corrosion.)
If the tank was found to have some corrosion, the addition of cathodic protection as well as
lining may be the method of choice. The cathodic protection protects the exterior of the tank
from corrosion, while the lining protects the ulterior and provides a layer of protection against
perforation by corrosion. This method is obviously more expensive than either lining or cathodic
protection alone, but provides additional protection.
Installation of either a flexible or rigid membrane liner converts a single wall tank into a
double containment tank. These methods are relatively new in the United States and there is little
experience with them to date in the industry. These methods might reasonably be combined with
cathodic protection of the tank shell to extend the life of the outer wall. Since these methods are
not explicitly mentioned in the federal regulations, the tank owner should check with the
regulating agency during evaluation of potential methods for upgrading tanks.
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Section 2
Conclusions
2.1 Inspection Techniques
The review of the state of the art identified three new techniques for inspecting steel tanks to
determine their suitability for upgrading by the addition of cathodic protection: noninvasive
statistical modelling; observation by remotely operated video camera; and robotic ultrasonic
testing. Each of these techniques has been developed since the EPA's previous SOTA report.
Standard requirements for each method are described in ASTM Emergency Standard Practice,
ASTM ES 40-94.(2) Additionally, one emerging tank inspection technology also was identified.
This method uses thermography and thermal waving to form an image of the tank shell which
shows exterior pits as light areas. The method requires further development to translate the
imaging technology into an inspection procedure that can be used on a routine or commercial
basis. Standards for thermal wave inspections have not yet been written.
2.2 Upgrading Techniques
Tank lining and the addition of cathodic protection are two standard upgrading techniques
that have been in use for many years. Tank lining consists of preparing the internal surface of the
tank and then applying a material that adheres directly to the interior surface. A nominal thickness
of 0.125 inch is typically used. Cathodic protection added to a steel tank can protect the outer
shell from corrosion by applying an electrical current to impede the corrosion process.
Combination of both tank lining and the addition of cathodic protection is also used in the
industry. A number of consensus standards exist for each type of upgrade; however, a separate
standard for their combination has not been published.
In addition to these standard methods, two additional methods which are not used extensively
in the United States were identified. A flexible membrane liner can be installed in a tank to
provide primary containment for the product. In this technology, the original tank shell provides
secondary containment. The interstitial space between the liner and the tank is monitored to
ensure the integrity of the liner and the shell. A second innovative method is the installation of a
rigid tank liner in an existing tank, converting the tank to a double-walled tank. Two separate
processes were identified for installation of rigid liners. In either case, the result is essentially a
fiberglass tank installed within the existing tank. The interstitial space can be monitored to ensure
the integrity of both walls of the resulting double-walled tank. To date, there are no U.S. industry
consensus standards or practices for the installation of these liners.
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2.3 Vendors
There are several vendors who supply tank assessment and/or tank upgrading services. Most
of these vendors offer a variety of inspection options and a variety of upgrading options, rather
than a single technology. Listings of vendors, classified by service type, were published in the
March 1996 issue of National Petroleum News.(lS)
A number of vendors were identified and contacted as part of this study. A list of these
vendors is provided in the Appendix, classified by type of inspection or type of upgrade. This list
is provided to identify sources of information for the current study and is not a complete list of
vendors. The list includes all respondents to the news items about the project or the Commerce
Business Daily announcement. No endorsement of any company, product, or service on this list
is intended or implied by their inclusion.
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Section 3
Recommendations
The performance of tank inspection techniques should be investigated to determine their
accuracy and effectiveness in assessing the condition of tanks for upgrading. This includes the
standard internal inspection techniques as well as the more recently developed procedures.
Although there is a substantial history for the internal inspection method, there has been no
independent evaluation of this technique. While such methods should be able to identify
perforations in the tank shell as well as evidence of internal corrosion, their ability to identify
external corrosion is less certain.
An impartial assessment of the performance of each of the inspection methods would be
valuable for both regulators and tank owners. An approach to such a study would involve
application of each inspection method to a tank. Subsequently, the tank would be excavated to
determine its actual condition. Testing of several tanks in different environments should be
included.
Upgrading methods of internal lining and addition of cathodic protection have been in general
use for some time. Upgrading of tanks by these methods has accelerated since the effective date
of the EPA's UST regulations in December, 1988. However, information as to the effectiveness
of these upgrades over long time periods is limited. A study to document the effectiveness of the
these techniques for upgrading tanks would be beneficial in establishing how long they extend the
service life of the tanks. This knowledge would benefit regulators, tank owners, and vendors.
Current regulations require inspection of internal linings after 10 years and periodic
inspections of cathodic protection systems to document that the systems are functioning properly.
These requirements, together with the leak detection requirements for USTs suggest that data
should be available to estimate the effectiveness of the standard upgrading methods. A data base
could be assembled from state records, documenting the dates when tanks were upgraded by
either method. If any of the tanks failed a leak detection test, that fact should be reported to the
state regulatory agency. Occurrence of a leak, together with the time since the tank was
upgraded could be used as part of the information used to estimate the effective life of the
upgrade. Similarly documentation that a tank was leak-free at certain times after the upgrade
would provide historical evidence of successful upgrade performance. Together, these existing
data should provide a base for estimation of the service life of lining, cathodic protection, or both.
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A similar study of the innovative techniques also should be initiated. Since there are few
tanks in the U.S. that have been upgraded by these methods, such a study would take longer to
generate sufficient data to estimate the service life of these upgrades. However, before these
systems are accepted for general upgrading, some evidence of their service life should be
documented. One approach would be to approve the use of these methods contingent upon
reporting of periodic leak detection tests. Because leak detection is required as part of UST
regulations, the data should be readily available. These data could then be used to estimate the
functional life of the methods.
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Section 4
Inspection/Assessment Technologies
Methods for assessing a steel tank for suitability for upgrading with cathodic protection are
described in this section. General inspection requirements are described in Section 4.1 and the
three newly developed methods are described in Sections 4.2, 4.3, and 4.4. Previously developed
and existing methods are listed in Section 4.5, along with references to the earlier SOTA
document, or updates where appropriate. Section 4.6 lists outmoded methods and Section 4.7
describes two emerging technologies.
4.1 General Requirements for Three New Assessment Methods
Three new assessment methods are described in the ASTM Emergency Standard Practice
ES 40-94.(2) These are: non-invasive statistical modelling; remotely operated video camera; and a
robotic ultrasonic method. The ASTM requirements specified in ASTM ES 40-94(2) include a
three phase approach for each of these newly developed methods as is described below.
Phase I is common to all three of the methods and consists of a preliminary survey to
determine the physical characteristics of the tanks and the operational characteristics employed by
the owner or operator of the tanks. As part of this phase, the tank must be assessed by one of the
leak detection methods in accordance with ASTM Practice E 1430 or a method that has been
certified in accordance with EPA requirements to establish that the tank is not leaking. However,
there are a number of sources of interference that could lead to a tank passing the leak test even
though there are some pinhole perforations. For example, a perforation might be filled with
corrosion product and not leak under the conditions of the test. If the tank fails the leak test, then
the tank is not considered suitable for upgrading with cathodic protection (unless some repair is
done). This phase also includes collection of some basic site information regarding stray DC
current sources, existing cathodic protection systems, and adjacent subsurface metallic structures.
The requirements for data collected as part of Phase I, the preliminary site survey that is common
to all three methods, are as follows.
• Leak Test
The tank or tanks must be assessed to establish that they are not leaking using a method that
has been certified in accordance with Federal EPA requirements or using ASTM Practice E
1430.
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• Facility Information
Basic facility information must be recorded, including:
—Address of the location
—Name and telephone number of owner and operator contact personnel
—Names and telephone numbers of site contact personnel
• Tank and piping information
—Number of tanks and capacity
—Location of tanks and dimensions
—Age of tanks
—Material of construction
—Electrical isolation
—Type of product stored
—Backfill material
—Coatings and linings (whether present and type of material)
—Leak history
—Repair history
—Site plans
—Installation specifications
—Tank excavation liners
—As-built drawings
• Other site-specific information
The presence of the following items should be investigated.
—Stray DC current sources
—Existing cathodic protection systems (and current functional status)
—Steel product and vent piping and fittings
<—Adjacent subsurface metallic structures and/or steel-reinforced concrete structures
Phase n consists of the in-field data gathering necessary to evaluate the integrity of each
tank. This phase is specific to each method, but includes data collection and analysis of soil
samples, along with other method-specific data, to determine the suitability of the tank for
upgrading by cathodic protection.
Phase HI involves data analysis and preparation of tank-specific recommendations based on
the data obtained in the first two phases. A report is prepared that identifies conclusions
regarding the suitability of each tank for upgrading by cathodic protection.
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All three methods also include characterization of the site and tank to determine the
requirements for cathodic protection. Soil sampling to define soil resistivity, pH, sulfide and
chloride ions, etc., is required. This information, coupled with the size of the tank, presence of
any coatings, and the structure-to-soil potential would be used to determine the requirements of
the cathodic protection system. (Additional information about cathodic protection is contained in
Section 5.2.)
4.2 Noninvasive Assessment (Corrosion Rate Modeling)
Noninvasive assessments can be conducted without interfering with normal tank operations.
Generally, nothing is inserted into the tank with the exception of a gauge stick that is used to
measure the diameter of the tank. A number of site-specific measurements are made at the site
and the data are assessed using a statistical model. To be valid, the model must have been
developed based on a large data base (a minimum of 200 tanks at a minimum of 100 sites). The
estimated service life as determined by the model is compared to the age of the tank and a
recommendation is made about the suitability of the tank and site for upgrading by cathodic
protection.
There are at least four independent companies that currently provide the statistical modeling
inspection services. Some of these have branch offices in several locations to provide the on-site
work. A number of other companies are considering adding this method to the services that they
provide.
4.2.1 Fundamental Principles of Operation
This method of assessment involves acquisition of soil and site measurement data beyond
those required to design a cathodic protection system. The additional measurements are used as
inputs to a statistical model which predicts the rate of corrosion and therefore the remaining
useful tank life. The data are used to predict the length of time from installation until a corrosion
perforation in the tank would be expected. The model provides a predicted tank life and a
probability that the tank is leaking (or has a corrosion perforation) as a function of the age of the
tank. The results of the model are then combined with the age of the tank to project the
remaining useful tank life and confidence limits. A probability of perforation is also estimated.
The exact form of the statistical model varies by vendor. The models were developed by taking
soil measurements at a large number of sites where tanks were excavated. The soil data base, the
physical condition of the tank, and the site-specific measurements were used to develop a
predictive model.
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4.2.2 Procedure Description
Several data collection activities are required by this method. These are grouped by type of
data and discussed below.
Stray Currents. A stray DC earth current monitor is established to detect the presence of
DC interference currents from foreign sources. Measurements of the structure-to-electrolyte
potential (voltage) are taken at least every 5 seconds throughout the duration of the field
investigation or for 30 minutes, whichever is greater.
Tank Information. Detailed tank information is required including:
(1) The location and material of construction for all tanks. (Only steel tanks are of interest
for cathodic protection.) The capacity, dimensions, and location of each tank must be
recorded.
(2) The presence and extent of any internal corrosion immediately below the fill riser. This is
determined using a test probe with a mechanical sensor tip. This is similar to using a gauge
stick to measure the product depth and does not interfere with normal operation of the tank.
Climate Information. Site-specific information including average annual precipitation and
mean temperature is obtained for the site and recorded.
Bore Hole Tests. The required soil data are obtained from soil samples taken from bore
holes.
(1) Soil borings are taken from at least two test holes for each tank. In the case where there
are more than four tanks, one additional bore hole is required for each two additional tanks
(i.e., one additional hole for five or six tanks, two additional holes for seven or eight tanks,
etc.) The location of these holes is identified on a site plan that includes the location of the
tanks and other structures. The two test holes should be located diagonally across the
excavation zone from each other, if feasible. The holes must be bored to the bottom level of
the deepest tank.
(2) Several measurements are required at each boring. The following measurements must be
made at 2-foot intervals: (a) electrical-resistivity measurements using an AC impedance
meter with a calibrated single probe test rod; (b) structure-to-soil potential measurements
using a minimum 10-MQ input impedance digital voltmeter and a calibrated copper-copper
sulfate reference electrode.
(3) The depth of any observed, perched, or static water table in each hole is to be recorded,
if encountered.
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(4) One soil sample at the top, mid-depth, and at the bottom of each hole is required. These
are sealed in sample containers for laboratory analysis.
(5) Each hole is backfilled and sealed with a concrete or asphalt plug.
Laboratory Testing Procedures. The soil samples are sent to a qualified soil laboratory and
tested in accordance with recognized industry standards. At a minimum the following data are
required:
soil resistivity/conductivity
moisture content
soil pH
chloride ion concentration
sulfide ion concentration
Additional data may be obtained from the soil samples. These data may be required by
specific methods, and include:
total hydrocarbon concentration in the soil
age of petroleum hydrocarbons
redox potential
sulfate ion concentration
soil classification (percent of sand, silt, and clay)
Atterberg limit tests (liquid limit, plastic limit)
microorganisms
Once the data have been obtained, Phase HI is conducted including the data analysis and
reporting. The data analysis is performed to determine the suitability of the tank for upgrading
with cathodic protection. The environment in the specific vicinity of the tank is used to establish a
relationship between the aggressiveness of the environment and the rate of corrosion by using a
statistical model. The model must be based on a data base sufficiently large and detailed enough
so that a confidence level of 0.99 can be used. A minimum of 100 sites and at least 200 tanks is
required by the ASTM emergency standard.
The mathematical formulation of the model must conform to accepted physical and
electrochemical characteristics of the tank corrosion process. The standard deviation of the
estimated time to corrosion failure must be no more than ±1.5 years and the model must generate
a probability of corrosion failure based upon a comparison of the actual tank age to the expected
leak-free life.
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4.2.3 Equipment
Much of the data for this method is obtained by laboratory analyses of soil samples. Standard
equipment is used for laboratory tests and for collecting and shipping the soil samples and making
the electrical measurements on site. Many of the electrical measurements are those needed by the
corrosion specialist to determine if the site is suitable for cathodic protection and if so to design
the cathodic protection system.
A 4-inch hand or power soil auger is used to obtain the soil samples. In addition, a power
drill is usually needed to drill through the paving material.
A sufficient number of 16 ounce sample containers (a minimum of eight) with screw-on lids is
required. Each sample container should be uniquely identified by an adhesive label (on the
container, not the lid) that identifies the site number, core number, and sample number.
Clean, inert sand is needed to refill each core hole. Some "cold patch" or concrete is needed
to seal the tops of the holes and patch pavement.
A three- or four-page survey and report is prepared for each location. This report shows the
location of the tanks, the soil borings, and records the measurements made on site.
Equipment needed to make the electrical measurements at the site includes a minimum 10-
MQ input impedance digital voltmeter and a calibrated copper-copper sulfate half cell. Equipment
to measure the soil resistivity using either the Wenner 4-pin or single-probe method according to
Appendix B of NACE RP0285 is needed.
4.2.4 Method Performance
Independent documentation of the performance of this method is not currently available.
Three companies who supply the service were contacted and indicated that the accuracy of the
method is between 95 and 99 percent. This claimed accuracy is said to be based on tank removals
and physical examination subsequent to applying the method.
4.2.5 Field Considerations
The staff who collect the field data must be competent in taking and handling soil samples.
This includes determining whether there is any observable water table in the soil boring holes. In
addition, the staff must be capable of making the soil resistivity measurements, as well as various
structure-to-soil potential (voltage) measurements.
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4.2.6 Cost
The cost of this service varies by vendor. Based on discussions with two vendors, the cost
ranges from $700 to $2,000 per tank. One company reported that the cost of their assessment
ranges from $700 to $900 per tank. The variation is attributed to site-specific conditions, size of
the tank, and number of tanks at the site. The process requires about one day on site, plus an
additional three days to complete the analysis and report. A second company reported a cost
range of $1,200 to $2000 per site. In general, this type of assessment requires two or three
persons on site for one-half to a foil day, followed by data analysis and reporting. This testing is
nonintrusive (in terms of the tank) and does not interrupt the normal operations. Based on the
information obtained, the cost for a site with three 10,000 gallon tanks would range from $1,700
to $2,700.
A tank tightness test is required. The cost of this test is not included in the cost estimates
presented above. If the test results are not available from leak detection records, this testing
would be an additional cost of approximately $500 per tank.
4.3 Robotic Ultrasonic Assessment
A robotic ultrasonic assessment involves the use of a remotely controlled ultrasonic
transponder. Assuming that the results of the site assessment indicate that the tank is a suitable
candidate for upgrading with cathodic protection (including passing a tank tightness test), this
invasive procedure of robotic ultrasonic assessment would proceed. The process involves
insertion of a robot through a 4-inch opening in the tank (typically the fill pipe). The system is
then used to conduct an ultrasonic survey of the interior walls of the tank (Figure 1, provided by
Red Zone Robotics).
The robotic ultrasonic inspection method is being developed by one company. Their stated
intention is to manufacture the equipment and sell it to service companies to provide the
inspections.
4.3.1 Fundamental Principles of Operation
This method uses remotely controlled ultrasonic testing to measure the thickness of the tank
wall at discrete points. In this regard, it is similar to manual ultrasonic testing. During this
process the wall thickness measurements and location information are stored automatically in a
computer file. This information is then reviewed (along with other information) by a corrosion
specialist to draw conclusions about the condition of the
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Figure 1. Robotic Ultrasonic Inspection
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tank. Another distinction between this method and standard ultrasonic inspection is that thickness
measurement readings are required from a larger portion of the interior surface of the tank. The
ASTM standard states: "The ultrasonic equipment used in the robotic inspection of the tanks
shall take discrete, located measurements on at least 15% of the entire tank interior surface,
excluding manways." Thus, the number of readings and amount of surface measured are
substantially greater than with manual ultrasonic inspection which requires one measurement on
each 3 foot by 3 foot section. (California requires one measurement on each square foot.)
Detailed requirements for this technology are defined in ASTM ES 40-94.(2)
4.3.2 Procedure Description
Safety precautions. Proper electrical grounding of the robotic inspection system is essential.
Pending certification of the equipment as intrinsically safe, with approval to operate in a
hazardous Class D environment, the tank must be emptied and incited to eliminate any
flammability or explosion hazard. The atmosphere inside the tank must be monitored throughout
the operation to ensure that this condition is maintained. Ultimately, the vendor intends to
develop the system so that the testing can be completed with the product remaining in the tank
(Figure 1).
Prepare the tank and insert transducer. This includes removing any adaptors and the drop
tube from the fill pipe and measuring the tank diameter. Also, the tank length must be determined
so that the required length of the tether guide can be calculated. The ultrasonic transducer is then
calibrated and inserted into the tank by placing it into the 4-inch riser and driving it partially down
the fill pipe. A launching rod, which is used to disengage the robot from the fill pipe, is positioned
on the rear of the robot and the robot is driven the rest of the way down the pipe. The robot is
then lowered into the tank, the launching rod removed, and the tether guide fed through the fill
pipe.
Conduct the inspection. The robot is driven to one end of the tank and positioned parallel
to the tank axis. The ultrasonic transducer scanning process is started and the robot is driven to
the other end of the tank. The operator monitors pitch, yaw, and roll readouts to ascertain that
the robot is on its intended path. The transducer is equipped with a bump sensor which, when
tripped, the odometer reading is compared with the tank length to determine if the robot has
reached the end of the tank or has encountered an obstruction. If an obstruction has been
encountered, the operator maneuvers the robot around the obstruction. When the robot reaches
the end of the tank, it is turned around and another traverse is conducted.
After the cylindrical walls of the tank have been tested, the robot is positioned on one endcap
and used to make measurements along a diameter. After scanning one diameter, the robot is
moved a short way around the circumference and driven along another diameter. The process is
then repeated on the other endcap. The track taken by the robot follows a zigzag or slalom route
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from endcap to endcap around the circumference of the tank and a starburst track on each
endcap.
Remove the system from the tank. After completing the scan, the robot is driven to a
position under the fill pipe. It is then removed from the tank by reversing the insertion process.
Once removed, the ultrasonic transducer is recalibrated and the documentation of the ultrasonic
inspection is completed.
4.3.3 Equipment
The equipment required consists of the robot equipped with an ultrasonic transducer
designed to measure the wall thickness of a steel tank. In addition, a data acquisition system is
connected to the robot via the tether cable and used to acquire the ultrasonic thickness data and
the position data. Equipment to control the robot and direct it to various positions in the tank is
part of the system, as are special tools to insert and extract the robot from the tank.
For the present, ancillary equipment is required to inert the tank and to monitor the tank
atmosphere to ensure safe operation. Eventually the vendor plans to offer an intrinsically safe
system than will be able to operate in a tank with the product in place, using the product as the
ultrasonic transducer couplant.
4.3.4 Method Performance
No field testing performance data are currently available.
4.3.5 Field Considerations
Currently the tank must first be emptied of product, then incited so that the equipment can be
safely used in the tank. Therefore, the tank must be taken out of service and the product moved
to another storage location. Depending upon the nature of the product, this transfer could present
significant difficulties and costs. The tank must be monitored continuously throughout the
inspection using an explosion meter to ensure that the inert atmosphere is maintained.
4.3.6 Cost
This method has not yet been applied in a commercial operation, therefore, no application
history or cost data exists. The developer intends to sell the equipment to vendors who will
perform the inspections. In commercial operation, the vendor envisions a system that can be
placed in a tank with the product in place, minimizing the disruption of the tank use. A single
operator would control the robot, requiring approudmately one day on site for a 10,000 gallon
tank. The cost for this inspection will vary by vendor and no dollar figures are currently available.
However, based on the level of effort required, it is expected to be less expensive than the current
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standard internal inspection (without ultrasonic testing). A tank tightness test would be
conducted prior to using this method of inspection. If results from previous tests are not available
from the leak detection requirements, the tank test would add approximately $500 per tank to the
inspection cost, depending on type of test and size of the tank.
4.4 internal Video Camera Assessment
Assessment of the internal condition of an UST using a video camera assessment method
avoids the necessity for a person to enter the tank. Since visual inspection is the most widely used
method of internal inspection, this method should accomplish the same goal. There are
advantages to using a remote video assessment in terms of safety, time, and cost. A schematic
drawing illustrating the application of the remote video inspection is shown in Figure 2.
However, with internal inspections, visually identified suspect areas such as ultrasonic, hammer
test, and magnetic flux measurements. This additional testing is not feasible with the video
camera method.
There are currently at least three separate companies that report using internal video camera
assessment as an inspection method. At least one additional company is in the process of adding
this method to its services. These companies include multiple branches or franchise holders, some
of which operate under different names.
This procedure is essentially a development of the boroscope technology mentioned in the
earlier SOTA as a developing technology in that it uses remote optical and video systems to
inspect the interior of the tank that is normally inaccessible. However, while the concept of using
a remote device for visual inspection was merely mentioned in the earlier document the remote
video inspection has now been developed to a commercially available service.
4.4.1 Fundamental Principles of Operation
Visual assessment using a remote video camera replaces the need for entry into the tank. It is
used to provide a visual image of the interior of the tank. Using the appropriate illumination,
camera direction, and zoom or interchangeable lenses, the visual images are displayed on a high
resolution television monitor. The operator views these images and interprets them in the same
manner that an inspector would perform a visual inspection of the tank interior. Thus, the
fundamental principle of operation is that of the internal visual inspection. The essential
difference is that the images are picked
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up with the video camera and displayed on a television screen instead of being observed directly.
The use of zoom or interchangeable lenses and the positioning of the camera direction replaces
the direct viewing of different parts of the tank by an inspector. A recording of the inspection is
made so that the inspection can be viewed by others or reviewed as needed. This is an
improvement over the visual inspection in that a record is provided that can be evaluated
independently.
4.4.2 Procedure Description
Prior to the video inspection, the tank must be emptied of all liquid product. Any residual
water, sludge, or other dense material must also be removed from the tank. The tank must then
be purged or inerted by replacing the atmosphere in the tank with an inert gas, typically carbon
dioxide. As the purging is carried out and during the inspection, the atmosphere in the tank is
monitored continuously using an intrinsically safe oxygen meter to ensure that the atmosphere is
inert and that it is safe to insert the video and lighting equipment into the tank.
The video equipment is designed to be inserted through an existing opening in the tank, such
as a fill pipe that has a minimum inside diameter of 2.5 inches. A rod apparatus that is designed to
allow the operator to swivel the camera 360 degrees in the horizontal plane and from directly
down to 135 degrees up from vertical holds the camera. The system is designed to allow the
camera to be raised or lowered over 95% of the tank diameter.
Once in place, the system is energized and its operation is checked. The lighting and lens
systems are adjusted to provide a clear image. Basic tank identification data are entered on the
video tape by the operator via a keyboard. These data include
• tank size and location
• tank owner and address
• tank age and any special considerations
• the date and time of the inspection
Additional data can be entered during the inspection as appropriate. These include the
position in the tank where the inspection was begun, the vertical and horizontal locations viewed,
and any unusual conditions or characteristics observed.
Voice-over comments can also be recorded on the videotape. These can include
identification of the tank, the vertical and horizontal locations, and comments on any unusual
conditions or characteristics observed. The end of the inspection is noted on both typed-in and
voice-over comments identifying the tank, date, etc., and stipulating the end of the inspection.
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The video tape is then viewed by a corrosion expert, who uses it along with the site
inspection data to make a determination as to the suitability of the tank for upgrading with
cathodic protection. The corrosion expert will identify active corrosion by visual evidence of:
• rust tuberculation—active dark red/maroon
• streaks—dark red-black at apex
• discoloration—patches showing dark reddish/black center, lighting toward edges, usually
irregular in shape, 3 to 9 inches in diameter
• pitting—black in center-bottom of crater, light red or bright metal near perimeter
• scaling or delaminations—typical exfoliation, no discoloration, layered flakes in small 2- to
4-inch diameter irregular patches
• weld decay—little discoloration, except possible black/maroon deposit beneath interface;
deterioration of metal within weld
• cracks—usually no discoloration; typically near welds, openings, fitting connections and
other stress or fatigue sites
• general overall rust film—light red, pink, or tan/beige; smooth to slightly pock-marked.
This is not active corrosion but an "alpha oxide" film which is protective or passivating.
In the event that the tank has been previously lined, the inspection can determine the
condition of the lining. In this case the corrosion expert will identify deteriorated lining by
evidence of:
• lining disbondment/peeling—portions of the lining disbonded and breaking free from the
tank walls
• cracking—cracking or fracturing of the lining material
• blistering—bulges that appear to be beneath the lining surface
• surface wrinkling—ridges or other uneven surface appearance
• surface roughening—a nonshiny or rough appearance of the lining surface
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The corrosion expert will prepare a report including the evidence from the remote video
internal inspection and the site inspection. A copy of the video tape would be included with the
written report.
4.4.3 Equipment
The primary equipment required is the remote controlled video camera equipped with zoom
or interchangeable lenses. In addition, lighting equipment is required to illuminate the interior of
the tank. Both the video equipment and lighting equipment must be mounted in such a way that
they can be rotated and used to scan the interior of the tank. In addition to the video pick up,
recording equipment is used outside of the tank. This equipment records the video images and
has the capacity to record both typed information as well as voice-over information. A high
resolution color video monitor is needed to observe the inspection in the field and to play back the
video record at a later date.
Detailed specifications for the pick-up, scanning, resolution, lighting, etc., are provided in the
emergency performance standard ASTM ES 40-94.(2)
Additional equipment is required to inert the tank and to monitor the tank atmosphere.
Typically this consists of compressed gas cylinders (i.e., carbon dioxide) and pressure regulators
together with oxygen monitors to determine the oxygen content of the tank atmosphere.
Additional equipment to conduct the site corrosion survey consists of the high impedance
voltmeters together with copper-copper sulfate reference half cells. This equipment is common to
all methods collecting the electrical measurement data needed for assessing the site for addition of
cathodic protection.
4.4.4 Method Performance
The ASTM ES 40-94 performance standard specifies that the equipment must be capable of
detecting a corrosion pit or tubercule that is 1/8 inch in diameter at the maximum distance from
the camera; typically up to 30 feet. Independent documented field experience regarding method
performance is not available.
4.4.5 Field Considerations
The field crew must ensure that the tank is properly emptied of liquid product and cleaned of
any remaining sludge that would interfere with the video inspection of the tank. This is not
considered by the vendor to be the responsibility of the video inspection crew. The video and
recording equipment must be designed to operate in the field environment. The recording
equipment must be protected and is usually located in a van.
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4.4.6 Cost
A video inspection can generally be completed by one person in about 6 hours if the tank has
been emptied prior to the arrival of the video inspection person or crew. The cost is estimated to
run from about $500 to about $650 per tank for tanks in the 10,000- to 20,000-gallon range. One
vendor estimated a cost of about $2,000 for testing three 10,000 gallon tanks at a single site.
Another vendor stated a cost of $500 per tank with a minimum $1,500 per site. Thus, a site with
three, 10,000 gallon tanks should range from $1,500 to $2,500. The cost of removing product
from the tank and subsequent refilling are not included in these estimates.
The cost of the site assessment to design the cathodic protection system is not included in this
cost estimate. A tank tightness test is also required. The cost of this test is not included in this
cost estimate, since those test results might be available from the leak detection required for the
tank. If the test results are not available, this would be an additional cost of approximately $500
per tank, depending on tank size and test method.
4.5 Previously Described Methods
A number of methods were described in EPA's previous SOT A. These methods are
identified below along with any available update information.
The following 12 inspection methods were listed in the previous SOTA as internal inspection
methods that were neither "outmoded" nor "emerging":
• Tank Wall Thickness
—Ultrasonic Testing
—Hammer Testing
• Tank Deflection
—Internal Tank Diameter
• Tank Lining Integrity
—Holiday Tests
—Dry Film Thickness Measurements
—Lining Hardness Tests
• Tank Integrity
—Bubble Testing
—Positive Pressure Testing
—Vacuum Tests
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• Tank Discontinuities
—Visual Examination
—Liquid Dye Penetrant
—Magnetic Particle Testing
Not all of these methods are used routinely; some are used more frequently than others, and
some are used only under special circumstances. Others are used rarely, if at all.
The most common inspection method currently in use is the visual examination. Probably all
tanks being considered for upgrading, whether by lining, cathodic protection, or by both, receive
an internal visual inspection unless other data rule out upgrading prior to opening and cleaning the
tank. For example, if a tank tightness test shows conclusively that the tank is leaking and that
clean-up is required, it is unlikely that the tank would be upgraded. Once the area has been
excavated to perform the clean-up, it is likely to be just as cost effective to remove the tank and
replace it with a new one. The method of visual inspection has not changed recently.
Visual inspection is sometimes augmented with ultrasonic and/or hammer testing, depending
on local regulations and on the method of upgrading being contemplated. These inspection
methods are described in API 1631 for lining a tank and in NLPA 631 (June 1995) for both lining
and addition of cathodic protection. Both of these methods are conducted in the manner as
described in the previous SOTA. (See consensus standards NLPA 631 and API 1631.)
If a tank is upgraded by application of a sprayed-on epoxy- or isophthalic polyester-based
resin system, the three tank lining integrity tests listed above are mandatory tests. Again, no
changes in their application have occurred.
The internal tank diameter test is limited, practically, to fiberglass (FRP) tanks. The
measurement technique remains the same.
The tank integrity tests listed are used in special situations. On occasion, a newly installed
tank may be pressure tested. A bubble test may be used after work has been performed on the
tank, for example, if a manway gasket has been replaced. Not listed above are annual tank
tightness tests and monthly tests using an automatic tank gauging system, which are now
commonplace, although they are not truly internal inspection methods (neither are the three listed
tank integrity tests).
The liquid dye penetrant test and the magnetic particle test, as implied in the previous SOTA,
had been widely used in various applications, but were not normally applied to USTs. That
situation has not changed.
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4.6 Outmoded Technologies
Several technologies have been identified that are seldom, if ever, used. The previous SOTA
identified radiography and eddy current tests as outmoded methods. Neither of these methods is
currently in regular use for testing underground storage tanks, although they may find applications
in other situations. Similarly, the liquid dye penetrant test and the magnetic particle test, though
not outmoded, continue to find applications elsewhere, but not in UST assessments.
4.7 Emerging Technologies
The previous SOTA identified three emerging technologies: acoustic emission, boroscope,
and microwave. To date, none of these has developed into a technology that has found
application in assessing suitability of USTs for upgrading. A possible exception to this might be
the boroscope in that the remotely operated video camera and recorder might be considered to be
an outgrowth of the general idea of a remote visual inspection. Acoustic emission technology is
still being developed for applications to detect or locate leaks, primarily from pressurized pipelines
containing liquids, but also in some applications involving aboveground storage tanks. However,
it has not emerged as a technology for assessing the structural integrity of an underground storage
tank.
Two new additional technologies were identified that are being developed or adapted to
assessment of USTs. These technologies are based on thermography or thermal imaging of a
surface and magnetic flux scanning for flaw detection.
4.7.1 Thermal Waving
4.7.1.1 Fundamental Principle of Operation
As currently being developed, thermal waving would be used as part of an internal inspection.
That is, the tank would have to be cleaned and prepared for a person to enter with the equipment.
This technology produces images of the tank's interior surface that are about 12 by 12 inches up
to 18 by 18 inches in size. A sufficient number of images would be taken to represent the interior
of the tank. The number of images and degree of coverage required remain to be determined.
Thermal waving imaging involves illuminating an area to be imaged with a flash or burst of
infra-red light or thermal energy. The infra-red energy penetrates the tank wall surface and is
partially reflected by the exterior of the tank wall. Different thickness of the tank reflect different
amounts of the incident thermal energy and appear as different shades of gray (or different colors
if the image is processed in false color).
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4.7.1.2 Procedure Description
Because this procedure is still under development, no complete description is available. The
procedure as currently envisioned would include preparation of the tank for a internal visual
inspection. A visual inspection of the tank interior would be carried out. If no holes or other
problems were found, thermal waving would then proceed. The equipment would be used to
form and record images of each section (approximately 1 to 2 square feet in area) of the tank.
These images would then be used to determine whether evidence of significant pitting or thin
areas on the exterior of the tank exists.
4.7.1.3 Equipment
The specific equipment needed for thermal waving includes a source of infra-red energy that
can be pulsed and an infra-red camera. A method of recording the images (for example, on video
tape) would be included as part of the camera system. A tripod would be used to set up the
camera and infra-red source. Each image would be identified on a reference grid of the interior of
the tank to allow identification of the location of any problem as well ensuring that adequate
coverage of the surface was obtained.
4.7.1.4 Method Performance
There is no field experience with this method, therefore, method performance is speculative
at this time. Figure 3 presents a reproduction of thermal waving images. These images were
made of three sections of an underground storage tank. These sections were approximately
1 foot square. The images were made from the interior (concave) side of the sections. A number
of features of the sections can be seen. Some had significant corrosion pits on the exterior
(convex) side of the section. These are apparent as white or light gray spots in the figures. The
general light areas identified as surface cracking were areas of internal corrosion. This method
appears capable of identifying significant pits on the exterior of the tank from the inside without
excavation and therefore offers a significant advance in the assessment of tank condition.
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Cutout # 17 - Concave side
hole —
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7
front
surface
cracking
deep
cracking
Single-side flash differential thermal wave images of the inner (concave) surface of a 12" X 12" section of
a 0.250" thick steel storage tank. Left: The early differential image indicates severe pitting on the outer
(convex) surface. Left: The later differential image shows extended areas (vertical stripes) of deep cracks.
Acquisition time for this image sequence was 20 seconds.
Figure 3. Thermal Wave Images
Reprinted from original source with permission of Thermal Wave Imaging, Inc.
Thermal Wave Imaging, Inc.
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4.7.1.5 Field Considerations
Because entry is required, all of the field considerations for a conventional internal
visual inspection would apply to this technology. This would include preparation of the
tank for human entry with all of the safety requirements for confined space entry. The time
required to complete a tank by this technology will be dependent upon the size of the tank
(i.e., the interior surface area), the number of images required, the size of the images, and
how quickly the images can be processed. For a 10,000 gallon tank the time required could
range from less than 2 to about 8 hours depending on the number of images requires.
If this method proves to be widely acceptable, the next logical step in its development
would be automation. Assuming that the infra-red camera and source can be made small
enough to be inserted into a tank through a 4-inch opening, the process could be
automated, and the images could be made via a remote camera without the need for a
person to enter the tank. This approach would be advantageous in reducing the cost and
risk involved. However, it would place additional requirements on the imaging system, as it
would have to function from a fixed location and produce acceptable images at varying
distances and angles.
4.7.1.6 Cost
The commercial cost for this procedure has yet to be established. Currently such
imaging would be available on a consultant basis at approximately $2,000 per day according
to one company involved in technology development. The cost for a tank test, if required,
would be additional. The site inspection for cathodic protection would also be an additional
cost.
4.7.2 Magnetic Flux Scanning
A second emerging technology is magnetic flux scanning for flaw detection. This
technology has been used to test the bottoms of aboveground storage tanks, and has been
used in Europe, but has only recently found applications in the U.S.
4.7.2.1 Fundamental Principle of Operation
The equipment for magnetic flux flaw detection consists of a hand operated scanner
and a console, with a cable connecting the two. The hand-operated scanner has rare earth
permanent magnets that induce a magnetic field as the unit is rolled over the steel surface.
There is a magnetic sensor between these magnets that measures the magnetic field
strength. The magnetic field induced by the permanent magnets is a function of the
magnetic properties and the thickness of the wall. A signal measuring the magnetic flux is
transmitted via the cable to the console. The system is calibrated for the material being
scanned and a threshold value entered on the console. For example, the console can be set
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to alarm at a fixed proportion of the wall thickness, e.g. 50 percent. When the scanning unit
is passed over an area with a flaw or reduced thickness, the console gives a visual and
audible alarm if the thickness is less than the adjustable threshold.
4.7.2.2 Procedure Description
An operator in the tank rolls the scanner along the tank walls in parallel strips. On the
end caps, the scanner may be rolled horizontally or vertically in strips. Each strip is adjacent
to the next for a 100 percent inspection, or a gap may be left for a 50 percent or less
complete inspection. Any flaws indicated are marked with chalk or a grease pencil. The
areas with flaws may be subsequently investigated with ultrasonic testing to measure the
actual wall thickness and to determine the extent of the flaw.
The method has the advantage of scanning about a 6-inch wide path on each pass. This
enables it to detect flaws or thin spots in the metal more rapidly than equipment which tests
a smaller area at a time.
4.7.2.3 Equipment
Equipment consists of a handscan battery powered unit with 6-inch wide path. This is
connected to a console with a cable. It induces magnetic fields and monitors for
discontinuity in flux which indicates a pit or thin spot. A flaw is indicated by an audible
signal and light at the preset threshold (e.g., 50 percent of wall thickness). The system is
precalibrated for magnetic permeability of the metal.
4.7.2.4 Method Performance
One unit, a US Stresstel J-MikeEL (TM) Serial 830082, was recently demonstrated
during a qualitative test. The system was demonstrated on a section of a steel tank with a
hole drilled part of the way through one side. The system identified the hole when operated
from the other side. It located the hole within a 6-inch diameter circle. Based on this
observation, it appears capable of detecting pits on the outside of a tank when operated
from the inside.
4.7.2.5 Field Considerations
The use of this technology currently requires that the tank be emptied, cleaned, purged,
and any loose scale or residue removed from the walls. This requires human entry into the
tank, and typically a degree of abrassive blasting to clean the tank. The degree of blasting
needed for inspection is much less than needed for lining preparation and a limited amount
of surface rust may not interfere with operation. While the use of this equipment is fairly
labor-intensive, it appears to take less time than an ultrasonic survey of the tank interior and
can provide more complete coverage.
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4.7.2.6 Cost
This technique would most likely be used in combination with or as part of an internal
inspection. Magnetic flux testing or a tank would take approximately half a day after the
tank has been prepared for entry and abrasively blasted to remove any loose scale (it does
not require a white metal blast).
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Section 5
Upgrading Techniques
This section describes techniques to upgrade a tank. Three such methods were
included in the EPA regulations: lining a tank, upgrading with cathodic protection, or both.
An additional method that has been developed since the regulations were written involves
installing a flexible membrane liner. In addition, combinations of these techniques can be
applied, for example a tank can be both lined and have cathodic protection. These methods
are described in Sections 5.1 to 5.3. Combinations are discussed in Section 5.4 and
emerging technologies still in the development stage are described in Section 5.5.
5.1 Upgrade by Lining the Tank
5.1.1 Fundamental Principles
The term tank lining has been accepted in the industry to mean applying a material that
adheres to the properly prepared interior tank surface. A lining system is distinguished from
flexible membrane liner systems in that it consists of applying a synthetic resin material
directly to the inside surfaces of the tank. The material cures in place and forms a strong
bond with the ulterior tank surface. When fully cured the material will have a nominal dry
film thickness of 0.125 inch.
In order for the lining method to be used, a tank must have adequate structural integrity
and its interior surface must be properly prepared. If these conditions are met, the tank may
be lined with a cure-in-place spray-applied synthetic resin system. Generally, linings are
applied to steel tanks, but the material can also be applied to fiberglass-reinforced plastic
(FKP) tanks.
Guidelines for tank inspection, tank repair (if needed), and interior lining of USTs are
provided by the American Petroleum Institute (API) Recommended Practice 1631(8) and by
the National Leak Prevention Association (NLP A) Standard 631 .{9) The inspection must
find the tank structurally sound. Some perforations are permitted, provided that these can
be repaired. For tanks 10 years old, the tank must not have any perforation greater than 1.5
inches in diameter, except that it may have a hole up to 2.5 inches in diameter below the fill
pipe. The tank may not have more than 5 perforations of 0.5 inch or less in diameter in any
one square foot area, nor more than 20 perforations of 0.5 inch or less in diameter in any
500 square foot area. The ulterior surface of the tank must be cleaned and generally blasted
with abrasives to white metal in order to provide a suitable anchor profile for the lining
material.
The cured resin system is commonly epoxy- or isophthalic polyester-based and must
demonstrate long-term chemical compatibility with the product to be stored. Federal
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standards permit this upgrading technique with or without cathodic protection applied to
the exterior surface of the (steel) tank.
The bonded lining imparts some structural integrity to the tank in that small tank
perforations (i.e., < 0.125 inch), either existing at the time of lining or developing due to
subsequent corrosion, will be bridged by the lining material.
5.1.2 Procedure Description
The lining material must be tested for product compatibility and other properties. The
tank must be inspected and repaired if needed. The tank's interior surface must be prepared.
The material is applied to the surface and allowed to cure. After curing, the material is
tested to ensure adequate bonding and minimum film thickness. The tank must be inspected
after 10 years and at subsequent system intervals.
5.1.2.1 Resin System Prequalification
Representative samples of lining materials are subjected to applicable ASTM or UL test
procedures to demonstrate product compatibility. The samples are subjected to long-term
immersion in the normally stored petroleum product, other hydrocarbons, and in distilled
water. After immersion, the samples are tested to demonstrate a sufficient level of bond
strength, and acceptable physical properties.
5.1.2.2 Tank Preparation
The tank preparation depends on the condition of the tank. For a tank that has
previously been in service, the tank must be emptied, any sludge must be removed, the tank
must be purged of vapor, cleaned, and abrasive blasted. These activities are conducted
according to recognized procedures (API 1631(8) or NLPA 631(9)) and in accordance with
confined space safety protocols. If the tank was not originally equipped with a manway, the
tank must be partially excavated and an opening cut in the tank. If a new tank is to be lined
prior to placing it into service, the steps associated with product removal are not needed.
However, abrasive blasting would still generally be required to clean any surface rust from
the tank interior and provide the necessary surface profile.
Once the tank has been prepared, it is inspected for holes, discontinuities, and wall
thickness. The walls may be further inspected by use of hammer testing, ultrasonic wall
thickness measurements, or other techniques, depending on the stipulations of the cognizant
regulating authority. Both API and NLPA provide guidelines for judging the acceptable
limits for size and number of tank perforations prior to interior lining, as well as allowable
wall thickness. Thin areas or perforations may be repaired by welding or plugging (NLPA
631).(9) Both API and NLPA require installation of a steel striker plate under the fill tube
and/or gauging port.
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5.1.2.3 Lining Application and Testing
After the interior of the tank has been prepared, the resin compounds are mixed and
applied according to the manufacturer's written protocol. The resin material is sprayed onto
the interior surfaces to a depth that will provide a nominal thickness of 0.125 inch with a
minimum thickness of 0.100 inch after the resin is cured. The resin must be applied within 8
hours after the abrasive blasting has been completed to avoid surface rusting that would
interfere with adhesion of the coating. The coating must also be applied within the
manufacturer's tolerances for ambient temperature and humidity and allowed to cure
according to the manufacturer's recommended time and temperature profile.
After thorough curing of the resin material, the lining is subjected to several tests
including:
a. a high vdtage electrical inspection (Holiday test) to locate coating discontinuities
or thin spots which can be repaired (usually by coating over them) according to
the resin supplier's instructions
b. a lining thickness test using a magnetic gauging instrument
c. a test for lining hardness (i.e., Barcol test)
d. a final tank tightness test of the system
Guidelines are provided in NLPA 631, 632, and API 1631 for closing the tank (covering the
opening or installing a manway or re-installing the manway cover).
5.1.2.4 Equipment
The lining application contractor will normally provide a "turn-key" operation including
several phases. These phases require a variety of equipment including:
a. tank excavation equipment when required because of the absence of a manway
b. a transfer pump for emptying the tank of product
c. purging and ventilation equipment
d. an air saw and drill for cutting a manway when required
e. desludging tools and sludge containers for removing sludge when cleaning the
tank
f. safety equipment including fresh air packs, safety lines, explosion-proof lights,
rescue airpacks, oxygen and explosive gas monitoring equipment
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g. fire extinguishers
h. tank inspection instruments such as brass hammers and an ultrasonic wall
thickness measuring device
I. abrasive blasting equipment and supplies including cleanup equipment and a
profilometer
j. resin, resin mixers, resin applicators, and resin cleanup materials
k. thermometers and humidity indicators
1. coating inspection devices including a high voltage holiday tester, film thickness
gauge, and a film hardness tester
m. tank tightness test equipment
n. materials and equipment for tank closing and backfilling the excavation
5.1.3 Method of Performance
A chemically cured resin lining forms an impermeable, noncorroding barrier between
the stored product and the backfill surrounding the buried tank. The steel tank shell
provides the main physical support for the barrier material.
After application of the lining and return of the tank to service, ongoing system
integrity must be monitored by an approved leak detection method. An inspection of the
lined tank is mandated after 10 years and at subsequent 5-year intervals to ensure that the
lined tank is structurally sound and that the lining still meets original design specifications.
5.1.4 Field Considerations
Because the lining application requires entry into the tank, all safety considerations
associated with tank excavation, evacuation, and internal inspection are applicable. This
includes confined space entry into a hazardous area. Additionally, epoxy, other synthetic
resin materials, and solvents for cleaning the equipment can have toxic effects and
appropriate precautions must be taken.
Other field considerations for lining applications include:
a. ensuring that an appropriate surface profile (anchor pattern) is provided by the
abrasive blasting operation
b. taking appropriate precautions for dealing with residuals from abrasive blasting
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c. applying the lining before the properly prepared steel surface can rust
d. ensuring acceptable ambient conditions at the time of the lining application
e. following the recommended cure schedule prior to testing the lining
f. taking care that the lining is not physically damaged prior to closing the tank
5.1.5 Cost
An approximate cost for a site with three 10,000 gallon steel tanks was estimated by
one vendor as $14,085 to inspect and line the three tanks. Another vendor estimated a cost
of $15,000 to $24,000, with $18,000 being the average estimated cost. The cost will vary
somewhat with location and with the contractor as well as the lining company. In addition,
lining requirements for special products might increase the cost. This price includes all
requirements for a "turn-key" operation including excavation, purging, and cutting an
access opening, cleaning, abrasive blasting, applying the lining, curing and testing, resealing
the tank and backfilling. The costs presented above do not include pumping product out to
empty the tank, repairing the pad over the tank, permits, special testing, oil-water
separation, mileage, per diem for the crew, tank bottom waste disposal, or damage caused
by accidental flotation of the tank.
Lining the tanks at a site generally requires a crew of three persons working at the site
for 1 week. Two or three tanks of about 10,000 gallons can be lined in this time. The
actual costs will vary with the lining company and material as well as the tank sizes.
Generally, lining a tank is estimated to cost form one-third to one-half as much as replacing
a tank.
5.2 Upgrading by Addition of Cathodic Protection (CP)
5.2.1 Fundamental Principles
Corrosion is generally defined as degradation of a material due to reaction with its
environment. Corrosion of buried steel (e.g. steel underground storage tanks) is generally
considered to be primarily due to galvanic action. Bare steel in contact with moist soils can
establish an electrochemical cell analogous to a battery. Some surface areas of a buried
steel tank can become negatively charged while other areas become positively charged.
These anode/cathode areas can, and do, move around on the tank. The moist soil serves as
an electrolyte allowing ions to move from one area to another. These oppositely charged
areas are metallically coupled though the tank shell, thereby completing a full electrical
circuit. Corrosion current flows due to the potential difference between these local action
electrodes. In this configuration, the positively charged areas (anodes) lose metal ions to
the electrolyte (soil) while the negatively charged areas (cathodes) attract metal ions. The
cathodes are thus protected from metallic dissolution.
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Corrosion occurs when electric current leaves the metal. This occurs when there is a
difference in electric potential between the tank and its surroundings, causing an electrical
current to flow from the tank (or a portion of the tank) to another structure or part of the
tank. The basic concept of cathodic protection is to eliminate corrosion of a metal by
reducing this potential difference to zero. Thus, the corrosion is stopped when the current
flow is reversed (cathodic protection). Cathodic protection can be effected by sacrificial
anodes or impressed current systems.
Sacrificial anode systems are established by placing pieces of another metal in the soil
adjacent to the metal (e.g. the tank or pipe) to be protected and attaching them to the metal
to be protected with a metallic lead (typically an insulated copper wire). The sacrificial
anode material is usually magnesium, aluminum, or zinc. These metals are more reactive
than the steel and, therefore, the electric current will exit from them rather than from the
tank. Because these metals are different from steel in the electromotive series, the
connection between them and the tank together with an electrolyte establishes an electric
cell with the tank being the cathode and the other metal becoming an anode. Metallic ions
leave the anode and migrate toward the cathode. Thus the anode corrodes away—is
sacrificed—as electric current leaves it (metal ions leave the anodic surface and enter the
electrolyte), hence the name sacrificial anode.
In an impressed current cathodic protection system, an external anode or anodes are
connected to the tank through an external power source (a battery or an alternating current
rectifier) that provides direct current. This electrical source provides enough direct current
to overcome that produced by the electrical cell created by the dissimilar metals and the
electrolyte, making the electrical charge on the (protected) tank negative, while the charge
on the anodes becomes positive. The impressed current source, thus drives the current
from the anode through the electrolyte and distributes it to the tank to be protected.
Anodes for an impressed current system may be of a variety of materials. Among those
commonly used are scrap iron in coke breeze backfill, graphite, high silcon cast iron, lead
silver alloy, platinum, or scrap steel. These are described in NACE RP-01-69 (1987
Revision), National Association of Corrosion Engineers Recommended Practice Control of
External Corrosion on Underground or Submerged Metallic Piping Systems. In either the
sacrificial anode or impressed current system, the current flowing from the attached anodes
is greater than the current flowing from the freely corroding tank and thus the tank
corrosion is mitigated.
The design and application of cathodic protection systems to steel tanks are tank and
site specific. The efficacy of a cathodic protection system is predicated on the current
demand of the tank to be protected and on the driving potential and current distribution
characteristics of the cathodic protection system within the ambient environment. Any
cathodic protection system requires periodic monitoring because of changing current
demands of the tank and/or changing characteristics of the current source and electrolyte
(soil).
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As with any upgrade methodology, an appropriate tank and site assessment must be
made to establish that the tank has sufficient physical integrity and projected life to warrant
application of the upgrade, cathodic protection in this case.
Cathodic protection, used as a stand alone upgrade method, will protect only the
exterior of the tank. It will mitigate exterior corrosion, but is not a "repair" for a tank
having even a small perforation.
In accordance with a consensus industry recommended practice, retrofitting
(upgrading) a tank with cathodic protection requires the services of a corrosion expert.
This expert must:
• assess the tank and tank site conditions required for designing the system
• oversee the application of the system
• establish a monitoring protocol and review the results of tests of the cathodic
protection system on a periodic basis
5.2.2 Procedure Description
There are many important factors to be considered by the corrosion expert in order to
determine the feasibility of upgrading a tank by the addition of cathodic protection and the
subsequent design of the system to be applied. Only after it has been established that the
tank has no history of leaking can the application of cathodic protection be considered. In
addition, the tank must be inspected to establish that it is free of corrosion holes
(perforations) and is structurally sound. After the tank's condition has been established, the
corrosion expert, hi following nationally recognized standards (identified below), will
require data that include the following:
• the size, shape, and condition of the tank
• the existence and type of any previous cathodic protection system
• the records of cathodic protection monitoring test results
• the existence and condition of any exterior tank coating
• the electrical isolation of the tank
• the electrical characteristics (resistivity) and chemical nature of the surrounding
soil
• the existence and nature of other buried metal structures in the tank vicinity and
whether or not these structures are cathodically protected
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• the existence of any sources of stray DC current
The corrosion expert may reference nationally recognized standards for upgrading with
cathodic protection. These standards include: (a) the API publication 1632, "Cathodic
Protection of Underground Petroleum Storage Tanks and Piping Systems;" (b) NACE
Recommended Practice RP-02-85, "Control of External Corrosion on Metallic Buried and
Partially Buried, or Submerged Liquid Storage Systems;" © MLPA Standard 632 "Internal
Inspection of Steel Tanks For Upgrading With Cathodic Protection Without Lining;" and
(d) ASTM ES 40-94, "Emergency Standard Practice for Alternative Procedures for the
Assessment of Buried Steel Tanks Prior to the Addition of Cathodic Protection."
In general, retrofitting with cathodic protection would utilize impressed current systems
rather than sacrificial anode systems. The reason for this is that the current requirements for
the tank and or piping are likely to be relative large due to little or no coating on the outside
of the tank (i.e., bare steel). Impressed current systems can provide a higher potential and
current than can sacrificial anode systems. (Sacrificial anode systems could be used when
the current demand of a tank is low, which might be the case if the tank has a tightly
adhering high resistivity coating that effectively minimizes the bare steel area exposed to the
soil.) For most older tanks, the impressed current system would be utilized because of its
higher driving potential and its capability of being adjusted to accommodate changing
current demand.
The physical placement of the anodes is important to ensure proper current distribution
and current density at the tank surface. While the adjustability and higher driving potential
of the impressed current system is an advantage, excessively high voltages can interfere with
adjacent systems. Excessively high voltages could also delaminate otherwise effective
coatings on the tank or dislodge tightly adhering corrosion product, which might be
protecting the tank from further corrosion or imparting physical integrity to the tank.
Delamination might occur as a result of the formation of hydrogen gas at the surface of the
metal. Because of this latter consideration, precision tank tightness tests are required to be
performed within 6 months after a cathodic protection retrofit.
As a practical matter, sacrificial anodes usually consist of a magnesium alloy packaged
in a specially formulated backfill material consisting primarily of gypsum and bentonite clay.
This backfill material is designed to provide ions for an electrolyte next to the sacrificial
anode and to hold moisture close to the anode, thus ensuring a good electrochemical
environment for the anode to function. A copper lead is connected to the anode when the
anode is cast and the lead wire is connected to the tank using a thermite weld.
5.2.3 Equipment
Required site assessment and system design data include the tank-to-soil potential
profiles and soil electrical resistivity profiles. Potentials are usually measured with a volt
meter electrically connected to the tank and to a copper/copper sulphate half-cell placed on
the soil surface. Soil resistivity is measured using a "four pin system" apparatus (power
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source, reference electrodes, and voltmeter) to measure IR drop in the soil. This system
requires a power source, reference electrodes and voltmeter. Soil core samples are usually
sent to a laboratory for analysis of sulfides, chlorides, hydrocarbons, moisture content,
conductivity, and pH.
Appropriate site excavation equipment is required to uncover a place on the tank to
attach the lead wire and to place the anodes around the tank. In addition, since most sites
are paved with either concrete or asphalt, appropriate trenching equipment is needed to run
the wires from the building to the anodes. After installation, equipment to patch the
pavement is required.
Rectifiers, which convert AC to DC are usually used as impressed current power
sources. Electrical leads would be run from the tank to a rectifier to a junction box (with
and ammeter and a voltmeter) to one or more buried anodes.
5.2.4 Method Performance
Once the cathodic protection system is installed and activated there are several criteria
that can be used to evaluate the efficacy of the system. Any one of these criteria, when met,
indicates that the probability is high that active corrosion is significantly mitigated by the
cathodic protection. The criteria (see NACE RP 02-85) are based on tank-to-soil potential
measurements. The most commonly used criterion is the -850 mV criterion, which is
achieved if the tank-to-soil potential is at least 850 millivolts, with the tank being negative
relative to the soil. There is also an "instant off" criterion in which the impressed current
system is turned off" while monitoring the tank-to-soil potential. If the difference between
the potential values after the instantaneous change and the asymptomatic value is more than
100 mV, this is indicative of cathodic protection. These criteria are described in NACE RP-
01-69 (Rev. 1987).
Cathodic protection requires the polarization of the cathodic reaction on the structure
to the static potential of the local action anodes. When cathodic protection is achieved, the
tank no longer supports anode regions as it has become the surface for the cathode reaction
alone. The tank-to-soil potential of a steel tank free to corrode in the soil may be on the
order of-550 mV when measured using a copper/copper sulfate half-cell reference
electrode. When cathodic protection is applied, this potential is driven in the negative
direction and, when the measured potential is -850 mV or more negative, the assumption is
that the tank surface is protected. Other criteria are sometimes utilized, for example if the
cathodic protection changes the tank-to-soil potential by more than 300 mV in the negative
direction, this is assumed to substantially mitigate the corrosion.
With any cathodic protection system, periodic monitoring and record keeping are
required. Since the tank structure is being protected by making it the cathode, the
corresponding anode will lose metal. In a sacrificial anode system, the anode corrodes to
protect the tank. When it has corroded away sufficiently, the protection of the tank stops.
Generally when an anode loses about 75% of its metal, cathodic protection may become
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ineffective until the anode is replaced. In an impressed current system, the anodes may also
corrode. In addition, other adjacent metallic structures may become anodic and may begin
corroding because of the impressed current. Periodic testing is required to ensure that the
cathodic protection system is still providing the required driving potential and current to
achieve protection and is not adversely affecting adjacent structures.
5.2.5 Field Considerations
Several considerations have been mentioned hi the previous discussion. Field
considerations will be site-specific and a comprehensive list is the purview of the corrosion
expert designing the system. Some general considerations are listed here to indicate their
nature.
a.
A corrosion expert must be involved in site assessment and system design and he
or she should follow a recognized standard. However, no "cookbook" protocol
can be developed that will apply to all applications and, therefore, some decisions
will be made on the basis of the expert's own experience.
Soil resistivity is an important factor in site assessment and system design. Soil
resistivity will be highly influenced by temperature, soil moisture, and soil
chemistry.
Soil pH, bacterial activity, salinity, presence of sulphide and chloride ions, and
other chemical characteristics can be important factors.
Electrical interferences such as stray currents are the bane of cathodic protection
practitioners.
Site surveyors, system installers, and system monitors should keep a very
comprehensive log book and document anything that might at anytime become
important to the corrosion expert.
Proper equipment must be used by trained personnel in designing and installing
the system. A common error is reversed polarity (i.e., hooking up the positive
and negative terminals backward) on a rectifier. Reversed polarity significantly
accelerates corrosion rather than mitigating it. The proper hookup makes the
tank become the cathode, that is, to have a negative charge relative to the soil.
5.2.6 Cost
The cost of adding cathodic protection to a site varies considerably. The factors that
influence the cost and add to this variability are the number of tanks to be protected, the
area to be covered, and the type of system to be installed. Generally, installation would
require at least two persons for about two days. All steel tanks present in a common
excavation, or that are electrically connected, should have cathodic protection installed at
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b.
c.
d.
e.
f.
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the same time. Periodic testing of the system is required to ensure that it remains
functional. One vendor estimated that the cost of inspecting the tanks, and designing and
installing an impressed current cathodic protection system at a site with three 10,000 gallon
tanks at $9,000 for the site. Another vendor estimated that the cost would be between
$6,500 to $8,000 for the same work. These estimates assume that all tanks and the site
meet the criteria for upgrading with cathodic protection. They do not include any required
repairs. Estimates could be expected to vary somewhat by location and by contractor.
5.3 Upgrading with Lining and Cathodic Protection
The combination of adhesive lining and addition of cathodic protection is a third
method of upgrading an existing tank that is allowed in the regulations. This method has
the advantage of protecting the exterior of the tank from (further) corrosion while at the
same time protecting the interior of the tank from internal corrosion. In addition, it can be
used to repair isolated defects hi the tank.
5.3.1 Fundamental Principles
The fundamental principles are those of cathodic protection described in Section 5.2.1
and of lining described in Section 5.1.1 and are not repeated here.
5.3.2 Procedure Description
The procedure would be a combination of the internal lining described in Section 5.1.2
and addition of cathodic protection described in Section 5.2.2 and so are not repeated here.
5.3.3 Equipment
The equipment required has been described earlier in Section 5.1.3 for lining and in
Section 5.2.3 for cathodic protection.
5.3.4 Method Performance
The method is a combination of the two previously described methods. The
combination should provide better performance in terms of protecting the tank than either
of the two methods alone. The cathodic protection part of the method requires periodic
monitoring to ensure that it remains functional. Eventually replacement of the anodes or
servicing of the rectifier may be required. The lining requires inspection after 10 years and
then at subsequent 5 year intervals to ensure that it is still adhering to the tank and is
protecting the interior.
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5.3.5 Field Considerations
The field considerations were described in Section 5.5.5 and 5.2.5 for lining and
cathodic protection, respectively.
5.3.6 Cost
The cost will include portions of cost from both lining and addition of cathodic
protection. However, it should be less than the sum of the two individual costs. Only one
inspection of the tank is needed. Thus, the cost would be approximately the sum of the
lining and cathodic protection costs less the cost of inspecting the tank for cathodic
protection. The cost will vary with location and vendor. For a site with three 10,000-
gallon tanks, the cost might range from about $17,000 to $27,000.
5.4 Combinations
A variety of combinations of upgrading techniques could be considered. However,
combining two or more of these techniques would increase the cost of the upgrade. This
increased cost might make the upgrade less attractive than replacing the tank. The increase
in cost would typically be less than the sum of the costs of the two upgrading methods,
since a substantial fraction of the cost consists of the tank inspection and/or preparation,
and parts of this are common to more than one method and so would not have to be
duplicated.
The most frequent combination of upgrades is internal lining of a steel tank combined
with the addition of cathodic protection. Any perforation of a steel tank disqualifies it for
upgrading with cathodic protection alone. Consequently, the inspection prior to upgrading
with cathodic protection might discover a perforation. In order to upgrade the tank, the
tank would have to be repaired. This could be accomplished by lining the tank. The
addition of cathodic protection would then proceed. This option—combining the addition
of cathodic protection with an internal lining—has found some use. It might be particularly
appropriate when several tanks at a location were to be upgraded, and one tank was found
to have a perforation. The additional cost would primarily consist of the lining material and
application, since the internal inspection currently used to qualify a tank for cathodic would
include abrasive blasting. Some increased cost might arise because of a different blasting
standard. If one of the new inspection techniques described in Sections 4.1 through 4.3
were used, then the additional cost of preparing the tank for the application of the lining
material would be incurred.
Installation of a flexible membrane liner combined with the addition of cathodic
protection is another upgrade option that could be considered. It would be a
straightforward application of those two upgrade methods. Since the inspection process for
installation of a membrane
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incurred. However, with the new inspection methods described in Sections 4.1 through 4.3,
these costs might be minimized or not incurred at all. At this time few, if any, tanks have
been upgraded with this combination.
The combination of tank lining (with an adhesive lining) and installation of a flexible
membrane liner would be another possible combination. This combination would provide
double containment for the product in that the flexible membrane liner would be the primary
containment. The lining applied to the tank interior would provide a secondary containment
for the product. The use of only these two methods (not including cathodic protection)
might be appropriate if the site was not conducive for the installation of cathodic protection
due, for example, to excessive stray currents or other buried metallic structures. At this
time it is doubtful whether any tanks have been upgraded with this combination of methods.
Finally, the combination of all three methods could be used to upgrade a tank. This
combination would provide certain advantages. The addition of cathodic protection to the
tank would mitigate external corrosion and help ensure the structural integrity or strength of
the tank shell. The interior lining would ensure that there are no perforations in the tank
shell, and so would provide a secondary containment for the product. The installation of a
flexible membrane liner would provide the primary containment for the product. This
conversion to a double walled or double contained tank system with an interstitial space for
leak detection monitoring would provide additional protection for the environment. The
state of California regulations specifically address the installation of a flexible liner, and,
when it is installed in a steel tank, require that the tank first be lined (with an adhesive
lining) and also be cathodically protected. Thus, this triple combination of upgrade methods
may find application in California.
5.5 Emerging Technologies
A number of new techniques have been developed by the industry as possible
alternative methods to upgrade tanks. Currently, the federal regulations only recognize
internal lining, addition of cathodic protection, or a combination of the two as upgrades.
Any application of these developing methods would require approval from EPA for
acceptance. One developing method is installation of a flexible membrane liner into a tank.
This method has been extensively used in Europe, particularly Germany, for heating oil
tanks. A second developing method is modifying the lining process to include an interstitial
porous spacer and changing the lining material to include fiberglass reinforcement so that
effectively a fiberglass tank is constructed inside the existing steel tank making the result a
double-walled tank. A third developing method is actually installing a fiberglass tank inside
an existing tank (referred to as re-tank). Each of these is discussed further below.
46
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5.5.1 Membrane Liner Systems
5.5.1.1 Fundamental Principles
There are a number of suppliers of flexible plastic membrane liners for underground
storage tanks. A membrane liner (bladder) is a large flexible bag that is prefabricated to
conform to the interior of a given tank. This fabrication takes into account the tank's
interior dimensions, the location and size of a manway, and the locations and sizes of other
tank openings for fill pipes, vent pipes, pumps, etc.
The membrane liner is installed in the tank and a partial vacuum is established in the
interstice. This is the area between the outside of the membrane and the inside of the tank
shell. Thus, once installed, the liner is held in place by pressure of the ah" inside the tank
and/or the pressure of the product on the membrane, relative to the reduced pressure
between the membrane and the tank shell.
The liner effectively provides a secondary containment system for the stored product.
That is, the membrane liner contains the product. The tank shell provides a secondary
barrier to the environment. If either is perforated, the other still contains the product and
prevents it from leaving containment and contaminating the environment. The rate of
vacuum decay within the interstitial space can be monitored to assess the physical integrity
of both the membrane liner and the outer tank shell.
There are several important considerations for parties investigating the possible use of a
membrane liner system. These include:
• the long-term compatibility of the liner material with the stored product
• the permeability of the liner material to the product
• the physical properties of the liner material needed to accommodate fabrication,
handling, and installation
• the structural integrity and interior smoothness of the tank shell
• the presence of a tank manway. If there is none, a permanent manway must be
installed
• the protocol and equipment for monitoring the interstitial space between the liner
and tank shell
As of this writing, there are no existing consensus standards for flexible membrane
liners. This is in contrast to the case for (adhesive) linings, for which such several such
standards exist, for example, API RP 1631, NLPA Standard 631, and UL Subject 1856.
47
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State regulators have established various requirements for underground storage tanks
along with their related components. These requirements are in addition to the federal
requirements specified by the U.S. EPA in 40 CFR Part 280. The various requirements deal
with the tanks themselves, spill and overfill protection, related components such as piping,
and (adhesive) tank linings as well as flexible membrane liners.
State regulators often require that manufacturers of tank equipment obtain an
evaluation of their product from an independent testing organization. For example, Article
3, Section 2631(d)(6) of the California Code of Regulations Title 23—Waters, Division 3—
State Water Resources Control Board, Chapter 16—Underground Tank Regulations states
"... secondary containment systems utilizing membrane liners shall be certified by an
independent testing organization."
5.5.1.2 Procedure Description
The installation of a flexible membrane liner in a tank requires the fabrication of the
liner, tank preparation, physical positioning of the liner inside the tank, conforming the liner
to the interior shape of the tank, installation of a striker plate, sealing the liner to the
manway and other openings, accommodation of the interstitial vacuum system, leak testing,
and placement of the manway cover.
5.5.1.3 Liner Fabrication
The manway and riser portions of the membrane must be precisely positioned on the
liner and the size and contour of these projections must match the tank openings. All seams
and joints must be hermetically sealed. The sealing of seams and joints is done at the
factory where the liner is fabricated.
5.5.1.4 Tank Preparation
The preparation of the tank that has been in service requires emptying the tank of
product, removing any sludge or residual material, purging the tank to acceptable vapor
concentrations, and an internal inspection. In contrast to lining a tank, abrasive blasting of
the interior surface is not necessarily required, although some states may require that it be
done as part of the internal inspection. The tank must be clean and dry and free of any
sharp protrusions that might puncture or abrade the membrane. Any such protrusions, for
example weld spatter from the tank manufacture, must be ground smooth. All flange
mating surfaces must be smooth, clean, and flat. As a final step the interior of the tank is
vacuum cleaned. If a membrane liner were installed in a new tank prior to introduction of
any product, the steps involving emptying and cleaning the tank would not be necessary.
The abrasive blasting might not be necessary, depending on the condition of the interior
shell surface.
48
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5.5.1.5 Liner Placement and Conformation
The placement of the liner and all other procedures must be performed in accordance
with the protocol of the supplier. This includes recognizing constraints imposed by ambient
conditions such as temperature and humidity.
The liner is generally shipped folded so that it can be lowered into the tank through a
manway. Workers inside the tank unfold and position the liner as necessary. Care must be
taken at this step to avoid puncture or abrasion of the liner. The liner can then be partially
inflated by the use of an air blower. After partial inflation, workers may go inside of the
liner to help position it as necessary while the liner is further inflated to conform to the tank
geometry. Once the manway and other projections of the liner are in place, workers exit the
tank and a partial vacuum is established in the liner/tank interstice to finally conform the
liner to the tank interior.
5.5.1.6 Striker Plate
One or more striker plates are installed in accordance with the supplier's protocol. The
requirements for underground storage tanks generally require a striker plate beneath each
opening to protect the tank or liner from damage caused by product delivery or inserting a
gauge stick or other equipment.
5.5.1.7 Final Sealing and Testing
The manway and other liner projections are sealed according to the supplier's
instructions. This commonly involves flanges, O-rings, gaskets, compression rings, and
other fittings. Fittings for gauges for establishing, maintaining, and monitoring the vacuum
are installed in the system. The system is checked by monitoring the vacuum decay
according to the appropriate protocol.
5.5.1.8 Equipment
The suppliers of flexible membrane liners may or may not contract for or be involved in
the complete tank upgrade. A complete upgrade would include the tank cleaning and
inspection, installation of spill and overfill protection, and leak detection or monitoring
systems. For liner installation following tank cleaning and inspection, equipment needs
include material handling equipment, a grinder or other method to eliminate burrs or other
protrusions inside the tank, a ladder, lights, safety equipment such as an explosivity meter,
self contained breathing apparatus, etc., an air blower, a vacuum cleaner, a vacuum pump,
appropriate tools for removing and replacing the manway, etc.
49
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5.5.1.9 Method Performance
A tank with a flexible membrane liner can be considered a "double wall" system. The
interstice between the tank shell and the liner can be monitored as in other double wall
configurations to provide continuous leak detection monitoring. This is usually
accomplished by monitoring the interstice for vacuum decay resulting from physical
integrity loss of the tank shell or liner material. However, other methods are possible, such
as vapor monitoring of the interstice, or inclusion of a sump for liquid monitoring.
Perforation of the tank shell will result in ingress of air and/or water while perforation
of the liner will result in ingress of liquid product, product vapor, or air. Flexible liners
made from currently available materials have some permeability to the product vapor, water
vapor, etc. Therefore, the vacuum on the interstice can be expected to decay, normally, at a
slow rate. In addition, the vacuum would be affected by changes in barometric pressure and
ambient temperature. The vacuum monitoring system must incorporate a means for
removal of condensed liquid and a vacuum pump that can be periodically activated to
reestablish the partial vacuum to a specified level.
Thus, the interstice is monitored not for an absolute level of vacuum, but for a rate of
vacuum decay. The rate of decay for a nonleaking tank and liner system will depend on the
permeability of the liner material, the surface area, the product being stored, and to some
extent the ambient conditions. That is, for example, the temperature can affect the vapor
pressure and the permeability of the liner material. In addition, the pressure differential
(vacuum) between the interstice and the atmosphere will be affected by changes in
barometric pressure and temperature according to the ideal gas law.
The protocol for monitoring the interstice is usually developed by and with the aid of
the lining material supplier. However, this need not be the case, as one manufacturer of
membrane linings provides no such leak detection capability and leaves the monitoring of
the interstitial space to the tank owner/operator. Any method of interstitial monitoring that
is compatible with the membrane liner system could be used by the tank owner/operator to
meet the EPA leak detection requirements for monitoring the interstitial space of double-
walled tanks.
5.5.1.10 Field Considerations
The ambient weather conditions are important considerations for the installation of a
flexible membrane liner. Temperature extremes can adversely affect the physical and
chemical properties of the synthetic resin liners. Liner flexibility, puncture resistance,
abrasion resistance, electrical resistance, impact resistance, and permeability will all be
functions of temperature. Surface temperatures of the tank shell below the dew point
would result in condensed water on exposed surfaces. This could affect corrosion rates for
the steel shell. Water trapped in the liner/tank interstice could lead to microbiological
growth.
50
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Material handlers and installers must be careful to not puncture or unduly abrade the
liner or tank walls and manways. This would particularly apply to taking care against
scuffing the material with shoes, ladders, or other equipment when working inside the liner.
The tank interior must be smooth so as not to puncture or abrade the liner. Grinding
procedures that generate sparks would be problematic for use in a tank that had previously
stored petroleum products, without adequate ventilation and monitoring.
5.5.1.11 Cost
The tank cleaning and inspection prior to installing a flexible membrane liner would be
comparable to those costs prior to application of an adhesive lining. One difference is that
for adhesive lining, abrasive blasting is needed to remove any dirt, scale, or other material
from the tank walls and to provide an anchor profile for the adhesion of the lining material.
Such abrasive blasting would not be needed for the flexible membrane liner, provided that
the tank walls can be cleaned sufficiently for internal inspection. Flexible membrane liner
companies often can clean the tank sufficiently with brushes and vacuums and do not
require abrasive blasting. This could vary by the individual tank condition, or local
regulations, however.
The materials cost for the flexible liners would depend on the size of the tank, and have
not been established. The physical installation of a flexible liner can be accomplished in 4 to
5 hours with an experienced team. One company reports that a team can generally install a
liner in one tank per day. Sometimes a team can install a liner in a second tank in the same
day, but this usually involves overtime, and the company feels that the quality of the work
may suffer, so a second installation in one day is not recommended.
5.5.2 Fiberglass Lining
A newer upgrade method is being developed. Currently, only minimal information on
this new system has been provided by the developer. This method involves the application
of a resin, interstitial material and fiberglass composite to form a rigid double wall retrofit
system. This would effectively build a second tank with a fiberglass wall inside the original
tank. An interstitial space would be created between the original tank wall and the one
newly installed. This procedure would effectively convert a single-walled tank into a
double-walled tank. The rigid liner would become the primary containment for the stored
product, while the original tank wall would become the secondary containment.
The interstitial space would be monitored for integrity using a method appropriate for
monitoring the interstitial space of a double walled tank. This monitoring might be done by
monitoring a partial vacuum, filling the interstitial space with a liquid and monitoring it
hydrostatically, or monitoring the space for vapor or liquid. Any method for monitoring the
interstitial space of a double-walled tank that is compatible with the construction of the rigid
liner could be applied to meet the EPA leak detection requirements for double-walled tanks
51
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For this to work, the original tank wall would be required to be free from corrosion holes or
any such perforations would have to be repaired before adding the new liner tank.
5.5.3 Installing a Fiberglass Tank in an Existing Tank
A similar approach to upgrading involves installing a fiberglass tank into an existing
steel tank. This alternative involves partial excavation of the steel tank and removal of one
end for installation of the fiberglass tanks. Then the end is replaced, resulting in a double-
walled tank system with an interstitial space for monitoring.
The costs for these procedures are not well-established at this writing. However, they
would probably fall somewhere between the cost of a standard lining upgrade and complete
replacement of the tank.
5.6 Outmoded Methods
No outmoded methods of upgrading underground storage tanks were identified.
52
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Section 6
Bibliography
1. 40 CFR Part 280 and 281, "Technical Standards and corrective Action
Requirements for Owners and Operators of Underground Storage Tanks," 1988.
2. ASTM Emergency Practice Standard ES 40-94, "Emergency Standard Practice for
Alternative Procedures for the Assessment of Buried Steel Tanks Prior to the
Addition of Cathodic Protection," 1995.
3. Section V, Article 9 of the ASME Boiler and Pressure Vessel Code (ASME
SE-797).
4. ASTM Standard G 1-90 (Re-approved 1994) "Standard Practice for Preparing,
Cleaning, and Evaluating Corrosion Test Specimens."
5. ASTM Standard G 46-94, "Standard Guide for Examination and Evaluation of
Pitting Corrosion," 1994.
6. ASTM Standard E 114, "Practice for Ultrasonic Pulse-Echo Straight-Beam
Examination by the Contract Method," 1990.
7. ASTM Standard E 797, "Practice for Measuring Thickness by Manual Ultrasonic
Pulse-Echo Contact Method," 1990.
8. API Standard 1631, "Interior Lining of Underground Storage Tanks," 3rd Edition,
April 1992.
9. NLPA 631, "Entry, Cleaning, Interior Inspection and Repair, and Lining of
Underground Storage Tanks," 4th Edition, 1991.
10. UL 58, "Steel Underground Tanks for Flammable and Combustible Liquids,"
1984.
11. H.R. Inspection Service, Inc., Shawnee, KS, "Radiographic Testing Procedure
NDE-RT."
12. NLPA Standard 632, " Internal Inspection of Steel Tanks For Upgrading with
Cathodic Protection Without Lining," 1st Edition, 1990.
53
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13. API Standard 1632, "Cathodic Protection of Underground Petroleum Tanks and
Piping Systems," 2nd Edition, December 1987.
14. Boone, S. E., P. J. Mraz, J. M. Miller, J. J. Mazza, and M. Borst, "State-of-the-
Art Procedures and Equipment for Internal Inspection of Underground Storage
Tanks," Risk Reduction Engineering Laboratory, Office of Research and
Development, U.D. Environmental Protection Agency, EPA/600/2-90/061,
January 1991.
15. "1996 Buyers Guide," National Petroleum News: Vol. 88, No. 3, March 1966,
pp. 29-100.
54
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Appendix
Vendor List
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VENDORS BY TYPE OF METHOD
Upgrading
Tank Lining (adhesive).
Armor Shield
RTE 2, Box 106A
Falmouth, KY41040
Tel: (606)-654-8265
FAX: (606)-654-4746
Bridgeport Chemical Group, Inc.
3883 Sweeten Creek Road
Arden, NC 28704
Tel: 704-684-8399
FAX: 704-684-3353
Industrial Environmental Coatings Corporation
183 IBlountRd, Suite B
Pompano Beach, FL 33069
Tel: 305-978-9355 or 800-449-6525
Flexible Membrane Liners
F. C. Witt Associates, Ltd.
P. O. Box 466
22 UN. E.L.Anderson
Claremore,OK74018
Tel: 918-342-0083 or 800-323-3335
World Enviro Systems, Inc.
P. O. Drawer 789
Shawnee, OK 74802
Tel: 405-275-3900
RELA TANKNOLOGY INC. (Subsidiary of Wulfing & Hauck)
3609 Fordham Court
Oceanside, CA 92056
Tel: 619-758-3200
A list of vendors, organized by upgrade method, is presented in this appendix. This list is provided solely to identify sources of information and points of contact
identified during this project. It is not a comprehensive listing of vendors. More complete listings of vendors appear in the March 1996 issue of National
Petroleum News Inclusion of vendors on this list does not constitute any endorsement or approval of the use of commercial products or companies This report
may not be cited for purposes of advertisement.
A-l
-------
Wulfing + Hauck
GmbH&CoKG
Ernst-Abbe-Strasse 2
34260 Kaufungen
Gennany
Tel: 05605/8009-110
Rigid In-Tank Liners
Armor Shield
RTE 2, Box 106A
Falmouth,KY 41040
Tel: (606)-654-8265
FAX: (606)-654-4746
Fluid Containment
P.O. Box 3085
Conroe, TX 77305
Tel: (409)-756-7731
FAX: (409)-756-7743
Cathodic Protection
Southern Cathodic Protection
Center One Suite 108
1100 Johnson Ferry Rd. N.E.
Atlanta, GA 30342
Tel: 617-573-9604
International Lubrication and Fuel Consultants
1201 Rio Rancho Blvd.
Rio Rancho, NB 87124
Tel 800-237-4532
Corrpro Companies, Inc.
P.O. Box 1179
Medina, OH 44258
Tel: 216-723-5082
A UA of vendors, organized by upgrade method, is presented in this appendix. This list is provided solely to identify sources of information and_points of contact
identiCedduringthUproject. It is not a comprehensive listing of vendors. More complete listings of vendors appear in the March 1996 issue of National
PttroleumNw*. Inclusion of vendors on this list does not constitute any endorsement or approval of the use of commercial products or companies. This report
nwy not be cited for purposes of advertisement.
-
-------
HARCO
1055 W. Smith Rd
Medina OH 44256
Tel 216-725-6681
Colorado Ground Water Resource Services
1809 E. Mulberry St.
Fort Collins CO 80524-3525
Tel 303-493-7780
DJA Inspection Services, Inc.
191 Howard St.
P. O. Box 489
Franklin PA 16323
Tel 814-437-3015
Envirovision Group, Inc.
33 IN. Route IW
Congers NY 10920
Tel 914-268-8265
Mid-Atlantic Tank Inspection
405 S. Parliament Dr.
Virginia Beach, VA 23462
Tel 804-497-7853
Seneca Corp
5636 NE 17th St.
Des Moines LA 50313-1616
Tel 515-262-5000
Tank Integrity Services, Inc.
8695 Parkdale Dr.
P. O. Box 33084
Cleveland, OH 44133
Tel 216-237-9200
Petroleum Monitoring Inc.
773 River Rd.
Smithland, KY 42081
Tel 502-928-4358
A list of vendors, organized by upgrade method, is presented in this appendix. This list is provided solely to identify sources of information and points of contact
identified during this project It is not a comprehensive listing of vendors. More complete listings of vendors appear in the March 1996 issue of National
PetroleumNews. Inclusion of vendors on this list does not constitute any endorsement or approval of the use of commercial products or companies This report
may not be cited for purposes of advertisement
A-3
FAX: 713-897-8183
Robotic Ultrasonic
Redzone Robotics, Inc.
2425 Liberty Avenue
Pittsburgh, PA 15222-4639
Tel: 412-765-3064
FAX: 412-765-3069
A list of vendors, organized by upgrade method, is presented in this appendix. This list is provided solely to identify sources of information and points of contact
identified during this project It is not a comprehensive listing of vendors. More complete listings of vendors appear in the March 1996 issue of National
PetroleumNews. Inclusion of vendors on this list does not constitute any endorsement or approval of the use of commercial products or companies. This report
may not be cited for purposes of advertisement
A-5
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Integrity Inspections
Soil Resistivity Integrity Tests
Southern Cathodic Protection
Center One Suite 108
1100 Johnson Ferry Rd. N.E.
Atlanta, GA 30342
Tel: 617-573-9604
International Lubrication and Fuel Consultants
1201 Rio Rancho Blvd.
Note: Redzone Robotics is developing the system. It is intended to be marketed through a
variety of companies. Many of the inspection companies may eventually offer this
inspection service.
Statistical Modeling
Warren Rogers, Associates, Inc.
747 Aquidneck Avenue
Middletown, Rhode Island 02842
Tel: 401-846-4747
FAX: 401-847-8170
International Lubrication and Fuel Consultants
1201 Rio Rancho Blvd.
Rio Rancho, NB 87124
Tel 800-237-4532
Corrpro Companies, Inc.
P.O. Box 1179
Medina, OH 44258
Tel: 216-723-5082
Thermal Wave Thermography
Progressive Maintenance Technologies, Inc.
P. O. Box 6403
Lee's Summit, MO 64064
Tel: 816-795-2499
Thermal Wave Imaging, Inc.
18899 West 12 Mile Road
Lathrup Village, MI 48076
Tel: 810-569-4960
Internal Inspection
Armor Shield
RTE 2, Box 106A
Falmouth,KY 41040
Tel: (606)-654-8265
FAX: (606)-654-4746
A list of vendors, organized by upgrade method, is presented in this appendix. This list is provided solely to identity sources of information and points of contact
identified during this project It is not a comprehensive listing of vendors. More complete listings of vendors appear in the March 1996 issue of National
PttroleumNews. Inclusion of vendors on this list does not constitute any endorsement or approval of the use of commercial products or companies. This report
msy not be cited for purposes of advertisement.
A-6
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Bridgeport Chemical Group, Inc.
3883 Sweeten Creek Road
Arden, NC 28704
Tel: 704-684-8399
FAX: 704-684-3353
Industrial Environmental Coatings Corporation
1831BlountRd, Suite B
Pompano Beach, FL 33069
Tel: 305-978-9355 or 800-449-6525
Southern Cathodic Protection
Center One Suite 108
1100 Johnson Ferry Rd. N.E.
Atlanta, GA 30342
Tel: 617-573-9604
State Environmental Services
1801 Stillwell Ave
Brooklyn, NY 11223
Tel: 718-765-3355
Tank Automation, Inc.
734ThicleRd
P.O. Box 1395
Brick NJ 08724
Tel: 908-280-2233
Scott Company of California
1717 Doolittle Drive
SanLeandro, CA 94577
Tel: 510-895-2333
Armour Tank Lining Co., Inc.
5333 University Avenue, NE
FridleyMN 55421
Tel: 612-571-1087
A list of vendors, organized by upgrade method, is presented in this appendix. This list is provided solely to identity sources of information and points of contact
identified during this project It is not a comprehensive listing of vendors. More complete listings of vendors appear in the March 1996 issue of National
report
A-7
—,_, — f—j—_ „ „ ..„. „ w**if *w»Mj»j.i»w »uuiig, v/j. wuMiua. LVUJLH i-um^iGiG listings 01 vciiuots appear in uic jviHrcn iyyo issue QiivcttiotiQi
Petroleum News. Inclusion of vendors on this list does not constitute any endorsement or approval of the vise of commercial products or companies This report
may not be cited for purposes of advertisement
-------
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