ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 280

[FRL-3385-3]

Underground Storage Tanks; Technical Requirements

AGENCY:  Environmental Protection Agency (EPA).

ACTION:  Final rule.

SUMMARY:  The Environmental Protection Agency (EPA) today finalizes regulations for underground storage tanks containing petroleum or substances defined as hazardous under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), except any substance regulated as a hazardous waste under Subtitle C of the Resource Conservation and Recovery Act (RCRA).  These regulations were first proposed on April 17, 1987 (52 FR 12662) and a subsequent Supplemental Notice was published on December 23, 1987 (52 FR 48638).

	Under Section 9003 of RCRA, EPA must establish requirements for leak detection, leak prevention, financial responsibility, and corrective action for all underground storage tanks containing regulated substances as necessary to protect human health and the environment.  Today's final rule sets forth requirements satisfying the mandates of section 9003, except that final requirements concerning financial responsibility will be addressed later by EPA in another FEDERAL REGISTER notice.

EFFECTIVE DATE:  [Insert date 90 days after publication in the FEDERAL REGISTER], except § 280.22(g) which is effective [insert date 30 days after publication].

ADDRESSES:  The docket for this rulemaking (Docket No. UST 2-1) is located at the U.S. Environmental Protection Agency, 401 M Street, S.W., Washington, DC  20460.  The docket is open from 9:30 a.m. to 3:30 p.m., Monday through Friday, except for federal holidays.  You may make an appointment to review docket materials by calling<PHONE_NUMBER>.  You may copy a maximum of 50 pages of material from any one regulatory docket at no cost.  Additional copies cost $0.20 per page.

FOR FURTHER INFORMATION CONTACT:  The RCRA/Superfund Hotline at<PHONE_NUMBER> (toll free) or 382-3000 (in Washington, DC).

SUPPLEMENTARY INFORMATION:  The contents of today's preamble are listed in the following outline:

I.	Authority

II.	Background

	A.	Subtitle I of RCRA 	B.	Operating Principles 	C.	Summary of April 17 Proposed Rule 	D.	Public Comment on the Proposal 	E.	Summary of the Supplemental Notice and the Notice of  		Availability of New Information 	F.	Influences on the Final Rule

		1.	Scope of the Problem 		2.	New Cause-of-Release Information 		3.	Industry Codes and Practices 		4.	Industry Trends  		5.	UST System Technology Development 		6.	Leaking USTs Present A Unique Regulatory Challenge 		7.Emerging State and Local UST Programs and EPA's Approach to Regulation

	G.	Conclusions Since Proposal

III.	Today's Final Rule

	A.	Summary of Today's Final Rule 	B.	Major Points of Departure from April 17 Proposal

		1.	More Frequent Tank Tightness Testing of Existing  			Unprotected Tanks During the 10-Year Upgrade Period 		2.Less Frequent Monitoring of New and Upgraded Tanks Until Age 10 		3.	Gradual Phase-in of Release Detection Based on Age 		4.	More Stringent Requirements for Pressurized Piping

	C.	Alternative Approaches Considered

		1.	New UST Systems Containing Petroleum 		2.	Existing UST Systems Containing Petroleum 		3.	Hazardous Substance UST Systems 		4.	Corrective Action

IV.	Analysis of Today's Rule

	A.	Program Scope

		1.	Applicability 		2.	Regulatory Exclusions 		3.	Deferral of Regulations 		4.	Definitions

	B.	UST Systems:  Design, Construction, Installation, and 		Notification

		1.	Design and Construction Requirements (§ 280.20) 		2.	Installation (§§ 280.20(d) and (e)) 		3.	Upgrading of Existing Systems (§ 280.21) 		4.	Notification (§ 280.22)

	C.	General Operating Requirements

		1.	Spill and Overfill Control (§ 280.30) 		2.Operation and Maintenance of Corrosion Protection (§ 280.31) 		3.	Inspection and Maintenance of the Tank System (§ 280.31) 		4.	Compatibility ( § 280.32) 		5.	Repairs (§ 280.33) 		6.	Reporting and Recordkeeping (§ 280.34)

	D.	Release Detection

		1.	Overview 		2.	Section-by-Section Analysis

	E.	Release Reporting, Investigation and Confirmation

		1.	Overview 		2.	Section-by-Section Analysis

	F.	Release Response and Corrective Action for UST Systems 		Containing Regulated Substances

		1.	Background 		2.	Major Issues Influencing the Final Rule 		3.	Section-by-Section Analysis

	G.	Out-of-Service UST Systems and Closures

		1.	Introduction 		2.	Temporary Closure (§ 280.70) 		3.	Permanent Closure (§ 280.71) 		4.	Assessing the Site at Closure (§ 280.72) 		5.	Applicability to Previously Closed UST Systems (§ 280.73) 		6.	Closure Records (§ 280.74)

	H.	Analysis of Other Significant Comments

		1.	Reliance on Codes Developed by Nationally Recognized 			Organizations  		2.	Additional Decisionmaking Authority for Implementing 			Agencies

V.	Relationship to Other Aspects of the UST System Program

	A.	Interim Prohibition 	B.	Notification 	C.	Leaking Underground Storage Tank Trust Fund 	D.	Exempted Tank Studies

VI.	Relationship to Other Agency Programs

	A.	CERCLA  	B.	Hazardous Waste Tank Program  	C.	Hazardous Waste Management Regulations

		1.	Hazardous Substances 		2.	Petroleum and Petroleum-based Substances

	D.	Used Oil Regulations 	E.	SPCC 	F.	DOE High Level Radioactive Waste Program

VII.	Economic and Regulatory Impacts

	A.	Regulatory Impact Analysis

		1.	Executive Order 12291 		2.	Costs 		3.	Benefits 		4.	Cost Effectiveness of the Final Rule 		5.	Economic Impacts on Existing Facilities 		6.Integration of Technical Standards and Financial Responsibility Rules

	B.	Regulatory Flexibility Act

		1.	Small Entities Potentially Affected by the Rule

	C.	Paperwork Reduction Act

VIII. List of Subjects in 40 CFR Part 280

I.	AUTHORITY

	These regulations are issued under the authority of sections 2002, 9001, 9002, 9003, 9004, 9005, and 9006, 9007, and 9009 of the Solid Waste Disposal Act of 1970, as amended by the Resource Conservation and Recovery Act of 1976, as amended (42 U.S.C. 6912, 6991, 6991(a), 6991(b), 6991(c), 6991(d), 6991(e), 6991(f) and 6991(h)).

II.	BACKGROUND

A.	Subtitle I of RCRA

	The Hazardous and Solid Waste Amendments of 1984 extended and strengthened the provisions of the Solid Waste Disposal Act as amended by the Resource Conservation and Recovery Act (RCRA) of 1976.  One major portion of RCRA as amended, Subtitle I, provides for the development and implementation of a comprehensive regulatory program for "underground storage tanks" containing "regulated substances" and releases of these substances to the environment.

	Subtitle I defines "underground storage tank" as a tank system, including its piping, that has at least 10 percent of its volume underground.  Throughout this preamble and final rule, the terms "underground storage tanks," "USTs," and "UST systems" include both the underground storage tank vessel and the underground piping connected to it.

	"Regulated substances" are defined as substances defined as hazardous under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), except hazardous wastes regulated under Subtitle C of RCRA, and petroleum.

	Subtitle I excludes the following from the definition of USTs:

	oFarm or residential tanks of 1,100 gallons or less capacity storing motor fuel for noncommercial purposes;

	oTanks storing heating oil for consumptive use on the premises where stored;

	o	Septic tanks;

	oPipeline facilities (including gathering lines) regulated under the Natural Gas Pipeline Safety Act of 1968, the Hazardous Liquid Pipeline Act of 1979, or state laws comparable to these Acts;

	o	Surface impoundments, pits, ponds, and lagoons;

	o	Storm-water or wastewater collection systems;

	o	Flow-through process tanks;

	oLiquid traps or associated gathering lines directly related to oil or gas production and gathering operations; and

	oStorage tanks situated on or above the floor of underground areas, such as basements and cellars.

	Subtitle I contains several major provisions for the regulation of UST systems.  Section 9002 requires UST system owners to notify states of the existence of their UST systems.  These notification requirements were addressed in a final rule published by EPA on November 8, 1985 (50 FR 46602).  Section 9002, as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA), also requires that states use the notifications they receive to compile tank inventories.  Under federal grant agreements, states are providing EPA with aggregated data from these notifications.

	Under section 9003, EPA must promulgate regulations applicable to all owners and operators of UST systems as necessary to protect human health and the environment.  In promulgating these regulations, section 9003(b) authorizes the Administrator to distinguish between types, classes, and ages of underground storage tanks.  Section 9003 requires EPA to issue design, construction, installation, and compatibility standards for new tanks, as well as requirements applicable to all tank owners and operators concerning leak detection, recordkeeping, reporting, closure, corrective action, and financial responsibility.

	Section 9003(h), as amended by SARA, gives EPA--and states under cooperative agreements with EPA--authority to clean up petroleum releases from UST systems or to require their owners and operators to do so.  It also establishes a trust fund to finance these activities.

	Section 9004 permits EPA to authorize states to implement their own UST programs in place of the federal requirements if the state's requirements are "no less stringent" than EPA's and provide for adequate enforcement.  Programs which are less stringent in certain areas may receive approval for an interim period.

	Other provisions of Subtitle I pertain to definitions (section 9001); entry, inspection, and information gathering (section 9005); enforcement (section 9006); federal facilities (section 9007); state authorities (section 9008); and studies and reports to Congress required of EPA (section 9009).

	This preamble and final rule pertain to the requirements mandated by sections 9003(a), (c), (e) and (g); they also meet the study requirements of sections 9009(a) and (b).  Final rules for state program approval requirements, under section 9004, are found elsewhere in today's FEDERAL REGISTER.  Final rules for financial responsibility requirements for petroleum UST systems, under sections 9003(a) and (d), will be promulgated by EPA at a later date.

	Section 9003(c) requires EPA to establish the following minimum technical requirements for all UST systems: to maintain a leak detection system or comparable system designed to identify releases to protect human health and the environment; to maintain records of any such release detection system; to report releases and corrective action taken; to take corrective action in response to a release; and to close tanks to prevent future releases.  Under section 9003(e), EPA must also establish performance standards for new UST systems.  At a minimum, these standards must include design, construction, installation, release detection, and compatibility standards.

	Until the promulgation of today's final rule, section 9003(g) established an "Interim Prohibition" that allowed installation of UST systems after May 8, 1985, only if the UST system is protected from corrosion, prevents releases due to corrosion or structural failure for the operational life of the tank, and is constructed of material compatible with the substance to be stored.  The law allowed an exemption from the requirement of corrosion protection if an UST system is located at a site having a soil resistivity measured at 12,000 ohms/cm or greater.  An interpretive rule concerning the Interim Prohibition was published on June 4, 1986 (51 FR 20418).  These Interim Prohibition requirements are replaced by today's final rule for new tank standards, except in those few cases where the Agency has decided to defer regulatory action on some types of UST systems.  For these deferred UST systems, the Interim Prohibition will continue to apply until EPA takes action in the future either to regulate or not regulate them (see §§ 280.10 and 280.11 of the final rule).

B.	Operating Principles

	Faced with the mandate of Subtitle I, EPA recognized several unusual aspects of the regulated universe that have created special problems in developing an effective regulatory approach.  First, the regulated universe is immense, including over 2 million UST systems estimated to be located at over 700,000 facilities nationwide.  Second, over 75 percent of the existing systems are made of unprotected steel, a type of tank system proven to be the most likely to leak and thus create the greatest potential for health and environmental damage.  Third, most of the facilities to be regulated are owned and operated by very small businesses, essentially "Mom and Pop" enterprises not accustomed to dealing with complex regulatory requirements.  Fourth, numerous technological innovations and changes are now underway in various sectors of the UST system service community.

	In response to the unique aspects of this regulated community, and the clear need for comprehensive management of USTs during their operating life, EPA has identified and followed several key operating principles, described briefly below, in developing the final regulations for USTs.

	oThe UST program must be based on sound national standards that protect human health and the environment.

	oThe UST regulatory program must be designed to be implemented at the state and local levels.  State and local governments have been and continue to be the authorities most capable of effective oversight of UST systems and response to releases.

	oThe regulations must be kept simple, understandable, and easily implemented by the owner and operator in order to facilitate voluntary compliance.  Section 9003(b) specifically indicates that technical capability can be considered in developing the Subtitle I rules.

	oThe regulations must not inhibit new UST technological developments.

	oThe regulations must be designed to retain the flexibility necessary to accommodate, where possible, the special needs of the UST regulated community, which is largely composed of small businesses with limited resources available for capital improvements.

	oIn order to encourage the utmost voluntary compliance, the regulations should build upon current industry trends and tie into and utilize ongoing industry initiatives toward more sound UST management.  Towards this end, Section 9003(b) specifically authorizes EPA to consider industry practices and consensus codes in developing appropriate UST regulations.  The Agency expects the nationwide use of these new management practices to yield direct environmental benefits.

	By reflecting these operating principles in the final UST regulations, the Agency believes it has taken the most effective approach toward protecting human health and the environment.

C.	Summary of April 17 Proposed Rule

	On April 17, 1987, EPA proposed regulations for USTs storing either petroleum or hazardous substances (other than hazardous wastes regulated under Subtitle C of RCRA) (52 FR 12662).  These proposed regulatory measures set requirements for both new and existing UST systems to control the major causes of releases from these tank systems and included, among other things, corrosion controls, proper installation requirements, and spill and overfill prevention measures.

	Figure 1 illustrates several key aspects of the regulatory program proposed in April 1987; requirements for corrosion protection and monthly release detection at all new UST systems; the phase-in of either monthly release detection or periodic tightness testing combined with inventory control at all existing USTs, within 3 years if unprotected from corrosion and within 5 years if protected; and the upgrading of all existing UST systems to the new tank standards within 10 years.  In addition, the proposed new and upgraded tank standards for hazardous substance USTs required secondary containment with interstitial monitoring.

	[INSERT FIGURE 1 HERE.]

	Figure 1 does not illustrate several other requirements and standards proposed for both new and existing UST systems:  the design and installation of new UST systems; spill and overfill prevention; UST system repair; system closure; release detection methods and performance; and release confirmation, reporting, and response (including corrective action requirements).  These proposed requirements and the manner in which they may have changed in the final rule are described in detail later in today's preamble.  Several major points of departure from the proposal are identified and discussed in section III. below.

D.	Public Comment on the Proposal

	EPA received over 5,000 individual comments from over 1,100 commenters on the April 17 proposal, including verbal and written comments from the three public hearings.  In general, these public comments supported the Agency's overall approach to the proposed regulations and the substantive requirements for new and existing UST systems.

	Many comments addressed specific parts of the proposed rule, suggesting changes or calling attention to potential problems.  These specific comments are discussed below in today's preamble.  In summary, many comments tended to center on three areas:  concern for the impact the UST rule would have on small businesses, calls for for EPA to adopt more stringent requirements for certain sensitive areas, and suggestions on the best way to phase in release detection.  (See the corresponding sections in today's preamble for a full discussion of these comments.)  The financial responsibility requirements generated more public comment than any other single area.  Comments on this issue will be addressed in the financial responsibility final rule that will appear in a later FEDERAL REGISTER.

E.Summary of the Supplemental Notice and the Notice of Availability of New Information

	After the April 17 proposal appeared, EPA realized that some aspects of the technical standards needed to be clarified and that more public comment on these matters was needed.  Consequently, EPA published a Supplemental Notice on December 23, 1987 (52 FR 48638).  This Supplemental Notice dealt with four areas pertaining to the proposed technical requirements:

	(1)	Use of "static inventory control" to monitor used oil UST systems;

	(2)	A listing of substances subject to petroleum UST standards;

	(3)	Alternatives to release monitoring for piping and tanks protected from external corrosion; and

	(4)	An alternative definition of "flow-through process tank."

Public response concerning these issues is discussed in later sections of this preamble.

	On March 31, 1988, EPA published a Notice of Availability of additional information for public comment.  It announced the availability of information pertaining to several technical areas of the proposed rule including general operating requirements, release detection and tank closure.  This new information was submitted by commenters, gathered in meetings or conferences and produced by Agency research programs.  Few public comments were provided concerning these documents.

F.	Influences on the Final Rule

	In the preamble to the April 17 proposal, the Agency discussed the scope and nature of the problem posed by UST systems and several important influences on the development of the proposal (52 FR 12665-12671).  Today's final rule builds on that earlier information and has benefited from numerous comments provided by the public on the issues highlighted in the proposal.  The following section briefly discusses several areas that have received further consideration from EPA in the development of today's final rules.

1.  Scope of the Problem

	The preamble to the proposed rule (52 FR 12665) presented estimates of the number of leaking UST systems based on EPA studies, local government experiences, and industry estimates.  Among the statistics cited were the percentage of systems failing tightness testing, the percentage of systems actually leaking, the correlation of tank age to failure, and the extent and impact of soil and ground-water contamination from USTs.  After the proposed rule was issued, EPA completed an additional study of the causes of release from UST systems.  This new study was placed into the public docket and announced as available for comment in the December 23, 1987, Supplemental Notice.  This study, "Causes of Release from UST Systems," and the public comments on it were important in developing today's preamble and final rule.

a.	Current Estimates of "Non-Tight" UST Systems

	In the preamble to the proposal (52 FR 12665), EPA cited evidence that numerous UST systems are non-tight and may be leaking.  This evidence was based largely on three studies:  EPA's "Underground Motor Fuel Tanks:  A National Survey" reported tank tightness testing results and found that 35 percent of over 450 tank systems surveyed nationwide failed tightness testing; Suffolk County's UST program data revealed that 26 percent of over 6,000 tank systems tested in this New York county failed; and a Chevron-sponsored testing program found that nearly 10 percent of over 3,000 of their UST systems failed.

	Commenters responding to the proposal who had experience with tightness testing provided various claims that between 11 and 48 percent of existing UST systems failed under test conditions.  In an EPA-sponsored meeting, a group of experienced, independent installation contractors expressed their expert judgment that increased awareness of the UST problem, use of better tanks, and use of better installation and maintenance procedures have decreased the probability of present-day systems testing non-tight to about 20 percent, in contrast to the 50 percent of UST installations they believed would have tested non-tight several years ago.

	After publication of the proposal, EPA studied several additional pieces of information concerning causes of release from UST systems.  For example, EPA further reviewed the records of over 10,000 tightness test results from local UST programs (in Suffolk County, New York; Austin, Texas; and San Diego, California).  EPA also analyzed an extensive and detailed historical set of records from a Texas tank testing company (the Service Station Testing Company of San Antonio, Texas).  The EPA-sponsored report, "Causes of Release from UST Systems," is based on all these data and concludes that approximately 25 percent of existing UST systems are found to be non-tight when tested using current methods and that loose tank fittings or faulty piping causes 84 percent of these tightness test failures.  Figure 2 summarizes the Agency's findings concerning the causes-of-release profile as derived from tank testing results and documented follow-up at over 10,000 UST systems conducted nationwide.

	[INSERT FIGURE 2 HERE]

b.	Estimated UST Systems with Releases

	Current indications concerning the number of UST systems nationwide that have had releases in the past or are now leaking are less precise than the tank tightness data, but the Agency believes the information that is available is significant nonetheless.  As discussed in the preamble to the proposed rule, in many places in the nation that are still without state or local UST regulatory programs today, release detection only takes place when someone sees or smells the release (52 FR 12665).  These historical data suggest that only about 10 percent of release incidents in these areas are discovered by inventory controls or mechanical release detection methods.  Although the large number of incidents that are known to threaten or have contaminated ground-water wells is significant, it is not an accurate prediction of leaking UST systems because most UST systems are not located near wells.

	As the result of aggressive UST monitoring programs in two states, over 5,000 UST sites in California and 3,000 sites in Florida have been identified as having had releases during the past three years.  These recent discoveries already exceed 10 percent of the number of UST sites in each of these states, and the number of releases identified in just these two states may soon exceed the cumulative total of releases reported to all the states up until 1985 (see 52 FR 12665).  At a more local level, UST system programs in Dade County, Florida, and San Jose, California, have also identified (through required release detection and system closure procedures) that well over 10 percent of their UST facilities have had some noticeable or significant releases into the surrounding soil and groundwater.  Thus, the initial findings by state and local UST regulatory programs that are particularly aggressive appear to corroborate an industry-sponsored study (than previously cited Chevron investigation) that found approximately 10 percent of their 1,000 UST facilities located throughout the South and Southwest of the United States have had an adverse impact on nearby ground water in the form of released product floating on top of the ground-water table (see 52 FR 12666).

	Public comments received in response to the proposal concerning this subject are not conclusive.  Some industry sources provided very low estimates, claiming that from 0 to 3 percent of UST systems have had releases.  Others claimed the actual number of leaking tank systems could be as high as 50 percent in some areas.  Many estimated that the actual range is somewhere between 8 to 20 percent of UST sites, and the average of all estimates reported by commenters falls into this range.  As shown in the previous figure (Figure 2), approximately 25 percent of all systems are now testing as non-tight.  About 15 percent of the sites whose systems were tested actually proved to have a leak under normal operating conditions (tank and delivery piping leaks), and this proportion falls within the above-estimated range provided by the commenters.

	Some commenters attempted to provide additional insight into the relationship between tank age and failure by indicating that tanks begin to fail tightness tests (and leak) at a much greater frequency after 12 years.  In addition, the recent EPA causes-of-release study includes one study that indicated 10 to 13 percent of the tanks that are 12 to 13 years old were non-tight.  This is more than double the proportion of non-tight tanks tested in other age groups.  In another study, of the tanks actually found to be leaking, 42 percent of the leakers were 15 to 20 years old, and 30 percent of the leakers were 10 to 15 years old.  All of the tanks that were leaking were made of bare steel.  This demonstrates that the critical age in a typical unprotected steel tank's life is the period between 10 to 20 years of age when breakthrough from corrosion is most likely to begin.

	Some commenters disputed the severity of the threat posed to the nation by leaking UST systems, which was discussed in the preamble to the proposed rule.  For example, one suggestion was that the data presented in the preamble indicate less than 0.008 percent of the total area of the United States is affected by contamination due to leaking UST systems.  In general, EPA finds this line of reasoning unpersuasive.  In particular, this argument ignores, (1) that population density in the nation is not uniform (with most areas being sparsely populated or unpopulated); (2) that tank systems are generally located near populated areas to provide the fuel for these centers of human activity and; (3) that there are numerous documented cases of drinking water wells that have been threatened or already destroyed by leaking UST systems nationwide.  The dispersal of leaked contaminants within ground-water aquifers can also affect an area many times larger than the soil-contaminated area.  Further information gathered over the coming years of UST program implementation will ascertain the full magnitude of the impacts that leaking UST systems pose in terms of contamination to the nation's environment, but EPA concludes that the evidence collected to date, including the information provided by commenters on the proposal, clearly supports the need for today's final rules.

2.   New Cause-of-Release Information

	EPA's new information concerning releases from UST systems comes primarily from public comment and an EPA-sponsored study ("Causes of Release from UST Systems") that was made available for public comment in the December 23, 1987, Supplemental Notice.  Review of this information has resulted in the following findings concerning the major causes of releases today:

	oMost releases do not come from the tank portion of UST systems, because piping releases occur twice as often as tank releases;

	o	Spills and overfills are the most common causes of releases;

	oVarious nonoperational UST components at the top of USTs are loose and leak in the event of overfills;

	oAlthough the older bare steel tanks fail primarily by corrosion, the "new generation" USTs (i.e., coated and cathodically protected steel, fiberglass-clad steel, and fiberglass tanks) have nearly eliminated failure induced by external corrosion;

	oCorrosion, poor installation techniques and workmanship, accidents, and natural events (e.g., frost heaves) are the four major causes of failure for piping; and

	oWhen piping fails, pressurized systems pose a significant added threat of sudden, large releases.

	Thus, the major causes of releases from UST systems are due to failures of unprotected tanks, leaks in delivery piping, leaks from vent pipes and fittings on top of the tank, and spill and overfill errors.  Comments received on the original proposal (52 FR 12665-12668) and the Supplemental Notice concerning causes of release generally tend to corroborate the above findings.  The following information summarizes some of the most relevant findings that are important in guiding today's standard-setting.

a.  Tanks

	Most existing tanks are made of bare steel.  Numerous tank failure histories indicate that when bare steel tanks fail they almost always do so because of external corrosion.  Of all of the current causes of release, corrosion of bare steel (tanks and pipes) is by far the most important.

	Tank manufacturers have responded to this problem with a "new generation" of tanks.  Innovative tanks began to appear about 20 years ago in the United States in three basic forms:  fiberglass-reinforced plastic (FRP); steel with a corrosion-resistant coating and cathodic protection; and steel-FRP composite.  A dramatic acceleration in the use of new generation tanks occurred with the introduction of the federal law's "Interim Prohibition" three years ago.  These protected tanks now are estimated to account for about 20 to 25 percent of existing USTs.  Although "new" in terms of protective designs, some of each of the new types of tank systems have been in the ground for over 20 years.  Reported failures observed in the field due to corrosion (or other reasons) are very rare.

	Failures (leaks) at all existing FRP tanks appear to have occurred at less than a rate of 0.05 percent per year of the total FRP tanks installed nationwide.  Many commenters and other sources support the field estimates collected by EPA that less than 0.5 percent of the total number of existing FRP tanks have ever leaked.  Although some installation-related failures have occurred in the past, heightened installer awareness of proper practices and techniques appropriate to FRP technology, manufacturer-sponsored contractor education programs, and production quality assurance appear to be responsible for a consistently decreasing failure rate of FRP tanks.  The most important reported failure mode for these tanks is improper installation practices.

	One new tank type, the STI-P3, is a favorite of corrosion engineers.  These steel tanks have an external noncorrodible coating and a factory-applied metal anode that sacrifices itself to protect any bare spots on the tank, and the tank vessel is electrically isolated from any attached piping.  Very few failures have ever been reported, and those failures are due to installation damage or improper maintenance, not design.  In Ontario, Canada, where STI-P3 tanks have been widely used, the number of tank releases due to corrosion is reported to be declining as old tanks are replaced with STI-P3 tanks.

	The steel-FRP composite tanks have not been used as widely as either the FRP or coated and cathodically protected tanks described above.  Approximately 65,000 have been installed in this country.  No corrosion-related failures have been reported.  Many commenters suggested that this type of tank has several advantages over both FRP and coated and cathodically protected steel tanks, such as durability, no need for maintenance, and an added barrier between the tank and the environment should the steel tank be breached by internal corrosion.

	As the threat of external corrosion is reduced by new tank designs, internal corrosion may eventually become the primary cause of failure for steel tanks.  Internal corrosion, however, occurs far less frequently and takes longer to manifest itself than external corrosion.  Many commenters have reported problems with internal corrosion under the drop tube (i.e., fill pipe located within the tank) of steel tanks.  Data submitted from the tank lining industry confirm these reports.  The tank manufacturing industry, however, began to respond to this problem several years ago by including "striker plates" under all openings of their new tanks.

	Lining tank interiors is another way to prevent releases due to internal and external corrosion.  Tank interior lining has been employed by major corporations and small businesses both as a short-term solution for potentially leaking tanks and as a preventive measure for temporarily giving structurally sound, non-leaking existing tanks the same protection from corrosion-induced releases that "new generation" tanks have.  Data indicate this to be a successful procedure for extending an existing tank's operational life.  Even when employed in the absence of external cathodic protection, failure rates are reported to be very low, apparently because current industry consensus codes only recommend the use of lining when the tank shell is assessed to be able to withstand the expected rate of corrosion at the site (determined by assessing the tank's existing condition).

b.  Piping

	Most commenters rated delivery piping the most significant source of releases and reported releases occurring twice as frequently from piping as from bare steel tank releases.  Two types of piping systems are commonly used:  suction piping, which is used in low-volume applications where only a few dispensers are needed; and pressurized piping, which is used in high-volume applications where many dispensers are fed from one tank.  Each piping system has unique advantages and disadvantages, discussed below.

	Suction piping is considered by commenters to be safer than pressurized piping because it operates at less than atmospheric pressure.  If the pipe develops a leak, air or ground water is usually drawn into the pipe instead of product leaking out.  Commenters suggested, however, that suction piping systems do not operate efficiently in a number of settings, such as at high altitudes, in hot climates, or in high-volume delivery situations.

	Pressurized piping systems reportedly are used at about 95 percent of new retail motor fuel system installations.  If the delivery line is breached, free product is released until the pressure in the pipe equals the pressure outside the pipe.  Without add-on instrumentation or devices, large volumes of product can be pushed out of breaches in the piping when product is delivered to the pump.  Pressurized piping simply pushes more volume to meet this increase in demand, releasing large amounts of product quickly into the environment.

	Comments received by EPA indicate that the releases from pressurized piping systems can be catastrophic in the absence of monitoring and automated pump flow restriction devices.  Incidents involving releases of thousands of gallons have been reported to EPA by experienced installers.  It is estimated that at least 70 percent of the volume of product lost through pressurized pipe releases could be avoided by retrofitting each line with a simple, inexpensive, continuous in-line pressure monitor that automatically restricts product flow in the presence of a significant line leak.

	Both suction and pressurized piping are often damaged by external corrosion.  Cathodic protection of steel piping would significantly reduce corrosion failures.  Presently, most steel piping is protected by galvanizing and coating, or coating and wrapping.  The threaded portions at joints are the most common failure points because the protection is removed from them while threading and is never replaced.  In these cases, cathodic protection would reduce joint failures.  Other joint failures result from untightened joints, cross-threaded joints, or improperly made joints.  Improving the installer's education and skills in the complex task of pipe installation would reduce these piping failures.

	Also, installers and others have estimated that piping is damaged 10 percent of the time at new installations between the installation of equipment and completion of paving.  They strongly recommend that a test of new equipment before start-up is essential as a sound practice, particularly with pressurized piping.

	Natural forces and accidents also cause piping failures.  The piping is near the surface of the ground and, thus, subject to frost heaves and overloading.  In addition, the starting and stopping of product delivery causes the piping to move and shift.  This eventually causes joint failure in many piping systems.  "New generation" piping systems comparable to the "new generation" of tanks are under development but not widely used.

c.  Nonoperational Components

	Nonoperational components consist of tank bung holes, tank manholes, vent and fill lines, vapor recovery lines, and manifold piping (the piping used in connecting tanks together).  These components, all located above the top of the tank, are called nonoperational because releases from these sources do not occur under normal operating conditions.  Releases from them are usually unseen because they are underground.  These releases are episodic and usually of small volume, because they only occur when the tank is overfilled or when manifolded tanks are filled through the piping connecting the tanks together.  Generally, when an overfill occurs, the volume of product contained in the fill tube above the loose nonoperational component will be forced out into the environment until the product level in the UST drops below the leaking component.  These leaking, nonoperational components are reported to be most often caused by improper installation practices, such as loose bung hole plugs not being tightened at installation or vent lines being hand-tightened on top of the tank.

	Two solutions are available to stop this type of release:  either ensure proper installation of these different types of fittings or eliminate overfills.  Elimination of overfilling of the tank is the surest remedy and is probably the easiest to accomplish with overfill shutoff devices now widely available.  Most releases associated with nonoperational components would be prevented if overfills were successfully eliminated.

d.  Spills and Overfills

	In addition to episodic releases from nonoperational components, there is an even more prevalent source of release that takes place at the tank fill port during tank filling.  Although usually small in volume, spill and overfill releases are probably the most common causes of release from UST systems.  These releases usually occur at the surface of the ground around the top of the fill pipe when the delivery truck's hose is disconnected from the fill pipe. Most of these releases go unreported due to the typically small volume of product lost (generally, less than the volume of the delivery truck's hose).  Most excavated bare steel tanks, however, show evidence of spilled material, such as dissolved asphalt coating near the fill pipe.  Regulatory officials in Dade County (Florida) cite spills and overfills as the primary cause of release--45 percent of reported releases.  These surface releases are at least twice as numerous as tank or piping releases.

	Spills most often occur at the fill pipe opening when the delivery truck's hose is disconnected, usually releasing only a few gallons.  Overfills occur far less frequently but usually release much larger volumes.  Overfills generally result in a release from loose, nonoperational components located above the tanks (as discussed in the previous section ), or from the top of the tank's vent pipe as product is forced out during overfilling of the system.  Experienced installation contractors emphasize to EPA that the control of spills and control of overfills are two different problems and equipment that controls one may not control the other.

3.   Industry Codes and Practices

	In the preamble to the proposed rule (52 FR 12670), EPA identified numerous industry consensus codes and recommended practices that influenced the development of the proposed regulatory program.  A table was provided listing several codes and practices concerning the proper management of UST systems that have been developed, mostly in the past decade, by industry associations, nationally recognized professional organizations, and independent testing laboratories.  Since the proposal of the federal rule over a year ago, these consensus code-making groups and industry standard-setting activities have continued at an increased rate.  (Refer to section IV.H.1. for a more detailed discussion clarifying the use of codes developed by nationally recognized organizations or independent testing laboratories.)

	Table 1 reflects a sampling of the current status of this national consensus code-making network.  The codes and standards marked with an asterisk have been reviewed, updated, or revised over the past year.  For example, last summer, the American Petroleum Institute reviewed several of its recommended practices (e.g., API 1631 and 1615) and improved the guidance provided in these documents.  In addition, several new codes are now under development or have been recently added.  For example, the National Leak Prevention Association was formed and developed an industry consensus code for the interior lining of tanks (NLPA 631).

	[INSERT TABLE 1 HERE.]

	Table 1 provides a snapshot of the depth and scope of the collective wisdom that has developed over the past several years in the United States concerning the proper standards for UST systems.  The recent updates and additions to this list of industry consensus codes and recommended practices reflect what appears to be a resurgence of interest in several areas of sound UST management practices.  Numerous commenters on the proposal cited specific developments in these consensus codes and provided copies of some of the most recent codes that were added or updated and revised.  In general, they provided a reminder to EPA that this improving body of knowledge should be understood and considered during the development of today's final rule.

4.   Industry Trends

	The nature and extent of the public response to the proposal has generally confirmed that a significant level of voluntary industry upgrading and replacement programs is already underway.  The closure and replacement trends briefly discussed in the preamble to the proposal (52 FR 12671) were confirmed by some commenters.  Numerous major oil companies, independent marketers of retail motor fuel, transportation fleet operators (government and private), and various manufacturers with USTs have clearly embarked on their own UST system management programs before promulgation of today's final rule.

	One of the most encouraging trends has been the increasing use of protected UST systems nationwide.  EPA estimates that there are currently over 450,000 UST systems in use today that are protected from external corrosion.  This expanding use of an important and necessary approach to the prevention of releases has increased rapidly over the past three years, particularly after the Interim Prohibition went into effect in May 1985 (section 9003(g) of RCRA), making illegal the installation of bare steel UST systems.  EPA estimates that, during the past three years over 50,000 new protected tanks were installed annually.  To date, over 210,000 FRP tanks, 120,000 coated and cathodically protected tanks, and 65,000 steel-FRP composite tanks have been installed.  In addition, an estimated 70,000 tanks have had their interiors lined to prevent releases, and another 50,000 UST systems are estimated to have been provided with field-installed corrosion protection systems.  According to tank manufacturers, the number of new bare steel tanks installed over the past three years has dropped precipitously.

	Early findings from several local UST programs visited by EPA staff since the proposal have confirmed the beginnings of an accelerated rate of closure of old, substandard UST systems (for example, in Suffolk County, New York; Austin, Texas; Dade County, Florida; and Sunnyvale, California).  A rapid rate of closure appears to manifest itself when each of these, and several other, local UST programs initiate their release detection requirements.  Thus, EPA's earlier projections that as much as three-fourths of the existing UST universe will be closed, upgraded, or replaced to the requirements of the Interim Prohibition within 10 years appears to be realistic (52 FR 12671).  Today's final rule will further ensure that these positive changes are accomplished and increased.

	EPA believes these are important developments because the successful implementation of this program depends a great deal on the regulated community's voluntary compliance.  The Agency is convinced that the most wide-spread compliance will be facilitated by technically sound standards that are capable of easy implementation by a highly varied regulated community.  Thus, as much as possible, the federal technical requirements must rely on familiar industry codes and build on recognized and effective trends occurring in the field of UST management that are consistent with protection of human health and the environment.

5.   UST System Technology Development

	As discussed in the preamble to the proposal, the array of technical control options available to address causes of releases, as well as response to releases that occur, also appears to be growing.  Numerous commenters provided technical information to EPA about newly available equipment being marketed for use in the prevention, detection, and correction of releases from UST systems.  New equipment for use either inside or outside of the UST system to detect releases from the underground tank or attached piping is being introduced for sale at many trade shows and industry fairs nationwide, including less expensive methods for providing secondary containment with interstitial monitoring for both existing and new UST systems.

	Several new types of equipment capable of preventing spills and overfills appear to be less costly and more easily retrofitted to existing tanks than earlier models.  For example, several new models of line leak detectors have recently been introduced to the UST market that are more sophisticated and sensitive than older types of equipment.  In addition, numerous companies have contacted EPA about their development efforts in the area of retrofitting preventive devices onto existing tanks or refurbishing old tanks.  Makers of nylon tanks are in the process of soliciting the approval of Underwriters Laboratories of Canada in that country.  Finally, vapor gas vacuum extraction techniques for use in the subsurface cleanup of volatile substances are also under accelerated development and investigative use in several places nationwide.  This cleanup technique has reportedly had widespread use in West Germany for a number of years.

	In summary, business in the UST control technology sector appears to be booming, and invention is proceeding at a rapid pace.  All this activity is a good indication that in the future, simpler, cheaper, and more dependable equipment will be produced to aid in the prevention, detection, and correction of releases.  Experienced persons in UST management in the public and private sectors have told EPA staff that the current level of control technology development by far exceeds any previous efforts within this industry.  In order to avoid interfering with this ongoing development of innovative and more environmentally protective new technologies, the Agency has chosen to write regulations that allow room for these new developments.

6.  Leaking USTs Present a Unique Regulatory Challenge

	EPA believes its approach to setting standards for UST systems on a national scale will have to be different from most national environmental programs because the UST problem is significantly different.  This difference is mainly due to three factors:  the large number of facilities to be regulated, the comprehensive scope of the regulations, and the nature of the regulated community.

	The most significant problem is the sheer size of the regulated community.  Nationally, over 700,000 UST facilities account for about 2 million UST systems, an average per state of about 14,000 UST facilities and 40,000 UST systems.  Estimates indicate that roughly 75 percent of existing UST systems are unprotected from corrosion.  In addition, because a relatively high proportion of UST facilities (10 to 30 percent) already have had a leak, or will soon leak unless measures are taken to upgrade them, the average number of leaking UST systems may range from 1,400 to 4,200 per state in the near future.

	The large number of tank owners and tank systems has also led EPA to conclude that the final federal UST standards must include a phase-in period for certain requirements that apply to existing tank systems.  Although all federal requirements are in effect immediately for new tanks, owners and operators will have additional time to upgrade existing tank systems to the corrosion protection standard for new UST systems, and to install release detection equipment for existing UST systems.  This phased-in approach is needed to establish a reasonable schedule that recognizes the limited capability of 700,000 UST owners and supporting service and manufacturing industries to respond immediately to new national regulations, and provides sufficient flexibility for implementing agencies.  The experience of states that have already been operating UST regulatory programs is that it takes several years for most owners or operators of existing UST systems to understand, plan, and arrange for the purchase, scheduling, and installation of necessary services and equipment required by the regulations.  The phase-in approach also has the added benefit of allowing time for continued development and improvement of available technologies in the marketplace for prevention and detection of releases from UST systems (as discussed previously in this section of the preamble).

	In addition, today's final rule establishes comprehensive requirements for the management of a wide range of UST systems.  These final standards for UST systems are designed to reduce the number of releases of petroleum and hazardous substances, increase the ability to quickly detect and minimize the contamination of soil and ground water by such releases, and ensure adequate cleanup of contamination.  To do this, the standards in some way must affect every phase of the life cycle of a storage tank system:  selection of the tank system; installation, operation and maintenance; closure and disposal; and cleanup of the site in cases of product release.  As a result, these standards must be technically adequate to ensure the wide array and needed level of improved performance when implemented.  At the same time, these wide ranging requirements must be straightforward enough to be understood and to be carried out successfully hundred of thousands of times nationwide.

	A third problem is the nature of the regulated community.  A large proportion of USTs are owned by small businesses with $500,000 or less in total assets.  For example, 72 percent of all retail motor fuel outlets are owned by small businesses.  An important influence in the making of today's technical standards has been EPA's attempt to minimize the regulatory impact on small businesses without compromising the statutory requirements to protect human health and the environment.  EPA's efforts to minimize the regulatory impact are discussed in a Regulatory Flexibility Analysis conducted for this rule, as specified by the Regulatory Flexibility Act of 1980, and a summary of that analysis is presented later in this preamble.

	Specifically, the Agency is convinced that the national UST standards must be kept simple and implementable by state and local officials because many UST facilities are owned and operated as small local businesses, such as "Mom and Pop" gasoline service stations and convenience stores.  These small entrepreneurs, who are used to operating their business with minimal regulation, will be significantly affected by environmental regulations for UST systems.  The experience of state and local agencies with UST programs is that large national businesses that own tanks are generally willing and have already begun to comply with UST requirements.  Owners of small businesses, however, generally need constant reminders and technical assistance to bring them into compliance.  Given the nature of this regulated community, a regulatory program often will be most effectively carried out by the level of government closest to the problem, and thus able to respond quickly and to create a visible presence.

7.   Emerging State and Local UST Programs and EPA's Approach to Regulation

	Many states and localities have adopted requirements applicable to UST systems.  Although these state and local requirements are diverse and vary in stringency, EPA believes that the formulation of federal standards should build upon the many effective state and local programs now in operation or about to begin operating in order to utilize this reservoir of accumulated UST experience in a way that can rapidly develop into a strong federal-state partnership for addressing this national concern.  Section 9004 also indicates Congressional intent that states with effective programs are to play a major role in implementing the program.

	At least 18 states and hundreds of local programs are currently addressing the ground-water contamination and cleanup problems posed by leaking UST systems through established regulatory programs.  Several states, such as California, New York, and Florida, and local UST programs such as those in Suffolk County (New York), Dade County (Florida), and Austin (Texas), have established specific UST system regulations that include standards for design, construction, and installation of new UST systems; closure, retrofitting, and repair of existing UST systems; and release detection and corrective action requirements for all UST systems.  EPA believes this type of state and local UST program activity nationwide will increase significantly with today's promulgation of EPA's technical standards.  Similar to the experiences in the three lead states identified above, other states will begin to wrestle for the first time with the reality of how to implement their UST programs.  As the dangers posed by existing UST systems become more widely known, local UST programs and involvement should increase significantly over current levels.

	Given the large number of UST facilities, tank systems, and potential cleanups needed, EPA is convinced that many aspects of this regulatory program will be most effectively carried out at the state level of government.  Local government involvement in this regulatory program will be important.  For example, a small city with about 700 facilities and 2,000 tank systems within its jurisdiction should be able to implement a manageable regulatory program.  If each of those 700 facilities installs one new tank during the next five years, that would be about three installations per week.  If that small city requires a city inspector to be present at each installation, an inspector must be in the field three times a week for this task alone.  In addition, the inspector could be required to be present for periodic tank testings, closures, upgrading or retrofit, and cleanups.

	Confronted with the above implementation realities, EPA has developed a more decentralized approach for addressing the realities of the national UST regulatory program.  This approach is based on several critical factors.  First, as more and more state and local governments become involved, the work of the UST program must be routinely carried out in thousands of jurisdictions nationwide.  Several operating state and local UST programs already report that they are very busy "running the store," expressing surprise at the size of the regulated community, and that fairly simple tasks must be routinely repeated numerous times for the implementing agency to be successful in bringing UST systems into, and maintaining, compliance.

	Second, visits to several state and local UST programs have shown that they have often developed their own unique requirements and methods of implementation, adapted to the types of tanks, physical environment, and regulated community with which they are concerned while they are, at the same time, all geared towards solving similar technical problems.  They need the flexibility to continue and to improve upon approaches which address the specific environmental needs of their communities.  They have common implementation problems, however, and have expressed the need for better technical aids, such as data management tools.

	Third, many state and local governments that already implement UST programs report a significant level of visible on-site monitoring, requiring a constant "regulatory presence" to effectively ensure this regulated community's compliance with UST requirements.  A significant environmental gain is achieved through implementation at the local level by these individual UST programs.  Thus, improving their performance will produce maximum environmental benefits and best ensure the success of the UST program nationwide.  As the head of the "distribution system" of UST-related technical information and implementation tools, EPA believes that its implementation efforts should be focused on serving the network of state and local programs through listening to their concerns and helping them solve implementation problems with tools that improve the effectiveness of their programs.

	Finally, EPA believes that a more decentralized approach to the federal implementation of the UST program is needed to ensure real gains in protection of human health and the environment.  Because there are so many UST sites nationwide, it would be very difficult to establish a credible federal implementation presence through compliance monitoring and enforcement at the federal level.  A more realistic and effective approach is for EPA to provide support tools and guidance to state and local regulators that can be used to improve their programs' compliance performance.

	In adopting this role, the Agency has recognized that it must not only establish sound national standards but, more importantly, must focus on improving the performance of the state and local implementing agencies.  Approval of state programs to operate "in lieu of" the federal program takes on a new meaning under this approach because it becomes a basic soundness test to ensure that the work associated with implementation of these state or local requirements will, in fact, cause the needed level of improvement in UST system management when carried out by the regulated community.  The requisite state enforcement authority and technical standards must be ensured and will be the focus for approval by EPA.  Thus, overall successful performance and implementation of this new national program is less focused on implementing detailed, national technical standards than it is on establishing the national UST program in a way that ensures effective, environmentally protective programs at the grassroots level and improving the performance of these programs over time.  EPA's final requirements for state program approval are presented in detail elsewhere in today's FEDERAL REGISTER.

	Thus, in recognition of its approach to UST implementation, EPA has attempted to establish final technical standards that are protective of health and the environment but, at the same time, are simple, understandable and implementable by state and local officials.  EPA also recognizes that there is often more than one proper way to address specific technical problems that are the focus of the final regulations.  Therefore, the Agency has attempted to identify and offer as many effective alternative technical approaches as possible particularly where this flexibility can be applied in the future by the implementing agencies.  In this way, the final technical requirements remain focused on the key environmental problems which the implementing agencies face.  Promoting the network of state and local implementation is the best way to ensure that significant protection of human health and the environment will be achieved by today's final requirements.

G.	Conclusions Since Proposal

	EPA has drawn several conclusions from the influences discussed above and in the background sections of the preamble to the proposed rule (52 FR 12663-12671).  Some of these conclusions support the direction and emphasis set forth in the proposal, and others indicate a need for change in the final rule.

	Given the large size of the existing regulated universe and the proportion of these UST systems that have leaked or are presently leaking, there is a need to finalize today's rules as an important step  resources.  The number of sites needing significant cleanup due to a number of poor past UST management practices is expected to be in the tens of thousands nationwide.

	Cause-of-release information related to unprotected tanks supports EPA's proposed approach for upgrading of unprotected tanks.  The new information, however, indicates a need for more frequent monitoring of unprotected tanks than was proposed.  By contrast, protected tanks appear to need less frequent monitoring than proposed.  Also, pressurized piping systems need more stringent monitoring than was proposed.

	Increased activity in the review and improvement of national consensus codes supports EPA's proposed reliance on these codes as providing the most up-to-date consensus practices and expertise concerning what constitutes proper UST system management.  The nationwide increase in the use of protected systems, the recent number of tank closures, and the development of new prevention, detection, and corrective action technologies are encouraging.  The final rules must be designed to foster and take advantage of these trends.  They must be simple and easily implementable by the regulated community to ensure the maximum level of voluntary participation by tank system owners and operators.  The Agency continues to believe that the size and nature of this regulated universe presents several unique regulatory challenges that necessitate the phase-in of some of the requirements for existing UST systems to ensure that genuine implementation is accomplished.

	The continuing and rapid emergence of numerous state and local UST programs is expected and will be encouraged by EPA because this is where the "real work" of this new national program must actually take place.  The Agency's approach to UST program implementation must start with a technically sound set of national standards.  These requirements, however, must be kept simple and implementable because most improvements in actual UST performance (and protection of human health and the environment) are expected to be achieved by working closely with state and local governments over time to increase the level of the effectiveness of their UST programs.

III.	TODAY'S FINAL RULE

	This section provides a summary of EPA's final rule.  It also identifies and describes several major points of departure from the proposed rule, several alternative strategies, public comments on them, and the Agency's rationale for the direction of the final rule in several other key areas.  More detailed summaries of all the public comments and the Agency's responses to them can be found in the "Comment and Response Summaries Background Document" that has been placed into the public docket in support of today's final rule. !iiia!

A.	Summary of Today's Final Rule

	EPA is today promulgating regulations for underground tanks storing either petroleum or hazardous substances other than hazardous wastes regulated under Subtitle C of RCRA.  These requirements establish measures for both new and existing UST systems to prevent, detect, and clean up releases from these systems.  These final requirements of Part 280 fulfill the mandates of RCRA sections 9003(a), (c), and (e), and sections 9009 (a) and (b).  The major elements of today's final rule are noted below.

	oNew UST systems must be designed and constructed to retain their structural integrity for their operating life, in accordance with national consensus codes of practice (see Table 1 provided earlier in this preamble).  All tanks and attached piping used to deliver the stored product must be protected from external corrosion.  Cathodic protection must be monitored and maintained to ensure that UST systems remain free of corrosion.

	oNationally recognized industry installation standards must be followed in placing new UST systems in service (see Table 1).  Owners and operators of new USTs must certify that proper installation procedures were followed and identify how the installation was accomplished.

	oOwners and operators of both new and existing UST systems must follow proper tank filling practices to prevent releases due to spills and overfills.  In addition, owners and operators of either new or upgraded UST systems must use devices that prevent overfills and control or contain spills.

	oTanks must be repaired in accordance with nationally recognized industry codes (see Table 1).  These national codes include several tests that must be conducted to ensure quality repairs.

	oTo close UST systems, industry-recommended practices must be followed: the UST system can be removed from the ground or left in place after removing all regulated substances and cleaning the tank, filling it with an inert substance, and closing it to all future outside access (see Table 1).  In addition, owners and operators must perform an assessment at the time of UST closure to ensure that a release has not occurred at the site.  If a release has occurred, then corrective action must be taken.

	oRelease detection must be instituted at all UST systems.  For petroleum UST systems, several methods will be allowed, although tank owners and operators must adhere to requirements concerning their use.  In addition, owners and operators must follow special requirements for pressurized delivery lines.  Petroleum UST systems are not required to have secondary containment with interstitial monitoring.  All new or upgraded UST systems storing hazardous substances, however, are required to have secondary containment with interstitial monitoring, unless an alternate release detection method is approved by the implementing agency.  The owners and operators must demonstrate to the implementing agency that a release detection method will detect releases of the stored substance in a manner no less stringent than the release detection methods allowed for petroleum USTs and that a method of corrective action is available to clean up a release of the hazardous substance should one occur.

	oGenerally, release detection at existing UST systems must be phased in over a 5-year period based on the age of the tank.  The oldest UST systems (usually unprotected from corrosion) are required to phase in release detection within 1 year, and the newest tank systems (usually protected from corrosion) by the end of the 5-year period.  Release detection for all pressurized delivery lines must be retrofitted within 2 years.

	oPeriodic tank tightness testing (every 5 years) combined with  monthly inventory control is allowed at new or upgraded UST systems for 10 years after new tank installation or existing tank upgrade.  After 10 years, monthly release detection is required.

	oEither monthly release detection or a combination of annual tank tightness testing with monthly inventory control is required of substandard existing USTs until they are upgraded.  Existing UST systems must be upgraded or closed within 10 years of the effective date of the final rule, or within 1 to 5 years if a release detection method is not available that can be applied during the required phase-in period for release detection.  Upgrading of petroleum UST systems includes retrofitting of corrosion protection and both spill and overfill controls at all tanks.  Upgrading of hazardous substance UST systems also includes secondary containment and interstitial monitoring or an alternate release detection method approved by the implementing agency.

	oTank owners and operators must report suspected releases.  Indications of a release must be reported to the implementing agency, including positive results from release detection methods, unless the initial cause of the alarm has been immediately investigated and the alarm is found to be false.  After reporting suspected releases, owners and operators must perform release investigation and confirmation tests and, where a release is confirmed must begin corrective action.

	oOwners and operators of leaking UST systems must follow measures for corrective action.  Immediate corrective action measures include mitigation of safety and fire hazards; removal of saturated soils and floating free product; and an assessment of the extent of further corrective action needed.  A corrective action plan would be required for long-term cleanups addressing ground-water contamination, although these cleanups could begin upon notification of the implementing agency by the owner and operator.  Cleanup levels would be established on a site-by-site basis as approved by the implementing agency.

B.	Major Points of Departure from April 17 Proposal

	Today's final rule includes four release detection requirements that represent significant changes to the proposed rule:

	(1) More frequent tank tightness testing (annual) of unprotected tanks during the initial 10-year upgrading period;

	(2) Less frequent monitoring of new and upgraded tanks until age 10;

	(3) Phase-in of release detection over 5 years at existing tanks based on age; and

	(4) More stringent release detection for all pressurized piping systems.

The final requirements in each of these areas, and EPA's rationale for revising the proposal, are summarized below and shown graphically in Figure 3.  The shaded areas indicate the major changes from the proposed approach.  More detailed discussions of these major points of departure are also provided in later sections of today's preamble.

	[INSERT FIGURE 3 HERE.]

1.   More Frequent Tank Tightness Testing of Existing Unprotected Tanks During the 10-Year Upgrade Period

	In the proposed rule (§§ 280.40 and 280.41), EPA provided owners and operators of existing UST systems without corrosion protection with two options for release detection, but only during the proposed 10-year upgrade period.  The two options were: 1) to perform monthly release detection monitoring or, 2) to conduct monthly inventory control combined with a tank tightness test every 3 years.  The option of tank tightness testing (in combination with inventory control) was proposed because tightness testing is already widely practiced.  The proposed frequency of testing every 3 years was based on the Agency's belief that the industry could not accomplish testing of such a large universe of existing tanks on a more frequent basis because the supply of testing services could not respond to such a large demand.

	Several commenters suggested that the proposed tank tightness testing alternative be allowed in the final rule but only if the testing were required more frequently.  EPA now shares the concerns of those commenters.  The Agency is particularly concerned about unprotected existing tanks, which have the greatest probability of leaking.  New information on causes of release has prompted the Agency to believe that tightness testing conducted once every 3 years leaves too much time between tests during which an unprotected steel tank may develop corrosion holes and release product.  Therefore, in the final rule the Agency requires that tank testing be performed every year during the 10-year upgrade period, instead of every third year as was proposed.  Because unprotected steel tank systems pose the greatest threat to the environment and public health, EPA believes that increasing the frequency of tightness testing will provide better environmental protection and is therefore warranted.

	With regard to EPA's initial concern that such a frequency would be impractical or difficult to achieve, numerous public comments were received from the release detection industry indicating their belief that more frequent tank tightness testing is feasible.  Commenters also verified that tank tightness testing is already a commonly used release detection method, and its technology and resources are currently widely available.

2.   Less Frequent Monitoring of New and Upgraded Tanks Until Age 10

	EPA's proposed approach for new USTs required either frequent-to-continuous (at least monthly) release detection monitoring or semiannual tank tightness testing in combination with monthly inventory control.  The Agency proposed frequent-to-continuous monitoring at new tanks because, the more frequently release detection is applied, the more likely an actual release will be detected when it occurs, as explained in detail in the proposal (52 FR 12720), and thus it was believed to be needed to ensure adequate protection of the environment and public health.

	Several commenters questioned the proposal to require more frequent release detection at new protected tanks than at existing (older) unprotected tanks.  New information on causes of release (see section II.F. of the preamble) confirms that new tanks are the least likely to leak.  The probability of new or upgraded tanks leaking, particularly early in their operational lifetime, is extremely low.  Therefore, the Agency agrees with commenters who suggested that new tanks should be allowed to be monitored less often than proposed.

	Today's final rule replaces the proposed semiannual tank testing with a requirement to conduct tank testing at least every fifth year during the first 10 years of the UST's operational life at a new or upgraded UST.  As proposed, however, tank testing must be used in combination with monthly inventory control to be considered an approved release detection method.  Because long-term experience with tank corrosion protection technology is not yet extensive, and because existing bare steel tanks rarely fail before 10 years of age, today's final rule requires monthly release detection at protected and upgraded tanks only after they pass their tenth year of operation.

3.    Gradual Phase-in of Release Detection Based on Age

	EPA proposed to phase in release detection at existing UST systems over a 3-year period for USTs unprotected from corrosion and a 5-year period for USTs protected from corrosion.  This approach was proposed because it was believed to be the fastest schedule reasonably implementable and would require unprotected tanks (which have the greatest potential to leak) to have release detection in place sooner than protected tanks.  In the preamble to the proposal (52 FR 12677), the Agency identified three approaches towards phasing in of release detection:  (1) a rapid phase-in (over 1 to 2 years), (2) a gradual phase-in (over 3 to 5 years), and (3) a class approach requiring a rapid phase-in at the most sensitive UST locations and more gradual phase-in elsewhere.  After considering public comments received on this issue, the Agency has decided in today's final rule to retain the gradual phase-in approach but to base the phase-in on the age of the UST system, with the oldest tanks being required to have release detection first.

	The preamble to the proposal solicited public comment on the appropriateness of considering tank age, vulnerability of hydrogeology, distance to drinking water wells, distance to vital ecological systems, and any other factors in the selection of a phase-in approach for release detection.  Most commenters supported the gradual phase-in to take place over time periods ranging from 3 to 10 years, but recommended that it be based on age.  A few recommended the rapid phase-in approach, and most of those recommended that the phase-in be based on age.

	Today's final rule requires the oldest tanks, with or without corrosion protection, to apply release detection within the first year and the newest tanks no later than 5 years after the effective date of today's rule.  This approach is believed to offer several advantages:  (1) EPA has concluded that the phasing in of release detection at all existing UST systems in the large universe is implementable within 5 years; (2) the age-based sequencing schedule ensures that implementation of the requirements will take place in an orderly fashion that will spread out the demand for release detection services and avoid bottlenecks; (3) it gives higher priority to older, unprotected tanks, which have been found to have the greatest potential to leak; and (4) it still allows the newer, protected tanks, which are the least likely to be leaking, to wait until the fifth year, as did the proposed rule.  In choosing the gradual approach, the Agency agrees with those commenters who cited the rapid approach as being impossible to implement with such a large universe of UST systems.  In addition, the gradual approach is supported by numerous existing industry, state, and local management programs which utilize the gradual approach as the most feasible phase-in approach.  The reasons the Agency is taking this gradual phase-in approach are discussed in more detail later in this preamble (section IV.D.2.).  The class approach was deemed unimplementable for other reasons discussed in more detail later in this section of the preamble.

4.   More Stringent Requirements for Pressurized Piping

	The proposed rule contained release detection requirements for pressurized piping in addition to those requirements for new tank systems.  Specifically, automatic release detection and shutoff devices were proposed for the pressurized piping at new tank systems unless continuous release detection or interstitial monitoring was installed.  Suction piping systems were exempt from the proposed requirements if other minimum construction requirements were met (see 52 FR 12774).  Information obtained by the Agency at the time of the proposal indicated that 20 to 30 percent of all reported releases are due to piping failures.  EPA also suspected that pressurized piping systems, which are reportedly the most commonly used withdrawal system at new retail motor fuel installations, were responsible for the larger  releases.

	Information obtained by EPA after publication of the proposal (see section II.F. of today's preamble) indicates that piping system failures are responsible for a much greater percentage (80 to 85 percent) of release incidents than previously thought.  Public comments received by EPA confirmed the Agency's belief that failure of pressurized piping systems frequently results in large releases.

	In today's rule, EPA has set forth more stringent release detection requirements for pressurized piping systems.  Systems must be:  (1) equipped with automatic shutoff devices or automatic flow restrictors and use either annual line testing or monthly release detection monitoring; or (2) have continuous interstitial or vapor monitoring combined with either shutoff devices or alarms.  These requirements will ensure that product releases from the most vulnerable portion of the UST systems are minimized.  (Today's preamble section IV.D.3.b. discusses these requirements more fully.)

C.	Alternative Approaches Considered

1.   New UST Systems Containing Petroleum

	In the preamble to the proposed rule (52 FR 12673-12675), EPA described three basic regulatory options that were considered for new petroleum tanks: (1) protected single-walled tanks with release detection; (2) secondary containment with interstitial monitoring; and (3) a class approach under which more protective requirements would apply to UST systems located where a release could pose a particularly high risk.  The Agency solicited comments on each of these general approaches to regulate new petroleum tanks, and announced that, based on comments received and on any additional data gathered prior to promulgation, it would give further consideration to each of them before finalizing today's rules.  Numerous comments were received concerning these options, and EPA developed additional information after the proposal that is relevant to this issue.  (EPA solicited comment on this new information in the December 23, 1987, Supplemental Notice and in the March 31, 1988, Notice of Availability.)

	Based on EPA's information and on public comment, the Agency has decided to proceed with the proposed approach of protected single-walled tanks with release detection for new petroleum UST systems.  The Agency's basic rationale for this choice as explained in the preamble of the proposal remains unchanged.  The following discussion briefly highlights some of the concerns raised by commenters and the influences that the new information had on this final decision.

a.	Option 1:  Protected Single-Walled Tanks With Release Detection

	Several commenters supported EPA's proposed approach of allowing protected single-walled tanks with release detection to be used at all new petroleum UST systems.  They agreed that this approach is protective of human health and the environment, confirmed that it is already widely in use by industry and in numerous state programs, and that it is available as a viable and effective alternative to interstitial monitoring.

	Some commenters, however, suggested that the approach of protected single-walled UST system with leak detection approach is not as implementable as secondary containment.  They stated that secondary containment is a more straightforward technical approach because, in the long run, it simplifies implementation by allowing relatively easy determination of the UST's compliance status.  Another disagreement with this option is the belief expressed by some commenters that the probability of releases to the environment occurring at single-walled tanks with release detection is much greater compared to UST systems with secondary containment and interstitial monitoring.

	EPA agrees with those commenters who suggested that there will probably be more releases to the environment from protected single-walled UST systems with release detection than from systems equipped with interstitial monitoring.  One of the advantages of secondary containment is the potential for detecting a leak before a release to the environment actually occurs.  Secondary containment thus provides a second barrier against release.

	Although there are several reasons why EPA has not mandated secondary containment with interstitial monitoring at new petroleum UST systems, the most important reason is that it is not believed to be necessary to protect human health and the environment at such systems (in contrast to hazardous substance UST systems, discussed in section III.C.3. below).  The new causes of release information (discussed previously in today's preamble) shows that the use of new, protected, single-walled USTs has, so far, resulted in the virtual disappearance of failures, because these new USTs have preventive controls for the main cause of past tank failures: corrosion of unprotected, bare steel.  This new information also revealed that protected UST piping that is carefully installed and immediately tested is expected to significantly reduce the occurrence of release incidents from this other major component of the UST system (a reduction of at least two-thirds according to experienced installer estimates).  Piping failures will not, however, be prevented to the same degree as tank failures.

	Thus, the Agency has concluded that petroleum releases will be dramatically reduced using protected UST systems.  This fact must also be considered with the knowledge that numerous effective methods of release detection are available and are being used at petroleum UST systems nationwide.  These methods of detection will enable actions to be taken that will minimize the extent of the few releases that do occur.  Also, the nature of petroleum products and the widely available technologies for their clean up provides the means to ensure that adverse impacts from such releases (when they occur) can be managed and remediated.

	In consideration of all of the above factors, the Agency has concluded that single-walled protected UST systems combined with the release detection required today will adequately protect human health and the environment.  {NOTE:  As discussed earlier in this section of the preamble, today's final approach to new petroleum UST systems has been further tailored to allow infrequent tightness testing of protected or upgraded tanks (combined with inventory control) for the first 10 years of their operating life, with more release monitoring required of the UST system piping--including continuous monitoring of pressurized lines.}

b.  Option 2: Secondary Containment With Interstitial Monitoring

	Several commenters supported the use of secondary containment with interstitial monitoring for various reasons, including: product releases would be completely contained and prevented from adversely impacting the environment and public health; it is a more rapid and reliable form of release detection; the cost is comparable to single-walled UST systems with release detection; and the need for conducting site assessments and corrective action would be avoided.  Others, however, opposed its required use with new petroleum tanks for reasons such as: the greater capital and installation costs do not justify the environmental gains that would be achieved (in comparison to the single-walled approach); and this approach is not compatible with current trends in industry that are well underway in upgrading existing UST systems.

	As previously stated, EPA agrees that secondary containment with interstitial monitoring would most likely result in fewer releases to the environment compared to protected single-walled UST systems with release detection.  UST systems having secondary containment and interstitial monitoring are not perfect, however, and failures of these systems will also occur and result in some releases into the environment that will have to be remediated.  Although protected single-walled systems would result in more releases, the Agency has concluded that this increase is not a significant added threat to human health and the environment given that release detection will minimize the extent of these additional releases, and the availability of petroleum cleanup technologies is widespread and capable of alleviating any resultant adverse impacts.  In addition, the Agency is concerned that many owners and operators would delay upgrading their existing petroleum UST systems to the extent allowed by law or even to the point of noncompliance, because of the perception on the part of many commenters of the significance of higher capital and installation costs that would result from requiring secondary containment and interstitial monitoring (compared to protected single-walled USTs with release monitoring).

c.  Option 3:  Classification Approach

	EPA recognized from the outset that releases from petroleum UST systems located in certain sensitive areas pose a greater risk of harming human health and the environment than others.  As a consequence, one of the regulatory options the Agency considered extensively in developing the final rule was a federal classification approach based upon the potential impact of a release.  Under this approach, a class or classes of UST systems located in high-risk areas would be subject to more protective requirements than UST systems located in less sensitive areas.

	Although the proposed baseline standards for prevention and detection of releases made no differentiation based on class, the Agency requested comment in the April 17 proposal on the general desirability and feasibility of a classification approach to regulating UST systems.  EPA also sought comment on a specific, two-tiered classification scheme.  Under this scheme, owners and operators of UST systems located in high-risk areas, defined as the area within a specified distance of a public drinking-water well, would be required to use secondary containment.  The baseline standard of protected, single-walled tanks with release detection would be allowed in low-risk areas.

	EPA received several comments that favored or opposed inclusion of a federal classification approach in the final rule.  Several commenters in favor of a class approach suggested, and the Agency has considered since proposal, alternative regulatory schemes with respect to how requirements should differ among UST systems in different classes.  The schemes examined included accelerating the schedule for upgrading of existing UST systems to new tank standards or for compliance of existing UST systems with release detection requirements in high-risk areas; imposing more stringent design requirements (e.g., secondary containment) in high-risk areas; and imposing more stringent design requirements in all areas except those designated as low risk by the implementing agency.  The Agency also explored several potential criteria proposed by commenters for differentiating among classes.  Hydrogeologic criteria, such as proximity to ground water used for drinking water, were considered most extensively.  The criterion EPA selected for detailed analysis was distance to a public water well.  (For discussion of the results of the analysis see the Regulatory Impact Analysis for the Technical Regulations.)

	As pointed out by several commenters, the concept of a classification approach to regulating UST systems is appealing for many reasons.  Because the potential impact of a release is greater in more sensitive areas, a classification approach tailors the level of protection to the risk posed in a particular area.  EPA's analyses of various classification schemes indicated that, without considering the costs of implementation, the benefits of a classification approach, primarily in terms of corrective action costs avoided, could be significant.  Cleanup of contamination is especially difficult and expensive in sensitive areas, such as where ground water used for drinking water is affected.  Classification could also provide a priority-setting scheme for enforcement and corrective action.

	Despite the advantages, EPA has not included a classification approach in the final rule.  Commenters' arguments against a federal classification approach influenced the Agency's decision.  EPA agrees with commenters that the baseline requirements set by the final rule will adequately protect the environment in all areas while also encouraging timely voluntary compliance by avoiding unnecessary additional complexity and providing reasonable flexibility for UST system owners and operators.  Although EPA supports the concept of differential protection based on the potential impact of a release, the Agency believes that, for this program, classification at the federal level is neither feasible nor practical.  EPA is particularly concerned about the potential hindrance to state program approval and the difficulties of implementing a classification approach at the federal level.

	Due to the size and nature of the community to be regulated, the success of this program depends largely upon implementation at the state and local levels.  Most states, however, have not developed classification systems.  Development of appropriate and workable classification schemes could take significant time and resources given the number of environmental and other factors that must be considered.  The Agency is concerned that the steps necessary to define criteria and then identify high-risk and low-risk areas in states that have not yet done so could delay implementation of the program and divert scarce resources from efforts to achieve the improvements of the baseline UST regulatory requirements, which will provide most of the benefits.  This additional complication may discourage states from seeking approval altogether.  The Agency has concluded that the potential reluctance of states to implement this program as a consequence of requiring a classification approach could result in less successful protection of the environment and human health.

	In addition, even without implementation delays, a federal classification scheme is not likely to provide significant real additional protection.  Several commenters stated (and the Agency has concluded) that, at the federal level, any criteria used to classify would have to be simple (such as specified distance to a water well) because implementation of a classification scheme based on more complex criteria would not be feasible.  Yet, given the diverse hydrogeologic conditions that exist in the United States, no single, simple classification criterion would be appropriate everywhere.  For example, a distance to drinking-water well criterion, as presented in the preamble to the proposal, is meaningless in locations such as Phoenix, Arizona, where the depth to ground water is so great that releases from UST systems will rarely contaminate drinking-water wells; or in places like Dade County, Florida, where ground water may move so fast that a release could travel the standard distance within a short period of time.  Because defining and identifying high-risk areas is so highly dependent on local (site-specific) hydrogeologic and other factors, EPA believes that state and local implementing agencies can make the most meaningful determinations of classes.

	Although the Agency has concluded that a classification approach at the federal level is neither feasible nor desirable, EPA believes that a classification approach to regulating UST systems at the state or local levels, where local environmental conditions are better known, may be both feasible and appropriate.  Under today's approach, the Agency allows but does not require states to use a classification approach if it is appropriate for the conditions in the state.  For example, states that have already developed a classification scheme may decide to use it to regulate USTs.  For such states, the potential difficulties associated with implementing a classification approach to regulating UST systems may be significantly reduced.

2.     Existing UST Systems Containing Petroleum

a.	Mandatory Upgrading or Replacement of Substandard UST Systems

	In the preamble to the proposal, the Agency identified four regulatory approaches to scheduling the upgrade or replacement of substandard existing UST systems:  (1) rapid upgrade or replacement (within 3 to 5 years of final rule promulgation), (2) gradual upgrade or replacement (within 6 to 12 years of final rule promulgation), (3) no required upgrade or replacement, and (4) scheduling of upgrade/replacement based on a class approach (upgrade or replace tanks located in environmentally vulnerable areas first).  EPA proposed to implement scheduling of mandatory upgrade/replacement using the gradual approach (within 10 years after the effective date of the final rule) and has retained this requirement in today's final rule.

	Many commenters supported the proposed 10-year compliance period for the reasons identified in the preamble to the proposal (52 FR 12676).  However, some recommended a shorter time period, stating their belief that industry resources could meet the demand and that a faster upgrading schedule would prevent a significant number of future product releases.  In contrast, other commenters suggested a longer compliance period than proposed and argued that more time was needed to become familiar with the UST regulations, that owners of multiple tank systems would not be able to finance upgrades/replacements in 10 years or less, and that the service industry would need more time to implement upgrades for this large universe of existing tank systems.

	As stated in the proposal, the Agency agrees that if upgrading could be completed in the shorter compliance period (3 to 5 years) it would decrease the number of product releases and thereby provide greater protection of human health and the environment.  However, the Agency also agrees with those commenters who believe that the large number of existing UST systems essentially precludes industry from implementing upgrade requirements faster than the proposed 10-year period.  Furthermore, EPA is in agreement with many of these same industry commenters who indicated that a 10-year compliance period is a reasonable time period and would not be overly burdensome.  EPA is aware of numerous industry upgrading programs that have already started and will be completed within this time frame.

	EPA continues to believe that the alternative of not requiring upgrade/replacement of substandard systems is simply unacceptable because the Agency has concluded that UST owners probably would not upgrade if it is not required.  The universe of 1.4 to 2 million UST systems largely consists of unprotected, bare steel tanks.  The new causes of release information summarized previously in this preamble (and derived from the "Causes of Release from UST Systems" report) confirms that the unprotected segment of the UST universe is very likely to leak due to corrosion and piping failures and, therefore, presents a significant threat to the public health and environment.  Historical tank replacement rates, established trends in the closure of existing retail motor fuel businesses over time, and the imposition of this new regulatory program are expected together to result in rapid decrease in these substandard UST systems nationwide.  However, a totally voluntary program of UST system upgrading is not expected by EPA to result in the timely upgrade or replacement of UST systems on a nationwide basis, particularly given the large number and heterogeneous nature of this universe of existing UST systems.  In order to ensure human health and the environment are protected, the Agency has established a clear national goal of upgrading all substandard UST systems within 10 years that rejects a purely voluntary approach as inadequate.  This goal is intended to prompt all UST owners and operators to plan for and undertake the upgrading steps that are needed to protect human health and the environment.

	Another option considered by the Agency in development of the proposal was to further require upgrade and replacement based on the use of a class approach that scheduled more rapid UST system upgrades/replacements in the most vulnerable areas (e.g., ecologically sensitive sites or sites in close proximity to drinking water sources) while allowing other UST systems to be phased in on a more gradual basis.  Many commenters recommended staggering the implementation schedule for upgrade/replacement based on other factors (besides class) such as tank age, tank size and type, proximity to human populations, and the measured corrosivity of a site.  The common concern among these commenters was that a staggered schedule would prevent all owners from being allowed to wait until the last minute to bring their existing substandard tank systems into compliance and would, thereby, ensure a more even, implementable, and serviceable demand for tank upgrade/replacement over the 10-year period.

	The Agency has decided not to require the phase-in of upgrading based on the class approach strategy, or on the basis of any other factor, for several reasons.  Although many factors on which to base tank upgrade/replacement have been identified, because of the serious ramifications to the owner and operator associated with the technical requirements for upgrading, EPA believes no single risk-based factor is appropriate or applicable to mandate nationwide for all existing UST systems.  Today's general 10-year requirement in the final rule also allows implementing agencies in approved states, or under State law, the opportunity to decide the staggered schedule on which upgrades should be conducted and what factor(s) are most applicable to their tank population.  Regardless of what type of state action is taken, upgrading is already rapidly taking place through numerous industry programs.  Today's final approach allows them to continue to use the numerous different phase-in approaches that are already successfully underway.  EPA believes this flexibility should also encourage others to upgrade because they can set their own schedules to meet the 10-year deadline.  Thus, EPA has concluded that much of this regulated community will have completed these voluntary programs of closure and upgrading within the mandated 10-year period, and, therefore, the number of existing USTs that otherwise will have to be upgraded by the end of this upgrading period is expected to be relatively small.  The implementation of today's final requirements for release detection (and the financial responsibility requirements to be provided later) are also expected to prompt rapid upgrading and should work to ensure that the implementation difficulties at the end of the 10-year period that were cited by some commenters are not encountered due to a backlog of upgrading demand.

	In summary, EPA believes that the 10-year upgrade requirement will not present an undue burden on industry and is implementable, but is needed to prompt a significant portion of this regulated community into making the upgrades and improvements necessary to protect human health and the environment.  It will also provide industry and the states with some flexibility that will allow (and thereby encourage) them to determine their own approaches and schedules for ensuring tank upgrade/replacement programs are implemented expeditiously within the nationally mandated timeframe.

b.	Methods of Release Detection

	The majority of existing UST systems are not currently being monitored for releases to the environment.  Therefore, EPA continues to believe that a fundamental goal of today's regulatory approach must include the establishment of reliable release detection at all UST systems.  In the proposal (52 FR 12676), the Agency required all existing substandard UST systems to comply with one of the six release detection methods proposed for new USTs (52 FR 12713).  The dual objective of this proposed approach was to allow for the continued development of release detection technologies and also to ensure that only sound and reliable release detection methods were used.  Particularly for petroleum UST systems, the Agency believed many releases would be detected if an appropriate method was selected and properly used.

	In the preamble to the proposal (52 FR 12676), EPA identified that a wide variety of release detection methods (applied either internally or externally to the tank) were currently on the market but with limited data available concerning their performance.  This lack of performance data and field experience was corroborated by many commenters.  Although numerous comments were received regarding the release detection methods proposed (see section IV.D. of today's preamble for a summary and discussion of these comments), the Agency did not receive any comments that opposed the general approach of mandating the use of at least one of the allowed methods at existing UST systems.  Other commenters noted their successful use of different types of methods.

	Performance data obtained from commenters and from EPA-sponsored research since proposal support the Agency's decision to retain the proposed approach in the final rule.  (EPA solicited public comment concerning this new information on March 31, 1988; 52 FR 10403.)  The Agency is convinced that the proposed release detection methods, when properly applied and performed as specified in the final rule, will successfully detect the large number of leaks believed to already have occurred.  For example, over the past year in California and Florida, several thousand UST system releases have been identified using these methods of release detection, and there appear to be few instances where releases have been later discovered through other means (e.g., off-site impacts) when release detection was being properly conducted at a site.

3.   Hazardous Substance UST Systems

	UST systems containing hazardous substances were proposed to have secondary containment with interstitial monitoring unless the owner or operator obtained a variance by demonstrating that another release detection method would be effective in detecting releases of that substance from a single-walled UST (see 52 FR 12677, April 17, 1987).  The reasons for selecting this proposed approach were:  (1) information is not available on the applicability and demonstrated reliability of release detection methods at most hazardous substance USTs, and (2) few industry and state and local agency UST programs yet apply to hazardous substance USTs and, thus, there is little collective experience on management of such USTs.  The Agency recognized that some release detection methods for petroleum UST systems might also perform well at some hazardous substance USTs.  Hazardous substance USTs, however, store an array of individual chemical compounds that vary widely in their physical and chemical characteristics and that may not be readily or reliably detected using release detection methods developed for single-walled UST systems storing petroleum products.  They also may not be able to be as readily addressed by corrective action technologies that are already widely available for petroleum releases.  Therefore, the proposed approach required secondary containment at all new hazardous substance UST systems, unless owners and operators could demonstrate that an alternative release detection method could be reliably applied and operated.

	Several commenters were opposed to the proposed secondary containment approach at new hazardous substances UST systems because:  (1) they do not believe that chemicals designated as hazardous substances are any more hazardous than petroleum products (and, therefore, should not have to meet more stringent requirements), and (2) EPA has not provided a technically valid explanation of why single-walled USTs are appropriate for petroleum products but not for hazardous substances.  It was also suggested that, instead of having a lengthy and costly variance procedure on a case-by-case basis, the Agency should incorporate a variance in the final rule for certain classes of hazardous substances.

	The Agency has decided to retain secondary containment for all new hazardous substance USTs in today's final rule because EPA has not received any additional information or data since proposal to convince the Agency that reliable and appropriate release detection methods are generally available for hazardous substance USTs.  The Agency continues to believe that under certain conditions, hazardous substances will pose a greater risk to human health or the environment than petroleum products.  Furthermore, there are proven, reliable and available release detection methods and cleanup technologies for petroleum, whereas the applications of these same release detection methods and cleanup technologies are neither proven nor available for hazardous substances.

	Also retained in the final rule is the proposed exception for those owners and operators who, by means of a variance, can demonstrate that a release detection method (other than interstitial monitoring) can be successfully installed and operated at a specific hazardous substance UST system to detect releases of the stored substance.  An additional requirement in the final rule is that an owner and operator must also demonstrate that a corrective action method is available to clean up the release.  The Agency decided not to structure the variance procedure by classes of hazardous substances because physical properties of chemicals within a class can be quite variable (for example, wide ranges in solubility and volatility) and require different corrective action approaches, and one release detection method would not reliably detect all of the chemicals within that class.  (A more detailed discussion on the final rule regarding hazardous substance USTs is presented in section IV.D. of today's preamble.)

	A detailed discussion of the methods of release detection allowed for existing petroleum UST systems is also presented in section IV.D. of today's preamble.

4.   Corrective Action

	An important facet of today's final strategy for regulating underground storage tanks is to ensure that public and private drinking water supplies are protected, and that necessary steps are taken to abate other health and safety threats (such as fires and explosions) due to present and future releases from UST systems.  As described previously in this preamble, tens of thousands of UST systems are believed to have already leaked substantial quantities of regulated substances into the environment and numerous public and private wells have already been threatened or destroyed.  As discussed in the preamble to the proposal (52 FR 12678), the development of a regulatory program for corrective action started with three assumptions: (1) the need to implement the requirements through the extensive participation of state and local UST programs; (2) the approach taken must be able to work as the nature of the UST corrective action problem changes over time; and (3) a process must be set up that ensures owners and operators get quickly to the task of cleaning up all releases, although the completion of corrective action may take a long period of time at any one site.

	The proposal provided for separate but very similar corrective action processes for UST systems that contain petroleum and those that contain hazardous substances.  In the proposal, the Agency solicited comment on whether the proposed requirements should be integrated into one subpart.  The proposal also divided the regulatory requirements for corrective action into two stages:  (1) immediate abatement actions that all owners and operators must take in response to a release; and (2) long-term investigation and remedial action measures that may be taken on a site-specific basis to protect human health and the environment.  The Agency solicited public comment on the approach taken to these immediate abatement (Stage I), and long-term remedial action (Stage II) issues in the proposal.  These and numerous other corrective action issues are discussed in more detail in the following section of this preamble that addresses the section-by-section analysis of the final corrective action rules (see section IV.F.).  The following discussion briefly highlights the major decisions and influences (including public comment) that went into the development of the Agency's final approach to corrective action for UST systems storing regulated substances.

a.   Corrective Action for Regulated Substances

	The proposal provided separate corrective action processes for UST systems storing petroleum and those storing hazardous substances (proposed Subparts F and G).  The stated purposes of this approach were: (1) to avoid confusion over which procedures must be followed at a release site; and (2) to construct an approach towards hazardous substances corrective action that was very similar to the one for petroleum, except that it was intended to move the owners and operators more quickly to collect, array, and assess the information needed to determine the nature, extent, and hazard of the corrective action release (52 FR 12682).  The dividing line between Stage I and Stage II of the process was intended to occur earlier in the response to a hazardous substance release, thus following more closely the RCRA Subtitle C hazardous waste tank approach to corrective action.  This proposed approach was an attempt to provide a response process for hazardous substances that recognized the relatively greater hazards that could be posed by hazardous substances releases, and that ensured that there was consistency with the corrective action approach required for hazardous waste tanks.  EPA solicited comments on whether the petroleum and hazardous substance requirements for corrective action should be merged in the final rule.

	In response to public comments received, and several other revisions made in the final corrective action rules, the Agency has decided to consolidate the requirements for UST corrective action into Subpart F for all regulated substances (both petroleum and hazardous substances) for the reasons discussed below.  All of the comments received by EPA concerning the merging of the two proposed subparts were in favor of it, although they made different suggestions on how to accomplish this consolidation (discussed in more detail later in the section-by-section analysis of this preamble).

	Although the preamble to the proposal described the Agency's intention to foster quicker investigatory and cleanup actions at hazardous substances release sites, as was pointed out by some commenters, the few differences in the actual regulatory language between the two separate subparts was not likely to attain this end.  In fact, most of the requirements within the two proposed subparts were the same.  The most significant differences were that a free product investigation was not a required step for hazardous substance responses, and a more rapid (within 30 days) and detailed reporting of certain information was required by owners and operators with hazardous substance releases (see proposed § 280.74(b)) than for those with petroleum releases.  Prompted by these public comments, additional review of these proposed differences has led the Agency to agree that they do not necessarily lead to faster corrective actions at hazardous substance release sites.  Furthermore, even if this end was achieved somewhat for hazardous substance releases, the Agency does not believe it would protect human health and the environment to move less quickly towards the remedial actions required with petroleum releases.  Thus, in the merger of the two subparts in today's final rules, the Agency has developed a process that ensures the most rapid reporting, investigation, and corrective action at all UST release sites that is believed to be attainable (the details of today's consolidation are discussed in more detail later in section IV.F. of today's preamble).

	Because the requirements of the two proposed subparts were largely the same, EPA also believes that today's merger of them into one consolidated Subpart F for all regulated substances avoids a significant source of potential confusion within the regulated community.  Despite the slight procedural differences between the two subparts, the Agency is now convinced that the work involved in investigating petroleum and hazardous substance releases will be very similar.  Also, given that the similarities in the characteristics of different petroleum products are expected to lead to more rapid and widespread understanding of how to respond routinely to petroleum releases (mostly gasoline), the actual investigation, initial abatement of hazards, and the availability of corrective action technology for petroleum releases may result in more rapid and effective release responses at sites with petroleum releases than those with a hazardous substance release.

	The Agency continues to believe that under certain conditions, hazardous substance releases can pose a greater hazard to human health and the environment than petroleum releases.  However, the consolidated requirements in today's final rules have been designed to allow the implementing agency to cause the owner and operator to move as rapidly as is necessary to identify and control any such additional potential threats.  For example, under the final rules, the identification and recovery of free product now must be considered at both petroleum and hazardous substance release sites.  This required consideration of free product recovery, however, does not hinder the progress of corrective action at sites with releases of hazardous substances because the presence and recovery of free product is already something that must be commonly considered at all release sites (whether petroleum or hazardous substances).  The final rule allows enough flexibility to ensure that this type of action is tailored, under the direction of the implementing agency, to site conditions and the type of substance released.

b.   Stage I: Investigation of Releases and Immediate Corrective Action

	EPA proposed requirements for the first stage of the corrective action process (Stage I) by establishing immediate steps that must be taken to abate imminent health and safety hazards whenever a release is confirmed.  The basic approach assured that the following activities were undertaken by the owner and operator at all sites with a confirmed release: (1) immediate notification of the implementing agency; (2) actions needed to stop further releases; (3) mitigation of safety hazards due to fire and explosion; (4) removal of contaminated soils; (5) investigation of the existence and extent of floating free product; and (6) initiation of the removal of free product and submittal of free product recovery plan unless directed to do otherwise by the implementing agency.

	Numerous public comments on issues related to these proposed requirements are discussed in more detail later in this preamble.  In general, many commenters believed the proposal was unclear as to what exactly had to be done, and by whom, to comply with the requirements.  EPA, in response to these commenters, has revised the language in the final rule to clarify which elements of the initial response actions are mandatory and which are discretionary.  The mandatory requirements are intended to ensure three goals are accomplished:

	oTo bring leaking UST sites under control with respect to immediate health and safety hazards;

	oTo stabilize the site so that contamination will not worsen as investigation and potentially long-term remedial actions are considered; and

	oTo be self-implementing in that these measures emphasize the responsibility of the owner and operator to take immediate action without awaiting approval of the implementing agency.

	All sites with releases of regulated substances must investigate the area around the UST system to be able to characterize the size and nature of the release (e.g., a small spill or a large, continuing slow release).  The findings of this initial investigation must be reported to the implementing agency, which has the discretion to require a more extensive site character - iza - tion based on these initial findings.  The proposal has also been revised to make this more extensive examination of ground-water and soil contamination mandatory when the initial investigation reveals that a significant release has occurred (e.g., free product floating on the ground water or saturated soils in the subsurface), even in the absence of direction from the implementing agency.  Thus, today's final rule requires all releases that seriously threaten or impact ground water to be automatically investigated by the owner and operator to characterize the extent of ground-water con - tam - ina - tion and any soil contamination remaining at the site.

c.   Stage II: Long-Term Corrective Action Options

	EPA also proposed requirements for the second stage of the corrective action process (Stage II) addressing long-term remediation of contaminated soils and ground water.  The Agency solicited public comment on three regulatory options for establishing long-term cleanup requirements: (1) national cleanup standards, with a variance provision; (2) site-specific standards to match the risk presented; and (3) a predetermined class approach.  The proposal emphasized the second approach, with its site-specific cleanup targets based on (1) the data from the detailed site investigation of soil and ground-water contamination performed by the owner and operator and (2) the site-specific risk present as determined by the implementing agency using exposure and risk assessment techniques.

	EPA received public comments for and against each of the three options for establishing cleanup levels.  The majority of commenters preferred the proposed site-specific approach as the best way to accommodate the diversity of UST releases nationwide.  Those in favor of establishing national cleanup standards in the regulations expressed the opinion that this would expedite cleanups and provide greater national consistency in cleanup results.  Supporters of the class approach cited the wisdom of tailoring cleanup efforts to a predetermined assessment of risk based on prospective classifications tied to ground-water vulnerability.  EPA has decided to retain the site-specific approach in the final rules.

	For the same reasons that were cited in the preamble to the proposal (52 FR 12680-12682) and supported by most commenters, EPA continues to believe that the site-specific approach is the most appropriate because it allows implementing agencies the necessary flexibility to address corrective action based on the unique circumstances of the site.  It also enables state and local governments to build upon their own experiences when assessing the need for and extent of corrective action.  EPA is not convinced that a national standards approach will result in more rapid and consistent levels of corrective action.  No data were provided that demonstrate this position.  In fact, the information available to the Agency about UST cleanup technologies indicates that the level of actual cleanup achieved is much more dependent on the limitations associated with current corrective action equipment and the problems posed by individual site conditions, than it is on the cleanup levels established in a corrective action plan (or by regulation).  In selecting the site-specific approach, the Agency notes that it does not preclude the use of the other two approaches by implementing agencies.  Some states already are using a statewide standards approach.

	The Agency continues to believe that the site-specific risk assessment process can be streamlined to ensure that the corrective action needed at a site can be identified rapidly and initiated quickly.  EPA maintains the position expressed in the proposal's preamble (52 FR 12681) that site-specific cleanup levels will have to account for potential exposure of the public to contamination at the site.  If a drinking water supply, public or private, is affected or threatened by the release, then the cleanup levels in the corrective action plan should be established using health-based levels as the target for cleanup of the release, unless an alternative source of drinking water can be provided to the potentially affected public.  The Agency is developing further guidance concerning the use of risk assessment and exposure assessment techniques for releases at UST sites.  These efforts are expected to further streamline the site-specific approach to regulation promulgated today.  (Further discussions of the site-specific approach to standard setting and corrective action plans are provided later in the section-by-section analysis in section IV.F. of today's preamble.)

IV.	ANALYSIS OF TODAY'S RULE

A.	Program Scope

1. Applicability

	As described previously, this rule generally applies to all owners and operators of UST systems containing regulated substances.  Regulated substances consist of either petroleum or any substance defined in section 101(14) of CERCLA (but not including any substance regulated as a hazardous waste under Subtitle C).  The following sections discuss the tank systems subject to exclusions from today's requirements and the deferral of regulation for other UST systems.

  2.   Regulatory Exclusions

	The regulatory exclusions in today's final rule are based on a number of statutory provisions and regulatory considerations.  Section 9003(a) of RCRA requires the Administrator to establish an UST program "as may be necessary to protect human health and the environment."  In addition, Section 9003(b) allows the administrator to consider such factors as tank size and quantity of substances stored when establishing necessary requirements.  The Agency believes that this statutory language allows some flexibility for EPA to concentrate its resources on tanks that pose the greatest potential environmental threat.  Section 9001 defines the universe of the UST program and indicates that EPA should regulate tanks containing an "accumulation" of regulated substances.  Section 9001 also excludes tanks regulated under Subtitle C from the jurisdiction of Subtitle I.  Finally, section 1006 of RCRA generally requires integration of RCRA with the Federal Water Pollution Control Act; the Safe Drinking Water Act; the Marine Protection, Research, and Sanctuaries Act; and the Atomic Energy Act.

	Based on these provisions, the Agency is today excluding from regulation several types of tank systems.  These exclusions will decrease the regulatory burden on implementing agencies so they can focus their resources on types and classes of tanks that pose a significant threat to human health or the environment.  Unlike statutory exclusions, regulatory exclusions may be modified by the Agency in the future should new information show that regulation of such an excluded tank type is necessary.